End-Bonded Metal Contacts on WSe2 Field-Effect Transistors

Contacts at the Nanoscale and for Nanomaterials

Contact scaling is a major challenge in nano complementary metal-oxide-semiconductor (CMOS) technology, as the surface roughness, contact size, film thicknesses, and undoped substrate become more problematic as the technology shrinks to the nanometer range. These factors increase the contact resistance and the nonlinearity of the current-voltage characteristics, which could limit the benefits of the further downsizing of CMOS devices. This review discusses issues related to the contact size reduction of nano CMOS technology and the validity of the Schottky junction model at the nanoscale. The difficulties, such as the limited doping level and choices of metal for band alignment, Fermi-level pinning, and van der Waals gap, in achieving transparent ohmic contacts with emerging two-dimensional materials are also examined. Finally, various methods for improving ohmic contacts' characteristics, such as two-dimensional/metal van der Waals contacts and hybrid contacts, junction doping technology, phase and bandgap modification effects, buffer layers, are highlighted.

Tuning Polarity in WSe2/AlScN FeFETs via Contact Engineering

Recent advancements in ferroelectric field-effect transistors (FeFETs) using two-dimensional (2D) semiconductor channels and ferroelectric Al0.68Sc0.32N (AlScN) allow high-performance nonvolatile devices with exceptional ON-state currents, large ON/OFF current ratios, and large memory windows (MW). However, previous studies have solely focused on n-type FeFETs, leaving a crucial gap in the development of p-type and ambipolar FeFETs, which are essential for expanding their applicability to a wide range of circuit-level applications. Here, we present a comprehensive demonstration of n-type, p-type, and ambipolar FeFETs on an array scale using AlScN and multilayer/monolayer WSe2. The dominant injected carrier type is modulated through contact engineering at the metal-semiconductor junction, resulting in the realization of all three types of FeFETs. The effect of contact engineering on the carrier injection is further investigated through technology-computer-aided design simulations. Moreover, our 2D WSe2/AlScN FeFETs achieve high electron and hole current densities of ∼20 and ∼10 μA/μm, respectively, with a high ON/OFF ratio surpassing ∼107 and a large MW of >6 V (0.14 V/nm).

Ultrafast and Broad-Band Graphene Heterojunction Photodetectors with High Gain

Graphene possesses an exotic band structure that spans a wide range of important technological wavelength regimes for photodetection, all within a single material. Conventional methods aimed at enhancing detection efficiency often suffer from an extended response time when the light is switched off. The task of achieving ultrafast broad-band photodetection with a high gain remains challenging. Here, we propose a devised architecture that combines graphene with a photosensitizer composed of an alternating strip superstructure of WS2-WSe2. Upon illumination, n+-WS2 and p+-WSe2 strips create alternating electron- and hole-conduction channels in graphene, effectively overcoming the tradeoff between the responsivity and switch time. This configuration allows for achieving a responsivity of 1.7 × 107 mA/W, with an extrinsic response time of 3-4 μs. The inclusion of the superstructure booster enables photodetection across a wide range from the near-ultraviolet to mid-infrared regime and offers a distinctive photogating route for high responsivity and fast temporal response in the pursuit of broad-band detection.

Controlled synthesis of van der Waals CoS2for improved p-type transistor contact

Two-dimensional (2D) van der Waals (vdW) p-type semiconductors have shown attractive application prospects as atomically thin channels in electronic devices. However, the high Schottky hole barrier of p-type semiconductor-metal contacts induced by Fermi-level pinning is hardly removed. Herein, we prepare a vdW 1T-CoS2nanosheet as the contact electrode of a WSe2field-effect transistor (FET), which shows a considerably high on/off ratio > 107and a hole mobility of ∼114.5 cm2V-1s-1. The CoS2nanosheets exhibit metallic conductivity with thickness dependence, which surpasses most 2D transition metal dichalcogenide metals or semimetals. The excellent FET performance of the CoS2-contacted WSe2FET device can be attributed to the high work function of CoS2, which lowers the Schottky hole barrier. Our work provides an effective method for growing vdW CoS2and opens up more possibilities for the application of 2D p-type semiconductors in electronic devices.

