Excitation transfer between extended band states and N-related localized states in image with x up to 1%

We present time-resolved photoluminescence (PL) results of a series of GaP1-xNx samples with x up to 0.01. The temperature dependence, the concentration dependence as well as the temporal behavior indicate that the PL is dominated by excitation transfer processes between the extended band states and localized N-related states (such as the isolated N-impurity, various N-pair states and higher N-clusters) as well as by excitation transfer between the various localized N-related states themselves. The excitation transfer processes in conjunction with the concentration-dependent statistics of the various N-related states alone are sufficient to explain the observed red-shift of the luminescence of GaP1-xNx with increasing x as well as the spectral dependence of the PL decay times. However, this implies that the PL data alone do not give any conclusive evidence that a hard transformation from an indirect to a direct-gap semiconductor takes place in Ga(N,P) with increasing N up to 2% as often stated.