Reconfigurable Cascaded Thermal Neuristors for Neuromorphic Computing.

While the complementary metal-oxide semiconductor (CMOS) technology is the mainstream for the hardware implementation of neural networks, an alternative route is explored based on a new class of spiking oscillators called "thermal neuristors", which operate and interact solely via thermal processes. Utilizing the insulator-to-metal transition (IMT) in vanadium dioxide, a wide variety of reconfigurable electrical dynamics mirroring biological neurons is demonstrated. Notably, inhibitory functionality is achieved just in a single oxide device, and cascaded information flow is realized exclusively through thermal interactions. To elucidate the underlying mechanisms of the neuristors, a detailed theoretical model is developed, which accurately reflects the experimental results. This study establishes the foundation for scalable and energy-efficient thermal neural networks, fostering progress in brain-inspired computing.

A complementary low-Schottky-barrier S/D-based nanoscale dopingless bidirectional reconfigurable field effect transistor with an improved forward current.

In this paper, a nanoscale dopingless bidirectional RFET (BRFET) is proposed. Unlike conventional BRFETs, the proposed BRFET uses two different metal materials to form two different types of Schottky barriers on the interface between the S/D and silicon. For one of the two metal forms, the Schottky barrier height between the conduction band of the semiconductor and one of the two metal materials is lower than half of the energy band gap. The Schottky barrier height between the valence band of the semiconductor and the other kind of the two metal materials is lower than half of the energy band gap of the semiconductor. Therefore, a complementary low Schottky barrier (CLSB) is formed. Therefore, more carriers from the source electrode can easily flow into the semiconductor region through thermionic emission in both n-mode and p-mode compared to conventional BRFET operation, which generates carriers through the band-to-band tunneling effect. Therefore, a larger forward current can be achieved by the proposed CLSB-BRFET. The performance of the CLSB-BRFET is investigated by device simulation and compared with that of the BRFET. The working principle is interpreted through an analysis based on energy band theory. The output characteristics and reconfigurable function are also investigated and verified.

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links.

The forthcoming sixth generation (6G) communication network is envisioned to provide ultra-fast data transmission and ubiquitous wireless connectivity. The terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great potential for 6G wireless technologies. However, the THz links suffers from high loss and line-of-sight connectivity. To overcome these challenges, a cost-effective method to dynamically optimize the transmission path using reconfigurable intelligent surfaces (RISs) is widely proposed. RIS is constructed by embedding active elements into passive metasurfaces, which is an artificially designed periodic structure. However, the active elements (e.g., PIN diodes) used for 5G RIS are impractical for 6G RIS due to the cutoff frequency limitation and higher loss at THz frequencies. As such, various tuning elements have been explored to fill this THz gap between radio waves and infrared light. The focus of this review is on THz RISs with the potential to assist 6G communication functionalities including pixel-level amplitude modulation and dynamic beam manipulation. By reviewing a wide range of tuning mechanisms, including electronic approaches (complementary metal-oxide-semiconductor (CMOS) transistors, Schottky diodes, high electron mobility transistors (HEMTs), and graphene), optical approaches (photoactive semiconductor materials), phase-change materials (vanadium dioxide, chalcogenides, and liquid crystals), as well as microelectromechanical systems (MEMS), this review summarizes recent developments in THz RISs in support of 6G communication links and discusses future research directions in this field.

A Polarization-Switching, Charge-Trapping, Modulated Arithmetic Logic Unit for In-Memory Computing Based on Ferroelectric Fin Field-Effect Transistors.

Nonvolatile logic devices are crucial for the development of logic-in-memory (LiM) technology to build the next-generation non-von Neumann computing architecture. Ferroelectric field-effect transistors (Fe FET) are one of the most promising candidates for LiMs because of high compatibility with mainstream silicon-based complementary metal-oxide semiconductor processes, nonvolatile memory, and low power consumption. However, because of the unipolar characteristics of a Fe FET, a nonlinear XOR or XNOR logic gate function is difficult to realize with a single device. In addition, because single Fe polarization switch modulation is available in the devices, a reconfigurable logic gate usually needs multiple devices to construct and realize fewer logic functions. Here, we introduced polarization-switching (PS) and charge-trapping (CT) effects in a single Fe FET and fabricated a multi-field-effect transistor with bipolar-like characteristics based on advanced 10 nm node fin field-effect transistors (PS-CT FinFET) with 9 nm thick Hf0.5Zr0.5O2 films. The special hybrid effects of charge-trapping and polarization-switching enabled eight Boolean logic functions with a single PS-CT FinFET and 16 Boolean logic functions with two complementary PS-CT FinFETs were obtained with three operations. Furthermore, reconfigurable full 1 bit adder and subtractor functions were demonstrated by connecting only two n-type and two p-type PS-CT FinFET devices, indicating that the technology was promising for LiM applications.

