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131.
Defects created by a dc hydrogen plasma have been compared to those observed in n-GaAs exposed to an inductively coupled (ICP) Ar plasma. The reference sample (in the case of H-plasma treated material) contained two prominent native deep level electron traps, possibly M4 and EC−0.56 eV, which were both passivated by hydrogen. Plasma treatment also resulted in the formation of a defect observed at 0.58 eV (M3) below the conduction band. This defect transforms back into what is believed to be M4 when annealed at 350 K for 3 h under reverse bias. These two defects compare well with two similar defects observed in the Ar ICP treated samples also showing metastable behavior. Additionally, the electrical characterization of Schottky barrier diodes on n-GaAs, prior to and after hydrogen passivation shows that, depending on the plasma conditions, the plasma ions significantly damage the surface resulting in poor rectifying contacts. The damage is considerably reversed/repaired upon annealing between the room temperature and 573 K (300 °C). 相似文献
132.
Comparative research on the transmission-mode GaAs photocathodes of exponential-doping structures
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Early research has shown that the varied doping structures of the active layer of GaAs photocathodes have been proven to have a higher quantum efficiency than uniform doping structures.On the basis of our early research on the surface photovoltage of GaAs photocathodes,and comparative research before and after activation of reflection-mode GaAs photocathodes,we further the comparative research on transmission-mode GaAs photocathodes.An exponential doping structure is the typical varied doping structure that can form a uniform electric field in the active layer.By solving the one-dimensional diffusion equation for no equilibrium minority carriers of transmission-mode GaAs photocathodes of the exponential doping structure,we can obtain the equations for the surface photovoltage(SPV) curve before activation and the spectral response curve(SRC) after activation.Through experiments and fitting calculations for the designed material,the body-material parameters can be well fitted by the SPV before activation,and proven by the fitting calculation for SRC after activation.Through the comparative research before and after activation,the average surface escape probability(SEP) can also be well fitted.This comparative research method can measure the body parameters and the value of SEP for the transmission-mode GaAs photocathode more exactly than the early method,which only measures the body parameters by SRC after activation.It can also help us to deeply study and exactly measure the parameters of the varied doping structures for transmission-mode GaAs photocathodes,and optimize the Cs-O activation technique in the future. 相似文献
133.
不同变掺杂结构GaAs光电阴极的光谱特性分析 总被引:1,自引:0,他引:1
为定量研究变掺杂结构对阴极量子效率的作用效果,设计生长了两种不同掺杂方式的反射式梯度掺杂GaAs光电阴极,激活后测量了两者的光谱响应曲线。将光谱响应曲线转换为对应的量子效率曲线,对不同入射光波段的量子效率进行了拟合分析,得到了体现变掺杂结构贡献程度的变掺杂系数K值。研究发现,同一阴极材料对不同波段的入射光,其掺杂结构产生的作用效果各不相同。同时,不同掺杂结构光电阴极对于相同波段范围内的入射光,其作用效果也不相同。产生这些差别的根本原因,是由于不同掺杂结构下,材料中内建电场的位置和强度不同而造成的。该研究为评判不同掺杂方式下光电阴极的结构性能提供了有效的分析手段,对研究阴极变掺杂结构的优化设计具有非常重要的应用价值。 相似文献
134.
135.
Ping Li Qingpu Wang Xingyu Zhang Yurong Wang Shichen Li He Jingliang Lu Xingqiang 《Optics & Laser Technology》2001,33(6)
A diode-pumped Nd:YVO4 laser passively Q switched with GaAs is studied theoretically and experimentally. We have demonstrated the influence of single-photon absorption, two-photon absorption and free-carrier absorption in GaAs on the Q-switched pulse characteristics. The pulse profile, pulse energy and pulse width of the Q switching with GaAs are simulated by using the conventional rate equations of the four-level laser system. The experimental results show reasonable agreement with the theoretical results on the whole. 相似文献
136.
