Browsing by Author "Bai, Xueyin"
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Item Chirality logic gates(AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE, 2022-12-07) Zhang, Yi; Wang, Yadong; Dai, Yunyun; Bai, Xueyin; Hu, Xuerong; Du, Luojun; Hu, Hai; Yang, Xiaoxia; Li, Diao; Dai, Qing; Hasan, Tawfique; Sun, Zhipei; Department of Electronics and Nanoengineering; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTF; National Center for Nanoscience and Technology Beijing; University of CambridgeThe ever-growing demand for faster and more efficient data transfer and processing has brought optical computation strategies to the forefront of research in next-generation computing. Here, we report a universal computing approach with the chirality degree of freedom. By exploiting the crystal symmetry–enabled well-known chiral selection rules, we demonstrate the viability of the concept in bulk silica crystals and atomically thin semiconductors and create ultrafast (<100-fs) all-optical chirality logic gates (XNOR, NOR, AND, XOR, OR, and NAND) and a half adder. We also validate the unique advantages of chirality gates by realizing multiple gates with simultaneous operation in a single device and electrical control. Our first demonstrations of logic gates using chiral selection rules suggest that optical chirality could provide a powerful degree of freedom for future optical computing.Item Coherent modulation of chiral nonlinear optics with crystal symmetry(Springer Nature, 2022-07-08) Zhang, Yi; Bai, Xueyin; Arias Muñoz, Juan; Dai, Yunyun; Das, Susobhan; Wang, Yadong; Sun, Zhipei; Department of Electronics and Nanoengineering; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTFLight modulation is of paramount importance for photonics and optoelectronics. Here we report all-optical coherent modulation of third-harmonic generation (THG) with chiral light via the symmetry enabled polarization selectivity. The concept is experimentally validated in monolayer materials (MoS2) with modulation depth approaching ~100%, ultra-fast modulation speed (<~130 fs), and wavelength-independence features. Moreover, the power and polarization of the incident optical beams can be used to tune the output chirality and modulation performance. Major performance of our demonstration reaches the fundamental limits of optical modulation: near-unity modulation depth, instantaneous speed (ultra-fast coherent interaction), compact footprint (atomic thickness), and unlimited operation bandwidth, which hold an ideal optical modulation solution for emerging and future nonlinear optical applications (e.g., interconnection, imaging, computing, and quantum technologies).Item Deterministic Modification of CVD Grown Monolayer MoS2 with Optical Pulses(WILEY-BLACKWELL, 2021-05-21) Turunen, Mikko T.; Hulkko, Eero; Mentel, Kamila K.; Bai, Xueyin; Akkanen, Suvi Tuuli; Amini, Mohammad; Li, Shisheng; Lipsanen, Harri; Pettersson, Mika; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Atomic Scale Physics; Harri Lipsanen Group; University of Jyväskylä; National Institute for Materials ScienceTransition metal dichalcogenide monolayers have demonstrated a number of exquisite optical and electrical properties. Here, the authors report the optical modification of topographical and optical properties of monolayer MoS2 with femtosecond pulses under an inert atmosphere. A formation of three-dimensional structures on monolayer MoS2 with tunable height up to ≈20 nm is demonstrated. In contrast to unmodified monolayer MoS2, these optically modified structures show significantly different optical properties, such as lower photoluminescence intensity and longer fluorescence lifetime. The results suggest a novel way to modify transition metal dichalcogenide materials for mechanic, electronic and photonic applications.Item Direct Synthesis of Semiconducting Single-Walled Carbon Nanotubes Toward High-Performance Electronics(Wiley-VCH Verlag, 2023-07) Liu, Peng; Khan, Abu Taher; Ding, Er Xiong; Zhang, Qiang; Xu, Zhenyu; Bai, Xueyin; Wei, Nan; Tian, Ying; Li, Diao; Jiang, Hua; Lipsanen, Harri; Sun, Zhipei; Kauppinen, Esko I.; Department of Electronics and Nanoengineering; Department of Applied Physics; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTF; Harri Lipsanen Group; NanoMaterials; Aalto