Seamless in two dimensions: prospects of lateral heterostructures from integration to quantum devices

Abstract

Lateral heterostructures of two-dimensional (2D) transition metal dichalcogenides feature atomically sharp, covalently stitched 1D interfaces that enable direct band-to-band coupling. This perspective highlights their unique ability to control quasiparticles, excitons, and spins, with implications for optoelectronics, excitonic and valleytronic devices, tunneling field-effect transistors, neuromorphic computing, spintronics, and quantum circuits. It also outlines challenges in scalable synthesis, interface engineering, and 2D–3D integration, charting paths toward future quantum technologies.

Introduction

The evolution of semiconductor technology has been instrumental in shaping modern electronics, from field-effect transistors (FETs), light-emitting diodes (LEDs), lasers, and power electronics to advanced optoelectronic, opto-spintronics, and quantum devices^{1,2,3,4,5,6,7,8}. Integrating diverse semiconducting materials has led to significant breakthroughs in quantum structures, such as superlattices and compound semiconductors, for efficiently manipulating charge carriers, excitons, polaritons, and their hybrids^9,10,11. While conventional semiconductor technology faces fundamental limitations in downscaling, integration, flexibility, and their efficacy for quantum technology necessitates unlocking new approaches in the post-Moore age^{3,12,13,14,15,16,17,18}. Two-dimensional (2D) materials provide a transformative platform, offering unique physicochemical properties, diverse crystal structures, layer-dependent bandgap, quantum confinement, strong light–matter interaction, and multiple degrees of freedom to control their collective characteristics. From graphene to transition metal dichalcogenides (TMDs) to magnets and beyond, a series of 2D materials has been explored and engineered to explore unconventional properties further^19,20,21. Efficient gate-electrostatic controllability, strong Coulomb exchange interaction, and minimal carrier-scattering due to dangling-bond-free surfaces at atomic thickness position 2D materials as a compelling alternative to existing silicon electronics, offering a pathway to sustain Moore’s law in the low power regime³. In TMDs, the emergence of a direct bandgap at the monolayer limit, combined with strong quantum confinement, tunable excitonic interactions, symmetry breaking, and pronounced spin-orbit coupling, gives rise to chiral physics through spin-valley coupling^{22,23,24,25,26,27}. These properties underpin various applications in quantum optoelectronics, electronics, spintronics, valleytronics, photonics, sensors, energy harvesting, and flexible devices^19,20,28,29.

Beyond their intrinsic electrical, optical, spin-valley, spin-photon, Berry-phase, and magneto-optics responses, 2D heterostructures offer tunable electro-optical functionalities via external perturbations such as electric and magnetic fields, strain, doping, defects, and chemical functionalization on demand^30,31. In addition to the intrinsic properties of individual 2D materials, heterostructures can be formed via van der Waals (vdW) stacking or lateral integration^19,32. Such precisely engineered 2D interfaces offer controlled light–matter, electron–electron, electron–phonon, electron–magnon, phonon–phonon, exciton–phonon, exciton–magnon, and exciton–polaron interactions^{33,34,35,36,37,38}, facilitating multi-functional applications and access to unconventional quantum phases^20,39. In vertical heterostructures (VHS), vdW forces enable stacking dissimilar 2D materials, allowing unprecedented design flexibility⁴⁰. The weak interlayer interaction facilitates precise control over stacking order, twist angle, and interlayer spacing, strongly influencing structure-property correlations and access to emergent phenomena. Moiré superlattices, engineered through rotational offset, lattice-mismatch, strain, and interlayer sliding, have emerged as a powerful platform for tuning electron mass renormalization and accessing correlated quantum phases in the flat band regime^36,41,42.

Top-down and bottom-up strategies represent the two primary approaches for fabricating 2D heterostructures. While the top-down method, based on exfoliation and restacking, is ideal for laboratory-scale research, bottom-up techniques offer scalability but require precise control over chemical kinetics during synthesis. Bottom-up methods are indispensable for lateral heterostructure (LHS), as edge epitaxy is needed for dissimilar materials across 1D interfaces. Unlike 3D materials, where synthesis challenges hinder seamless integration, the inherently dangling bond-free surfaces of 2D materials facilitate edge-epitaxial growth of different atomic layers within an LHS. However, chemical knitting is limited compared to vdW stacking due to the constraints imposed by lattice mismatch and interface coherence during lateral integration of different heterogeneous 2D materials. Recent advances^{43,44,45,46,47,48,49,50,51,52,53} in controlling chemical kinetics have opened new pathways for designing and synthesizing diverse LHS systems.

The seamless lateral integration of different 2D materials enables precise band engineering at 1D interfaces³¹, unlocking novel physics such as directional energy transport, exciton–polaron interactions, and spin-valley manipulation. Recent studies highlight their role in energy transport, Kapitza resistance-like exciton dynamics, and optically controlled valley filters or transistors for electrically tunable valley qubits, which are necessary to efficiently design quantum optical circuits for excitonic, photonic, and valley-selective applications^{54,55,56,57,58}. By carefully selecting material combinations, LHS allows for tailored band offsets, which could enable ultra-thin p-n junctions with significant potential in optoelectronics, including photodetectors, thermo-electric rectifiers, spin filters, modulators, optical synaptic devices, and quantum sensors.

This perspective delves into the emerging functionalities of LHS, addressing fabrication challenges and strategies to enhance their efficiency, sensitivity, and tunability. It highlights the distinct properties of LHS for the quantum engineering of electrons, photons, and excitons (Fig. 1). A comprehensive analysis of their significance is provided, addressing key challenges and outlooks in integrating 2D LHS into electronics, optoelectronics, and quantum technology (Fig. 1). Recent advancements in fabrication strategies are reviewed, emphasizing their importance for optimizing performance and scalability. This article aims to foster the mainstream adoption of LHS alongside their vdW counterparts by bridging fundamental physics with practical device implementation.

Fig. 1

A perspective of the potential of 2D lateral heterostructures, from in-plane synthesis, exotic exciton physics, confinements, and extending to applications in emerging optoelectronics and quantum technology.

