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Proceedings Paper

Enhanced performance of vertical GaN-based LEDs with a highly reflective ohmic contact and a nano-roughened indium-zinc oxide transparent conduction layer
Author(s): Der-Ming Kuo; Shui-Jinn Wang; Kai-Ming Uang; Tron-Ming Chen; Wei-Chi Lee; Pei-Ren Wang
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Paper Abstract

The use of Polystyrene Spheres (PSs) to realize nano-roughened Indium-Zinc Oxide (IZO) surface and a high reflective ohmic p-contact to improve the optoelectronic properties of larger-area (1×1 mm2) vertical metallic-substrate GaN-based light-emitting diodes (VLEDs) were proposed and investigated. A metal system consisting of annealed- Pt/Al/Pt was employed to serve as a reflector and ohmic contact to p-GaN, which exhibits a good ohmic contact (1.84×10-3 Ωcm2) and high reflectivity (88% at 465 nm). After the removal of sapphire using laser lift-off process (LLO) and etching of u-GaN by ICP, Ti/IZO film was then deposited to serve as a transparent conduction layer (TCL). After that, the polystyrene spheres (PSs) were dispersed on the IZO surface, followed by second sputtering-deposition of IZO film to fill the space between neighboring PSs. The PSs were then removed to form a nano-roughened IZO top-layer. Compared to regular VLEDs with Ni/Au ohmic contact and Ti/Al/Ti/Au as reflector layer, the fabricated VLED shows a typical increase in light output power (i.e., ▵Lop/Lop) by 72.2% at 350 mA and a decrease in forward voltage (Vf) from 3.43 V down to 3.33 V. It is expected that the proposed PSs nano-roughening technology and high reflection annealed- Pt/Al/Pt metal system for ohmic contact to p-GaN would be a potential candidate for the fabrication of high power GaNbased LEDs for solid-state lighting in the near future.

Paper Details

Date Published: 11 February 2010
PDF: 8 pages
Proc. SPIE 7617, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIV, 76170Q (11 February 2010); doi: 10.1117/12.840170
Show Author Affiliations
Der-Ming Kuo, National Cheng Kung Univ. (Taiwan)
Shui-Jinn Wang, National Cheng Kung Univ. (Taiwan)
Kai-Ming Uang, WuFeng Institute of Technology (Taiwan)
Tron-Ming Chen, WuFeng Institute of Technology (Taiwan)
Wei-Chi Lee, National Cheng Kung Univ. (Taiwan)
Pei-Ren Wang, National Cheng Kung Univ. (Taiwan)

Published in SPIE Proceedings Vol. 7617:
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIV
Klaus P. Streubel; Heonsu Jeon; Li-Wei Tu; Norbert Linder, Editor(s)

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