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Bandtail States and Carrier Transport in Amorphous Silicon

非晶硅中的带尾态和载流子传输

基本信息

批准号：
11650324
负责人：
HATTORI Kiminori
金额：
$ 2.24万
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

In this study, we have pursued a theory for nonequilibrium carrier kinetics in amorphous semiconductors containing localized bandtail states among which finite interactions are allowed via tunneling. Fourier domain solutions are explored intensively in order to quantitatively interpret the frequency-dependent photocarrier drift mobility determined by modulated photocurrent measurement. The theoretical analysis is in good agreement with experiments carried out for hydrogenated amorphous silicon over a wide range of frequencies and temperatures, and discloses that the inclusion of tunneling transitions considerably accelerates carrier thermalization in localized bandtail states. A generalized recombination model which considers both direct capture of band carriers and tunneling transfer of bandtail carriers into recombination centers is also examined in detail, suggesting that even for room temperature, the tunneling recombination takes place preferentially. Also performed in this study is the frequency-domain measurement of junction photocurrent under a modulated photoexcitation, called the frequency-resolved time of flight, in order to evaluate the drift mobilities of electrons and holes, separately. The electron time of flight spectra measured for a p-i-n sample exhibit an oscillatory structure due to a transit time effect in a non-dispersive transport regime. The analysis of the spectral beat determines the frequency dependent drift mobility, and yields quantitative assessments of the transport properties of this material. Under an intense light exposure, the time of flight experiments observe a sizable reduction of the hole drift mobility, which illustrates that the light induced disordering of amorphous silicon network gives a strong impact on the electronic states near the valence band edge.

在这项研究中，我们追求的非平衡载流子动力学理论在非晶半导体包含本地化的带尾状态之间的有限相互作用，允许通过隧道。傅立叶域的解决方案进行了深入的探索，以定量解释的频率依赖的光生载流子漂移迁移率确定调制光电流测量。的理论分析是在很宽的频率和温度范围内进行的氢化非晶硅的实验，并揭示了隧道跃迁的列入大大加速载流子热化在本地化的带尾状态。一个广义的复合模型，它考虑了直接捕获的带载流子和隧穿转移带尾载流子到复合中心也详细检查，这表明，即使在室温下，隧穿复合优先发生。在这项研究中还进行了调制光激发下的结光电流的频域测量，称为频率分辨飞行时间，以分别评估电子和空穴的漂移迁移率。测量的电子飞行时间谱的p-i-n样品表现出振荡结构，由于在非色散传输制度的渡越时间效应。的光谱拍的分析确定的频率相关的漂移迁移率，并产生定量评估的这种材料的传输特性。在强光照射下，飞行时间实验观察到空穴漂移迁移率的相当大的降低，这说明光诱导非晶硅网络的无序对价带边缘附近的电子态产生了强烈的影响。