A broad optical absorption band with a peak near to 1μm was found in most single crystals. The same crystals exhibited an electron paramagnetic resonance signal which was attributed to singly-ionized Zn vacancies. A direct correlation between the intensity of the optical absorption at 1μm, and the intensity of the electron paramagnetic resonance signal, was established by using a set of crystals in which this absorption varied widely. The results suggested that the singly-ionized Zn vacancy acceptor played a direct role in the electronic transition which was responsible for the 1μm optical absorption. It was also found that illumination with a 632.8nm He-Ne laser at about 25K produced an increase in the absorption at 1μm, and an increase in the Zn-vacancy electron paramagnetic resonance spectrum.

Characterization of Defect-Related Optical Absorption in ZnGeP2 S.D.Setzler, P.G.Schunemann, T.M.Pollak, M.C.Ohmer, J.T.Goldstein, F.K.Hopkins, K.T.Stevens, L.E.Halliburton, N.C.Giles: Journal of Applied Physics, 1999, 85[12], 6677-81