InGaAs quantum wells (QWs), with either InP or InGaAsP barriers, are increasingly considered for optoelectronic device applications. Nevertheless, because interdiffusion across the interfaces (intermixing) results in unwanted modifications of the nominal properties, in-situ controls of the well composition (to be ultimately done during the processing sequences) are of fundamental interest. In this work, we have used a single quantum well of InGaAs/InGaAsP as a prototype structure and we investigate the respective advantage (and/or disadvantage) of both PL and Raman tools as non-destructive techniques. Provided careful analyses are done, we find that both determinations are in satisfactory agreement and constitute alternative but non-equivalent techniques for in-line characterization. © 1993.