Effect of oxidation on the optical and surface properties of AlGaN

The chemical properties of AlxGa1 xN surfaces exposed to air for different time periods are investigated by atomic force microscopy (AFM), photoluminescence (PL) measurement and X-ray photoelectron spectroscopy (XPS). PL and AFM results show that AlxGa1 xN samples exhibit different surface characteristics for different air-exposure times and Al contents. The XPS spectra of the Al 2p and Ga 2p core levels indicate that the peaks shifted slightly, from an Al–N to an Al–O bond and from a Ga–N to a Ga–O bond. All of these results show that the epilayer surface contains a large amount of Ga and Al oxides