The defect energy levels in metalorganic chemical vapor deposition (MOCVD) grown GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S epilayers (x≤0.24) have been studied by photoluminescence (PL) and photoconductivity (PC) measurements. To understand the origin of the observed deep levels, we have determined the temperature dependence of the intensity and half‐width of the dominant deep‐level PL peaks. We find that (1) the dominant deep‐level peaks of the samples grown on the same substrate are related to the epilayer composition, and move to higher energies with increasing gallium content; (2) the dominant deep‐level peaks of the samples with the same epilayer composition grown on different substrates are different. They are attributed to the impurity in the substrate diffusing into the epilayer during MOCVD growth, forming an impurity‐vacancy complex. The following tentative assignments are proposed: the dominant deep‐level peaks in GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S are attributed to the emission of a (V)P‐(Fe)IIIcomplex and a (V)III‐(S)Pcomplex, respectively. Comparing the deep level with the near‐band‐edge emission we show that (1) all deep levels are independent of the band edge asxis varied; (2) the composition dependences of the deep levels associated with such complexes depend on the site occupied by the impurity atom.