We have used secondary ion mass spectrometry and cathodoluminescence spectroscopy to determine the effects that growth and postgrowth conditions have on interdiffusion and near band edge emissions in In0.53Ga0.47As/InP heterojunctions grown by molecular beam epitaxy. This lattice-matched interface represents a model system for the study of atomic movements and electronic changes with controlled anion overlap during growth. Structures subjected to anneals ranging from 440 to 495 degreesC provide a quantitative measure of concentration-driven cross diffusion of group-III and group-V atoms. By measuring anneal-induced broadening at the InGaAs-on-InP interface we have determined an activation energy for As diffusion into InP of similar to2.44 +/- 0.40 eV. An interface layer with Ga-P bonds indicates Ga competes favorably versus As for bonding in the preannealed InP near-surface region. In addition, we present evidence that interface chemical effects manifest themselves electronically as variations of the InGaAs band gap energy. (C) 2004 American Vacuum Society.