Magneto-optical study of ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$Sb/GaSb strained-quantum-well structures: Miniband formation and valence-band structure

Interband magneto-optical studies have been performed on a series of strained single and coupled ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$Sg/GaSb quantum wells. We have investigated the dependence of interwell coupling on the well and barrier thicknesses and on the In content of the wells. Superlattice miniband formation is discussed where we observe a large anisotropy in carrier masses along and perpendicular to the growth direction. A reduced in-plane mass of the highest valence band (‖${\mathit{m}}_{\mathit{J}}$‖=3/2, conventional heavy-hole band) is observed, dependent on the degree of the heavy-hole–light-hole (‖${\mathit{m}}_{\mathit{J}}$‖=1/2) decoupling. An extra Landau level transition appears between the conventional l=0 and l=1 Landau level transitions, increasing in intensity as the magnetic field perpendicular to the layer increases. This is interpreted as a result of mixing between the heavy-hole and light-hole states induced by the magnetic field. Interband spin splitting is observed in narrow ${\mathrm{Ga}}_{0.88}$${\mathrm{In}}_{0.12}$Sb/GaSb single quantum wells but not wide wells. The difference arises from the valence-band spin splittings, which are very dependent on the heavy-hole–light-hole coupling, and therefore on the quantum-well width. These last two observations are explained well by Landau level calculations with the Luttinger k⋅p Hamiltonian.