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  Subjects -> PHYSICS (Total: 775 journals)
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PHYSICS (564 journals)            First | 1 2 3 4 5 6 | Last

Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 7)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin     Hybrid Journal   (Followers: 4)
Nuclear Engineering and Design     Hybrid Journal   (Followers: 12)
Nuclear Medicine and Biology     Hybrid Journal   (Followers: 1)
Nuclear Receptor     Full-text available via subscription   (Followers: 1)
Open Journal of Biophysics     Open Access   (Followers: 1)
Open Journal of Fluid Dynamics     Open Access   (Followers: 3)
Open Journal of Microphysics     Open Access  
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 5)
Optofluidics, Microfluidics and Nanofluidics     Open Access   (Followers: 1)
Organic Electronics     Hybrid Journal   (Followers: 4)
Organic Photonics and Photovoltaics     Open Access   (Followers: 2)
PAJ: A Journal of Performance and Art     Hybrid Journal   (Followers: 12)
Papers in Physics     Open Access  
Particle Physics Insights     Open Access   (Followers: 2)
Particuology     Hybrid Journal  
Pattern Recognition in Physics     Open Access   (Followers: 2)
Pergamon Materials Series     Full-text available via subscription  
Phase Transitions and Critical Phenomena     Full-text available via subscription   (Followers: 1)
Philosophical Magazine     Hybrid Journal   (Followers: 2)
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences     Full-text available via subscription   (Followers: 6)
Philosophy and Foundations of Physics     Full-text available via subscription  
Physica B: Condensed Matter     Hybrid Journal   (Followers: 5)
physica status solidi (a)     Hybrid Journal   (Followers: 1)
physica status solidi (b)     Hybrid Journal   (Followers: 1)
physica status solidi (c)     Hybrid Journal   (Followers: 1)
Physica Status Solidi - Rapid Research Letters     Hybrid Journal   (Followers: 1)
Physical Communication     Hybrid Journal  
Physical Review C     Full-text available via subscription   (Followers: 18)
Physical Review Special Topics - Physics Education Research     Open Access   (Followers: 6)
Physical Review X     Open Access   (Followers: 6)
Physical Sciences Data     Full-text available via subscription   (Followers: 1)
Physics - spotlighting exceptional research     Full-text available via subscription   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 2)
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal   (Followers: 2)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 3)
Physics and Materials Chemistry     Open Access  
Physics Essays     Full-text available via subscription  
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 10)
Physics in Perspective     Hybrid Journal   (Followers: 1)
Physics International     Open Access   (Followers: 2)
Physics Letters A     Hybrid Journal   (Followers: 9)
Physics Letters B     Open Access   (Followers: 3)
Physics of Fluids     Hybrid Journal   (Followers: 24)
Physics of Life Reviews     Hybrid Journal   (Followers: 1)
Physics of Plasmas     Hybrid Journal   (Followers: 6)
Physics of the Dark Universe     Open Access  
Physics of the Solid State     Hybrid Journal   (Followers: 3)
Physics of Wave Phenomena     Hybrid Journal   (Followers: 1)
Physics Procedia     Partially Free   (Followers: 1)
Physics Reports     Full-text available via subscription   (Followers: 2)
Physics Research International     Open Access   (Followers: 1)
Physics Today     Hybrid Journal   (Followers: 34)
Physics World     Full-text available via subscription   (Followers: 3)
Physics-Uspekhi     Full-text available via subscription  
Physik in unserer Zeit     Hybrid Journal  
Physik Journal     Hybrid Journal  
Plasma Physics and Controlled Fusion     Hybrid Journal   (Followers: 3)
Plasma Physics Reports     Hybrid Journal   (Followers: 2)
Pramana     Open Access   (Followers: 9)
Preview     Hybrid Journal  
Proceedings of the National Academy of Sciences     Full-text available via subscription   (Followers: 562)
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (Followers: 3)
Progress in Materials Science     Hybrid Journal   (Followers: 20)
Progress in Planning     Hybrid Journal   (Followers: 1)
Progress of Theoretical and Experimental Physics     Open Access  
Quantum Electronics     Full-text available via subscription   (Followers: 3)
Quantum Measurements and Quantum Metrology     Open Access  
Quantum Studies : Mathematics and Foundations     Hybrid Journal   (Followers: 1)
Quarterly Journal of Mechanics and Applied Mathematics     Hybrid Journal   (Followers: 3)
Radiation Effects and Defects in Solids     Hybrid Journal   (Followers: 1)
Radiation Measurements     Hybrid Journal   (Followers: 2)
Radiation Physics and Chemistry     Hybrid Journal   (Followers: 1)
Radiation Protection Dosimetry     Hybrid Journal   (Followers: 2)
Radiation Research     Full-text available via subscription   (Followers: 3)
Radio Science     Full-text available via subscription   (Followers: 3)
Radiological Physics and Technology     Hybrid Journal   (Followers: 1)
Reflets de la physique     Full-text available via subscription  
Reports on Mathematical Physics     Full-text available via subscription  
Reports on Progress in Physics     Full-text available via subscription   (Followers: 2)
Research & Reviews : Journal of Physics     Full-text available via subscription  
Research in Drama Education     Hybrid Journal   (Followers: 12)
Research Journal of Physics     Open Access  
Results in Physics     Open Access   (Followers: 1)
Reviews in Mathematical Physics     Hybrid Journal  
Reviews of Accelerator Science and Technology     Hybrid Journal  
Reviews of Geophysics     Full-text available via subscription   (Followers: 20)
Reviews of Modern Physics     Full-text available via subscription   (Followers: 17)
Revista Boliviana de Física     Open Access  
Revista Colombiana de Física     Open Access  
Revista Mexicana de Astronomía y Astrofísica     Open Access  
Revista Mexicana de Física     Open Access  
Revista mexicana de física E     Open Access  
Rheologica Acta     Hybrid Journal   (Followers: 3)
Russian Journal of Mathematical Physics     Hybrid Journal  
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 1)
Russian Physics Journal     Hybrid Journal  
Samuel Beckett Today/Aujourd'hui     Full-text available via subscription   (Followers: 2)
Science and Technology of Nuclear Installations     Open Access   (Followers: 1)

  First | 1 2 3 4 5 6 | Last

Journal Cover   physica status solidi (c)
  [SJR: 0.471]   [H-I: 31]   [3 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642
   Published by John Wiley and Sons Homepage  [1608 journals]
  • Impedance spectroscopy study of phase transitions to ionic and superionic
           conductivity states in Ag2S and Ag2Se
    • Authors: O. Alekperov; O. Samedov, R. Paucar, N. Abdulzade, E. Nakhmedov, A. Nadjafov, K. Wakita, N. Mamedov
      Abstract: The percolation threshold (PT) temperatures Tc1,c2 of two non‐equivalent Ag+1,2 ions in Ag2S and Ag2Se lattices were determined from the temperature dependence of low‐frequency (25‐106Hz) impedance spectroscopy measurements. At PT temperatures Tc1≈200 K and Tc2≈ 334 K, an abrupt increase of the dielectric function ε1(ω) of Ag2Se crystal from a very large negative value, ε1 ≈‐109, to a very large positive value ε1≈ 106 was observed, which is assumed to result from the dipole relaxation. The strong peaks of the dielectric losses ε2(ω), tgδ(ω) and impedance Z in Ag2Se were also determined at Tc1,c2. Two significant peaks in ε1(ω), ε2(ω)and tgδ(ω) were observed at Tc1≈ 312‐320 K. and Tc2≈ 380‐430 K in the temperature dependences of these parameters. The measured parameters decreased significantly with increasing frequency, confirming the long relaxation times. The drastic decrease at T > 430 K of ε1from a very large positive value 109to a very large negative one ‐108 is in accordance with infrared (IR) ellipsometry measurements; this indicates that electrons of Ag+‐ ions are ionized because of the high dielectric function screening of lattice sites before the known β→α structural phase transition from monoclinic to a body‐centered cubic (bcc) structure. In addition, the activation energies of Ag+1,2 ions were estimated for Ag2S and Ag2Se crystals. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-24T03:30:08.269573-05:
      DOI: 10.1002/pssc.201400366
       
  • Advancement in treating some features of CIGS thin film solar cells during
           manufacturing
    • Authors: Poonam Sharma; Zhongli Li, Hsueh Hsin Chang, Arya Jagadhamma Letha, Lexi Shao, Yafei Zhang, Huey Liang Hwang
      Abstract: In‐line sputtering and selenization have become the industrial standard, but it is difficult to predict and control the local chemical composition of the film. The present communication reports on the material design, device design and process design. These designs use parameters that are closely related to their chemical compositions, as a variation in composition leads to modification of the Poisson equation, current equation and continuity equation. Therefore, there is a need to build a model that relates the optoelectrical properties and device structural parameters that will be loaded into the process simulation, to obtain the complete set of process control parameters. The detailed optical and electrical properties are also investigated for the development of an analytical solar cell simulator. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-24T03:30:06.90874-05:0
      DOI: 10.1002/pssc.201400315
       
  • Control of extended defects in cast multicrystalline silicon using
           polycrystalline template
    • Authors: Ronit R. Prakash; Karolin Jiptner, Jun Chen, Yoshiji Miyamura, Hirofumi Harada, Takashi Sekiguchi
      Abstract: Extended defects were controlled using polycrystalline silicon as a template for cast‐growth of multicrystalline silicon. At the initial stage of growth, small randomly oriented grains with a high density of random type grain boundaries were obtained. With growth, the grain size increased and the fraction of random grain boundaries decreased. Electrical activity of defects was investigated and it was found that with growth, network of small angle grain boundaries became the most electrically active defects. This network of small angle grain boundaries were found to have a tilt angle less than 3° and were mainly found in elongating grains. The density of these highly electrically active grain boundaries increased with growth. This can be attributed to propagation and agglomeration of dislocations into small angle grain boundaries. The high density of random grain boundaries in this ingot may suppress dislocation propagation between grains, however they do not intersect elongating grains enabling dislocation propagation in elongated grains. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-24T03:30:05.844509-05:
      DOI: 10.1002/pssc.201400299
       
  • Structural characterisation of Cu2.04Zn0.91Sn1.05S2.08Se1.92
    • Authors: G. Gurieva; M. Dimitrievska, S. Zander, A. Pérez‐Rodríguez, V. Izquierdo‐Roca, S. Schorr
      Abstract: Quaternary Cu2ZnSn(S1‐xSex)4 compounds are promising semiconductor materials for absorber layer in thin film solar cells. Record efficiency devices (12.6%) exhibit an off‐stoichiometric composition of the absorber layer. These deviations from stoichiometry cause intrinsic point defects, which determine the electronic properties of the semiconductor significantly. A structural analysis of a nearly C‐type off‐stoichiometric Cu and Sn rich and Zn poor Cu2ZnSn(S1‐xSex)4 mixed crystal with x=0.48 by a neutron diffraction investigation was performed. The average neutron scattering length method was applied, showing that the mixed crystal adopts the kesterite type structure. A detailed cation distribution analysis revealed the occurrence of ZnCu(2a) and SnZn anti‐site point defects additional to the Cu‐Zn disorder in the planes at z=1/4 and 3/4. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:23.574279-05:
      DOI: 10.1002/pssc.201400307
       
  • Optimization of preparation techno‐ logy of ZnO and ZnO: Al thin
           films for solar cell applications
    • Authors: Elnur Bagiyev; Narmina Balayeva, Yegana Aliyeva, Afet Kerimova, Rusif Valiyev, Zamin Mamiyev, Nagi Gasimov, Ayaz Bayramov
      Abstract: ZnO and ZnO: Al thin films of about 100 nm thicknesses were deposited by magnetron sputtering method at 200‐400 °C substrate temperatures under oxygen/argon gas mixture with different O/Ar ratio (0‐6 %O2). The higher crystallinities for ZnO: Al and ZnO films are achieved at 400 °C substrate temperature under 0 % and 4 % (O/Ar) mixture ratios, respectively. The films were characterized by X‐ray diffraction (XRD), spectroscopic ellipsometery (SE), photoluminescence spectroscopy, and atomic force microscopy (AFM) methods. Electrical, optical, and luminescent properties depending on crystallinities of the obtained films were studied. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:22.542009-05:
      DOI: 10.1002/pssc.201400364
       
  • Variable range hopping conductivity at low temperatures in CuGaS2 single
           crystals
    • Authors: N. A. Abdullayev; Kh. V. Aliquliyeva, I. Qasimoglu, T. G. Kerimova, I. A. Mamedova
      Abstract: Charge transport mechanism in the CuGaS2 single crystals in a wide temperature range 4.3‐300 K are investigated. In the high temperature range 100‐300 K, the electrical conductivity is predominantly provided by thermally excited impurity charge carriers in the allowed energy band. The activation energy for impurity charge carriers in this temperature range is equal to 12 meV. In the low temperature range (T < 100 K), the electrical conductivity occurs through charge carrier hopping between localized states lying in a narrow energy band near the Fermi level (so called Mott conductivity). The density of localized states near the Fermi level, the width of the optimum energy band of localized levels, concentration of localized states and the average carrier‐hopping distances are estimated for different temperatures. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:21.491314-05:
      DOI: 10.1002/pssc.201400339
       
  • Metallic conductivity and weak antilocalization in Bi2Te2.7Se0.3 thin
           films
    • Authors: Nadir A. Abdullayev; Afet M. Kerimova, Khayala V. Aliquliyeva, Yong Gu Shim, Kojiro Mimura, Kazuki Wakita, Oktay Z. Alekperov, Nazim T. Mamedov, Vladimir N. Zverev
      Abstract: Submicron thin films of Bi2Te2,7Se0,3 solid solution is synthesized by thermal vacuum evaporation. The films are then subjected to after‐growth vacuum annealing and characterized using X‐ray diffraction and confocal laser microscopy techniques. Electron transport in the synthesized films is studied over the temperature range of 1.4‐300 K at magnetic fields up to 8 T. Electron localization due to electron‐electron interaction, along with weak anti‐localization effect at weak magnetic fields and temperatures below 8 K is observed. The latter effect is commonly encountered in thin films of topological insulators grown by molecular beam epitaxy and has therefore been ascribed to the manifestation of the topological surface states. Finally, phase coherence length is estimated.
      PubDate: 2015-04-22T05:30:20.305072-05:
      DOI: 10.1002/pssc.201400338
       
