Optical resonance modes in GaN pyramid microcavities

An array of GaN hexagonal pyramids with a side length of 8.0 mu m was fabri cated by selective epitaxial overgrowth. These microsized pyramids are high ly efficient microcavities. Three types of optical resonance modes with mod e spacings of 10, 5.0, and 6.0 Angstrom were observed when a single pyramid was pumped optically by an intense ultraviolet laser beam. An optical ray tracing method has been developed for calculating the optical resonance mod es inside the pyramid microcavities. It was shown that a single pyramidal c avity can support several different types of optical resonance modes. The c alculated mode spacing agrees very well with the observations. The uniquene ss and advantages of this class of hexagonal pyramidal microcavities over t he other microcavities are discussed. The implications of our finding on th e future GaN microcavity light emitters including micro-light-emitting diod es, microcavity lasers, and vertical-cavity-surface emitting lasers are als o discussed. (C) 1999 American Institute of Physics. [S0003-6951(99)03632-3 ].