Photoluminescence spectroscopy of semi-insulating CdZnTe and its correlation to resistivity and photoconductivity

Two CdZnTe samples grown via the Vertical-Gradient-Freeze (VGF) method were studied through low-temperature photoluminescence, room-temperature resistivity and photoconductivity measured by the contactless method. Luminescence of three deep levels EDL1=EC−1.09 eV, EDL2=EC−0.70 eV and EDL3=EC−0.55 eV was observed. Correlation between the optical and the electrical investigation methods suggests the dependence of resistivity on DL3. Photoconductivity and subsequently the charge transport efficiency seem to depend on the occupation of a near midgap level DL2, which is influenced by the position of the Fermi level. A model of the Fermi level shift can be used to evaluate the results of the complementary investigation methods.