  • Preparation of europium‐doped GaN and AlGaN films grown by
           radical‐nitrogen‐assisted compound‐source MBE
    • Authors: Shinji Yudate; Yuki Koyama, Sho Shirakata
      Abstract: By the compound‐source molecular beam epitaxy (CS‐MBE), GaN:Eu and AlGaN films grown on both Al2O3(0001) and GaAs(100) substrates were prepared. Under RHEED observation, streak RHEED patterns from GaN were observed. This result shows that the surface of the film grown by CS‐MBE is atomically flat. From the XRD measurements, for GaN:Eu/Al2O3(0001), the film was oriented to c‐axis. On the other hands, for GaN:Eu/GaAs(100), the layer includes both the hexagonal and cubic phases. From the PL measurements, the PL spectra of both GaN:Eu/Al2O3 and GaN:Eu/GaAs(100) showed PL peaks related to Eu3+ ion. For GaN:Eu/GaAs(100), it is possible that part of Eu atom incorporates cubic‐GaN site (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:19.298999-05:
      DOI: 10.1002/pssc.201400330
       
  • Improvement of In2S3/ZnCuInS2 interfaces for wide‐gap solar cells
    • Authors: Teruaki Yamamoto; Takayuki Negami, Koji Matsubara, Shigeru Niki
      Abstract: We have fabricated superstrate In2S3/ZnCuInS2 (Zn2xCu1‐xIn1‐xS2, ZCIS) solar cells as the top cell of multi‐junction solar cells. The ZCIS and In2S3 thin films were deposited by spray pyrolysis deposition (SPD) and an efficiency of 4.4% was achieved with bandgap of 1.8 eV. However, in the structure of superstrate type solar cells, interdiffusion have been caused between the buffer layer and the ZCIS layer. In order to suppress the interdiffusion, we have fabricated In2S3/ZCIS substrate type solar cells. The thickness of the interdiffusion region decreased from 70 nm of the superstrate cell to 15 nm of the substrate cell. As a result, the substrate cell with bandgap of 1.8 eV showed VOC of 0.71 V and FF of 0.55 higher than those of the superstrate cells. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:18.33856-05:0
      DOI: 10.1002/pssc.201400313
       
  • Effects of H2S annealing on Cu‐Sn‐S thin films prepared from
           vacuum‐ evaporated Cu‐Sn precursor
    • Authors: Yuji Miyata; Shigeyuki Nakamura, Yoji Akaki
      Abstract: In this work, Cu‐Sn‐S thin films were prepared from a vacuum‐evaporated Cu‐Sn precursor via annealing in H2S from 200 to 500 °C for 1 h. Cu2SnS3 thin films with monoclinic and tetragonal structures were observed by X‐ray diffraction when the annealing temperature exceeded 325 °C. In addition, the SnS phase was observed when the annealing temperature exceeded 275 °C. The surface of the Cu‐Sn‐S thin film annealed at 500 °C was uneven due to the re‐evaporation of SnS. The absorption coefficient of the Cu‐Sn‐S thin films was above 104 cm‐1 with energies above 1.0 eV. The band gap of these films was estimated from transmission and reflection apectra using UV‐visible‐NIR spectrophotometry to be between 0.88‐1.0 eV when the annealing temperature exceeded 450 °C. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:17.372572-05:
      DOI: 10.1002/pssc.201400310
       
  • Temperature dependence of low‐frequency optical phonons in TlInS2
    • Authors: Raul Paucar; YongGu Shim, Kazuki Wakita, Oktay Alekperov, Nazim Mamedov
      Abstract: The unpolarized Stocks component of the Raman spectra of the layered ternary thallium dichalcogenide, TlInS2 was studied with the aid of a Raman confocal microscope system in the low‐frequency region of 35‐150 cm‐1 over the temperature range that embraced the region of the successive phase transitions in this crystal. The observed spectra were deconvoluted into Lorentzian peaks to single‐out the contribution of each Raman mode. The temperature dependence of the Raman frequency and broadening associated with each mode was then obtained. The irregular temperature behaviour of most modes was disclosed in the proximity of phase transitions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-22T05:30:16.347173-05:
      DOI: 10.1002/pssc.201400350
       
  • RF magnetron sputtering deposition of amorphous Zn–Sn–O thin
           films as a buffer layer for CIS solar cells
    • Authors: Shao‐Wei Chang; Kaoru Ishikawa, Mutsumi Sugiyama
      Abstract: Amorphous Zn–Sn–O (α‐ZTO) layers were deposited by RF magnetron sputtering to provide an alternative n‐type buffer layer for CuInSe2 solar cells. Electrical properties, such as the carrier density, mobility, and resistivity were adjusted by controlling the Sn/(Sn+Zn) ratio of the α‐ZTO layer and by regulating the oxygen partial pressure during sputtering. Valence band discontinuities of α‐ZTO/CuInSe2 were determined using photoelectron yield spectroscopy. The band discontinuity at the interface has “spikes” in the conduction band offset. Further, the short circuit current of a CIGS solar cell that uses an α‐ZTO layer was marginally higher compared to one that used a CdS layer. These results represent a step toward developing a safer, cheaper solar cell with higher performance by using an α‐ZTO film instead of a traditional CdS film. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:30.536287-05:
      DOI: 10.1002/pssc.201400255
       
  • The growth of AgGaTe2 layers on glass substrates with Ag2Te buffer layer
           by closed space sublimation method
    • Authors: Aya Uruno; Ayaka Usui, Yuji Takeda, Tomohiro Inoue, Masakazu Kobayashi
      Abstract: The AgGaTe2 layer growth was performed by the closed space sublimation method on the Mo/glass substrate. The Ag2Te buffer layer was inserted between AgGaTe2 and Mo layers, to improve the quality of grown layers. Crystallographic properties were analyzed by x‐ray diffraction (XRD), and the surface morphologies were analyzed by scanning electron microscopy (SEM). The Ag2Te layer grown on the Mo/glass exhibited a membrane filter structure from the SEM observation. XRD spectra of layers grown with and without the buffer layer were compared. The AgGaTe2 layer with the Ag2Te buffer layer exhibited peaks originating from AgGaTe2, and a very strong diffraction peak of 112 was observed. On the other hand, it was cleared that the layer grown without the buffer layer exhibited no strong peaks associated with AgGaTe2, but Ga‐Te compounds. From this, crystallographic properties of the AgGaTe2 layer were drastically improved by the insertion of the Ag2Te buffer layer. Moreover, the surface morphology exhibited a smooth surface when the Ag2Te buffer layer was inserted. The nucleation site density of AgGaTe2 was probably increased since the membrane filter structure exhibited numbers of kinks at the edge. Chemical reaction between Ga and Mo was also eliminated. It was cleared that the insertion of the buffer layer and its surface morphology were an important parameter to grow high quality AgGaTe2 layers. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:28.403448-05:
      DOI: 10.1002/pssc.201400267
       
  • Study of the synthesis of self‐ assembled tin disulfide
           nanoparticles prepared by a low‐cost process
    • Authors: Arturo Méndez‐López; Arturo Morales‐Acevedo, Yuliana de Jesús Acosta‐Silva, Hironori Katagiri, Yasuhiro Matsumoto, Orlando Zelaya‐Angel, Mauricio Ortega‐López
      Abstract: Oleylamine‐capped tin disulfide nanoparticles were prepared by the hot‐injection method using tin (II) chloride (SnCl2.5H2O) and thioacetamide as tin (II) and sulfur precursors, respectively. The as‐prepared nanoparticles were rinsed with ethanol or toluene, and their structural and morphological were assessed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The obtained nanoparticles were single‐phase SnS2 with hexagonal structure. These nanoparticles self‐assembled to produce spherical 40‐50 nm nanostructures after ethanol evaporation, whilst rhombohedral‐shaped nanostructures or round‐edge nanoribbons were produced after the toluene evaporation. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:26.654532-05:
      DOI: 10.1002/pssc.201400271
       
  • Surface etching of CZTS absorber layer by Br‐related solution
    • Authors: H. Miyazaki; M. Aono, H. Kishimura, H. Katagiri
      Abstract: Cu2ZnSnS4 (CZTS) material has many advantages for high‐efficiency thin‐film solar cell absorber layer. A detailed study of the surface of the CZTS and the hetero‐interface of the CZTS/buffer layer is important to improve the conversion efficiency of CZTS thin film solar cells. We investigated the surface condition of the CZTS films by carrying out the surface treatment using bromine solution. The activation energy of the etching using bromine solution was estimated from the slope of the line fitting the graph of the temperature dependence of the etching rate. The activation energy is about 0.35 eV. This value suggests that etching mechanism of CZTS using bromine solution is diffusion‐limited process. There were no significant changes in the structural characteristics after surface treatment by X‐ray diffraction and Raman spectroscopy. From the results of X‐ray photoelectron spectroscopy measurements, a relative surface composition was shifted to Cu‐ and Zn‐rich phase after surface treatment. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:24.804012-05:
      DOI: 10.1002/pssc.201400274
       
  • Effect of surface treatment of CZTS absorber layer by ammonia solution
    • Authors: H. Miyazaki; M. Aono, H. Kishimura, H. Katagiri
      Abstract: In this work, we investigated the effect of surface treatment of the Cu2ZnSnS4 (CZTS) thin films using ammonia solution. CZTS thin films were prepared by RF sputtering using single CZTS target with sulfurization process. In order to study the effect of surface treatment using ammonia solution, solution temperature was varied. Structural properties of the samples are almost same with and without ammonia surface treatment measured by XRD and Raman spectroscopy. From the measurement of the chemical composition, the Zn is dissolved by ammonia solution. In addition, the removal rate of oxygen and sodium is different between deionised water and ammonia solution. Ammonia could have prevented their removal from the surface to solution. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:22.704809-05:
      DOI: 10.1002/pssc.201400275
       
  • Investigation of the sulfurization process of Cu2SnS3 thin films and
           estimation of band offsets of Cu2SnS3‐related solar cell structure
    • Authors: Soichi Sato; Hiroki Sumi, Guannan Shi, Mutsumi Sugiyama
      Abstract: The morphological and structural transition of Cu2SnS3 (CTS) thin films during sulfurization was investigated. The surface morphology and re‐evaporation of CTS films strongly depend on the sulfurization temperature. Low temperature sulfurization enables the films to be sulfurized and form CTS without re‐evaporation. Subsequently, the high‐temperature annealing improves the grain size of the CTS film. In addition, the energy band diagrams of the CTS‐related solar cell structures that use various n‐ type oxide semiconductors, such as CdS, ZnO:In2O3(IZO), ZnO, SnO2, and ZnO:SnO2(ZTO) were examined by photoelectron yield spectroscopy. The band diagrams of IZO/CTS, ZnO/CTS, SnO2/CTS, and ZTO/CTS have a TYPE‐I heterostructure known as a “spike” conduction band offset structure, essential for high‐efficiency solar cells. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:21.237337-05:
      DOI: 10.1002/pssc.201400294
       
  • Improvement of Cu2ZnSn(S,Se)4 solar cell efficiency by surface treatment
    • Authors: Kento Furuta; Noriyuki Sakai, Takuya Kato, Hiroki Sugimoto, Yasuyoshi Kurokawa, Akira Yamada
      Abstract: Surface treatments for the purpose of contamination elimination and surface passivation were performed to as‐deposited CZTSSe thin films before CdS buffer layer deposition. It was found that HCl etching treatment removes contaminations such as sulfide and oxide on CZTSSe surface and helps enhancement of thiourea treatment carried out after HCl etching. Thiourea treatment drastically improves solar cell characteristics, especially FF and JSC, and it would have the effect of surface passivation, although surface sulfuration does not occur. The improvement of characteristics seems to be due to improvement of the film quality and increase in the width of a depletion layer. As a result, conversion efficiency of CZTSSe solar cells was improved from 6.3% to 10.3% with sequential treatment of HCl etching and thiourea treatment. 10.5% was achieved by air anneal after fabrication with both treatments.
      PubDate: 2015-04-21T05:10:19.329902-05:
      DOI: 10.1002/pssc.201400309
       
  • Optical properties and electronic energy‐band structure of Cu2ZnSnS4
    • Authors: Shunji Ozaki; Keiji Hoshina, Yuji Usami
      Abstract: Optical properties of the quaternary Cu2ZnSnS4 semiconductor have been studied by optical absorption, photoluminescence, photoreflectance, and thermoreflectance measurements. Optical absorption measurements suggest that Cu2ZnSnS4 is a direct‐gap semiconductor having the band gap of ∼1.46 eV at 11 K. The photoreflectance and thermoreflectance spectra reveal distinct structures at energies of the critical points in the Brillouin zone. By performing the band‐structure calculation, these critical points are successfully assigned to specific points in the Brillouin zone. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-21T05:10:17.349331-05:
      DOI: 10.1002/pssc.201400254
       
  • Cover Picture: Phys. Status Solidi C 4–5/2015
    • Abstract: GaN based devices with semipolar quantum wells have seen tremendous advances in recent years. Most have been realized homoepitaxially on pseudo bulk substrates which are typically small and expensive. These restrictions of homoepitaxial growth motivate the research for cost‐efficient and large area alternatives. For polar GaN structures, heteroepitaxial growth on sapphire substrates is well established with excellent results – in contrast to the growth of semipolar GaN layers on sapphire, which presents unique challenges. Drawing from expertise in c‐plane samples, Robert A. R. Leute and coworkers (see pp. 376–380) use selective area epitaxy (SAE) on 2‐inch c‐oriented templates to fabricate 3D structures with semipolar side facets. Stripes with triangular cross‐section aligned parallel to GaN a‐direction exhibit {10–11} facets which can be overgrown with quantum wells. By reducing the size of these structures to a sub‐μm scale, they are able to embed their semipolar QWs within planar layers resulting in flat samples with c‐plane surfaces. Thereby all layers except the QWs are grown c‐oriented. The authors present results concerning semipolar QWs emitting in the blue and green spectral range as well as light emitting diodes. The colorized STEM image shows the position of the embedded semipolar QWs inside the otherwise c‐oriented LED structure. The small figures show the spectra of blue and true‐green LED under cw operation and a photograph taken through a microscope during cw operation (image slightly retouched to remove dirt on the surface).
      PubDate: 2015-04-17T03:21:56.468088-05:
      DOI: 10.1002/pssc.201570079
       
