We have investigated annealing ambient effects on optical properties of GaInNAs/GaAs single quantum wells with the use of photoluminescence (PL) spectroscopy sensitive to localization of carriers and photoreflectance (PR) spectroscopy sensitive to the intrinsic band-edge transition. We examined two annealing ambient sequences: tertiarybutylarsine and H-2 in the annealing process and H-2 in the cooling process. The PL efficiency at room temperature is markedly improved in the H-2 ambient annealing process. We found from systematic results of PL and PR spectra that the PL efficiency at room temperature is in connection with the Stokes shift at 10 K, which is a measure of carrier localization, and the broadening factor of the band-edge transition. (C) 2008 Elsevier B.V. All rights reserved.