Confocal microscopy and spectroscopy of InGaN epilayers on sapphire

We report a preliminary investigation of spatial inhomogeneities in an InGa N epilayer using scanning confocal microscopy as the investigative tool. Th e Daresbury confocal microscope SYCLOPS provides simultaneous high quality reflection and fluorescence images of InGaN sample areas up to 500 mu m squ are, even at room temperature. Sample cooling increases the brightness and quality of the fluorescence image, as expected. Spectral selection using in terference filters permits identification of features close to sample edges resulting from the nitridation of indium droplets. The unexpected non-coin cidence of fluorescence and reflection features below 10 mu m in size is te ntatively attributed to the differing absorption strengths of different cry stallites.