Fanyao Qu N. O. Dantas P. C. Morais 《Physica E: Low-dimensional Systems and Nanostructures》2001,9(4):709
The investigation of the evolution of the photoluminescence spectra, in single asymmetric quantum wells (SAQWs), from a typical emission spectrum to a Fermi-edge singularity, is carried out as a function of both the optical excitation intensity and the temperature. The three samples used here are n-doped, low carrier density (below 5×1011 cm−2), GaAs/Al0.35Ga0.65As SAQWs grown by molecular beam epitaxy. The strong collective recombination of electrons with different k states up to the Fermi wave vector as well as the optical signature of the Fermi-edge singularity is observed in two samples containing residual acceptors inside the GaAs SAQW. In contrast, a third sample containing no experimental evidence of residual acceptors in the GaAs SAQW shows no optical signature of the Fermi-edge singularity. 相似文献
137.
H. Chen Z. Q. Li H. F. Liu L. Wan M. H. Zhang Q. Huang J. M. Zhou Y. Luo Y. J. Han K. Tao N. Yang 《Journal of Crystal Growth》2000,210(4):811-814
Two kinds of GaN samples were grown on GaAs(0 0 1) substrates. One is grown on nitridized GaAs surface, the other is grown on nitridized AlAs buffer GaAs substrate. X-ray diffraction and photoluminescence measurements find that the GaN sample directly grown on GaAs substrate is pure cubic phase and those grown on AlAs buffer is pure hexagonal phase. The present study shows that the phase of GaN samples grown on GaAs substrates can be controlled using different buffer layers. 相似文献
138.
X. Z. Wang D. H. Zhang H. Q. Zheng S. F. Yoon C. H. Kam W. Shi A. Raman 《Journal of Crystal Growth》2000,210(4):458-462
We report the growth and characterization of GaInAsP films on GaAs substrates by solid source molecular beam epitaxy (SSMBE) using a valve phosphorous cracker cell at varied white phosphorous beam equivalent pressure (BEP). It is found that the GaInAsP/GaAs can be easily grown with the solid sources, and the incorporated phosphorous composition as a function of the beam equivalent pressure ratio, R=fP/(fP+fAs), can be well described by a parabolic relationship. With the increase of the incorporated phosphorous composition, the GaP-, InP-, InAs- and GaAs-like phonon modes shift towards opposite directions and their emission intensities also change. The first three modes shift to larger wave numbers while the last one shifts to smaller wave number. The lattice mismatch, Δa/a, of the materials grown with varied phosphorous BEP follows a linear relationship. Photoluminescence (PL) measurements reveal that as the phosphorous BEP ratio increases, the peak position or energy band gap of the material shifts towards higher energy; the full-width at half-maximum (FWHM) becomes narrower, and the luminescence intensity becomes higher. In addition, the materials also show smooth surfaces that do not change significantly with phosphorous beam equivalent pressure. 相似文献
139.
In this paper we show a detailed AFM observation of GaAs epilayers grown on GaAs (0 0 1) substrate patterned with SiO2 mask by low angle incidence microchannel epitaxy (LAIMCE). We have found that low index facets are formed as sidewalls of the epilayers grown in open window aligned along singular directions. We have also found that low index facets are formed as sidewalls for epilayers showing a zigzagging edge. In the case of the epilayers grown in an open window aligned 10° off [0 1 0], for which lateral growth is maximum, we have found round shape sidewalls and (0 0 1) terraces at the boundary of the sidewall and the top surface. We concluded that the lateral growth proceeds when the sidewall is rough, while it stops when low index facets are formed as sidewalls. 相似文献
140.
本文探讨了具有缓冲功能的三值 GaAs电路的基本结构 ,特别是对三值 GaAs逻辑输出级电路 进行了讨论 ,提出了 2种三值 GaAs电路的逻辑级电路的结构 ,经过 PSPICE程序的模拟 ,选取了较理想 的一种电路结构 ,并由此建立了对应的开关模型. 根据该模型提出了适用于三值 GaAs在开关元件级的 电路设计方法 . 相似文献