High-Voltage Normally-off Recessed Tri-Gate GaN Power MOSFETs With Low on-Resistance

In this letter, we present normally-off GaN-on-Si MOSFETs based on the combination of tri-gate with a short barrier recess to yield a large positive threshold voltage (VTH) while maintaining a low specific on resistance (R ON,SP ) and high current density (ID). The trigate structure offered excellent channel control, enhancing VTH from +0.3 V for the recessed to +1.4 V for the recessed tri-gate, along with a much reduced hysteresis in VTH, and a significantly increased transconductance (gm). Additional conduction channels at the sidewalls of the tri-gate trenches compensated the degradation in ON-resistance (R ON ) from the gate recess, resulting in a small R ON of 7.32 ± 0.26 Q·mm for L GD of 15 μm and an increase in the maximum drain current (I max D ). In addition, the tri-gate inherently integrates a gate-connected field-plate (FP), which improved the breakdown voltage (V BR ) and reduced the degradation in dynamic R ON . With proper passivation techniques, these devices could be very promising as high-performance power switches for future power applications.