In 0.53 Ga 0.47 As/InP/In 0.53 Ga 0.47 As heterostructures with InP barrier widths between 2 and 20 nm, grown by metal–organic chemical-vapor deposition (MOCVD), were analyzed with respect to interfacial intermixing and As incorporation in the InP. Raman scattering in conjunction with spectroscopic ellipsometry revealed the formation of intermixed (InGa)(AsP) interface layers with a width of about 2 nm. A second effect to be distinguished from interfacial intermixing was detected by the same experimental techniques, namely, the incorporation of As into the InP at an almost constant concentration for InP layer thicknesses up to at least 20 nm. The cross incorporation of As into the InP was attributed to memory effects in the MOCVD growth system.