Edge-epitaxial growth strategies by bottom-up approach

Material properties fundamentally determine their technological applicability, underscoring the importance of high-quality growth strategies for achieving scalability and tunability. The realization of LHSs necessitates in-plane atomic stitching, achievable only through bottom-up methods such as chemical vapor deposition (CVD), metal-organic CVD (MOCVD), and molecular beam epitaxy (MBE). The distinct physico-chemical functionalities of pristine 2D monolayers, VHSs, and LHSs of 2D materials are summarized in Table 1. For successful lateral epitaxy, precise control over adatom kinetics is crucial to confine their migration along the edges of a pre-grown template. Factors such as crystal symmetry compatibility and minimal lattice mismatch significantly facilitate seamless lateral epitaxy. Several studies have reported the successful synthesis of LHSs employing various growth strategies and material systems^{43,44,45,47,51,59,60,61,62,63,64,65,66,67,68,69} (Box 1). The sequential edge epitaxy for the growth of LHSs can be achieved via one-pot or multi-step strategies (Fig. 2a)^45,46,47,62. The one-pot CVD process offers advantages over multi-step methods by simplifying fabrication in situ. Still, it is prone to alloying and is restricted mainly to materials with similar structural characteristics. A two-step growth process can allow different TMDs to grow, but face the challenge of etching and degrading pre-grown TMD films. These growth strategies are also limited to single junctions since switching chemical sources instantly and protecting the initial island from thermal tolerance is difficult. During the temperature-swing stage, a reverse-flow reactor in the sequential vapor deposition growth process enables robust block-by-block epitaxial growth of diverse 2D heterostructures, multi-heterostructures, and superlattices⁶³.

Fig. 2: Various growth methods for fabricating multiple-junction LHSs.

a Direct synthesis followed by CVD and MOCVD, where changes in the in-situ or external environment control the deposition of the subsequent materials, resulting in multijunction LHS. b Laser patterning on as-grown TMDs, followed by chalcogenation or metallization of the exposed areas. c Initial TMD growth with metal dot arrays that act as nucleation sites for directional material deposition. d Heterostructures with distinct phases formed by selective doping and material deposition via in-situ carrier gas switching.

Still, it is limited to stability, controllability, and scalability. Controlling carrier gases, the selective evaporation of precursors, and the subsequent edge-epitaxy are robust and scalable strategies to realize multi-junction LHSs with excellent control over layer thickness, domain size, periodicity, and interface width^31,45,46,70. This process enables the formation of atomically sharp junctions, and by sequentially switching carrier gases, it can facilitate the growth of lateral superlattices without alloying.

Besides CVD with low-volatile bulk precursors, growth strategies based on high-volatile precursors such as MOCVD and halide CVD (HCVD) have also shown coherent lateral integration of 2D TMDs superlattices and LHS^62,71. MOCVD offers more controllability and back-end-of-line (BEOL) CMOS compatibility but suffers from carbon residues detrimental to electro-optical performance. While HCVD offers carbon-free atomic layers and LHS, effectively removing byproducts during the HCVD process is critical to ensure BEOL compatibility. Carbon contamination in MOCVD can be minimized by selecting appropriate organo-metal precursors or introducing a controlled H₂O vapor flow during the growth process⁷². Low H₂O concentrations suppress carbon incorporation, reduce TMD nucleation density, and promote larger grain growth, enhancing crystalline and electro-optical quality⁷². On the other hand, the HCVD process offers the deposition of carbon-free atomic layers and LHS due to the use of carbon-free metal-halide sources, which are reduced to metal under a H₂ environment⁷¹. However, the high processing temperature (>600 °C) requirement for complete reduction of metal-halides and effective removal of halide byproducts remains a critical challenge to BEOL compatibility of HCVD. Beyond isolated and random nucleation, 2D-LHS arrays are essential for large-scale integration and on-chip applications. Although the epitaxial growth by substrate engineering can offer a solution to control the nucleation density and orientation of the individual domains⁷³, large-scale 2D-LHS growth is limited in this approach due to lateral stitching of two different TMDs through edge-epitaxy. Few reports demonstrated arrays of TMDs via patterned masking, selective-area etching, followed by chalcogenation or re-growth (Fig. 2b)^53,64,74,75. However, this strategy is limited to a poor-quality interface due to undesired residues or degradation from conventional lithography and etching. Laser patterning and thermal etching of point defects in the pre-grown TMDs domain results in a well-defined active periphery for the endo-epitaxial mosaic growth of the heterogenous TMDs on the predefined triangular holes⁵¹, which can be scalable and applicable to the growth of mosaic arrays of different 2D-2D combinations. Pre-patterning via metal seeds and epitaxial growth could also lead to fabricating arrays of LHS (Fig. 2c)⁷⁶. Arrays of LHS devices are only possible by site-selective nucleation and uniform domain size growth over a large area. The seeded growth approach using metal seeds or pre-patterned TMDs on lithographically patterned substrates can offer a viable route to control domain placement and accessibility. However, challenges remain in confining metal precursors to predefined nucleation sites and maintaining uniform metal distribution during the lateral growth. The existing lithography techniques require refinement to pattern ~10 nm seeds with wide separations (100 s of µm) for scalable LHS device fabrication. Phase engineering offers additional control over tuning physicochemical properties for designing efficient quantum devices (Fig. 2d). Lateral integrations of homo-phase and hetero-phase LHSs were achieved during the CVD process^66,67,77. However, the quality and controllability of thermodynamic process parameters to incorporate different crystal structures are still limited. The ability of CVD methods to control, scale up, and uniform growth of 2D LHS opens remarkable opportunities where MBE strategies lack both cost-effectiveness and scalability¹⁹.

Phase-selective heterointegration is critical for controlling interfacial properties and enabling tunable device functionalities governed by unconventional quantum excitations. In CVD, phase transformations are typically induced via alkali metal interactions, thermal tolerance, alloying, electric field modulation, and strain engineering. However, these methods often suffer from interface defects, poor phase purity, and structural retransformation once external stimuli are removed. In contrast, the MBE offers a low temperature growth under high vacuum that ensures slow deposition rate, reduced thermal stress, and minimizes interfacial energy, facilitating precise in-plane phase selective heteroepitaxy. Recent demonstration of planar heterostructures such as of (1T)VSe₂-(1H)NbSe₂, (1H)CrSe₂-(1H)MoSe₂, CrTe₃-CrTe₂, NbSe₂-TiSe₂, CrTe₂/Bi(110) reveals exotic phenomena including Kondo resonances, nonreciprocal charge density wave, interfacial magnetic and topological states^{67,69,78,79,80}. These hetero-phased LHSs represent a promising route toward realizing emergent quantum phases in condensed matter systems. Despite significant advancements, challenges remain in site-selective and low-temperature growth, requiring compatibility with state-of-the-art IC technology (Box 2).

