Strain control and its effect on the optical properties of InGaN/GaN multiple quantum wells

The strain modulation mechanism of green InGaN quantum wells (QWs) was investigated by designing and growing additional InGaN/GaN strain modulation layers with different Indium (In) content and structures. Electroluminescence (EL) measurements were employed to analyze the strain in InGaN QWs by checking the change of EL peak energy with injection current. The experimental results suggest that proper In content in the InGaN strain modulation layer is required to reduce the compression strain in multiple quantum wells (MQWs). Meanwhile, the material quality and flatness of the pre-grown modulation layer may significantly affect the homogeneity and the strain state of MQWs. Temperature-dependent photoluminescence (TDPL) and micro-luminescence were measured to characterize the optical properties of MQWs prepared with strain modulation layers. By carefully modulating the strain in QWs, the InGaN/GaN green multiple quantum wells (MQWs) exhibit higher In incorporation and uniform luminescence.