Channel Temperature Determination in High-Power AlGaN/GaN HFETs Using Electrical Methods and Raman Spectroscopy

Self-heating in AlGaN/GaN HFETs was investigated using electrical analysis and micro-Raman thermography. Two typically employed electrical methods were assessed to provide a simple means of extracting average channel temperatures in devices. To quantify the accuracy of these electrical temperature measurements, micro-Raman thermography was used to provide submicron resolution temperature information in the source-drain opening of the devices. We find that electrical methods significantly underestimate peak channel temperatures, due to the fact that electrical techniques measure an average temperature over the entire active device area. These results show that, although electrical techniques can be used to provide qualitative comparisons between different devices, they have challenges for the accurate estimation of peak channel temperatures. This needs to be taken into account for lifetime testing and reliability studies based on electrical temperature measurements.