The photoluminescence (PL) characteristic of Ga(NAsP)/(BGa)P quantum well heterostructures pseudomorphically grown on (0 0 1) Si substrates are dominated by the compound semiconductor crystal quality in line with local defects and impurities, but also influenced by the hetero-interface morphology. A comparison of the PL line width of multi-quantum well (QW) structures with different QW thicknesses reveals an increase in line width due to interfacial composition undulation. The degree of interface roughness is related to the N concentration of the active material system. A pronounced decline in PL intensity of the QW material is observed when B and N precursors are simultaneous utilized in the metal organic vapor phase epitaxy growth process. In order to preserve the luminescence efficiency a GaP spacer layer is inserted between each B-containing barrier film and the Ga(NAsP) active material system. The minimum required GaP film thickness is linked to the amount of interface undulation. A GaP spacer width of 3 nm is sufficient to maintain the luminescence intensity of Ga(NAsP)/(BGa)P multi-quantum well heterostructures. (C) 2010 Elsevier B.V. All rights reserved.