Determination of MgO∕GaN heterojunction band offsets by x-ray photoelectron spectroscopy

Abstract

MgO is a promising gate dielectric and surface passivation film for GaN transistors but little is known of the band offsets in the MgO∕GaN system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of MgO∕GaN heterostructures in which the MgO was grown by rf plasma-assisted molecular beam epitaxy on top of thick GaN templates on sapphire substrates. A value of ΔEv=1.06±0.15eV was obtained by using the Ga 3d energy level as a reference. Given the experimental band gap of 7.8eV for the MgO, this would indicate a conduction band offset ΔEC of 3.30eV in this system.