Two-Step Flux Synthesis of Ultrapure Transition-Metal Dichalcogenides

Two-dimensional transition-metal dichalcogenides (TMDs) have attracted tremendous interest due to the unusual electronic and optoelectronic properties of isolated monolayers and the ability to assemble diverse monolayers into complex heterostructures. To understand the intrinsic properties of TMDs and fully realize their potential in applications and fundamental studies, high-purity materials are required. Here, we describe the synthesis of TMD crystals using a two-step flux growth method that eliminates a major potential source of contamination. Detailed characterization of TMDs grown by this two-step method reveals charged and isovalent defects with densities an order of magnitude lower than those in TMDs grown by a single-step flux technique. For WSe2, we show that increasing the Se/W ratio during growth reduces point defect density, with crystals grown at 100:1 ratio achieving charged and isovalent defect densities below 1010 and 1011 cm-2, respectively. Initial temperature-dependent electrical transport measurements of monolayer WSe2 yield room-temperature hole mobility above 840 cm2/(V s) and low-temperature disorder-limited mobility above 44,000 cm2/(V s). Electrical transport measurements of graphene-WSe2 heterostructures fabricated from the two-step flux grown WSe2 also show superior performance: higher graphene mobility, lower charged impurity density, and well-resolved integer quantum Hall states. Finally, we demonstrate that the two-step flux technique can be used to synthesize other TMDs with similar defect densities, including semiconducting 2H-MoSe2 and 2H-MoTe2 and semimetallic Td-WTe2 and 1T'-MoTe2.

Fabrication of p-type 2D single-crystalline transistor arrays with Fermi-level-tuned van der Waals semimetal electrodes

High-performance p-type two-dimensional (2D) transistors are fundamental for 2D nanoelectronics. However, the lack of a reliable method for creating high-quality, large-scale p-type 2D semiconductors and a suitable metallization process represents important challenges that need to be addressed for future developments of the field. Here, we report the fabrication of scalable p-type 2D single-crystalline 2H-MoTe2 transistor arrays with Fermi-level-tuned 1T'-phase semimetal contact electrodes. By transforming polycrystalline 1T'-MoTe2 to 2H polymorph via abnormal grain growth, we fabricated 4-inch 2H-MoTe2 wafers with ultra-large single-crystalline domains and spatially-controlled single-crystalline arrays at a low temperature (~500 °C). Furthermore, we demonstrate on-chip transistors by lithographic patterning and layer-by-layer integration of 1T' semimetals and 2H semiconductors. Work function modulation of 1T'-MoTe2 electrodes was achieved by depositing 3D metal (Au) pads, resulting in minimal contact resistance (~0.7 kΩ·μm) and near-zero Schottky barrier height (~14 meV) of the junction interface, and leading to high on-state current (~7.8 μA/μm) and on/off current ratio (~105) in the 2H-MoTe2 transistors.

Combination of Polymer Gate Dielectric and Two-Dimensional Semiconductor for Emerging Field-Effect Transistors

Two-dimensional (2D) materials are considered attractive semiconducting layers for emerging field-effect transistors owing to their unique electronic and optoelectronic properties. Polymers have been utilized in combination with 2D semiconductors as gate dielectric layers in field-effect transistors (FETs). Despite their distinctive advantages, the applicability of polymer gate dielectric materials for 2D semiconductor FETs has rarely been discussed in a comprehensive manner. Therefore, this paper reviews recent progress relating to 2D semiconductor FETs based on a wide range of polymeric gate dielectric materials, including (1) solution-based polymer dielectrics, (2) vacuum-deposited polymer dielectrics, (3) ferroelectric polymers, and (4) ion gels. Exploiting appropriate materials and corresponding processes, polymer gate dielectrics have enhanced the performance of 2D semiconductor FETs and enabled the development of versatile device structures in energy-efficient ways. Furthermore, FET-based functional electronic devices, such as flash memory devices, photodetectors, ferroelectric memory devices, and flexible electronics, are highlighted in this review. This paper also outlines challenges and opportunities in order to help develop high-performance FETs based on 2D semiconductors and polymer gate dielectrics and realize their practical applications.

