Effect of Showerhead Gap Position on The Growth of InGaN/GaN MQWs

A series of InGaN/GaN multi-quantum wells(MQWs) samples were grown with four different showerhead gap position using Aixtron 3×2 close-coupled showerhead MOCVD system.In the reactor,the showerhead gap position of 7,13,18 and 25 mm were selected to study the effect of gap position on the growth of InGaN/GaN MQWs.The surface morphology,interface quality of samples were characterized by atomic force microscopy(AFM) and X-ray diffraction(XRD).The results show that the roughness of MQWs decreased and the interfacial structure between InGaN and GaN deteriorated simultaneously with the increasing of the showerhead gap position.The thickness of GaN barrier layer and InGaN well layer also decreased,as well as the In composition.However,when the showerhead gap position was enhanced to a certain level,both the variation in thickness of the MQWs and the In composition were reduced and tended to stay stable.Meanwhile,compared with the thickness variation of barrier layer and well layer,the thickness variation of barrier layer was more remarkable.