To date, the optimization of CVD synthesis conditions for 2D materials has primarily depended on time-intensive, trial-and-error approaches, often leading to extended development cycles, limited reproducibility, and inconsistent material quality⁸¹. These experimental iterations frequently involve costly, environmentally hazardous precursors and energy-intensive processes, resulting in considerable resource wastage and increased fabrication costs. Machine learning (ML)-guided synthesis frameworks are urgently needed to overcome these challenges. Such approaches have the potential to accelerate process optimization, enhance reproducibility, and minimize the economic and environmental footprint of 2D material production⁸². Realizing the full potential of CVD-grown 2D materials will require sustained research efforts in tandem with AI/ML integration to systematically map the complex process space, optimize growth conditions, and tailor material properties (Fig. 3). Empirically, over nineteen parameters can influence the target variables in 2D material synthesis via CVD, among which nine have been identified as particularly critical: (1) type of precursors and their amount (such as MX₂/WY₂ ratio, S_Mo/W), (2) reaction temperature (T), (3) growth time (t_D), (4) carrier gases (H₂, H₂O mixed with N₂ or Ar)), (5) gas flow rate, (6) pressure (P), (7) cooling condition (under H₂Se, H₂ or N₂ gas), (8) nucleation promoters, and (9) source to substrate distance (Fig. 3). These key variables significantly influence domain size, layer thickness, heterostructure morphology, and electrical and optical characteristics, such as photoluminescence (PL) characteristics, including emission wavelength, linewidth, and intensity, which collectively determine the quantum yield and overall performance of 2D optoelectronic and quantum devices.

Fig. 3: Design framework for the fabrication of 2D MX₂-M´Y₂ (M and M’ = Mo, W, Nb, Re, etc. and X, Y = S, Se, Te) lateral heterostructures via CVD methods, input features data sets, machine learning, target variables, and experiments to optimize the best CVD process parameters.

Left col. (insets), schematic representation of the CVD system used to fabricate 2D LHS, composed of two independent temperature zones, precursors, substrates, and carrier gases. Right col. (top) optical microscope image of a multi-junction 2D MoSe₂-WSe₂ lateral heterostructure grown via CVD and the corresponding photoluminescence spectra (bottom) obtained from individual domains.

Table 1 Qualitative understanding of the physico-chemical functionalities of pristine 2D material, vertical and lateral heterostructures.

ML can be integrated in a closed-loop framework that iteratively refines the synthesis conditions based on experimental feedback and model predictions to optimize critical growth parameters^83,84,85. Initially, ML models, such as neural networks, are trained on key input parameters (e.g., precursor type and amount, temperature, gas flow, pressure) along with output variables including domain size, layer thickness, nucleation density, and photoluminescence characteristics (e.g., peak shift, broadening, intensity). Once trained, these models can identify the most influential parameters and suggest optimal growth conditions. As the dataset expands with each experimental iteration, model accuracy improves, enabling high-throughput, data-driven process optimization. This ML-guided approach accelerates the discovery of ideal growth windows and improves reproducibility, yield, and scalability in 2D materials synthesis.

Box 1 Growth kinetics and mechanism for lateral epitaxy

Growth LHSs in CVD are formed through either one-step or two-step growth strategies. In the one-step approach, selective precursor evaporation enables seamless domain growth within a single chamber. In the two-step method, sequential growth is achieved by transferring the substrate between chambers. Precise control over temperature, precursor type, carrier gas, and pressure is crucial for achieving desired material quality, morphology, sharp interfaces, and uniformity.

• Role of precursor:

  The choice of precursor, whether bulk powder, transition metal oxide, or organic compound, significantly impacts the growth temperature, domain size, interfacial quality, and reproducibility¹⁹. Organometallic compounds offer low-temperature processing but often lead to unwanted carbon contamination. Bulk TMD precursors require high temperatures due to their high melting temperatures and diffusion limits, whereas transition metal oxide precursors with lower melting points and vapor pressures provide better control. However, reproducibility and poor interface quality are still critical to control.

• Temperature influence:

  Growth mode, vertical (VHS) vs. lateral (LHS), is governed by the interplay between thermodynamic and kinetic factors^43,45,46,47. Lower temperatures favor lateral stitching by suppressing vertical nucleation, while higher temperatures promote vertical stacking, which can be understood from the following mechanisms;

  • 1. Kinetics controlled

    The growth mode of LHS is governed by the kinetic coefficients associated with adatom-attachment (K_n-) and detachment (K_n+) at the pre-existing matrix-layer (n) edges, which is growth temperature (T_growth) dependent⁴⁶:

    $${{\rm{K}}}_{{\rm{n}}+}={{\rm{K}}}_{{\rm{n}}-}\exp (-{{\rm{V}}}_{{\rm{b}}}/{{\rm{k}}}_{{\rm{B}}}{{\rm{T}}}_{{\rm{growth}}})$$

    where V_b is the edge barrier energy. At lower temperatures (K_n+≪K_n-), the adatoms lack sufficient energy to surpass this edge barrier, favoring edge attachment and promoting lateral monolayer growth. At higher temperatures, as K_n+~K_n-, adatoms acquire enough energy to overcome the barrier, enabling simultaneous growth in both lateral and vertical directions, thereby promoting the formation of multilayer LHS.

  • 2. Surface-energy assisted

    The thermodynamic preference between LHS and VHS growth is determined by competing surface energy contributions, arising from edge bonding/chemical interactions and vdW forces⁴³:

    • Lateral growth (edge bonding): ${E}_{{lateral}}=\,\alpha L$

    • Vertical growth (vdW stacking): ${E}_{{vertical}}=\frac{\sqrt{3}}{4}$βL²

    where L is the domain length. The proportionality constants, α and β, correspond to the energies gained per unit length and unit area, respectively. While lateral growth is favored at small scales due to lower energy cost, vertical stacking becomes thermodynamically dominant at larger scales or higher temperatures, where vdW interactions outweigh edge energies.

  • 3. Supersaturation control

    According to classical nucleation theory, the Gibbs free energy change (ΔG) during nucleation at a heterointerface depends on the nucleus radius (r) and surface energy balance between the nucleus and the substrate (γ_c + γ_sc − γ_s). For a disk-shaped nucleus in monolayer crystals, this energy change can be described by the following equation⁴⁸:

    $$\mathrm{\varDelta G}({\rm{r}},{\rm{\gamma }})={{\rm{\pi }}{\rm{r}}}^{2}{\rm{t}}{\Delta {\rm{G}}}_{{\rm{V}}}+{{\rm{\pi }}{\rm{r}}}^{2}({\rm{\gamma }}{\rm{c}}+{\rm{\gamma }}\mathrm{sc}-{\rm{\gamma }}{\rm{s}})+{2{\rm{\pi }}\mathrm{rt}{\rm{\gamma }}}_{{\rm{c}},\mathrm{edge}}$$

    where r and t represent the radius and thickness of the nucleus; the γ_s, γ_c, γ_sc, and γ_{c, edge} represent the surface energy of the substrate, monolayer nucleus, interfacial, and edge surface energy per unit area of the monolayer nucleus, respectively. ΔG_V represents the volumetric free energy change during nucleation. In this expression, the first term accounts for the change in volume free energy, while the second and third terms represent the surface free energy contributions.

    • The nucleation rate (R) follows: ${\rm{R}} \sim \exp$(-$\frac{\Delta {G}^{* }}{{kT}}$)x$\exp \left(\frac{-\Delta {G}_{m}^{* }}{{kT}}\right)$

    Here, ΔG* is the nucleation energy barrier. Under sequential precursor exchange, ΔG^*_lateral>ΔG^*_vertical, meaning lateral nucleation is less favorable at high temperatures. As a result, increasing temperature lowers the energy barrier (ΔG^*) and enhances the nucleation rate (R) for VHS, while lower temperatures promote LHS formation.

