XPS Studies of the Graded Band Gap Al<sub>x</sub>Ga<sub>1-x</sub>N Material Grown by MOCVD

Abstract

To characterize the properties of the as-grown AlxGa1-xN material for producing high property AlxGa1-xN photocathode in ultraviolet (UV) detection, the Ar+ sputtering and X-ray photoelectric spectroscopy (XPS) scan are performed. XPS spectra indicates that although processed with chemical solutions, AlxGa1-xN still contains large amount of carbon and oxide on the surface, which can be completely removed by Ar+ sputtering within few minutes. Ga3d and Al2p curves show that there are other compounds of Ga and Al on the surface but both become very concentrated when sputtering continues. The proportion of Al increases and that of Ga decreases gradually from surface to AlN bulk, which testify the graded band gap profile of the AlxGa1-xN sample. There is always a very slight amount of oxygen in the AlN layer, which is regarded as native element during material growth. At the interface of AlN and sapphire, an abrupt transition appears which can influence the properties of the AlxGa1-xN photocathode when it works with the transmittance mode