Confocal Microscopy and TRPL Spectroscopy Study on Spatial Variation of PL in Blue-Emitting InGaN/GaN MQWs

Abstract

Confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) spectroscopy were used to study blue-emitting indium gallium nitride (InGaN)/gallium nitride (GaN) multi-quantum wells grown on c-plane sapphire substrate by metal-organic chemical vapor deposition under different growth conditions. Spatial and spectral variations of photoluminescence (PL) were observed in sub-micrometer scale. Spectrum measurement showed that the bright regions have higher PL intensity as well as smaller PL peak energy than the dark regions. The brightness of CLSM images is related with the PL peak energy difference between bright region and dark region: the larger the energy difference is, the brighter the CLSM image is. TRPL measurement and calculation showed that the effective PL lifetime at bright regions is longer than that at dark regions, and brightness of CLSM images increases with the increment of bright region effective PL lifetime.