Band Alignments at Polar Nitride Heterojunctions

Aluminum scandium nitride (AlScN) has shown promise for its high-K dielectric properties, enhanced piezoelectricity, and ferroelectricity. For potential applications in high electron mobility transistors (HEMTs), understanding of band alignments at heterojunction interfaces is important. Extracting these values from both first-principles calculations and experiments has proven difficult for the commonly used [0001] direction in wurtzite nitrides due to the presence of spontaneous and piezoelectric polarization fields along that direction. While band alignments have been calculated for non-polar directions, it is not clear how much the orientation affects the results. In this work, we use density functional theory calculations along with a recently developed methodology to control polarization fields in slab calculations [1] to obtain band offsets in the [0001] direction. The method accounts for the polarization effect by passivating slabs with modified pseudo-hydrogen atoms. We apply the approach to an AlN/GaN interface and then to interfaces with AlGaN and AlScN alloys.



[1] S. H. Yoo, M. Todorova, J. Neugebauer, and C. G. Van de Walle, Phys. Rev. Appl. 19, 064037

(2023).