RELATION BETWEEN BAND-GAP SHRINKAGE AND OVERLAP OF INTERFACE STATES IN POLAR (GAAS)N/(GE2)N [001] SUPERLATTICE

被引:1
作者
SAITO, T
IKOMA, T
机构
[1] Institute of Industrial Science, University of Tokyo, Minato-ku, Tokyo, 106
关键词
D O I
10.1016/0749-6036(91)90263-Q
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
We have calculated the band structures of (GaAs)n/(Ge2)n [001] superlattices (SL's) with n=10∼1 to understand the origin of the band gap shrinkage in the (GaAs)1/(Ge2)1 [001] SL. The calculations are performed by a semi-empirical tight-binding method with the sp3s* basis. We have studied two kinds of states in the SL's. The first one corresponds to the states at the conduction and valence band edges, which are confined two-dimensionally in the Ge layers. The energy gap between the confined states increases (1.07eV at the X-point for n=2) with decreasing SL period, n, due to the quantum confinement effect. The second one corresponds to the interface states constituting the two interface bands in the gap. The interface states on the lower and upper interface bands are located at the Ga-Ge and As-Ge interfaces, respectively. By decreasing n, a sudden decrease in the band gap (Eg=0.16eV at the R-point) is obtained at n=1. The origin of the band gap shrinkage is related to the fact that the overlap of the interface states becomes so large that they can combine as the band states. © 1991.
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页码:377 / 381
页数:5
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