Transistor-based Circuits Research Articles

Recent Progress in Development of Artificial Neuromorphic Devices Based on Emerging Materials

In the fourth industrial revolution, the efficient processing of huge amounts of data is important due to the development of artificial intelligence (AI), internet of things (IoT), and machine learning (ML). The conventional computing system, which is known as von Neumann architecture, has been facing bottleneck problems because of the physical separation of memory and central processing unit (CPU). Many researchers have interested to study on neuromorphic computing, inspired by the human brain, to solve the bottleneck problems. The development of artificial neuromorphic devices, such as neuron and synaptic devices, is important to successfully demonstrate a neuromorphic computing hardware. Various Si CMOS transistor-based circuits have been investigated to implement the behaviors of the biological neuron and synapse; however, they are not suitable for mimicking the large-scale biological neural networks because of Si CMOS transistor’s scalability and power consumption issues. In this report, we review the recent research progress in artificial neurons and synaptic devices based on emerging materials and discuss the future research direction of artificial neural networks.

Uniting GaN Electronics and Photonics on A Single Chip

The bandgap energies of the group III-V semiconductor gallium nitride (GaN) and its alloys cover emission wavelengths ranging from the ultraviolet to the visible. Concurrently, GaN has enabled high performance transistors to provide attractive solutions in the high voltage and high frequency regimes. Both GaN optoelectronics and electronics have been successfully developed, and the two technologies are often dependent on each other in many real-life applications. In the simplest case, both the GaN light-emitting diode (LED) and photodiode have to be driven or amplified by transistor-based circuits. However, these circuits are separately made on the Si platform. What if GaN optoelectronics and electronics can be integrated onto the same platform? That would result in significant reduction in material costs, processing costs and packaging costs. At the same time, the performance of the monolithically integrated system will be significantly improved, due to reduced resistances and parasitic capacitances. In view of such prospects, we propose and characterize monolithically integrated GaN metal-oxide-semiconductor field effect transistors (MOSFETs), transmitter, waveguide, and receiver, which are fabricated onto a conventional InGaN/GaN LED wafer without involving re-growth or post-growth doping (diffusion or ion implantation). The capability of integrating optoelectronics (transmitter, waveguide, receiver) with MOSFETs would inevitably open up new horizons for the GaN platform.

Nonvolatile Multilevel Photomemory Based on Lead-Free Double Perovskite Cs2AgBiBr6 Nanocrystals Wrapped Within SiO2 as a Charge Trapping Layer.

Floating gate transistor photomemory (FGTPM) has been regarded as one of the most prospective nonvolatile photomemory devices because of its compatibility with transistor-based circuits, nondestructive reading, and multilevel storage. Until now, owing to the excellent photoelectric properties, lead-based perovskite nanocrystals (PNCs) have been applied in most of the perovskite-based FGTPM devices and embedded in the polymer matrix as the charge trapping layer. However, the polymer matrix and its solvent would degrade the structure of the PNCs, resulting in the loss of their unique photoresponse ability. In addition, lead-based perovskites have environmental unfriendliness and poor stability. Hence, a novel nonvolatile FGTPM based on oligomeric silica (OS) wrapped lead-free double perovskite Cs2AgBiBr6 NCs was demonstrated for the first time. Acting synchronously as the protection layer for the discrete Cs2AgBiBr6 NCs and charge tunneling layer for the FGTPM device, the OS layer can achieve controllable thickness by adjusting the process parameters, leading to an adjustment of storage properties with a larger memory window (58 V). Owing to the excellent photoresponse ability of the Cs2AgBiBr6@OS composite layer, the FGTPM device exhibited high-performance with repeatable multilevel nonvolatile photomemory and precise photoresponse ability of wavelength/time/power-dependent photoirradiation without extra gate biasing.

Monolithic Integration and Design of Solution-Processed Metal-Oxide Circuitry in Organic Photosensor Arrays

Metal-oxide and organic semiconductors possess distinctive characteristics, such as relative high performance for oxide semiconductors and abundance of functional materials for organic semiconductors. Here, we demonstrate monolithically integrated $13\times 13$ solution-processed oxide-organic hybrid photosensor arrays, in which the optical response from the organic material is transferred to oxide thin-film transistor-based circuits for $10^{1} \sim 10^{3}$ orders of signal amplification. Especially, we modulated signal amplification of the sensor by adjusting the circuit design resulting in high photosensitivity.

Fringe Field Effect on Electrical Characteristics of Pentacene Thin-Film Transistors

This paper reports the effects of the fringe field on the operating characteristics of geometrically-modified pentacene thin-film transistors (TFTs) with a polymeric gate insulator. When the dimensions of the pentacene film structurally exceeded the channel region, the output current at a given voltage was overestimated by the extra charge carriers, which were affected by the fringe field in the peripheral territory away from the channel region. By examining the range of operating frequencies, the fringe field was found to have a much more serious effect at low frequencies due to the slow movement of charge carriers stored around the periphery of the patterned source and drain electrodes. This suggests that minimizing the fringe field is important for improving the dynamic characteristics of the organic transistor-based circuits operating at low frequencies.

Exploring the Design of the Magnetic–Electrical Interface for Nanomagnet Logic

Nanomagnet logic (NML) has received increasing attention as an alternative information processing technology given the potential for low energy dissipation, a relatively advanced experimental state of the art, and intangibles such as inherent radiation hardness and nonvolatility. In order to facilitate the integration of NML-based circuits with transistor-based circuits, a magnetic-electrical interface (MEI) is needed. This paper focuses on the output portion of MEI design, i.e., converting signals from the magnetic domain to the electrical domain. The basic idea of an MEI output is to employ fringing fields from an NML device to set the magnetization state of the free layer of a magnetic tunnel junction. A detailed study of four different MEI output designs is presented which considers metrics such as the clock energy required to set the output state, the magnetoresistance ratio, etc. Simulation-based analysis reveals the pros and cons of each design. A design where multiple NML devices (i.e., free layers) share a large synthetic antiferromagnet is most promising based on our simulation-based, quantitative analysis.

Optimization of Inkjet-Based Process Modules for Printed Transistor Circuits

We report on the development of inkjet-based process modules for printed transistor-based circuits. The requirement for realization of printed transistor-based circuits is the capability to print consistent fine lines for transistor electrodes and uniform/conformal layers of insulators and semiconductor islands on top of the printed electrodes by optimizing the printing parameters and surface energy of the underlying layers. The baseline processes accomplished the above-mention requirement were developed. In addition, we demonstrate novel process modules such as self-alignment of transistor electrodes, printed self-aligned interconnect and printed local interconnect by simultaneous dissolving and connecting the underlying metal layers. Lastly, a printed inverter circuit utilizing the complete printing modules was demonstrated to illustrate the simplicity and the feasibility of the inkjet-based process modules towards the realization of low-cost printed electronics.