Effects of 4° misoriented sapphire substrate on optical property of green InGaN/GaN multiple quantum wells

The effects of 4° misoriented sapphire substrate on optical property of green InGaN/GaN multiple quantum wells (MQWs) grown on planar c-plane sapphire and vicinal cut sapphire substrates were investigated. About an order of magnitude higher photoluminescent intensity of MQWs on vicinal substrate was observed compared to that of MQWs on planar substrate. Atomic force microscope and scanning electron microscope found there was a large number of V-shape pits on the structure grown on vicinal substrate. Result of Raman demonstrated that there was more stress in MQWs structure on planar substrate. It was identified by high-resolution X-ray diffraction and transmission electron microscope that the structure on vicinal substrate had higher crystalline quality. V-shape MQWs grown on semipolar sidewalls of V-shape pits on vicinal substrate played an important role in improving luminescent intensity.