碲镉汞光导探测器掺杂表面层特性

把掺杂层对HgCdTe光导探测器表面的影响视为掺杂层电活性载流子与基底材料电活性载流子之比的函数关系,作了理论研究。结论是:在较薄层正面和背面作适当掺杂,可能提高光导探测器的响应率。     

Fe掺杂Hg_(1-x)Cd_xTe材料的光谱与电学研究

利用红外光谱、光致发光光谱与Hall测量等手段，对Fe掺杂Hg1-xCdxTe体单晶样品进行实验，研究了Fe在Hg1-xCdxTe中的杂质行为，发现Fe掺杂在Hg1－xCdxTe中引入一个位于导带底下方约80meV的施主能级，并且发现掺杂HgCdTe中的Fe元素在低于180K温度下基本上不表现出电活性，但它能够起非辐射复合中心的作用，影响材料的非平衡载流子寿命，在积分光致发光强度的温度变化关系中明显地反映出来．     

液相外延碲镉汞中砷离子注入与激活表征研究

As在HgCdTe材料中具有较小的扩散系数,可以形成较为稳定的结构,广泛应用于HgCdTe的p型掺杂。在p-on-n型碲镉汞红外探测器的制备中As掺杂是重要的制备方法。针对在制备过程中存在无法精确测量As激活率的问题,提出采用低温弱p型退火辅助差分霍尔测试的方法,获得了载流子浓度分布,从而通过与SIMS测试结果对比得到长、中波液相外延HgCdTe样品中As的激活率,并分析了退火等工艺对As掺杂后激活率的影响。     

HgCdTe晶体的本征载流子浓度的应用

HgCdTe晶体的本征激发决定于组份和温度。本征载流子浓度与组份、温度的关系早已得到广泛、深入的研究。由于自由载流子来源于杂质激发与本征激发,如果把杂质的影响考虑进去,就可以由本征载流子浓度推算出在高于77K的任何温度下的载流子浓度。反过来,如果知道处于本征激发占主导地位的某一温度时(如室温)的载流子浓度,就可以     

真空退火的CdTe/Au掺杂HgCdTe界面状态的影响

对使用CdTe覆盖的HgCdTe材料在不同温度下进行了一系列的退火实验.研究发现,退火可以改善电子束蒸发CdTe的晶体状态,使CdTe和HgCdTe之间的界面状态得到改善.Au掺杂HgCdTe覆盖CdTe后,真空条件下退火,240℃和300℃对Au掺杂的浓度分布改变不大,Au掺杂的浓度几乎不变.但是,温度的不同会对汞空位的浓度产生显著的影响,因此退火温度不同会使载流子浓度明显不同.退火温度从240℃升高至300℃后,霍尔测试得到的载流子浓度从2×10~(16)cm~(-3)左右升高至5.5×1016cm~(-3)左右.     

杂质和缺陷对非掺半绝缘LECGaAs霍耳测量的影响

研究了非掺杂半绝缘ＬＥＣ ＧａＡｓ霍耳参数温度关系，研究结果表明，杂 缺陷的不均匀分布引起的电势波动对霍耳测量结果有明显影响，存在电势波动的情况下，仅用霍耳测量不能测定真实的自由载流子浓度和费米能级位置。     

由透过率测量HgCdTe的导电类型载流子浓度及吸收截面

由自由载流子吸收下的样品透过率测量了HgCdTe导电类型、载流子浓度和吸收截面,该法属种非接触、无损伤测量,并能得到测量参数分布状况。这项工作是与光调制红外吸收技术测量HgCdTe少数载流子寿命同时完成的。我们有效地解决了用激光光源作为探针光     

富汞热处理对碲镉汞电学性能的影响

对液相外延方法(LPE)生长的碲镉汞(HgCdTe)材料进行了闭管富汞热处理,并研究了不同的热处理时间和热处理温度对碲镉汞材料电学性能的影响。HgCdTe材料经过富汞热处理后可以有效降低材料内的缺陷尺寸和密度。该方法不仅可以降低材料内的位错密度,而且还可以完成材料P型到N型的转变。工艺中的低温热处理对HgCdTe材料的电学性能有较大影响。研究发现,随着低温热处理时间的持续增加,HgCdTe材料的载流子浓度会明显增加。而当低温热处理温度在210℃~250℃范围内变化时,若保持低温热处理时间不变,则热处理后HgCdTe材料的载流子浓度在一定范围内波动,且无明显变化。通过对HgCdTe器件进行I-V曲线测试以及最终的组件测试,发现热处理后载流子浓度在1E13~1E14cm^-3范围内的HgCdTe芯片就可以得到很好的测试结果。     

