Improvement of thermal stability of InGaN/GaN multiple-quantum-well by reducing the density of threading dislocations

Three InGaN/GaN multi-quantum well (MQW) samples are grown on c-plane sapphire substrate and free standing GaN substrate, respectively. The emission and structural sproperties of these samples are studied in detail. It is found that the thermal stability and emission homogeneity of InGaN/GaN MQWs grown on GaN substrate is much better than that grown on sapphire substrate. This may be attributed to the lower density of threading dislocations in InGaN/GaN MQW regions grown on GaN substrate. Threading dislocations often end with V-pits at InGaN surface, and often contain In-rich clusters around them. These In-rich regions are easy to segregate during high temperature p-type layer growth, leading to the degradation of InGaN/GaN MQWs ultimately.