Photoinduced electron paramagnetic resonance of the phosphorus vacancy in ZnGeP2

The electron paramagnetic resonance (EPR) spectrum of the neutral phosphorus vacancy has been observed in as-grown ZnGeP2 during illumination at liquid-helium temperatures. Without illumination, this donor is a nonparamagnetic singly ionized phosphorus vacancy (VP+ center). Either above-band-gap light (514.5 nm) or below-band-gap light (632.8 nm) can produce the paramagnetic neutral state (VP0 center) of the donor. Principal values of the g matrix for the neutral donor are 1.944, 2.046, and 2.223. The angular dependence of the EPR spectrum suggests that the unpaired spin is unequally shared by two of the zinc ions neighboring the phosphorus vacancy. These phosphorus vacancies are the dominant donor in this highly compensated material, while the previously reported zinc vacancies are the dominant acceptor.