Reaction kinetics in GaP:(Zn,O)

Photoinduced reactions in which pairs of ${\mathrm{Zn}}_{\mathrm{Ga}}$ and ${\mathrm{O}}_{\mathrm{P}}$ ions in GaP dissociate and subsequently re-form are studied. The decay of nearest-neighbor (Zn,O) pair luminescence is measured versus laser power and temperature. The dissociation rate of the pairs is deduced with the use of a model for the electron-hole recombination kinetics which includes the effects of saturation and spatially dependent carrier generation. The activation energy for the photoinduced dissociation is found to be 0.60±0.07 eV. Dissociation of the nearest-neighbor pairs by purely thermal mechanisms is also observed, with an activation energy of 2.6±0.6 eV. From these activation energies and the observed pre-exponential factors, the photoinduced dissociation is determined to be a recombination-enhanced defect reaction. The dissociated nearest-neighbor pairs tend to re-form as pairs with small inter-ion separation.