Ultrathin gallium nitride passivation layers grown in situ on near-surface InxGa1-xAs/GaAs quantum wells using metalorganic vapour-phase epitaxy (MOVPE) with dimethylhydrazine as nitrogen source are reported. Nitridation of GaAs using DMHy during the post-growth cool-down is also studied. The effect of passivation on the surface recombination rate of quantum well (QW) structures is characterized using low-temperature (10 K) photoluminescence. Measured after growth, the GaN passivation is shown to enhance the PL intensity of the near-surface QWs approximately by a factor of 20. For samples stored in ambient air for 5 months, the enhancement is nearly 10(3). The results suggest that MOVPE-grown thin GaN layers are applicable to GaAs Surface passivation. (C) 2004 Elsevier B.V. All rights reserved.