First-principles study of possible shallow donors in ZnAl2O4spinel

Abstract

ZnAl${}_{2}$O${}_{4}$ (gahnite) is a ceramic which is considered a possible transparent conducting oxide (TCO) due to its wide band gap and transparency for UV. Defects play an important role in controlling the conductivity of a TCO material along with the dopant, which is the main source of conductivity in an otherwise insulating oxide. A comprehensive first-principles density functional theory study for point defects in ZnAl${}_{2}$O${}_{4}$ spinel is presented using the Heyd, Scuseria, and Ernzerhof hybrid functional (HSE06) to overcome the band gap problem. We have investigated the formation energies of intrinsic defects which include the Zn, Al, and O vacancy and the antisite defects: Zn at the Al site (Zn${}_{\mathrm{Al}}$) and Al at the Zn site (Al${}_{\mathrm{Zn}}$). The antisite defect Al${}_{\mathrm{Zn}}$ has the lowest formation energy and acts as a shallow donor, indicating possible $n$-type conductivity in ZnAl${}_{2}$O${}_{4}$ spinel by Al doping.