Valence band offsets of Sc_x Ga_1−x N/AlN and Sc_x Ga_1−x N/GaN heterojunctions

The valence band offsets of Sc_x Ga_1−x N/AlN heterojunctions were measured by x-ray photoelectron spectroscopy (XPS) and were found to increase from 0.42 eV to 0.95 eV as the Sc content x increased from 0 to 0.15. The increase in valence band offset with increasing x is attributed to the corresponding increase in spontaneous polarization of the wurtzite structure. The Sc_x Ga_1−x N/AlN heterojunction is type I, similar to other III-nitride-based heterojunctions. The data also indicate that a type II staggered heterojunction, which can enhance spatial charge separation, could be formed if Sc_x Ga_1−x N is grown on GaN. (paper)