Increased static RON in GaN-on-silicon power transistors under high-side operation with floating substrate conditions

An increase in static on-state resistance (R_ON) is observed in heterojunction field-effect transistors (HFETs) fabricated as GaN-on-silicon devices with floating substrates, when the device is operated at a higher positive bias with respect to the ground, compared to nominal grounded source measurement conditions. This is unlike the widely discussed and reported phenomenon of dynamic R_ON increase during current collapse, where an increase in R_ON is observed only after a high off-state drain bias is applied to the device. These findings are crucial from the point of view of in power electronic circuit applications either as discrete devices or in monolithic integrated circuits. The impact manifests itself as an increased threshold voltage in the HFET and affects its output characteristics, with an impact equivalent to and observed during Si substrate negative back-biasing.