EFFECTS OF WAVE-FUNCTION DELOCALIZATION ON THE OPTICAL-PROPERTIES OF GAAS ALAS SHORT-PERIOD ASYMMETRIC SUPERLATTICES

We have conducted a high-pressure study of asymmetric-period GaAs/AlAs superlattices in order to observe the effects of inter-GaAs-well electronic coupling on the superlattice optical luminescence properties with varying AlAs layer thickness and approximately constant GaAs thickness (20). When the AlAs layers are thick (60), confinement shifts the GaAs "-like state well above the AlAs X-like state in the conduction band, producing a type-II band alignment. For decreasing AlAs thickness, the X-like state shows increasing confinement energy while the "-like state drops in energy due to wave-function delocalization across the barriers. Simultaneously the pressure coefficient of the GaAs-AlAs valence-band energy difference approaches zero for thinner barriers. We interpret this as evidence that the superlattice valence band loses its square-well nature in the thin-barrier limit. © 1990 The American Physical Society.