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Studies of Degradation in Nichia AlGaN/InGaN/GaN Blue Light Emitting Diodes Under Close to Normal Operating Conditions

Published online by Cambridge University Press:  10 February 2011

M. Osiński ,
D. L. Barton ,
C. J. Helms ,
P. Perlin ,
N. H. Berg ,
P. Sartori  and
B. S. Phillips
M. Osiński
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87131–6081, USA
D. L. Barton
Affiliation:
Sandia National Laboratories, P.O.Box 5800, Albuquerque, New Mexico 87185–1081, USA
C. J. Helms
Affiliation:
Sandia National Laboratories, P.O.Box 5800, Albuquerque, New Mexico 87185–1081, USA
P. Perlin
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87131–6081, USA
N. H. Berg
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87131–6081, USA
P. Sartori
Affiliation:
Ecole Nationale Sup6rieure des T61communications, Paris, France
B. S. Phillips
Affiliation:
Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87131–6081, USA
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Abstract

The reliability of devices fabricated in GaN and related alloys, especially under high current densities as would be found in lasers, has yet to be fully characterized. Our previous work [1] investigated the degradation of GaN-based blue light emitting diodes (LEDs) under high pulsed current stress. This work indicated a possible correlation between the high crystal defect density and failures caused by metal migration along these defect tubes. To assess the impact of this data on devices under more normal conditions, several LEDs from both older and more recent production lots were placed in a controlled temperature and current environment for several thousand hours. The test started with a constant 20 mA current for the first 1000 hours and continued for another 1650 hours at various currents up to 70 mA, all at a temperature of 23 °C. During this test, one of the older generation LED's output degraded by more than 50%. Subsequent failure analysis showed that this was caused by a crack which isolated part of the active region from the p-contact. The remaining LEDs were returned to life testing where the temperature was subsequently increased by 5 °C after each 500 hours of testing. The output from one of the newer LEDs dreiven at 70 mA degraded to 55% of its original value after 3600 hours and a second newer LED degraded by a similar amount after 4400 hours. The first failure, LED #16, did not exhibit a significant change in its I-V characteristics indicating that a change in the package transparency was a likely cause for the observed degradation. The second failure, LED #17, did show a noticeable change in its I-V characteristics. This device was subsequently returned to life testing where the degradation process will be monitored for further changes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 421: Symposium D – Compound Semiconductor Electronics and Photonics , 1996 , 183
Copyright
Copyright © Materials Research Society 1996

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References

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