The effect of junction temperature on the optoelectrical properties of InGaN/GaN multiple quantum well light-emitting diodes

• Main Authors: Jen Hsuan Wang, 王仁炫
• Other Authors: T. E. Nee
• Format: Others
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/59490833073094035706

碩士 === 長庚大學 === 電子工程學系 === 99 === 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 C to 14.5 C and from 22.4 C to 35.6 C, respectively. At the same time, the carrier temperature decreased from 371.2 C 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 theemission 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.