• Metal to Chalcogen ratio

  The metal-to-chalcogen ratio (M/X) is critical in directing heteroepitaxial growth and determining whether lateral or vertical structures form⁵⁰. The competition between diffusion and deposition rates governs this. At lower M/X, low-energy adatom clusters favor edge diffusion and lateral nucleation along the crystal edge. In contrast, higher M/X ratios lead to a mixture of cluster species with broader energy distributions, promoting surface accumulation and a transition from lateral to vertical growth.

• Controlling the volatility of precursors and Carrier gas

  The variation in vapor pressures of gas-phase precursors enables selective evaporation, reaction, and sequential growth, facilitating LHS formation without altering core growth parameters⁴⁴. In the one-step method using metal oxides, temperature and duration of reaction control volatility for selective evaporation of precursors, guiding LHS growth. However, significant alloying at the interface leads to diffuse heterointerfaces. In situ source switching offers improved interface sharpness by enabling adatom attachment to unsaturated edge-dangling bonds of a pre-formed domain. The two-step growth strategy involving temporary interruptions during growth and ambient exposure of edges limits sequential lateral growth. To overcome these limitations, introducing a water-assisted one-pot CVD technique enables the continuous synthesis of multi-junction LHSs with controlled layer numbers by merely switching carrier gases in situ⁴⁵. This method is robust and simple, with the ability to produce high-quality optical and electronic-grade LHS, offering a scalable and cost-effective route toward industrial applications.

• Functionalization/patterning

  Temperature, selective defect creation, and chemisorption of a functionalized group, such as -OH, can be modulated on the surface or edge of the pre-grown monolayer, which regulates the growth of the subsequent atomic layer either in the lateral or vertical direction^51,52,53. Physical masking of the pregrown 2D layer and sequential chalcogenation also results in the LHS growth.

Box 2 Challenges in LHS growth

Achieving seamless covalent stitching of dissimilar 2D materials in LHS requires matched crystal symmetries and comparable precursor melting points to accommodate lattice and thermal mismatch. Several key challenges hinder scalable and device-ready LHS integration:

• 1. Metal cross-contamination: Cross-contamination of metal atoms is the primary challenge that a hot-walled CVD faces. While cold-walled CVD offers localized heating to suppress cross-contamination, it typically results in smaller domains and high nucleation density, limiting high crystallinity.

• 2. Lattice mismatch constraints: The edge epitaxial growth of LHS is restricted by stringent lattice matching, limiting the integration of diverse 2D materials. Overcoming this is essential for practical applications, including heterogeneous 2D/3D integration.

• 3. Scalable device arrays: Real-world applications require arrayed device architectures. This demands site-selective, nucleation-controlled growth strategies that offer both spatial precision and uniformity over large areas.

Exciton-spin-valley physics at 1D interface

In 2D semiconductors, reduced dielectric screening and strong Coulomb interaction enable the formation of various exciton species, even at room temperature²⁵. The optical response of most 2D TMDs, linear and nonlinear, is primarily dictated by excitonic resonances. Precise control over excitons in energy, spatial-temporal modulation, and transport is essential for designing efficient optical circuits in excitonic, photonic, and valley-selective quantum applications^{33,86,87,88,89,90,91,92}. Excitons in the 2D semiconductor can diffuse over tens of microns before dissociating (Table 2)^33,93. Key factors governing exciton diffusion include dipole–dipole repulsive interaction, concentration gradient, energy gradient, and thermalization^35,94,95,96. Additionally, efficient spin-valley coupling, confinement effects, and symmetry-breaking mechanisms introduce spin and valley degrees of freedom, imparting chirality to excitons in TMDs. This chiral physics in 2D excitonic systems enables unconventional functionalities, advancing their potential for quantum circuitry^97,98,99,100. However, achieving on-demand spatial and spin-valley selective directional exciton transport in 2D monolayers is challenging due to the absence of a preferential energy landscape. LHS with tailored band offset can create an asymmetric energy profile, guiding excitons directionally from higher to lower excitonic resonance regions across the 1D interface (Fig. 4a)^54,101. This controlled transport exhibits Kapitza resistance-like exciton dynamics across the interface, making LHS a promising platform for excitonic diodes and circuit design.⁵⁶ In LHSs with contrasting spin-valley coupling domains, such as the case of MoX₂ and WX₂, exciton and valley dynamics at the 1D interface exhibit intriguing behaviors. Distinct spin and valley polarization could harness optically or electrically tunable spin-valley transmission (Fig. 4b), analogous to chiral and Klein tunneling^55,102. The MoX₂-WX₂ LHS has been theoretically proposed as an optically controlled valley filter and valley transistor, where Floquet engineering via an off-resonant circularly polarized modulator facilitates spin- and valley-resolved transmission for photo-valleytronics and spin-excitonic applications⁵⁵. At the hetero-chiral 1D interface, exciton spin-polarization dictates transmission probability between domains.

Fig. 4: Different possible exciton-spin-valley configurations in a 2D lateral heterostructure platform.

a Directional exciton transport across 1D interface due to asymmetric energy landscape from higher to lower excitonic-resonance domain (WX₂ to MoX₂)⁵⁴. b optically (off-resonant circularly polarized excitation) or electrically controlled valley filter or valley transistor due to valley contrasting features across MoX₂-WX₂ LHS⁵⁵. c Gate defined quantum confinement of excitonic wave function due to a laterally engineered electric field defined confining potential, reproduced from ref. ^95,96 with permission from Springer Nature and Science publishing group. d Variation of exciton density distribution across a 1D interface showing exciton lensing or collimation effect. e Electrically controlled valley qubit via gate-defined momentum profile to tunable quantum states.

