Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllab...Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllable doping of TMDs remains a challenging issue due to the natural doping of these materials.Here,we demonstrate the controllable growth of indium-doped p-type WS_(2) monolayers with various doping concentrations via chemical vapor deposition(CVD)of a host tungsten(W)source and indium(In)dopant.Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS_(2) lattice.Intriguingly,the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration,which first increases remarkably with an enhancement factor up to~35 and then decreases gradually when further increasing the doping concentration.Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples.The assignment was further verified by the electric behavior of the fabricated In-doped WS_(2) field effect transistors,which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration.The successful growth of p-type monolayer WS_(2) and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.展开更多
The realization of light-triggered devices where light is used as external stimulus to control the device performances is a long-standing goal in modern opto-electrical interconnection circuits.In this work,it reveals...The realization of light-triggered devices where light is used as external stimulus to control the device performances is a long-standing goal in modern opto-electrical interconnection circuits.In this work,it reveals that light illumination can induce the formation of p-n junctions along two-dimensional conduction channels.The results indicate that the dominant charge carrier type and density in black phosphorus(BP)conduction channel can be effectively modulated by the underlying cadmium sulfide(CdS)photogate layer under light illumination.This enables flexible switching of the working state between BP resistor and BP p-n diode in the designed semi-photo-gate transistor(SPGT)devices when switching the light on and off(ultra-low threshold light power).Simultaneously,the achieved BP p-n junctions also exhibit ultra-high photoresponsivity and evident photovoltaic properties.That is to say,light can be employed as external stimulus to define the BP p-n junctions,and in turn the p-n junctions will further convert the light into electrical power,showing all-in-one opto-electrical interconnection properties.Moreover,the SPGT device architecture is also applicable for construction of other ambipolar semiconductor-based(WSe2-and MoTe2-based)p-n diodes.Such universal all-in-one light-triggered lateral homogeneous pn junctions with ultra-low energy consumption should open a new pathway toward novel optoelectronic devices and deliver various new applications.展开更多
Layered semiconductor heterostructures are essential elements in modern electronic and optoelectronic devices.Dynamically engineering the composition of these heterostructures may enable the flexible design of the pro...Layered semiconductor heterostructures are essential elements in modern electronic and optoelectronic devices.Dynamically engineering the composition of these heterostructures may enable the flexible design of the properties of heterostructure-based electronics and optoelectronics as well as their optimization.Here,we report for the first time a two-step chemical vapor deposition approach for a series of WS2(1−x)Se2x/SnS2 vertical heterostructures with high-quality and large areas.The steady-state photoluminescence results exhibit an obvious composition-related quenching ratio,revealing a strong coherence between the band offset and the charge transfer efficiency at the junction interface.Based on the achieved heterostructures,dual-channel backgate field-effect transistors were successfully designed and exhibited typical composition-dependent transport behaviors,and pure n-type unipolar transistors to ambipolar transistors were realized in such systems.The direct vapor growth of these novel vertical WS2(1−x)Se2x/SnS2 heterostructures could offer an interesting system for probing new physical properties and provide a series of layered heterostructures for high-quality devices.展开更多
Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surface...Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surfaces of 2D materials enable the direct integration of different materials with various properties through van der Waals(vdW)forces into vdW heterostructures,providing new opportunities for constructing new type devices with superior performances.In this study,we report the vertical assembly of n-type CdS and p-type BP into p-n junctions.The electrically tunable heterojunction device shows a high current rectifying ratio up to8×103at a low bias voltage range of±1 V and an ideality factor of 1.5.More interestingly,the CdS/BP vdW heterojunction exhibits an ultra-high photoresponsivity up to 9.2×105A W-1and an ultra-high specific detectivity of 3.2×1013Jones with a low bias voltage of 1.0 V,which is among the highest in the reported results of 2D heterostructures.While operated at a self-powered mode,the device also exhibits excellent photodetection performances with a high photoresponsivity of0.27 A W-1and a high external quantum efficiency of 76%.Time-resolved photoresponse characterizations indicate that the device possesses a fast response time of about 10 ms.The developed CdS/BP vdW heterojunctions will find potential applications in the next-generation nanoscale electronics and optoelectronics applications.展开更多
The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of tra...The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of traditional semiconductors. However, the realization of high performance 2D semiconductorbased field-effect transistors(FETs) has been a longstanding challenge in 2D electronics, which is mainly ascribing to the presence of significant Schottky barrier(SB) at metal-semiconductor interfaces. Here, an additional contact gate is induced in 2D ambipolar FET to realize near ideal reconfigurable FET(RFET)devices without restrictions of SB. Benefitting from the consistently high doping of contact region, the effective SB height can be maintained at ultra-small value during all operation conditions, resulting in the near ideal subthreshold swing(SS) values(132 mV/decade for MoTe2 RFET and 67 mV/decade for WSe2 RFET) and the relatively high mobility(28.6 cm2/(Vs) for MoTe2 RFET and 89.8 cm2/(V s) for WSe2 RFET). Moreover, the flexible control on the doping polarity of contact region enables the remodeling and switching of the achieved unipolar FETs between p-type mode and n-type mode. Based on such reconfigurable behaviors, high gain complementary MoTe2 inverters are further realized. The findings in this work push forward the development of high-performance 2D semiconductor integrated devices and circuits.展开更多
The growth of data and Internet of Things challenges traditional hardware,which encounters efficiency and power issues owing to separate functional units for sensors,memory,and computation.In this study,we designed an...The growth of data and Internet of Things challenges traditional hardware,which encounters efficiency and power issues owing to separate functional units for sensors,memory,and computation.In this study,we designed an a-phase indium selenide(a-In_(2)Se_(3))transistor,which is a two-dimensional ferroelectric semiconductor as the channel material,to create artificial optic-neural and electro-neural synapses,enabling cutting-edge processing-in-sensor(PIS)and computing-in-memory(CIM)functionalities.As an optic-neural synapse for low-level sensory processing,the a-In_(2)Se_(3)transistor exhibits a high photoresponsivity(2855 A/W)and detectivity(2.91×10^(14)Jones),facilitating efficient feature extraction.For high-level processing tasks as an electro-neural synapse,it offers a fast program/erase speed of 40 ns/50μs and ultralow energy consumption of 0.37 aJ/spike.An AI vision system using a-In_(2)Se_(3)transistors has been demonstrated.It achieved an impressive recognition accuracy of 92.63%within 12 epochs owing to the synergistic combination of the PIS and CIM functionalities.This study demonstrates the potential of the a-In_(2)Se_(3)transistor in future vision hardware,enhancing processing,power efficiency,and AI applications.展开更多
Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promis...Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promise for next-generation information circuits,still suffer from poor contact quality at the metal–semiconductor junction interface,which severely hinders their further applications.Here,a novel contact strategy is proposed,where Bi_(2)Te_(3)nanosheets with high conductivity were in-situ epitaxially grown on MoS_(2)as van der Waals contacts,which can effectively avoid the damage to MoS_(2)caused during the device manufacturing process,leading to a high-performance MoS_(2)FET.Moreover,the small work function difference between Bi_(2)Te_(3)and MoS_(2)(Bi_(2)Te_(3):4.31 eV,MoS_(2):4.37 eV,measured by Kelvin probe force microscopy(KPFM)),enables small band bending and Ohmic contact at the junction interface.Electrical characterizations indicate that the MoS_(2)FET device with Bi_(2)Te_(3)contacts possesses a high current on/off ratio(5×107),large effective carrier mobility(90 cm^(2)/(V·s)),and low flat-band SBH(60 meV),which is favorable as compared with MoS_(2)FET with traditional Cr/Au electrodes contacts,and superior to the vast majority of the reported chemical vapor deposition(CVD)MoS_(2)-based FET device.The demonstration of epitaxial van der Waals Bi_(2)Te_(3)contacts will facilitate the application of 2D MoS_(2)nanosheet in next-generation low-power consumption electronics and optoelectronics.展开更多
Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previous...Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previously been proven to be a feasible way to tune the band structure and related properties of 3D materials;however,this approach still remains to be explored in 2D materials.Here,we systematically demonstrate the growth of vanadium-doped molybdenum disulfde(V-doped MoS_(2))monolayers via an alkali metal-assisted chemical vapor deposition method.Scanning transmission electron microscopy demonstrated that V atoms substituted the Mo atoms and became uniformly distributed in the MoS_(2)monolayers.This was also confrmed by Raman and X-ray photoelectron spectroscopy.Power-dependent photoluminescence spectra clearly revealed the enhanced B-exciton emission characteristics in the V-doped MoS_(2)monolayers(with low doping concentration).Most importantly,through temperature-dependent study,we observed efcient valley scattering of the B-exciton,greatly enhancing its emission intensity.Carrier transport experiments indicated that typical p-type conduction gradually arisen and was enhanced with increasing V composition in the V-doped MoS_(2),where a clear n-type behavior transited frst to ambipolar and then to lightly p-type charge carrier transport.In addition,visible to infrared wide-band photodetectors based on V-doped MoS_(2)monolayers(with low doping concentration)were demonstrated.The V-doped MoS_(2)monolayers with distinct B-exciton emission,enhanced p-type conduction and broad spectral response can provide new platforms for probing new physics and ofer novel materials for optoelectronic applications.展开更多
Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exh...Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exhibit picosecond photoresponse speed.However,2D materials naturally have low absorption,and when increasing thickness to gain higher responsivity,the response time usually slows to nanoseconds,limiting their photodetection performance.Here,by taking time-resolved photocurrent measurements,we demonstrated that graphene/MoTe_(2) van der Waals heterojunctions realize a fast 10 ps photoresponse time owing to the reduced average photocurrent drift time in the heterojunction,which is fundamentally distinct from traditional Dirac semimetal photodetectors such as graphene or Cd_(3)As_(2) and implies a photodetection bandwidth as wide as 100 GHz.Furthermore,we found that an additional charge carrier transport channel provided by graphene can ef-fectively decrease the photocurrent recombination loss to the entire device,preserving a high responsivity in the near-infrared region.Our study provides a deeper understanding of the ultrafast electrical response in van der Waals heterojunctions and offers a promising approach for the realization of photodetectors with both high responsivity and ultrafast electrical response.展开更多
基金financially supported by the National Natural Science Foundation of China (51525202, 61635001, 52072117 and 21703059)the Key Program of the Hunan Provincial Science and Technology Department (2019XK2001)the International Science and Technology Innovation Cooperation Base of Hunan Province (2018WK4004)
文摘Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllable doping of TMDs remains a challenging issue due to the natural doping of these materials.Here,we demonstrate the controllable growth of indium-doped p-type WS_(2) monolayers with various doping concentrations via chemical vapor deposition(CVD)of a host tungsten(W)source and indium(In)dopant.Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS_(2) lattice.Intriguingly,the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration,which first increases remarkably with an enhancement factor up to~35 and then decreases gradually when further increasing the doping concentration.Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples.The assignment was further verified by the electric behavior of the fabricated In-doped WS_(2) field effect transistors,which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration.The successful growth of p-type monolayer WS_(2) and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.
基金supported by the National Natural Science Foundation of China (51902098, 51972105, 51525202, and 61574054)the Hunan Provincial Natural Science Foundation (2018RS3051).
