A study on fast photo-response characteristics in amorphous semiconductors

本研究的目的是获得硫系非晶态半导体基本物理性质的统一图景。这项研究主要基于成分和压力诱导效应的实验结果。对光诱导现象也进行了广泛的研究。通过本工作取得的成果可以概括如下：第一，证实了对中期结构有序性的新认识。从共价键的平均配位数Z可以推断，随着Z从2增加到4，结构从一维链状结构转变为三维连通网络。在这两个极值之间，在Z=2.7时存在二维结构。其次，对光变暗现象的机理进行了定量描述。这种现象的产生归因于硫族原子的光致扭转运动。分析了光变暗的光强依赖关系，预测光变暗的大小可以提高到通常观测值的两倍。这两种对硫系玻璃不同方面的研究将结合起来研究光结构的转变。

A purpose of the present study is to obtain a unified picture of fundamental physical properties in chalcogenide amorphous semiconductors. The study is mainly based on experimental results of compositional and pressure-induced effects. Photoinduced phenomena are also investigated extensively. The results obtained through the present work can be summarized as follows.First, new insights regarding the medium-range structural order have been confirmed. The structure, which can be inferred from the average coordination number Z of covalent bonding, changes from the one-dimensional chain structure to the three-dimensionally connected networks with an increase in Z from 2 to 4. Between these extrema, there exists the two-dimensional structure at around Z = 2.7.Second, a quantitative description for the mechanism of the photodarkening phenomenon has been given. The origin is ascribed to photoinduced twisting motions of chalcogen atoms. Light-intensity dependence of the photodarkening is analysed, and it is predicted that the magnitude of the photodarkening can be enhanced to twice the commonly-observed value.These two kinds of studies on the different aspects of chalcogenide glasses will be connected for investigating the photostructural transformations.