Surface states at the GaAs-germanium nitride interface

Metal/insulator/semiconductor (MIS) structures were produced by reactive sputter deposition of germanium nitride onto n-GaAs. The electrical properties of the n-GaAs-germanium nitride interface were found to exhibit a strong dependence on the deposition process parameters and the annealing conditions. The interface density evaluated from conductance and capacitance measurements was of the order of 10¹¹ eV^-1 cm^-2 at the midgap, and was improved by annealing in a hydrogen atmosphere before and after metallization. Because of a possible excess of germanium ions near the interface a counterclockwise hysteresis in the capacitance-voltage curve was observed. The dependence of germanium nitride film properties on heat treatment at different temperatures in hydrogen and nitrogen gas was studied by X-ray diffraction analysis and ellipsometric measurements. The low interface state density found using low r.f. sputtering power establishes sputtering as a competitive deposition technique.