Establishing Doping Limits for ZnGa2O4 for Ultra Wide Band Gap Semiconductor Applications

ZnGa2O4 is an ultra-wide bandgap oxide with promising applications as a transparent conductor and deep-UV electronic material. Despite this, its transport and doping limits remain poorly defined. Here, we present a comprehensive computational study combining hybrid density functional theory, density functional perturbation theory, and advanced transport modelling. We show that ZnGa2O4 exhibits a dispersive conduction band minimum with a low effective mass (0.27 m0), supporting phonon-limited electron mobilities approaching 500 cm2 V−1 s−1. However, impurity scattering dominates across experimentally relevant carrier concentrations, limiting the achievable mobility to values consistent with state-of-the-art measurements. Temperature-dependent bandgap renormalization due to electron–phonon coupling is quantified and found to be strongly asymmetric between the conduction and valence bands, an effect that is essential to reproduce experimentally observed intrinsic carrier concentrations (∼1 × 10^19 cm−3). Defect calculations reveal that Ga/Zn antisites pin the Fermi level, driving degenerate n-type conductivity under typical growth conditions, while p-type behavior is unlikely due to deep acceptor levels and polaron formation. Screening of extrinsic dopants demonstrates limited potential for further carrier enhancement, with most substitutions yielding high formation energies or deep traps. These findings establish the intrinsic and extrinsic doping limits of ZnGa2O4, highlighting both its potential as a deep-UV transparent conductor and the challenges for further performance optimization.