Measurement of the valence-band offset at the epitaxial MgO-GaAs(001) heterojunction by x-ray photoelectron spectroscopy

The electronic band structure at the interface of the MgO-GaAs(001) tunnel contact has been experimentally studied. X-ray photoelectron spectroscopy has been used to measure the valence-band offset at the MgO-GaAs(001) heterojunction interface. The valence-band offset ΔEV is determined to be 4.2±0.1eV. As a consequence, a nested “type-I” band alignment with a conduction-band offset of ΔEC=2.2±0.1eV is found. The accurate determination of the valence and conduction band offsets is important for the fundamental understanding of the tunnel spin injection in GaAs.