We examined the structural properties of optical modulators consisting of multi-quantum wells and InGaAs relaxed buffer layers grown on (001) GaAs substrates by MBE. The effects of different linearly graded buffer layers was a key component of this study. For all samples, high resolution x-ray techniques determined that the buffer layers were completely relaxed in both [110] directions. The epitaxial layers did not possess any overall crystallographic tilt with respect to the substrate. The strained layer superlattices were pseudomorphic as well. We determined that the crystal quality of multiquantum wells grown on the InGaAs buffers decreases with increasing composition gradient in the underlying buffer layer. The improved material quality correlates with sharper exciton resonance from the more slowly graded samples and suggests that the proximity of the buffer layer strain fields to the active multi-quantum wells plays a significant role in optical and structural properties.