Properties of Thin MgO Films on 6H-SiC and GaN: Photoelectron Studies

Properties of MgO layers on p-GaN(0001) and p-6H-SiC(0001) surfaces are studied using X-ray and ultraviolet photoelectron spectroscopy.Up to 5 nm thickness, MgO thin films have been deposited in situ under ultrahigh vacuum by electron beam evaporation.The formation of MgO compound with Mg 2p and O 1s core levels located at 51.0 eV and 531.6 eV, respectively, is confirmed by X-ray photoelectron spectroscopy.The bandgap widths of MgO films determined from the Mg 2p and O 1s losses are estimated to be 6.7 eV and 6.9 eV for MgO layers with a thickness of 5 nm deposited on SiC and GaN substrates, respectively.Valence band maxima of bare substrates and MgO films are found from the ultraviolet spectra.Offsets of the valence and conduction bands have been calculated.Their respective values are 1.9 eV and 1.8 eV for the MgO/SiC interface, and 2.3 eV and 1.2 eV for the MgO/GaN interface.topics: p