文摘The realization of light-triggered devices where light is used as external stimulus to control the device performances is a long-standing goal in modern opto-electrical interconnection circuits.In this work,it reveals that light illumination can induce the formation of p-n junctions along two-dimensional conduction channels.The results indicate that the dominant charge carrier type and density in black phosphorus(BP)conduction channel can be effectively modulated by the underlying cadmium sulfide(CdS)photogate layer under light illumination.This enables flexible switching of the working state between BP resistor and BP p-n diode in the designed semi-photo-gate transistor(SPGT)devices when switching the light on and off(ultra-low threshold light power).Simultaneously,the achieved BP p-n junctions also exhibit ultra-high photoresponsivity and evident photovoltaic properties.That is to say,light can be employed as external stimulus to define the BP p-n junctions,and in turn the p-n junctions will further convert the light into electrical power,showing all-in-one opto-electrical interconnection properties.Moreover,the SPGT device architecture is also applicable for construction of other ambipolar semiconductor-based(WSe2-and MoTe2-based)p-n diodes.Such universal all-in-one light-triggered lateral homogeneous pn junctions with ultra-low energy consumption should open a new pathway toward novel optoelectronic devices and deliver various new applications.
基金National Natural Science Foundation of China,Grant/Award Numbers:51525202,51902098,51772084,61574054,51972105the Hunan Provincial Natural Science Foundation of China(No.2018RS3051).
文摘Layered semiconductor heterostructures are essential elements in modern electronic and optoelectronic devices.Dynamically engineering the composition of these heterostructures may enable the flexible design of the properties of heterostructure-based electronics and optoelectronics as well as their optimization.Here,we report for the first time a two-step chemical vapor deposition approach for a series of WS2(1−x)Se2x/SnS2 vertical heterostructures with high-quality and large areas.The steady-state photoluminescence results exhibit an obvious composition-related quenching ratio,revealing a strong coherence between the band offset and the charge transfer efficiency at the junction interface.Based on the achieved heterostructures,dual-channel backgate field-effect transistors were successfully designed and exhibited typical composition-dependent transport behaviors,and pure n-type unipolar transistors to ambipolar transistors were realized in such systems.The direct vapor growth of these novel vertical WS2(1−x)Se2x/SnS2 heterostructures could offer an interesting system for probing new physical properties and provide a series of layered heterostructures for high-quality devices.
基金supported by the National Natural Science Foundation of China(U19A2090,51902098,51972105,51525202 and 61574054)Hunan Provincial Natural Science Foundation of China(2018RS3051)。
文摘Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surfaces of 2D materials enable the direct integration of different materials with various properties through van der Waals(vdW)forces into vdW heterostructures,providing new opportunities for constructing new type devices with superior performances.In this study,we report the vertical assembly of n-type CdS and p-type BP into p-n junctions.The electrically tunable heterojunction device shows a high current rectifying ratio up to8×103at a low bias voltage range of±1 V and an ideality factor of 1.5.More interestingly,the CdS/BP vdW heterojunction exhibits an ultra-high photoresponsivity up to 9.2×105A W-1and an ultra-high specific detectivity of 3.2×1013Jones with a low bias voltage of 1.0 V,which is among the highest in the reported results of 2D heterostructures.While operated at a self-powered mode,the device also exhibits excellent photodetection performances with a high photoresponsivity of0.27 A W-1and a high external quantum efficiency of 76%.Time-resolved photoresponse characterizations indicate that the device possesses a fast response time of about 10 ms.The developed CdS/BP vdW heterojunctions will find potential applications in the next-generation nanoscale electronics and optoelectronics applications.
