Technology breakthroughs at the 2021 Symposia on VLSI Technology and Circuits.

An electronic network of compact oscillatory circuits can be used to find the optimal ground state of Ising Hamiltonians.

Combinatorial optimization problems belong to the non-deterministic polynomial time (NP)-hard complexity class, and their computational requirements scale exponentially with problem size. They can be mapped into the problem of finding the ground state of an Ising model, which describes a physical system with converging dynamics. Various platforms, including optical, electronic and quantum approaches

An organic phototransistor with two complementary bulk heterojunctions exhibits light-intensity-dependent adaptation behaviour that mimics the behaviour of the human visual system.

Wireless on-demand drug delivery systems exploit exogenous stimuli—acoustic waves, electric fields, magnetic fields and electromagnetic radiation—to trigger drug carriers. The approach allows drugs to be delivered with controlled release profiles and minimal off-target effects. Recent advances in electronics and materials engineering have led to the development of sophisticated systems designed for

The development of artificial visual systems that mimic biological systems requires devices that can autonomously adapt their response to varying stimuli. However, emulating biological feedforward visual adaptation is challenging and requires complementary photoexcitation and inhibition, ideally in a single device. Here we show that an organic transistor that incorporates two bulk heterojunctions is

Owing to its energy efficiency, silicon complementary metal–oxide–semiconductor (CMOS) technology is the current driving force of the integrated circuit industry. Silicon’s narrow bandgap has led to the advancement of wide-bandgap semiconductor materials, such as gallium nitride (GaN), being favoured in power electronics, radiofrequency power amplifiers and harsh environment applications. However,

The human body can be used as a medium to couple ambient energy and transmit power to wearable devices.

Lateral-channel dual-gate organic thin-film transistors have been used in pseudo complementary metal–oxide–semiconductor (CMOS) inverters to control switching voltage. However, their relatively long channel lengths, combined with the low charge carrier mobility of organic semiconductors, typically leads to slow inverter operation. Vertical-channel dual-gate organic thin-film transistors are a promising

Carbon materials such as graphene are of potential use in the development of electronic devices because of properties such as high mechanical strength and electrical and thermal conductivity. However, technical challenges, including difficulties in generating and modulating bandgaps, have limited the application of such materials. Here we show that the bandgaps of bilayers of two-dimensional C3N can

Two-dimensional structures that are engineered to manipulate electromagnetic radiation are becoming increasingly practical and could be of use in bioelectronics and communications.

Magnetic tunnel junctions with a hybrid free layer design can be used to electrically read and write domain walls.

The manipulation of fast domain wall motion in magnetic nanostructures could form the basis of novel magnetic memory and logic devices. However, current approaches for reading and writing domain walls require external magnetic fields, or are based on conventional magnetic tunnel junctions (MTJs) that are not compatible with high-speed domain wall motion. Here we report domain wall devices based on

Strong electron–electron interactions between adjacent nanoscale wires can lead to one-dimensional Coulomb drag, where current in one wire induces a voltage in the second wire via Coulomb interactions. This effect creates challenges for the development of nanoelectronic devices. Quantum spin Hall (QSH) insulators are a promising platform for the development of low-power electronic devices due to their

Electrically tunable metadevices can add novel functionalities to electronic and electromagnetic systems such as antennas and cloaking technologies. However, current microwave metadevices are based on materials that require sophisticated and expensive fabrication processes, and are not compatible with large-area and high-throughput deposition techniques on flexible platforms. Here we report reconfigurable

The development of next-generation wireless communication technology requires integrated radiofrequency devices capable of operating at frequencies greater than 90 GHz. Carbon nanotube field-effect transistors are promising for such applications, but key performance metrics, including operating frequency, at present fall below theoretical predictions. Here we report radiofrequency transistors based

Electric fields drive the degradation of wide-bandgap semiconductor devices. However, directly mapping the electric field inside an active device region remains challenging. Here we show that electric-field-induced second harmonic generation can be used to map the electric field in the device channel of GaN-based high-electron-mobility transistors at submicrometre resolution. To illustrate the capabilities

Boron arsenide could be used as a high-thermal-conductivity cooling substrate in gallium nitride power devices.

