1 May 1996 Life tests and failure analysis of AlGaN/InGaN/GaN blue light-emitting diodes
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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 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 at a range of currents up to 70 mA for the remaining 1650 hours, all at a temperature of 23 degrees Celsius. One of the older generation LED's output degraded by more than 50% during the test. The I-V characteristics of this device indicated that there was an ohmic leakage path across the junction which was similar to, but much higher resistance, than was observed on failures from the previous high current tests. The similarity indicates that these LEDs may fail at room temperature and at moderate currents in the same manner as was observed at high currents. Subsequent failure analysis proved that this was not the case, since a crack was found on the degraded LED which isolated part of the active region from the p-contact.
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Daniel L. Barton, Daniel L. Barton, Marek Osinski, Marek Osinski, Christopher J. Helms, Christopher J. Helms, Niel H. Berg, Niel H. Berg, B. Scott Phillips, B. Scott Phillips, } "Life tests and failure analysis of AlGaN/InGaN/GaN blue light-emitting diodes", Proc. SPIE 2693, Physics and Simulation of Optoelectronic Devices IV, (1 May 1996); doi: 10.1117/12.239012; https://doi.org/10.1117/12.239012
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