InGaN layers are the heart of green/blue/violet optoelectronic devices. They are not only used as light-emitting quantum wells but also as anti-stressor layers or electron-injecting layers.

The most significant feature of InGaN layers is their tendency to be segregated. The In-rich clusters are very efficient light emitters despite a high dislocation density in heteroepitaxial relaxed structures, but at the same time they are a serious problem in more sophisticated devices, as laser diodes.

This work shows how X-ray diffraction can be used to monitor the In-segregation in the layers. A new simulation program enables us to estimate the range of In-content in thick InGaN layers as well as in the thin quantum wells. The XRD results are well matched with those obtained using transmission electron microscopy, as well as photoluminescecne techniques.