The continuous miniaturization of field effect transistors (FETs) dictated by Moore's law has enabled continuous enhancement of their performance during the last four decades, allowing the ...fabrication of more powerful electronic products (e.g., computers and phones). However, as the size of FETs currently approaches interatomic distances, a general performance stagnation is expected, and new strategies to continue the performance enhancement trend are being thoroughly investigated. Among them, the use of 2D semiconducting materials as channels in FETs has raised a lot of interest in both academia and industry. However, after 15 years of intense research on 2D materials, there remain important limitations preventing their integration in solid‐state microelectronic devices. In this work, the main methods developed to fabricate FETs with 2D semiconducting channels are presented, and their scalability and compatibility with the requirements imposed by the semiconductor industry are discussed. The key factors that determine the performance of FETs with 2D semiconducting channels are carefully analyzed, and some recommendations to engineer them are proposed. This report presents a pathway for the integration of 2D semiconducting materials in FETs, and therefore, it may become a useful guide for materials scientists and engineers working in this field.
Developing field effect transistors with channels made of 2D semiconducting materials can produce substantial advances in several key technologies. However, their production at the wafer level for industrial application remains a big challenge. This work provides critical advice on materials synthesis, the effect of the electrode/channel contact resistance, dielectric environment, channel length, and channel thickness.
High-performance radio frequency (RF) switches play a critical role in allowing radio transceivers to provide access to shared resources such as antennas. They are important, especially in ...reconfigurable radios, where the connections within and between the different blocks (e.g., filters, amplifiers, and mixers) can be changed to customize and compose RF functions for distinct frequency bands. To realize this potential, new concepts for RF switch devices that can be integrated with standard transistor process, while providing better transmission performance, lower power consumption, smaller area, and lower actuation voltage than current RF switch technologies e.g., field-effect transistors (FETs) and microelectromechanical systems (MEMSs) are needed. Recently, RF switches based on emerging memory technologies, such as conductive-bridge RAM (CBRAM), resistive RAM (ReRAM), and phase-change memory (PCM), have been proposed. These nanoscale switches present major advantages, for example, high cutoff frequency, nonvolatility, fast and low-energy switching, small footprint, and compatibility with back-end-of-line (BEOL) of the standard CMOS process, thus placing them as possible contenders for high-performance RF switches. This article surveys high-performance RF switches based on resistive memories, comparing them with mature RF switching technologies like RF MEMS, p-i-n diodes, and FETs. We discuss the physical mechanisms, device structure, performance characteristics, and applications of these novel RF switches. Furthermore, we examine the prospects and future research directions of these technologies that could lead to their adoption at the industrial level.
Four-terminal, inline, indirectly heated phase-change switches (IPCS) have emerged as great contenders for reconfigurable radio frequency (RF) integrated circuits, providing state-of-the-art cutoff ...frequency thanks to their built-in dc-RF decoupling. However, the switching of IPCS devices is determined by their temperature which is challenging to predict. In this article, we present a physics-based compact model of the IPCS, validated by finite-element method simulations and measurements of IPCS devices. The model accurately predicts the thermal and electrical dynamics of the device by considering the changes in heater resistance, contact resistance, and parasitic capacitance. The complete model is implemented in Verilog-A, and a downloadable version is freely available at the nanoHUB.org. We show how the compact model can be used for rapid device evaluation and optimization between RF performance and energy efficiency. Nanosecond electrical thermometry of the heater for varying pulses during IPCS device operation and RF measurements is used to experimentally validate the model.
Two-dimensional (2D) molybdenum trioxide (MoO3) with mono- or few-layer thickness can potentially advance many applications, ranging from optoelectronics, catalysis, sensors, and batteries to ...electrochromic devices. Such ultrathin MoO3 sheets can also be integrated with other 2D materials (e.g., as dopants) to realize new or improved electronic devices. However, there is lack of a rapid and scalable method to controllably grow mono- or few-layer MoO3. Here, we report the first demonstration of using a rapid (<2 min) flame synthesis method to deposit mono- and few-layer MoO3 sheets (several microns in lateral dimension) on a wide variety of layered materials, including mica, MoS2, graphene, and WSe2, based on van der Waals epitaxy. The flame-grown ultrathin MoO3 sheet functions as an efficient hole doping layer for WSe2, enabling WSe2 to reach the lowest sheet and contact resistance reported to date among all the p-type 2D materials (∼6.5 kΩ/□ and ∼0.8 kΩ·μm, respectively). These results demonstrate that flame synthesis is a rapid and scalable pathway to growing atomically thin 2D metal oxides, opening up new opportunities for advancing 2D electronics.
Electrical contacts to atomically thin 2-D semiconductors are considered as the hindering aspect of electronic devices based on these materials. The high resistance of such contacts stems from their ...Schottky nature in contrast to the desired low-resistance Ohmic contacts. This issue of Schottky contacts is thus one of the major inhibitors to the integration of 2-D materials into mainstream technology. In this work, we explore contact resistance (<inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} </tex-math></inline-formula>) to atomically thin 2-D semiconductors in terms of the injected current through the Schottky barrier (SB) by using the Landauer-Büttiker formalism as well as experimental measurements and technology computer aided design (TCAD) simulations. We show that the SB height and width, which are determined by the metal-semiconductor interface and the number of charge carriers in the semiconductor channel, respectively, affect <inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} </tex-math></inline-formula> when it is relatively high (<inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} > </tex-math></inline-formula> 1 <inline-formula> <tex-math notation="LaTeX">\text{k}\Omega \cdot \mu \text{m} </tex-math></inline-formula>). However, the number of transport modes for carrier injection is the limiting factor for aggressive <inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} </tex-math></inline-formula> lowering (<inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} < </tex-math></inline-formula> 1 <inline-formula> <tex-math notation="LaTeX">\text{k}\Omega \cdot \mu \text{m} </tex-math></inline-formula>), even for near-zero SB height. Our results show that to reduce <inline-formula> <tex-math notation="LaTeX">{R}_{\text {C}} </tex-math></inline-formula> below <inline-formula> <tex-math notation="LaTeX">100~\Omega \cdot \mu \text{m} </tex-math></inline-formula>, large number of transport modes are required, which can be accomplished through raising the number of channel carriers above 5. 1013 cm-2 by means of heavy doping or gating. Our conclusions offer insight for future contact engineering and can explain recently published state-of-the-art results.
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