UC Santa Barbara

Deep-level transient spectroscopy measurements were conducted on He-implanted β-Ga2O3 thin films to study the E4* level, which is a known irradiation-induced defect that is energetically positioned 1.5eV below the conduction band minimum. We find that the formation of E4* after implantation is strongly dependent on a reverse-bias annealing step, where the activation energy for the thermally-activated introduction of E4* is estimated to be ∼2.4eV. Contrary to previous reports, we find, for some of the measured diodes, that the level is stable upon subsequent measurements. From first-principles calculations of the intrinsic defects, we find that the properties of the VO1 and VO3 configurations of the oxygen vacancy closely agree with the experimental observations for the E4* level. A model is suggested where the reverse bias lowers the Fermi-level position in the depletion region of the diode and changes the relative formation energies of the possible configurations of the oxygen vacancy; the formation of E4* then results from an increase in the relative stability of the O1 and O3 configurations of VO.