Surface passivation of GaAs using an ultrathin cubic GaN interface control layer

An attempt was made to passivate the GaAs surface by a Si3N4/c-GaN/GaAs passivation structure, having an ultrathin cubic GaN as an interface control layer (ICL) with a wide energy gap. The GaN ICL was formed by direct nitridation of GaAs with active nitrogen radical species in a molecular beam epitaxy (MBE) chamber. A detailed in situ x-ray photoelectron spectroscopy study confirmed formation of 1 or 2 monolayers of pseudomorphic cubic GaN layer. A remarkable increase of the quantum efficiency of photoluminescence (PL) by a factor of 30 was obtained by forming the passivation structure on the MBE grown clean (001) GaAs under optimum conditions. This indicates a large reduction of the surface recombination velocity. The increase of the PL intensity was extremely stable, maintaining its value even after leaving the sample in air for 2 months. Detailed ultrahigh vacuum contactless capacitance-voltage (C-V) measurements and usual metal-insulator-semiconductor C-V measurement indicated reduction of interface states, realizing a wide movement of the Fermi level within the midgap region. (C) 2001 American Vacuum Society.