  • Cover Picture: Phys. Status Solidi C 4–5/2015
    • Abstract: View of part of the surface during MBE growth of homoepitaxial wurtzite GaN(0001) showing Ga atoms in yellow and N atoms in red. The terrace atoms are already incorporated into the crystal whereas the adatoms diffuse towards step edges. The rate of diffusion of adatoms is a crucial factor in the quality of the crystal. Through DFT calculations, Manjusha Chugh and Madhav Ranganathan on pp. 408–412 have shown that the hopping barrier for an N adatom is reduced from 1.1 eV to 0.7 eV in the presence of a nearby Ga adatom. This explains why small excess Ga can lead to stable growth in MBE. The authors have carried out kinetic Monte Carlo simulations of this process and show the structures formed.
      PubDate: 2015-04-17T03:21:54.136827-05:
      DOI: 10.1002/pssc.201570080
       
  • Issue Information: Phys. Status Solidi C 4–5/2015
    • PubDate: 2015-04-17T03:21:51.104994-05:
      DOI: 10.1002/pssc.201570081
       
  • Semiconducting asphaltene thin films: preparation and characterization
    • Authors: Ibrahim M. Nassar; Zamin Mamiyev, Khuraman Khalilova, Eldar Mammadov, Yegana Aliyeva, Oktay Alekperov, Ayaz Bayramov, Nazim Mamedov
      Abstract: Asphaltene thin films of 100‐500 nm thicknesses were deposited on soda lime glass substrates from toluene solution by spray pyrolysis method. Atomic force microscopy (AFM), photoluminescence (PL), spectroscopic ellipsometry (SE), and electron paramagnetic resonance (EPR) methods were used for characterization of the films. The obtained films were found to be broad band semiconducting material with band gap energy ∼ 3.1 eV and exhibited n‐type conductivity with resistivity ρ ∼ 8·102Ω·cm. Concentration of free radicals and g‐factor were about of ∼ 1018 spin/g and 2.00307, respec­tively. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:20:10.17852-05:0
      DOI: 10.1002/pssc.201400365
       
  • Phonon‐phonon interaction in CdGa2Se2 single crystals
    • Authors: T. G. Kerimova; N. A. Abdullayev, L. Y. Kengerlinski, I. A. Mamedova, N. I. Ibragimov
      Abstract: Raman scattering spectra of CdGa2Se4 single crystals were measured in temperature range 8‐300 K. From the temperature dependence of optical phonons of B (196 cm‐1) and E (246 cm‐1) symmetry type, the lattice deformation and phonon‐phonon interaction contributions to the temperature coefficient of phonon shift were calculated. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:20:06.305425-05:
      DOI: 10.1002/pssc.201400344
       
  • Cu2ZnSnS4 thin film deposited by pulse laser deposition
    • Authors: Yusuke Watanabe; Hiroki Miura, Yong‐Gu Shim, Kazuki Wakita
      Abstract: In this work, bulk Cu2ZnSnS4 (CZTS) poly‐crystals which were used as a target of the pulse laser deposition (PLD) method were grown using the solid‐phase method. The CZTS poly‐crystals were then investigated using X‐ray diffraction (XRD), Raman spectroscopy, and compositional analyses. It was observed that impure crystal phases were reduced with increasing heat growth duration, and they almost completely disappeared in the crystals grown for 96 h at 980 °C. The lattice constants of the a and c axes were estimated from the XRD data and found to be 5.4307 Å and 10.8680 Å, respectively, which are in good agreement with the standard values of 5.4340 Å and 10.8560 Å, as according to JCPDS Card 01‐075‐4122. Our results indicate that the CZTS poly‐crystals have either a kesterite or a stannite structure. Raman spectra confirmed the existence of CZTS without any secondary phases in the form of binary or ternary sulfides. CZTS poly‐crystals were found to be nearly stoichiometric, and they possessed a uniform composition. CZTS thin films were deposited using the PLD method, and were evaluated using X‐ray diffraction (XRD), composition analysis, and field emission scanning electron microscopy (FE‐SEM). Very few additional impurity phases were detected in CZTS thin films deposited at a pulse energy density of 5 mJ/mm2. Finally, the composition of the CZTS thin films was not consistent with that of the CZTS poly‐crystals as a target of PLD method. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:20:05.325903-05:
      DOI: 10.1002/pssc.201400349
       
  • Impact of water‐rinse treatment on Cu2ZnSnS4 studied by X‐ray
           absorption near‐edge structure analysis
    • Authors: Toshihiko Toyama; Takafumi Konishi, Ryotaro Tsuji, Ryuichiro Maenishi, Akiko Arata, Shinji Yudate, Sho Shirakata
      Abstract: Cu2ZnSnS4 (CZTS) thin‐film solar cells are considered promising for terawatt‐scale production. It has been established that in the fabrication process of CZTS thin‐film solar cells, a water‐rinse treatment for the CZTS surface yields a great improvement in conversion efficiency. We studied the mechanism of the water‐rinse treatment on an aged crystalline‐CZTS sample, using the X‐ray absorption near‐edge structure (XANES) technique, which is highly sensitive for oxidation states of sulfur. The sulfur K‐edge XANES spectra revealed a dramatic change at around 2480 eV after a 3‐min water‐rinse treatment. By comparison with the spectra of reference samples, we posit the removal of surface sulfate cations as a possible source for this behavior. From further comparison with the spectrum of a thin‐film sample, we discuss the use of this short 3‐min treatment time in actual device‐fabrication procedures. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:18.726221-05:
      DOI: 10.1002/pssc.201400265
       
  • Synthesis of SrGa2S4:Eu green emitting phosphor using liquid phase process
    • Authors: Hiroko Kominami; Yoichiro Nakanishi, Kazuhiko Hara
      Abstract: The synthesis process of sulfide phosphors using liquid phase reaction was investigated to aim at fine particle. SrGa2S4:Eu green emitting phosphor was prepared using chlorides and sodium sulfide as source materials. After chemical reaction of acid and alkali, obtained sediments were fired in sulfur atmosphere. The powders were determined at SrGa2S4 single phase by X‐ray diffraction measurement, and the obtained phosphor showed green emission of SrGa2S4:Eu excited by 325 nm of He‐Cd laser and EB excitation. It indicates that it is possibility of new synthesis method for fine‐particle sulfide phosphors. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:15.877114-05:
      DOI: 10.1002/pssc.201400282
       
  • Effects of Zn‐dopant on structural properties and electrochromic
           performance of sol‐gel derived NiO thin films
    • Authors: Russameeruk Noonuruk; Wanichaya Mekprasart1, Wisanu Pecharapa
      Abstract: Zn‐doped NiO thin films were prepared by sol‐gel spin‐coating method onto transparent conducting substrates using nickel acetate tetrahydrate and zinc acetate dehydrate as starting precursors. Effects of zinc doping content on the structural, optical and electrochromic properties of NiO films were investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, field emission‐scanning electron microscope, atomic force microscopy, UV‐VIS spectrophotometer and cyclic voltammetry. The results reveal that Zn doping has significant influence on crystallinity deterioration, surface topography alternation and electrochromic performance of the films. The expansion of active surface area due to reduced crystallinity of the films resulting to the increase of charge transfer in the electrochemical reaction. It is indicated that electrochromic performance of sol‐gel derived NiO films can be ameliorated by the incorporation of Zn additive at specific content. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:14.641078-05:
      DOI: 10.1002/pssc.201400303
       
  • Blue phosphor synthesized with Eu‐containing strontium aluminate by
           reaction on single crystalline magnesia
    • Authors: Keiji Komatsu; Atsushi Nakamura, Ariyuki Kato, Shigeo Ohshio, Hidetoshi Saitoh
      Abstract: The luminescence properties of strontium aluminate (Sr‐Al‐O) phosphors change strongly depending on the starting metal composition ratio of strontium oxide (SrO) and alumina (Al2O3). In this study, the starting metal composition effect on blue Sr‐Al‐O:Eu2+ phosphor synthesized on single crystalline magnesia (MgO) was investigated. The crystal structure and the emission property of the obtained Sr‐Al‐O:Eu2+ blue phosphors, were independent of the Al2O3/SrO ratio in the raw material. In addition, the obtained emission phases were not contained Al atom. These results indicated the correct starting metal composition for the blue phosphor synthesized on MgO is SrO:Eu. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:13.478997-05:
      DOI: 10.1002/pssc.201400304
       
  • Electronic structure of YbNiX3 (X =Si, Ge) studied by hard X‐ray
           photoemission spectroscopy
    • Authors: Hitoshi Sato; Yuki Utsumi, Junichi Kodama, Heisuke Nagata, Marcos A. Avila, Raquel A. Ribeiro, Kazunori Umeo, Toshiro Takabatake, Kojiro Mimura, Satoru Motonami, Hiroaki Anzai, Shigenori Ueda, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi
      Abstract: lectronic structure of the Kondo lattices YbNiX3 (X =Si, Ge) has been investigated by means of hard x‐ray photoemission spectroscopy (HAXPES) with hν = 5.95 keV. From the Yb 3d HAXPES spectra, the Yb valence in YbNiSi3 is estimated to be ∼ 2.92, which is almost temperature‐independent. On the other hand, the valence in YbNiGe3 is estimated to be 2.48 at 300 K, showing significant valence fluctuation, and gradually decreases to 2.41 at 20 K on cooling. The Ni 2p3/2 and Yb3+ 4f peaks exhibit opposite energy shifts amounting to ∼ 0.6 eV between YbNiSi3 and YbNiGe3. We propose a simple model for the electronic structure of YbNiX3 based on the HAXPES results. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:12.315085-05:
      DOI: 10.1002/pssc.201400312
       
  • Preparation and photoluminescence properties of Mn‐doped deep red
           emitting phosphor under blue to near ultraviolet excitations
    • Authors: Shoma Kawakita; Hiroko Kominami, Kazuhiko Hara
      Abstract: Preparation method and photoluminescence properties of Mg2(Ti0.99‐x ‐y, Gex, Siy)O4:Mn phosphor for white LED was studied. The obtained powders showed deep red emission around 670 nm under blue light excitation. The PL intensity depended on the ratio of IV atoms, and PL spectra depended on the IV atom consisted in the phosphors. It was found that the ternary or multinary compounds showed higher luminescence. It indicates that the properties of Mg2(Ti0.99‐x, Gex)O4:Mn might much improve by preparation of completed alloy. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-14T06:10:10.833397-05:
      DOI: 10.1002/pssc.201400323
       
  • Excitonic emission of TlGaSe2
    • Authors: Masashi Hagiwara; Raul Paucar, YongGu Shim, Kazuki Wakita, Oktay Alekperov, Arzu Najafov, Nazim Mamedov
      Abstract: Photoluminescence (PL) spectra in the band‐edge region of bulk single‐crystals of layered ternary chalcogenide TlGaSe2 were examined at low temperature using confocal microscopy. Obvious PL emission near the band‐edge region appeared only when the excitation light travelled in the direction normal to the c axis of the crystal structure of TlGaSe2. The observed PL spectra were resolved into two Gaussian peaks, A and B, located at 2.01 and 2.10 eV, respectively. By analyzing the excitation intensity dependence of the PL intensity, we assigned peak B to proper free excitons, whereas peak A seems to represent free excitons derived from the distorted crystal structure of TlGaSe2. This is the first observation of free excitons in TlGaSe2 by PL measurement. We also examined the temperature dependence of the PL intensity. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:51.068226-05:
      DOI: 10.1002/pssc.201400348
       
  • Numerical analysis of Cu(In,Ga)Se2 solar cells with high defect density
           layer at back side of absorber
    • Authors: Naoki Ashida; Masashi Murata, Daisuke Hironiwa, Jakapan Chantana, Hikaru Uegaki, Takashi Minemoto
      Abstract: The 2‐µm‐thick Cu(In,Ga)Se2 (CIGS) absorber is divided into two areas, low defect density layer (front side) and high defect density layer (back side). In this paper, the optimized thickness of the low defect density layer and the high defect density layer is estimated for high cell performance. The optimization is performed by using device simulator. As a result, the high defect density layer (back side) has no influence on cell performance in the case of CIGS with high optical‐absorption coefficient owing to almost no photocarriers, which are generated in the high defect density layer. In addition, the necessary thickness for absorbing all light to obtain high conversion efficiency is considered. CIGS with graded band profile can be thinner than that with flat band profile for high cell performance owing to the aid of back surface field. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:50.039268-05:
      DOI: 10.1002/pssc.201400242
       
  • Epitaxial growth of chromium nitride thin films with addition of silicon
    • Authors: Kazuma Suzuki; Tsuneo Suzuki, Toshiyuki Endo, Tadachika Nakayama, Hisayuki Suematsu, Koichi Niihara
      Abstract: Epitaxial Cr‐Si‐N thin films were prepared on MgO (100) substrates with a misfit of ‐1.7% with respect to CrN, by pulsed laser deposition. The Si content in the thin films were controlled by varying the ratio of target surface area of Si for Cr. X‐ray diffraction and microstructure observation showed that the thin films were epitaxially grown with the Si contents up to 10 mol% and no grain boundary could be observed. It was considered that the epitaxial thin films consisted of (Cr,Si)N phase, which was synthesized by partial replacement of Cr in CrN lattice with Si. The thin films with the Si contents above 11 mol% formed the polycrystalline. The hardness of the epitaxial Cr‐Si‐N thin films increased with increasing the Si content and the thin films showed the maximum hardness value of 51 GPa. It was considered that the hardening was caused by dissolution of Si in CrN. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:49.071633-05:
      DOI: 10.1002/pssc.201400281
       
  • Morphological and structural modifications of chemically‐prepared
           emeraldine polyaniline and zinc oxide in PAni‐ZnO composite
    • Authors: Reynaldo M. Vequizo; Filchito Renee G. Bagsican, Majvell Kay G. Odarve
      Abstract: In this paper, the characteristic changes on the surface morphology and structure of both emeraldine polyaniline (PAni) and ZnO films in the chemically‐prepared PAni‐ZnO composite are presented. The PAni‐ZnO composite on amorphous glass substrate was fabricated utilizing chemical bath deposition technique. The ZnO films were first synthesized using appropriate amounts of zinc sulphate and ammonium hydroxide. Emeraldine form polyaniline films were then grown on as‐prepared ZnO films using appropriate amounts of aniline hydrochloride and ammonium peroxydisulphate. The formation of zinc hydroxychloride hexagonal‐plate structures in the composite film resulted to morphological and structural modifications of PAni and ZnO composite films. The highly‐crystalline emeraldine polyaniline became amorphous when deposited as part of the composite while increased tensile strain was observed for ZnO in the composite due to stretching‐effect caused by zinc hydroxychloride along the outward‐planar direction. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:47.985294-05:
      DOI: 10.1002/pssc.201400311
       
