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Proceedings Paper

Reliability of AlGaN-based deep UV LEDs on sapphire
Author(s): Maxim Shatalov; Zheng Gong; Mikhail Gaevski; Shuai Wu; Wenhong Sun; Vinod Adivarahan; M. Asif Khan
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Paper Abstract

Deep UV LEDs emitting at on 280 nm with powers as high as 1 mW at 20 mA have been reported recently. These devices have mesa size of 100 μm x 100 μm to avoid current crowding due to the high Al-composition of the AlxGa1-xN buffer layers. Small mesa size results in pump current density of 200 A/cm2 for a device current of 20 mA. Small area of p-contact also leads to higher operating voltage and higher thermal impedance for the flip-chip packaged device. These factors limit the device lifetime for 50 % power reduction to only a few hundred hours. From temperature and bias dependent power degradation measurements we found the output power to decay with two characteristic time constants indicating two degradation mechanisms. The faster time constant is bias dependent and temperature independent. The slower time constant varies exponentially with junction temperature having the activation energy of 0.27 eV at 200 A/cm2 pump current density. For the devices with high thermal impedance this degradation mechanism controls the long term power degradation. To increase the device area for better reliability we used the interconnected micro-pixel device design with 10x10 array of 22 μm in diameter pixels. This design allowed for the four-fold increase of the junction area and thereby led to improved reliability performance with the operation life-time for 50 % power reduction of about 1000 hours. In this paper we will present the details of the reliability measurements and use the experimental results to determine possible degradation mechanisms.

Paper Details

Date Published: 22 February 2006
PDF: 11 pages
Proc. SPIE 6134, Light-Emitting Diodes: Research, Manufacturing, and Applications X, 61340P (22 February 2006); doi: 10.1117/12.647204
Show Author Affiliations
Maxim Shatalov, Univ. of South Carolina (United States)
Zheng Gong, Univ. of South Carolina (United States)
Mikhail Gaevski, Univ. of South Carolina (United States)
Shuai Wu, Univ. of South Carolina (United States)
Wenhong Sun, Univ. of South Carolina (United States)
Vinod Adivarahan, Univ. of South Carolina (United States)
M. Asif Khan, Univ. of South Carolina (United States)

Published in SPIE Proceedings Vol. 6134:
Light-Emitting Diodes: Research, Manufacturing, and Applications X
Klaus P. Streubel; H. Walter Yao; E. Fred Schubert, Editor(s)

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