Band Structure of Semiconductor Superlattices with Ultrathin Layers (GaAs)n/(AlAs)nwithn=1, 2, 3, 4

Abstract

The band structures of ultrathin layered superlattices (GaAs) _n /(AlAs) _n with n =1, 2, 3 and 4 are calculated by the self-consistent pseudopotential method. In this calculalion a value of α in the Xα approximation for the exchange-correlation potential is adjusted so as to reproduce both band gaps of GaAs and AlAs. This reflects an effect of the self-energy correction. The resulting band structures and charge densities show that upper valence band states of (GaAs) _n /(AlAs) _n with n =1 to 4 are approximately obtained by folding the valence bands of GaAs and AlAs, while that lower conduction band states correspond to strong hybridization of folded bands of GaAs and AlAs. It is shown that the band gap of (GaAs) ₁ /(AlAs) ₁ is indirect, while those for n =2 to 4 are direct and decrease with increasing n. This trend is consistent with recent experimental results.