  • Synthesis and characterization of nanocrystalline hydroxyapatite and
           biphasic calcium phosphate using Ca(OH)2 and (NH4)H2PO4
    • Authors: Romnick Unabia; Joy Cristy Piagola, John Robert Guerrero, Reynaldo Vequizo, Jess Gambe, Majvell Kay Odarve, Bianca Rae Sambo
      Abstract: In this study, nanocrystalline hydroxyapatite and biphasic calcium phosphate prepared via wet chemical precipitation technique in an isolated N2 environment that utilizes calcium hydroxide and ammonium dihydrogenphosphate as main precursors, is presented. Formation of predominantly hydroxyapatite with increasing crystallinity from 39.6 to 88.3% with corresponding crystallite sizes of ∼20.6 and ∼46.6 nm were found for the as‐grown and the annealed powders, respectively. Partly phase transition of hydroxyapatite to β‐TCP phase forming biphasic calcium phosphate was observed in the 900 oC annealed powders. Aggregated structures with nanopores were depicted on the surface of the as‐grown sample while interconnected worm‐like structures with voids forming nanopores were found for the sample annealed at 900 oC. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:46.894894-05:
      DOI: 10.1002/pssc.201400319
       
  • Graphene transparent electrode for thin‐film solar cells
    • Authors: Ryousuke Ishikawa; Yasuyoshi Kurokawa, Shinsuke Miyajima, Makoto Konagai
      Abstract: Transparent electrode is a key component in the multi‐junction solar cells, working as window and intermediate electrodes. It requires high transparency for wide range and suitable electrical junctions. Graphene, a single atomic layer of sp2 graphitic carbon, is one of alternative materials. We demonstrated a‐Si thin film solar cells with high‐quality graphene grown by chemical vapor deposition. The graphene‐cell showed higher open‐circuit voltage compared with conventional transparent conductive oxide. It might be a contribution of lower Schottky barrier at graphene/p‐layer interface. Our experimental results demonstrated a high potential of graphene transparent electrode not only for a‐Si solar cells but also for multi‐junction solar cells.
      PubDate: 2015-04-09T04:43:45.860732-05:
      DOI: 10.1002/pssc.201400320
       
  • Electrical performance of the InGaP solar cell irradiated with low energy
           electron beams
    • Authors: Yasuki Okuno; Shuichi Okuda, Takeo Kojima, Takashi Oka, Shirou Kawakita, Mitsuru Imaizumi, Hiroaki Kusawake
      Abstract: The investigation of the radiation degradation characteristics of InGaP space solar cells is important. In order to understand the mechanism of the degradation by radiation the samples of the InGaP solar cell were irradiated in vacuum and at ambient temperature with electron beams from a Cockcroft‐Walton type accelerator at Osaka Prefecture University. The threshold energies for recoil were obtained by theoretical calculation. The energies and the fluences of the electron beams were from 60 to 400 keV and from 3×1014 to 3×1016 cm‐2, respectively. The light‐current‐voltage measurements were performed. The degradation of Isc caused by the defects related to the phosphorus atoms was observed and the degradation was suppressed by irradiation at an energy higher than the threshold energy for recoiling Indium atoms. At an energy of 60 keV, where the recoil does not occur, the Voc was degraded. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:44.782389-05:
      DOI: 10.1002/pssc.201400322
       
  • Properties of in situ HCl‐doped emeraldine polyaniline on n
           ‐Si(100) substrates for diode application
    • Authors: J. P. B. Ontolan; P. A. M. Alcantara, R. M. Vequizo, M. K. Odarve, B. R. B. Sambo
      Abstract: In this study, the characteristic physicochemical and electrical properties of HCl‐doped polyaniline (PAni) films grown via oxidative chemical polymerization of aniline on n ‐Si(100) are presented. Two exothermic processes were found for 0.2 M HCl solution during aniline polymerization while all others underwent one exothermic process only. All polyaniline films were of emeraldine salt form that exhibited connected rod‐like to agglomerated grains and dendritic surface morphologies on top of wetting layer with increasing hydrochloric acid concentration. Rectifying behaviour of p‐ PAni/n ‐Si(100) heterojunctions were also found indicating the formation of p‐n junction between p ‐PAni and n ‐Si(100). (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:43.715708-05:
      DOI: 10.1002/pssc.201400328
       
  • Band structure and vacancy formation in β‐Ag2S: Ab‐initio
           study
    • Authors: Oktay Alekberov; Zakir Jahangirli, Raul Paucar, Suma Huseynova, Nigar Abdulzade, Anver Nakhmedov, Kazuki Wakita, Nazim Mamedov
      Abstract: Electronic band structure, together with formation energy of native point defects has been studied for β‐Ag2S superionic material. The density‐functional full‐potential calculations have been carried out for perfect crystal and defect structure. In latter case a 96‐atom supercell has been composed and account of structural relaxation around a vacancy has been taken up to second nearest neighbor. Formation energies of point defects have been obtained and compared. According to comparison, cation vacancies are the dominant intrinsic defects in β‐Ag2S and transition into a state with high ionic conductivity is probably related with their abrupt concentration increase with increasing temperature. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:42.671878-05:
      DOI: 10.1002/pssc.201400335
       
  • Crystallographic and optical properties of (Cu, Ag)2ZnSnS4 and (Cu,
           Ag)2ZnSnSe4 solid solutions
    • Authors: Weiyan Gong; Takahiro Tabata, Koji Takei, Masaru Morihama, Tsuyoshi Maeda, Takahiro Wada
      Abstract: (Cu1‐xAgx)2ZnSnS4 (CAZTS) and (Cu1‐xAgx)2ZnSnSe4 (CAZTSe) solid solutions with 0 ≤ x ≤ 1.0 were synthesized. Their crystal structures were analyzed by Rietveld refinement of X‐ray diffraction data. The refined lattice constants a of the kesterite‐type CAZTS and CAZTSe increase with Ag content (x) increasing, while their lattice constants c slightly decrease. Therefore, by increasing x, the c /a ratio decreases from 2 for Cu‐based compounds to a value lower than 1.9 for Ag‐based compounds. The band‐gap energies (Eg) of CAZTS and CAZTSe solid solutions were determined by their diffuse reflectance spectra. The reflectance edges of the CAZTS and CAZTSe shifted to the longer wavelength side with Ag content increasing at 0.0 ≤ x ≤ 0.2, while they shifted to the shorter wavelength side at 0.2 ≤ x ≤ 1.0. By increasing x, the Eg of CAZTS decreases from 1.49 eV (x=0.0) to 1.47 (x=0.2) and then increases to 2.01 eV (x=1.0); and the Eg of CAZTSe decreases from 0.98 eV (x=0.0) to 0.95 (x=0.2) and then increases to 1.34 eV (x=1.0). There is small bowing in the band gaps of the CAZTS and CAZTSe systems. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-09T04:43:41.450258-05:
      DOI: 10.1002/pssc.201400343
       
  • Characterization and effect of calcination temperature on structural
           properties of spinel zinc aluminate synthesized via Co‐precipitation
           process
    • Authors: Wanichaya Mekprasart; Suchada Worasawat, Thanit Tangcharoen, Wisanu Pecharapa
      Abstract: Zinc aluminate (ZnAl2O4) nanopowders were synthesized by co‐precipitation method using zinc chloride and aluminum chloride as starting precursors. The calcination temperature which was a crucial preparation factor was varied and its influence on relevant physical properties of the product was investigated. Structural properties of synthesized nanoparticles were investigated by X‐ray diffraction, X‐ray absorption spectroscopy, scanning electron microscope, and Raman spectroscopy. The results suggest that that ZnAl2O4 in spinel structure with high crystallinity can be obtained after calcination beyond specific temperature affirmed by XRD results. Raman result indicates the correlated chemical bonding relating to the formation of ZnAl2O4 structure. Meanwhile, the Zn K‐edge X‐ray absorption near‐edge structure (XANES) spectra of these samples with different calcination temperature obtained from the synchrotron X‐ray absorption spectroscopy measurement show the existence of accurate oxidation state for zinc ion (Zn2+) in the spinel crystal structure. Moreover, it is revealed that the calcination temperature has significant effect on the local environment of the zinc absorbing atoms through the interesting change of white line appearance. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T12:10:36.314966-05:
      DOI: 10.1002/pssc.201400292
       
  • Depolarization effect in rare‐earth doped Y2O3 films in blue and UV
           spectral range
    • Authors: Naghi Gasimov; Eldar Mammadov, Anne L. Joudrier, Sardar Babayev, Irada Mamedova, Christian Andriamiadamanana, Nazim Mamedov, Negar Naghavi, Jean F. Guillemoles
      Abstract: The 200 to 300 nm thick, Er and Er,Yb doped Y2O3 films deposited onto silicon substrate by spin coating have been studied by spectroscopic ellipsometry over the 192‐1680 nm spectral range at room temperature. All samples have been found to be strongly depolarizing in the blue and UV part of the spectrum. Complimentary examination of the sample surfaces, using confocal photoluminescence microscopy has disclosed the non‐uniform distribution of the rare‐earth dopants. The depolarization effects have then been modeled and found to be best reproduced by taking the thickness non‐uniformity as the main source of depolarization. The optical constants of the studied films have been determined after four‐step modeling with sequential decrease of the mean square error. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T12:10:34.102847-05:
      DOI: 10.1002/pssc.201400301
       
  • Characterization of CuInS2‐Cu2ZnSnS4 crystals grown from the melt
    • Authors: Koichiro Oishi; Kenta Nakamura, Makoto Yamazaki, Shota Fukai, Takuya Shigeno, Hironori Katagiri
      Abstract: Cu2(2.00‐x)((2In)y (ZnSn)(1.00‐y))x S4 crystals were grown from the melt. 23 samples with different x and y values were synthesized by heating constituent elementary Cu, In, S and Zn‐Sn alloy at 1,250 °C for 10 hours in each evacuated fused‐quartz ampule. All samples were characterized by powder X‐ray diffraction analysis. Two peaks are seen at the 112 diffraction positions in 0.3 ≤ y ≤ 0.9. The FWHM of the 112 diffraction peak broadened in 0.2 ≤ y ≤ 0.7. Lattice constants were obtained by Rietveld method using two tetragonal structure models simultaneously in the refinement. Both a and c obtained as CuInS2 phase changed almost linearly in y ≥ 0.7; therefore the existence of CuInS2 phase solid solution containing Zn and Sn was indicated in this region. The miscibility gap was also suggested as the region of 0.2 ≤ y ≤ 0.7 in our results because of the shape and the broadening of the 112 diffraction peaks. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T12:10:32.030877-05:
      DOI: 10.1002/pssc.201400306
       
  • Effect of arsenic cracking on In incorporation into MBE‐grown InGaAs
           layer
    • Authors: Hiromu Iha; Yujiro Hirota, Masatsugu Yamauchi, Nao Yamamoto, Takahiro Maruyama, Shigeya Naritsuka
      Abstract: The effect of arsenic cracking on In incorporation in MBE‐grown InGaAs selective growth was systematically studied with changing the cracking cell temperature. Incorporation of In was greatly enhanced by the use of As2 molecular beam during the selective growth at 600 °C. On the other hand, almost no In was incorporated into the grown layer by the use of a conventional As4 molecular beam. The relation between InAs mole fraction and the cracking cell temperature was found to monotonously increase with the cracking cell temperature. It is probably because the ratio of As2 molecules increases with the cracking cell temperature. Not only at 600 °C but also at 580 °C, a selective growth was also successfully performed using As2 molecular beam by the formation of the “denuded zone”, with the InAs mole fraction of 10%. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:15.94053-05:0
      DOI: 10.1002/pssc.201400286
       
  • A 5.1% efficient kesterite Cu2ZnSnS4 (CZTS) thin film solar cell prepared
           using modified sulfurization process
    • Authors: Myeng G. Gang; Kishor V. Gurav, Seung W. Shin, Chang W. Hong, Jung H. Min, Mahesh P. Suryawanshi, Sharad A. Vanalakar, Dong S. Lee, Jin H. Kim
      Abstract: Cu2ZnSnS4 (CZTS) absorber thin films are prepared by sulfurization of sputtered Cu/Sn/Zn (CZT) stacked metallic precursor. The modified sulfurization process is adapted to prepare photovoltaic quality CZTS films. Specifically, sputtered CZT precursor films are sulfurized in sulfur powder contained graphite box using rapid thermal processing furnace at 580 °C for 10 min, in N2(95%) + H2S (5%) atmosphere. The Cu‐poor CZTS films with various Cu/(Zn+Sn) ratio are prepared by varying Cu layer deposition time. The effect of Cu/(Zn+Sn) ratio on the properties of CZTS films is investigated. The CZTS thin film solar cells with Cu/(Zn+Sn)=0.76 shows best conversion efficiency of 5.1% (Voc: 573 mV, Jsc: 18.38 mA/cm2, FF: 0.48 %, and active area: 0.31 cm2). (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:14.501619-05:
      DOI: 10.1002/pssc.201400285
       
  • Deep absorption band in Cu(In,Ga)Se2 thin films and solar cells observed
           by transparent piezoelectric photothermal spectroscopy
    • Authors: Sho Shirakata; Akiko Atarashi, Masakazu Yagi
      Abstract: The photo‐acoustic spectroscopy (PAS) using a transparent piezoelectric photo‐thermal (Tr‐PPT) method was carried out on Cu(In,Ga)Se2 (CIGS) thin films (both CIGS/Mo/SLG and CdS/CIGS/Mo/SLG) and solar cells (ZnO/CdS/CIGS/Mo/SLG). Using the Tr‐PPT method, the high background absorption in the below gap region observed in both a microphone and a conventional transducer PAS spectra was strongly reduced. This high background absorption came from the CIGS/Mo interface. This result proves that the Tr‐PPT PAS is the surface sensitive method. In the below‐band region, a bell‐shape deep absorption band has been observed at 0.76 eV, in which a full‐width at the half‐maximum value was 70‐120 meV. This deep absorption band was observed for both CdS/CIGS/Mo/SLG and ZnO/CdS/CIGS/Mo/SLG structures. The peak energy of the absorption band was independent of the alloy composition for 0.25≤Ga/III≤0.58. Intensity of the PA signal was negatively correlated to the Na concentration at the CIGS film surface. The origin of the 0.76 eV peak is discussed with relation to native defects such as a Cu‐vacancy‐related defect (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:13.253569-05:
      DOI: 10.1002/pssc.201400284
       
