Localization and other properties of electronic states in a semiconductor revealed by their response to surface doping and band-bending potential

Abstract

Using photoelectron spectroscopy (PES), we study InAs(001) and InAs(110) surfaces, doped with Te atoms to induce strong band-bending phenomena and a formation of two-dimensional electron gases (2DEGs). The band structure of the 2DEGs as well as the coexisting 3D bulk electronic structure are investigated. We discuss several schemes to estimate the band-bending potentials at surfaces by PES methods, appropriate in different situations, e.g. in the presence of a significant band tailing. We use the Schroedinger–Poisson scheme as well as the Thomas–Fermi method to model the band-bending potential profiles and the 2DEG band energies. For the InAs crystal we find that the valence bands investigated with PES closely follow the band-bending potential which evidences that valence electronic states are localized to within few nm. In contrast, the conduction band is entirely insensitive to the band-bending potential, evidencing that the extent of electronic states within this band is at least 103nm.