One-dimensional semimetal contacts to two-dimensional semiconductors

Two-dimensional (2D) semiconductors are promising in channel length scaling of field-effect transistors (FETs) due to their excellent gate electrostatics. However, scaling of their contact length still remains a significant challenge because of the sharply raised contact resistance and the deteriorated metal conductivity at nanoscale. Here, we construct a 1D semimetal-2D semiconductor contact by employing single-walled carbon nanotube electrodes, which can push the contact length into the sub-2 nm region. Such 1D-2D heterostructures exhibit smaller van der Waals gaps than the 2D-2D ones, while the Schottky barrier height can be effectively tuned via gate potential to achieve Ohmic contact. We propose a longitudinal transmission line model for analyzing the potential and current distribution of devices in short contact limit, and use it to extract the 1D-2D contact resistivity which is as low as 10^-6 Ω·cm² for the ultra-short contacts. We further demonstrate that the semimetal nanotubes with gate-tunable work function could form good contacts to various 2D semiconductors including MoS₂, WS₂ and WSe₂. The study on 1D semimetal contact provides a basis for further miniaturization of nanoelectronics in the future.

P-Type 2D Semiconductors for Future Electronics

2D semiconductors represent one of the best candidates to extend Moore's law for their superiorities, such as keeping high carrier mobility and remarkable gate-control capability at atomic thickness. Complementary transistors and van der Waals junctions are critical in realizing 2D semiconductors-based integrated circuits suitable for future electronics. N-type 2D semiconductors have been reported predominantly for the strong electron doping caused by interfacial charge impurities and internal structural defects. By contrast, superior and reliable p-type 2D semiconductors with holes as majority carriers are still scarce. Not only that, but some critical issues have not been adequately addressed, including their controlled synthesis in wafer size and high quality, defect and carrier modulation, optimization of interface and contact, and application in high-speed and low-power integrated devices. Here the material toolkit, synthesis strategies, device basics, and digital electronics closely related to p-type 2D semiconductors are reviewed. Their opportunities, challenges, and prospects for future electronic applications are also discussed, which would be promising or even shining in the post-Moore era.

Recent Progress in 1D Contacts for 2D-Material-Based Devices

Recent studies have intensively examined 2D materials (2DMs) as promising materials for use in future quantum devices due to their atomic thinness. However, a major limitation occurs when 2DMs are in contact with metals: a van der Waals (vdW) gap is generated at the 2DM-metal interfaces, which induces metal-induced gap states that are responsible for an uncontrollable Schottky barrier (SB), Fermi-level pinning (FLP), and high contact resistance (R_C ), thereby substantially lowering the electronic mobility of 2DM-based devices. Here, vdW-gap-free 1D edge contact is reviewed for use in 2D devices with substantially suppressed carrier scattering of 2DMs with hexagonal boron nitride (hBN) encapsulation. The 1D contact further enables uniform carrier transport across multilayered 2DM channels, high-density transistor integration independent of scaling, and the fabrication of double-gate transistors suitable for demonstrating unique quantum phenomena of 2DMs. The existing 1D contact methods are reviewed first. As a promising technology toward the large-scale production of 2D devices, seamless lateral contacts are reviewed in detail. The electronic, optoelectronic, and quantum devices developed via 1D contacts are subsequently discussed. Finally, the challenges regarding the reliability of 1D contacts are addressed, followed by an outlook of 1D contact methods.

All-van-der-Waals Barrier-Free Contacts for High-Mobility Transistors

Ultrathin 2D semiconductor devices are considered to have beyond-silicon potential but are severely troubled by the high Schottky barriers of the metal-semiconductor contacts, especially for p-type semiconductors. Due to the severe Fermi-level pinning effect and the lack of conventional semimetals with high work functions, their Schottky hole barriers are hardly removed. Here, an all-van-der-Waals barrier-free hole contact between p-type tellurene semiconductor and layered 1T'-WS₂ semimetal is reported, which achieves a zero Schottky barrier height of 3 ± 9 meV and a high field-effect mobility of ≈1304 cm² V^-1 s^-1 . The formation of such contacts can be attributed to the higher work function of ≈4.95 eV of the 1T'-WS₂ semimetal, which is in sharp contrast with low work function (4.1-4.7 eV) of conventional semimetals. The study defines an available strategy for eliminating the Schottky barrier of metal-semiconductor contacts, facilitating 2D-semiconductor-based electronics and optoelectronics to extend Moore's law.

