The effect of the low-mole InGaN structure and InGaN/GaN strained layer superlattices on optical performance of multiple quantum well active layers

We report on the effects of both a low-mole InGaN (LMI) structure and an InGaN/GaN strained layer superlattices (SLSs) structure as a buffer layer on the strain relaxation and the optical performance of an InGaN/GaN quantum well (QW) grown on c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). We investigated their structural and optical properties by varying the indium mole fraction, the thickness of InGaN, and the periodicity of the InGaN/GaN SLSs. We found that 300-Å-thick In0.03Ga0.97N LMI and 10 pair In0.1Ga0.9N/GaN (24/40 Å) SLSs were the optimal conditions to reduce the strain of an InGaN/GaN QW. The wavelength shift was reduced to as small as 7 nm for LEDs with In0.1Ga0.9N/GaN SLSs. We speculate that the reduction in the wavelength shift in the In0.1Ga0.9N/GaN SLSs LEDs resulted from the reduction of the strain in the MQW.