Accurate Implementation of Gate Resistance Thermometry for GaN HEMTs with a Source Connected Field Plate

Gate resistance thermometry (GRT) is a well-established electrical method that is used to infer the gate metal temperature of GaN high electron mobility transistors (HEMTs). In this work, the effect of the bottom side thermal boundary condition on the calibration of the temperature coefficient of resistance (TCR) and the measurement of the device temperature rise was investigated by applying GRT to a bare device die and an identical device die solder-bonded to a CuMo shim. It was found that the probing location of the thermocouple utilized during the calibration process can result in a 12% difference in the deduction of the TCR. Furthermore, the temperature rise of a GaN HEMT on a bare die with no thermal interface material between the bottom of the device die and the thermal stage could be 2.35 × greater than a same device mounted to a CuMo shim due to wafer bow that results in a large thermal contact resistance. Therefore, proper experimental setup was found to be crucial in order to extract the correct TCR and temperature rise within GaN HEMTs with complex topside geometries where GRT is needed.