Electron paramagnetic resonance of electron-irradiated GaP

An electron paramagnetic resonance (EPR) study of electron-irradiated GaP is presented with emphasis on the properties of the isolated gallium vacancy which can be deduced from its EPR. Further confirmation of the assignment of this spectrum to the vacancy is presented with additional discussion of defect structure. Details of the optical excitation of the EPR-active charge state are given. The vacancy is introduced at a high rate (∼ 1 ${\mathrm{cm}}^{-1\mathrm{}}$) in $p$-type material for electron irradiation at energies of 1-2 MeV. An electron fluence study is reported. High concentrations of isolated vacancies are not found in heavily irradiated $n$-type samples. The vacancy EPR has been observed from 1.4 to 150 K. The vacancy disppears in isochronal annealing studies at temperatures from 300 to 350 °C. Reverse annealing was observed following intense room-temperature laser excitation. A brief discussion of other EPR spectra observed in $e$-irradiated GaP is given.