Abstract
We investigate the junction temperature measurements for GaN-based blue light emitting diodes (LEDs) using nonlinear dependence of the forward voltage (Vf) on temperature. Unlike the conventional linear model of the dependence of Vf on temperature, the modeling of the temperature dependent Vf with a quadratic function showed good agreements with measured data in the temperature range between 20 and 100 °C. Using the proposed quadratic model, the junction temperature and thermal resistance of the measured LED could be accurately determined as the ambient temperature varied. It was observed that the junction temperature increment remained almost unchanged as the ambient temperature increased from 20 to 80 °C, which could be attributed to the interplay between the decrease in series resistance and the increase in non-radiative recombination with increasing temperature. The presented method for accurate determination of the junction temperature is expected to be advantageously employed for the thermal management of high-power LEDs.
Highlights
The demand for light emitting diodes (LEDs) as applied to commercial and residential solid-state lighting, display backlighting, and automobile headlights continues to rise (Chang et al 2012, Pust et al 2015, Cho et al 2017, Bhardwaj et al 2017)
We investigate the junction temperature measurements for GaN-based blue light emitting diodes (LEDs) using nonlinear dependence of the forward voltage (Vf) on temperature
We report on the method for accurate determination of Tj of a GaN-based blue LED package in the temperature range between 20 to 100 oC using nonlinear temperature dependence of the forward voltage
Summary
The demand for light emitting diodes (LEDs) as applied to commercial and residential solid-state lighting, display backlighting, and automobile headlights continues to rise (Chang et al 2012, Pust et al 2015, Cho et al 2017, Bhardwaj et al 2017). The internal quantum efficiency (IQE) of state-of-the art blue LEDs can exceed 90% (Hurni et al 2015, Kuritzky et al 2018, David et al 2020). The IQE of GaN-based blue LEDs may be reduced significantly at high current density and at high temperature, respectively referred to as current droop and thermal droop (David et al 2019, Meneghini et al 2020). Thermal management of LEDs has become increasingly important with the development of high power LEDs. Junction temperature (Tj) is an important parameter which could significantly influence IQE, device reliability, and color stability of LEDs. High electrical power consumption by commercial high-power LEDs results in device heating, making Tj an essential figure of merit that requires a reliable method of measurement. Because of the importance of thermal management in LEDs, Tj of GaN-based LEDs has been intensively studied
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