Temperature-modulated photoluminescence of GaP: N

We have measured the temperature-modulated photoluminescence of excitons bound to isolated nitrogen and also to nitrogen pairs of different separations. It is shown that temperature modulation can reveal further evidence on the recombination mechanism of bound excitons. The line-shape study of the temperature-modulated spectra indicates the existence of a second-order resonant transition from the $J=2$ state of the bound exciton. Samples heavily doped with nitrogen show temperature-dependent transfer of excitons from one type of nitrogen pair to another.