EVIDENCE OF TYPE-I BAND OFFSETS IN STRAINED GAAS1-XSBX/GAAS QUANTUM-WELLS FROM HIGH-PRESSURE PHOTOLUMINESCENCE

We have used high-pressure photoluminescence in a diamond anvil cell to investigate the band offsets between strained GaAs1-xSbx and unstrained GaAs for x = 0.12. It has generally been expected that this system should display a strongly type-II band lineup, with holes confined in deep GaAs1-xSbx wells and the lowest-energy electron states in GaAs. Our results on a multiple-quantum-well sample show that this is not the case. We measure the photoluminescence transition energies up to and beyond the GAMMA-X crossover near 36 kbar, where the luminescence becomes indirect. The character of the GAMMA-X crossover dependence on well width requires a type-I offset for the X minimum and suggests a type-I offset for the GAMMA minimum of the conduction band. This is in good agreement with theory when the strong band-gap bowing in the GaAs1-xSbx alloy system is properly taken into account.