Molecule-Upgraded van der Waals Contacts for Schottky-Barrier-Free Electronics

The applications of any ultrathin semiconductor device are inseparable from high-quality metal-semiconductor contacts with designed Schottky barriers. Building van der Waals (vdWs) contacts of 2D semiconductors represents an advanced strategy of lowering the Schottky barrier height by reducing interface states, but will finally fail at the theoretical minimum barrier due to the inevitable energy difference between the semiconductor electron affinity and the metal work function. Here, an effective molecule optimization strategy is reported to upgrade the general vdWs contacts, achieving near-zero Schottky barriers and creating high-performance electronic devices. The molecule treatment can induce the defect healing effect in p-type semiconductors and further enhance the hole density, leading to an effectively thinned Schottky barrier width and improved carrier interface transmission efficiency. With an ultrathin Schottky barrier width of ≈2.17 nm and outstanding contact resistance of ≈9 kΩ µm in the optimized Au/WSe₂ contacts, an ultrahigh field-effect mobility of ≈148 cm²  V^-1 s^-1 in chemical vapor deposition grown WSe₂ flakes is achieved. Unlike conventional chemical treatments, this molecule upgradation strategy leaves no residue and displays a high-temperature stability at >200 °C. Furthermore, the Schottky barrier optimization is generalized to other metal-semiconductor contacts, including 1T-PtSe₂ /WSe₂ , 1T'-MoTe₂ /WSe₂ , 2H-NbS₂ /WSe₂ , and Au/PdSe₂ , defining a simple, universal, and scalable method to minimize contact resistance.

Mobility Extraction in 2D Transition Metal Dichalcogenide Devices-Avoiding Contact Resistance Implicated Overestimation

Schottky barrier (SB) transistors operate distinctly different from conventional metal-oxide semiconductor field-effect transistors, in a unique way that the gate impacts the carrier injection from the metal source/drain contacts into the channel region. While it has been long recognized that this can have severe implications for device characteristics in the subthreshold region, impacts of contact gating of SB in the on-state of the devices, which affects evaluation of intrinsic channel properties, have been yet comprehensively studied. Due to the fact that contact resistance (R_C ) is always gate-dependent in a typical back-gated device structure, the traditional approach of deriving field-effect mobility from the maximum transconductance (g_m ) is in principle not correct and can even overestimate the mobility. In addition, an exhibition of two different threshold voltages for the channel and the contact region leads to another layer of complexity in determining the true carrier concentration calculated from Q = C_OX * (V_G -V_TH ). Through a detailed experimental analysis, the effect of different effective oxide thicknesses, distinct SB heights, and doping-induced reductions in the SB width are carefully evaluated to gain a better understanding of their impact on important device metrics.

Design and tailoring of two-dimensional Schottky, PN and tunnelling junctions for electronics and optoelectronics

Owing to their superior carrier mobility, strong light-matter interactions, and flexibility at the atomically thin thickness, two-dimensional (2D) materials are attracting wide interest for application in electronic and optoelectronic devices, including rectifying diodes, transistors, memory, photodetectors, and light-emitting diodes. At the heart of these devices, Schottky, PN, and tunneling junctions are playing an essential role in defining device function. Intriguingly, the ultrathin thickness and unique van der Waals (vdW) interlayer coupling in 2D materials has rendered enormous opportunities for the design and tailoring of various 2D junctions, e.g. using Lego-like hetero-stacking, surface decoration, and field-effect modulation methods. Such flexibility has led to marvelous breakthroughs during the exploration of 2D electronics and optoelectronic devices. To advance further, it is imperative to provide an overview of existing strategies for the engineering of various 2D junctions for their integration in the future. Thus, in this review, we provide a comprehensive survey of previous efforts toward 2D Schottky, PN, and tunneling junctions, and the functional devices built from them. Though these junctions exhibit similar configurations, distinct strategies have been developed for their optimal figures of merit based on their working principles and functional purposes.

A synaptic memristor based on two-dimensional layered WSe2 nanosheets with short- and long-term plasticity

Neural synapses with diverse synaptic functions of short- and long-term plasticity are highly desired for developing complex neuromorphic systems. A memristor with its two terminals serving as pre- and post-neurons, respectively, can emulate two neuronal-based synaptic functions. In this work, multilayer two-dimensional (2D) layered WSe₂ nanosheets are synthesized by a salt-assisted chemical vapor deposition (CVD) method. Two-terminal memristors with a planar structure are fabricated based on the CVD-grown triangular WSe₂ nanosheets. The fabricated devices exhibit typical bipolar nonvolatile resistive switching behaviors with a high current ON/OFF ratio of up to 6 × 10³ and good retention and endurance properties, suggesting good stability and reliability of the WSe₂-based memristors. Furthermore, the developed memristors demonstrate synaptic functions of short- and long-term plasticity (STP and LTP), as well as a transition from STP to LTP by applying consecutive pulse voltages. Moreover, the WSe₂-based memristors exhibits biological synaptic functions of long-term potentiation and depression, and paired-pulse facilitation. Thus, our 2D WSe₂ nanosheet based memristors not only exhibit stable and reliable nonvolatile resistive switching behaviors, but also show potential applications in mimicking biological synapses.

