Photoconductivity of Quasicrystalline Alloys : Electronic Structure Investigation as a Semiconductor

准晶合金的光电导性:作为半导体的电子结构研究

基本信息

批准号：
09450232
负责人：
KIMURA Kaoru
金额：
$ 9.02万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Modulated photocurrent measurements, originally developed for analyzing the electronic states of semiconductors have been performed on an Al-Pd-Re quasicrystal having high electrical resistivity using two kinds of Lasers with different excitation energies. No noticeable difference has been found in the phase shift between the two excitation energies. The data of the amplitude and phase shift of modulated photocurrent can be explained well by a simple model in which only the two processes, carrier generation and recombination, are involved. The recombination time is by about six orders larger than those reported for conventional semiconductors. The results obtained are discussed in terms of electron density of states and energy dependence of carrier mobility.The modulated photocurrent method has been applied to pure and vanadium (V) doped β-rhombohedral boron (β-B), aiming at investigating the difference in the distribution of electronic states in the band gap between them. Excitation light intensity dependence of the amplitude and phase shift of photocurrent shows that V-doped β-B has a much larger trapping states density for photoexcited carriers than pure β-B.With increasing temperature, the amplitude increases and decreases for pure and V-doped β-B, respectively, indicating that the conduction mechanism for photo-excited carrier is completely different between the two samples. The unusual negative temperature dependence for V-doped β-B is similar to that for Al-Pd-Re quasicrystal and the change of dependence from positive to negative is consistent with the approach to aluminum-based icosahedral quasicrystals in atomic structure and in transport properties by V-doping to β-B.The modulated frequency dependence of the amplitude and phase shift cannot be explained by the usual photoconduction processes, which are indicating that the gap states distribution and photoconduction processes in these materials are complicated.

最初为分析半导体电子态而开发的调制光电流测量已在具有高电阻率的 Al-Pd-Re 准晶体上使用两种具有不同激发能量的激光器进行，未发现两种激光器之间的相移存在明显差异。调制光电流的幅度和相移数据可以通过一个简单的模型很好地解释，其中仅涉及载流子生成和复合两个过程，复合时间比该模型大大约六个数量级。所获得的结果从电子态密度和载流子迁移率的能量依赖性方面进行了讨论。调制光电流方法已应用于纯和钒 (V) 掺杂的 β-菱面体硼 (β-B)，旨在研究它们之间带隙中电子态分布的差异对光电流振幅和相移的激发光强度的依赖性，结果表明V掺杂的β-B具有更大的光激发俘获态密度。随着温度的升高，纯β-B和V掺杂β-B的振幅分别增大和减小，表明两种样品之间光激发载流子的传导机制完全不同。 V 掺杂 β-B 的依赖性与 Al-Pd-Re 准晶的依赖性相似，并且依赖性从正到负的变化与原子中铝基二十面体准晶的方法一致。 V-掺杂到β-B会影响结构和输运特性。振幅和相移的调制频率依赖性不能用通常的光电导过程来解释，这表明这些材料中的能隙态分布和光电导过程是复杂的。