This article demonstrates that interdiffusion, which is inherent in heteroepitaxy, can be well suppressed by inserting a thin buffer layer grown at sufficiently lower temperature with taking a ZnSe/GaAs heteroepitaxy as an example. Two types of samples are prepared by molecular beam epitaxy (MBE): a 1114 Angstrom thick ZnSe epilayer grown on a 150 Angstrom thick low-temperature ZnSe buffer layer on a GaAs (001) substrate, and a 1356 Angstrom thick ZnSe layer grown directly on GaAs. The composition profile at the heterointerface measured by secondary ion mass spectrometry (SIMS) clearly shows that the Ga diffusion is greatly suppressed in the ZnSe/GaAs system prepared with the low-temperature buffer layers, while considerable Ga interdiffusion from the GaAs substrate into the ZnSe epilayer is observed in the sample without the low-temperature buffer layer. The suppression of interdiffusion is also evidenced by low-temperature photoluminescence (PL) spectroscopy which shows no trace of donor-acceptor pair (DAP) emission at around 2.7 eV normally observed in ZnSe epilayers. In addition to the suppression of interdiffusion, Se reaction with GaAs surfaces is suppressed, which leads to the reduction of built-in defect generation due to heterovalency. Consequently, the ZnSe layer grown on a thin low-temperature ZnSe buffer layer shows high crystallinity as indicated by strong and sharp exciton emission in low-temperature photoluminescence spectrum and narrow X-ray line width. (C) 2003 Elsevier B.V. All rights reserved.