Near-field scanning optical spectroscopy of an InGaN quantum well

Near-field scanning optical microscopy is used to image photoluminescence (PL) in an InGaN/GaN quantum well (QW) with spatial resolution of approximately 100 nm for temperatures between 50 and 295 K. Strong (similar to 50%) fluctuations in the quantum well photoluminescence as well as a tenfold enhancement of deep level-related emission at lower energies occur at large (similar to 500 nm diam:) pits in the heterostructure. Regions of smaller (similar to 15%) fluctuations in the QW PL are not correlated with the presence of pits. The spectrum of the QW FL shows no significant variations on the length scales probed in this experiment. We thus fin no spectroscopic signature of the recombination of strongly localized carriers at temperatures above 150 K. (C) 1998 American Institute of Physics.