Valence-band coupling in thin (Ga,In)As-AlAs strained quantum wells

Model representations of varying complexity are used to describe the band structure of semiconductor quantum wells and superlattices. However, the physics of valence-band-confined states is usually restricted to the upper ${\mathrm{\Gamma }}_8^{\mathit{v}}$ band. We report spectroscopic measurements of the light- to heavy-hole splitting in (Ga,In)As-AlAs strained multiple quantum wells. The results are compared to two types of theoretical calculations: (i) within the framework of the usual approximations, and (ii) taking account of the ${\mathrm{\Gamma }}_7^{\mathit{v}}$ split-off states, which are mixed with the light-hole ones. We demonstrate the crucial influence of the valence-band coupling, by a significant improvement of the agreement between theory and experiments. Competitive effects of thicknesses, potential-well depths, and magnitude of the ${\mathrm{\Gamma }}_8^{\mathit{v}\mathrm{-}}$${\mathrm{\Gamma }}_7^{\mathit{v}}$ splitting are detailed and discussed.