Electron paramagnetic resonance and theoretical study of gallium vacancy in β-Ga2O3

Unintentionally doped n-type β-Ga2O3 becomes highly resistive after annealing at high temperatures in oxygen ambient. The annealing process also induces an electron paramagnetic resonance (EPR) center, labeled IR1, with an electron spin of S = 1/2 and principal g-values of gxx = 2.0160, gyy = 2.0386, and gzz = 2.0029 with the principal axis of gzz being 60° from the [001]* direction and gyy along the b-axis. A hyperfine (hf) structure due to the hf interaction between the electron spin and nuclear spins of two equivalent Ga atoms with a hf splitting of ∼29 G (for 69Ga) has been observed. The center can also be created by electron irradiation. Comparing the Ga hf constants determined by EPR with corresponding values calculated for different Ga vacancy-related defects, the IR1 defect is assigned to the double negative charge state of either the isolated Ga vacancy at the tetrahedral site (V2−Ga(I)) or the VGa(I)–Gaib–VGa(I) complex.