Investigation on defect levels in CdZnTe : Al using thermally stimulated current spectroscopy

Defect levels present in as-grown semi-insulating CdZnTe : Al samples, taken from the top, middle and tail of the same ingot, have been investigated by thermally stimulated current (TSC) spectroscopy. Their trap signatures, particularly the thermal activation energy, capture cross section and concentration, were characterized and discussed, respectively, by fitting the measured TSC spectra with the simultaneous multiple peak analysis method. Furthermore, the deep donor levels EDD from the top, middle and tail were found to be positioned at 0.692 eV, 0.659 eV and 0.618 eV below the conduction band, respectively, by fitting the ln(I) versus 1/kT plots above room temperature. The Fermi level was positioned at 0.716 ± 0.05 eV by fitting the linear plots of the temperature dependence of resistivity, which was pinned by the EDD level near the middle of the band gap, which in turn caused the observed high resistivity in the as-grown CdZnTe : Al ingot.