Atomic-Scale Structures of Top and Bottom Heterointerfaces in GaAs–AlxGa1-xAs (x=0.2-1) Quantum Wells Prepared by Molecular Beam Epitaxy with Growth Interruption

Abstract

We have studied microscopic structures of two different interfaces in MBE-grown GaAs–Al _x Ga_1-x As quantum wells (QWs), and effects of growth interruption on the interface roughness. For QWs with x>0.5, the effective roughness of top (AlGaAs-on-GaAs) interfaces is drastically reduced down to less than 0.2 atomic layer by the growth interruption, whereas bottom (GaAs-on-AlGaAs) interfaces are unaffected and act as pseudo-smooth interfaces even without the interruption. However, for QWs with x<0.3, bottom interfaces are similar to top interfaces, and can be smoothed by the growth interruption. Microscopic models of various heterointerfaces are presented.