Optical properties and resonant modes in GaN/AlGaN and InGaN/GaN multiple quantum well microdisk cavities

Abstract

Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 angstroms/50 angstroms GaN/AlxGa1-xN (x approximately 0.07) and 45 angstroms/45 angstroms InxGa1-xN/GaN (x approximately 0.15) multiple quantum well structures. Microdisks, approximately 9 micrometers in diameter and regularly spaced every 50 micrometers , were formed by ion beam etch process. Individual disk was pumped from 10 K to 300 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical properties of these microdisks have been studied by picosecond time-resolved photoluminescence (PL) spectroscopy. From cw PL emission spectra, optical modes corresponding to (1) the radial mode type with a spacing of 49 - 51 meV (both TE and TM) and (2) the Whispering gallery mode with a spacing of 15 - 16 meV were observed in the GaN-based microdisk cavities. The spacings of these modes are consistent with theoretical calculation. The implications of our results to III-Nitride microdisk lasers are discussed.