Observation of the Orientation Dependence of Interface Dipole Energies in Ge-GaAs

Abstract
The interfaces between a thin (∼20-Å) abrupt epitaxial layer of Ge grown on substrates of (111), (110), and (100) GaAs have been investigated with x-ray photoelectron spectoscopy. Observed changes in core-level binding energies have been directly related to the crystallographic orientation dependence of interface dipoles and variations of band-gap discontinuities. The orientation variation of the band-gap discontinuities is found to be a significant fraction (≈ ¼) of the total band-gap discontinuity.