Gallium Nitride Distributed Feedback Nanowire Lasers
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Nature Nanotechnology
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Proposed for publication in Applied Physics Letters.
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Proposed for publication in Applied Physics Letters.
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Optics Express
We demonstrate stable, single-frequency output from single, asfabricated GaN nanowire lasers operating far above lasing threshold. Each laser is a linear, double-facet GaN nanowire functioning as gain medium and optical resonator, fabricated by a top-down technique that exploits a tunable dry etch plus anisotropic wet etch for precise control of the nanowire dimensions and high material gain. A single-mode linewidth of ∼0.12 nm and >18dB side-mode suppression ratio are measured. Numerical simulations indicate that single-mode lasing arises from strong mode competition and narrow gain bandwidth. © 2012 Optical Society of America.
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Proceedings of SPIE - The International Society for Optical Engineering
Although planar heterostructures dominate current optoelectronic architectures, 1D nanowires and nanorods have distinct and advantageous properties that may enable higher efficiency, longer wavelength, and cheaper devices. We have developed a top-down approach for fabricating ordered arrays of high quality GaN-based nanorods with controllable height, pitch and diameter. This approach avoids many of the limitations of bottom-up synthesis methods. In addition to GaN nanorods, the fabrication and characterization of both axial and radial-type GaN/InGaN nanorod LEDs have been achieved. The precise control over nanorod geometry achiveable by this technique also enables single-mode single nanowire lasing with linewidths of less than 0.1 nm and low lasing thresholds of ∼250kW/cm 2. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
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Proposed for publication in Applied Physics Letters.
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Proposed for publication in ACS Nano.
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Thin Solid Films
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Nano Letters
The deformation, fracture mechanisms, and the fracture strength of individual GaN nanowires were measured in real time using a transmission electron microscope-scanning probe microscope (TEM-SPM) platform. Surface mediated plasticity, such as dislocation nucleation from a free surface and plastic deformation between the SPM probe (the punch) and the nanowire contact surface were observed in situ. Although local plasticity was observed frequently, global plasticity was not observed, indicating the overall brittle nature of this material. Dislocation nucleation and propagation is a precursor before the fracture event, but the fracture surface shows brittle characteristic. The fracture surface is not straight but kinked at (10-10) or (10-11) planes. Dislocations are generated at a stress near the fracture strength of the nanowire, which ranges from 0.21 to 1.76 GPa. The results assess the mechanical properties of GaN nanowires and may provide important insight into the design of GaN nanowire devices for electronic and optoelectronic applications. © 2011 American Chemical Society.
Nano Letters
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Applied Physics Letters
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Optics Express
Vertically aligned InGaN/GaN nanorod light emitting diode (LED) arrays were created from planar LED structures using a new top-down fabrication technique consisting of a plasma etch followed by an anisotropic wet etch. The wet etch results in straight, smooth, well-faceted nanorods with controllable diameters and removes the plasma etch damage. 94% of the nanorod LEDs are dislocation-free and a reduced quantum confined Stark effect is observed due to reduced piezoelectric fields. Despite these advantages, the IQE of the nanorod LEDs measured by photoluminescence is comparable to the planar LED, perhaps due to inefficient thermal transport and enhanced nonradiative surface recombination.
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Although planar heterostructures dominate current solid-state lighting architectures (SSL), 1D nanowires have distinct and advantageous properties that may eventually enable higher efficiency, longer wavelength, and cheaper devices. However, in order to fully realize the potential of nanowire-based SSL, several challenges exist in the areas of controlled nanowire synthesis, nanowire device integration, and understanding and controlling the nanowire electrical, optical, and thermal properties. Here recent results are reported regarding the aligned growth of GaN and III-nitride core-shell nanowires, along with extensive results providing insights into the nanowire properties obtained using cutting-edge structural, electrical, thermal, and optical nanocharacterization techniques. A new top-down fabrication method for fabricating periodic arrays of GaN nanorods and subsequent nanorod LED fabrication is also presented.
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Advanced Materials
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