FAR-INFRARED PHOTOCONDUCTIVITY MECHANISM ON SHALLOW IMPURITY IN GaAs

We report the far-infrared photoconductivity spectroscopy (FIRPCS) of the high purity n-GaAs grown by molecular beam epitaxial (MBE) technique. The current-voltage (I-V) measurement and FIRPCS under different electric field strength have been performed on high purity n-GaAs at 4.2K. Except for photothermal ionization process, a new far-infrared photoconductivity (FIRPC) mechanism is observed. This photo ionization process is assisted by impact ionization and depends on external electric field. This new mechanism originates from photo-field ionization.     

THE SCREENING EFFECT OF PHONON MODES IN HIGH-Tc OXIDE SUPERCONDUCTOR

This paper presents three different kinds of infrared (IR) spectra of oxide materials. The first one is the IR reflection spectra of Ti₂Ba₂Ca₂Cu₃O₁₀ superconducting film at the incident angles 7°, 12° and 30°. The second one is the IR spectra of nonsuperconducting ceramic materials YBa₂Cu₃O₆ and PrBa₂Cu₃O₇. The third one is the IR spectra of superconductor YBa₂Cu₃O_7-δ and of its film with the c-axis perpendicular to the film plane, as well as the changes in the spectra of these materials after annealing at different temperatures. It is found that in the spectra of high-T_c oxide superconductor, only the phonon modes along c-axis can be observed while the modes in a-b plane are absent. But in the spectra of nonsuperconductors the modes in a-b plane can be observed, particularly in the absorption spectra of the semiconductor YBa₂Cu₃O₆, all eleven allowed IR active modes have been detected. We suggest that the above experimental phenomena may result from the fact that the phonon modes vibrating in the a-b plane of the high-T_c oxide superconducting materials are almost screened by the free carriers which can move only in a-b plane.     

自伴向量型Sturm-Liouville问题特征值λn,r的依赖性*

研究定义在区间[a,b]上的m维自伴向量型Sturm-Liouville问题.首先, 利用矩阵Pr¨ufer变换讨论该问题特征值的分布, 同时得到第n组特征值λ_n,r(n ∈ N₀, r = 1, 2, · · · , m)所对应的特征函数u_n,r(x)在区间(a,b)内恰有n个零点.然后, 研究了特征值λ_n,r分别关于算子系数和边界条件的连续依赖性. 在此基础上, 假设所有特征值都是单重的,建立了第n组特征值λ_n,r (r = 1, 2, · · · , m)关于首项系数P^-1, 势矩阵Q, 权矩阵W的微分表达式,进而讨论特征值关于P^-1, Q, W的单调性. 最后, 如果允许特征值的指标可以跳跃,则任一特征值都可以嵌入到一个连续的特征值分支中,从而证明λ_n,r关于边界条件中的参数α和β的连续可微性.     

GaAs/Al1-xAs表面单量子阱原位光调制反射光谱研究

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Zn_(0.04)Cd_(0.96)Te中深能级的红外光电导谱研究

应用红外光电导谱研究半绝缘p型Zn0.04Cd0.96Te中的深能级,在温度从4.2到165K范围内,观察到了位于0.24,0.34,0.38,0.47,0.55和0.80eV处6个光电导响应峰.结合4.2K下光致发光谱的测量结果以及对ZnxCd1-xTe中深能级发光光谱、深能级瞬态谱等已有的研究结果,对这些响应峰对应的深能级特性进行了讨论.     

THE SCREENING EFFECT OF PHONON MODES IN HIGH-Tc OXIDE SUPERCONDUCTOR

This paper presents three different kinds of infrared (IR) spectra of oxide materials. The first one is the IR reflection spectra of Ti₂Ba₂Ca₂Cu₃O₁₀ superconducting film at the incident angles 7°, 12° and 30°. The second one is the IR spectra of nonsuperconducting ceramic materials YBa₂Cu₃O₆ and PrBa₂Cu₃O₇. The third one is the IR spectra of superconductor YBa₂Cu₃O_7-δ and of its film with the c-axis perpendicular to the film plane, as well as the changes in the spectra of these materials after annealing at different temperatures. It is found that in the spectra of high-T_c oxide superconductor, only the phonon modes along c-axis can be observed while the modes in a-b plane are absent. But in the spectra of nonsuperconductors the modes in a-b plane can be observed, particularly in the absorption spectra of the semiconductor YBa₂Cu₃O₆, all eleven allowed IR active modes have been detected. We suggest that the above experimental phenomena may result from the fact that the phonon modes vibrating in the a-b plane of the high-T_c oxide superconducting materials are almost screened by the free carriers which can move only in a-b plane.     

GaAs中与施主高激发态有关的共振极化子效应

报道了n型GaAs的杂质磁光电导谱．在相对低的磁场下观察到束缚电子高激发态与LO声子的共振相互作用；讨论了共振极化子光电导响应随磁场强度变化的行为，以及钉扎在LO声子能量处的光电导峰的物理起源     

外延Si1-xGex薄层中浅杂质的光热电离光谱

在Si_1-xGe_x合金外延层中利用光热电离光谱方法观察到了Si_0.92Ge_0.08合金中浅施主磷的2p_±及3p_±态的分立谱线，并根据有效质量近似理论估算了Si_0.92Ge_0.08合金中磷施主的电离能为45.51meV．与硅相比，由于合金的无序效应，Si_1-xGe_x合金的分立谱线发生明显展宽 关键词：