Effect of non-abrupt interfaces in AlAs/GaAs superlattices with embedded GaAs quantum wells

In the present paper, we investigate the effect of the non-abrupt interface s on the electronic and optical properties of short-period AlAs/GaAs superl attices with embedded GaAs quantum wells. The lateral disorder and the comp onent interdiffusion at the interfaces are averaged over the layer planes a nd are effectively represented by a diffusion concentration profile in the growth direction. The diffusion length L-D is used as a parameter character izing the degree of interface broadening. The electronic structure calculat ions are made using the sp3s* spin-dependent empirical tight-binding Hamilt onian, the virtual crystal approximation, and the surface Green function ma tching method. The dependencies of the lowest electron (E1), heavy hole (HH 1), and light hole (LH1) bound states on the diffusion length are calculate d for L-D from 0 to 4 monolayers. It is found that the energies of the tran sitions (E1-HH1) and (E1-LH1) increase as L-D increases. The results obtain ed are compared with photoluminescence data for MBE-grown samples. It is fo und that the degree of interface broadening depends on the growth temperatu re and on the sample geometry. The diffusion lengths calculated from the ex perimental data follow the expected trends, revealing a good qualitative ag reement between theory and experiment. (C) 2000 Elsevier Science Ltd. All r ights reserved.