NITROGEN CONCENTRATION-DEPENDENCE OF PHOTOLUMINESCENCE DECAY TIME IN GAP1-XNX ALLOYS

We report on the nitrogen concentration dependence of photoluminescenc e (PL) properties in GaP1-xNx alloys. Time-resolved PL measurements re veal that the radiative transition and relaxation processes in GaP1-xN x alloys with high nitrogen concentrations are significantly different from those with low concentrations where NNi lines are clearly observ ed. The PL decay profile shows two distinct exponential processes with fast and slow decay times for high concentrations. With increasing N concentration, the fast decay component becomes dominant and the slow decay time becomes longer. The fast decay is attributed to the relaxat ion to nonradiative recombination centers. The slow decay indicates th e long radiative lifetime due to the weak localization of excitons and the slow relaxation due to the scattered spatial distribution of the states. This is consistent with the fact that the PL occurs at the tai ls of the density of states. (C) 1997 Elsevier Science Ltd.