University; Department of Electronics and Nanoengineering; Peking University; Dalian Maritime UniversityThe large-scale synthesis of high-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) plays a crucial role in fabricating high-performance and multiapplication-scenario electronics. This work develops a straightforward, continuous, and scalable method to synthesize high-purity and individual s-SWCNTs with small-diameters distribution (≈1 nm). It is believed that the water and carbon dioxide resulting from the decomposition of isopropanol act as oxidizing agents and selectively etch metallic SWCNTs, hence enhancing the production of s-SWCNTs. The performance of individual-SWCNTs field effect transistors confirms the high abundance of s-SWCNTs, presenting a mean mobility of 376 cm2 V−1 s−1 and a high mobility of 2725 cm2 V−1 s−1 with an on-current to off-current (Ion/Ioff) ratio as high as 2.51 × 107. Moreover, thin-film transistors based on the as-synthesized SWCNTs exhibit excellent performance with a mean mobility of 9.3 cm2 V−1 s−1 and Ion/Ioff ratio of 1.3× 105, respectively, verifying the enrichment of s-SWCNTs. This work presents a simple and feasible route for the sustainable synthesis of high-quality s-SWCNTs for electronic devices.Item Dual-gated mono-bilayer graphene junctions(Royal Society of Chemistry, 2021-01-21) Du, Mingde; Du, Luojun; Wei, Nan; Liu, Wei; Bai, Xueyin; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTF; NanoMaterialsA lateral junction with an atomically sharp interface is extensively studied in fundamental research and plays a key role in the development of electronics, photonics and optoelectronics. Here, we demonstrate an electrically tunable lateral junction at atomically sharp interfaces between dual-gated mono- and bilayer graphene. The transport properties of the mono–bilayer graphene interface are systematically investigated with Ids–Vds curves and transfer curves, which are measured with bias voltage Vds applied in opposite directions across the asymmetric mono–bilayer interface. Nearly 30% difference between the output Ids–Vds curves of graphene channels measured at opposite Vds directions is observed. Furthermore, the measured transfer curves confirm that the conductance difference of graphene channels greatly depends on the doping level, which is determined by dual-gating. The Vds direction dependent conductance difference indicates the existence of a gate tunable junction in the mono–bilayer graphene channel, due to different band structures of monolayer graphene with zero bandgap and bilayer graphene with a bandgap opened by dual-gating. Simulation of the Ids–Vds curves based on a new numerical model validates the gate tunable junction at the mono–bilayer graphene interface from another point of view. The dual-gated mono–bilayer graphene junction and new protocol for Ids–Vds curve simulation pave a possible way for functional applications of graphene in next-generation electronics.Item Electrical Control of Interband Resonant Nonlinear Optics in Monolayer MoS2(AMERICAN CHEMICAL SOCIETY, 2020-07-28) Dai, Yunyun; Wang, Yadong; Das, Susobhan; Xue, Hui; Bai, Xueyin; Hulkko, Eero; Zhang, Guangyu; Yang, Xiaoxia; Dai, Qing; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Chinese Academy of Sciences; National Center for Nanoscience and Technology BeijingMonolayer transition-metal dichalcogenides show strong optical nonlinearity with great potential for various emerging applications. Here we demonstrate the gate-tunable interband resonant four-wave mixing and sum-frequency generation in monolayer MoS2. Up to 80% modulation depth in four-wave mixing is achieved when the generated signal is resonant with the A exciton at room temperature, corresponding to an effective third-order optical nonlinearity |χ(3)eff| tuning from (∼12.0 to 5.45) × 10-18 m2/V2. The tunability of the effective second-order optical nonlinearity |χ(2)eff| at 440 nm C-exciton resonance wavelength is also demonstrated from (∼11.6 to 7.40) × 10-9 m/V with sum-frequency generation. Such a large tunability in optical nonlinearities arises from the strong excitonic charging effect in monolayer transition-metal dichalcogenides, which allows for the electrical control of the interband excitonic transitions and thus nonlinear optical