Transfer processes for excitons bound to complex defects in GaP studied by optical detection of magnetic resonance.

Abstract

A comprehensive discussion of relevant transfer processes for excitons bound to complex defects in GaP is presented on the basis of experimental studies by optically detected magnetic resonance (ODMR). A new experimental procedure is applied for determination of the efficiency of the energy migration processes among complex defects in the GaP lattice. The role of phonon interaction in the transfer transitions is discussed, with the example of excitation-energy transfer from shallow donor-acceptor pairs in GaP to excitons bound at complex isoelectronic defects. It is explained that the sign of the sensitizer ODMR signal may relate to the nature of the phonon interaction. The relevant ODMR signal is positive for ``purely'' electronic transitions or for one-site phonon interaction and it may be observed as negative for two-site phonon interactions in the transfer process. The data presented prove the quenching action of the antisite-related complex defects on the GaP visible emission. The mechanism responsible for photoluminescence quenching in this case is shown to be excitation-energy transfer, probably due to phonon-assisted tunneling of bound excitons.