This article reviews the state of the art in inversion-type p-channel diamond MOSFETs. We successfully developed the world’s first inversion-channel homoepitaxial and heteroepitaxial diamond MOSFETs. We investigated the dependence of phosphorus concentration (N_P) of the n-type body on field-effect mobility (μ_FE) and interface state density (D_it) for the inversion channel homoepitaxial diamond MOSFETs. With regard to the electrical properties of both the homoepitaxial and heteroepitaxial diamond MOSFETs, they suffer from low μ_FE and one main reason is high D_it. To improve the interface quality, we proposed a novel technique to form OH-termination by using H-diamond followed by wet annealing, instead of the previous OH-termination formed on O-diamond. We made precise interface characterization for diamond MOS capacitors by using the high-low C–V method and the conductance method, providing further insights into the trap properties at Al₂O₃/diamond interface, which would be beneficial for performance enhancement of the inversion-type p-channel diamond MOSFETs. Graphic abstract

Acute kidney injury (AKI) is a frequently occurring severe disease with high mortality. Cystatin C (Cys-C), as a biomarker of early kidney failure, can be used to detect and prevent acute renal injury. In this paper, a biosensor based on a silicon nanowire field-effect transistor (SiNW FET) was studied for the quantitative detection of Cys-C. Based on the spacer image transfer (SIT) processes and channel doping optimization for higher sensitivity, a wafer-scale, highly controllable SiNW FET was designed and fabricated with a 13.5 nm SiNW. In order to improve the specificity, Cys-C antibodies were modified on the oxide layer of the SiNW surface by oxygen plasma treatment and silanization. Furthermore, a polydimethylsiloxane (PDMS) microchannel was involved in improving the effectiveness and stability of detection. The experimental results show that the SiNW FET sensors realize the lower limit of detection (LOD) of 0.25 ag/mL and have a good linear correlation in the range of Cys-C concentration from 1 ag/mL to 1 pg/mL, exhibiting its great potential in the future real-time application.

A normally-off inversion p-channel metal-oxide-semiconductor field-effect transistor (MOSFET) with a nitrogen (N)-doped diamond body deposited using microwave plasma-enhanced chemical vapor deposition (MPECVD) was fabricated. The MOSFET exhibited a drain current density of −1.7 mA/mm. Thus far, this value is similar to the device performance of the inversion p-channel MOSFET fabricated using a phosphorus (P)-doped n-type diamond body. The N₂ used for N-doping is safer than the PH₃ used for P-doping; moreover, the doping concentration is highly controllable. Because the MOSFET, which is a classical electronic device, is driven by a gate voltage, smooth functioning was possible even at a deep donor level. The observed characteristics of the classic MOSFET operating via an N-doped body are crucial for the development of diamond power devices. In this paper, we discuss the significance of the N-doped diamond body and electrical characteristics of the inversion p-channel MOSFET fabricated using an N-doped diamond body.

We employed a high temperature conductance method to investigate the interface state properties of the Al₂O₃/B-doped diamond MOS structure by considering the surface potential fluctuation. Based on Gaussian approximation of Nicollian's model and Brew's graphical approach, we analyzed the frequency dependent characteristics of parallel conductance (G_p/ω–f) at various gate voltages and extracted the energy distribution of interface state density (D_it), capture cross section (σ_p), time constant (τ_it), and the standard deviation of surface potential fluctuation (σ_s). The D_it extracted by the conductance method exhibited good agreement with that by the high-low method, whereas there exist large errors when surface potential fluctuation was not considered by using the conductance method. The capture cross section extracted by the conductance method was on the order of 10⁻¹⁷ cm². From the energy dependence of the interface state time constant, the hole capture and emission follow the Shockley–Read–Hall statistics. σ_s decreases with the energy position away from the valence band edge (E_v) of diamond, indicating that donor-like traps are distributed in the E_v side of diamond.

Silicon nanowire field effect (SiNW-FET) biosensors have been successfully used in the detection of nucleic acids, proteins and other molecules owing to their advantages of ultra-high sensitivity, high specificity, and label-free and immediate response. However, the presence of the Debye shielding effect in semiconductor devices severely reduces their detection sensitivity. In this paper, a three-dimensional stacked silicon nanosheet FET (3D-SiNS-FET) biosensor was studied for the high-sensitivity detection of nucleic acids. Based on the mainstream Gate-All-Around (GAA) fenestration process, a three-dimensional stacked structure with an 8 nm cavity spacing was designed and prepared, allowing modification of probe molecules within the stacked cavities. Furthermore, the advantage of the three-dimensional space can realize the upper and lower complementary detection, which can overcome the Debye shielding effect and realize high-sensitivity Point of Care Testing (POCT) at high ionic strength. The experimental results show that the minimum detection limit for 12-base DNA (4 nM) at 1 × PBS is less than 10 zM, and at a high concentration of 1 µM DNA, the sensitivity of the 3D-SiNS-FET is approximately 10 times higher than that of the planar devices. This indicates that our device provides distinct advantages for detection, showing promise for future biosensor applications in clinical settings.