Spatially resolved photoluminescence in InGaN/GaN quantum wells by near-field scanning optical microscopy

Spatially and spectrally resolved photoluminescence (PL) from InGaN/GaN quantum wells is obtained using near-field scanning optical microscopy (NSOM). Samples displaying high macroscopic PL intensity revealed nonuniform intensity and linewidth but nearly uniform peak position. It suggests that the contrast in the NSOM image reflects nonuniform distribution of dislocations or defects which act as nonradiative recombination centers. The formation of quantum dots with size of 30 +/- 25 nm and their size-dependent interaction with dislocations were observed in plan-view transmission electron microscopy. It is likely that the high luminescence efficiency is due to the efficient localization of excitons in high-density quantum dots located in regions with fewer dislocations. (C) 2001 American Institute of Physics.