Detailed investigation of MOCVD-grown [beta]-Ga2O3 through quantitative defect spectroscopies

Ultra-wide bandgap (~ 4.8 eV) beta phase gallium oxide (β-Ga2O3) grown by metal organic chemical vapor deposition (MOCVD) has demonstrated promising electronic transport properties with room temperature electron mobilities reaching 194 cm2/V-s and background doping as low as 9×1014 cm-3 [Zeng et al, Appl. Phys. Lett. 114, 250601 (2019)]. Commensurate with these values is a total trap concentration that is ~10x lower, with a different distribution of states throughout the bandgap than what has been observed for β-Ga2O3 grown by other methods [Zhang et al., Appl. Phys. Lett. 108, 052105 (2016), Farzana et al, Appl. Phys. Lett. 123, 161410 (2018)]. Given the promise of MOCVD-grown β-Ga2O3, a deeper understanding of the nature of defects in this material is of interest. This work provides a comprehensive picture of the current state of knowledge regarding deep levels in MOCVD-grown β-Ga2O3, including trapping properties, energy and concentration distributions in the bandgap, potential physical sources, and comparisons with other growth methods. By applying a suite of complementary defect spectroscopy methods-deep level optical spectroscopy, deep level transient spectroscopy, and admittance spectroscopy, quantitative characterization of defect states within the ~ 4.8 eV bandgap is possible. We find that, through systematically varying growth conditions, differing trends in concentrations for individual states are observed, implying that growth optimization is possible. Combined with observations made after high energy particle irradiation, we can differentiate between states of intrinsic and extrinsic origin.