Characterization of Sturctural Disorder by means of Polarized Photoreflectance in Amorphous Semiconductors

通过非晶半导体中的偏振光反射表征结构无序

基本信息

批准号：
05650305
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 General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Polarized Electroabsorption technique (PEA) has been developed for the determination of carrier mean free path as well as mobility near the band edge in amorphous semiconductors. The method is based upon the result of microscopic theory of optical spectrum in the presence of external electric fields, which indicates that an "extrinsic" polarization dependence of the EA signal appears due to the fieldinduced change in the matrix element for transitions involving localized states, so that it serves as a measure of the degree of disorder in amorphous semiconductors. Measured EA signal intensity ratio between field-light polarization parallel and perpendicular conditions is transrated into carrier mean free path and band edge mobility. We have applied this new technique to amorphous silicon alloys. The conclusions reached from the present work are as follows ;1) The electron (hole) mean free path is about 12* (5*) for device quality undoped a-Si : H,which yields estimate of the electron (hole) mobility of 10 cm2/Vs (3cm2/Vs).2) The mobilities attain maxima at a particular deposition temperature which would depend on details of deposition conditions.3) Annealing treatment on a-Si : H deposited at a low temperature improves carrier mobilities through the relaxation of structural disorder.4) Alloying with carbon leads to a continuous reduction of mobility, with the largest drop (15%) for a carbon concentration of about 10 at%, this being in sharp contrast to a less-pronounced effect by germanium alloying.5) Phosphorus doping ramarkably detoriorates the electron mobility, while the hole mobility remains almost unchanged from that in undoped material.

已经开发出偏振电吸附技术（PEA），以确定载体平均自由路径以及在无定形半导体中带边缘附近的迁移率。该方法基于在存在外电场的光谱的显微镜理论的结果，这表明EA信号的“外部”极化依赖性是由于涉及局部状态的过渡矩阵元素的现场诱导的变化而出现的，因此它可以用作不良半多管的无序程度的度量。测得的EA信号强度比平行和垂直条件之间的野外极化比率将其跨为载体平均自由路径和带缘迁移率。我们已经将这种新技术应用于无定形硅合金。从目前的工作得出的结论如下：1）电子（孔）平均自由路径约为12*（5*），用于设备质量的未固定A-SI：H，该估计值估算了10 cm2/vs（3cm2/vs）的电子（孔）迁移率。2在低温下，通过放松结构性障碍，可以改善载体。未稳定的材料。