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

In this work, 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 degrees C to 100 degrees C. The current-dependent electroluminescence (EL) spectra, current-voltage (IN) curves and luminescence-current (L-I) curve have been measured to characterize the thermal-related effects on the optoelectrical properties of the InGaN/GaN MQW heterostructures. Experimentally, both the forward voltages decreased with slope of -2.6 mV/K and the emission peak wavelength increased with slope of +4.5 nm/K with increasing temperature, indicating a change in the contact resistance between the metal and GaN layers and the band gap shrinkage effect. With increasing injection current, it has been found the strong current-dependent blueshift of -0.048 nm/mA in EL spectra. It was attributed to not only the stronger band-filling effect but also the enhanced quantum confinement effect, resulted from the piezoelectric polarization and the spontaneous polarization in InGaN/GaN heterostructures. The junction temperature calculated by forward voltage was from 25.6 to 14.5 degrees C and by emission peak shift was from 22.4 to 35.6 degrees C.