Interface recombination in GaAs at the GaAs/AlAs interface has been investigated before and after selective ‘‘wet oxidation’’ of the AlAs layer. Time‐resolved photoluminescence of the band‐edge GaAs emission has been used to characterize the interface recombination. Prior to oxidation, the interface recombination is low. After oxidation, the interface recombination has greatly increased, and is comparable to a free GaAs surface in air. However, isolating the GaAs layer from the oxide by a 30 nm layer of Al0.3Ga0.7As allows the interface recombination to remain low after the oxidation. These results help explain the low threshold currents which have been observed in vertical cavity lasers which use wet oxidation of AlAs for current confinement. ©1995 American Institute of Physics.