Effects of bulk inversion asymmetry and low interface symmetry on the optical properties of broken-gap heterostructures

Abstract

We have studied the influence of bulk inversion asymmetry (BIA) and the relativistic part of the low-symmetry interface Hamiltonian (IH) on intersubband optical transitions, induced by linearly polarized light, between strongly hybridized electron-hole states in asymmetrical $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{Sb}$ broken-gap quantum wells grown along the [001] direction. The self-consistent calculations were performed using the Burt-Foreman envelope function theory and a sophisticated eight-band $\mathbf{k}∙\mathbf{p}$ model Hamiltonian. We found that the BIA and the IH can activate originally forbidden spin-flip optical transitions, and that the strength of the corresponding optical matrix elements depends on the light polarization direction and the quasiparticle in-plane wave vector. Both the BIA and the IH contribute significantly to this effect. When the initial electron-hole states are strongly hybridized, the spin-flip optical transition probability can be of the same order as the probability of the spin-conserved transitions. The BIA results in interface-localized terms in the optical matrix elements due to the material-dependent Kane's $B$ parameter and produces a strong in-plane anisotropy in the absorption of light polarized along the [11] and $[1\overline{1}]$ directions. The IH also contributes to this effect. We found that the primary contribution to the optical anisotropy comes from the BIA-induced mechanism.