Table 2 Exciton-diffusion length in different material configurations

Beyond transport control, spatial confinement of excitons is critical for designing quantum emitters, from single-photon sources to scalable arrays^33,103. The development of high-quality LHS based on TMDs presents exciting opportunities for confining excitons in 1D. Several strategies for exciton confinement in TMD semiconductors are being explored, including electrostatically defined potentials using patterned gate electrodes^95,96,104, strain-induced confinement^105,106, and dielectric engineering^94,107,108. Among these, lithographically patterned gates have enabled scalable and tunable confinement in 1D and 0D geometries (Fig. 4c). Exciton confinement is particularly interesting for nonlinear optics, as spatially localized excitons exhibit enhanced interaction effects and reduced susceptibility to disorder-induced inhomogeneous broadening. Moreover, scalable and tunable confinement schemes are highly desirable for integration into quantum photonic circuits—especially as potential platforms for on-demand single-photon sources. Lateral TMD heterostructures provide a powerful and versatile platform to revisit and combine exciton confinement strategies within a novel in-plane architecture. A persistent challenge in conventional vertical heterostructures is the presence of background excitonic states that lie close in energy to confined excitons, making it difficult to spectrally isolate and study the desired nonlinear optical transitions. LHSs naturally address this issue by offering clean, atomically sharp interfaces that spatially separate regions with distinct band alignments. For example, narrow MoSe₂ channels embedded within WSe₂ domains (or vice versa) can act as 1D quantum wires with strongly reduced background emission. These heterojunctions confine excitons along one spatial dimension by design, allowing efficient confinement along the orthogonal direction using additional techniques such as electrostatic gating or strain. Moreover, the observation of discrete excitonic states in 1D channels, as well as the dependence of such discretization on channel width, presents an intriguing question for further exploration in such devices. This built-in directional confinement significantly simplifies device design. In traditional gate-defined quantum dot architectures, achieving 0D confinement often requires complex geometries, such as bow-tie electrode configurations, and multiple gate electrodes to control individual excitonic sites. In contrast, in 2D LHS, the lateral interfaces already provide confinement in one dimension, enabling strong 0D confinement with as little as a single gate. This not only eases fabrication requirements but also enhances the scalability of such systems for integration into photonic or quantum devices. Recent work demonstrates gate-defined lateral p-i-n geometries, confining excitons to ~10 nm in 2D TMDs, paving the way towards electrically controlled exciton quantization for the on-chip photonics^95,104,109. However, scaling such architecture remains challenging. MoX₂-WX₂ LHS, featuring an intrinsic p-n junction, provides a natural platform for exciton confinement and 1D exciton channels. Strategically combining multiple lateral junctions could effectively control exciton density, flux, and their diffusion length, facilitating active modulation of in-plane exciton transport. The spatial arrangement of 1D interfaces plays a key role in enabling exciton collimation and trapping (Fig. 4d).¹¹⁰Multi-junction LHS with periodic p-n junctions can provide electrically controlled exciton trap arrays. These in-plane heterojunctions introduce periodic energy modulation, supporting the formation of 1D exciton lattices and efficient exciton-photon coupling for designing 1D exciton-polariton lattices. A recent theoretical study demonstrated that gate-defined electron confinement and modulating the dipolar potential crossover across a sharp 1D junction can design all electrically controllable valley qubits in an LHS (Fig. 4e)⁵⁷. Gate-defined modulation of the momentum profile within the confinement potential and intervalley transitions, dependent on effective overlapping of junction potential with confinement profile and intervalley transitions, dependent on effective overlapping of junction potential with confinement profile, enables valley isospin qubits and tunable quantum states⁵⁷. The current advancements in exciton and intervalley physics establish LHS as a bridge between quasiparticle dynamics and quantum technology, driving progress in optoelectronics and quantum computing.

Optoelectronic properties of 2D LHS-based FETs

Harnessing exciton control and transport in 2D heterostructures paves the way for transformative advances in on-chip photonics and electronics. Precise generation and manipulation of exciton complexes were achieved using an encapsulated 1 L MoSe₂-WSe₂ LHS FET device geometry with graphene as contacts.¹¹¹ The synergistic effects of localized electric fields and interface phenomena profoundly modulate excitons and trions, leading to spatially controlled variation in their densities under external electrical influence (Fig. 5a). Furthermore, high-density and localized quantum emitters within the LHS can be finely tuned through precise carrier injection and electrical biasing, promising for realizing spatially and spectrally tunable single-photon sources (Fig. 5b). The controlled tunability of FET geometries based on 2D LHSs demonstrates multifunctionality in electrically manipulating excitonic characteristics¹¹². Unlike traditional vertical heterostructures, LHS-based devices enable preferential exciton generation and manipulation without relying on external potential confinement. The in-plane FET geometry with built-in potential asymmetry facilitates spontaneous exciton diffusion and enables domain-specific carrier generation and transport across the interface.

Fig. 5: Interfacial optoelectronics characteristics in 2D Lateral Heterostructure.

a A distinctive interfacial characteristic of an LHS is explored through laser irradiation near the junction region of a 1 L LHS, functioning as a quantum particle detector. The PL intensity profiles (middle) reveal trion (X⁺) intensity dominates at the junction, while neutral excitons (X₀) prevail in the central MoSe₂ region. A band diagram (right) illustrates this behavior, which depicts the formation of charge-transfer-induced trions proximate to the interface.¹¹¹ b Deterministic and spatially distributed quantum emitters across a 1D interface. c Schematic of an electroluminescence (EL) device illustrating the recombination of electrons and holes at the interface under external bias. An optical image of a 1 L WSe₂-MoS₂ device is shown, along with the EL map of the device under forward bias, highlighting the maximum EL intensity at the lateral junction (bottom).²¹⁶ The EL response at room temperature from a 2 L MoS₂-WS₂ LHS is presented in the right panel.⁴⁶ d Illustrations of piezoelectric and flexoelectric effects on 1 L LHS, where P_F and P_P are the flexoelectric and piezoelectric polarizations, respectively. The band diagrams of the lateral interface under small and large compressive (top row) and tensile (bottom row) strains. With minor strain, the band offset (ΔE_C and ΔE_V) increases, and the depletion zone shrinks. A large strain lowers the band energy levels and expands the depletion zone¹¹⁷.

Electroluminescence (EL) from 2D TMDs offers a pathway to high-performance, miniaturized, and energy-efficient quantum devices, including displays, single photon emitters, and detectors^8,113. The atomically sharp interfaces of 2D LHS minimize defect states, reducing non-radiative recombination^58,114 and enhancing EL efficiency. Engineering device geometry on monolayer WSe₂ homo p–n junction enables electrically confined neutral exciton-driven EL emission at the interface¹¹⁵. However, the overall quantum efficiency remains low, and scalability remains challenging. Bilayer LHSs, compared to their monolayer counterparts, exhibit superior environmental stability and improved electrical performance, leading to enhanced photovoltaic response¹¹⁶ and room-temperature EL (Fig. 5c).⁴⁶ Electrical control of excitonic recombination enables precise tuning of spectral width and emission. Advancing photosensors through piezoelectric and flexoelectric effects opens new avenues for wearable devices¹¹⁷. In a monolayer MoSe₂−WSe₂ LHS, band alignment at the interface enhances electromechanical optoelectronic efficiency by enabling a tunable built-in electric field (Fig. 5d). Under external strain, the combined flexoelectric and piezoelectric effects boost photoelectric conversion and regulate the photosensor performance, expanding the potential of LHS for flexible and low-light detection applications.

