Donor doping of corundum (AlxGa1−x)2O3

Corundum (AlxGa1−x)2O3 alloys have been proposed as a candidate ultrawide-bandgap oxide for a number of applications, but doping is unexplored. We examine the prospects for n-type doping with H, Si, Ge, Sn, Hf, Zr, and Ta in corundum (AlxGa1−x)2O3 alloys using first-principles calculations. All of the dopants are shallow donors in corundum Ga2O3. In the (AlxGa1−x)2O3 alloy, they transition from shallow to deep donors at Al compositions that are unique to each donor. Si and Hf remain shallow donors up to the highest Al contents in corundum (AlxGa1−x)2O3 alloys and are still shallow even as the (AlxGa1−x)2O3 bandgap exceeds 6.5 eV. Finally, we address the detrimental role of cation vacancies as compensating deep acceptors and suggest that doping in a hydrogen-rich environment under cation-rich conditions can be used to overcome this problem.