responses for future on-chip nonlinear optoelectronics.Item Enhancing Si3N4Waveguide Nonlinearity with Heterogeneous Integration of Few-Layer WS2(ACS Publications, 2021-09-15) Wang, Yuchen; Pelgrin, Vincent; Gyger, Samuel; Uddin, Gius Md; Bai, Xueyin; Lafforgue, Christian; Vivien, Laurent; Jöns, Klaus D.; Cassan, Eric; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; KTH Royal Institute of Technology; Université Paris-Saclay; Paderborn UniversityThe heterogeneous integration of low-dimensional materials with photonic waveguides has spurred wide research interest. Here, we report on the experimental investigation and the numerical modeling of enhanced nonlinear pulse broadening in silicon nitride waveguides with the heterogeneous integration of few-layer WS2. After transferring a few-layer WS2 flake of similar to 14.8 mu m length, the pulse spectral broadening in a dispersion-engineered silicon nitride waveguide has been enhanced by similar to 48.8% in bandwidth. Through numerical modeling, an effective nonlinear coefficient higher than 600 m(-1) W-1 has been retrieved for the heterogeneous waveguide indicating an enhancement factor of larger than 300 with respect to the pristine waveguide at a wavelength of 800 nm. With further advances in two-dimensional material fabrication and integration techniques, on-chip heterostructures will offer another degree of freedom for waveguide engineering, enabling high-performance nonlinear optical devices, such as frequency combs and quantum light sources.Item Giant anisotropic photonics in the 1D van der Waals semiconductor fibrous red phosphorus(Nature Publishing Group, 2021-08-10) Du, Luojun; Zhao, Yanchong; Wu, Linlu; Hu, Xuerong; Yao, Lide; Wang, Yadong; Bai, Xueyin; Dai, Yunyun; Qiao, Jingsi; Uddin, Md Gius; Li, Xiaomei; Lahtinen, Jouko; Bai, Xuedong; Zhang, Guangyu; Ji, Wei; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Surface Science; CAS - Institute of Physics; Renmin University of ChinaA confined electronic system can host a wide variety of fascinating electronic, magnetic, valleytronic and photonic phenomena due to its reduced symmetry and quantum confinement effect. For the recently emerging one-dimensional van der Waals (1D vdW) materials with electrons confined in 1D sub-units, an enormous variety of intriguing physical properties and functionalities can be expected. Here, we demonstrate the coexistence of giant linear/nonlinear optical anisotropy and high emission yield in fibrous red phosphorus (FRP), an exotic 1D vdW semiconductor with quasi-flat bands and a sizeable bandgap in the visible spectral range. The degree of photoluminescence (third-order nonlinear) anisotropy can reach 90% (86%), comparable to the best performance achieved so far. Meanwhile, the photoluminescence (third-harmonic generation) intensity in 1D vdW FRP is strong, with quantum efficiency (third-order susceptibility) four (three) times larger than that in the most well-known 2D vdW materials (e.g., MoS2). The concurrent realization of large linear/nonlinear optical anisotropy and emission intensity in 1D vdW FRP paves the way towards transforming the landscape of technological innovations in photonics and optoelectronics.Item High photoresponsivity and broadband photodetection with a band-engineered WSe 2 /SnSe 2 heterostructure(The Royal Society of Chemistry, 2019-02-21) Xue, Hui; Dai, Yunyun; Kim, Wonjae; Wang, Yadong; Bai, Xueyin; Qi, Mei; Halonen, Kari; Lipsanen, Harri; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Kari Halonen Group; Harri Lipsanen Group; VTT Technical Research Centre of Finlandvan der Waals (vdW) heterostructures formed by stacking different two-dimensional layered materials have been demonstrated as a promising platform for next-generation photonic and optoelectronic devices due to their tailorable band-engineering properties. Here, we report a high photoresponsivity and broadband photodetector based on a WSe 2 /SnSe 2 heterostructure. By properly biasing the heterostructure, its band structure changes from near-broken band alignment to type-III band alignment which enables high photoresponsivity from visible to telecommunication wavelengths. The highest photoresponsivity and detectivity at 532 nm are ∼588 A W -1 and 4.4 × 10 10 Jones and those at 1550 nm are ∼80 A W -1 and 1.4 × 10 10 