Samples of V-doped material were studied by using electron paramagnetic resonance, photo-electron paramagnetic resonance, and optical absorption techniques. The electron paramagnetic resonance results indicated that the V replaced Cd in the oxidation states, V2+ and V3+. Whereas V3+ produced a well-known isotropic electron paramagnetic resonance spectrum. the V2+ spectrum exhibited triclinic symmetry; due to strong Jahn-Teller coupling. Photo electron paramagnetic resonance data showed that the V2+/V3+ donor level was 0.67eV below the conduction band.

P.Christmann, J.Kreissl, D.M.Hofmann, B.K.Meyer, R.Schwarz, K.W.Benz: Journal of Crystal Growth, 1996, 161, 259-63