Optical resonance modes in InGaN/GaN multiple-quantum-well microring cavities

Microrings of varying sizes have been fabricated from InxGa1-xN/GaN (x simi lar to 0.15) multiple quantum wells (MQWs). Photolithography and dry etchin g techniques including both ion-beam and inductively coupled plasma etching were employed to pattern the III-nitride MQW microrings. Individual micror ings were optically pumped and optical resonance modes were observed. The o bserved mode spacings were consistent with those expected for whispering-ga llery (WG) modes within a resonant cavity of cylindrical symmetry, refracti ve index, and dimensions of the rings under investigation. The results obta ined from the microring cavities were compared with those of the III-nitrid e MQW microdisk cavities. Our results have indicated that resonance modes c orresponding to the radial and the WG modes are simultaneously present in m icrodisk cavities, but only WG modes are available from the microring cavit ies. Implications of our results on future GaN-based microcavity light emit ters have been discussed. (C) 1999 American Institute of Physics. [S0003-69 51(99)04743-9].