  • The effect of dextrin addition during Cu2ZnSnS4 thin film preparation by
           photochemical deposition
    • Authors: Katsuhiko Moriya; Hikaru Shimotsuma, Kunihiko Tanaka, Hisao Uchiki
      Abstract: Cu2ZnSnS4 (CZTS) thin films were prepared by annealing films of Cu2S, ZnS, and SnS2 precursors deposited on a soda‐lime glass substrate by photochemical deposition (PCD) from an aqueous solution containing CuSO4, ZnSO4, SnSO4, and Na2S2O3. This paper discusses the effect of adding dextrin as a titrant during the PCD preparation of CZTS thin films. We investigated the effects of dextrin addition on the surface morphology of the resulting films. The surfaces of films prepared with added dextrin were composed of uniformly sized grains. The results also demonstrate that the surface morphology of photochemically deposited CZTS films can be smooth if the proper additives are employed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:12.205831-05:
      DOI: 10.1002/pssc.201400280
       
  • Effects of preferential etching treatment of CZTS absorber layer by
           deionized water
    • Authors: H. Miyazaki; M. Aono, H. Kishimura, H. Katagiri
      Abstract: Cu2ZnSnS4 (CZTS) is one of the promising materials for high efficiency thin film solar cells. Here we report on the chemical and structural characterization of the CZTS thin films before and after the surface treatment using deionized water. X‐ray diffraction and Raman scattering spectroscopy results showed that the deionized water treatment did not affect the bulk characterization. Copper chemical composition ratio increases and sulphur composition ratio decreases with increasing deionized water treatment temperature on the film surface. In the case of the sample treated at 353 K, the surface composition changes to Cu‐rich composition. However, the chemical composition ratio of the bulk still remained before deionized water (DIW) surface treatment. The change in the CZTS surface composition according to the DIW surface treatment temperature, we think these results may help to be studied in CZTS surface in more detail. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:11.043396-05:
      DOI: 10.1002/pssc.201400276
       
  • Fundamentals and R&D status of III‐V compound solar cells and
           materials
    • Authors: Masafumi Yamaguchi
      Abstract: The III‐V compound multi‐junction solar cells have high efficiency potential of more than 50% due to wide photo response, while limiting efficiencies of single‐junction solar cells are 31‐32%. In order to realize high efficiency III‐V compound multi‐junction (MJ) solar cells, understanding and controlling imperfections (defects) are very important. This paper reviews fundamentals for major losses of III‐V compound materials and solar cells, key issues for super high‐efficiency MJ solar cells and recent R&D status of III‐V compound MJ solar cells. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:09.97663-05:0
      DOI: 10.1002/pssc.201400216
       
  • EPR and SPM studies of Zn‐Ni ferrites
    • Authors: Sh. N. Aliyeva; Y. N. Aliyeva, A. I. Nadjafov, I. S. Hasanov, E. K. Huseynov, T. R. Mehdiyev
      Abstract: Electron paramagnetic resonance studies have been carried out over 3.7‐300 K on micropowders of Ni1‐xZnxFe2O4 ferrites, obtained by high temperature synthesis and preliminary characterized by X‐ray diffraction and differential scanning calorimetry in a wide range of tempera‐tures. Complimentary, scanning probe microscopy, compris‐ing atomic and magnetic force microscopies has been applied to polycrystalline Ni1‐xZnxFe2O4thin films. The correlation between X‐ray and differential scanning calorimetry data has been observed. Deconvolution of the obtained paramagnetic resonance spectra into Gaussian components and their further analysis have allowed retrival of the compensation points of the magnetc momenta of the sublattices of Ni1‐xZnxFe2O4, as well as of superparamagnetism effect and g‐factors dispersion verified by studies on polycrystalline thin films. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-07T11:51:08.151943-05:
      DOI: 10.1002/pssc.201400273
       
  • Excitonic emission on CuInS2 epitaxial films by pulse laser deposition
    • Authors: Ryo Yoshida; Tseng Po‐Han, Yong‐Gu Shim, Kazuki Wakita
      Abstract: Thin films of epitaxial CuInS2 were deposited on a GaAs substrate at a temperature of 500 ºC by the pulse‐laser‐deposition method. Surface and cross‐section scanning electron microscopy (SEM) images were taken for all the films, with thicknesses estimated to range between 0.5‐1 μm. X‐ray diffraction (XRD) and Raman scattering confirmed the chalcopyrite structure of the films. For a film deposited by a pulse of energy density 0.8 J/cm2, free exciton and bound exciton emissions at 77 K were observed using photoluminescence (PL). The exciton emissions appear only at specific points in a PL‐intensity mapping. In addition, for the points with excitonic emission the composition ratio of the Cu and In was found to be very close to unity compared to other areas without emissions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:23.95739-05:0
      DOI: 10.1002/pssc.201400352
       
  • Fabrication of visible‐light transparent solar cells composed of
           NiO/NixZn1‐xO/ZnO heterostructures
    • Authors: Daisuke Kawade; Kazuma Moriyama, Fumika Nakamura, Shigefusa F. Chichibu, Mutsumi Sugiyama
      Abstract: Visible‐light transparent solar cells were fabricated using p ‐type NiO and n ‐type ZnO by conventional RF reactive sputtering with NiZnO alloy as an intrinsic interlayer. The energy band diagrams of NiO/NiZnO/ZnO heterojunctions were revealed by photoelectron yield spectroscopy, and the band gap energies were estimated to be 1.2 eV for NiO/Ni0.4Zn0.6O and 0.6 eV for Ni0.4Zn0.6O/ZnO heterojunctions. By using In2O3:Sn (ITO) as a transparent electrode in NiO‐based visible‐light transparent solar cells, a small but noticeable photovoltaic effect was obtained. The short‐circuit current density (Jsc) increased from 4 μA/cm2 to 12 μA/cm2 due to the insertion of Ni0.4Zn0.6O interlayer. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:18.086297-05:
      DOI: 10.1002/pssc.201400256
       
  • Deposition of Cl‐doped CdTe polycrystalline films by
           close‐spaced sublimation
    • Authors: Tamotsu Okamoto; Kohei Takahashi, Sho Akiba, Nao Yasuda, Satoshi Tokuda, Hiroyuki Kishihara, Akina Ichioka, Takahiro Doki, Toshiyuki Sato
      Abstract: The effects of Cl‐doping on the CdTe layers by the close‐spaced sublimation (CSS) deposition were investigated. Cl‐doped CdTe polycrystalline films were deposited on graphite substrates by CSS method using a mixture of CdTe and CdCl2 powder as a source. In X‐ray diffraction (XRD) patterns of the obtained films with various deposition times, many diffraction peaks other than CdTe peaks were observed in the deposition times lower than 10 min. These diffraction peaks were probably due to the formation of chlorides of Cd, Te and C, such as CdCl2, TeCl4, Te3Cl2 and C10Cl8. X‐ray fluorescence (XRF) and secondary ion mass spectrometry (SIMS) analyses revealed that a large amount of chlorine was contained in the films with the deposition times lower than 10 min, and that Cl concentration decreased with increasing the deposition time above 3 min. These results indicate that the films containing the chlorides of Cd, Te and C in addition to CdTe are formed in the initial stage of the CSS deposition using a mixture of CdTe and CdCl2 powder as a source. Cross‐sectional images revealed that the grain size was decreased by the effect of Cl‐doping. Furthermore, current‐voltage (I ‐V) characteristics of the CdTe/graphite structures were measured, and it was found that the resistivity of the Cl‐doped CdTe layer was much higher than that of the undoped CdTe layer. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:17.009612-05:
      DOI: 10.1002/pssc.201400257
       
  • Structure and optical properties of CdS:O films by cathode sputtering
    • Authors: Masahiro Nakajima; Ryo Asaba, Akinori Suzuki, Yong‐Gu Shim, Kazuki Wakita, Kh. Khalilova, Nazim Mamedov, Ayaz Bayramov, Emil Huseynov
      Abstract: We have studied the structure and optical properties of CdS:O films deposited on SLG (soda lime glass) substrates by cathode sputtering in the atmosphere of oxygen/argon gases. According to X‐ray diffraction (XRD) and confocal Raman scattering data, the films annealed in vacuum at temperatures above 300 °C exhibited crystalline structure of CdS. On the other hand, XRD, confocal Raman scattering, AFM (atomic force microscopy) and TEM (transmission electron microscopy) data indicated amorphous structure nano‐crystallization in CdS:O films annealed in vacuum at 400 °C. For the films, the emissions located at 3.35 eV were evident from photoluminescence measurements. The origin of this energy gap is discussed by taking into account redistribution of electronic density of states in the amorphous phase and quantum‐size effect. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:14.194475-05:
      DOI: 10.1002/pssc.201400347
       
  • Growth and characteristics of amorphous silica‐modified polyaniline
           films for ammonia sensor application
    • Authors: Majvell Kay Odarve; Reynaldo Vequizo
      Abstract: The characteristic properties of the nanostructured polyaniline (PAni) films synthesized via chemical oxidative polymerization of aniline on glass substrates using amorphous cristobalite silica (SiO2) as structural growth director are presented in this study. The change in the resistance of the sample was monitored upon exposure to ammonia gas using two‐probe method for two cycles, 40 min each. The structural and morphological property of the PAni/SiO2 samples were studied and compared to PAni samples alone using FTIR spectroscopy and scanning electron microscopy. It was found out that PAni/SiO2 films have higher and uniform response to ammonia with good repeatability during the two cycles and recovery upon removal of ammonia source. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:13.148346-05:
      DOI: 10.1002/pssc.201400318
       
  • Bulk crystal growth and characterization of ZnSnP2 compound semiconductor
           by flux method
    • Authors: Shigeru Nakatsuka; Hiroshi Nakamoto, Yoshitaro Nose, Tetsuya Uda, Yasuharu Shirai
      Abstract: ZnSnP2 is a promising candidate for solar absorber materials from the viewpoint of high absorption and earth‐abundant constitution elements. In this paper, we fabricated ZnSnP2 crystals by flux method based on the phase diagram of Sn‐ZnP2 pseudo‐binary system and investigated their properties for an application to photovoltaics. The crystal growth experiments with the cooling rate of 0.7 and 12 °C/h were carried out and we successfully obtained ZnSnP2 crystals with the diameter of 8mm and the thickness of a few mm by a slow cooling rate. The structure of grown crystals studied by X‐ray diffraction was indicated to be chalcopyrite‐type ZnSnP2. In addition, the decrease of the degree of order was observed with the increase of cooling rate. The lattice constants of a and c axes are 5.649 and 11.295 Å, respectively. The composition of grown crystals is a near stoichiometric ratio of ZnSnP2 by EDX analysis. The bandgaps of ZnSnP2 crystals obtained by cooling rate of 0.7 and 12 °C/h were estimated to be 1.61 and 1.48 eV, respectively, which is caused by the difference of the degree of order. The hall‐resistivity measurement showed that ZnSnP2 crystals with a slow cooling rate has a p‐type conduction. The resistivity, the hole concentration and the mobility are 10∼70 Ωcm, 6·1016∼2·1017 cm‐3, and 1∼3 cm2V‐1s‐1. The obtained properties are suitable for an absorber of photovoltaics. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:12.061845-05:
      DOI: 10.1002/pssc.201400291
       
  • Crystallization mechanism of sol‐gel synthesized spinel LiMn2O4
    • Authors: K. Kushida; K. Kuriyama
      Abstract: Crystallization mechanism of sol‐gel synthesized spinel LiMn2O4 is studied by a differential scanning calorimetry (DSC) method. Lithium acetate and manganese acetate are dissolved in methanol in the atomic ratio of 1:2 (Li:Mn) with citric acid as a chelating agent, leading to a sol solution. A Li‐Mn gel precursor is obtained by partly evaporating the sol solution. A large exothermic reaction of the Li‐Mn gel starts at 280 °C, indicating that the combustions of C and H atoms released from the gel occur above 280 °C. After the rise in temperature to 290 °C, the exothermic reaction of the gel continues at the constant temperature of 290 °C, indicating that the rearrangement of Li, Mn and O atoms for the crystallization into the spinel structure mainly occurs at 290 °C. This suggests that annealing the Li‐Mn gel precursor above 290 °C is necessary to obtain spinel LiMn2O4. During the exothermic reaction, Mn atoms released from the gel occupy the octahedral sites in the spinel framework of O, and Li atoms also released are inserted into the tetrahedral sites. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:11.073234-05:
      DOI: 10.1002/pssc.201400289
       
  • Fabrication of Cu2ZnSnSe4 thin films by selenization of precursor using
           Cu2ZnSnSe4 compound for photovoltaic applications
    • Authors: M. Nakashima; T. Yamaguchi, K. Kusumoto, S. Yukawa, J. Sasano, M. Izaki
      Abstract: Cu2ZnSnSe4 ingot was synthesized and then used it and Na2Se powder as evaporation materials to prepare a precursor for selenization process in order to fabricate Cu2ZnSnSe4 thin films for solar cell applications. From EPMA analysis, the Sn content in the thin films was approximately constant with increasing Sn mole ratio and the Se content was under 50 at.% in the first experiment. The Se content in the thin films increased to around 50 at.% by the addition of Se layer in second experiment. XRD study showed that the thin films had a kesterite phase in Cu2ZnSnSe4. The Se layer addition enhanced to grow thin films having a close‐packed structure and columnar grains. Cu2ZnSnSe4 thin film solar cells demonstrated Voc= 282 mV, Isc= 3.00 mA/cm2. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:10.003037-05:
      DOI: 10.1002/pssc.201400279
       
  • First‐principles study of doping properties in ZnSnAs2
    • Authors: Masato Ishikawa; Takashi Nakayama
      Abstract: Doping properties in ZnSnAs2 compound semiconductors were studied by the first‐principles spin‐polarized calculation. We have shown that the Ga doping into Zn site produces an ideal n‐type system with small effective mass, not sensitive to the doping concentration, which feature merits the optical isolator application. On the other hand, the Mn doping into Sn site induces a large spin moment around S=1, which merits the spintronics application. When the Mn concentration is increased, however, Mn atoms prefer to locate nearby and the spin moment decreases by the anti‐ferromagnetic interaction between Mn atoms. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:08.788846-05:
      DOI: 10.1002/pssc.201400277
       
