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Proceedings Paper

Development of AlGaN-based deep-ultraviolet (DUV) LEDs focusing on the fluorine resin encapsulation and the prospect of the practical applications
Author(s): Akira Hirano; Yosuke Nagasawa; Masamichi Ippommatsu; Ko Aosaki; Yoshio Honda; Hiroshi Amano; Isamu Akasaki
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Paper Abstract

AlGaN-based LEDs are expected to be useful for sterilization, deodorization, photochemical applications such as UV curing and UV printing, medical applications such as phototherapy, and sensing. Today, it has become clear that efficient AlGaN-based LED dies are producible between 355 and 250 nm with an external quantum efficiency (EQE) of 3% on flat sapphire. These dies were realized on flat sapphire without using a special technique, i.e., reduction in threading dislocation density or light extraction enhancement techniques such as the use of a photonic crystal or a patterned sapphire substrate. Despite the limited light extraction efficiency of about 8% owing to light absorption at a thick p-GaN contact layer, high EQEs of approximately 6% has been reproducible between 300 and 280 nm without using special techniques. Moreover, an EQE of 3.9% has been shown at 271 nm, despite the smaller current injection efficiency (CIE). The high EQEs are thought to correspond to the high internal quantum efficiency (IQE), indicating a small room for improving IQE. Accordingly, resin encapsulation on a simple submount is strongly desired. Recently, we have succeeded in demonstrating fluorine resin encapsulation on a ceramic sheet (chip-on-board, COB) that is massproducible. Furthermore, the molecular structure of a resin with a durability of more than 10,000 h is explained in this paper from the photochemical viewpoint. Thus, the key technologies of AlGaN-based DUV-LEDs having an EQE of 10% within a reasonable production cost have been established. The achieved efficiency makes AlGaN-based DUVLEDs comparable to high-pressure mercury lamps.

Paper Details

Date Published: 15 September 2016
PDF: 13 pages
Proc. SPIE 9926, UV and Higher Energy Photonics: From Materials to Applications, 99260C (15 September 2016); doi: 10.1117/12.2235398
Show Author Affiliations
Akira Hirano, UV Craftory Co., Ltd. (Japan)
Yosuke Nagasawa, UV Craftory Co., Ltd. (Japan)
Masamichi Ippommatsu, UV Craftory Co., Ltd. (Japan)
Ko Aosaki, Asahi Glass Co., Ltd. (Japan)
Yoshio Honda, Nagoya Univ. (Japan)
Hiroshi Amano, Nagoya Univ. (Japan)
Isamu Akasaki, Meijo Univ. (Japan)

Published in SPIE Proceedings Vol. 9926:
UV and Higher Energy Photonics: From Materials to Applications
Gilles Lérondel; Satoshi Kawata; Yong-Hoon Cho, Editor(s)

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