Intersubband optical transitions in InAs/GaSb broken-gap quantum wells

摘要

We investigate the intersubband optical transitions in the InAs/GaSb quantum wells using Burt's envelope function theory and the eight-band model. The self-consistent potential and the lattice-mismatched strain are taken into account to study the effects of bulk inversion asymmetry (BIA) and low interface symmetry on optical matrix elements in structures grown on the InAs substrate along the [001] direction. We have found that both BIA and low symmetry interface Hamiltonian (IH) can result in initially forbidden spin-flip optical transitions or initially forbidden spin conserved optical transitions caused by linearly polarized light. For the light polarization in the plane of the structure, the originally forbidden spin-flip processes can be induced if the light polarization is along the quasiparticle wave vector. However, if light polarization is normal to it, then the originally forbidden spin-conserved processes can be induced. If the light is polarized normally to interfaces along the growth direction [001], then the originally forbidden spin-flip transitions are activated, if in-plane wave vector of the initial quasiparticle states is along the [10] direction. We have also found a considerable lateral anisotropy of absorption caused mainly by BIA induced mechanism. The principal point of this mechanism is the interface contribution to the optical matrix elements due to the material-dependent Kane's B-parameter.