n-Type Doping of Visible-Light-Absorbing (GaN)1–x(ZnO)x with Aliovalent Sn/Si Substitutions

(GaN)1–x(ZnO)x (GZNO) is a visible-light absorber of interest for solar-driven water splitting. Here, n-type doping of the GZNO solid solution by cation substitution with group IV elements Sn and Si is reported for the first time, which was achieved by nitriding ZnGa-layered double hydroxides with SnO2 or SiO2 colloids. Characterization of Si-(15 at. %, metals basis) and Sn-(3 and 4 at. %) doped analogues of GZNO revealed the formation of solid solutions, which crystallize into a wurtzite-type structure. The local structure of the Sn dopants was investigated by X-ray absorption spectroscopy which was confirmed to be a Sn(IV) center in a 4-coordinated tetrahedral environment. Structural and spectroscopic analyses were suggestive that Si and Sn are both shallow donors in GZNO. Thus, doping of GZNO with group IV elements provides a potential handle to tune the carrier transport properties of GZNO for photoelectrochemical devices.