Thermal Simulation and Characterization of GaN HEMT using Gate Resistance Thermometry and Thermoreflectance imaging
Résumé
Two electrical methods and one optical method are used, in order to measure the temperature of the hot spot of a 150nm, 2x150µm GaN HEMT. One of the electrical methods is based on Gate Resistance Thermometry (GTR) [1] and the other one is based on the On State resistance Ron obtained from Id(Vgs,Vds) drain current characterization [2]. The optical one uses the reflectivity variation principle to measure the surface temperature and is based on CCD-thermoreflectance [3]. The measurement results are supported by nonlinear simulation, using Finite Element Method (FEM). The use of the GTR electrical method allows a characterization of the temperature along the gates close to the hot spot region and averages the temperature over the gate width. This method demonstrates a relative linearity in the variation of thermal resistance as function of the applied power dissipation and notably a higher thermal resistance value compared to the conventional way of RON extraction. We may notice that with the On State resistance, the average is realized over the Source-Drain length. The optical method based on the ThermoReflectance (TR) allows a measurement of the surface temperature of the component at the hot spot. The values obtained are consistent with those found by electrical methods and FEM simulation up to 10W/mm.
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