Optical modes within III-nitride multiple quantum well microdisk cavities

Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 Angstrom/50 Angstrom GaN/AlxGa1-xN(x similar to 0.07) and 45 Angstrom/45 Angstrom InxGa1-xN/GaN(x similar to 0.15) multiple quantum well structures. Microdisks, approximately 9 mu m in diameter and regularly spaced every 50 mu m, were formed by an ion beam etch process, Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter, Optical modes corresponding to (i) the radial mode type with a spacing of 49-51 meV (both TE and TM) and (ii) the Whispering Gallery mode With a spacing of 15-16 meV were observed in the GaN microdisk cavities. The spacings of these modes are consistent with those expected for modes within a resonant cavity of cylindrical symmetry, refractive index, and dimensions of the microdisks under investigation, The GaN-based microdisk cavity is compared with its GaAs counterpart and implications regarding future GaN-based microdisk lasers are discussed. (C) 1998 American Institute of Physics.