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

Photoluminescence of deep levels near mid-gap in P-(Cd1-x Zn-x)Te (x approx imate to 0.03-0.05) grown by the vertical gradient freezing method was inve stigated. Correlation with recombination properties manifested by temperatu re dependence of diffusion length of minority electrons and the correspondi ng mobility-lifetime product was studied. Low-temperature photoluminescence (PL) in the spectral range 0.68-1.3 eV and a temperature dependence of dif fusion length of minority electrons (DL) measured by EBIC in the temperatur e range 60-300 K on both as-grown and annealed samples (800 degrees C and 9 00 degrees C) were investigated. We observed, that while as-grown samples e xhibited a steep increase in DL with decreasing temperature in the temperat ure range 60-140 K, annealing and subsequent quenching resulted in a signif icant decrease of DL at these temperatures. Photoluminescence band with a p eak 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-g rown samples with high DL. Luminescence in the approximate to 0.8 eV band i s 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 effe cts of increased recombination manifested by decreased values of DL at temp eratures 60-140 K and detection of the approximate to 0.8 eV PL band was ob served. Reduction of the mobility-lifetime product by increased recombinati on in (CdZn)Te single crystals is therefore probably connected with a prese nce of a V-Cd-related defect. (C) 1999 Elsevier Science B.V. All rights res erved.