Experimental Benchmarking of Electrical Methods and $\mu $ -Raman Spectroscopy for Channel Temperature Detection in AlGaN/GaN HEMTs

In this paper, several experimental methods (electrical and optical) for channel temperature detection in AlGaN/GaN high-electron mobility transistors have been studied and experimentally benchmarked. This paper encompasses four electrical methods (two dc characterization methods, low-RF output conductance measurement, and gate-resistive sensing technique) and one optical method (micro-Raman spectroscopy), which have been frequently used to sense temperature in AlGaN/GaN transistors. The experiments are carried out on identical test structures on wafer-level conditions as well as on single dies mounted on printed circuit board for power densities up to 12 W/mm. Due to a large temperature distribution along the channel of the devices and due to the physics on which each method is based, it was shown that the differences between the measured temperatures using the different methods can be as high as 50%. Experimental results are discussed and compared with coupled TCAD and finite element modeling simulations, where significant agreements have been observed.