Hydrogen passivation of GaAs grown on InP substrates by molecular‐beam epitaxy has been performed. Photoluminescence studies show that two peaks at 1.503 and 1.462 eV, which have the luminescence intensities in heteroepitaxial GaAs stronger than that in homoepitaxial GaAs, are effectively passivated by atomic hydrogen. The copper‐arsenic vacancy complex associated recombination is also eliminated after hydrogenation. However, hydrogenation can enhance the intensity of donor toC(As) acceptor transition. In addition, we show that the damaged surface during hydrogenation using rf glow‐discharge method can be passivated by the hydrogenation using photochemical vapor deposition system.