Discovery of a Robust P-Type Ultrawide Bandgap Oxide Semiconductor: LiGa₅O₈

LiGa5O8, an ultrawide bandgap semiconductor, is discovered to exhibit p-type conductivity at room temperature, making it the widest bandgap p-type oxide semiconductor known to date. Utilizing a mist-chemical vapor deposition (M-CVD) technique, successful growth of p-type LiGa5O8 thin films on c-plane sapphire and GaN-on-sapphire substrates is achieved. Characterization through X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) confirms the spinel cubic crystal structure of LiGa5O8. Comprehensive investigations into the effects of growth conditions on surface morphology, material composition, and p-type charge carrier transport are conducted. As-grown LiGa5O8 thin films exhibit a broad range of hole concentrations, ranging from 10(15) cm(-3) to 10(18) cm(-3), depending on growth conditions. Elemental compositions of Li, Ga, and O are extracted using X-ray photoemission spectroscopy (XPS). Both Li-poor and Li-rich LiGa5O8 films demonstrate p-type conductivity. Optical absorption measurements reveal the bandgap of LiGa5O8 films to be approximate to 5.36 eV. Additionally, temperature-dependent Hall measurements of the p-type LiGa5O8 thin films show robust p-conductivity down to 150 K. Results from this study promise the advancement of future power electronics based on ultrawide bandgap Ga2O3 and related semiconductor material systems.