分子束外延HgCdTe nBn结构红外探测器的理论计算和优化

通过2维数值模拟对HgCdTe nBn红外探测器的光电性质进行了研究.理论计算了nBn结构中各层的参数的变化(包含厚度的变化、掺杂浓度的变化以及组分)对器件性能的影响规律.通过优化上述器件结构参数,理论上获得了最优化结构的HgCdTe nBn器件,为获得高性能MBE外延HgCdTe nBn红外探测器提供重要参考.     

碲镉汞薄膜少子寿命测试研究

碲镉汞(HgCdTe)材料的少子寿命是影响碲镉汞红外探测器性能的重要参数。分别采用微波光电导衰减(Microwave Photoconductivity Decay, μ-PCD)法和微波探测光电导(Microwave Detected Photoconductivity, MDP)法对HgCdTe薄膜的少子寿命进行了研究。结果表明,随着激光功率的增强,样品的少子寿命降低;由于载流子复合机制的变化,HgCdTe薄膜的少子寿命随温度的增加有先增后减的趋势。通过HgCdTe薄膜少子寿命面分布可以得出样品不同区域的载流子浓度分布与均匀性。对于HgCdTe薄膜材料来说,以上两种测试结果的面分布状况相近。     

Finite-temperature effects in free-electron lasers

The effect of energy spread on the gain of a dense-beam free-electron laser amplifier is analyzed. The formalism includes collective effects and allows for the use of an arbitrary distribution function. The dispersion relation is solved numerically. Besides broadening of the spectrum and decrease in gain, lowering of the central emission frequency with energy spread is observed. An initial-value problem is formulated and numerically solved, with power computed as a function of distance. The relative contributions of the different modes when temperature changes are analyzed. In particular, the competing effects of a decrease in coupling loss with temperature together with Landau damping are investigated.     

Propagation and excitation of perturbations in electron beams with velocity shear

A theoretical investigation of the influence of a spatially varying drift velocity on the perturbations in magnetically focused electron beams is presented. The wave propagation on such beams, focused by infinite magnetic fields, is studied under the small-wave assumption. The dispersion relation for slow waves is derived and solved for different transversal boundary conditions. Two sets of infinitely many propagating modes are found in a beam with small velocity shear. In a beam with sufficiently large velocity shear only two eigenfunctions exist. Since it is not possible to match the two eigenfunctions on arbitrary longitudinal boundary conditions, additional solutions (which cannot be written in form of a plane wave) must exist. The excitation of perturbations by ideal grids is solved by introducing the Laplace transform analysis. Additional solutions are ascertained which lead to a spatial decay of the perturbations according to a power law z^-α. This damping, arising from the spatially varying drift velocity, is similar to the Landau damping in electron beams with velocity distribution. Such damping effects are of great practical importance in conjunction with noise reduction in traveling-wave tubes.     

HgCdTe反型层电子子能带物理

<正> 本文在4.2K下测定了p-HgCdTe MIS结构样品的量子电容谱,表面磁阻振荡,表面回旋共振以及表面电子自旋共振,确定了HgCdTe反型层电子子能带结构,包括能级位置、费米能级、有效质量、反型层耗尽层厚度等,并推导了由于自旋轨道相互作用而引起的电致自旋分裂子能带的色散关系和朗道能级扇形图,还研究了朗道能级以及自旋能级间的光跃迁问题。     

极性晶体中磁极化子声子色散效应

利用线性组合算符和幺正变换相结合的方法,研究了声子色散对极性晶体中磁极化子性质的影响．计及纵光学（LO）声子色散,在抛物近似下导出了极性晶体中磁极化子基态能量、自陷能和基态Landau能随声子色散系数、回旋共振频率和电子-纵光学声子耦合强度的变化关系．数值计算结果表明基态能量随声子色散系数、电子-纵光学声子耦合强度的增大而减小．自陷能随声子色散系数和电子-纵光学声子耦合强度的增大而增大．基态Landau能随电子-纵光学声子耦合强度的增大先增大到最大值后又减小,随声子色散系数的增大而增大．     

