Hybrid functional calculations of $DX$ centers in AlN and GaN

Hybrid functional calculations of $D X$ centers in AlN and GaN

L. Gordon, J. L. Lyons, A. Janotti, and C. G. Van de Walle

Phys. Rev. B 89, 085204 – Published 18 February 2014

Abstract

Using hybrid functional calculations, we investigate the formation of $D X$ centers in GaN and AlN. We find that O, Si, and Ge are shallow donors in GaN, but form stable $D X$ centers in AlN for Fermi-level positions near the conduction band. Using a linear interpolation, we estimate the composition at which the onset of $D X$ behavior will occur in AlGaN alloys. Based on these predictions, we identify Si as the most effective donor for high Al-content AlGaN, and explain a number of seemingly conflicting experimental results for Si-doped AlGaN. Although based on size matching Ge was expected to be superior to Si as a shallow donor, it actually turns out to be more prone to $D X$ -center formation.