基金supported by the National Natural Science Foundation of China (U19A2090, 51902098, 51972105, 51525202, and 61574054)the Hunan Provincial Natural Science Foundation (2018RS3051)。
文摘The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of traditional semiconductors. However, the realization of high performance 2D semiconductorbased field-effect transistors(FETs) has been a longstanding challenge in 2D electronics, which is mainly ascribing to the presence of significant Schottky barrier(SB) at metal-semiconductor interfaces. Here, an additional contact gate is induced in 2D ambipolar FET to realize near ideal reconfigurable FET(RFET)devices without restrictions of SB. Benefitting from the consistently high doping of contact region, the effective SB height can be maintained at ultra-small value during all operation conditions, resulting in the near ideal subthreshold swing(SS) values(132 mV/decade for MoTe2 RFET and 67 mV/decade for WSe2 RFET) and the relatively high mobility(28.6 cm2/(Vs) for MoTe2 RFET and 89.8 cm2/(V s) for WSe2 RFET). Moreover, the flexible control on the doping polarity of contact region enables the remodeling and switching of the achieved unipolar FETs between p-type mode and n-type mode. Based on such reconfigurable behaviors, high gain complementary MoTe2 inverters are further realized. The findings in this work push forward the development of high-performance 2D semiconductor integrated devices and circuits.
基金supported by the National Natural Science Foundation of China(62104066,52221001,62090035,U19A2090,U22A20138,52372146,and 62101181)the National Key R&D Program of China(2022YFA1402501,2022YFA1204300)+6 种基金the Natural Science Foundation of Hunan Province(2021JJ20016)the Science and Technology Innovation Program of Hunan Province(2021RC3061)the Key Program of Science and Technology Department of Hunan Province(2019XK2001,2020XK2001)the Open Project Program of Wuhan National Laboratory for Optoelectronics(2020WNLOKF016)the Open Project Program of Key Laboratory of Nanodevices and Applications,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences(22ZS01)the Project funded by China Postdoctoral Science Foundation(2023TQ0110)the Innovation Project of Optics Valley Laboratory(OVL2023ZD002).
文摘The growth of data and Internet of Things challenges traditional hardware,which encounters efficiency and power issues owing to separate functional units for sensors,memory,and computation.In this study,we designed an a-phase indium selenide(a-In_(2)Se_(3))transistor,which is a two-dimensional ferroelectric semiconductor as the channel material,to create artificial optic-neural and electro-neural synapses,enabling cutting-edge processing-in-sensor(PIS)and computing-in-memory(CIM)functionalities.As an optic-neural synapse for low-level sensory processing,the a-In_(2)Se_(3)transistor exhibits a high photoresponsivity(2855 A/W)and detectivity(2.91×10^(14)Jones),facilitating efficient feature extraction.For high-level processing tasks as an electro-neural synapse,it offers a fast program/erase speed of 40 ns/50μs and ultralow energy consumption of 0.37 aJ/spike.An AI vision system using a-In_(2)Se_(3)transistors has been demonstrated.It achieved an impressive recognition accuracy of 92.63%within 12 epochs owing to the synergistic combination of the PIS and CIM functionalities.This study demonstrates the potential of the a-In_(2)Se_(3)transistor in future vision hardware,enhancing processing,power efficiency,and AI applications.
基金The authors are grateful to the National Key R&D Program of China(No.2022YFA1402501)the National Natural Science Foundation of China(Nos.51902098,62090035,U22A2013,and U19A2090)+3 种基金the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Program of Hunan Province(Nos.2021RC3061,2020RC2028,and 2021RC2042)the Natural Science Foundation of Hunan Province(No.2021JJ20016)the Project funded by China Postdoctoral Science Foundation(Nos.2020M680112 and 2021M690953).
