Structural and Band Gap Investigation of GaN:ZnO Heterojunction Solid Solution Photocatalyst Probed by Soft X-ray Spectroscopy

Abstract

We have studied the electronic structure of (Ga1–xZnx)(N1–xOx) as a function of zinc and oxygen concentration (x) using soft X-ray emission (XES) and absorption (XAS) spectroscopy. We have constructed a binding energy model of the compound’s valence band using common metal features found in both N K and O K XES spectra. By comparing the spectra with theoretical DFT models, we determine that our measurements describe an inverted gap heterostructure of GaN and ZnO with two optical gaps characteristic of each phase, 2.6 and 2.8 eV, respectively. We observe a band gap reduction of 0.4 eV across the range of x tested, which is attributed to repulsion between each phase’s conduction band onset due to the proximity of states at the phase interface.