Spatial Inhomogeneity of Photoluminescence in an InGaN-Based Light-Emitting Diode Structure Probed by Near-Field optical Microscopy Under Illumination-Collection Mode

Spatial distribution of photoluminescence (PL) spectra has been assessed in an InGaN single quantum well (SQW)-based light-emitting diode structure by near-field optical microscopy under the illumination-collection mode. The obtained PL mapping image revealed a variation in both peak and intensity of PL spectra according to the probing location with a scale less than about 200 nm. The variation in PL intensity is from 0.8 to 1.8 in arbitrary units indicating that the internal quantum efficiency fluctuates from 10% to 50% within the active layer.