The electrical and optical properties of 2.0 MeV electron-irradiated ZnGeP2

Results are presented on the electrical and optical-absorption spectra (hv < Esub(g)) of p-ZnGeP crystals before and after electron irradiation (2 MeV, 300 K), and post-irradiated annealing (300 to 870 K). The defect or impurity level at about (Esub(v) + 0.6) eV (N approximately= 5 x 1017 cm-3) which is responsible for the optical-absorption in the spectral range 0.6 to 1.3 eV is found in initial samples. The enlightment of the samples in the spectral range 0.6 to 1.3 eV is found after electron irradiation and this is connected with the Fermi level moving up to approximately Esub(g)/2 during irradiation. Isochronal annealing experiments indicate three regions of annealing at temperature 410 to 450 K (Esub(a) approximately= 1.1 eV), 480 to 550 K (Esub(a) approximately= 1.4 eV) and 550 to 770 K. It is supposed that the electrical and optical property changes of ZnGeP2 upon electron bombardment are connected with formation of simple point defects [Vsub(Zn)], [Vsub(Ge)], and [Vsub(P)]. (author)