Photoluminescence (PL) characteristics of Se‐doped Ga0.5In0.5P/(Al0.5Ga0.5)0.5In0.5P double heterostructure (DH) on GaAs substrates were investigated at room temperature. The PL intensity and the decay time both strongly depend on the cladding‐layer carrier density. Up to a carrier density of 2.5×1017cm−3, the PL intensity increases linearly with carrier density, while the decay time is almost constant. For carrier densities larger than 2.5×1017cm−3, the PL intensity and the decay time decrease linearly and quadratically with carrier density, respectively. We also studied the PL characteristics of Se‐doped Ga0.5In0.5P and (Al0.5Ga0.5)0.5In0.5P single layers on GaAs substrates. We found that the carrier density dependence of DH governed by the cladding layer is similar to that of (Al0.5Ga0.5)0.5In0.5P single layers. These results indicate that a nonradiative interfacial recombination process dictates the DH PL characteristics and that the quality of the cladding layer affects the PL radiative efficiency. ©1995 American Institute of Physics.