Effect of GaN barrier layer thickness on morphology and optical properties of multilayer InGaN quantum dots

Light-emitting diodes based on InGaN have a problem called a green gap. InGaN quantum dots have proven to be a promising structure to solve this problem due to their strong carrier localization effects. In this study, we fabricated InGaN / GaN quantum dots and conventional InGaN / GaN multiple quantum wells by adjusting the growth mode and compared their quantum confinement Stark by intensity-dependent and temperature-dependent photoluminescence measurements. Effects and internal quantum efficiency. The stress modulation effect of GaN barrier layer on multilayer InGaN quantum dots is studied. It is found that as the thickness of GaN barrier layer increases, the stress accumulation phenomenon and the polarization effect caused by stress are weakened, and more importantly, the residual stress is reduced. The density of the non-radiative recombination center in the epitaxial layer is reduced. On the other hand, the temperature-dependent photoluminescence spectrum indicates that the local state in the quantum dot decreases slightly as the thickness of the GaN barrier layer increases, but the carrier can not be trapped by the non-radiative recombination center even if the temperature rises to room temperature.. By analyzing the stress field and the local effect of the carrier, it can be concluded that as the thickness of the GaN barrier layer increases, the main reason for the increase in quantum efficiency in the quantum dot is the decrease in the number of non-radiative recombination centers.