Ti- and Fe-related charge transition levels in beta-Ga2O3

Abstract

Deep-level transient spectroscopy measurements on b-Ga2O3 crystals reveal the presence of three defect signatures labeled E2a; E2b, and E3 with activation energies at around 0.66 eV, 0.73 eV, and 0.95 eV below the conduction band edge. Using secondary ion mass spectrometry, a correlation between the defect concentration associated with E3 and the Ti concentration present in the samples was found. Particularly, it is found that E3 is the dominant Ti-related defect in b-Ga2O3 and is associated with a single Ti atom. This finding is further corroborated by hybrid functional calculations that predict Ti substituting on an octahedral Ga site, denoted as TiGaII, to be a good candidate for E3. Moreover, the deep level transient spectroscopy results show that the level previously labeled E2 and attributed to Fe substituting on a gallium site (FeGa) consists of two overlapping signatures labeled E2a and E2b. We tentatively assign E2a and E2b to Fe substituting for Ga on a tetrahedral or an octahedral site, respectively.