a-Si:H/a-SiN_x:H超晶格中空间电势分布和光电导的理论计算

CALCULATION OF ELECTRONIC POTENTIAL DISTRIBUTIONS AND PHOTOCONDUCTIVITY IN a-Si:H/a-SiN_x:H SUPERLATTICES

本文从a-Si:H体材料的缺陷态模型出发,考虑在a-Si:H/a-SiN:H超晶格中由于空间电荷转移掺杂效应,以及界面不对称引起的a-Si:H阱层的能带下降和弯曲,严格求解空间电势分布和电荷分布,发现a-Si:H阱层中能带的下降值远大于由界面电荷不对称所引起的两端电势能差,且随转移到阱层中的电荷总量的变化非常敏感。空间电荷分布比较平缓,当不对称参数K=0.9时,空间电荷浓度的最大差值不到两倍。在此基础上,计算了超晶格中光电导的温度曲线,发现引起超晶格中暗电导和光电导相对于单层膜增大的主要原因是转移电荷量的多少,而界面电荷不对称的影响则小得多。计算中对带尾态采用Simmons-Taylor理论,考虑a-Si:H中悬挂键的相关性,并用巨正则分布讨论其在复合过程中的行为。

A reasonable model is proposed to calculatee the temperature dependence of photoconductivity (PC) in a-Si:H and a-Si:H/a-SiNx:H super lattices. Simmons-Taylor theory and the occupation statistics of correlated defects are used to describe band tail states and dangling bonds states. As in a-Si:H/a-SiNx:H superlattices, the electronic potential and charge distributions resulting from space-charge doping are calculated at various amounts of transferred charge and different asymmetry boundary conditions. The DC and PC are calculated with corresponding space potential and charge distributions. It is found that the enhancements of DC and PC in superlattices are mainly determined by the amouns of injected charge, and the influence of interface asymmetry is slight.