Data are presented on the luminescence characteristics of GaAs layers adjacent to native‐oxide regions derived from epitaxial AlGaAs and InAlP films. The native‐oxide ‘‘window’’ layers capping the epitaxial structures are formed by the oxidation of the exposed Al0.9Ga0.1As and In0.48Al0.52P cladding layers. Extensive photoluminescence and time‐resolved photoluminescence studies performed at 300 K show that both the luminescence intensity and lifetime from GaAs ‘‘active regions’’ drop dramatically when the adjacent AlGaAs window layer is oxidized completely. However, there is a marked increase in the efficiency and decay time of the luminescence with the oxidation of InAlP window layers which are grown immediately above the GaAs layer. ©1996 American Institute of Physics.