P-type, Be-doped GaInNAs layers (1100 Å thick) are grown on GaAs substrates by gas-source molecular beam epitaxy with a nitrogen radical beam source. High-resolution x-ray rocking curves show that the Ga0.892In0.108NxAs1−x peak shifts closer to the GaAs substrate peak with increasing N concentration, indicating reduced strain. After rapid thermal annealing (RTA) at 700 °C for 10 s, the Ga0.892In0.108As sample suffers strain relaxation, but the N-containing samples remain pseudomorphically strained, suggesting better thermal stability of GaInNAs. The wavelength of room-temperature photoluminescence redshifts from 0.988 to 1.276 μm, due to large band gap bowing, with N concentration increased from 0 to 0.024. Secondary ion mass spectrometry results show no Be diffusion, but hydrogen incorporation alongside N. The free carrier concentration is decreased by one order of magnitude mainly due to H passivation, but after RTA at 700 °C, it is increased to half that of GaInAs due to the reduced H concentration. The product of carrier concentration and Hall mobility is increased from one-tenth to about half that of the GaInAs sample. © 1999 American Institute of Physics.