应变层超晶格InAs/InP界面的平均键能行为与价带边不连续性

THE AVERAGE BOND ENERGY AND THE VALENCE-BAND EDGE OFFSET AT THE INTERFACE OF STRAINED SUPERLATTICE InAs/InP

采用LMTO能带方法,对两种不同应变状态下(自由形变和以InP为衬底),应变层超晶格(InAs)_1(InP)_1(001)和与应变层超晶格的分子层相对应的应变体材料,以及无应变的体材料进行了第一原理计算,并采用冻结势方法求出了两种超晶格各分子层的平均键能。结果表明,能存在应变的情况下,异质界面两边的平均键能非常一致,且这种一致性受应变状态的影响很小,因而可以把它用来作为确定应变层超晶格价带边不连续值(△E_v)的普遍适用的参考能级。研究了应变对超晶格分子层能带结构的作用及其对△E_v值的影响。本文以平均键能为参考能级所得出的△M_v值与冻结势方法的结果及XPS的实验测量值非常一致。

The electronic structures of the strained superlattice (SLS) (InAs)1 (InP)1 (001)under two strain conditions (free-standing model and InP-substrate model) and the strained bulk materials corresponding to the molecular layers in the SLS as well as the unstrained bulk materials are calculated with the ab initio LMTO band structure method. The average bond energy of molecular layers in the two SLS are determined with the frozen-potential approach. The results show that the average bond energies are well aligned across the interfaces and this alignment is not almost affected by the condition of strain. Thus, the average bond energy can be considered as a very reasonable reference energy level for determined the valence band offset in SLS. The strain effects on the band structures of molecular layers in SLS and on the △Ev values are investigated. Results given by frozen potential approach and using Em as a reference level in this paper are in good agreement with the available experimental datum from XPS measurement.