Quantum engineering of 2D LHS FET

As outlined in the International Technology Roadmap of Semiconductor, advancements in device architectures, including Gate-All-Around structure, 3D monolithic integration, and novel channel materials^16,118, are being pursued to sustain ongoing miniaturization and meet the demands of next-generation electronics. 2D heterostructures are revolutionizing electronic devices, enabling FETs with high on/off ratios, energy-harvesting systems, and low-power TFETs while paving the way for energy-efficient computing, neuromorphic circuits, and flexible electronics. Their continued integration promises transformative advancements across multiple fields. LHS could offer a unique platform to overcome thermal limitations in conventional semiconductors by enabling intrinsic heat management without relying on external dissipation channels (Fig. 6a).^119,120 The plot compares the thermal conductivity measured along two opposite heat flow directions from MoSe₂ to WSe₂ (J⁺) and from WSe₂ to MoSe₂ (J^-) across a temperature range. In the J⁺ direction, heat is conducted significantly more efficiently with thermal conductivity values consistently higher than in the reverse direction. This asymmetry arises from better phonon spectral overlap and interfacial transmission when heat flows from MoSe₂ to WSe_2, whereas phonon scattering and mismatch dominate the reverse path. Their electro-thermal rectification behavior can be tuned via junction orientation. Designing high-performance 2D integrated devices will further require optimization of key metrics such as high ${I}_{{on}}/{I}_{{off}}$ ratio, carrier mobility, and low leakage current. 2D TMD-based LHSs have gained significant attention for their superior electrostatic control and energy-efficient operation, making them well-suited for seamless integration into advancing CMOS technology^118,121. LHS-based devices exhibit a higher I_on/I_off ratio than their vertical counterparts due to superior gate electrostatic control across the entire channel. In-plane carrier transport in LHS allows efficient gate modulation of the potential barrier, resulting in a steeper subthreshold swing (SS) and lower off-state current, key factors for fast and energy-efficient switching. In contrast, VHS suffers from electrostatic screening, where layers closer to the gate electrode partially shield the electric field, reducing controllability.

Fig. 6: Schematic illustration and operational characteristics of devices based on 2D Lateral Heterostructure geometry.

a Schematic of an external thermal measurement circuit based on a MoSe₂-WSe₂ LHS. V₁ and V₂ measure the voltage of the two gold sensors (Au), while I₁ and I₂ measure the current in each loop. The blue and red arrows indicate the thermal conductivity directions, J⁺ from MoSe₂ to WSe₂ and J^- from WSe₂ to MoSe_2, respectively, reproduced from ref. ¹¹⁹ with permission from Science Publishing. b Device schematic for LHS-based tunneling field effect transistors (LHS-TFET) and vertical heterostructure TFETs (VH-TFET), illustrating the band profile in the ON and OFF states. Key figures of merit, including on-state current (I_on), off-state current (I_off), tunneling efficiency, etc., are tabulated to emphasize performance metrics. c Schematic representation of LHS-based heterojunction bipolar transistor (HBT) along with the typical current–voltage (I–V) characteristics (citation with copyright). The figures of merit, including the cut-off frequency, base transit time, injection efficiency, base transport factor, current gain, and cut-off frequency, are required parameters for high-speed and high-frequency performance, reproduced from ref. ¹⁴³ with permission from ACS Publishing.

Additionally, vdW gaps in stacked geometries introduce additional stray capacitance, adversely affecting switching speed and energy efficiency. These key figures of merit dictate effective switching behavior and overall power consumption. FETs based on LHS have demonstrated a promising ${I}_{{on}}/{I}_{{off}}$ ratio, comparable to transistors developed using vertical heterostructure and 3D semiconductors at similar scaling^122,123,124. LHS integrating graphene and TMDs, particularly in top-gate FETs with graphene as the source/drain and MoS₂ as the channel¹²⁵, have demonstrated an impressive ${I}_{{on}}/{I}_{{off}}$ ratio of ~10⁹ and a maximum transconductance (${g}_{m}$) of 6 μS. These devices exhibit superior mobility compared to MoS₂-based counterparts, while LHS-based logic circuits achieve a voltage gain of ~70, comparable to 3D NMOS technology.¹²⁶ Heterogeneous NbS₂-WS₂-based FETs exhibit n-type behavior with an on/off ratio of 10⁵.¹²⁷ While field-effect mobility is modest at 0.14 cm²/V s, further optimization could enhance performance. The interface quality of the LHSs significantly influences transport characteristics in FET devices. Optimizing specific growth methods is crucial for higher on/off ratios and enhanced mobility.⁴⁵ Flexible electronics, such as rectennas¹²⁸ for harvesting Wi-Fi energy and e-skin sensors, demonstrate the potential of 2D LHS for novel and efficient technologies. Resonators based on graphene–hBN LHS function as bandpass filters and can be adapted for amplifiers or multipliers in high-frequency applications.¹²⁹ The evolution of transistors, including TFETs¹³⁰, Dirac source FET¹³¹, and hot electron transistors¹³², is driven by the need for ultra-thin materials with high mobility, for which 2D heterostructures could overcome the limitations of conventional 3D semiconductors.

The continued scaling of the FET channel materials aims to enhance the switching speed of processors but remains constrained by the thermionic limit. TFETs offer a promising solution for low-power applications, with performance reliant on key figures of merit for optimization (Fig. 6b). A lower SS is highly desirable for sharper switching, enhancing speed and efficiency, while a low threshold voltage (${V}_{{th}}$) is essential for low-power applications, ensuring effective operation at reduced power levels. Maximizing the on-state current (${I}_{{on}}$) enhances transistor performance while minimizing the off-state current, (${I}_{{off}}$), which reduces the power leakage in the “off” state. Energy Delay Product (EDP) is a crucial metric that balances the trade-off between speed and energy efficiency. Minimizing gate leakage current prevents unnecessary power loss, while strong scaling potential ensures TFET performance remains consistent as device dimensions shrink.

A critical factor affecting the SS is band-edge smearing caused by Urbach tails, which is significantly suppressed in 2D materials due to their low deformation potential and weak electron–phonon interaction. Quantum tunneling, fundamental to TFET operation, is characterized by tunneling efficiency, quantifying how effectively carriers tunnel through the potential barrier. Material selection is equally critical, as reflected in the metric material requirements, ensuring optimal TFET design. As device scaling continues, controlling Short Channel Effects (SCEs) becomes essential to maintaining performance and mitigating undesired impacts. Other key considerations in TFET design include manufacturability, which influences large-scale adoption, and a wide operating temperature range, ensuring broad applicability. Together, these metrics provide a comprehensive framework for evaluating and optimizing TFET performance towards advanced energy-efficient transistor technology. 2D heterostructures with atomically sharp interfaces and tunable electronic and optical properties are ideal for optimizing TFET performance¹³³.

