Photoluminescence and photocurrent were used to study the effect of interlayer such as diffusion-suppressing layer (DSL) and strained compensating layer (SCL) on optical properties of InGaAsN/GaAs quantum well grown by metal organic chemical vapor deposition (MOCVD). The photoluminescence peaks showed a red shift due to strain gap energy decreasing by adding SCL, and it also showed an improved photoluminescence intensity by inserting both DSL and SCL layers. Moreover, the peaks observed in photocurrent spectra were preliminarily assigned to the fundamental of excitonic transition. Two additional transitions related to the SCL region and DSL region were observed clearly. The result indicated that a higher density of indium diffusion into the barrier which influences crystallite interface quality was suppressed. It was explained by using diffusion calculation for our optimum samples. (C) 2004 Elsevier B.V. All rights reserved.