Tuning AlAs-GaAs band discontinuities and the role of Si-induced local interface dipoles

Abstract

The presence of thin ordered layers of Si within the interface region of AlAs-GaAs heterostructures is found to tune the valence-band offset throughout the 0.02--0.78 eV range. High-resolution x-ray-photoemission studies of heterostructures prepared in situ by molecular-beam epitaxy as a function of substrate temperature, arsenic flux, interface concentration of Si, and growth sequence (AlAs on GaAs versus GaAs on AlAs) indicate that this tunability is associated with a Si-related local dipole which can be added to or subtracted from the intrinsic AlAs-GaAs valence-band offset of 0.40 eV.