In situ characterization of InP by integrated photoluminescence has been conducted during processing of high-quality InP/SiO2 structures by electron cyclotron resonance plasma-enhanced chemical vapor deposition. Photoluminescence was used as a tool to control in situ the passivation of III-V semiconductors. A study of the influence of several experi mental parameters revealed that substrate temperature, excitation intensity, and excitation time can all modify photoluminescence. Photoluminescence measurements as a function of excitation intensity were used to study the progressive evolution of the InP surface after several processing steps. The thermal stability of the InP surface, the effect of oxygen plasma treatments, and SiO2 deposition using an oxygen plasma were investigated. Correlations between photoluminescence intensity measured at a fixed intensity on as-grown structures and interfacial electrical properties of the final InP/SiO2 structures as characterized by 1 MHz capacitance-voltage measurements were established. The reported results clearly demonstrate that in situ PL can be used to monitor, with confidence, the interfacial electrical properties of InP/SiO2 structures during the fabrication process.