  • Cu2SnS3 thin film solar cells prepared by thermal crystallization of
           evaporated Cu/Sn precursors in sulfur and tin atmosphere
    • Authors: M. Nakashima; T. Yamaguchi, H. Itani, J. Sasano, M. Izaki
      Abstract: Cu2SnS3 thin films were prepared by crystallization in sulfur and tin mixing atmosphere from the stacked Cu/Sn precursors deposited by sequential evaporation of Sn and Cu elements. From EPMA analysis, the composition of the thin film was approximately constant regardless changing Sn mole ratio in the precursor. However, the composition of inside of the thin films and Mo layer had gradation. The Raman analysis showed that the spectrum corresponded to monoclinic Cu2SnS3. Cu2SnS3 thin films were applied to the fabrication of Cu2SnS3 solar cells. The values of Voc and Isc increased with decreasing Sn mole ratio in the precursor. The largest Voc of 247.5 mV was achieved in sample of Cu/Sn mole ratio of 2/1.2, which is comparable with early reported value of Voc. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:07.574195-05:
      DOI: 10.1002/pssc.201400269
       
  • Effect of supercritical carbon dioxide treatment on the polarons of
           HCl‐doped polyaniline films
    • Authors: J. G. Fernando; R. M. Vequizo, M. K. G. Odarve, B. R. B. Sambo, R. M. Malaluan, L. A. M. Malaluan
      Abstract: In situ HCl‐doped polyaniline films were synthesized on glass substrates via chemical oxidative polymerization of aniline using ammonium peroxydisulfate as oxidant. The films were treated with supercritical carbon dioxide (SC‐CO2) at 30 MPa and 40 °C for 30 minutes. The physico‐chemical and electrical properties of the films were determined to establish the effect of supercritical carbon dioxide treatment on the polaron structures of polyaniline films. The treatment removed limited number of polarons which affected the properties of polyaniline. The treated films remained conducting despite that the conductance decreased substantially. The treatment enhanced the quinoid character of the films and altered the HOMO‐LUMO transitions. In addition, SC‐CO2 treatment was unable to remove the PANI precipitations adhering on the surface of the films. A mechanism on the effect of SC‐CO2 interaction to HCl‐doped PANI films was proposed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:06.432144-05:
      DOI: 10.1002/pssc.201400262
       
  • A mild hydrothermal route to synthesis of CZTS nanoparticle inks for solar
           cell applications
    • Authors: S. A. Vanalakar; G. L. Agwane, M. G. Gang, P. S. Patil, J. H. Kim, J. Y. Kim
      Abstract: Cu2ZnSnS4 (CZTS) is a promising thin film absorber material for low cost solar cell applications. Its absorption coefficient (∼ 104 cm‐1), crystal structure and band gap energies (∼1.5 eV) are similar to those of Cu(In,Ga)Se2 (CIGS), one of the most studied and flourishing thin film solar cell absorber materials. However, unlike CIGS, which requires the expensive and rare elements; In and Ga, CZTS is composed of reasonably priced and abundant elements like Zn and Sn. In the present investigation, kesterite CZTS nanoparticle inks were obtained by a hydrothermal process using Cu, Zn and Sn chlorides, and Na sulfide. The synthesized CZTS nanoparticles were characterized using optical absorption, X‐ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), micro‐Raman spectroscopy, high‐resolution transmission electron microscopy (HRTEM), and X‐ray photoelectron spectroscopy (XPS). The optical and morphological properties demonstrated that the prepared nanoparticles have strong absorption in 300−550 nm range with band gap energy of 1.55 eV with an average particle size of 20 nm. The X‐ray and micro‐Raman analysis revealed that the synthesized CZTS nanoparticles have the phase pure kesterite structure. We believe that our synthetic method will be helpful for low‐cost and efficient thin film photovoltaic technology. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:30:05.46824-05:0
      DOI: 10.1002/pssc.201400261
       
  • Minority carrier diffusion length in AlxGa1‐xN (x = 0.1) grown by
           ammonia molecular beam epitaxy
    • Authors: Timur Malin; Alexander Gilinsky, Vladimir Mansurov, Dmitriy Protasov, Eugeny Yakimov, Konstantin Zhuravlev
      Abstract: The room‐temperature minority carrier diffusion length in n ‐Al0.1Ga0.9N grown by ammonia molecular beam epitaxy on (0001) sapphire for photodetector applications has been investigated. The measurements were performed using the spectral dependence of the photocurrent detected by the built‐in p‐n ‐junction on thinner layer samples, and by the electron beam induced current technique on films of up to 2 µm in thickness. The results show that the hole diffusion length in n ‐AlGaN films amounts to 120‐150 nm, which is by 3‐4 times larger than that in GaN films grown under similar growth conditions. The thicker films do not show a considerable improvement in the hole diffusion length value. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:20:13.593975-05:
      DOI: 10.1002/pssc.201400180
       
  • Power dependence of unusual bands in photoluminescence spectra of
           AlGaN/GaN heterostructures
    • Authors: I. V. Osinnykh; K. S. Zhuravlev, T. V. Malin
      Abstract: AlGaN/GaN heterostructures with a two‐dimensional electron gas (2DEG) grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) techniques were investigated by photoluminescence (PL) spectroscopy. Series of PL bands located below the donor bound excitons band have been observed for a high quality MOCVD sample. Two of these PL bands peaked at ħωmax=3.446 and ħωmax=3.423 eV have been observed at both continuous and pulse excitation and connected with the recombination of 2DEG localized at the first and the second levels in the quantum well with free holes. The PL band at ħωmax=3.36 eV may be attributed to recombination of the 2DEG electrons with holes located at acceptors. Band at ħωmax=3.41 eV is not connected with 2DEG because of this band didn’t disappear after etching of the AlGaN layer and this band was observed in all samples. An intensity of all these four PL bands increased superlinearly with rise of the excitation power. The exponents for the Y bands more than 2, while the exponent for the excitonic band is about 1.5 at T=5 K. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:20:12.751989-05:
      DOI: 10.1002/pssc.201400179
       
  • Effect of reactor pressure on optical and electrical properties of InN
           films grown by high‐pressure chemical vapor deposition
    • Authors: Mustafa Alevli; Nese Gungor, Sabri Alkis, Cagla Ozgit‐Akgun, Inci Donmez, Ali Kemal Okyay, Sampath Gamage, Indika Senevirathna, Nikolaus Dietz, Necmi Biyikli
      Abstract: The influences of reactor pressure on the stoichiometry, free carrier concentration, IR and Hall determined mobility, effective optical band edge, and optical phonon modes of HPCVD grown InN films have been analysed and are reported. The In 3d, and N 1s XPS spectra results revealed In‐N and N‐In bonding states as well as small concentrations of In‐O and N‐O bonds, respectively in all samples. InN layers grown at 1 bar were found to contain metallic indium, suggesting that the incorporation of nitrogen into the InN crystal structure was not efficient. The free carrier concentrations, as determined by Hall measurements, were found to decrease with increasing reactor pressure from 1.61×1021 to 8.87×1019 cm‐3 and the room‐temperature Hall mobility increased with reactor pressure from 21.01 to 155.18 cm2/Vs at 1 and 15 bar reactor pressures, respectively. IR reflectance spectra of all three (1, 8, and 15 bar) InN samples were modelled assuming two distinct layers of InN, having different free carrier concentration, IR mobility, and effective dielectric function values, related to a nucleation/interfacial region at the InN/sapphire, followed by a bulk InN layer. The effective optical band gap has been found to decrease from 1.19 to 0.95 eV with increasing reactor pressure. Improvement of the local structural quality with increasing reactor pressure has been further confirmed by Raman spectroscopy measurements. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-30T02:20:11.55197-05:0
      DOI: 10.1002/pssc.201400171
       
  • The effects of Al on the neutral Mg acceptor impurity in AlxGa1‐xN
    • Authors: U. R. Sunay; M. E. Zvanut, A. A. Allerman
      Abstract: High hole concentrations in AlxGa1‐xN become increasingly difficult to obtain as the concentration of Al increases. It is well known in GaN and related alloys that hole concentration is directly affected by compensation and extended defects. Using electron paramagnetic resonance (EPR) spectroscopy, we studied the amount of neutral Mg in AlxGa1‐xN with x = 0 to 0.28. 0.4‐0.9 μm thick Mg‐doped AlxGa1‐xN films were grown by metal‐organic chemical vapour deposition and annealed at 900 °C anneal in N2. EPR measurements indicate that the amount of neutral Mg decreased by 60% in AlxGa1‐xN films for x = 0.18 and 0.28 as compared to x=0.00 and 0.08. Experiments also showed that the lower neutral Mg for higher Al compositions trend did not depend on threading dislocation densities in the range of 3‐20x109 cm‐2, capping the surface with 5 nm of P+ GaN, or detailed annealing conditions. Additional studies show that oxygen and carbon concentrations are insufficient to account for the decrease in neutral Mg observed in the samples. Although the study cannot isolate the cause for the decrease in neutral Mg, the results clearly demonstrate that the acceptor concentration decreases with increasing Al, providing an additional limitation to achieving high hole densities. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:39.097403-05:
      DOI: 10.1002/pssc.201400184
       
  • Electron paramagnetic resonance studies of bulk Mg‐doped GaN grown
           by high nitrogen pressure solution method
    • Authors: J. Dashdorj; W. R. Willoughby, M. E. Zvanut, M. Bockowski
      Abstract: An acceptor‐related impurity was studied in bulk free standing GaN using electron paramagnetic resonance spectroscopy. Both undoped and Mg‐doped substrates grown by the high nitrogen pressure solution method were examined, but only the doped sample revealed the presence of an EPR‐detected center. Comparison with earlier work on p ‐type GaN films suggests that the defect is an acceptor, heavily compensated during growth. Photo‐EPR studies revealed a photo‐ionization threshold of 2.8 eV, which is interpreted as excitation of an electron from the acceptor to the conduction band. Based on the concentration and photo‐threshold, the EPR center detected in the HNPS doped samples is tentatively identified as Be, which SIMS measurements indicate is a trace impurity in the doped GaN sample. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:37.662444-05:
      DOI: 10.1002/pssc.201400181
       
  • Efficiency of UVA LEDs grown by HVPE in relation with the active region
           thickness
    • Authors: Sergey Kurin; Andrey Antipov, Iosif Barash, Alexander Roenkov, Alexander Usikov, Heikki Helava, Yuri Makarov, Alexander Solomonov, Sergey Tarasov, Anton Evseenkov, Ivan Lamkin
      Abstract: We report on results of the performance study of UVA LEDs depending on the thickness of the active region. UVA LEDs are based on GaN/AlGaN heterostructures grown on Al2O3 (0001) substrates by hydride vapor phase epitaxy (HVPE). It is shown that the use of thick (̴ 100 nm) single layer as the active region of UVA LED is a promising concept to achieve enhanced efficiency. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:36.633618-05:
      DOI: 10.1002/pssc.201400178
       
  • Surface polariton spectroscopy of AlN films grown by ammonia MBE on (0001)
           Al2O3 substrate
    • Authors: N. N. Novikova; E. A. Vinogradov, V. A. Yakovlev, T. V. Malin, V. G. Mansurov, K. S. Zhuravlev
      Abstract: Surface polariton (SP) spectra of nitridated sapphire and rather thick (1 µm) AlN films on sapphire have been measured using attenuated total reflection technique. The high sensitivity of SP allows to see the sapphire spectra change after nitridation of sapphire and even variations parameters of the nitridation procedure. SP dispersion curves depend on degree of conversion of an initial sapphire surface layer into crystalline AlN during the nitridation procedure. The TO frequencies of formed AlN films are higher than the frequency reported for the AlN single crystal indicating the increase of the lattice constant. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:35.669586-05:
      DOI: 10.1002/pssc.201400177
       
  • Blue to true green LEDs with semipolar quantum wells based on GaN
           nanostripes
    • Authors: Robert A. R. Leute; Junjun Wang, Tobias Meisch, Joachim Biskupek, Ute Kaiser, Ferdinand Scholz
      Abstract: Recent advances of the performance of GaN based devices with semipolar quantum wells have been realized homoepitaxially on pseudo bulk substrates which are typically small in size and high in cost. These limitations fuel the search for cheap and large area alternatives. Heteroepitaxial growth on sapphire substrates is well established with excellent results for polar GaN structures ‐ the growth of semipolar gallium nitride on sapphire, however, presents unique challenges. In order to profit from our expertise in c‐plane samples, our semipolar gallium nitride growth experiments are based on growth in c‐direction. Using selective area epitaxy (SAE) on c‐oriented templates, we can grow 3D structures with semipolar side facets. These structures are typically several μm in size which constitutes further challenges for device processing. Reducing the size of the structures to a sub‐μm scale, we are able to bury our semipolar QWs within planar layers resulting in flat samples with c‐plane surfaces. In this contribution, we present our results concerning the structural quality and spectral properties of quantum wells emitting in the blue and green spectral range as well as light emitting diodes. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:33.740958-05:
      DOI: 10.1002/pssc.201400176
       
  • High power blue AlGaInN LED chips with two‐level metallization
    • Authors: D. A. Zakheim; G. V. Itkinson, M. V. Kukushkin, L. K. Markov, O. V. Osipov, A. S. Pavluchenko, I. P. Smirnova, D. A. Bauman
      Abstract: In this paper, we report on the development and fabrication of high power LED chips based on AlGaInN. These chips are meant for flip‐chip mounting and have novel contact pad topology utilizing two‐level metallization with the intermediate dielectric isolation. The size and shape of highly reflective ITO/Ag‐based p‐type and Ti/Ag based n‐type contact pads were adjusted with the use of the numerical simulations of current spreading. As a result, the developed chip has 1 mm2 active area and series resistance as low as 0.3 Ω. The fabricated LEDs demonstrate emission power of 542 mW at 350 mA and the maximum external quantum efficiency equal to 60%. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:32.492114-05:
      DOI: 10.1002/pssc.201400174
       
  • Improved GaN films with low background doping and low deep trap density
           grown by hydride vapor phase epitaxy
    • Authors: Alexander Polyakov; Nikolai Smirnov, Anatoli Govorkov, Elena Kozhukhova, Tatiana Yugova, Alexander Usikov, Heikki Helava, Yuri Makarov
      Abstract: Electrical properties and deep electron and hole traps spectra are compared for undoped n‐GaN films grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates at 850 °C (Group 1) and 950 °C (Group 2). Group 1 samples have very low residual donor concentration ((2‐5)×1014 cm‐3), very low density of electron and hole traps, low leakage current of Schottky diodes. Group 2 samples are not very different from the usual thick HVPE samples in terms of predominant electron and hole traps and MCL spectra. But the concentration of both electron and hole traps is quite high and could contribute to rather high reverse leakage current, low photocurrent and pronounced tunneling. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:31.266409-05:
      DOI: 10.1002/pssc.201400173
       