2D black phosphorus (BP) possesses high carrier mobility and low dielectric constant,¹³⁴ while its bilayer form provides extended tunneling length, enabling reduced OFF-state current and enhanced device performance¹³⁵. TFETS based on BP/MoS₂ heterostructures have demonstrated ON/OFF ratios up to 10⁶ and SS near 55 mV/dec¹³⁶, while WSe₂/SnSe₂ and Ge/MoS₂ VHSs have achieved SS values as low as 35 mV/dec¹³⁷, and 3.9 mV/dec,¹³⁸ respectively. Despite these advances, VHS typically suffer from higher SS_min due to weaker electrostatic gating and fixed tunneling widths. LHS offers a key advantage by allowing tunable tunneling width via band bending, enabling lower SS_min and better gate control¹²¹. Environmental and chemical stability remain concerns for pure 2D systems, prompting the exploration of hybrid 2D–3D TFETs, such as Si/MoS₂ HS that yield low SS (15 mV/dec) and high ON/OFF ratios (~10⁷)¹³⁹.

Structural design plays a critical role in tunneling efficiency, with sensitivity to the junction area, layer orientation, and lattice matching¹⁴⁰. Novel device architectures such as Z-shaped TFETs¹⁴¹ enhance the tunneling area and suppress parasitic leakage currents, improving RF performance. Meanwhile, L-shaped TFETs¹⁴² improve interband tunneling, leading to higher device efficiency. Various TFET architectures comprising the SS performance of LHS-based designs over their vertical and hybrid counterparts were summarized in Table 3. Among these, lateral BP–WSe₂ and BP–WTe₂ TFETs demonstrate exceptional SS, especially when combined with electrostatic or charge-transfer doping. These configurations benefit from tunable tunneling widths and enhanced electrostatic screening due to their proximity to gate dielectrics, resulting in sharper switching and lower OFF-state currents¹²¹. Integrating LHS with gate-all-around (GAA) architectures would present a promising TFET design evolution. This hybrid design could unify the benefits of lateral TFETs, such as scalable junction control and anisotropic transport, with the electrostatic superiority of GAA structures, offering enhanced short-channel control and energy efficiency. Material choice and architectural innovation will be central to advancing TFET performance for next-generation low-power electronics.

Table 3 Comparison of TFET architectures highlighting the subthreshold swing (SS) and performance across lateral, vertical, and hybrid designs.

By utilizing the unique electronic, thermal, and optical properties, 2D heterojunction bipolar transistors (HBT) and resonant tunneling diodes achieve advantages in scaling, speed, and improved energy efficiency, as shown in Fig. 6c. The inbuilt potential across the in-plane LHS interface controls the transport of the carrier. The prototype lateral npn (MoS₂-WSe₂-MoS₂) device demonstrated a gain of 3 in the common emitter configuration¹⁴³. Despite challenges in material quality and device integration, progress in heterostructure design, interface engineering, and large-scale fabrication is advancing 2D HBTs toward practical implementation. Their potential for high-frequency, low-power, and flexible electronics, spintronics, and opto-spintronics positions them as key components in future electronic and optoelectronic devices.

Lateral spin transport, conversion, and manipulation

Spintronics, an emerging field in condensed matter physics, exploits the intrinsic spin of electrons and their associated magnetic moment for information processing. Compared to charge-based electronics, spintronics offers advantages such as lower power consumption, faster processing speeds, and non-volatility. Among various material platforms, 2D materials have gained significant attention for spintronics due to their tunable electronic properties, high carrier mobility, and long spin diffusion lengths, making them highly suitable for next-generation spintronic devices¹⁴⁴. One of the key challenges in 2D spintronics is efficient spin manipulation, which is typically weak in pristine materials like graphene. However, this limitation can be overcome by proximity-induced spin-orbit coupling (SOC), where a nonmagnetic 2D material with weak SOC (e.g., graphene) is interfaced with a material possessing strong SOC (e.g., TMDs)¹⁴⁵. This interaction enables spin-charge conversion (SCC) effects such as the spin Hall effect (SHE) and Rashba-Edelstein effect (REE), both of which play essential roles in next-generation spintronic devices (Fig. 7a). The REE arises from interfacial SOC, leading to spin accumulation in response to an applied charge current. In contrast, the SHE generates transverse spin currents due to bulk SOC interactions¹⁴⁶. In adittion the valley-dependent SOC in TMDs such as MoS₂ and WSe₂ introduces another degree of freedom, enabling control over spin and valley transport.

Fig. 7: Spin-orbit effects and spin-charge conversion mechanisms in lateral 2D heterostructures.

a Rashba–Edelstein effect and valley-dependent spin–orbit coupling in graphene/TMD interfaces. b Spin injection from ferromagnets into graphene/TMD heterostructures with spin precession. c Omnidirectional spin–charge conversion for x-, y-, and z-polarized spin currents. d Inverse spin Hall effect (ISHE) converting spin current to charge current. e Gate-tunable spin-charge conversion via Fermi level tuning in graphene/TMDs.

LHS could provide an additional platform for spin functionality (Fig. 7b). Unlike vertical stacks, LHS enables direct atomic bonding, enhancing interfacial coupling and proximity effects¹⁴⁷. This arrangement leads to spatially varying SOC and facilitates emergent spintronic phenomena like chiral spin filtering, directionally controlled spin flow, and gate-tunable interconversion of spin and charge¹⁴⁸. One of the primary consequences of SOC in LHS is the manifestation of spin-to-charge interconversion (SCI) through mechanisms such as the SHE and its inverse, the ISHE (Fig. 7c). In high-symmetry materials like platinum, the SHE generates spin currents orthogonal to both charge current and spin polarization. However, in low-symmetry TMDs like MoTe₂, unconventional, non-orthogonal geometries have been observed due to crystalline anisotropy. These configurations expand the design flexibility for detecting and manipulating spin information in devices.

Graphene-TMD heterostructures serve as prototypical systems for SCC exploration (Fig. 7d). In graphene/MoS₂ or graphene/WSe₂ stacks, graphene acquires induced SOC from the adjacent TMD, enabling a gate-tunable SHE that persists at room temperature. In MoTe₂-based LHS, multidirectional spin-to-charge conversion has been reported, showcasing room-temperature performance and electric-field tunability. Furthermore, chiral charge density waves (CDWs), as observed in 1T-TaS₂, introduce additional tunability in SCC via lattice symmetry breaking. This mechanism provides new avenues for phase-dependent spintronic switching and signal modulation. While the SHE is essential for generating spin currents, the ISHE facilitates their detection by converting spin currents into transverse charge signals—this is crucial for reading out spin logic states. In lateral systems like graphene/NbSe₂ and graphene/MoTe₂, ISHE occurs in non-orthogonal geometries due to broken inversion symmetry, which has been experimentally verified. Notably, omnidirectional spin-charge conversion has been demonstrated in these systems, showing equal conversion efficiency for spin currents polarized along the x-, y-, and z-directions, making them ideal for advanced spin logic where spin orientation control is impractical¹⁴⁹. Beyond the SHE and ISHE, the REE provides a complementary interfacial mechanism. In graphene/TMD LHS, interfacial SOC can lead to REE-driven spin polarization aligned along the charge current direction¹⁵⁰. Such REE signatures have been detected up to room temperature and are further enhanced in twisted TMD structures like graphene/WTe₂ and graphene/MoTe₂¹⁵¹.

