The effect of silicon on In GaAsSi/GaAs quantum well structures is investigated using high resolution X-ray diffraction technique (HRXRD). The growth of quantum well is studied by surface electron microscopy (SEM). The surface morphology is studied using atomic force microscopy (AFM). It is observed from the AFM images that the roughness increases as Si doping increases. The incorporation of silicon also induces alloy nonuniformity in the quantum well, leading to an increased surface roughness. We found that the FWHM of the rocking curves of Si-doped InGaAs increase with increasing Si concentration, indicating the degradation of the crystal quality with increasing doping level.