Morphologic and electronic changes induced by thermally supported hydrogen cleaning of GaAs(110) facets

Abstract

Hydrogen exposure and annealing at 400 °C leads to a layer-by-layer etching of the n-doped GaAs(110) cleavage surface removing islands and forming preferentially step edge sections with [001] normal vector. In addition, a large density of negatively charged point defects is formed, leading to a Fermi level pinning in the lower part of the bandgap. Their charge transfer level is in line with that of Ga vacancies only, suggesting that adatoms desorb preferentially due to hydrogen bonding and subsequent Ga–H desorption. The results obtained on cleavage surfaces imply that the morphology of nanowire sidewall facets obtained by hydrogen cleaning is that of an etched surface, but not of the initial growth surface. Likewise, the hydrogen-cleaned etched surface does not reveal the intrinsic electronic properties of the initially grown nanowires.