This work presents the results of cathode luminescence (CL) investigations of single layers InGaAsP/InP heterostructures with a composition of a quadruple solid solution at wavelengths of 1. 2 and 1. 5 mu m. The authors previously investigated the effect of noncorrespondence of the parameters of the lattice on the heteroboundary on the defect structure of epitaxial layer. This work investigates heterostructures in which the condition of isoperiodicity is met sufficiently well and the noncorrespondence of the lattice parameters had no great effect on the defect formation process.