Reversal of light- and heavy-hole valence bands in strained GaAsP/AlGaAs quantum wells

We have experimentally determined the magnitude of the light-hole-heavy-hole exciton energy difference as a function of biaxial tensile strain in GaAsP/AlGaAs quantum wells using 5 K photoluminescence excitation spectroscopy. The strain is induced by the addition of phosphorus into the GaAs well layer which decreases its lattice constant so that it is less than that of the AlGaAs barrier material. Under certain conditions, the strain resulting from the lattice mismatch is large enough to reverse the order of the light- and heavy-hole valence bands. We found good overall agreement between the experimentally determined dependence of the light-hole-heavy-hole energy difference on the phosphorus concentration in the well layer and a simple calculation which included the effects of spatial confinement and biaxial tensile strain on quantum well exciton energies.