A Note on the Band-Folding Effects in the (GaAs)n/(AlAs)1, (GaAs)1/(AlAs)n (n{=}1∼ 10) Superlattices

The electronic band structures of (GaAs)_n/(AlAs)₁ and (GaAs)₁/(AlAs)_n (n{=}1∼ 10) superlattices were investigated by means of an improved tight-binding method in which the overlap integrals up to the second nearest-neighbor atoms, including new parameters, were explicitly taken into account. Kroemer’s rule for the band offset value was employed. The resulting band structure of superlattices in the extended zone scheme were compared with the bulk band structure while paying attention to the band-folding effect due to a periodic insertion of one atomic monolayer. A possibility of transforming an indirect-gap material into a direct-gap material by such artificial insertion of another material is discussed and the optical oscillator strength at the Γ-point is estimated for each n.