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Study of Carrier Transport Property in Amorphous Semiconductors by Light Excited Hall effect

光激发霍尔效应研究非晶半导体载流子传输特性

基本信息

批准号：
07650376
负责人：
OKAMOTO Hiroaki
金额：
$ 1.34万
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：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Carrier mobility is one of the fundamental physical quantities which largely impact the device performance. In this regard, the knowledge of the carrier mobility is indispensable for the refinements of material processing as well as device design. However, for amorphous semiconductors including amorphous silicon alloys (a-Si) which are of great interest in solar cell field, no simple means have been available for the direct measurement of the "free" carrier mobility, instead it is conventionally deduced from the temperature dependence of the TOF "total charge-carrier" mobility by relying on some specific models. The present work aims to establish a new tool for the determination of free carrier mobility near the band edge by the use of polarized electroaborption and Hall measurements, and to investigate how mobilities are affected by alloying, doping, preparation conditions and/or various treatments after preparation. Upon Phosphorous doping, the electron mobility decreases to about one-third of that in undoped case, while the hole mobility remains almost unchanged. If the long-range potential fluctuation plays a critical role in determining the transport property, then both the electron and hole mobilities should be equally reduced by the incorporation of charged impurities and/or defects, which is, however, in contradiction with our experimental observation. Furthermore, we have found on B doped materials a qualitatively identical behavior of mobilities ; drop in the electron mobility, but no significant reduction in the hole mobility. These findings seem to imply that the doping-induced change in mobilities should not be attributed to classical charge effects, but the incorporation of impurity atoms itself may be of central importance.

载波移动性是影响设备性能的基本物理量之一。在这一点上，载流子迁移率的知识对于改进材料加工和器件设计是不可或缺的。然而，对于太阳能电池领域非常感兴趣的非晶态半导体，包括非晶硅合金(a-Si)，还没有简单的方法来直接测量“自由”载流子迁移率，而是依赖于一些特定的模型，传统地根据TOF“总电荷-载流子”迁移率的温度关系来推导它。本工作旨在建立一种新的工具，通过极化电脱附和霍尔测量来确定带边附近的自由载流子迁移率，并研究合金化、掺杂、制备条件和/或制备后的不同处理对迁移率的影响。磷掺杂后，电子迁移率下降到未掺杂时的三分之一左右，而空穴迁移率几乎保持不变。如果长程势涨落在决定输运性质中起关键作用，那么电子和空穴的迁移率应该通过引入带电杂质和/或缺陷来同等地降低，然而，这与我们的实验观察相矛盾。此外，我们还发现在B掺杂材料上具有相同的迁移率行为：电子迁移率下降，但空穴迁移率没有显著降低。这些发现似乎表明，掺杂引起的迁移率变化不应归因于经典的电荷效应，但杂质原子的加入本身可能是核心重要的。