A self-consistent investigation of the semimetal–semiconductor transition in InAs/GaSbquantum wells under external electric fields

Abstract

We investigate the phase transitions in InAs/GaSb quantum wells sandwiched between twowide-gap AlSb barrier layers under an external electric field perpendicular to interfaces.The Schrödinger and the Poisson equations are solved self-consistently to derive the subbanddispersions, the potential profile, the electron charge distribution in the InAs layer,and the hole charge distribution in the GaSb layer. The Burt–Foreman envelopefunction theory and the scattering matrix method are used to solve the Schrödingerequation in the framework of the eight-band model, including the spin-splitting of subbands in our calculation. We have found that ina thick InAs/GaSb quantum well, which has been investigated experimentallyby Cooper et al (1998 Phys. Rev. B 57 11915), under low external electric fields,two electron levels stay below the highest hole level at zero in-plane wavevectork‖ = 0. Then, the anticrossings of electron and hole levels produce several minigaps in thein-plane dispersions, inside which the states of other subbands exist. As a result, thesystem is in a semimetal phase. With increasing external electric field, the semimetal phasechanges to semiconductor phase with only one hybridization gap. When all electronlevels become higher than the hole levels at higher electric fields, the system has asemiconducting gap.