The effect of an initially grown high-temperature A1N buffer （HT-A1N） layer＇s thickness on the quality of an A1N epilayer grown on sapphire substrate by metalorganic chemical vapor deposition （MOCVD） in a two-ste...The effect of an initially grown high-temperature A1N buffer （HT-A1N） layer＇s thickness on the quality of an A1N epilayer grown on sapphire substrate by metalorganic chemical vapor deposition （MOCVD） in a two-step growth process is investigated. The characteristics of A1N epilayers are analyzed by using triple-axis crystal X-ray diffraction （XRD） and atomic force microscopy （AFM）. It is shown that the crystal quality of the A1N epilayer is closely related to its correlation length. The correlation length is determined by the thickness of the initially grown HT-A1N buffer layer. We find that the optimal HT-A1N buffer thickness for obtaining a high-quality A1N epilayer grown on sapphire substrate is about 20 nm.展开更多
We study the effect of the AlGaN interlayer on structural quality and strain engineering of the GaN films grown on SiC substrates with an AlN buffer layer, hnproved structural quality and tensile stress releasing are ...We study the effect of the AlGaN interlayer on structural quality and strain engineering of the GaN films grown on SiC substrates with an AlN buffer layer, hnproved structural quality and tensile stress releasing are realized in unintentionally doped GaN thin films grown on 6H-SiC substrates by metal organic chemical vapor deposition. Using the optimized AlGaN interlayer, we find that the full width at half maximum of x-ray diffraction peaks for GaN decreases dramatically, indicating an improved crystalline quality. Meanwhile, it is revealed that the biaxial tensile stress in the GaN film is significantly reduced from the Raman results. Photoluminescence spectra exhibit a shift of the peak position of the near-band-edge emission, as well as the integrated intensity ratio variation of the near-band-edge emission to the yellow luminescence band. Thus by optimizing the AlGaN interlayer, we could acquire the high-quality and strain-relaxation GaN epilayer with large thickness on SiC substrates.展开更多
Excitation power and temperature-dependent photoluminescence（PL） spectra of the ZnTe epilayer grown on（100）Ga As substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structu...Excitation power and temperature-dependent photoluminescence（PL） spectra of the ZnTe epilayer grown on（100）Ga As substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the Ga As substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor–acceptor pair（DAP） nor conduction band-acceptor（e–A） emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal.展开更多
The infrared reflectance spectra of both 4H SiC substrates and epilayers are measured in a wave number range from 400 cm 1 to 4000 cm-1 using a Fourier-transform spectrometer. The thicknesses of the 4H-SiC epilayers a...The infrared reflectance spectra of both 4H SiC substrates and epilayers are measured in a wave number range from 400 cm 1 to 4000 cm-1 using a Fourier-transform spectrometer. The thicknesses of the 4H-SiC epilayers and the electrical properties, including the free-carrier concentrations and the mobilities of both the 4H SiC substrates and the epilayers, are characterized through full line-shape fitting analyses. The correlations of the theoretical spectral profiles with the 4H-SiC electrical properties in the 30 cm-1-4000 cm 1 and 400 cm-1-4000 cm-1 spectral regions are established by introducing a parameter defined as error quadratic sum. It is indicated that their correlations become stronger at a higher carrier concentration and in a wider spectral region （30 cm-1-4000 cm-1）. These results suggest that the infrared reflectance technique can be used to accurately determine the thicknesses of the epilayers and the carrier concentrations, and the mobilities of both lightly and heavily doped 4H-SiC wafers.展开更多
A near-infrared germanium(Ge)Schottky photodetector(PD)with an ultrathin silicon(Si)barrier enhancement layer between the indium-doped tin oxide(ITO)electrode and Ge epilayer on Si or silicon-on-insulator(SOI)is propo...A near-infrared germanium(Ge)Schottky photodetector(PD)with an ultrathin silicon(Si)barrier enhancement layer between the indium-doped tin oxide(ITO)electrode and Ge epilayer on Si or silicon-on-insulator(SOI)is proposed and fabricated.The well-behaved ITO/Si cap/Ge Schottky junctions without intentional doping process for the Ge epilayer are formed on the Si and SOI substrates.The Si-and SOI-based ITO/Si cap/Ge Schottky PDs exhibit low dark current densities of 33 mA/cm2 and 44 mA/cm2,respectively.Benefited from the high transmissivity of ITO electrode and the reflectivity of SOI substrate,an optical responsivity of 0.19 A/W at 1550 nm wavelength is obtained for the SOI-based ITO/Si cap/Ge Schottky PD.These complementary metal–oxide–semiconductor(CMOS)compatible Si(or SOI)-based ITO/Si cap/Ge Schottky PDs are quite useful for detecting near-infrared wavelengths with high efficiency.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 60876009)
文摘The effect of an initially grown high-temperature A1N buffer （HT-A1N） layer＇s thickness on the quality of an A1N epilayer grown on sapphire substrate by metalorganic chemical vapor deposition （MOCVD） in a two-step growth process is investigated. The characteristics of A1N epilayers are analyzed by using triple-axis crystal X-ray diffraction （XRD） and atomic force microscopy （AFM）. It is shown that the crystal quality of the A1N epilayer is closely related to its correlation length. The correlation length is determined by the thickness of the initially grown HT-A1N buffer layer. We find that the optimal HT-A1N buffer thickness for obtaining a high-quality A1N epilayer grown on sapphire substrate is about 20 nm.
