Surface States for the GaAs(001) Surfaces Observed by Photoemission Yield Spectroscopy

Abstract

The energy distributions of the occupied surface states of GaAs (001) surfaces are measured using photoemission yield spectroscopy. The surfaces are prepared by different kinds of techniques, including molecular beam epitaxy, As decapping, and chemical etching. The surface states are found to change in both distribution and density depending on the surface preparation techniques. The origins of the surface states are discussed in terms of surface atomic structures for the atomically clean surfaces. A great reduction by about one order of magnitude in the density of the surface states is revealed for the surface covered with native oxide compared with the other atomically clean surfaces: the surface state electron density is estimated to be about 3×1013 cm-2 for the latter, and ∼1012 cm-2 for the former.