Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/AlxGa1-xN strained quantum do...Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/AlxGa1-xN strained quantum dot, including the strong built- in electric field effect due to the spontaneous and piezoelectric polarization. The results show that the binding energy of impurity decreases when the strain is considered. Then the built-in electric field becomes bigger with the Al content increasing and the bin...展开更多
CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are stu...CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the CaN layers are strongly dependent on the difference of the Al composition between AlxCa1-xN barriers and AlyCa1-yN wells in the SLs. With a large Al composition difference, the CaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the CaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained CaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1-xN/AlyGal-yN SL buffer layer is a promising buffer structure for growing thick CaN films on Si substrates without crack generation.展开更多
Surface photovoltage spectroscopy equations for cathode materials with an AlxGa1-xAs buffer layer are determined in order to effectively measure the body parameters for transmission-mode （t-mode） photocathode materi...Surface photovoltage spectroscopy equations for cathode materials with an AlxGa1-xAs buffer layer are determined in order to effectively measure the body parameters for transmission-mode （t-mode） photocathode materials before Cs-O activation. Body parameters of cathode materials are well fitted through experiments and fitting calculations for the designed AlxGa1-xAs/GaAs structure material. This investigation examines photo-excited performance and measurements of body parameters for t-mode cathode materials of different doping structures. It also helps study various doping structures and optimize structure designs in the future.展开更多
We report an AlGaN channel high electron mobility transistor （HEMT） on a sapphire substrate with a 1000-nm A1xGa1-xN （x = 0-0.18）/GaN composite buffer layer, With a significant improvement of crystal quality, the ...We report an AlGaN channel high electron mobility transistor （HEMT） on a sapphire substrate with a 1000-nm A1xGa1-xN （x = 0-0.18）/GaN composite buffer layer, With a significant improvement of crystal quality, the device features a high product orris. #n. The AIGaN channel HEMTs presented show improved performance with respect to the conventional AIGaN channel HEMTs, including the on-resistance reduced from 31.2 to 8.1 Ω.mm, saturation drain current at 2 V gate bias promoted from 218 to 540 mA/mm, peak transconductance at 10 V drain bias promoted from 100 to a state-of-the-art value of 174 mS/ram, and reverse gate leakage current reduced from 1.85 × 10-3 to 2.15 × 10-5 mA/mm at VOD = -20 V.展开更多
Single quantum wells(SQWs)of GaAs/Al_xGa_(1-x)As have been investigated as photoelectrodes in photoelectrochemical cells.Structured photocurrent spectra for well widths of 50 and 100 SQWs were obtained in nonaqueous s...Single quantum wells(SQWs)of GaAs/Al_xGa_(1-x)As have been investigated as photoelectrodes in photoelectrochemical cells.Structured photocurrent spectra for well widths of 50 and 100 SQWs were obtained in nonaqueous solution.The dependence of structured photocurrent spectra on electrode potential were exhibited.The quantum yield was higher in SQW with 100 well compared to 50 well.展开更多
基金supported by the National Natural ScienceFoundation of China (No. 10564003)the Key Project of theScience and Technology Research of the Educational Ministry ofChina (No. 208025)
文摘Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/AlxGa1-xN strained quantum dot, including the strong built- in electric field effect due to the spontaneous and piezoelectric polarization. The results show that the binding energy of impurity decreases when the strain is considered. Then the built-in electric field becomes bigger with the Al content increasing and the bin...
基金Supported by the National Natural Science Foundation of China under Grant Nos 61076120 and 61106130the Natural Science Foundation and Scientific Support Plan of Jiangsu Province under Grant Nos BK2012516,BK20131072,and BE2012007
文摘CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the CaN layers are strongly dependent on the difference of the Al composition between AlxCa1-xN barriers and AlyCa1-yN wells in the SLs. With a large Al composition difference, the CaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the CaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained CaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1-xN/AlyGal-yN SL buffer layer is a promising buffer structure for growing thick CaN films on Si substrates without crack generation.
基金supported by the General Administra-tion for Quality Supervision of China(No.2008QK328)the Zhejiang Provincial Natural Science Foundation of China(No.Y5090150)
文摘Surface photovoltage spectroscopy equations for cathode materials with an AlxGa1-xAs buffer layer are determined in order to effectively measure the body parameters for transmission-mode （t-mode） photocathode materials before Cs-O activation. Body parameters of cathode materials are well fitted through experiments and fitting calculations for the designed AlxGa1-xAs/GaAs structure material. This investigation examines photo-excited performance and measurements of body parameters for t-mode cathode materials of different doping structures. It also helps study various doping structures and optimize structure designs in the future.
基金Supported by the National Science and Technology Major Project of China under Grant No 2013ZX02308-002National Natural Science Foundation of China under Grant Nos 11435010 and 61474086
文摘We report an AlGaN channel high electron mobility transistor （HEMT） on a sapphire substrate with a 1000-nm A1xGa1-xN （x = 0-0.18）/GaN composite buffer layer, With a significant improvement of crystal quality, the device features a high product orris. #n. The AIGaN channel HEMTs presented show improved performance with respect to the conventional AIGaN channel HEMTs, including the on-resistance reduced from 31.2 to 8.1 Ω.mm, saturation drain current at 2 V gate bias promoted from 218 to 540 mA/mm, peak transconductance at 10 V drain bias promoted from 100 to a state-of-the-art value of 174 mS/ram, and reverse gate leakage current reduced from 1.85 × 10-3 to 2.15 × 10-5 mA/mm at VOD = -20 V.
基金This work was supported by the National Natural Science Foundation of China.
文摘Single quantum wells(SQWs)of GaAs/Al_xGa_(1-x)As have been investigated as photoelectrodes in photoelectrochemical cells.Structured photocurrent spectra for well widths of 50 and 100 SQWs were obtained in nonaqueous solution.The dependence of structured photocurrent spectra on electrode potential were exhibited.The quantum yield was higher in SQW with 100 well compared to 50 well.
