title: Measurement of temperature profiles on visible light-emitting diodes by use of a nematic liquid crystal and an infrared laser.
abstract: We present a new technique for measuring the temperature profiles of visible LED chips by use of a nematic liquid crystal with IR laser illumination. The LEDs studied have a multi-quantum-well InGaN/GaN/sapphire structure. New features in this technique are the use of a high-power IR laser beam as the sensing light and the insertion of a color filter in the optical path to block the high-intensity LED light. For the LEDs measured, the conversion efficiency decreases by 70% when the junction temperature rises from 25 to 107 degrees C. This technique is a valuable tool for studying the performance of LEDs as a function of junction temperature.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of California, Irvine, Irvine, California 92697-2625, USA.
authors.forename: Jeong
authors.initials: J
authors.lastname: Park
authors.forename: Moowhan
authors.initials: M
authors.lastname: Shin
authors.forename: Chin C
authors.initials: CC
authors.lastname: Lee