Structure and energy level of native defects in as-grown and electron-irradiated zinc germanium diphosphide studied by EPR and photo-EPR Original Research Article

The properties of defects in as-grown p-type zinc germanium disphosphide (ZnGeP2) and the influence of electron irradiation and annealing on the defect behavior were studied by means of electron paramagnetic resonance (EPR) and photo-EPR. Besides the well-known three native defects (VZn, VP, GeZn), an S=1/2 EPR spectrum with an isotropic g=2.0123 and resolved hyperfine splitting from four equivalent I=1/2 neighbors is observed in electron-irradiated ZnGeP2. This spectrum is tentatively assigned to the isolated Ge vacancy. Photo-EPR and annealing treatments show that the high-energy electron irradiation-induced changes in the EPR intensities of the zinc and phosphorus vacancies are caused by the Fermi level shift towards the conduction band. Annealing of the electron-irradiated samples induces a shift of the Fermi level back to its original position, accompanied by an increase of the EPR signal associated with the VZn− and a proportional increase of the EPR signal assigned to the VP0 under illumination (λ<1 eV) as well as generation of a new defect. The results indicate that the EPR spectra originally assigned to the isolated VZn− and VP0 are in fact associated defects and the new defect is probably the isolated phosphorus vacancy VPi.