Integrated Circuits Research Articles

Two-Dimensional Semiconductors for State-of-the-Art Complementary Field-Effect Transistors and Integrated Circuits.

As the trajectory of transistor scaling defined by Moore's law encounters challenges, the paradigm of ever-evolving integrated circuit technology shifts to explore unconventional materials and architectures to sustain progress. Two-dimensional (2D) semiconductors, characterized by their atomic-scale thickness and exceptional electronic properties, have emerged as a beacon of promise in this quest for the continued advancement of field-effect transistor (FET) technology. The energy-efficient complementary circuit integration necessitates strategic engineering of both n-channel and p-channel 2D FETs to achieve symmetrical high performance. This intricate process mandates the realization of demanding device characteristics, including low contact resistance, precisely controlled doping schemes, high mobility, and seamless incorporation of high- κ dielectrics. Furthermore, the uniform growth of wafer-scale 2D film is imperative to mitigate defect density, minimize device-to-device variation, and establish pristine interfaces within the integrated circuits. This review examines the latest breakthroughs with a focus on the preparation of 2D channel materials and device engineering in advanced FET structures. It also extensively summarizes critical aspects such as the scalability and compatibility of 2D FET devices with existing manufacturing technologies, elucidating the synergistic relationships crucial for realizing efficient and high-performance 2D FETs. These findings extend to potential integrated circuit applications in diverse functionalities.

Iterative printing of bulk metal and polymer for additive manufacturing of multi-layer electronic circuits

In pursuing advancing additive manufacturing (AM) techniques for 3D objects, this study combines AM techniques for bulk metal and polymer on a single platform for one-stop printing of multilayer 3D electronic circuits with two novel aspects. The first innovation involves the embedded integration of electronic circuits by printing low-resistance electrical traces from bulk metal into polymer channels. Cross-section grinding results reveal (92 ± 5)% occupancy of electrically conductive traces in polymer channels despite the different thermal properties of the two materials. The second aspect encompasses the possibility of printing vertical bulk metal vias up to 10 mm in height with the potential for expansion, interconnecting electrically conductive traces embedded in different layers of the 3D object. The work provides comprehensive 3D printing design guidelines for successfully integrating fully embedded electrically conductive traces and the interconnecting vertical bulk metal vias. A smooth and continuous workflow is also introduced, enabling a single-run print of functional multilayer embedded 3D electronics. The design rules and the workflow facilitate the iterative printing of two distinct materials, each defined by unique printing temperatures and techniques. Observations indicate that conductive traces using molten metal microdroplets show a 12-fold reduction in resistance compared to nanoparticle ink-based methods, meaning this technique greatly complements multi-material additive manufacturing (MM-AM). The work presents insights into the behavior of molten metal microdroplets on a polymer substrate when printed through the MM-AM process. It explores their characteristics in two scenarios: When they are deposited side-by-side to form conductive traces and when they are deposited out-of-plane to create vertical bulk metal vias. The innovative application of MM-AM to produce multilayer embedded 3D electronics with bulk metal and polymer demonstrates significant potential for realizing the fabrication of free-form 3D electronics.

R&D of a timing measurement ASIC for possible HL-LHC upgrade

The Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN will undergo a major upgrade for the High Luminosity phase of the LHC (HL-LHC), which is expected to start in 2029 [1]. In addition to improving the detector rate capabilities and performance at increased higher luminosity, precision timing measurements are added to mitigate pile-up effects. The timing detector currently under construction covers pseudo-rapidity up to η=3[2] . A possible pathway for further improvements is the extension of timing capabilities to cover the full tracker acceptance up to η=4. Low Gain Avalanche Detectors (LGAD) pixels have been shown to be a suitable candidate for replacing a part of the pixel detector end-caps during a future Long Shutdown or Year-End Technical Stop of the LHC. Here, we present preliminary results of our design efforts towards a readout Application-specific integrated circuit (ASIC) capable of operating with LGAD pixel sensors [3]. The first results of the modeling of a part of the ASIC are demonstrated.