基金Supported by the National Key R&D Program of China under Grant No 2016YFB0400200
文摘We study the effect of the AlGaN interlayer on structural quality and strain engineering of the GaN films grown on SiC substrates with an AlN buffer layer, hnproved structural quality and tensile stress releasing are realized in unintentionally doped GaN thin films grown on 6H-SiC substrates by metal organic chemical vapor deposition. Using the optimized AlGaN interlayer, we find that the full width at half maximum of x-ray diffraction peaks for GaN decreases dramatically, indicating an improved crystalline quality. Meanwhile, it is revealed that the biaxial tensile stress in the GaN film is significantly reduced from the Raman results. Photoluminescence spectra exhibit a shift of the peak position of the near-band-edge emission, as well as the integrated intensity ratio variation of the near-band-edge emission to the yellow luminescence band. Thus by optimizing the AlGaN interlayer, we could acquire the high-quality and strain-relaxation GaN epilayer with large thickness on SiC substrates.
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120131110006)the Key Science and Technology Program of Shandong Province+10 种基金China(Grant No.2013GGX10221)the Key Laboratory of Functional Crystal Materials and Device(Shandong UniversityMinistry of Education)China(Grant No.JG1401)the National Natural Science Foundation of China(Grant No.61306113)the Major Research Plan of the National Natural Science Foundation of China(Grant No.91433112)the Partnership Project for Fundamental Technology Researches of the Ministry of EducationCultureSportsScience and TechnologyJapan
文摘Excitation power and temperature-dependent photoluminescence（PL） spectra of the ZnTe epilayer grown on（100）Ga As substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the Ga As substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor–acceptor pair（DAP） nor conduction band-acceptor（e–A） emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal.
基金supported by the National Natural Science Foundation of China (Grand No. 60876003)the Program of 2011 (2nd)Innovative Research Teams and Leading Talents in Guangdong Province of China
文摘The infrared reflectance spectra of both 4H SiC substrates and epilayers are measured in a wave number range from 400 cm 1 to 4000 cm-1 using a Fourier-transform spectrometer. The thicknesses of the 4H-SiC epilayers and the electrical properties, including the free-carrier concentrations and the mobilities of both the 4H SiC substrates and the epilayers, are characterized through full line-shape fitting analyses. The correlations of the theoretical spectral profiles with the 4H-SiC electrical properties in the 30 cm-1-4000 cm 1 and 400 cm-1-4000 cm-1 spectral regions are established by introducing a parameter defined as error quadratic sum. It is indicated that their correlations become stronger at a higher carrier concentration and in a wider spectral region （30 cm-1-4000 cm-1）. These results suggest that the infrared reflectance technique can be used to accurately determine the thicknesses of the epilayers and the carrier concentrations, and the mobilities of both lightly and heavily doped 4H-SiC wafers.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2200103)the National Natural Science Foundation of China(Grant No.61474094)Principal Fund of Minnan Normal University(Grant No.KJ2020006).
文摘A near-infrared germanium(Ge)Schottky photodetector(PD)with an ultrathin silicon(Si)barrier enhancement layer between the indium-doped tin oxide(ITO)electrode and Ge epilayer on Si or silicon-on-insulator(SOI)is proposed and fabricated.The well-behaved ITO/Si cap/Ge Schottky junctions without intentional doping process for the Ge epilayer are formed on the Si and SOI substrates.The Si-and SOI-based ITO/Si cap/Ge Schottky PDs exhibit low dark current densities of 33 mA/cm2 and 44 mA/cm2,respectively.Benefited from the high transmissivity of ITO electrode and the reflectivity of SOI substrate,an optical responsivity of 0.19 A/W at 1550 nm wavelength is obtained for the SOI-based ITO/Si cap/Ge Schottky PD.These complementary metal–oxide–semiconductor(CMOS)compatible Si(or SOI)-based ITO/Si cap/Ge Schottky PDs are quite useful for detecting near-infrared wavelengths with high efficiency.
