Low energy electron-excited nano-luminescence (LEEN) spectroscopy provides electronic band gap, confined state, and deep level trap information from semiconductor surfaces and interfaces on a nanometer scale. Correlation of luminescence features with their spatial location inside a growth structure-either depth wise or laterally-also provides information on the physical origin and growth dependence of the electronically active defects that form. LEEN spectroscopy of localized states illustrates this approach for a representative set of III-V nitride interfaces, including metal-GaN Schottky barriers, GaN/InGaN quantum wells, GaN ultrathin films, AlGaN/GaN pseudomorphic heterostructures across a single growth wafer, and GaN/Al2O3 interfaces. In each case, electronic properties are sensitive to the chemical composition, bonding, and atomic structures near interfaces and in turn to the specifics of the growth process.