a-Si:H中本征缺陷引起的赝隙态

本文取原子集团模型Si₈H₁₈,Si₁₇及从连续无规网络中挖取的集团模型Si₂₉和Si₄₇,用CNDO LCAO-MO方法计算其电子结构,探讨了a-Si:H中由弱键、弯键和带电组态等本征缺陷引起的赝隙态分布。结果表明,当弱键拉伸时,两个弱键态移动并收缩至带隙中央;过剩电荷使弱键能级移至价带顶或导带底附近;弯键态主要出现在价带顶附近。当弯键曲率较大时,弯键态上移至带隙中央以下的区域。结构拓扑无序导致 关键词：

GAP STATES DUE TO INTRINSIC DEFECTS IN a-Si:H

Calculations of electronic structures for Si₂₉ and Si₄₇ clusters, which are cut from continuous random networks of a-Si, and those of simple ones Si₈H₁₈,Si₁₇, have been performed by using CNDO LCAO MO method. The origin and nature of the gap states due to intrinsic defects such as weak bond, bent bond and charged configurations are examined in a-Si:H. The results show that two weak bond states situated in both sides of band gap have been contracted and shifted to the center of the gap as the weak bond is stretched. These weak bond levels have been shifted to some location near the top of valence band or near the bottom of conduction band due to extra charges. The bent bond states mainly appear near the top of valence band. When the bond is bent severely,the bond level shifted upwards, close to the center of band gap from below. The structural lopological disorder may induce the gap states at any position within the band gap. It is suggested that all the weak bond and bent bond as well as charged configuration are the principal forms of intrinsic defects in a-Si:H. Various experimental results of gap states are explained according to these theoretical calculations.