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Reliability and degradation modes of 280 nm deep UV LEDs on sapphire

Published online by Cambridge University Press:  01 February 2011

Zheng Gong
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, 301 Main ST, Columbia, SC, 29208, United States
Sameer Chhajed
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
Mikhail Gaevski
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
Wenhong Sun
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
Vinod Advivarahan
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
Maxim Shatalov
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
M. Asif Khan
Affiliation:
[email protected], University of South Carolina, Electrical Engineering, United States
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Abstract

In this paper, we report a study of the degradation of AlGaN-based 280 nm LEDs, which were grown on sapphire substrates using migration-enhanced metalorganic chemical vapor deposition process (MEMOCVD). Electroluminescence (EL), atomic force microscopy (AFM), cathodoluminescence (CL), and scanning electron microscopy (SEM) observations showed that the degradation of deep UV LEDs generally fell into two categories: catastrophic degradation and gradual degradation. The catastrophic degradation was found to be mostly caused by the non-uniformity of surface morphology. The gradual power reduction had two characteristic time constants indicating two possible degradation mechanisms as found from temperature and bias dependent LED power degradation measurements. The faster time constant was bias dependent and virtually constant with temperature whereas the second time constant (slower) varied exponentially with junction temperature. For this temperature dependent part, the activation energies of degradation were determined to be 0.23 eV and 0.27 eV under injected current density of 100 A/cm2 and 200 A/cm2 respectively.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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References

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