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 (∼50%) fluctuations in the quantum well photoluminescence as well as a tenfold enhancement of deep level-related emission at lower energies occur at large (∼500 nm diam) pits in the heterostructure. Regions of smaller (∼15%) fluctuations in the QW PL are not correlated with the presence of pits. The spectrum of the QW PL shows no significant variations on the length scales probed in this experiment. We thus find no spectroscopic signature of the recombination of strongly localized carriers at temperatures above 50 K.