The Effect of Passive Substrate Terminations on RON Degradation in GaN Bidirectional Switches

In this paper, four passive terminations are considered for the substrate biasing of Gallium Nitride (GaN) bidirectional high-electron-mobility transistors (HEMTs). These substrate networks are analyzed via switching simulations and by adopting a physical model for the bidirectional transistor based on the well-known Advanced SPICE Model (ASM) for GaN HEMT, including an enhanced formulation of back-gating phenomena. The most promising network, which exploits resistances and diodes in the common anode configuration, was implemented with discrete components and tested. The measurement data turned out to be in line with the simulations results in terms of substrate voltage, which is pushed toward zero at low resistance values, thus reducing the back-gating effect. Consequently, a remarkable reduction in the on-resistance (RON) degradation compared to the floating substrate configuration is observed, with a proper trade-off between RON drift and off-state leakage current. Finally, some considerations about the partial recovery of on-resistance due to the substrate termination are discussed.