Revisiting Mn-doped Ge using the Heyd-Scuseria-Ernzerhof hybrid functional

We perform a comparative ab initio study of Mn-doped germanium semiconductor using the Perdew-Burke-Ernzerhof exchange-correlation functional, density functional theory (DFT) + U, and Heyd-Scuseria-Ernzerhof hybrid functional (HSE). We show that the HSE functional is able to correctly account for the relevant ground-state properties of the host matrix as well as of the Mn-doped semiconductor. Although the DFT + U and the HSE description are very similar, some differences still remain. In particular, the half metallicity is lost using DFT + U when a suitable U value, tuned to recover the photoemission spectra, is employed. For comparison, we also discuss the case of Mn in silicon.