Hybrid integrated GaSb/Si3N4 narrow linewidth (<50 kHz) distributed Bragg reflector laser

A narrow linewidth hybrid integrated distributed Bragg reflector (DBR) laser platform operating at 2 μm wavelength region is demonstrated. The laser architecture comprises AlGaInAsSb/GaSb type-I quantum well reflective semiconductor optical amplifiers butt-coupled to a Si3N4 photonic integrated circuit (PIC), incorporating a narrow-band DBR. The DBR is realized with a long spiral-shaped waveguide structure with periodic circular posts placed adjacent to the waveguide. At room temperature operating conditions, the laser exhibits a maximum continuous wave output power of more than 17 mW for emission near 2 μm. Linewidth properties are analyzed with a heterodyne measurement technique, involving the mixing of the laser signal with a frequency comb phase-locked to an ultra-stable laser. The hybrid laser exhibits a narrow linewidth of ∼8 kHz in 1 ms timescale and ∼50 kHz in 10 ms timescale.

Grating Coupler Design for Low-Cost Fabrication in Amorphous Silicon Photonic Integrated Circuits

Photonic circuits find applications in biomedicine, manufacturing, quantum computing and communications. Photonic waveguides are crucial components, typically having cross-section orders of magnitude inferior when compared with other photonic components (e.g., optical fibers, light sources and photodetectors). Several light-coupling methods exist, consisting of either on-plane (e.g., adiabatic and end-fire coupling) or off-plane methods (e.g., grating and vertical couplers). The grating coupler is a versatile light-transference technique which can be tested at wafer level, not requiring specific fiber terminations or additional optical components, like lenses, polarizers or prisms. This study focuses on fully-etched grating couplers without a bottom reflector, made from hydrogenated amorphous silicon (a-Si:H), deposited over a silica substrate. Different coupler designs were tested, and of these we highlight two: the superimposition of two lithographic masks with different periods and an offset between them to create a random distribution and a technique based on the quadratic refractive-index variation along the device’s length. Results were obtained by 2D-FDTD simulation. The designed grating couplers achieve coupling efficiencies for the TE-like mode over −8 dB (mask overlap) and −3 dB (quadratic variation), at a wavelength of 1550 nm. The coupling scheme considers a 220 nm a-Si:H waveguide and an SMF-28 optical fiber.

Transmission Characteristics Analysis of a Twin-Waveguide Cavity

The transmission spectrum of a twin-waveguide cavity is systematically analyzed based on coupled mode theory, using the transfer matrix method (TMM). The results show that the traveling-wave transmission spectra of the twin-waveguide cavity is entirely determined by the coherent coupling effect involving the parameters of the effective refractive indices of the upper and lower waveguides, the coupling length Lc, and the ratio of the cavity length L to the coupling length (L/Lc). Filters with single, double, or triple-notch filtering could be obtained by choosing an appropriate L/Lc value. When the facet reflection is taken into consideration, the traveling-wave transmission spectrum is modified by the Fabry––Perot (FP) resonance, making it a standing-wave transmission spectrum. As a result, resonance splitting has been observed in the transmission spectrum of twin-waveguide resonators with high facet reflectivity. Further analysis shows that such an abnormal resonance phenomenon can be attributed to the destructive interference between the two FP resonance modes of the upper and lower waveguide through coherent coupling. In addition, narrow bandwidth amplification has also been observed through asymmetric facet reflections. Undoubtedly, all these unique spectral characteristics should be beneficial to the twin-waveguide cavity, achieving many more functions and being widely used in photonic integration circuits (PICs).

Iterative Placement of Decoupling Capacitors using Optimization Algorithms and Machine Learning

Abstract. In this work, an approach for optimum placement of on-board decoupling capacitors (decaps) is presented, which aims at reducing transient noise in power delivery networks (PDNs). This approach is based on a genetic algorithm (GA) and accelerated by the use of an artificial neural network (ANN) as surrogate model to efficiently determine the fitness of a decap design, i.e., of a particular choice for the position and the type of the decaps to integrate in the printed circuit board (PCB). The ANN is trained by a suitable set of reference designs labeled by the impedance at the power pin of the integrated circuit (IC), which is computed by commercial simulation software. Several iterative runs of the GA are performed with an increasing number of decaps to identify a design with the least number of decaps necessary to reduce the distance of the frequency domain input impedance of the considered point-to-point connection from a desired target impedance as far as possible. This approach is successfully applied to generate an optimum decap design for a PDN with 52 possible decap positions and decaps chosen from three types.