Yin-Yang: Programming Abstractions for Cross-Domain Multi-Acceleration.

FPGA accelerators offer performance and efficiency gains by narrowing the scope of acceleration to one algorithmic domain. However, real-life applications are often not limited to a single domain, which naturally makes Cross-Domain Multi-Acceleration a crucial next step. The challenge is, existing FPGA accelerators are built upon their specific vertically-specialized stacks, which prevents utilizing multiple accelerators from different domains. To that end, we propose a pair of dual abstractions, called Yin-Yang, which work in tandem and enable programmers to develop cross-domain applications using multiple accelerators on a FPGA. The Yin abstraction enables cross-domain algorithmic specification, while the Yang abstraction captures the accelerator capabilities. We also develop a dataflow virtual machine, dubbed XLVM, that transparently maps domain functions (Yin) to best-fit accelerator capabilities (Yang). With six real-world cross-domain applications, our evaluations show that Yin-Yang unlocks 29.4× speedup, while the best single-domain acceleration achieves 12.0×.

Nonvolatile Electrically Reconfigurable Integrated Photonic Switch Enabled by a Silicon PIN Diode Heater.

Reconfigurability of photonic integrated circuits (PICs) has become increasingly important due to the growing demands for electronic-photonic systems on a chip driven by emerging applications, including neuromorphic computing, quantum information, and microwave photonics. Success in these fields usually requires highly scalable photonic switching units as essential building blocks. Current photonic switches, however, mainly rely on materials with weak, volatile thermo-optic or electro-optic modulation effects, resulting in large footprints and high energy consumption. As a promising alternative, chalcogenide phase-change materials (PCMs) exhibit strong optical modulation in a static, self-holding fashion, but the scalability of present PCM-integrated photonic applications is still limited by the poor optical or electrical actuation approaches. Here, with phase transitions actuated by in situ silicon PIN diode heaters, scalable nonvolatile electrically reconfigurable photonic switches using PCM-clad silicon waveguides and microring resonators are demonstrated. As a result, intrinsically compact and energy-efficient switching units operated with low driving voltages, near-zero additional loss, and reversible switching with high endurance are obtained in a complementary metal-oxide-semiconductor (CMOS)-compatible process. This work can potentially enable very large-scale CMOS-integrated programmable electronic-photonic systems such as optical neural networks and general-purpose integrated photonic processors.

An Area-Efficient and Highly Linear Reconfigurable Continuous-Time Filter for Biomedical Sensor Applications.

This paper proposes a compact, high-linearity, and reconfigurable continuous-time filter with a wide frequency-tuning capability for biopotential conditioning. It uses an active filter topology and a new operational-transconductance-amplifier (OTA)-based current-steering (CS) integrator. Consequently, a large time constant τ , good linearity, and linear bandwidth tuning could be achieved in the presented filter with a small silicon area. The proposed filter has a reconfigurable structure that can be operated as a low-pass filter (LPF) or a notch filter (NF) for different purposes. Based on the novel topology, the filter can be readily implemented monolithically and a prototype circuit was fabricated in the 0.18 µm standard complementary-metal-oxide-semiconductor (CMOS) process. It occupied a small area of 0.068 mm2 and consumed 25 µW from a 1.8 V supply. Measurement results show that the cutoff frequency of the LPF could be linearly tuned from 0.05 Hz to 300 Hz and the total-harmonic-distortion (THD) was less than -76 dB for a 2 Hz, 200 mVpp sine input. The input-referred noises were 5.5 µVrms and 6.4 µVrms for the LPF and NF, respectively. A comparison with conventional designs reveals that the proposed design achieved the lowest harmonic distortion and smallest on-chip capacitor. Moreover, its ultra-low cutoff frequency and relatively linear frequency tuning capability make it an attractive solution as an analog front-end for biopotential acquisitions.

Reconfigurable Complementary Monolayer MoTe2 Field-Effect Transistors for Integrated Circuits.

Transition metal dichalcogenides are of interest for next generation switches, but the lack of low resistance electron and hole contacts in the same material has hindered the development of complementary field-effect transistors and circuits. We demonstrate an air-stable, reconfigurable, complementary monolayer MoTe2 field-effect transistor encapsulated in hexagonal boron nitride, using electrostatically doped contacts. The introduction of a multigate design with prepatterned bottom contacts allows us to independently achieve low contact resistance and threshold voltage tuning, while also decoupling the Schottky contacts and channel gating. We illustrate a complementary inverter and a p-i-n diode as potential applications.