Electron Paramagnetic Resonance Study Of Neutral Mg Acceptors In Beta-Ga2o3 Crystals

Electron paramagnetic resonance (EPR) is used to directly observe and characterize neutral Mg acceptors (Mg-Ga(0)) in a beta-Ga2O3 crystal. These acceptors, best considered as small polarons, are produced when the Mg-doped crystal is irradiated at or near 77K with x rays. During the irradiation, neutral acceptors are formed when holes are trapped at singly ionized Mg acceptors (Mg-Ga(-)). Unintentionally present Fe3+ (3d(5)) and Cr3+ (3d(3)) transition-metal ions serve as the corresponding electron traps. The hole is localized in a nonbonding p orbital on a threefold-coordinated oxygen ion adjacent to an Mg ion at a sixfold-coordinated Ga site. These Mg-Ga(0) acceptors (S = 1/2) have a slightly anisotropic g matrix (principal values are 2.0038, 2.0153, and 2.0371). There is also partially resolved Ga-69 and Ga-71 hyperfine structure resulting from unequal interactions with the two Ga ions adjacent to the hole. With the magnetic field along the a direction, hyperfine parameters are 2.61 and 1.18 mT for the Ga-69 nuclei at the two inequivalent neighboring Ga sites. The Mg-Ga(0) acceptors thermally convert back to their nonparamagnetic Mg-Ga(-) charge state when the temperature of the crystal is raised above approximately 250 K. Published by AIP Publishing.