Assessment of large critical electric field in ultra-wide bandgap p-type spinel ZnGa₂O₄

Abstract

The spinel Zinc Gallate ZnGa2O4 stands out among the emerging ultra-wide bandgap (~5eV) semiconductors as the ternary complex oxide with the widest gap where bipolar conductivity (electrons and holes) has been demonstrated. For power and energy electronic applications, a fundamental property of the material is its critical electric field (Ec), as, for example, the Baliga’s figure of merit scales as ~Ec3. However, the critical electric field of ZnGa2O4 is yet unknown. In this work, it is carried out with the thermodynamic analysis of point defects and free carriers versus oxygen pressure. According to this analysis, highly resistive p--type ZnGa2O4 thin films on sapphire and Si substrates were elaborated by metal organic chemical vapor deposition (MOCVD) technique. Hall Effect measurements confirmed a low carrier level at room temperature (estimated at 1011 cm-3), and breakdown voltage characterizations on a polycrystalline thin film on p--type doped silicon substrates have been performed. We can deduce a value of the critical electric field to be at least 5.3 MV/cm for p--type ZnGa2O4.