We investigated the relation between interface morphology and recombination-enhanced defect reaction (REDR) phenomena in LI-VI light emitting devices (LEDs) using electroluminescence (EL), atomic force microscopy (AFM) and transmission electron microscopy (TEM). REDR phenomena are observed as nucleation and growth of dark-area defects (DADs) in the EL images. The growth direction of DADs depends on the II/VI ratio, which affects interface morphology and the composition modulation in the alloy layers. We discuss a possible relation between the growth direction of dark defects and interface morphology and/or composition modulation.