Preparation Of Carbon Nanotube Transistors and Their Applications in Integrated Circuits

Preparation Of Carbon Nanotube Transistors and Their Applications in Integrated Circuits

Polarization insensitive and wideband terahertz absorber using high-impedance resistive material of RuO2

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band.

Bound-state-in-continuum guided modes in a multilayer electro-optically active photonic integrated circuit platform: erratum

This erratum includes additional references omitted from the original paper [Optica 11, 706 (2024)OPTIC82334-253610.1364/OPTICA.516044].

Validation of Timepix4 energy calibration procedures with synchrotron X-ray beams

The Timepix4 is an application-specific integrated circuit developed by the Medipix4 collaboration. The chip is a 448 × 512 matrix that can be connected, via bump-bonding, to pixelated sensors of various materials and thicknesses, forming application specific detection systems. Among the Timepix4 operating modes, the data-driven Time-of-Arrival - Time-Over-Threshold is a particularly promising mode for spectral imaging applications: data packets are generated every time the charge created by the incoming radiation goes above a pre-defined threshold, allowing the count of the detected particles and their energy measurement. This article investigates the spectroscopic characteristics of a Timepix4 assembly equipped with a 300 μm Si sensor, using monochromatic X-ray beams in the energy range 8.5 keV–40 keV working at the SYRMEP beamline of the Elettra synchrotron. The accuracy and the energy resolution of the reconstructed energy spectra, together with an energy resolution model, will be presented.

Electric Field-Manipulated Optical Chirality in Ferroelectric Vortex Domains.

Manipulating optical chirality via electric fields has garnered considerable attention in the realm of both fundamental physics and practical applications. Chiral ferroelectrics, characterized by their inherent optical chirality and switchable spontaneous polarization, are emerging as a promising platform for electronic-photonic integrated circuits applications. Unlike organics with chiral carbon centers, integrating chirality into technologically mature inorganic ferroelectrics has posed a long-standing challenge. Here, the successful introduction of chirality is reported into self-assembly La-doped BiFeO3 nanoislands, which exhibit ferroelectric vortex domains. By employing synergistic experimental techniques with piezoresponse force microscopy and nonlinear optical second-harmonic generation probes, a clear correlation between chirality and polarization configuration within these ferroelectric nanoislands is established. Furthermore, the deterministic control of ferroelectric vortex domains and chirality is demonstrated by applying electric fields, enabling reversible and nonvolatile generation and elimination of optically chiral signals. These findings significantly expand the repertoire of field-controllable chiral systems and lay the groundwork for the development of innovative ferroelectric optoelectronic devices.

Investigating superior performance by configuring bimetallic electrodes on fabric triboelectric nanogenerators (F-TENGs) for IoT enabled touch sensor applications

Fabric Triboelectric Nanogenerators (F-TENGs) are increasingly becoming more significant in wearable monitoring and beyond. These devices offer autonomous energy generation and sensing capabilities, by replacing conventional batteries in flexible wearables. Despite the substantial effort, however, achieving high output with optimal stability, durability, comfort, and washability poses substantial challenges, so we have yet to see any practical commercial uses of these materials. This study focuses on output and investigates the impacts of mono and bimetallic composite fabric electrode configurations on the output performance of F-TENGs. Our findings showcase the superiority of bimetallic configurations, particularly those incorporating Copper (Cu) with Nickel (Ni), over monometallic (Cu only) electrodes. These configurations demonstrate remarkable results, exhibiting a maximum instantaneous voltage, current, and power density of ∼ 199 V (a twofold increase compared to monometallic configurations), ∼22 μA (a threefold increase compared to monometallic configurations), and 2992 mW/m², respectively. Notably, these bimetallic configurations also exhibit exceptional flexibility, shape adaptability, structural integrity, washability, and mechanical stability. Furthermore, the integration of passive component-based power management circuits significantly enhances the performance capabilities of the F-TENGs, highlighting the essential role of power management circuits and electrode selection in optimizing F-TENGs. In addition, we have developed a complete IoT-enabled touch sensor system using CuNi-BEF EcoFlex layered F-TENGs for precise detection of soft and hard touches. This advanced system enhances robotic functionality, enabling nuanced touch understanding essential for precision tasks and fostering more intuitive human-machine interactions.