Embedment of Multiple Transition Metal Impurities into WS2 Monolayer for Bandstructure Modulation

Band structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach is proposed. Here, the growth of WS₂ monolayer is shown codoped with multiple kinds of transition metal impurities via chemical vapor deposition controlled in a diffusion-limited mode. Multielement embedment of Cr, Fe, Nb, and Mo into the host lattice is exemplified. Abundant impurity states thus generate in the bandgap of the resultant WS₂ and provide a robust switch of charging/discharging states upon sweep of an electric filed. A profound memory window exists in the transfer curves of doped WS₂ field-effect transistors, forming the basis of binary states for robust nonvolatile memory. The doping technique presented in this work brings one step closer to the rational design of 2D semiconductors with desired electronic properties.

Photoelectronic Properties of End-bonded InAsSb Nanowire Array Detector under Weak Light

A simple fabrication of end-bonded contacts InAsSb NW (nanowire) array detector to weak light is demonstrated in this study. The detector is fabricated using InAsSb NW array grown by molecular beam epitaxy on GaAs substrate. The metal-induced gap states are induced by the end-bonded contact which suppresses the dark current at various temperatures. The existence of the interface dipole due to the interfacial gap states enhances the light excitation around the local field and thus upgrades the photoresponsivity and photodetectivity to the weak light. The light intensity of the infrared light source in this report is 14 nW/cm² which is about 3 to 4 orders of magnitude less than the laser source. The responsivity of the detector has reached 28.57 A/W at room temperature with the light (945 nm) radiation, while the detectivity is 4.81 × 10¹¹ cm·Hz^1/2 W^-1. Anomalous temperature-dependent performance emerges at the variable temperature experiments, and we discussed the detailed mechanism behind the nonlinear relationship between the photoresponse of the device and temperatures. Besides, the optoelectronic characteristics of the detector clarified that the light-trapping effect and photogating effect of the NWs can enhance the photoresponse to the weak light across ultraviolet to near-infrared. These results highlight the feasibility of the InAsSb NW array detector to the infrared weak light without a cooling system.

Photoelectric Characteristics of a Large-Area n-MoS2/p-Si Heterojunction Structure Formed through Sulfurization Process

Two-dimensional (2D) materials, such as molybdenum disulfide (MoS₂) of the transition metal dichalcogenides family, are widely investigated because of their outstanding electrical and optical properties. However, not much of the 2D materials research completed to date has covered large-area structures comprised of high-quality heterojunction diodes. We fabricated a large-area n-MoS₂/p-Si heterojunction structure by sulfurization of MoO_x film, which is thermally evaporated on p-type silicon substrate. The n-MoS₂/p-Si structure possessed excellent diode characteristics such as ideality factor of 1.53 and rectification ratio in excess of 10⁴. Photoresponsivity and detectivity of the diode showed up to 475 mA/W and 6.5 × 10¹¹ Jones, respectively, in wavelength ranges from visible to near-infrared. The device appeared also the maximum external quantum efficiency of 72%. The rise and decay times of optical transient response were measured about 19.78 ms and 0.99 ms, respectively. These results suggest that the sulfurization process for large-area 2D heterojunction with MoS₂ can be applicable to next-generation electronic and optoelectronic devices.

P-N conversion of charge carrier types and high photoresponsive performance of composition modulated ternary alloy W(SxSe1-x)2 field-effect transistors

Transition metal dichalcogenides (TMDs) have emerged as a new class of two-dimensional (2D) materials, which are promising for diverse applications in nanoelectronics, optoelectronics, and photonics. To satisfy the requirements of the building blocks of functional devices, systematic modulation of the band gap and carrier type of TMDs materials becomes a significant challenge. Here, we report a salt-assisted chemical vapor deposition (CVD) approach for the simultaneous growth of alloy W(SxSe1-x)2 nanosheets with variable alloy compositions. Electrical transport studies based on the as-fabricated W(SxSe1-x)2 nanosheet field-effect transistors (FETs) demonstrate that charge carrier types of alloy nanosheet transistors can be systematically tuned by adjusting the alloy composition. Temperature-dependent current measurement shows that the main scattering mechanism is the charged impurity scattering. The effective Schottky barrier heights of bipolar W(SxSe1-x)2 transistors are initially increased and then decreased with increasing positive (or negative) gate voltage, which is tunable by varying the alloy composition. In addition, the tunability of these W(SxSe1-x)2-based ambipolar transistors is suitable for logic and analog applications and represents a critical step toward future fundamental studies as well as for the rational design of new 2D electronics with tailored spectral responses, and simpler and higher integration densities. Finally, the high photoresponsivity (up to 914 mA W-1) and detectivity (4.57 × 1010 Jones) of ultrathin W(SxSe1-x)2 phototransistors imply their potential applications in flexible light-detection and light-harvesting devices. These band gap engineered 2D structures could open up an exciting opportunity and contribute to finding diverse applications in future functional electronic/optoelectronic devices.

