Thermal metrology techniques for UV LED light sources

In this study, we highlight the use of micro-Raman spectroscopy to measure vertical temperature gradients within Light Emitting Diodes (LEDs), ranging from the temperature of the growth substrate, the temperature of regions adjacent to the MQWs, as well as the p-GaN contact layer adjacent to the p-contact metallization. Depth-sensitive micro-Raman temperature measurements are compared with IR spectroscopy temperature measurements, for two types of device architectures. It was found that the temperature rises of the interior layers of the device are higher than those measured by IR thermography. Device peak temperatures shown by IR thermography are also compared to peak temperatures from a thermal finite element analysis (FEA) model for one type of device architecture and were found to agree closely. This study focuses mainly on the thermometry and thermal analysis of Ultraviolet Light Emitting Diodes (UV LEDs) with some additional discussion on blue LEDs.