Photo-excited carrier and space-charge field sub-ns dynamics were investigated in bulk V-doped, and Cl- or As- co-doped, crystals by using a degenerate 4-wave mixing technique. Time-resolved measurements of ps grating decay at various illumination intensities revealed some peculiarities of defect transformation with doping, or under illumination. Novel features in carrier generation and dynamics were observed for the first time and permitted the defect parameters to be deduced. Fast electron capture, and its saturation with increasing illumination intensity were observed in V-doped material and was attributed to the Cd divacancy which was a known deep double acceptor. Numerical modelling, using a two-deep-trap model, permitted the deduction of the concentration and recombination activity of Cd divacancies. An enhancement of the electron generation rate, by a factor of 3 to 4, was found in Cl and V co-doped crystals in spite of a decreased density of donor V states after co-doping. This additional channel of electron generation was attributed to photo-excitation of a DX centre with an activation energy of 1 to 1.2eV.

Role of the charge state of deep vanadium impurities and associations of defects in photoelectric and optical properties of semi-insulating CdTe crystals K.Jarašiūnas, L.Bastienė, J.C.Launay, P.Delaye, G.Roosen: Semiconductor Science and Technology, 1999, 14[1], 48-57