The effect of a self-organized SiNs interlayer on the defect density of （1122） semipolar GaN grown on 7n-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-r...The effect of a self-organized SiNs interlayer on the defect density of （1122） semipolar GaN grown on 7n-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-ray diffrac- tion. The SiNx interlayer reduces the c-type dislocation density from 2.5 ×10^10 cm^-2 to 5 ×10^8 cm 2. The SiNx interlayer produces regions that are free from basal plane stacking faults （BSFs） and dislocations. The overall BSF density is reduced from 2.1×10^5 cm-1 to 1.3×10^4 cm^-1. The large dislocations and BSF reduction in semipolar （1122） GaN with the SiNx, interlayer result from two primary mechanisms. The first mechanism is the direct dislocation blocking by the SiNx interlayer, and the second mechanism is associated with the unique structure character of （1122） semipolar GaN.展开更多
本文分析了在不同衬底上生长无极性GaN薄膜的情况,这些衬底主要包括-γL iA lO2、r面蓝宝石等。通常在蓝宝石上制备的GaN外延膜是沿c轴生长的,而c轴是GaN的极性轴,导致GaN基器件有源层量子阱中出现很强的内建电场,发光效率会因此降低,...本文分析了在不同衬底上生长无极性GaN薄膜的情况,这些衬底主要包括-γL iA lO2、r面蓝宝石等。通常在蓝宝石上制备的GaN外延膜是沿c轴生长的,而c轴是GaN的极性轴,导致GaN基器件有源层量子阱中出现很强的内建电场,发光效率会因此降低,发展非极性面外延,有望克服这一物理现象,使发光效率提高。展开更多
LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluo...LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti： LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively： The peaks at 716nm and 798nm may stem from the VLi^＋ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4＋-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.展开更多
Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions （x = 0, 0.05, 0.10, 0.15） by analyzing the relative oscillator strength （ROS） and en...Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions （x = 0, 0.05, 0.10, 0.15） by analyzing the relative oscillator strength （ROS） and energy level splitting of the three transitions related to the top three valence bands （VBs）. The ROS was calculated by applying the effective-mass Hamiltonian based on k .p perturbation theory. For c-plane InxGa1-xN, it was found that the ROS of 〈X〉 and 〈Y〉-like states were superposed with each other. Especially, under compressive strain, they dominated in the top VB whose energy level also went up with strain, while the ROS of the ｜Z〉-like state decreased in the second band. For m-plane InxGa1-xN under compressive strain, the top three VBs were dominated by 〈X〉, 〈Z〉, and 〈Y〉-like states, respectively, which led to nearly linearly-polarized light emissions. For the top VB, ROS difference between [X） and [Z）-like states became larger with compressive strain. It was also found that such tendencies were more evident in layers with higher In compositions. As a result, there would be more TE modes in total emissions from both c-plane and m-plane InGaN with compressive strain and In content, leading to a larger polarization degree. Experimental results of luminescence from InGaN/GaN quantum wells （QWs） showed good coincidence with our calculations.展开更多
This paper reports that the m-plane GaN layer is grown on （200）-plane LiAlO2 substrate by metal-organic chemical wpour deposition （MOCVD） method. Tetragonal-shaped crystallites appear at the smooth surface. Raman ...This paper reports that the m-plane GaN layer is grown on （200）-plane LiAlO2 substrate by metal-organic chemical wpour deposition （MOCVD） method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer＇s thickness. The high transmittance （80%）, sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at -3.41 eV with full-width at half maximum of 120 meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO2 substrate.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61204006 and 61574108the Fundamental Research Funds for the Central Universities under Grant No JB141101the Foundation of Key Laboratory of Nanodevices and Applications of Suzhou Institute of Nano-Tech and Nano-Bionics of Chinese Academy of Sciences under Grant No 15CS01
文摘The effect of a self-organized SiNs interlayer on the defect density of （1122） semipolar GaN grown on 7n-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-ray diffrac- tion. The SiNx interlayer reduces the c-type dislocation density from 2.5 ×10^10 cm^-2 to 5 ×10^8 cm 2. The SiNx interlayer produces regions that are free from basal plane stacking faults （BSFs） and dislocations. The overall BSF density is reduced from 2.1×10^5 cm-1 to 1.3×10^4 cm^-1. The large dislocations and BSF reduction in semipolar （1122） GaN with the SiNx, interlayer result from two primary mechanisms. The first mechanism is the direct dislocation blocking by the SiNx interlayer, and the second mechanism is associated with the unique structure character of （1122） semipolar GaN.
文摘本文分析了在不同衬底上生长无极性GaN薄膜的情况,这些衬底主要包括-γL iA lO2、r面蓝宝石等。通常在蓝宝石上制备的GaN外延膜是沿c轴生长的,而c轴是GaN的极性轴,导致GaN基器件有源层量子阱中出现很强的内建电场,发光效率会因此降低,发展非极性面外延,有望克服这一物理现象,使发光效率提高。
文摘LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti： LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively： The peaks at 716nm and 798nm may stem from the VLi^＋ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4＋-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60676032,60577030 and 60776042)National Key Basic Research Special Foundation of China (Grant No TG 2007CB307004)
文摘Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions （x = 0, 0.05, 0.10, 0.15） by analyzing the relative oscillator strength （ROS） and energy level splitting of the three transitions related to the top three valence bands （VBs）. The ROS was calculated by applying the effective-mass Hamiltonian based on k .p perturbation theory. For c-plane InxGa1-xN, it was found that the ROS of 〈X〉 and 〈Y〉-like states were superposed with each other. Especially, under compressive strain, they dominated in the top VB whose energy level also went up with strain, while the ROS of the ｜Z〉-like state decreased in the second band. For m-plane InxGa1-xN under compressive strain, the top three VBs were dominated by 〈X〉, 〈Z〉, and 〈Y〉-like states, respectively, which led to nearly linearly-polarized light emissions. For the top VB, ROS difference between [X） and [Z）-like states became larger with compressive strain. It was also found that such tendencies were more evident in layers with higher In compositions. As a result, there would be more TE modes in total emissions from both c-plane and m-plane InGaN with compressive strain and In content, leading to a larger polarization degree. Experimental results of luminescence from InGaN/GaN quantum wells （QWs） showed good coincidence with our calculations.
文摘This paper reports that the m-plane GaN layer is grown on （200）-plane LiAlO2 substrate by metal-organic chemical wpour deposition （MOCVD） method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer＇s thickness. The high transmittance （80%）, sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at -3.41 eV with full-width at half maximum of 120 meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO2 substrate.
