Thermal stability of InGaN multiple-quantum-well light-emitting diodes on an AlN/sapphire template

摘要

InGaN multiple-quantum-well light-emitting diodes (LEDs) were grown on an AlN/sapphire template by metalorganic chemical vapor deposition. The crystalline quality was investigated by x-ray diffraction and electron-beam-induced current. The thermal stability of the LED was demonstrated by measurements of current-voltage, light output power-current, and electroluminescence (EL) spectra at different temperatures. The output power at 200 mA decreased by 7.3 for the LED on the template upon increasing temperature from 25 to 95℃, while that for the LED on sapphire decreased by 23.9. The peak external quantum efficiency decreased from 0.23 to 0.22 and from 0.15 to 0.10 for the LEDs on the template and on sapphire, respectively. The EL spectrum peak at 20 mA shifted to lower energy by 17.2 meV for the LED on the template upon increasing temperature, while that for the LED on sapphire shifted by 32.7 meV. The LED on the template exhibited a higher output power and a better thermal stability with respect to the conventional LED on sapphire using a low-temperature GaN buffer layer, which is due to the low threading dislocation density in the active layer and the high thermal conductivity of AlN layer.