Advances in III-Nitride Microstructures and Micro-Size Emitters

This paper summarizes some of the recent advances in III-nitride microstructures and micro-size emitters made by the author’s group. Microstructures discussed include micro-size disk, ring, and pyramid structures. Optical mode behaviors in these microcavities were probed by optical pumping and measuring the photoluminescence (PL) emission from individual cavities. It was found that the microdisk cavities support both the Whispering Gallery (WG) and the radial modes, while the microring cavities support only the WG type. Micro-size pyramids were also obtained by selective epitaxial overgrowth. It was shown that these pyramids are highly efficient resonators and each pyramidal microcavity is a true 3-D cavity that can support more than three different groups of optical resonance modes. The current injected micro-size LEDs were successfully fabricated from InGaN/GaN quantum wells. It was found that quantum efficiencies in these micro-size LEDs were significantly greater than in conventional broad-area LEDs. A novel light emitting diode (LED) architecture based on interconnecting hundreds of microdisk LEDs was successfully fabricated. It was demonstrated that the emission efficiency was boosted by as much as 50 % in this novel device. The operation of an individually addressable III-nitride microdisk LED array or the first prototype semiconductor microdisplay was also demonstrated. The III-nitride microdisplay can potentially provide unsurpassed performance over those based on the liquid crystal or organic LED technologies. Some of the future trends and challenges facing the III-nitride microcavity photonic devices are also discussed.