High-resolution PL characterization of impurity segregation and their complex formation on extended defects in CdTe

The peculiarities of impurity complex formation around the extended defects are investigated by high-resolution scanning photoluminescence at 100 K. We have both good spectral resolution for the detailed identification of the various recombination processes (so-called Z-bands at 1.30 and 1.36 eV, self-activated band and band-edge luminescence) and high spatial resolution (<5 mu m) for a definite attribution to extended defects. The broad maxima of the Z-bands' PL profiles correlate with the dislocation etch pits but the width of the profile proves that the Z-recombination mechanism can not be related to the dislocation core itself but to the impurity cloud near the dislocation. When the local concentration of the Z-impurity is further increased a dip arises on the maxima shape of the PL profile. We note that the positions of these dips coincide with the maxima of the self-activation band at 1.45 eV. A mechanism of impurities-complex formation is used to explain the profiles in question.