We have investigated interfacial characteristics of lattice-matched GaInP/GaAs heterostructures grown by low-pressure organometallic vapor phase epitaxy with constant and variable growth-temperature sequences. The 77 K photoluminescence (PL) measurements were used to confirm the existence of a lower-bandgap interlayer at the GaAs-on-GaInP interface. In the sample grown at 610 degreesC with the constant growth-temperature sequence, only a broad peak was observed at the wavelength longer than that expected from either GaInP or GaAs, while the PL spectrum was dominated by the GaAs near-band-edge emission in the sample grown at 550 degreesC. By inserting a thin 540 degreesC-grown GaInP layer into the GaAs-on-GaInP interface with the variable growth-temperature sequence, the interface-related PL peak was also suppressed completely. (C) 2003 Elsevier Science B.V. All rights reserved.