We have investigated the photoluminescence and structural properties of GaInNAs/GaAs quantum wells grown by molecular beam epitaxy under different arsenic pressures with all the other fluxes kept constant. The best optical properties are achieved when the V/III beam equivalent pressure ratio (V/IIIBEP) is equal to 10. The emission wavelength remains unchanged for the V/IIIBEP ratios between 8 and 12, suggesting that within this range neither the alloy composition nor the nitrogen sticking coefficient is changed. For V/IIIBEP< 8, incorporation of nitrogen into the crystal is enhanced and for V/IIIBEP> 12 incorporation is reduced. Post-growth thermal annealing induces a spectral blue-shift, which decreases as the V/IIIBEP ratio is increased above 12. This phenomenon is likely due to combined effects of Ga/In interdiffusion and a change in the nearest neighbourhood of nitrogen. (c) 2005 Elsevier B.V. All rights reserved.