Technologies | Research | Light Generation | Light Extraction | LEDs | Flip-Chip LED | Oct 25, 2019

Chinese Researchers Propose Method to Overcome Low Efficiency of High-Power Flip-Chip LEDs

Chinese scientists from different research centers recently published a co-authored paper on "Highly Efficient GaN-based High-Power Flip-Chip LEDs" in Optics Express Vol. 27, Issue 12, pp. A669-A692 (2019)under the terms of the OSA Open Access Publishing Agreement. High-power flip-chip light-emitting diodes (FCLEDs) suffer from low efficiencies because of poor p-type reflective ohmic contact and severe current crowding, they propose an improvement by using an Ag film.
Abstract:

In this paper, the authors show that it is possible to improve both the light extraction efficiency (LEE) and current spreading of an FCLED by incorporating a highly reflective metallic reflector made from silver (Ag). The reflector, which consists of an Ag film covered by three pairs of TiW/Pt multilayers, demonstrates high reflectance of 95.0% at 460 nm at arbitrary angles of incidence.

The numerical simulation and experimental results reveal that the FCLED with Ag-based reflector exhibits higher LEE and better current spreading than the FCLED with indium-tin oxide (ITO)/distributed Bragg reflector (DBR). As a result, the external quantum efficiency (EQE) of FCLED with Ag-based reflector was 6.0% higher than that of FCLED with ITO/DBR at 750 mA injection current.

The work also suggests that the EQE of FCLED with the Ag-based reflector could be further enhanced 5.2% by replacing the finger-like n-electrodes with three-dimensional (3D) vias n-electrodes, which spread the injection current uniformly over the entire light-emitting active region. This study paves the way towards higher-performance LED technology.

References:

The originl paper is published and under copyright of © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement and can be downloaded at
https://www.osapublishing.org/DirectPDFAccess/111D8DBB-023F-89B8-1F96436CD64D9AF4_412026/oe-27-12-A669.pdf

Credits:

Shengjun Zhou, Xingtong Liu, Han Yan, Zhiwen Chen, Yingce Liu, and Sheng Liu, "Highly efficient GaN-based high-power flip-chip light-emitting diodes," Opt. Express 27, A669-A692 (2019)

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