Curvy imagers that can adjust their shape are of use in imaging applications that require low optical aberration and tunable focusing power. Existing curvy imagers are either flexible but not compatible with tunable focal surfaces, or stretchable but with low resolution and pixel fill factors. Here, we show that curvy and shape-adaptive imagers with high pixel fill factors can be created by transferring

Two-dimensional (2D) semiconducting transition metal dichalcogenides could be used to build high-performance flexible electronics. However, flexible field-effect transistors (FETs) based on such materials are typically fabricated with channel lengths on the micrometre scale, not benefitting from the short-channel advantages of 2D materials. Here, we report flexible nanoscale FETs based on 2D semiconductors;

Thermal management is critical in modern electronic systems. Efforts to improve heat dissipation have led to the exploration of novel semiconductor materials with high thermal conductivity, including boron arsenide (BAs) and boron phosphide (BP). However, the integration of such materials into devices and the measurement of their interface energy transport remain unexplored. Here, we show that BAs

Bioelectronic systems typically rely on radiofrequency wireless components to interface with the human body, but such components are bulky and energy-demanding, which limits the performance of the systems. Metasurfaces—artificial two-dimensional materials with subwavelength structure—can be engineered to control electromagnetic fields around the human body and could be used to overcome the current

Wireless power transmission and energy harvesting techniques could be used to power and operate devices in, on and around the human body. However, near-field power transmission approaches are limited by distance, and the efficiency of far-field radiofrequency methods is limited by the body shadowing effect. Here, we show that the body-coupling characteristics of electromagnetic waves—which are either

Future devices for the Internet of Things will require communication systems that can deliver higher data rates at low power. Backscatter radio—in which wireless communication is achieved via reflection rather than radiation—is a low-complexity approach that requires a minimal number of active elements. However, it is typically limited to data rates of hundreds of megabits per second because of the

A single biological neuron can efficiently perform Boolean operations. Artificial neuromorphic systems, on the other hand, typically require several devices to complete a single operation. Here, we show that neuristors that exploit the intrinsic polarity of two-dimensional materials can perform logic operations in a single device. XNOR gates can be made using ambipolar tungsten diselenide (WSe2), NOR

Humans detect tactile stimuli through a combination of pressure and vibration signals using different types of cutaneous receptor. The development of artificial tactile perception systems is of interest in the development of robotics and prosthetics, and artificial receptors, nerves and skin have been created. However, constructing systems with human-like capabilities remains challenging. Here, we

The coronavirus pandemic and an increased demand for semiconductor technology has led to a global chip shortage — and a re-evaluation of global supply chains.

Unipolar barrier structures are used to suppress dark current in photodetectors by blocking majority carriers. Designing unipolar barriers with conventional materials is challenging due to the strict requirements of lattice and band matching. Two-dimensional materials have self-passivated surfaces and tunable band structures, and can thus be used to design unipolar barriers in which lattice mismatch

Magnetoelectric systems could be used to develop magnetoelectric random access memory and microsensor devices. One promising system is the two-phase 3-1-type multiferroic nanocomposite in which a one-dimensional magnetic column is embedded in a three-dimensional ferroelectric matrix. However, it suffers from a number of limitations including unwanted leakage currents and the need for biasing with a

The implementation of memristive synapses in neuromorphic computing is hindered by the limited reproducibility and high energy consumption of the switching behaviour of the devices. Typical filament-type memristors suffer, in particular, from temporal and spatial variation in the set voltage and resistance states due to stochastic filament formation. Here, we report memristors based on two-dimensional

Unique circumstances in Taiwan led to the creation of the foundry model, where an integrated circuit manufacturer has no products of its own and its plants produce only customer designs. The model has reshaped the global semiconductor industry and is well positioned to be at the heart of technological innovation in the industry.

Sub-1-nm vertical field-effect transistors can be created by transferring pre-made metal film contacts onto two-dimensional materials.

A superconducting electromechanical device at cryogenic temperatures can be probed using optical fibres and a commercial phase modulator.

A major challenge to the scalability of cryogenic computing platforms is the heat load associated with the growing number of electrical cable connections between the superconducting circuitry and the room-temperature environment. Compared with electrical cables, optical fibres have significantly lower thermal conductivity and are widely used in modern telecommunications. However, optical modulation

Graphene has a range of properties that makes it suitable for building devices for the Internet of Things. However, the deployment of such devices will also likely require the development of suitable graphene-based hardware security primitives. Here we report a physically unclonable function (PUF) that exploits disorders in the carrier transport of graphene field-effect transistors. The Dirac voltage

With careful planning and a focus on developing expertise, government policy has helped Taiwan become a centre for semiconductor innovation.

Transistors that are printed on paper substrates using all-carbon inks can be completely recycled, providing a potential route to helping solve the problem of electronic waste.

How did Taiwan — home to the world’s largest semiconductor foundry, TSMC — become a leading player in global electronics?

