Effect of defect clusters on carrier recombination in high-resistivity CdZnTe

Abstract

Carrier recombination in high-resistivity CdZnTe is investigated using the non-contact Defect Specific Photoconductance (DSPC) method that allows for the separation of the photoconductance components associated with recombination at point defects and defect clusters. Unlike photoconductance component controlled by the recombination at point defects that decays exponentially upon cessation of illumination, the component associated with carrier recombination at defect clusters decays logarithmically with time. It is shown that this decay is associated with formation of a Schottky-type depletion space-charge region around the cluster. In high-resistivity CdZnTe the time constant of the logarithmic decay exceeds 1 ms. Reduction of the height of cluster potential barrier with increasing photo-excited excess carrier density increases carrier recombination through the cluster states and leads to its dominance over the recombination through the point defects. At higher carrier injection densities the contribution of the carrier recombination through the clusters exceeds 80% of the total recombination rate.