Emerging oxidized silicon-terminated (C-Si-O) diamond field-effect transistors toward industrial applications

Diamond surfaces terminated with a silicon layer (C–Si) can induce a two-dimensional hole gas (2DHG) layer at the insulator/diamond interface, enabling the realization of p-channel metal–oxide-semiconductor field-effect transistors (MOSFETs). Through two primary fabrication routes—namely, SiO2 annealing in a reducing atmosphere and silicon molecular beam deposition (MBD) at high temperatures—stable oxidized silicon-terminated (C–Si–O) and C–Si diamond channels have been realized. These channels facilitate normally-off p-channel FETs with threshold voltages (VTH) ranging from −3 to −16 V and hole mobilities between 100 and 200 cm2/V·s. For instance, a (111)-oriented C–Si–O MOSFET with a VTH of −5.6 V delivers an output current density of −311 mA/mm, whereas another MBD C–Si–O MOSFET with a varying source-to-drain distance (LSD) shows a ΔVTH shift whose magnitude is less than 0.2 V. This review provides a critical overview of the chemical structures, the formation methods, and operational mechanisms of C–Si–O diamond surfaces. It also summarizes recent progress in C–Si–O diamond electronic devices, with emphasis on device architectures, fabrication techniques, and electrical characteristics. Finally, key challenges and potential pathways toward the industrial adoption of this emerging technology are discussed.