  • Simulation of the stress state of GaN‐AlN based epitaxial devices
    • Authors: Arun Kumar; Ganesh Iyer, Anandh Subramaniam
      Abstract: The stress state plays an important role in the performance of GaN‐AlN based multilayer epitaxial devices and their degradation with time. The stress state arises due to the superposition of stresses originating from multiple sources: (i) thermal mismatch, (ii) epitaxial growth, (iii) low angle grain boundaries (threading dislocations) and (iv) interfacial misfit edge dislocations. The current investigation pertains to the plane strain linear elastic finite element simulation of the stress state of a model GaN‐AlN high electron mobility transistor (HEMT) device on a Si substrate, taking into account the above‐mentioned sources of stresses. The value of stresses arising from grain boundary dislocations corresponds to the experimental results and imposed as tractions in the numerical model, while the other stresses are modelled using eigenstrains in appropriate regions in the finite element domain. A ten step simulation strategy is developed to simulate the stress state of the entire HEMT device. It is seen that: (i) the AlN layers are under tensile stress, (ii) the embedded GaN layers are under compressive stress, (iii) the GaN layer between source and drain is under tensile stress, (iv) the AlGaN layer is under tensile stress, (v) the source and the drain are mostly in tensile stress, while the gate is nearly stress‐free. The AlGaN and GaN layers (close to the source and drain) are under tensile stress (by considerations of pure epitaxy these are expected to be under compression). The critical thickness for the stability of a misfit edge dislocation at the AlN‐GaN interface is computed using the simulations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:29.757345-05:
      DOI: 10.1002/pssc.201400170
       
  • 2D AlN crystal phase formation on (0001) Al2O3 surface by ammonia MBE
    • Authors: Timur Malin; Vladimir Mansurov, Yury Galitsyn, Konstantin Zhuravlev
      Abstract: Kinetics of a two‐dimensional (2D) AlN layer formation on (0001) sapphire (Al2O3) surface during nitridation at different ammonia fluxes is investigated by reflection high energy electron diffraction (RHEED). The process on the surface is described in the framework of a chemical reactions kinetic model including interaction between partially reduced aluminum oxide species (AlO) and chemisorbed NH2 particles. The experimentally determined AlN formation rates as functions of both the temperature and the ammonia pressure are successfully described by a simple set of kinetic equations. Calculated maximum rate of the process well agrees with the experimental values. Precision measurement of 2D AlN lattice parameters during the nitridation process detects the value of 3.01 Å. This value coincides exactly with a characteristic structure parameter of the oxygen‐deficient Al2O3 surface. We assume this coincidence results from flexibility of the 2D AlN monolayer which provides minimization of elastic stresses at the AlN/(0001)Al2O3 interface. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:28.350806-05:
      DOI: 10.1002/pssc.201400168
       
  • Contents: Phys. Status Solidi C 4–5/2015
    • Pages: 327 - 330
      PubDate: 2015-04-17T03:21:54.027087-05:
      DOI: 10.1002/pssc.201570082
       
  • Growth of III‐Nitrides
    • Authors: Russell D. Dupuis; Fernando A. Ponce
      Pages: 331 - 333
      Abstract: The International Symposium on the Growth of III‐Nitrides (ISGN) series of conferences have been premier international forums for experts from academia, industry, and national laboratories to present their latest progress and exchange ideas in the fundamental and applied aspects of III‐N bulk and epitaxial growth technologies as well as related device advances. III‐N compound semiconductor materials underlie many of today's most advanced high‐performance devices such as LEDs, laser diodes, and transistors, which are becoming an essential part of the solution of many global problems. In the future, III‐N solar cells, nanostructure materials, and other innovative devices will play a similar significant role in improving the human condition. The primary purpose of ISGN‐5 was to foster the continued advance of this important field of research and development. The ISGN‐5 was organized by a team of US‐based experts in the field and the choice of Plenary and Invited speakers was based upon inputs from the International Advisory Committee composed of active III‐N researchers from all over the world. We actively solicited papers describing the latest work in the following technical areas: – III‐N bulk growth: AlN, GaN, InN – Epitaxial growth techniques – Ternary and quaternary alloys – III‐N nanostructures – Defect control and surface effects – Optical and electrical properties – III‐N magnetic and spin‐related phenomena – III‐N devices: FETs, HBTs, rectifiers, LEDs, lasers, photodetectors, and novel devices The ISGN‐5 program had fourteen regular sessions and two poster sessions scheduled over four days. The total number of attendees was 146. The conference technical sessions began with a plenary talk by André Strittmatter who described the current state‐of‐the‐art of GaN on Si. The regular sessions were begun with Invited Speakers. The full conference schedule is available here: http://www.mrs.org/isgn‐5‐program/. The primary conference support was provided by AIXTRON, Sandia National Laboratories, the U.S. National Science Foundation, and the U.S. Army Research Office. We were fortunate to have the on‐site support of eleven commercial vendors of equipment and services related to III‐N materials and devices who arranged to have a booth at ISGN‐5 to display and demonstrate their products. These companies included AIXTRON, Aymont Technology Inc., Evans Analytical Group, HexaTech, Inc., k‐Space Associates, Inc., KITZ SCT America Corporation, Nitride Crystals, Inc., Proton OnSite, Riber, Inc., Semiconductor Technology Research–STR Group, and Taiyo Nippon Sanso Corporation. The ISNG‐5 proceedings Guest Editors were Christian Wetzel (Rensselaer), Jae‐Hyun Ryou (University of Houston), and Michael Manfra (Purdue University). We thank the sponsors, the exhibitors, the Materials Research Society staff, the members of the Conference Organizing Committee, the members of the International Advisory Committee and of the Program Committee, and everyone who attended for their support. The ISGN‐5 Symposium Chairs, Russell D. Dupuis, Georgia Institute of Technology Fernando A. Ponce, Arizona State University
      PubDate: 2015-04-17T03:21:52.749639-05:
      DOI: 10.1002/pssc.201570083
       
  • HVPE homoepitaxy on freestanding AlN substrate with trench pattern
    • Authors: Yoshinobu Watanabe; Hideto Miyake, Kazumasa Hiramatsu, Yosuke Iwasaki, Shunro Nagata
      Pages: 334 - 337
      Abstract: Conditions on chemical surface treatment and thermal treatment of sublimation‐freestanding AlN substrates were investigated to remove damage layers on surfaces for high‐quality and crack‐free AlN films grown by hydride vapour phase epitaxy (HVPE). By wet etching, the residue on the surface was removed and the polishing scratches were reduced. Atomic steps were formed on the surface by the subsequent thermal treatment at 1450 °C for 10 min, and surface layer of 220 nm in thickness was removed, Homoepitaxial growth on freestanding AlN substrate with trench pattern was also performed. A crack‐free AlN film with atomic steps was obtained on the trench‐patterned bulk AlN substrate, and the emission at the band edge near 206.9 nm was dominant. The wavelength of luminescence from cross‐sectional and surface of the HVPE‐AlN layer was maintained. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:48.179394-05:
      DOI: 10.1002/pssc.201400202
       
  • Modeling micromechanical response to thermal history in bulk grown
           aluminum nitride
    • Authors: Payman Karvani; Antoinette M. Maniatty
      Pages: 345 - 348
      Abstract: A thermal‐elastic‐viscoplastic model suitable for modeling aluminum nitride (AlN) during crystal growth is presented. A crystal plasticity model that considers slip along crystallographic slip systems and the evolution of mobile and immobile dislocations on the prismatic and basal slip systems is developed. The model has been implemented into a finite element framework, and a sublimation growth process is modeled to demonstrate the model capability. The dislocation density, which characterizes the crystal quality, and the maximum tensile stress on the cleavage planes (m ‐planes), which leads to cracking, are computed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-04-17T03:21:53.01423-05:0
      DOI: 10.1002/pssc.201400189
       
  • Degradation of external quantum efficiency of AlGaN UV LEDs grown by
           hydride vapor phase epitaxy
    • Authors: Natalia Shmidt; Alexander Usikov, Eugenia Shabunina, Anton Chernyakov, Alexey Sakharov, Sergey Kurin, Andrei Antipov, Iosif Barash, Alexander Roenkov, Heikki Helava, Yuri Makarov
      Pages: 349 - 352
      Abstract: A comparative study of the degradation of HVPE‐grown 360 nm AlGaN/GaN UV and commercially available InGaN/GaN blue LED chips was performed. The common feature of the degradation of these two types of LEDs was found to be the increase of the conductivity of shunt paths under current injection. The paths (shunts) are localized in the extended defects system (EDS). It is proposed that the conductivity increase is due to defect formation under multiphonon carriers recombination in a part of the EDS enriched by Ga or In atoms. This process is accompanied by a local overheating and migration of Ga or In atoms. To increase the lifetime of the AlGaN/GaN UV LEDs to more than 2000 h it is necessary to improve their nano‐structural and nanoscale AlGaN composition ordering. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:46.189625-05:
      DOI: 10.1002/pssc.201400172
       
  • Time‐resolved photoluminescence characterization of 2 eV band in AlN
    • Authors: Ivan A. Aleksandrov; Vladimir G. Mansurov, Victor F. Plyusnin, Konstantin S. Zhuravlev
      Pages: 353 - 356
      Abstract: We report time‐resolved and temperature‐dependent photoluminescence investigations of 2 eV photoluminescence band in AlN with below bandgap excitation. Series of the samples grown by molecular beam epitaxy on sapphire substrates with varying growth conditions have been studied. Intensity of the 2 eV photoluminescence band has been found to increase with increasing III/V flux ratio. The 2 eV photoluminescence band has been described in one‐dimensional configuration coordinate model. A possible origin of this orange emission has been discussed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:47.139747-05:
      DOI: 10.1002/pssc.201400175
       
  • Fabrication of AlGaN multiple quantum wells on sapphire with
           lattice‐relaxation layer
    • Authors: Kazuhiro Nakahama; Fumitsugu Fukuyo, Hideto Miyake, Kazumasa Hiramatsu, Harumasa Yoshida, Yuji Kobayashi
      Pages: 361 - 364
      Abstract: The influences of three types of lattice‐relaxation layer between AlGaN multiple quantum wells (MQWs) and AlN layer on sapphire substrate were investigated. For structure (a), two‐high‐Al‐mole‐fraction AlGaN layers grown at 1170 °C was prepared. For structure (b), an AlN interlayer with growth temperature at 1450 °C was inserted between AlN/sapphire substrate and two‐high‐Al‐mole‐fraction AlGaN layer. For structure (c), an Al‐composition‐graded AlGaN layer with decreasing Al composition was grown after an AlN interlayer at 1450 °C by lowering the temperature gradually from the growth temperature of AlN. The narrowest rocking curve X‐ray diffraction at AlGaN MQWs occurs while using structure (b) as lattice‐relaxation layer. The highest emission intensity of cathodoluminescence from AlGaN MQWs at room temperature was also shown by using structure (b). The ratio of integrated intensity of spectra at 300 K and 10 K (I300K/I10K) is 58%. High temperature AlN films as lattice‐relaxation layer improved the crystal quality and emission intensity in AlGaN MQWs. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:20.654157-05:
      DOI: 10.1002/pssc.201400201
       
  • Study of interference effects on the photoluminescence of AlGaN/GaN
           quantum wells
    • Authors: M. Ramírez‐López; Y. L. Casallas‐Moreno, M. Pérez‐Caro, A. Escobosa‐Echevarria, S. Gallardo‐Hernández, J. Huerta‐Ruelas, M. Lopez‐Lopez
      Pages: 365 - 368
      Abstract: In this work we compared the optical properties of AlGaN(50 nm)/GaN(5 nm) quantum wells (QWs) grown by plasma‐assisted molecular beam epitaxy (PAMBE) technique, on Si(111) substrates and sapphire substrates. Optical properties were acquired by photoluminescence (PL) and reflectance (R) spectroscopies. Reflectance spectra shows interference oscillations of the reflected beam at Air/AlGaN and the beam reflected at bottom interface with Si substrate. Such oscillations vanish at the band gap of GaN buffer layer (3.4 eV). The PL spectra of samples grown on Silicon substrate shows a photoluminescence modulation effect, attributed to interference of light emitted from the QWs that is reflected at different heterostructure interfaces. On sapphire substrate no modulation effect is present. This could be explained due to interfacial roughness and the smaller refractive index of sapphire in comparison to silicon. PL shows a strong emission around 3 eV, which is in agreement with recombination energy determined by self‐consistent calculations, which consider a 4 MV/cm built‐in electric field and low carrier densities. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:25.077187-05:
      DOI: 10.1002/pssc.201400185
       
  • Reflectance analysis on the MOCVD growth of AlN on Si(111) by the virtual
           interface model
    • Authors: Tuoh‐Bin Ng; David A. Ewoldt, Debra A. Shepherd, Mark J. Loboda
      Pages: 385 - 388
      Abstract: The reflectance‐time profile of AlN‐on‐Si(111) growth by MOCVD as acquired through an in‐situ optical reflectance monitor is analyzed. It is found that, similar to the case of GaN‐on‐sapphire nucleation and growth through the low temperature GaN or AlN buffer layer techniques, the reflectance profile for AlN‐on‐Si also contains information that relate to the growth mechanism, which can then be correlated to the as‐grown material quality. Based on the equations for the Virtual Interface model, a set of 6 parameters can be used to curve‐fit the reflectance traces of AlN growth as acquired by the in‐situ optical monitor. By analyzing a range of 405 nm AlN reflectance‐time data from single layer AlN growth to multilayer AlN/AlGaN/GaN stack grown on Si(111), the “goodness of fit” statistics are found to correlate with material quality metrics such as the XRD (002) rocking curve FWHM for AlN, microscopic morphological roughness of the AlN surface, as well as the resultant wafer bow and curvature for GaN/AlGaN grown on the AlN/Si(111) substrate. The correlations provide useful insight into the desirable mechanism and growth mode for the high temperature MOCVD growth of AlN and GaN on Si(111). When fully established, the technique has the potential of being used as an in‐situ pass/fail screen for the MOCVD growth of GaN‐on‐Si. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:41.27289-05:0
      DOI: 10.1002/pssc.201400159
       
  • A numerical analysis of a MOCVD process for the growth of GaN nanowires
           using GaCl3 and NH3
    • Authors: Edgar Serrano Perez; Miguel A. Nuñez Velazquez, Fernando Juárez Lopez
      Pages: 389 - 393
      Abstract: In this paper, the analysis of horizontal cold wall reactor for GaN nanowires growing from GaCl3 and NH3 at atmospheric pressure conditions has been studied. It aims to provide better understanding of the MOCVD process especially of deposition process of GaN nanowires as well as fluid dynamics inside the reactor. Numerical solution to transport model coupled with 2D geometry using CFD shows several results including GaCl3 thermal decomposition at different temperature conditions, velocity and temperature distribution as well as concentration profiles into reactor. Afterwards experimental parameters of temperature and gases flow were set to growth of GaN nanowires. Scanning electron microscopy analysis shows the microstructural characteristics of GaN nanowires. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T06:50:42.903471-05:
      DOI: 10.1002/pssc.201400165
       