Jones, which are superior to those of the current state-of-the-art layered transition metal dichalcogenides based photodetectors under similar measurement conditions. Our work not only provides a new method for designing high-performance broadband photodetectors but also enables a deep understanding of the band engineering technology in the vdW heterostructures possible for other applications, such as modulators and lasers.Item Hybrid Photodetection Mechanisms Tuned with Tunneling(2022) Yoon, Hoon Hahn; Fernandez, Henry A.; Nigmatulin, Fedor; Dai, Yunyun; Ahmed, Faisal; Cui, Xiaoqi; Bai, Xueyin; Li, Diao; Du, Mingde; Lipsanen, Harri; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Harri Lipsanen GroupIn this paper, we report two strategies for realizing the hybrid photodetection mechanisms for high-performance broadband photodetectors built with tunable van der Waals (vdW) heterojunction interfaces. All electrically-controlled photoresponse tuned by the atomically-thin tunneling barrier and bandgap contrast across the vdW heterojunction interfaces can be used to adjust the tunneling resistance and suppress the dark current. Adjusting the hybrid photodetection through the switching operation can lead to an optimized optical switching ratio covering from the ultra-violet to the mid-infrared ranges. The representative device structures suitable for each strategy (1) naturally formed oxidation layer (2) energy band alignment, and their characterization exhibit how the hybrid gauge of the photodetection mechanisms can be tuned by quantum tunneling and charge trapping at the vdW heterointerfaces.Item Lattice Dynamics, Phonon Chirality, and Spin–Phonon Coupling in 2D Itinerant Ferromagnet Fe3GeTe2(WILEY-V C H VERLAG GMBH, 2019-11-28) Du, Luojun; Tang, Jian; Zhao, Yanchong; Li, Xiaomei; Yang, Rong; Hu, Xuerong; Bai, Xueyin; Wang, Xiao; Watanabe, Kenji; Taniguchi, Takashi; Shi, Dongxia; Yu, Guoqiang; Bai, Xuedong; Hasan, Tawfique; Zhang, Guangyu; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Chinese Academy of Sciences; National Institute for Materials Science; Songshan Lake Materials Laboratory; University of CambridgeFe3GeTe2 has emerged as one of the most fascinating van der Waals crystals due to its 2D itinerant ferromagnetism, topological nodal lines, and Kondo lattice behavior. However, lattice dynamics, chirality of phonons, and spin-phonon coupling in this material, which set the foundation for these exotic phenomena, have remained unexplored. Here, the first experimental investigation of the phonons and mutual interactions between spin and lattice degrees of freedom in few-layer Fe3GeTe2 is reported. The results elucidate three prominent Raman modes at room temperature: two A(1g)(Gamma) and one E-2g(Gamma) phonons. The doubly degenerate E-2g(Gamma) mode reverses the helicity of incident photons, indicating the pseudoangular momentum and chirality. Through analysis of temperature-dependent phonon energies and lifetimes, which strongly diverge from the anharmonic model below Curie temperature, the spin-phonon coupling in Fe3GeTe2 is determined. Such interaction between lattice oscillations and spin significantly enhances the Raman susceptibility, allowing to observe two additional Raman modes at the cryogenic temperature range. In addition, laser radiation-induced degradation of Fe3GeTe2 in ambient conditions and the corresponding Raman fingerprint is revealed. The results provide the first experimental analysis of phonons in this novel 2D itinerant ferromagnet and their applicability for further fundamental studies and application development.Item Molybdenum Disulfide/Double-Wall Carbon Nanotube Mixed-Dimensional Heterostructures(WILEY-BLACKWELL, 2022-05-04) Bai, Xueyin; Xu, Zhenyu; Zhang, Qiang; Li, Shisheng; Dai, Yunyun; Cui, Xiaoqi; Yoon, Hoon Hahn; Yao, Lide; Jiang, Hua; Du, Mingde; Zhang, Yi; Kauppinen, Esko I.; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTF; NanoMaterials; National Institute for Materials ScienceMixed-dimensional heterostructures which combine materials with different dimensions have emerged to expand the scope and functionality of van der Waals heterostructures. Here, a direct synthesis method of molybdenum disulfide/double-wall carbon nanotube (MoS2/DWCNT) mixed-dimensional heterostructures by sulfurating