Band offsets in the Mg0.5Ca0.5O/GaN heterostructure system

MgCaO offers promise as a gate dielectric for GaN-based metal-oxide-semiconductor (MOS) transistors, particularly in combination with environmentally stable capping layers such as Sc2O3- X-ray photoelectron spectroscopy (XPS) was used to measure the energy discontinuity in the valence band (Delta E-v) Of Mg0.5Ca0.5O/GaN heterostructures in which the MgCaO was grown by rf plasma-assisted molecular beam epitaxy on top of thick GaN templates on sapphire substrates. A value of Delta E-v = 0.65 eV +/- 0.10 eV was obtained by using the Ga 3d energy level as a reference. Given the bandgap of 7.45 eV for the MgCaO, we infer a conduction band offset Delta E-C of 3.36 eV in the Mg0.5Ca0.5O system.