Valence-band discontinuity between GaN and AIN measured by x-ray photoemission spectroscopy

The valence-band discontinuity at a wurtzite GaN/AIN (0001) heterojunction is measured by means of x-ray photoemission spectroscopy. The method first measures the core level binding energies with respect to the valence-band maximum in both GaN and A1N bulk films. The precise location of the valenceb and maximum is determined by aligning prominent features in the valenceb and spectrum with calculated densities of states. Subsequent measurements of separations between Ga and Al core levels for thin overlayers of GaN film grown on A1N and vice versa yield a valence-band discontinuity of ΔE_v = 0.8+- 0.3 eV in the standard Type I heterojunction alignment.