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 k ʈ , 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 k•p model and the scattering matrix method. We have found that the order of levels at the zone center (k ʈ ϭ0), 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 k ʈ ϭ0 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.

Carrier transport in broken-gap heterostructures tuned by a magnetic field

“…Consequently, the heavy-hole states in the well do not contribute to the interband-tunneling current. For k ʈ 0 and/or nonzero magnetic field, electron, light-hole, and heavy-hole states can hybridize considerably, 8,[10][11][12][13] and so the heavy-hole-like states can contribute to interband tunneling as much as the lighthole-like states. [20][21][22][23] An eight-band k · p Hamiltonian, including strain and bulk anisotropy but not an applied magnetic field, was used to investigate transmission coefficients and current-voltage ͑I-V͒ characteristics.…”

Effect of nonrelativistic interface Hamiltonian on optical transitions in broken-gap heterostructures

“…When the lowest electron level in the InAs layer lies below the highest hole level in the GaSb layer, existing hybridization gap in in-plane dispersion was observed [8][9][10][11] and analyzed theoretically. [12][13][14][15][16][17][18] The lateral anisotropy of spin-dependent intersubband optical absorption of light linearly polarized along the ͓11͔ and the ͓11͔ directions was also investigated both theoretically and experimentally. [19][20][21][22] The relevant mechanisms are spin-orbit interaction, structural inversion asymmetry ͑SIA͒, bulk inversion asymmetry ͑BIA͒, and low symmetry of interfaces which can be described by a specific interface Hamiltonian ͑IH͒.…”

“…The explicit forms of Ĥ 4 , Ĥ so , and Ĥ ⑀ are given in Ref. 17. The next two terms Ĥ ⑀k and Ĥ B are due to BIA, and the last matrix Ĥ k is the interface Hamiltonian.…”

<title>Electronic band structure and semimetal-semiconductor transition in InAs/GaSb quantum wells</title>

“…(The effect of strain on subband dispersions was considered in Ref. [9].) In our calculations, we suppose for simplicity that each AlSb barrier is of 10 nm thickness and the bias voltage is applied between two GaSb contacts with the acceptor concentrations equal to 2 iO'7 cm3 placed to the left and to the right of the structure.…”

“…In this procedure, we neglect small subband anisotropy considered in Ref. [9]. Once the electron and hole charge density distributions have been obtained, the Poisson equation is solved taking into account the positive charge of donor defects which are supposed to be ionized.…”