Study of Light Induced Effects on the Carrier Transport Property in Amorphous Silicon

频率相关（ac）电导率是无序固体的特征，长期以来一直是人们非常感兴趣的课题，并从各种导电系统的微观和宏观图像中进行了论证。最近的实验研究揭示了归一化交流电导率的“通用”频率标度的存在，这被发现在理论上很好地再现了极端无序系统，其中通过强局域/结合位点的跳变电荷传导占主导地位。在这些讨论中排除的是在非晶半导体的迁移率边缘附近的交流电子电导率，它可能表现出类似的缩放特征。因此，这项工作的目的是追求迁移率边缘电子电导率的通用交流标度，并推断从测量中提取的信息，特别是光诱导对带边载流子输运的影响。在弱局部化问题的重整化群处理的基础上，研究了迁移率边缘附近随频率和温度变化的电子传导。通过对直流电导率的归一化，发现交流电导率遵循一个简单的普适方程，这个普适方程与各种不同的跳变传导系统的普适方程非常相似。将理论结果应用于氢化非晶硅在良好退火和光浸泡状态下的交流电导率实验数据集，结果表明，光浸泡不会改变导带边缘局域态的能量宽度，并保持在100 meV左右。

The frequency dependent (ac) conductivity being characteristic to disordered solids has been long a subject of great interest, and argued from both the microscopic and macroscopic pictures of various conduction systems. Recent experimental studies have revealed an existence of "universal" frequency-scaling of the normalized ac conductivity, that is found to be well reproduced theoretically for extremely disordered system in which hopping charge conduction via strongly localized/bound sites is predominant. What is excluded in these discussions is the ac electronic conductivity near the mobility edge in amorphous semiconductors which is likely to exhibit similar scaling feature. The aim of this work is, then, to pursue the universal ac scaling for the mobility edge electronic conductivity as well as to infer to the information to be extracted from the measurements, especially the light induced effects on the band-edge carrier transport. Frequency and temperature dependent electronic conduction near the mobility edge is investigated on the basis of the renormalization group treatment for weak localization problems. The ac conductivity normalized by its dc counterpart is found to follow a simple universality equation being quite similar to that obeyed in common for various different hopping conduction systems. The theoretical results have been applied to the experimental data sets acquired on the ac conductivity of hydrogenated amorphous silicon in the well-annealed and light-soaked states, indicating that the the energy width of the conduction band edge localized states is not changed by light-soaing, and stays at aroud 100 meV.