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，我们在包含局部长尾状态的无定形半导体中提出了一个非平衡载体动力学的理论，其中允许通过隧道进行有限的相互作用。深入探索傅立叶域解决方案，以定量解释由调制光电流测量确定的频率依赖性光载体漂移迁移率。理论分析与在广泛的频率和温度下对氢化无定形硅进行的实验非常吻合，并揭示了隧道转变的包含可以大大加速固定型带tail的载体热化。还详细研究了一种直接捕获带载体的隧道转移和隧道转移到重组中心中的广义重组模型，这表明即使对于室温，隧道重组也优先进行。在这项研究中还执行的是在调制的光激发下的频域测量，称为飞行频率分辨时间，以评估电子和孔的漂移迁移率。 P-I-N样品测得的飞行光谱的电子时间由于非分散运输状态的运输时间效应而表现出振荡结构。频谱拍打的分析决定了频率依赖性漂移迁移率，并对该材料的运输特性产生定量评估。在强烈的光线曝光下，飞行实验的时间观察到了孔漂移迁移率的大量降低，这说明了光诱导的无定形硅网络无序对价值带边缘附近的电子状态产生了强烈的影响。