The Molecular Substrates of Insect Eusociality.

The evolution of eusociality in Hymenoptera-encompassing bees, ants, and wasps-is characterized by multiple gains and losses of social living, making this group a prime model to understand the mechanisms that underlie social behavior and social complexity. Our review synthesizes insights into the evolutionary history and molecular basis of eusociality. We examine new evidence for key evolutionary hypotheses and molecular pathways that regulate social behaviors, highlighting convergent evolution on a shared molecular toolkit that includes the insulin/insulin-like growth factor signaling (IIS) and target of rapamycin (TOR) pathways, juvenile hormone and ecdysteroid signaling, and epigenetic regulation. We emphasize how the crosstalk among these nutrient-sensing and endocrine signaling pathways enables social insects to integrate external environmental stimuli, including social cues, with internal physiology and behavior. We argue that examining these pathways as an integrated regulatory circuit and exploring how the regulatory architecture of this circuit evolves alongside eusociality can open the door to understanding the origin of the complex life histories and behaviors of this group.

InGaAs/GaAs nano-ridge laser with an amorphous silicon grating monolithically grown on a 300 mm Si wafer.

The monolithic growth of direct-bandgap III-V materials directly on a Si substrate is a promising approach for the fabrication of complex silicon photonic integrated circuits including light sources and amplifiers. It remains challenging to realize practical, reliable, and efficient light emitters due to misfit defect formation during the epitaxial growth. Exploiting nano-ridge engineering (NRE), III-V nano-ridges with high crystal quality were achieved based on aspect ratio defect trapping inside narrow trenches. In an earlier work, we used an etched grating to create distributed feedback lasers from these nano-ridges. Here we deposited an amorphous silicon grating on the top of the nano-ridge. Under pulsed optical pumping, a ∼7.84 kW/cm2 lasing threshold was observed, ∼5 times smaller compared to devices with an etched grating inside the nano-ridge. Compared to the etched grating, the amorphous silicon grating introduces no extra carrier loss channels through surface state defects, which is believed to be the origin of the lower threshold. This low threshold again demonstrates the high quality of the epitaxial deposited material and may provide a route toward further optimizing the electrically driven devices.

Reconfigurable Vertical Phototransistor with MoTe2 Homojunction for High-Speed Rectifier and Multivalued Logical Circuits.

The most reported two-dimensional (2D) reconfigurable multivalued logic (RMVL) devices primarily involve a planar configuration and carrier transport, which limits the high-density circuit integration and high-speed logic operation. In this work, the vertical transistors with reconfigurable MoTe2 homojunction are developed for low-power, high-speed, multivalued logic circuits. Through top/bottom dual-gate modulation, the transistors can be configured into four modes: P-i-N, N-i-P, P-i-P, and N-i-N. The reconfigurable rectifying and photovoltaic behaviors are observed in P-i-N and N-i-P configurations, exhibiting ideal diode characteristics with a current rectification ratio over 105 and sign-reversible photovoltaic response with a photoswitching ratio up to 7.44 × 105. Taking advantage of the seamless homogeneous integration and short vertical channel architecture, the transistor can operate as an electrical switch with an ultrafast speed of 680 ns, surpassing the conventional p-n diode. The MoTe2 half-wave rectifier is then applied in high-frequency integrated circuits using both square wave and sinusoidal waveforms. By applying an electrical pulse with a 1/4 phase difference between two input signals, the RMVL circuit has been achieved. This work proposes a universal and reconfigurable vertical transistor, enabled by dual-gate electrostatic doping on top/bottom sides of MoTe2 homojunction, suggesting a high integration device scheme for high-speed RMVL circuits and systems.