文摘Small contact resistance and low Schottky barrier height(SBH)are the keys to energy-efficient electronics and optoelectronics.Two-dimensional(2D)semiconductors-based field effect transistors(FETs),holding great promise for next-generation information circuits,still suffer from poor contact quality at the metal–semiconductor junction interface,which severely hinders their further applications.Here,a novel contact strategy is proposed,where Bi_(2)Te_(3)nanosheets with high conductivity were in-situ epitaxially grown on MoS_(2)as van der Waals contacts,which can effectively avoid the damage to MoS_(2)caused during the device manufacturing process,leading to a high-performance MoS_(2)FET.Moreover,the small work function difference between Bi_(2)Te_(3)and MoS_(2)(Bi_(2)Te_(3):4.31 eV,MoS_(2):4.37 eV,measured by Kelvin probe force microscopy(KPFM)),enables small band bending and Ohmic contact at the junction interface.Electrical characterizations indicate that the MoS_(2)FET device with Bi_(2)Te_(3)contacts possesses a high current on/off ratio(5×107),large effective carrier mobility(90 cm^(2)/(V·s)),and low flat-band SBH(60 meV),which is favorable as compared with MoS_(2)FET with traditional Cr/Au electrodes contacts,and superior to the vast majority of the reported chemical vapor deposition(CVD)MoS_(2)-based FET device.The demonstration of epitaxial van der Waals Bi_(2)Te_(3)contacts will facilitate the application of 2D MoS_(2)nanosheet in next-generation low-power consumption electronics and optoelectronics.
基金supported by the National Key R&D Program of China(No.2022YFA1204300)the National Natural Science Foundation of China(Grant Nos.62104066,52372146,U22A20138,52221001 and 62090035)+2 种基金the Open Project Program of Wuhan National Laboratory for Optoelectronics(No.2020WNLOKF016)the Science and Technology Innovation Program of Hunan Province(Nos.2021RC3061 and 2020RC2028)the National Postdoctoral Program for Innovative Talents(No.BX2021094).
文摘Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previously been proven to be a feasible way to tune the band structure and related properties of 3D materials;however,this approach still remains to be explored in 2D materials.Here,we systematically demonstrate the growth of vanadium-doped molybdenum disulfde(V-doped MoS_(2))monolayers via an alkali metal-assisted chemical vapor deposition method.Scanning transmission electron microscopy demonstrated that V atoms substituted the Mo atoms and became uniformly distributed in the MoS_(2)monolayers.This was also confrmed by Raman and X-ray photoelectron spectroscopy.Power-dependent photoluminescence spectra clearly revealed the enhanced B-exciton emission characteristics in the V-doped MoS_(2)monolayers(with low doping concentration).Most importantly,through temperature-dependent study,we observed efcient valley scattering of the B-exciton,greatly enhancing its emission intensity.Carrier transport experiments indicated that typical p-type conduction gradually arisen and was enhanced with increasing V composition in the V-doped MoS_(2),where a clear n-type behavior transited frst to ambipolar and then to lightly p-type charge carrier transport.In addition,visible to infrared wide-band photodetectors based on V-doped MoS_(2)monolayers(with low doping concentration)were demonstrated.The V-doped MoS_(2)monolayers with distinct B-exciton emission,enhanced p-type conduction and broad spectral response can provide new platforms for probing new physics and ofer novel materials for optoelectronic applications.
基金This work was supported by the National Natural Science Foundation of China(Grants No.52022029,91850116,51772084,and U19A2090)the Sino-German Center for Research Promotion(Grant No.GZ1390)the Hunan Provincial Natural Science Foundation of China(Grants No.2018RS3051 and 2019XK2001)。
文摘Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exhibit picosecond photoresponse speed.However,2D materials naturally have low absorption,and when increasing thickness to gain higher responsivity,the response time usually slows to nanoseconds,limiting their photodetection performance.Here,by taking time-resolved photocurrent measurements,we demonstrated that graphene/MoTe_(2) van der Waals heterojunctions realize a fast 10 ps photoresponse time owing to the reduced average photocurrent drift time in the heterojunction,which is fundamentally distinct from traditional Dirac semimetal photodetectors such as graphene or Cd_(3)As_(2) and implies a photodetection bandwidth as wide as 100 GHz.Furthermore,we found that an additional charge carrier transport channel provided by graphene can ef-fectively decrease the photocurrent recombination loss to the entire device,preserving a high responsivity in the near-infrared region.Our study provides a deeper understanding of the ultrafast electrical response in van der Waals heterojunctions and offers a promising approach for the realization of photodetectors with both high responsivity and ultrafast electrical response.