Interface engineering of two-dimensional transition metal dichalcogenides towards next-generation electronic devices: recent advances and challenges

Over the past decade, two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted tremendous research interest for future electronics owing to their atomically thin thickness, compelling properties and various potential applications. However, interface engineering including contact optimization and channel modulations for 2D TMDCs represents fundamental challenges in ultimate performance of ultrathin electronics. This article provides a comprehensive overview of the basic understanding of contacts and channel engineering of 2D TMDCs and emerging electronics benefiting from these varying approaches. In particular, we elucidate multifarious contact engineering approaches such as edge contact, phase engineering and metal transfer to suppress the Fermi level pinning effect at the metal/TMDC interface, various channel treatment avenues such as van der Waals heterostructures, surface charge transfer doping to modulate the device properties, and as well the novel electronics constructed by interface engineering such as diodes, circuits and memories. Finally, we conclude this review by addressing the current challenges facing 2D TMDCs towards next-generation electronics and offering our insights into future directions of this field.

Photogating WS2 Photodetectors Using Embedded WSe2 Charge Puddles

Performance of 2D photodetectors is often predominated by charge traps that offer an effective photogating effect. The device features an ultrahigh gain and responsivity, but at the cost of a retarded temporal response due to the nature of long-lived trap states. In this work, we devise a gain mechanism that originates from massive charge puddles formed in the type-II 2D lateral heterostructures. This concept is demonstrated using graphene-contacted WS₂ photodetectors embedded with WSe₂ nanodots. Upon light illumination, photoexcited carriers are separated by the built-in field at the WSe₂/WS₂ heterojunctions (HJs), with holes trapped in the WSe₂ nanodots. The resulting WSe₂ hole puddles provide a photoconductive gain, as electrons are recirculating during the lifetime of holes that remain trapped in the puddles. The WSe₂/WS₂ HJ photodetectors exhibit a responsivity of 3 × 10² A/W with a gain of 7 × 10² electrons per photon. Meanwhile, the zero-gate response time is reduced by 5 orders of magnitude as compared to the prior reports for the graphene-contacted pristine WS₂ monolayer and WS₂/MoS₂ heterobilayer photodetectors due to the ultrafast intralayer excitonic dynamics in the WSe₂/WS₂ HJs.

Graphene-Transition Metal Dichalcogenide Heterojunctions for Scalable and Low-Power Complementary Integrated Circuits

The most pressing barrier for the development of advanced electronics based on two-dimensional (2D) layered semiconductors stems from the lack of site-selective synthesis of complementary n- and p-channels with low contact resistance. Here, we report an in-plane epitaxial route for the growth of interlaced 2D semiconductor monolayers using chemical vapor deposition with a gas-confined scheme, in which patterned graphene (Gr) serves as a guiding template for site-selective growth of Gr-WS₂-Gr and Gr-WSe₂-Gr heterostructures. The Gr/2D semiconductor interface exhibits a transparent contact with a nearly ideal pinning factor of 0.95 for the n-channel WS₂ and 0.92 for the p-channel WSe₂. The effective depinning of the Fermi level gives an ultralow contact resistance of 0.75 and 1.20 kΩ·μm for WS₂ and WSe₂, respectively. Integrated logic circuits including inverter, NAND gate, static random access memory, and five-stage ring oscillator are constructed using the complementary Gr-WS₂-Gr-WSe₂-Gr heterojunctions as a fundamental building block, featuring the prominent performance metrics of high operation frequency (>0.2 GHz), low-power consumption, large noise margins, and high operational stability. The technology presented here provides a speculative look at the electronic circuitry built on atomic-scale semiconductors in the near future.