Band offset of Al₁−xSixOymixed oxide on GaN evaluated by hard X-ray photoelectron spectroscopy

An Al1−xSixOy mixed oxide has been deposited on GaN by plasma-enhanced atomic layer deposition. The band diagrams between the mixed oxide and GaN for various Si atom fraction x values are determined by hard X-ray photoelectron spectroscopy for the first time. The band gap of the mixed oxide increases with increasing x. This dependence has a large bowing parameter of 1.5 eV. We have successfully obtained conduction band offset (ΔEC) and valence band offset (ΔEV) as a function of x: ΔEC (eV) = 1.6 + 0.4x + 1.2x2 and ΔEV (eV) = 1.7 + 0.34x + 0.36x2. These relationships enable us to design GaN metal–oxide–semiconductor devices using the Al1−xSixOy mixed oxide.