Nanoscale photoluminescence mapping for MOVPE InN films using scanning near-field optical microscopy (SNOM)

This paper reports for the first time the scanning near-field optical microscopy (SNOM) analysis of MOVPE InN. A near-field PL spectrum and its intensity mapping for MOVPE InN are obtained successfully at room temperature. The near-field PL spectrum has a smaller FWHM and a little higher peak energy compared with the conventional macroscopic PL spectrum. Near-field PL images are used to know the effects of GaN buffer layer on in-plain optical uniformity in MOVPE InN. A large non-uniformity is seen in the image for the sample grown without GaN buffer. Compared with the film grown without buffer, the film grown with a GaN buffer has a better uniformity. Although the use of buffer improves the apparent in-plane uniformity, a fine structure is found in both the PL and topographic images. The fine structure seems to be related to the small grains of InN grown on the GaN buffer composed of small grains.