High‐Frequency Electron Paramagnetic Resonance and Electron‐Nuclear Double Resonance Spectroscopy Study of the Ga Vacancy in β‐Ga 2 O 3

The Ga vacancy (V Ga ) defect in β‐Ga 2 O 3 , generated by proton irradiation, is studied using high‐frequency electron paramagnetic resonance (EPR) and electron‐nuclear double resonance spectroscopy. The previous X‐band EPR studies of this defect, attributed to V Ga 2− , are extended to higher frequencies (240 GHz) and lower temperatures ( T = 6 K). The spin Hamiltonian parameters of the V Ga 2− center are determined: electron spin S = 1/2, g ‐tensor: g b = 2.0313, g c = 2.0079, and g a = 2.0025; the hyperfine interaction parameters with 2 equivalent Ga neighbors: A b = 14.0 G, A c = 14.6 G, and A a* = 12.8 G for 69 Ga; the superhyperfine interaction with distant Ga neighbors A SHF ( 69 Ga) = 11 MHz; and the quadrupole interaction Q b ( 69 Ga) = 0.32 MHz and Q b ( 71 Ga) = 0.22 MHz. These results shall allow to refine the assignment of this center to a split vacancy or an unrelaxed V Ga 2− defect.