a molten salt, Na2MoO4, on a substrate covered with a DWCNT film is reported. The synthesized heterostructures are comprehensively characterized and their stacking order is confirmed to be MoS2 under the DWCNTs, although the DWCNT film is transferred on the substrate first. Moreover, field-effect transistors based on the heterostructure are fabricated for photodetection, and an abnormal negative photoresponse is discovered due to the strong carrier transfer in the mixed-dimensional heterostructures under light incidence. The MoS2/DWCNT heterostructure results provide a new approach for the synthesis and applications of mixed-dimensional heterostructures.Item Novel synthesis technologies for two-dimensional transition metal dichalcogenides and their heterostructures(Aalto University, 2022) Bai, Xueyin; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Photonics Group; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Sun, Zhipei, Prof., Aalto University, Department of Electronics and Nanoengineering, FinlandTwo-dimensional (2D) materials, especially 2D transition metal dichalcogenides (TMDs), have been recently expected to play important roles in future applications due to their atomic-thickness nanostructure and various physical properties. Chemical vapour deposition (CVD) is considered to be the most promising synthesis method for two-dimensional materials, due to the best balance between yield and quality of the products. Hence, this thesis focuses on two novel CVD methods for synthesising TMDs and their heterostructures. The first one is molten salt-assisted chemical vapour deposition (Salt 2.0). By applying the Salt 2.0 technique, an abnormal anti-pyramid stacked MoS2/WS2 heterostructure and a MoS2/double-wall carbon nanotube mix-dimensional heterostructure with negative photoresponse are synthesised respectively. These heterostructures can provide new approaches for engineering two-dimensional nanoelectronic devices.Another technique is gas-phase chemical vapour deposition (GCVD). Different from other synthesis methods, the GCVD technique can continuously produce clean and large-mass TMD nanoflakes in aerosols which can be simply collected by a filter for device fabrication and integration at room temperature. A demonstration is achieved for producing MoS2 nanoflakes in the gas phase with an output of up to 24 μg.min-1. The MoS2 nanoflakes have comparable sizes and qualities to the ones from current methods, promising their potential to replace the current MoS2 materials in many applications. In addition, the synthesis without substrate provides a better understanding of the nucleation and growth mechanism in the synthesis of TMDs. The extension of an available novel method and the development of a completely new method provide new approaches for the synthesis of TMDs and other 2D materials.Item Optical Control of High-Harmonic Generation at the Atomic Thickness(AMERICAN CHEMICAL SOCIETY, 2022-11-09) Wang, Yadong; Iyikanat, Fadil; Bai, Xueyin; Hu, Xuerong; Das, Susobhan; Dai, Yunyun; Zhang, Yi; Du, Luojun; Li, Shisheng; Lipsanen, Harri; García De Abajo, F. Javier; Sun, Zhipei; Department of Electronics and Nanoengineering; Zhipei Sun Group; Centre of Excellence in Quantum Technology, QTF; Harri Lipsanen Group; Barcelona Institute of Science and Technology; National Institute for Materials ScienceHigh-harmonic generation (HHG), an extreme nonlinear optical phenomenon beyond the perturbation regime, is of great significance for various potential applications, such as high-energy ultrashort pulse generation with outstanding spatiotemporal coherence. However, efficient active control of HHG is still challenging due to the weak light–matter interaction displayed by currently known materials. Here, we demonstrate optically controlled HHG in monolayer semiconductors via the engineering of interband polarization. We find that HHG can be efficiently controlled in the excitonic spectral region with modulation depths up to 95% and ultrafast response speeds of several picoseconds. Quantitative time-domain theory of the nonlinear optical susceptibilities in monolayer semiconductors further corroborates these experimental observations. Our demonstration not only offers an in-depth understanding of HHG but also provides an effective approach toward active