This project implements a time-resolved photoluminescence technique and the related analysis method to study the carrier recombination decay process in heterojunction materials in a non- destructive and contactless fashion. The corresponding "surface velocity" parameter describing the surface and/or interface quality as well as the interface electric field will be determined quantitatively. A quantitative description of the interface quality to determine the interface electric field and to establish the relationship between these material properties and device performance is central to the characterization requirements of compound semiconductor heterojunction materials.