Steady-State Dynamic R_ON Measurements of GaN HEMTs: Role of Voltage-and Temperature-Dependent Time Constants

Steady-state measurements of the dynamic ON-resistance (RON) in GaN high-electron-mobility transistors (HEMTs) are cruicial due to the presence of slow charge trapping processes. This is often overlooked by most circuit-level studies, which fail to represent realistic steady-state operations and hinder direct comparison between different GaN technologies. In this work, we propose a steady-state, time-resolved dynamic RON characterization methodologyspanning the μs-to-minute scale, enabling accurate evaluation of Schottky-type (GaN-1) and Ohmic-type (GaN-2) p-GaN gate HEMTs under realistic hard- and soft-switching conditions up to 200 kHz. We reveal the role of different trapping time constants, which can exceed 10 min, along with their voltage and temperature dependencies. For GaN-1, we identify two OFF-state trapping processes: a fast μs-scale process correlated with drain-bias-induced threshold voltage shift and its partial recovery; a slow, thermally activated process with an activation energy of 0.34 eV that closely follows OFF-state leakage behavior. Finally, fast de-trapping processes in GaN-2 driven by gate-side and drain-side hole injection are identified, explaining its superior steady-state performance. These findings clarify the distinct trapping time scales and are important for understanding and optimizing GaN HEMT performance for efficient power conversion.