High‐Performance Enhancement‐Mode β‐Ga 2 O 3 Metal‐Oxide‐Semiconductor Field‐Effect Transistors With Recessed‐Gate and Wet Repair for Monolithic NMOS Inverters

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Recessed‐gate enhancement‐mode (E‐mode) β‐Ga 2 O 3 MOSFETs are demonstrated using a damage‐mitigated process combining plasma etching and a two‐step wet chemical repair. The repair treatment reduces surface roughness of the etched surface from 4.65 nm to 0.52 nm without affecting the recess channel depth. The fabricated (MOSFET) Metal‐oxide‐semiconductor field‐effect transistors exhibits a threshold voltage of 9.6 V, a saturation drain‐current density of 54.7 mA/mm, a low on‐resistance of 151.7 Ω·mm, and a peak transconductance exceeding 8 mS/mm. A high‐quality restored Al 2 O 3 /β‐Ga 2 O 3 interface is suggested from a subthreshold swing of 258.6 mV/dec, an interface trap density of 1.9 × 10 12 cm −2 ·eV −1 , and an on/off ratio above 10 9 . Furthermore, the E‐mode MOSFET is monolithically integrated with a depletion‐mode (D‐mode) β‐Ga 2 O 3 MOSFET to obtain an E/D NMOS inverter, which exhibits a voltage gain of 4.6 and balanced low/high noise margins of 5.5 V/7.4 V. These findings establish a viable route toward high‐performance β‐Ga 2 O 3 logic circuits.