Comparison of two methods for one-dimensional Ga2O3-ZnGa2O4 core–shell heterostructure synthesis

Abstract

While gallium oxide Ga2O3 has recently shown promise as a new ultra-wide bandgap semiconductor in the form of thin films and nanowires (NWs), its widespread applicability is limited due to lack of native p-type conductivity, thus requiring fabrication of heterojunctions. A potential matching material is spinel zinc gallate ZnGa2O4. In this work we demonstrated and compared two novel approaches of one-dimensional Ga2O3-ZnGa2O4 core–shell NW heterostructure preparation: (a) a direct deposition of a ZnGa2O4 coating using a reactive magnetron co-sputtering; (b) annealing of a sacrificial few-nm-thick ZnO coating, deposited via atomic layer deposition, at high temperature to enable solid state reaction between ZnO and Ga2O3. The as-grown nanostructures were characterized via scanning and transmission electron microscopies, X-ray diffraction and X-ray photoelectron spectroscopy. Room temperature optical features were disclosed using photoluminescence and optical absorption. While both methods are viable for production of the heterostructures, smoother and more uniform ZnGa2O4 coating around Ga2O3 NWs was obtained via sacrificial layer conversion in comparison to the sputter-deposited one. These heterostructures could potentially be used for photocatalysis and nanoscale ultra-wide bandgap electronics.