Gate-tunable SCC is essential for device applications. In graphene/WSe₂, for example, electrostatic gating can modulate the Fermi level and maximize the conversion efficiency near the Dirac point (Fig. 7e). Similarly, in MoTe₂ and NbSe₂-based systems, omnidirectional spin-charge conversion has been demonstrated with voltage control, supporting reconfigurable and nonvolatile logic architectures. Despite these advances, challenges remain in the synthesis and scalability of LHS. Achieving atomically sharp interfaces without defects or lattice mismatches remains nontrivial. Additionally, efficient spin injection and detection are still limited by interface scattering and spin relaxation losses¹⁵². Potential solutions include integrating 2D ferromagnets, magnetic topological insulators, and novel magnetic electrodes¹⁵³. Further refinement in materials growth, spin-sensitive characterization, and theoretical modeling is needed to realize functional quantum spintronic systems. Nevertheless, lateral 2D heterointegration is a promising platform for future spin-based computing and memory technologies, enabling dynamic, all-electrical control over spin currents in scalable geometries.

Quantitative analysis of charge and spin transfer in lateral 2D heterostructures

The quantum functionalities of 2D LHS are fundamentally governed by the efficiency and dynamics of charge and spin transfer processes across their interfaces^58,154. While qualitative understanding of these transport mechanisms has advanced significantly, quantitative characterization remains essential for establishing design principles and performance benchmarks for next-generation spintronic devices^19,155. The complex interplay between interfacial coupling, proximity effects, and quantum transport phenomena requires systematic analysis of key parameters, including charge transfer rates, spin injection efficiencies, spin-orbit coupling strengths, and interface-dependent properties.

Recent experimental advances have enabled precise quantification of these transport parameters across various material systems, revealing the critical role of interface quality, material selection, and external control mechanisms in determining device performance^20,156. Charge transfer processes occur on femtosecond to picosecond timescales^157,158, with transfer efficiencies ranging from 0.1 to several electrons per interface, depending on the material combination and coupling strength. Spin transport phenomena exhibit remarkable tunability, with spin lifetimes extending from picoseconds to nanoseconds and diffusion lengths reaching tens of micrometers in optimized systems¹⁵⁹.

The following comprehensive analysis (Table 4) presents quantitative data for charge and spin transfer processes in lateral 2D heterostructures, providing essential benchmarks for understanding quantum transport phenomena and guiding the development of practical spintronic and quantum computing applications¹⁶⁰. These parameters establish the foundation for rational design of LHS devices with optimized transport characteristics and controllable quantum functionalities¹⁹.

Table 4 Comprehensive Quantitative Parameters for charge and spin transfer process for 2D Heterostructures

Outlook

2D heterostructures represent a rapidly evolving class of atomically engineered materials with immense potential for transforming modern electronics, optoelectronics, and quantum technologies. Unlike vertical heterostructures, LHSs offer seamless, in-plane interfaces with high structural coherence and spatially separated domains. The presence of sharp 1D junctions facilitates directional control of charge and exciton flow, precise band alignment, and tunable quasiparticle interactions.

In optoelectronics, LHSs offer finely tunable photoresponse, polarization control, and broadband sensitivity, enabling applications in photodetectors, light-emitting diodes, modulators, and integrated photonic circuits. Their ability to confine excitons, control emission spectra, and support negative and positive photoconductivity through external stimuli also opens new opportunities for reconfigurable and multimodal photonic devices.

From a quantum technology perspective, LHSs provide an exciting platform for engineering spin, valley, and exciton degrees of freedom. These can be harnessed to develop single-photon emitters, valley filters, and electrically tunable quantum light sources. The emergence of gate-defined excitonic confinement and directional exciton transport along 1D interfaces suggests a path toward scalable quantum circuits and all-electrical control of quantum states, a crucial milestone in integrated quantum photonics.

An exciting direction for future research lies in integrating laterally confined excitonic systems with photonic architectures. The ability to engineer 1D channels that support neutral and charged excitons—combined with precise electrostatic control—makes these structures highly suitable for coupling to confined photonic modes. Embedding such channels within optical microcavities, photonic crystals, or waveguides could significantly enhance light–matter interaction and open access to new regimes of exciton-polariton physics. A particularly promising approach is incorporating these 1D excitonic channels into photonic waveguides. Since LHS can support channel lengths on the order of 100 microns, integrating them with guided optical modes offers a new platform for exploring strong coupling and enhanced optical nonlinearities. This geometry is especially well-suited to probe phenomena predicted in recent theoretical studies of one-dimensional polaritonic gases, including interaction-driven effects and collective excitations. Beyond fundamental studies, such integrated systems could also lead to novel optoelectronic devices that leverage strong exciton–photon interactions in compact, scalable architectures.

The unique capabilities of LHSs are expected to play a pivotal role in developing future nanoelectronic and integrated circuit technologies. Their inherently superior electrostatic gate control, reduced short-channel effects, and compatibility with atomically thin geometries will make them ideal candidates for next-generation transistors, including TFETs and beyond-CMOS logic architectures. As device scaling progresses, LHS-based transistors are anticipated to enable low-power operation with high on/off ratios—meeting the performance and energy efficiency demands of emerging computing paradigms such as neuromorphic and edge computing. According to the international roadmap, 2D LHSs will likely emerge as key enablers of high-performance CMOS technology, complementary to Si, offering effective delay time and power-delay products. Their planar geometry is well-suited for seamless integration into advanced IC platforms, while their structural versatility could facilitate innovative device designs. In addition, when combined with vertical 3D stacking, LHSs are expected to contribute significantly to increasing transistor density, thereby supporting continued progress in semiconductor scaling and performance enhancement.

Despite their promise, several challenges must be addressed to unlock the full potential of LHSs. These include scalable and reproducible growth, precise control over interface sharpness, defect passivation, and compatibility with BEOL processing. Bottom-up synthesis strategies, especially CVD and MOCVD, remain central to large-scale fabrication, but further chemical kinetics and interface engineering refinement are required. Emerging approaches that integrate AI/ML for growth optimization and in-situ diagnostics for real-time monitoring could accelerate the transition from laboratory prototypes to manufacturable device platforms.

In conclusion, 2D LHSs stand at the frontier of materials innovation, offering a versatile and tunable platform that bridges fundamental quantum phenomena with practical device applications. Continued interdisciplinary efforts across materials science, physics, and engineering are expected to drive transformative advances in low-power electronics, multi-functional optoelectronics, and quantum information technologies.