针对高应变InGaAs/GaAs多量子阱中存在的局域态问题,利用金属有机化合物气相外延(MOCVD)技术,设计并生长了五周期的In_(0.3)Ga_(0.7)As/GaAs高应变多量子阱材料。通过原子力显微镜(Atomic force microscope,AFM)和变温光致发光(Photolum...针对高应变InGaAs/GaAs多量子阱中存在的局域态问题,利用金属有机化合物气相外延(MOCVD)技术,设计并生长了五周期的In_(0.3)Ga_(0.7)As/GaAs高应变多量子阱材料。通过原子力显微镜(Atomic force microscope,AFM)和变温光致发光(Photoluminescence,PL)测试,发现量子阱内部存在缺陷及组分波动的材料无序性表现,验证了多量子阱内部局域态的存在及起源。同时发现在不同测试位置,局域态在低温下对光谱的影响也不同,分别表现为双峰分布和峰位“S”型变化。这进一步说明材料内部无序化程度不同,导致局域态的深度也不同。依据温度-带隙关系的拟合,提出了包含局域态的多量子阱材料的电势分布,并揭示了局域态载流子和自由载流子的复合机制。并且借助变功率PL测试,研究了在不同激发功率密度下不同深度的局域态的发光特性。展开更多
Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition（MOCVD） technique is a promising process for high-temperature supercon...Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition（MOCVD） technique is a promising process for high-temperature superconductor YBa;Cu;O;（YBCO） preparation.In this technique,the evaporation characteristics and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film.In the present report,bis（2,2,6,6-tetramethyl-3,5-heptanedionato）copper（II）(Cu（TMHD）;) was synthesized by the interaction of copper acetate hydrate with TMHD in methanol solution,and its structure was identified by FTIR,1 H NMR,and EI-MS spectroscopy.Subsequently,thermal property and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods（TGA） at different heating rates in streams of N;,and the average apparent activation energy of evaporation process was evaluated by the Ozawa,Kissinger,and Friedman methods.The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 85.1 kJ·mol;.展开更多
In this work, a hetero-epitaxial Al0.49In0.51As/Ga0.47In0.53 As metamorphic high electron mobility transistor(mHEMT) grown by metal–organic chemical vapor deposition(MOCVD) on p-type silicon substrate has been succes...In this work, a hetero-epitaxial Al0.49In0.51As/Ga0.47In0.53 As metamorphic high electron mobility transistor(mHEMT) grown by metal–organic chemical vapor deposition(MOCVD) on p-type silicon substrate has been successfully demonstrated. A novel AlGaAs/Al As period multiple quantum well(MQW) composite buffer scheme is developed to effectively tune the leakage current from the buffer layer. The quantized room-temperature Hall mobility of the twodimensional electron gas(2DEG) is larger than 7800 cm2/V·s, with an average sheet carrier density of 4.6×1012cm-2.Two-stage electron beam(EB) lithography technology by a JBX-6300 e-beam lithography system is developed to realize a 0.13-μm m HEMT device on Si substrate. A maximum transconductance Gm of up to 854 mS/mm is achieved, and is comparable to that of m HEMT technology on Ga As substrate with the same dimension. The fTand fmax are 135 GHz and120 GHz, respectively.展开更多
The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high temperature superconductor YBa2Cu3O7-δ （YBCO） preparation. In this technique, the purity, evaporation characteristics ...The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high temperature superconductor YBa2Cu3O7-δ （YBCO） preparation. In this technique, the purity, evaporation characteristics and thermostability of adopted precursors will de- cide the quality and reproducible results of YBCO film. In the present report, tris（2,2,6,6-tetramethyl-3,5-heptanedionato）yttrium（III） （Y（TMHD）3） was synthesized by the interaction of yttrium nitrate hydrate with TMHD in methanol solution, and its structure was identified by FTIR, 1H NMR, 13C NMR and EI-MS spectroscopy. Subsequently, the thermal property and the kinetics of decomposition were system- atically investigated by non-isothermal thermogravimetric analysis methods （TGA） at different heating rates in streams of N2, and the average apparent activation energy of evaporation process was evaluated by the Ozawa, Kissinger and Friedman methods. The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 88.9 kJ/mol.展开更多
To enhance light extraction effciency, high-quality InGaN-based light emitting diodes (LED) was grown on cone-shaped patterned sapphire (CPSS) by using metal organic chemical vapor deposition (MOCVD). From the transmi...To enhance light extraction effciency, high-quality InGaN-based light emitting diodes (LED) was grown on cone-shaped patterned sapphire (CPSS) by using metal organic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) observation, the CPSS was confirmed to be an efficient way to reduce the threading dislocation density in the GaN epilayer. A sharp and high intensity Photoluminescence (PL) for LED on CPSS at 457 nm compared to LED on unpattern planar sapphire substrates (USS) indicates that the crystalline quality was improved significantly and the internal reflection on the cones of the substrate was enhanced. The output power of the LED on CPSS is higher than that of LED on USS. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the CPSS.展开更多
