27 February 2014 Reduction of efficiency droop in InGaN light-emitting diodes on low dislocation density GaN substrate
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Abstract
A GaN layer of 20 μm thickness grown by the liquid-phase epitaxy on c-plane sapphire was used as a template for the growth of blue light-emitting diodes (LEDs) with emission peak wavelengths of about 450 nm. As the underlying layer of the active region, an InGaN/GaN superlattice or two pairs of 100 nm undoped GaN and 20 nm GaN:Si layers on an n-type GaN:Si layer was found to be effective for reducing the forward voltage. By optimizing the multiple-quantumwell structure, LEDs having a 2.5-nm-thick InGaN well and 5-nm-thick GaN barrier exhibited the highest internal quantum efficiency (IQE) at both low and high currents. This IQE was much higher than that of LEDs on a sapphire substrate. The IQE of LEDs using the liquid-phase GaN grown on sapphire substrate exceeded more than 75% at a forward current density of over 200 A/cm2.
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Kouhei Yamashita, Tomohiko Sugiyama, Makoto Iwai, Yoshio Honda, Takashi Yoshino, Hiroshi Amano, "Reduction of efficiency droop in InGaN light-emitting diodes on low dislocation density GaN substrate", Proc. SPIE 9003, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVIII, 90030E (27 February 2014); doi: 10.1117/12.2038764; https://doi.org/10.1117/12.2038764
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