Strain-induced semimetal-semiconductor transition in InAs/GaSb broken-gap quantum wells

Abstract

We investigate the hybridization of the electron, heavy-hole and/or light-hole dispersion relations in strained InAs/GaSb quantum wells. In the considered structures, the lowest electron level lies below several hole levels at zero in-plane wave vector ${\mathbf{k}}_{\ensuremath{\Vert}},$ so that the anticrossings of subbands produce gaps in the in-plane dispersions. To calculate the electronic band structures of such quantum wells grown on different substrates, we use the eight-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ model and the scattering matrix method. We have found that the order of levels at the zone center $({\mathbf{k}}_{\ensuremath{\Vert}}=0),$ gap positions and magnitudes can change due to the lattice-mismatched strain. Strain can also enhance the hybridization of electron and light-hole states at ${\mathbf{k}}_{\ensuremath{\Vert}}=0$ considerably. In the structure with a thick InAs layer grown on GaSb, we have obtained a negative indirect gap in the in-plane dispersion resulting from the anticrossing of electronlike and highest heavy-hole-like subbands. If the substrate is InAs, the gap becomes direct and positive. This phenomenon can be treated as strain-induced semimetal-semiconductor phase transition.