Defect evolution and carrier compensation in high-growth rate MOCVD-grown β-Ga2O3

Beta-phase gallium oxide (β-Ga2O3) grown by metal-organic chemical vapor deposition (MOCVD) using trimethylgallium (TMGa) as the Ga precursor has recently attracted interest as an alternative to triethylgallium (TEGa). This approach enables the high growth rates required for thick drift layers in high-voltage β-Ga2O3 power devices. In comparison with TEGa-based growth, the impact of TMGa on deep-level defect incorporation and carrier compensation remains largely unexplored. Here, deep-level optical and thermal (transient) defect spectroscopies (DLOS and DLTS) measurements made on β-Ga2O3 grown over a systematically varied set of growth conditions reveal a strong effect of TMGa flow rate on the concentration of individual compensating acceptor-like defect states throughout the bandgap. The deep level spectra are significantly dominated by a heretofore unreported state at EC-1.6 eV, whose concentration increases monotonically with TMGa flow rate. Lighted C–V measurements reveal that this new state accounts for more than 90% of the total carrier compensation. Another state at EC-0.6 eV measured using DLTS also monotonically follows the TMGa flow rate but contributes less than 5% of the carrier compensation. The EC-1.6 eV trap concentration tracks the carbon concentration for the growth series measured by secondary ion mass spectroscopy. This trend correlates with density functional theory predictions of carbon-related acceptor transitions near this energy. These results establish the EC-1.6 eV level as the dominant compensating acceptor in MOCVD-grown β-Ga2O3 using TMGa at high growth rates, and they provide guidance for growth optimization to mitigate carrier compensation in the thick drift layers required for high-voltage β-Ga2O3 devices.