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Study of Light-induced Structural Change in Hydrogenated Amorphous Silicon by the Glancing-angle Polarized Electroabsorption Technique

掠射角偏振电吸收技术研究氢化非晶硅光致结构变化

基本信息

批准号：
11650325
负责人：
OKAMOTO Hiroaki
金额：
$ 2.18万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

This research program is comprised of three sub-subjects ; 1) development of "Glancing-angle Polarized Electroabsorption (GAPEA) Technique", 2) identification of light-induced structural change and its consequence for light-induced degradation of electronic properties in hydrogenated amorphous silicon (a-Si : H), and 3) evaluation of light-induced internal stress/volume change. The GEPEA in the light-reflection geometry has been established both in the theoretical and technological aspects. The new characterization method has been applied to practical a-Si : H p-i-n junction samples, definitely indicating that the net work disorder is increased by light exposure as had been suggested by our earlier study based on the coplanar-geometry PEA measurements. The internal stress as well as mass density have been measured to provide alternative evidences for the light-induced structural change by the use of the bending-beam method and floatation method, respectively. It is found from these res … More ults that a-Si : H films expand and the density tends to decrease upon light-exposure, the temporal behaviors of which coincide with that of the PEA ratio factor indicating disorderness of the amorphous network structure. The results permit us to conclude that a large scaled change in the amorphous network structure occurs under light-exposure, which might proceed the light-induced creation of metastable dangling bond defects. Theoretical consideration based on the simple site-disordered tight-binding model gives a possible solution ; observed light-induced changes in the polarized electroabsorption signal, electron mobility and optical Urbach tail could be all consistently explained if light exposure would give a striking impact only on the valence band edge states. A preliminary examination involving internal photo emission measurements on a-SiN : H/a-Si : H heterostructures demonstrates the valence band tail slope is broadened upon light exposure, implying the validity of our new idea on the physics of the light-induced disorder. Less

本研究由三个子课题组成：1)掠角偏振电吸收(GAPEA)技术的发展，2)光诱导结构变化及其对氢化非晶硅(a-Si：H)电子性能退化的影响的识别，以及3)光诱导内应力/体积变化的评估。光反射几何中的GEPEA在理论和技术方面都已经建立起来。新的表征方法已被应用于实际的a-Si：Hp-i-n结样品，明确地表明，正如我们先前基于共面几何PEA测量所提出的那样，光暴露增加了网络无序。分别用弯曲束法和浮选法测量了样品的内应力和质量密度，为光致结构变化提供了替代证据。它是从这些RES…中找到的结果表明，a-Si：H薄膜在光照下发生膨胀，密度趋于减小，其时间行为与表征非晶态网络结构无序性的PEA比因子的时间行为相吻合。结果表明，非晶态网络结构在光照射下发生了较大规模的变化，这可能导致了亚稳态悬挂键缺陷的产生。基于简单的格点无序紧束缚模型的理论考虑给出了可能的解决方案；如果光暴露只对价带边状态产生显著影响，则可以一致地解释观察到的光诱导的极化电吸收信号、电子迁移率和光学Urbach尾部的变化。对a-SiN：H/a-Si：H异质结内部光致发射测量的初步研究表明，在光照射下，价带尾斜率变宽，这意味着我们关于光致无序物理的新观点是正确的。较少