Photoluminescence of deep levels in (CdZn) Te-correlation with diffusion length measurement

Photoluminescence of deep levels near mid-gap in P-(Cd(1-x) Zn(x))Te (x approximate to 0.03-0.05) grown by the vertical gradient freezing method was investigated. Correlation with recombination properties manifested by temperature dependence of diffusion length of minority electrons and the corresponding mobility-lifetime product was studied. Low-temperature photoluminescence (PL) in the spectral range 0.68-1.3 eV and a temperature dependence of diffusion length of minority electrons (DL) measured by EBIC in the temperature range 60-300 K on both as-grown and annealed samples (800 degrees C and 900 degrees C) were investigated. We observed, that while as-grown samples exhibited a steep increase in DL with decreasing temperature in the temperature range 60-140 K, annealing and subsequent quenching resulted in a significant decrease of DL at these temperatures. Photoluminescence band with a peak at approx. 0.84 eV in annealed samples with increased recombination and therefore low DL was observed, while no such peak was detected in the as-grown samples with high DL. Luminescence in the approximate to 0.8 eV band is usually attributed to a V(Cd) related defect which is supposed to act as a recombination centre. It can be concluded, that a correlation between effects of increased recombination manifested by decreased values of DL at temperatures 60-140 K and detection of the approximate to 0.8 eV PL band was observed. Reduction of the mobility-lifetime product by increased recombination in (CdZn)Te single crystals is therefore probably connected with a presence of a V(Cd)-related defect. (C) 1999 Elsevier Science B.V. All rights reserved.