Transition metal impurities as shallow donors in β−Ga2O3

We present an in-depth investigation of transition-metal impurities (Hf, Zr, Nb and W) as shallow donors in monoclinic using first-principles calculations within the framework of density-functional theory (DFT). A combination of semilocal and hybrid functionals is used to predict their binding energies and hyperfine parameters. The generalized gradient approximation (GGA) allows performing calculations for supercells of up to 2500 atoms, enabling an extrapolation to the dilute limit. The shortcoming of GGA in correctly describing the electron localization is then overcome by the use of the hybrid functional. Results are presented and discussed in light of the application of these transition-metal elements as shallow donors in and their identification in experiment. The methodology applied here can be used in calculations for shallow donors in other systems.