It is shown that hydrogen passivation by the photochemical vapor deposition method can have a significant influence on GaInP/GaAs heterostructures. The effect has been investigated by low-temperature photoluminescence and current-voltage and capacitance-voltage experiments. The photoluminescence measurement shows a strong increase in the luminescence intensity after hydrogenation. It is interpreted in terms of the passivation of nonradiative recombination defect centers by atomic hydrogen. The effect is also accompanied by a simultaneous decrease in the carrier concentration as shown from the capacitance-voltage measurements. In addition, the effect of hydrogenation is confirmed by the improvement of the Schottky-diode properties. These results provide concrete evidence to support the passivation of impurities and defects by atomic hydrogen in GaInP/GaAs heterostructures. (C) 1999 American Institute of Physics. [S0003-6951(99)04310-7].