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Photonics 2018, 5(4), 41; https://doi.org/10.3390/photonics5040041

Effect of Die Shape and Size on Performance of III-Nitride Micro-LEDs: A Modeling Study

STR Group–Soft-Impact, Ltd., 64 Bolshoi Sampsonievskii pr., Bld. E., 194044 St. Petersburg, Russia
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Received: 2 October 2018 / Revised: 22 October 2018 / Accepted: 25 October 2018 / Published: 27 October 2018
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Abstract

Flip-chip truncated-pyramid-shaped blue micro-light-emitting diodes (μ-LEDs), with different inclinations of the mesa facets to the epitaxial layer plane, are studied by simulations, implementing experimental information on temperature-dependent parameters and characteristics of large-size devices. Strong non-monotonous dependence of light extraction efficiency (LEE) on the inclination angle is revealed, affecting, remarkably, the overall emission efficiency. Without texturing of emitting surfaces, LEE to air up to 54.4% is predicted for optimized shape of the μ-LED dice, which is higher than that of conventional large-size LEDs. The major factors limiting the μ-LED performance are identified, among which, the most critical are the optical losses originated from incomplete light reflection from metallic electrodes and the high p-contact resistance caused by its small area. Optimization of the p-electrode dimensions enables further improvement of high-current wall-plug efficiency of the devices. The roles of surface recombination, device self-heating, current crowding, and efficiency droop at high current densities, in limitation of the μ-LED efficiency, are assessed. A novel approach implementing the characterization data of large-size LED as the input information for simulations is tested successfully. View Full-Text
Keywords: micro-LEDs; InGaN; light extraction efficiency; external quantum efficiency; surface recombination; current crowding; self-heating; simulation; optical losses micro-LEDs; InGaN; light extraction efficiency; external quantum efficiency; surface recombination; current crowding; self-heating; simulation; optical losses
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Bulashevich, K.A.; Konoplev, S.S.; Karpov, S.Y. Effect of Die Shape and Size on Performance of III-Nitride Micro-LEDs: A Modeling Study. Photonics 2018, 5, 41.

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