PL Spatial Variation in InGaN/GaN MQWs Studied by Confocal Microscopy and TRPL Spectroscopy

Abstract

Confocal laser scanning microscopy and time-resolved photoluminescence (TRPL) spectroscopy were used to study blue-emitting InGaN/GaN multiple quantum wells. Spatial and spectral variations of photoluminescence (PL) were observed over submicron-scale regions. Spectral measurements showed that the bright regions have a higher PL intensity as well as smaller peak energy than the dark regions. Correlations among the bright region-dark region PL peak energy difference, the average PL intensity, the PL FWHM, the bright region PL intensity, and the extent of PL intensity fluctuation were observed. As the energy difference increased, the average PL intensity, the PL FWHM, and the bright region PL intensity increased, with a higher degree of areal PL intensity fluctuations. TRPL measurements and calculations showed that the effective PL lifetime at bright regions was longer than that at dark regions, and bright region lifetime increases as energy difference increases, possibly as a result of stronger confinement.