Valence-band-shape modification due to band coupling in strained quantum wells

We have observed the strong dependence of the in-plane effective masses of the heavy-hole and light-hole valence bands in quantum wells on their coupling. The magnitude of this interaction, which is a function of the energy separation of the two bands, was tuned by adjusting the magnitude of tensile strain and well width in ${\mathrm{GaAs}}_{1\mathrm{-}\mathit{y}}$ ${\mathrm{P}}_{\mathit{y}}$/${\mathrm{Al}}_{0.35}$ ${\mathrm{Ga}}_{0.65}$As quantum wells. A distinct increase of both the heavy- and light-hole masses is observed when the bands merge at k=0, consistent with theoretical predictions.