Inequality of semiconductor heterojunction conduction-band-edge discontinuity and electron affinity difference

Abstract
The commonly used Anderson electron affinity rule is shown not to provide the band-edge offsets at the interface between different semiconductors. Using synchrotron radiation excited photoelectron spectroscopy, we determine electron affinities χ of 4.14 +0.17−0.09 eV for a Ge(110) surface and of 4.15 +0.17−0.09 eV for a 18-Å GaAs(110) epitaxial overlayer on Ge(110). In the same experiment, for the same layers, a conduction-band discontinuity ΔEc of 0.54±0.08 eV is measured for the heterojunction of GaAs grown by molecular beam epitaxy on Ge(110). Compilation of data on 14 recent photoemission studies confirms that ΔEc≠Δ χ for most heterojunction systems investigated to date.