Ohmic heating of InGaN LEDs during operation: Determination of the junction temperature and its influence on device performance

Heat:generated by ohmic losses is a critical parameter for performance and lifetime of light-emitting diodes (LEDs). The temperature of InGaN MQW LEDs during operation has been investigated depending on the forward current us ing three independent methods. First, the temperature of the active region was derived from the electroluminescence spectra of the devices. Second, te mperature dependent micro-Raman scattering by phonons was used to determine ,the local temperature. Finally a finite element simulation was performed t o get a full temperature profile of the device. While the first method yiel ds the temperature of the active region, the latter two can map the thermal distribution. All three independent methods reveal maximum operation tempe ratures about 120 to 130 degrees C at a forward current of 30 mA, correspon ding to a power density of 705 W cm(-2).