NITRIDATION OF GAAS(110) USING ENERGETIC N+ AND N2+ ION-BEAMS

X-ray photoelectron spectroscopy is used to monitor surface stoichiometric and electronic changes that result from reactive nitrogen ion beam bombardment of GaAs(110) at room temperature. This treatment leads directly to the formation of a thin GaN reaction layer. The nitride layer thickness is found to depend on ion dose, incident energy (0.5-3 keV) and composition (N+, N2+) in a manner that suggests that the growth kinetics are limited by sputter desorption of the growth surface. A comparison of results is made between 1 keV Ar+ and 1 keV N2+ bombarded surfaces to distinguish to what extent changes in the surface composition and band bending are physical bombardment or chemically induced. We demonstrate that bombardment-induced crystal lattice imperfections are a dominant source of electronically active band gap acceptor states. From band bending measurements evidence is given that suggests N2+ ion bombardment yields a lower concentration of charge acceptor states in comparison to Ar+ ion bombardment. We attribute this behavior to the formation of strong GaN bonds that help to minimize the group V surface depletion and lattice disorder.