On-chip topological beamformer for multi-link terahertz 6G to XG wireless.

Terahertz (THz) wireless communication holds immense potential to revolutionize future 6G to XG networks with high capacity, low latency and extensive connectivity. Efficient THz beamformers are essential for energy-efficient connections, compensating path loss, optimizing resource usage and enhancing spectral efficiency. However, current beamformers face several challenges, including notable loss, limited bandwidth, constrained spatial coverage and poor integration with on-chip THz circuits. Here we present an on-chip broadband THz topological beamformer using valley vortices for waveguiding, splitting and perfect isolation in waveguide phased arrays, featuring 184 densely packed valley-locked waveguides, 54 power splitters and 136 sharp bends. Leveraging neural-network-assisted inverse design, the beamformer achieves complete 360° azimuthal beamforming with gains of up to 20 dBi, radiating THz signals into free space with customizable user-defined beams. Photoexciting the all-silicon beamformer enables reconfigurable control of THz beams. The low-loss and broadband beamformer enables a 72-Gbps chip-to-chip wireless link over 300 mm and eight simultaneous 40-Gbps wireless links. Using four of these links, we demonstrate point-to-4-point real-time HD video streaming. Our work provides a complementary metal-oxide-semiconductor-compatible THz topological photonic integrated circuit for efficient large-scale beamforming, enabling massive single-input multiple-output and multiple-input and multiple-output systems for terabit-per-second 6G to XG wireless communications.

Motor Cortical Neuronal Hyperexcitability Associated with α-Synuclein Aggregation.

Dysfunction of the cerebral cortex is thought to underlie motor and cognitive impairments in Parkinson disease (PD). While cortical function is known to be suppressed by abnormal basal ganglia output following dopaminergic degeneration, it remains to be determined how the deposition of Lewy pathology disrupts cortical circuit integrity and function. Moreover, it is also unknown whether cortical Lewy pathology and midbrain dopaminergic degeneration interact to disrupt cortical function in late-stage. To begin to address these questions, we injected α-synuclein (αSyn) preformed fibrils (PFFs) into the dorsolateral striatum of mice to seed αSyn pathology in the cortical cortex and induce degeneration of midbrain dopaminergic neurons. Using this model system, we reported that αSyn aggregates accumulate in the motor cortex in a layer- and cell-subtype-specific pattern. Particularly, intratelencephalic neurons (ITNs) showed earlier accumulation and greater extent of αSyn aggregates relative to corticospinal neurons (CSNs). Moreover, we demonstrated that the intrinsic excitability and inputs resistance of αSyn aggregates-bearing ITNs in the secondary motor cortex (M2) are increased, along with a noticeable shrinkage of cell bodies and loss of dendritic spines. Last, neither the intrinsic excitability of CSNs nor their thalamocortical input was altered by a partial striatal dopamine depletion associated with αSyn pathology. Our results documented motor cortical neuronal hyperexcitability associated with αSyn aggregation and provided a novel mechanistic understanding of cortical circuit dysfunction in PD.

Research on optical interferometric imaging with flexible control using optical fibers and PIC chip

We propose a prototype called a flexible integrated resolution and efficient light-imaging-expanded synthetic system (FIREFLIES). This paper describes the design, manufacturing, and experimental demonstration of the proposed system. FIREFLIES enables interferometric imaging at approximately 1550 nm using a variable baseline sampling technique, in which the baseline-collected light field forms interference fringes that are captured by an on-chip photodetector. This innovation extends the limited sampling distance imposed by the processing size restrictions of traditional photonic integrated circuit (PIC) links. Furthermore, we introduce a unique method for achieving super-resolution sampling by flexibly controlling the baseline. An experimental platform is constructed to test the FIREFLIES against a one-dimensional grating target. The experimental curves closely align with the theoretical predictions, confirming the efficacy of the system in super-resolution sampling and imaging performance.

Optimization design and application scenario research of low power digital integrated circuit

Optimization design and application scenario research of low power digital integrated circuit