Four-junction A1GaAs/GaAs laser power converters （LPCs） with n＋-GaAs/p＋-A10.37Ga0.63As hetero- structure tunnel junctions （TJs） have been designed and grown by metal-organic chemical vapor deposition （MOCVD） f...Four-junction A1GaAs/GaAs laser power converters （LPCs） with n＋-GaAs/p＋-A10.37Ga0.63As hetero- structure tunnel junctions （TJs） have been designed and grown by metal-organic chemical vapor deposition （MOCVD） for converting the power of 808 nm lasers. A maximum conversion efficiency ηc of 56.9% ＋ 4% is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W, while dropping to 43.3% at 1.5 W. Measured current-voltage （I-V） characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC.展开更多
ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three...ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.展开更多
Growth of cadmium sulfide （CdS） thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition （AP-MOCVD） using Cd（S2CNEt2）2 as the single precursor. Changes in th...Growth of cadmium sulfide （CdS） thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition （AP-MOCVD） using Cd（S2CNEt2）2 as the single precursor. Changes in the surface morphology of the deposited CdS thin films were investigated by atomic force microscope （AFM） as the function of substrate temperature （Ts）, vaporizing temperature （Tv）, and Ar flow rate. With the increase of Tv, CdS thin films evolved from pyramidal structure with fine grains to columnar structure with large grains. X-ray diffraction （XRD） patterns indicated that the CdS films had random orientation at the lower Tv and preferred orientation at the higher Tv. In addition, Ts had a great effect on the surface roughness of the CdS films, and a quantum dot-like structural CdS films were obtained in a narrow range of Ts with high Ar flow rate. Furthermore, the optical properties of the CdS films were measured using ultraviolet-visible （UV/VIS） spectrometer.展开更多
文摘针对高应变InGaAs/GaAs多量子阱中存在的局域态问题,利用金属有机化合物气相外延(MOCVD)技术,设计并生长了五周期的In_(0.3)Ga_(0.7)As/GaAs高应变多量子阱材料。通过原子力显微镜(Atomic force microscope,AFM)和变温光致发光(Photoluminescence,PL)测试,发现量子阱内部存在缺陷及组分波动的材料无序性表现,验证了多量子阱内部局域态的存在及起源。同时发现在不同测试位置,局域态在低温下对光谱的影响也不同,分别表现为双峰分布和峰位“S”型变化。这进一步说明材料内部无序化程度不同,导致局域态的深度也不同。依据温度-带隙关系的拟合,提出了包含局域态的多量子阱材料的电势分布,并揭示了局域态载流子和自由载流子的复合机制。并且借助变功率PL测试,研究了在不同激发功率密度下不同深度的局域态的发光特性。
基金supported by the Major State Basic Research Development Program of China (973 Program) (No.2011CBA00105)the National Natural Science Foundation of China (Nos. 51002149 and 21101151)
文摘Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition（MOCVD） technique is a promising process for high-temperature superconductor YBa;Cu;O;（YBCO） preparation.In this technique,the evaporation characteristics and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film.In the present report,bis（2,2,6,6-tetramethyl-3,5-heptanedionato）copper（II）(Cu（TMHD）;) was synthesized by the interaction of copper acetate hydrate with TMHD in methanol solution,and its structure was identified by FTIR,1 H NMR,and EI-MS spectroscopy.Subsequently,thermal property and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods（TGA） at different heating rates in streams of N;,and the average apparent activation energy of evaporation process was evaluated by the Ozawa,Kissinger,and Friedman methods.The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 85.1 kJ·mol;.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61401373)the Fundamental Research Funds for Central University,China(Grant Nos.XDJK2013B004 and 2362014XK13)the Chongqing Natural Science Foundation,China(Grant No.cstc2014jcyj A40038)
文摘In this work, a hetero-epitaxial Al0.49In0.51As/Ga0.47In0.53 As metamorphic high electron mobility transistor(mHEMT) grown by metal–organic chemical vapor deposition(MOCVD) on p-type silicon substrate has been successfully demonstrated. A novel AlGaAs/Al As period multiple quantum well(MQW) composite buffer scheme is developed to effectively tune the leakage current from the buffer layer. The quantized room-temperature Hall mobility of the twodimensional electron gas(2DEG) is larger than 7800 cm2/V·s, with an average sheet carrier density of 4.6×1012cm-2.Two-stage electron beam(EB) lithography technology by a JBX-6300 e-beam lithography system is developed to realize a 0.13-μm m HEMT device on Si substrate. A maximum transconductance Gm of up to 854 mS/mm is achieved, and is comparable to that of m HEMT technology on Ga As substrate with the same dimension. The fTand fmax are 135 GHz and120 GHz, respectively.
