The effect of junction temperature on the optoelectrical properties of InGaN/GaN multiple quantum well light-emitting diodes |
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Authors: | Jen-Cheng Wang Chia-Hui Fang Ya-Fen Wu Wei-Jen Chen Da-Chuan Kuo Ping-Lin Fan Joe-Air Jiang Tzer-En Nee |
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Institution: | 1. Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan, Republic of China;2. Department of Electronic Engineering, Ming Chi University of Technology, Taishan Dist., New Taipei City 243, Taiwan, Republic of China;3. Department of Digital Technology Design and Graduate School of Toy and Game Design, National Taipei University of Education, Taipei 106, Taiwan, Republic of China;4. Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, Taipei 106, Taiwan, Republic of China |
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Abstract: | Thermal effects on the optoelectrical characteristics of green InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) have been investigated in detail for a broad temperature range, from 30 °C to 100 °C. The current-dependent electroluminescence (EL) spectra, current–voltage (I–V) curves and luminescence intensity–current (L–I) characteristics of green InGaN/GaN MQW LEDs have been measured to characterize the thermal-related effects on the optoelectrical properties of the InGaN/GaN MQW LEDs. The experimental results show that both the forward voltages decreased with a slope of ?3.7 mV/K and the emission peak wavelength increased with a slope of +0.02 nm/K with increasing temperature, indicating a change in the contact resistance between the metal and GaN layers and the existence of a band gap shrinkage effect. The junction temperature estimated from the forward voltage and the emission peak shift varied from 25.6 to 14.5 °C and from 22.4 to 35.6 °C, respectively. At the same time, the carrier temperature decreased from 371.2 to 348.1 °C as estimated from the slope of high-energy side of the emission spectra. With increasing injection current, there was found to be a strong current-dependent blueshift of ?0.15 nm/mA in the emission peak wavelength of the EL spectra. This could be attributed to not only the stronger band-filling effect but also the enhanced quantum confinement effect that resulted from the piezoelectric polarization and spontaneous polarization in InGaN/GaN heterostructures. We also demonstrate a helpful and easy way to measure and calculate the junction temperature of InGaN/GaN MQW LEDs. |
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