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Published online by Cambridge University Press: 15 February 2011
Single and multi-mode room temperature laser action was observed in GaN pyramids under strong optical pumping. The 5- and 15-micron-wide hexagonal-based pyramids were laterally overgrown on a patterned GaN/AlN seeding layer grown on a (111) silicon substrate by metal-organic chemical vapor deposition. The pyramids were individually pumped, imaged, and spectrally analyzed through a high magnification optical system using a high density pulsed excitation source. We suggest that the cavity formed in a pyramid is of a ring type, formed by total internal reflections of light off the pyramids' surfaces. The mode spacing of the laser emission was found to be correlated to the size of pyramids. The effects of pyramid geometry and pulse excitation on the nature of laser oscillations inside of the pyramids is discussed.