spds* tight-binding calculation of the local density of states near vacancies in wurtzite GaN

GaN has become ubiquitous in modern technology due in part to its large direct band gap (~3.4eV) which makes it ideal for use in blue LEDs and high field power electronics, as well as its high displacement energy which makes it `naturally’ radiation hardened when compared with Si and GaAs[1]. While there has been significant experimental effort dedicated to the effects of impurities and radiation induced defects at the device level, much less is known about the electronic properties of single defects. We describe an approach to calculating the effects of impurities in bulk crystals by using an spds* (with spin-orbit coupling) tight-binding Green's function formalism. In this approach, the real-space homogeneous Green's functions are constructed by numerically Fourier transforming the k-space propagator. This method has been successfully applied to transition metal impurities in zincblende GaAs [2, 3]. We treat gallium and nitrogen vacancies in wurtzite GaN by perturbatively decoupling the vacancy atomic site from its neighbors and then setting a large onsite potential. We present results for the real-space local density of states as well as topological scans for m- and a-plane wurtzite GaN.

[1]S. J. Pearton and F. Ren, E. Patrick, M. E. Law and A. Y. Polyakov, ECS J. Solid State Sci. Technol. 5, Q35 (2015)

[2]J.-M Tang and M. E. Flatté., PRL 92, 047201 (2004)

[3]J. Bocquel, V. R. Kortan, C. Sahin, R. P. Campion, B. L. Gallagher, M. E. Flatté, and P. M. Koenraad, PRB 87, 075421 (2013)