Gate Geometry-Dependent Thermal Impedance of Depletion Mode HEMTs

Although the steady-state thermal behavior of GaN-based high-electron-mobility transistors (HEMTs) has been studied extensively, significantly fewer studies have considered their thermal capacitance. In this article, frequency domain characterization has been employed to extract the thermal impedance of GaN depletion mode HEMTs (D-HEMTs) by using an impedance analyzer. The resulting thermal impedances, when varying the channel length and gate width, are successfully modeled for a frequency domain analysis. A conventional fifth-order geometry-dependent thermal network is proposed for a time domain analysis. Thus, this article presents an experimental tool for determining the gate geometry-dependent thermal resistances and capacitances of D-HEMTs for electrothermal modeling. The thermal resistances are comparable to those obtained with pulsed measurements.