Over 10% EQE AlGaN deep-UV LED using transparent p-AlGaN contact layer (Conference Presentation)

Hideki Hirayama; Takayoshi Takano; Jun Sakai; Takuya Mino; Kenji Tsubaki; Noritoshi Maeda; Masafumi Jo; Issei Ohshima; Takuma Matsumoto; Norihiko Kamata

doi:10.1117/12.2254100

19 April 2017 Over 10% EQE AlGaN deep-UV LED using transparent p-AlGaN contact layer (Conference Presentation)

Hideki Hirayama, Takayoshi Takano, Jun Sakai, Takuya Mino, Kenji Tsubaki, Noritoshi Maeda, Masafumi Jo, Issei Ohshima, Takuma Matsumoto, Norihiko Kamata

Author Affiliations +

Proceedings Volume 10104, Gallium Nitride Materials and Devices XII; 101041P (2017) https://doi.org/10.1117/12.2254100
Event: SPIE OPTO, 2017, San Francisco, California, United States

Abstract

AlGaN deep ultraviolet light-emitting diodes (DUV-LEDs) are attracting much attention for a wide variety of applications, however, the efficiency of DUV-LED is still low suppressed by low light-extraction efficiency (LEE). Transparent contact layer is considered to be necessary in order to obtain high LEE in AlGaN DUV LEDs. In this work, we demonstrate over 10% external quantum efficiency (EQE) in an AlGaN DUV-LED by using transparent p-AlGaN contact layer and highly reflective p-type electrode. We fabricated AlGaN quantum well (QW) DUV LEDs with transparent p-AlGaN contact layers on AlN/sapphire templates. EQEs were compared between LEDs with Ni/Al highly reflective electrode and with conventional Ni/Au electrode. The transparency of the p-AlGaN contact layer was confirmed to be more than 97 %. The maximum EQE for 261 nm LEDs with Ni/Al and Ni/Au electrodes were approximately 2 and 3.3%, respectively. We confirmed that the LEE was increased by about 1.7 times. We also fabricated flip-chip (FC) UVC LED module with transparent p-AlGaN contact layer and reflective electrode. The FC LED module was encapsulated to increase LEE. The emission wavelengths were 276 nm. The EQE value under the forward current of 120 mA was increased from 2.7 to 8.6% by increasing an LEE. The output power of approximately 60 mW was obtained under the forward current of 150 mA. The EQE value was maximally increased up to 10.8%. LEE was estimated to be increased from 8.6 % to 25.5 % by introducing LEE enhancement structure.

Conference Presentation

Citation Download Citation

Hideki Hirayama, Takayoshi Takano, Jun Sakai, Takuya Mino, Kenji Tsubaki, Noritoshi Maeda, Masafumi Jo, Issei Ohshima, Takuma Matsumoto, and Norihiko Kamata "Over 10% EQE AlGaN deep-UV LED using transparent p-AlGaN contact layer (Conference Presentation)", Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101041P (19 April 2017); https://doi.org/10.1117/12.2254100

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