Theoretical Study of Bond-Fluctuation in Amorphous Semiconductors

非晶半导体键涨落的理论研究

• 批准号: 10640311
• 负责人: SHINOZUKA Yuzo
• 金额: $ 1.09万
• 依托单位: Wakayama University (1999)Yamaguchi University (1998)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640311/
• 关键词: amorphous semiconductor; structural randomness; metastable structure; s-p hybridization; optical absorption; Urbach rule; gap state; selection rule; アモルファス; s-p混成軌道

The electronic structure and optical properties of covalent amorphous semiconductors are theoretically studied with special attention to the s-p hybridization in electronic states and the spatial correlation in their mixing. One-dimensional tight binding model is used in which the inter-atomic transfer energy of an electron between nearest neighbor atoms depends linearly on their inter-atomic distance. All the electronic states are numerically calculated for a 150-atom system and the ensemble average is taken over 10 samples. Following results have been obtained.(1)As the degree of randomness increase, the degree of hybridization decreases and rearrangements in the covalent bonds take place.(2)The width of the band gap decreases but the gap remains rather long compared to a case where the spatial correlation is neglected.(3)There appears a characteristic peak in the optical absorption spectrum, which reflects central peaks in the partial (s- or p-) density of states in the valence and conduction bands and is related to an electron localization caused by the spatial correlation.Since we have used the one-dimensional model, the van Hove singularity appears remarkably at the band edges, and then we cannot directly compare the results with experiments on the absorption spectrum. However, rearrangements of the hybridization and the covalent bond are expected to take place also in three-dimension. This would be important in connection with the stability of so-called weak bond and dangling bond and their metamorphosis. Self-consistent calculations for the distribution of the interatomic distance and the local covalent bond in three-dimensional system are under progress in order to explain a universal value for the steepness parameter of the Urbach tails the absorption spectrum in various amorphous semiconductors.

本文从理论上研究了共价非晶半导体的电子结构和光学性质，特别是电子态的s-p杂化和它们混合时的空间相关性。采用一维紧束缚模型，电子在最近邻原子间的转移能与原子间距离呈线性关系。所有的电子态的数值计算为150个原子的系统和系综平均取超过10个样品。取得了以下结果。(1)As无规度增加，杂化度降低，共价键发生重排。（2）与忽略空间相关性的情况相比，带隙的宽度减小，但是差距保持相当长。（3）在光吸收谱中出现一个特征峰，它反映了部分吸收峰的中心峰。（s-或p-）态密度，并与空间关联引起的电子局域化有关.由于我们采用一维模型，货车霍韦奇异性在带边出现显著，然后我们不能直接将结果与吸收光谱上的实验进行比较。然而，杂交和共价键的重排预计也将在三维中发生。这对于所谓的弱键和悬挂键的稳定性以及它们的变形是很重要的。为了解释各种非晶半导体吸收谱中Urbach尾陡度参数的普适值，对三维体系中原子间距分布和局域共价键进行了自洽计算。

项目成果

Yuzo Shinozuka: "Hybridazation in Eectronic States and Optical Properties of Covalent Amorphous Semiconductors"MRS Proceedings 1999 Fall. 588(印刷中). (2000)

Yuzo Shinozuka：“共价非晶半导体的电子态杂化和光学性质”MRS Proceedings 1999 Fall 588（印刷中）。

Yuzo Shinozuka: "Hybridization in Electronic States and Optical Properties of Covalent Amorphous Semiconductors"MRS Proceedings 1999 Fall. 588 (印刷中). (2000)

Yuzo Shinozuka：“电子态的杂化和共价非晶半导体的光学特性”MRS Proceedings 1999 Fall 588（印刷中）。

Yuzo Shinozuka: "Hybridization in Electronic States and Optical Properties of Covalent Amorphous Semiconductors"MRS Proceedings 1999 Fall Volume 588, Optical Microstructural Characterization of Semiconductors. (in press). (2000)

Yuzo Shinozuka：“共价非晶半导体的电子态杂化和光学特性”MRS 会议记录 1999 年秋季第 588 卷，半导体的光学微观结构表征。