Nanoscopic Photoluminescence Properties of a Green-Emitting InGaN Single Quantum Well on a {20(2)over-bar1} GaN Substrate Probed by Scanning Near-Field Optical Microscopy

Nanoscopic photoluminescence (PL) properties of a green-emitting {20 (2) over bar1} InGaN single quantum well (SQW) are investigated by scanning near-field optical microscopy (SNOM). Carrier/exciton diffusion outside the probe aperture of 150nm is demonstrated by a multimode SNOM technique. The estimated diffusion lengths are similar to 70nm along the [(1) over bar 014] direction and similar to 50nm along the [(1) over bar2 (1) over bar0] direction, and are in between those of (11 (2) over bar2) and (0001) InGaN QWs. This finding is well accounted for by the difference in carrier/exciton lifetimes. Furthermore, atomic force microscopy (AFM) reveals ridge structures along the [(1) over bar2 (1) over bar0] direction. Superimposing the SNOM-PL image with an AFM image, we find a clear correlation between the spatial distributions of PL peak wavelength and surface morphology. (C) 2012 The Japan Society of Applied Physics