EXCITATION AND RECOMBINATION OF DONOR-ACCEPTOR PAIRS IN ZNTE

The photoluminescence spectra and its excitation spectra of the donor‐acceptor pairs are observed in ZnTe crystals doped with Li and As in the region below the bandgap energy. The relaxation of electrons and holes into the first excited state of d‐a paris is studied for the three excitation processes: (1) bound‐to‐bound transitions, (2) bound‐to‐free transitions, and (3) free‐to‐free transitions. It is concluded that most of the electrons and holes at the excited states of each impurity level are relaxed rapidly into their ground states before the occurrence of the recombination involving the excited states. For the excitation process (2), conduction electrons are preferentially trapped by positively charged pairs. The redistribution of bound holes by hopping is suggested to explain the broad d– a emission band observed for the bound‐to‐free excitation for very distant pairs. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA