Control of plasma-CVD SiO2/InAlN interface by ultrathin atomic-layer-deposited Al2O3 interlayer

Abstract

To control a plasma-CVD SiO2/InAlN interface, the insertion of an ultrathin Al2O3 interlayer deposited by atomic layer deposition was investigated. The thickness of the Al2O3 interlayer was varied between 0.5 and 2 nm. Compared with the direct deposition of SiO2, the insertion of a 2 or 1 nm thick Al2O3 interlayer resulted in the similar interface state density Dit distribution. However, a significant reduction in Dit was achieved by using a 0.5 nm thick Al2O3 interlayer. Slight oxidation of the InAlN surface under the 0.5 nm thick Al2O3 interlayer was observed by X-ray photoelectron spectroscopy (XPS). This result indicated that a native oxide/InAlN interface was formed without disorder beneath the 0.5 nm thick Al2O3 interlayer, while plasma damage was prevented at the interface. On the other hand, the density of positive charges at the interface increased with the Al2O3 interlayer thickness. The generation process of the interface charge is discussed on the basis of XPS data.