Vertical transistors—in which the channel length is determined by the thickness of the semiconductor—are of interest in the development of next-generation electronic devices. However, short-channel vertical devices are difficult to fabricate, because the high-energy metallization process typically results in damage to the contact region. Here we show that molybdenum disulfide (MoS2) vertical transistors

Electronic waste can lead to the accumulation of environmentally and biologically toxic materials and is a growing global concern. Developments in transient electronics—in which devices are designed to disintegrate after use—have focused on increasing the biocompatibility, whereas efforts to develop methods to recapture and reuse materials have focused on conducting materials, while neglecting other

Electronic technologies that can operate in harsh radiation environments are important in space, nuclear and avionic applications. However, radiation-hardened (rad-hard) integrated circuits often require additional processing and more complex configurations than conventional systems. Here we review the development of low-power, rad-hard electronics, examining the underlying phenomena of radiation-induced

A Correction to this paper has been published: https://doi.org/10.1038/s41928-021-00582-0.

Woven displays with a high number of light-emitting pixels can be created by interlacing two electrically conducting fibres and forming electroluminescent units at the crossover points.

Through a combination of talent cultivation and innovative research and development, the integrated circuit design industry in Taiwan now plays a central role in global electronics.

Wide-bandgap oxide semiconductors are essential for the development of high-speed and energy-efficient transparent electronics. However, while many high-mobility n-type oxide semiconductors are known, wide-bandgap p-type oxides have carrier mobilities that are one to two orders of magnitude lower due to strong carrier localization near their valence band edge. Here, we report the growth of bilayer

A Correction to this paper has been published: https://doi.org/10.1038/s41928-021-00572-2.

Implantable sensors can be used to monitor biomechanical strain continuously. However, three key challenges need to be addressed before they can be of use in clinical practice: the structural mismatch between the sensors and tissue or organs should be eliminated; a practical suturing attachment process should be developed; and the sensors should be equipped with wireless readout. Here, we report a

A Correction to this paper has been published: https://doi.org/10.1038/s41928-021-00571-3.

Monitoring the flow rate, cumulative loss and temperature of sweat can provide valuable physiological insights for the diagnosis of thermoregulatory disorders and illnesses related to heat stress. However, obtaining accurate, continuous estimates of these parameters with high temporal resolution remains challenging. Here, we report a platform that can wirelessly measure sweat rate, sweat loss and skin

Nanowire-based devices can potentially be of use in a variety of electronic applications, from ultrascaled digital circuits to 5G communication networks. However, the devices are typically restricted to low-power applications due to the relatively low electrical conductivity and limited voltage capability of the nanowires. Here, we show that wide-band-gap AlGaN/GaN nanowires containing multiple two-dimensional

Wearable sensors and machine learning can be a powerful combination for capturing human gestures and tactile interactions.

An AI-assisted smart textile can be used to record, model and understand human–environment interactions.

Three-dimensional (3D) complementary metal–oxide–semiconductor (CMOS) integration could enable device scaling beyond the limits of conventional 2D CMOS technology. Such integration requires vertical electrical connections that pass through silicon substrates and interconnect stacked chips. The fabrication of these through-silicon vias (TSVs) creates new challenges in metrology, including the characterization

Recording, modelling and understanding tactile interactions is important in the study of human behaviour and in the development of applications in healthcare and robotics. However, such studies remain challenging because existing wearable sensory interfaces are limited in terms of performance, flexibility, scalability and cost. Here, we report a textile-based tactile learning platform that can be used

Programmable metasurfaces can be used to encode wireless signals between users at different locations.

Digitally programmable metasurfaces are of potential use in wireless multiplexing techniques because they can encode and transmit information without using traditional radio-frequency components such as antennas or mixers. Space–time-coding digital metasurfaces can, in particular, manipulate the propagation direction and harmonic power distribution of electromagnetic waves, making them suitable for

Graphene is of interest in the development of next-generation electronics due to its high electron mobility, flexibility and stability. However, graphene transistors have poor on/off current ratios because of the absence of a bandgap. One approach to introduce an energy gap is to use a hydrogenation reaction, which changes graphene into insulating graphane with sp3 bonding. Here we show that an electric

Atomically thin materials can be used to build novel forms of conventional semiconductor heterostructure devices. One such device is a resonant tunnelling diode, which can exhibit negative differential resistance and usually consists of a quantum-well structure between two barrier layers. Here, we show that a twisted black phosphorus homostructure can be used to create a resonant tunnelling diode.

Ising machines are hardware devices that can solve ground-state search problems of Ising spin models and could be of use in solving various practical combinatorial optimization problems. However, large-scale systems have to be implemented by partitioning into subsystems that are hard to synchronize and where communication between them is difficult. Here, we report a scale-out architecture for Ising

Hydrogels offer tissue-like compliance, stretchability, fracture toughness, ionic conductivity and compatibility with biological tissues. However, their electrical conductivity (<100 S cm−1) is inadequate for digital circuits and applications in bioelectronics. Furthermore, efforts to increase conductivity by using hydrogel composites with conductive fillers have led to compromises in compliance and