The In compositional gradation effect on photoluminescence in InGaN/GaN multi-quantum-well structures

Various shapes of InGaN/GaN multi-quantum-well structures were grown by metal-organic chemical vapour deposition in order to investigate the compositional gradation effect on photoluminescence in the vicinity of the InGaN active quantum well region. The photoluminescence spectra at 424 and 435 nm for the symmetrically graded multi-quantum-well structure and the spectrum at 442 nm for the square-type well structure were strongly quenched, indicating the formation of nano-structures. The symmetrically graded multi-quantum-well structure exhibited a relatively short decay lifetime compared to the square-type well structure for the entire range of temperatures. The compositional gradation in the InGaN/GaN multi-quantum-well structure provides the enhanced In fluctuation with the formation of nano-clusters