  • Low‐temperature hollow cathode plasma‐assisted atomic layer
           
    • Authors: Cagla Ozgit‐Akgun; Eda Goldenberg, Sami Bolat, Burak Tekcan, Fatma Kayaci, Tamer Uyar, Ali Kemal Okyay, Necmi Biyikli
      Pages: 394 - 398
      Abstract: Hollow cathode plasma‐assisted atomic layer deposition (HCPA‐ALD) is a promising technique for obtaining III‐nitride thin films with low impurity concentrations at low temperatures. Here we report our previous and current efforts on the development of HCPA‐ALD processes for III‐nitrides together with the properties of resulting thin films and nanostructures. The content further includes nylon 6,6‐GaN core‐shell nanofibers, proof‐of‐concept thin film transistors and UV photodetectors fabricated using HCPA‐ALD‐grown GaN layers, as well as InN thin films deposited by HCPA‐ALD using cyclopentadienyl indium and trimethylindium precursors. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:26.998226-05:
      DOI: 10.1002/pssc.201400167
       
  • SCM and SIMS investigations of unintentional doping in III‐nitrides
    • Authors: M. J. Kappers; T. Zhu, S.‐L. Sahonta, C. J. Humphreys, R. A. Oliver
      Pages: 403 - 407
      Abstract: Cross‐sectional scanning capacitance microscopy measurements of unintentionally doped model structures for InGaN quantum wells, GaN barriers and AlInN electron‐blocking layers showed n ‐type conductivity for the In‐containing layers. Secondary ion mass spectrometry indicated that oxygen impurities are the likely source of the electron density in the model layers. The n ‐type conductivity as well as the oxygen impurity level increases to ∼1018 cm‐3 for AlInN lattice‐matched to GaN. These results suggest that the background electron concentration due to oxygen impurities in indium‐containing layers needs to be considered in the design and theoretical modelling of device structures. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:19.646276-05:
      DOI: 10.1002/pssc.201400206
       
  • Kinetic Monte Carlo simulations of epitaxial growth of wurtzite GaN(0001)
    • Authors: Manjusha Chugh; Madhav Ranganathan
      Pages: 408 - 412
      Abstract: A lattice based kinetic Monte Carlo (kMC) simulation is developed to describe growth of GaN(0001) in conditions typical of a molecular beam epitaxy unit. Deposition and surface diffusion via attachment and detachment of atoms are the main processes considered in this model. The energy barriers for surface diffusion are estimated from ab‐initio density functional theory calculations. From the ab‐initio calculations, we identify a rapid motion of N atoms attached to Ga adatoms. Preliminary kMC simulation results indicate that this motion allows N adatoms to move towards their preferred positions and thereby facilitate smooth growth prior to the formation of the protective Ga adlayer which is believed to promote smooth growth under Ga rich conditions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:21.798767-05:
      DOI: 10.1002/pssc.201400194
       
  • Improved thermal stability and narrowed line width of photoluminescence
           from InGaN nanorod by ytterbium doping
    • Authors: Jingzhou Wang; Kiran Dasari, Kevin Cooper, Venkata R. Thota, Jason Wright, Ratnakar Palai, David C. Ingram, Eric A. Stinaff, S. Kaya, W. M. Jadwisienczak
      Pages: 413 - 417
      Abstract: Nanorod of in situ Yb‐doped InGaN and undoped InGaN have been grown on (0001) sapphire substrates by plasma assisted molecular beam epitaxy (MBE). Selected regions on Yb‐doped InGaN sample show single dominant near band edge emission (NBE) in green, yellow or orange color due to the variation of In content. Temperature dependent PL peak energy of InGaN nanorod shows the characteristic S ‐shaped behavior indicating the presents of strong exciton localization energy in undoped InGaN nanorod. The exciton localization energy reduced significantly after incorporating Yb into InGaN, giving rise to damping of the S‐shape profile amplitude and narrowing of the PL line width from ∼20 meV to ∼12 meV at 11 K. It is proposed that the improved PL thermal stability and the PL line width in Yb‐doped InGaN nanorod is affected by the Yb gettering effect. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T08:10:24.031155-05:
      DOI: 10.1002/pssc.201400186
       
  • Investigation of stress, defect structure and electrical conduction in
           large diameter III‐nitride epitaxy on silicon substrates
    • Authors: G. Chung; M. J. Loboda, E. Carlson, D. Ewoldt, T. Ng, D. Shepherd
      Pages: 418 - 422
      Abstract: The results of studies focused on understanding materials‐electrical correlations for GaN‐based films deposited on 150 mm diameter Si wafers in a batch MOCVD system are reported. A wide range of film stress and electrical conduction is observed at consistent and good X‐ray FWHM values. The vertical leakage currents show a strong asymmetry on the polarity of the bias voltage. Film stress (wafer bow) and impurity variations in the buffer layers show no correlation with leakage currents. Surface pit formation and conductive interfaces are critical to determine the leakage currents in buffer layers. TEM image confirms that surface pit stems from voids in Si substrate. The vertical leakage currents follow the Frenkel‐Poole conduction model at the trap energy of 0.7 eV. Vertical leakage currents measured in films can be reduced by a novel, post‐growth process. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-03-18T06:50:41.884366-05:
      DOI: 10.1002/pssc.201400137
       
  • Unusual phonon mode behaviour in zinc‐blende BN/GaN superlattices
    • Authors: Devki N. Talwar; Andrew F. Zhou, Tzuen‐Rong Yang
      Pages: 430 - 433
      Abstract: Comprehensive calculations of the long‐wavelength optical phonons are reported for zinc‐blende BN films by exploiting a linear response theory to simulate far‐infrared reflectivity and transmission spectra at oblique incidence. A rigid‐ion‐model is used to study the lattice dynamics of the unconventional BN/GaN short‐period superlattices (SLs). Besides empathizing, the anisotropic mode behaviour of optical phonons, the study has offered evidence of acoustic‐mode anti‐crossing, mini‐gap formation, confinement, as well as BN‐like modes falling between the gap regions separating the optical phonons of the two bulk (BN, GaN) semiconductor materials. A bond‐polarizability approach within the second‐nearest‐neighbour linear‐chain model is also employed to visualize the Raman intensity profiles of the short‐period BN/GaN SLs, revealing major trends of the phonon characteristics noted in many conventional SLs, while eliciting some interesting contrasts. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:45.055269-05:
      DOI: 10.1002/pssc.201400157
       
  • Plasma‐assisted molecular beam epitaxy of strain‐compensated
           a‐plane InGaN/AlGaN superlattices
    • Authors: Ryan W. Enck; N. Woodward, C. Gallinat, G. Metcalfe, A. V. Sampath, H. Shen, M. Wraback
      Pages: 434 - 438
      Abstract: Strain‐compensated InGaN/AlGaN structures can enable the growth of thick layers of InGaN epitaxial films far beyond the critical thickness for InGaN grown pseudomorphically to GaN. In this paper, we demonstrate the epitaxial growth of high‐quality strain‐compensated a‐plane In0.12Ga0.88N/Al0.19Ga0.81N superlattices up to 5 times thicker than the critical thickness on free‐standing a‐plane GaN substrates by plasma‐assisted molecular beam epitaxy (PA‐MBE). The superlattices consist of 50 to 200 periods of 10 nm thick In0.12Ga0.88N and 6 nm thick Al0.19Ga0.81N layers. The structures are characterized using a double crystal X‐ray diffractometer, asymmetric reciprocal space mapping, and atomic force microscopy. We use X‐ray diffraction to determine the strain, composition, degree of relaxation, and superlattice period of our samples. The structural characteristics of periodic structures containing from 50 to 200 periods are compared to single layer, uncompensated In0.12Ga0.88N films. A 100 period structure exhibited only 15% relaxation compared to 69% relaxation for the bulk In0.12Ga0.88N film grown with the same total InGaN thickness but without strain‐compensating layers. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-01-23T08:10:49.21007-05:0
      DOI: 10.1002/pssc.201400208
       
  • Challenges for Group III Nitride Semiconductors for Solid State Lighting
           and Beyond
    • Pages: 451 - 451
      PubDate: 2015-04-17T03:21:51.545713-05:
      DOI: 10.1002/pssc.201570084
       
  • Investigation of cubic GaN quantum dots grown by the
           Stranski‐Krastanov process
    • Authors: M. Bürger; J. K. N. Lindner, D. Reuter, D. J. As
      Pages: 452 - 455
      Abstract: We investigate the formation of cubic GaN quantum dots (QDs) on pseudomorphic strained cubic AlN layers on 3C‐SiC (001) substrates grown by means of molecular beam epitaxy. Surface morphologies of various QD sizes and densities were obtained from uncapped samples by atomic force microscopy. These results were correlated with similar but capped samples by photoluminescence experiments. The QD density varies by one order of magnitude from ∼1x1010 cm‐2 to ∼1x1011 cm‐2 as a function of the GaN coverage on the surface. The initial layer thickness for the creation of cubic GaN QDs on cubic AlN was obtained to 1.95 monolayers by a comparison between the experimental results and an analytical model. Our results reveal the strain‐driven Stranski‐Krastanov growth mode as the main formation process of the cubic GaN QDs. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-02-12T07:40:17.990154-05:
      DOI: 10.1002/pssc.201400132
       
  • Designing InGaN/GaN nano‐LED arrays for étendue‐limited
           applications
    • Authors: Sophia Fox; Simon O'Kane, Szymon Lis, Duncan Allsopp
      Pages: 456 - 459
      Abstract: This paper presents the far field results of a study by simulation using the finite‐difference time‐domain (FDTD) method of vertical light emitting diode structures with an incorporated ordered nanorod array in place of the typical surface roughened region. For a dipole placed directly below the centre nanorod in the FDTD model, highly collimated light is achieved by changing the radii of the nanorods, for a fixed array pitch, which we attribute mainly to Bragg diffraction. By changing the pitch only, higher diffraction orders are observed in the far field emission as the pitch is increased and a relative increase in the directionality of emission is predicted. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-02-12T07:40:19.018773-05:
      DOI: 10.1002/pssc.201400240
       
  • Computational model of 2DEG mobility in AlGaN/GaN heterostructures
    • Authors: Karine Abgaryan; Ilya Mutigullin, Dmitry Reviznikov
      Pages: 460 - 465
      Abstract: The computational scheme of multiscale modeling of semiconductor heterostructures is presented. Three scale levels are taken into account. On the atomic level the system is described using crystallographic information and quantum‐mechanical model. Ab initio modeling allows to determine the electronic structure, define polarization effects and calculate charge densities on the interfaces between layers. Obtained information is used in the nanoscale level model for the calculation of the charge carrier distribution in the heterostructure. At this level mathematical model contains the system of conjugated Schrödinger and Poisson equations. The carrier density distributions over the lateral direction of the multilayered structure and 2DEG localization are of the most interest at this point. This data is used in the next scale level model where electron mobility is calculated. A wide range of electron scattering mechanisms are taken into account during this calculation. This approach was applied to model 2DEG in AlGaN/AlN/GaN heterostructures. The good agreement between calculated values of interface charge density, 2DEG electron concentration, electron mobility and known experimental data was achieved. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-02-27T05:50:54.13433-05:0
      DOI: 10.1002/pssc.201400200
       
  • The temperature dependence of the luminescence of
           rare‐earth‐doped semiconductors: 25 years after Favennec
    • Authors: K. P. O'Donnell
      Pages: 466 - 468
      Abstract: Twentyfive years after the publication of P. N. Favennec's seminal paper on luminescence from rare‐earth‐doped semiconductors (Electron. Lett. 25, 718–719 (1989), with 390+ citations to date) we examine the long shadow it has cast on recent studies of europium‐doped GaN, aimed at substituting for InN‐rich InGaN in red‐light‐emitting devices (LEDs). According to Favennec's principle, wider band gap semiconductors should show weaker thermal quenching, thus favouring the III‐nitrides hugely. The conventional approach to fitting temperature dependences of light emission, based on competition between radiative and non‐radiative transitions, is presented here in simplified form and an alternative fitting equation proposed. The original data of Favennec (op. cit.) is re‐examined in the light of these fitting models. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-02-27T05:50:52.467273-05:
      DOI: 10.1002/pssc.201400133
       
  • STEM‐CL investigations on the influence of stacking faults on the
           optical emission of cubic GaN epilayers and cubic GaN/AlN
           multi‐quantum wells
    • Authors: R. M. Kemper; P. Veit, C. Mietze, A. Dempewolf, T. Wecker, F. Bertram, J. Christen, J. K. N. Lindner, D. J. As
      Pages: 469 - 472
      Abstract: We report the influence of {111} stacking faults on the cathodoluminescence (CL) emission characteristics of cubic GaN (c‐GaN) films and cubic GaN/AlN multi‐quantum wells. Transmission electron microscopy (TEM) measurements indicate that stacking faults (SFs) on the {111} planes are the predominant crystallographic defects in epitaxial films, which were grown on 3C‐SiC/Si (001) substrates by plasma‐assisted molecular beam epitaxy. The correlation of the SFs and the luminescence output is evidenced with a CL setup integrated in a scanning TEM (STEM). By comparing the STEM images and the simultaneously measured CL signals it is demonstrated that SFs in these films lead to a reduced CL emission intensity. Furthermore, the CL emission intensity is shown to increase with increasing film thickness and decreasing SF density. This correlation can be connected to the reduction of the full width at half maximum of X‐ray diffraction rocking curves with increasing film thickness of c‐GaN films. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-02-27T06:10:12.359989-05:
      DOI: 10.1002/pssc.201400154
       
  • Erratum: Influence of annealing on the properties of (Cd,Mn)Te crystals
    • Authors: M. Witkowska‐Baran; D. M. Kochanowska, A. Mycielski, R. Jakieła, A. Wittlin, W. Knoff, A. Suchocki, P. Nowa‐kowski, K. Korona
      Pages: 473 - 473
      Abstract: The authors have completed their institutions to properly reflect the contributions of the affiliated institutions.
      PubDate: 2015-04-17T03:21:55.561107-05:
      DOI: 10.1002/pssc.201570085
       
 
 
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