Samples of V-doped material had been shown to have a high sensitivity for optical processing at 1.5. However, the role which was played by the V dopant was unclear. An electron paramagnetic resonance study was carried out which demonstrated that V was the predominant paramagnetic defect. It pinned the Fermi level, and gave rise to photoconductivity at 1.5. The V was substitutionally incorporated at Cd sites, in concentrations of about 5 x 1016/cm3, and acted as a deep donor with a 2+/3+ level at Ev + 0.8eV. The defect was observed only in the 3+ charge state. The spin Hamiltonian parameters of the V3+ defect were: electron spin = 1, Landé g-factor = 1.962, central hyperfine interaction constant = 0.006/cm, and Cd ligand hyperfine interaction constant = 0.0004/cm.

H.J.Von Bardeleben, J.C.Launay, V.Mazoyer: Applied Physics Letters, 1993, 63[8], 1140-2