基金Project supported by Major State Basic Research Development Program of China (973 Program) (2011CBA00105)National Natural Science Foundation of China (51002149, 21101151)
文摘The metal-organic chemical vapor deposition （MOCVD） technique is a promising process for high temperature superconductor YBa2Cu3O7-δ （YBCO） preparation. In this technique, the purity, evaporation characteristics and thermostability of adopted precursors will de- cide the quality and reproducible results of YBCO film. In the present report, tris（2,2,6,6-tetramethyl-3,5-heptanedionato）yttrium（III） （Y（TMHD）3） was synthesized by the interaction of yttrium nitrate hydrate with TMHD in methanol solution, and its structure was identified by FTIR, 1H NMR, 13C NMR and EI-MS spectroscopy. Subsequently, the thermal property and the kinetics of decomposition were system- atically investigated by non-isothermal thermogravimetric analysis methods （TGA） at different heating rates in streams of N2, and the average apparent activation energy of evaporation process was evaluated by the Ozawa, Kissinger and Friedman methods. The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 88.9 kJ/mol.
文摘To enhance light extraction effciency, high-quality InGaN-based light emitting diodes (LED) was grown on cone-shaped patterned sapphire (CPSS) by using metal organic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) observation, the CPSS was confirmed to be an efficient way to reduce the threading dislocation density in the GaN epilayer. A sharp and high intensity Photoluminescence (PL) for LED on CPSS at 457 nm compared to LED on unpattern planar sapphire substrates (USS) indicates that the crystalline quality was improved significantly and the internal reflection on the cones of the substrate was enhanced. The output power of the LED on CPSS is higher than that of LED on USS. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the CPSS.
基金Project financially supported by the National Natural Science Foundation of China(No.61376065)Zhongtian Technology Group Co.Ltd
文摘Four-junction A1GaAs/GaAs laser power converters （LPCs） with n＋-GaAs/p＋-A10.37Ga0.63As hetero- structure tunnel junctions （TJs） have been designed and grown by metal-organic chemical vapor deposition （MOCVD） for converting the power of 808 nm lasers. A maximum conversion efficiency ηc of 56.9% ＋ 4% is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W, while dropping to 43.3% at 1.5 W. Measured current-voltage （I-V） characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC.
基金Supported by the National Natural Science Foundation of China(Nos. 20071013 and 20301007).
文摘ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.
基金supported by the Project of Key Technologies Research & Development Programme of Chengdu under Grant No.06GGYB512GX-030
文摘Growth of cadmium sulfide （CdS） thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition （AP-MOCVD） using Cd（S2CNEt2）2 as the single precursor. Changes in the surface morphology of the deposited CdS thin films were investigated by atomic force microscope （AFM） as the function of substrate temperature （Ts）, vaporizing temperature （Tv）, and Ar flow rate. With the increase of Tv, CdS thin films evolved from pyramidal structure with fine grains to columnar structure with large grains. X-ray diffraction （XRD） patterns indicated that the CdS films had random orientation at the lower Tv and preferred orientation at the higher Tv. In addition, Ts had a great effect on the surface roughness of the CdS films, and a quantum dot-like structural CdS films were obtained in a narrow range of Ts with high Ar flow rate. Furthermore, the optical properties of the CdS films were measured using ultraviolet-visible （UV/VIS） spectrometer.
