Dynamic RON Characterization Technique for the Evaluation of Thermal and Off-State Voltage Stress of GaN Switches

GaN power switches provide remarkable performance in terms of power-density, reduced parasitics, and high-thermal handling capability that enable the realization of very efficient and compact dc/dc converters. Despite exhibiting state-of-the-art channel conductivity, GaN high electron mobility transistor (HEMT) devices are affected by the degradation of the dynamic ON-Resistance (R
_ON
) at increasing OFF-state voltages and operative temperatures. In this paper, a novel laboratory setup and characterization procedure for the dynamic R
_ON
of GaN HEMT switches in the presence of thermal- and trapping-effects is presented. The proposed setup allows the study of R
_ON
transients after the switching event at variable off-state voltages and temperatures. The use of custom-designed differential amplification stages and a voltage-controlled current source enables the accurate characterization of R
_ON
even on large periphery devices. At first, the proposed setup is tested with a well-established and mature device technology such as a Si MOSFET. Degradation of the R
_ON
up to 120% due to temperature variation is observed with the presented setup. The setup is then used for the characterization of commercial-grade GaN-on-SiC and GaN-on-Si HEMTs. For both technologies dynamic R
_ON
degradations up to 75% and 20% are observed for temperature and OFF-state voltage variations, respectively. These characterization data are fundamental for the accurate estimation of conduction losses during the design of switching-mode power converters.