用吸收和反射谱的方法测定半磁半导体HgSe:Fe的重要参数(英文)

Infrared measurements have been performed on semimagnetic semiconductor HgSe:Fe with concentrations of iron from 2 ×1018cm-3 to 7×1019cm-3 in the wavelength region of 300 cm-1 to 2500 cm-1 and the temperature range from 11K to 300K, for the absorption spectra, and 300K, for the reflectivity spectra, respectively.Calculations of free carrier absorption coefficient and reflectivity based on Drude theory have also been carried out.It was found that the calculated values of both absorption coefficient and reflectivity agree very well with the measured values. This proves that Drude theory can be used to explain the free-carriers absorption and reflectivity of HgSe:Fe. Thus, the parameters of material, such as plasma frequecy, high frequency dielectric constant and damping constant, can be then obtained from the fitting of theory to experiment. Furthermore, two other physical parameters, i.e. the concentration of free carriers and effective mass averaged over energy band, can be evaluated.     

Hg1—xCdxTe表面电子的子能带结构

讨论了Hg_(1-x)Cd_xTe MIS结构N型反型层电子子能带结构的理论和实验研究结果。描述了采用电容-电压谱,回旋共振谱和磁导振荡谱定量地研究电子子能带结构的模型和方法。推导得到的子能带色散关系,朗道能级和有效g~*因子,与测得的子能带电子的回旋共振和自旋共振结果符合得很好,从而可以定量地研究由于表面电子的自旋轨道相互作用引起的零场分裂效应,朗道能级的移动、交叉,波函数的混合效应以及电致自旋分裂的色散关系。     

Waveguide Subsidiary Resonance Ferrite Limiters

This paper gives an analysis of E-plane waveguide ferrite limiters under subsidiary resonance conditions. Since Suhl's high-power damping term is power sensitive, it is necessary to evaluate it in every part of the ferrite structure before forming the dispersion relation. This is done in this paper by dividing the waveguide assembly in small elements transverse and parallel to the direction of propagation and calculating it in each region. The dispersion relation in each section along the direction of propagation is then formed in conjunction with the appropriate Suhl damping constant by establishing the transverse resonance condition. The total output power is obtained by forming the input/output relation for each section one at a time along the structure. The theory has been found useful in describing both the onset of limiting and the dynamic range of a ferrite limiter mounted on one of the narrow walls of the waveguide.     

Theory of Raman-mediated pulsed amplification in silicon-wire waveguides

We present a comprehensive theoretical study of pulsed stimulated Raman scattering in silicon wires. The pulse dynamics is described by a system of coupled equations, which describes intrinsic waveguide optical losses, phase shift and losses due to free-carriers (FCs) generated through two-photon absorption (TPA), first- and second-order frequency dispersion, self-phase and cross-phase modulation, TPA losses, and the interpulse Raman interaction. Furthermore, the influence of the FCs on the pulse dynamics is incorporated through a rate equation. The corresponding system of equations has then been numerically integrated, and phenomena such as noise-seeded Raman amplification, pulsed Raman amplification, and Raman-mediated pulse interaction have been described.     

平行磁场下半导体超晶格电子结构(英文)

Electron and hole subbands of superlattices in an in-plane magnetic field are investigated. Landau energy levels, subband dispersion curves and optical transition probabilities in GaAs-AlxGa1-xAs are calculated by using the effective mass theory. The variations of the binding energies of light and heavy hole excitoas as functions of quantum well width and magnetic field strength are obtained.Electronic energy levels in a magnetic field (in xy plane) with the tilting away from the growth direction (y axis) are calculated and discussed.     

The Problem of the Experimental Confirmation of Landau Damping†

The experimental confirmation of Landau damping in a one-dimensional plasma or electron beam requires the measurement of the velocity distribution, the wave amplitude as a function of time or space, and the numerical solution of the Volterra integral equation through which these data are theoretically related. It is shown that the errors inherent in the two measurements are, under the best of circumstances, of such magnitude that it is not possible to adduce a damping law. The analysis is devoted for the most part to the spatial damping on an electron beam, and a typical numerical example is given