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Sensors 2012, 12(4), 4648-4660; doi:10.3390/s120404648

Precise Temperature Mapping of GaN-Based LEDs by Quantitative Infrared Micro-Thermography

1 Division of Instrument Development, Korea Basic Science Institute, Daejeon 305-333, Korea 2 Medical Device Development, Osong Medical Innovation Foundation, Chungbuk 363-951, Korea
* Author to whom correspondence should be addressed.
Received: 20 February 2012 / Revised: 26 March 2012 / Accepted: 27 March 2012 / Published: 10 April 2012
(This article belongs to the Section Physical Sensors)
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A method of measuring the precise temperature distribution of GaN-based light-emitting diodes (LEDs) by quantitative infrared micro-thermography is reported. To reduce the calibration error, the same measuring conditions were used for both calibration and thermal imaging; calibration was conducted on a highly emissive black-painted area on a dummy sapphire wafer loaded near the LED wafer on a thermoelectric cooler mount. We used infrared thermal radiation images of the black-painted area on the dummy wafer and an unbiased LED wafer at two different temperatures to determine the factors that degrade the accuracy of temperature measurement, i.e., the non-uniform response of the instrument, superimposed offset radiation, reflected radiation, and emissivity map of the LED surface. By correcting these factors from the measured infrared thermal radiation images of biased LEDs, we determined a precise absolute temperature image. Consequently, we could observe from where the local self-heat emerges and how it distributes on the emitting area of the LEDs. The experimental results demonstrated that highly localized self-heating and a remarkable temperature gradient, which are detrimental to LED performance and reliability, arise near the p-contact edge of the LED surface at high injection levels owing to the current crowding effect.
Keywords: infrared; thermography; light-emitting diode (LED); temperature infrared; thermography; light-emitting diode (LED); temperature
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Chang, K.S.; Yang, S.C.; Kim, J.-Y.; Kook, M.H.; Ryu, S.Y.; Choi, H.Y.; Kim, G.H. Precise Temperature Mapping of GaN-Based LEDs by Quantitative Infrared Micro-Thermography. Sensors 2012, 12, 4648-4660.

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