Measurement of the thermal impedance of GaN HEMTs using “the 3ω method”

This paper deals with an accurate characterization method dedicated to the determination of the thermal impedance of Gallium Nitride based High Electron Mobility Transistors (GaN HEMTs). The method is inspired by the “3ω method” initially proposed by D.G. Cahill in order to measure the thermal conductivity of bulk materials or layers and our previous works and experiments on the thermal resistance measurements. It is demonstrated that the voltage oscillation at the third harmonic is a real image of the thermal impedance of the device in the frequency domain. Both theoretical approach and test bench are discussed.