Scanning electron microscopic (SEM) cathodoluminescence (CL) micrographs of GaxIn1−xP crystals grown from nonstoichiometric melts by a modified Bridgman‐technique reveal a network of lines of reduced luminescence intensity. These lines can be identified by electron microscopic transmission micrographs as subgrain boundaries. Cathodoluminescence spectra of this subgrain boundaries are obtained and the orientation differences of the subgrains are determined by electron channelling patterns.