Reduction of interface state density at SiO2/InAlN interface by inserting ultrathin Al2O3 and plasma oxide interlayers

SiO2/InAlN interfaces formed by plasma-enhanced chemical vapor deposition were investigated. X-ray photoelectron spectroscopy showed that the direct deposition of SiO2 onto an InAlN surface led to the oxidation of the InAlN surface. The interface state density, D-it, was on the order of 10(12) cm(-2) eV(-1) (5 x 10(12) cm(-2) eV(-1) at 0.3 eV from the conduction band edge, E-c), which indicated the possibility of improving the interface properties. Reduction of the interface state density was attempted using an Al2O3 interlayer and a plasma oxide interlayer. The insertion of a 2-nm-thick Al2O3 interlayer to prevent surface oxidation by plasma reduced D-it slightly. A marked reduction in D-it to less than 10(11) cm(-2) eV(-1) deeper than 0.3 eV from E-c, however, was achieved by the intentional formation of a 1-nm-thick plasma oxide layer, formed by N2O plasma oxidation, as an interlayer between SiO2 and InAlN. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim