Bulk Ga0.48In0.52NyP1-y and Ga0.92In0.08NyAs1-y were grown on GaAs (001) substrates by gas-source molecular beam epitaxy. Optical and electrical transport properties show great similarities between Ga0.48In0.52NyP1-y and Ga0.92In0.08NyAs1-y. With nitrogen incorporation, the low-temperature photoluminescence (PL) spectra exhibit an asymmetric line shape with a low-energy tail indicating the presence of N-related localized states which dominate the radiative recombination processes. N incorporation significantly reduces the electron mobility and electron concentration. Because N is more electronegative than P or As, N has a tendency to bind the free valence electron of Si. The free electron concentration of N-containing Ga0.48In0.52N0.005P0.995 and Ga0.48In0.52N0.03As0.97 decreases dramatically with high-temperature annealing because Si is passivated by N through the formation of Si-N pairs. (C) 2004 American Vacuum Society.