optical devices for strong-field physics and extreme nonlinear optics.Item Probing Electronic States in Monolayer Semiconductors through Static and Transient Third-Harmonic Spectroscopies(WILEY-V C H VERLAG GMBH, 2022-01-20) Wang, Yadong; Iyikanat, Fadil; Rostami, Habib; Bai, Xueyin; Hu, Xuerong; Das, Susobhan; Dai, Yunyun; Du, Luojun; Zhang, Yi; Li, Shisheng; Lipsanen, Harri; García de Abajo, F. Javier; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Harri Lipsanen Group; Barcelona Institute of Science and Technology; KTH Royal Institute of Technology; National Institute for Materials ScienceElectronic states and their dynamics are of critical importance for electronic and optoelectronic applications. Here, various relevant electronic states in monolayer MoS2, such as multiple excitonic Rydberg states and free-particle energy bands are probed with a high relative contrast of up to >= 200 via broadband (from approximate to 1.79 to 3.10 eV) static third-harmonic spectroscopy (THS), which is further supported by theoretical calculations. Moreover, transient THS is introduced to demonstrate that third-harmonic generation can be all-optically modulated with a modulation depth exceeding approximate to 94% at approximate to 2.18 eV, providing direct evidence of dominant carrier relaxation processes associated with carrier-exciton and carrier-phonon interactions. The results indicate that static and transient THS are not only promising techniques for the characterization of monolayer semiconductors and their heterostructures, but also a potential platform for disruptive photonic and optoelectronic applications, including all-optical modulation and imaging.Item Single-step chemical vapour deposition of anti-pyramid MoS2/WS2vertical heterostructures(ROYAL SOC CHEMISTRY, 2021-02-28) Bai, Xueyin; Li, Shisheng; Das, Susobhan; Du, Luojun; Dai, Yunyun; Yao, Lide; Raju, Ramesh; Du, Mingde; Lipsanen, Harri; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Ilkka Tittonen Group; Harri Lipsanen Group; National Institute for Materials ScienceVan der Waals heterostructures are the fundamental building blocks of electronic and optoelectronic devices. Here we report that, through a single-step chemical vapour deposition (CVD) process, high-quality vertical bilayer MoS2/WS2 heterostructures with a grain size up to ∼60 μm can be synthesized from molten salt precursors, Na2MoO4 and Na2WO4. Instead of normal pyramid vertical heterostructures grown by CVD, this method synthesizes an anti-pyramid MoS2/WS2 structure, which is characterized by Raman, photoluminescence and second harmonic generation microscopy. Our facile CVD strategy for synthesizing anti-pyramid structures unveils a new synthesis route for the products of two-dimensional heterostructures and their devices for application.Item Tunable Quantum Tunneling through a Graphene/Bi2Se3 Heterointerface for the Hybrid Photodetection Mechanism(AMERICAN CHEMICAL SOCIETY, 2021-12-15) Yoon, Hoon Hahn; Ahmed, Faisal; Dai, Yunyun; Fernandez Pizarro, Henry; Cui, Xiaoqi; Bai, Xueyin; Li, Diao; Du, Mingde; Lipsanen, Harri; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Harri Lipsanen GroupGraphene-based van der Waals heterostructures are promising building blocks for broadband photodetection because of the gapless nature of graphene. However, their performance is mostly limited by the inevitable trade-off between low dark current and photocurrent generation. Here, we demonstrate a hybrid photodetection mode based on the photogating effect coupled with the photovoltaic effect via tunable quantum tunneling through the unique graphene/Bi2Se3 heterointerface. The tunneling junction formed between the semimetallic graphene and the topologically insulating Bi2Se3 exhibits asymmetric rectifying and hysteretic current-voltage characteristics, which significantly suppresses the dark current and enhances the photocurrent. The photocurrent-to-dark current ratio increases by about a factor of 10 with the electrical tuning of tunneling resistance for efficient light detection covering the major photonic spectral band from the visible to the mid-infrared ranges. Our findings provide a novel concept of using tunable quantum tunneling for highly sensitive broadband photodetection in mixed-dimensional van der Waals heterostructures.
