The microstructure, local indium composition and photoluminescence in green-emitting InGaN/GaN quantum wells.

In this work, we analyse the microstructure and local chemical composition of green-emitting InxGa1-xN/GaN quantum well (QW) heterostructures in correlation with their emission properties. Two samples of high structural quality grown by metalorganic vapour phase epitaxy (MOVPE) with a nominal composition of x = 0.15 and 0.18 indium are discussed. The local indium composition is quantitatively evaluated by comparing scanning transmission electron microscopy (STEM) images to simulations and the local indium concentration is extracted from intensity measurements. The calculations point out that the measured indium fluctuations may be correlated to the large width and intensity decrease of the PL emission peak. Lay description Recently, extensive research is carried out on indium gallium nitrides alloys for applications in general lighting. The challenge is to incorporate high indium content in indium gallium nitride layer for green emission. In this case, fluctuations of indium are generated because of the large lattice mismatch between gallium nitride and indium nitride. In this paper, we used scanning transmission microscopy to quantify indium in the ternary alloys. The results show that the local indium composition fluctuations in these layers can be correlated with the light emission performance.