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Advances in AlGaN-based Deep UV LEDs

Published online by Cambridge University Press:  01 February 2011

M. H. Crawford
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
A. A. Allerman
Affiliation:
Advanced Material Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
A. J. Fischer
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
K. H. A. Bogart
Affiliation:
Advanced Material Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
S. R. Lee
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
W. W. Chow
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
S. Wieczorek
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
R. J. Kaplar
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
S. R. Kurtz
Affiliation:
Semiconductor Material and Device Sciences Department, Sandia National Laboratories, Albuquerque, NM 87185, USA
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Abstract

Materials studies of high Al-content (> 30%) AlGaN epilayers and the performance of AlGaN-based LEDs with emission wavelengths shorter than 300 nm are reported. N-type AlGaN films with Al compositions greater than 30% reveal a reduction in conductivity with increasing Al composition. The reduction of threading dislocation density from the 1–5 × 1010 cm-2 range to the 6–9 × 109cm-2 range results in an improvement of electrical conductivity and Al0.90Ga0.10N films with n= 1.6e17 cm-3 and μ=20 cm2/Vs have been achieved. The design, fabrication and packaging of flip-chip bonded deep UV LEDs is described. Large area (1 mm × 1 mm) LED structures with interdigitated contacts demonstrate output powers of 2.25 mW at 297 nm and 1.3 mW at 276 nm when operated under DC current. 300 μm × 300 μm LEDs emitting at 295 nm and operated at 20 mA DC have demonstrated less than 50% drop in output power after more than 2400 hours of operation. Optimization of the electron block layer in 274 nm LED structures has enabled a significant reduction in deep level emission bands, and a peak quantum well to deep level ratio of 700:1 has been achieved for 300 μm × 300 μm LEDs operated at 100 mA DC. Shorter wavelength LED designs are described, and LEDs emitting at 260 nm, 254nm and 237 nm are reported.

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Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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