Interfacial disorders in semiconductor quantum wells(QWs)determine material properties and device performance and have attracted great research efforts using different experimental methods.However,so far,there has bee...Interfacial disorders in semiconductor quantum wells(QWs)determine material properties and device performance and have attracted great research efforts using different experimental methods.However,so far,there has been no way to quantify the lateral length distribution of the interfacial disorders in QWs.Since photoluminescence(PL)is sensitive to exciton localization,the evolutions of PL energy and linewidth under external perpendicular magnetic fields have served as effective measurement methods for QW analysis;however,the evolution of PL intensity has not played a matching role.In this paper,we develop a theoretical model correlating the PL intensity with the interfacial disorders of type-I QWs under an external perpendicular magnetic field.We verify the model's rationality and functionality using In Ga(N)As/Ga As single QWs.In addition,we derive the Urbach energy and determine the lateral length distribution of interfacial disorders.The results show that the magnetic field-dependent PL intensity,as described by our model,serves as a valid probe for quantifying the interface flatness.The model also reveals that the mechanism of magnetic-field-induced intensity enhancement is a joint effect of interfacial disorder-induced exciton localization and the transfer of excitons from dark to bright states.These insights may benefit performance improvements of type-I QW materials and devices.展开更多
This paper presents a review of recent advances in quantum well and quantum cascade infrared photodetectors developed in Shanghai Institute of Technical Physics, Chinese Academy of Sciences(SITP/CAS). Firstly, the tem...This paper presents a review of recent advances in quantum well and quantum cascade infrared photodetectors developed in Shanghai Institute of Technical Physics, Chinese Academy of Sciences(SITP/CAS). Firstly, the temperature-and bias-dependent photocurrent spectra of very long wavelength(VLW) GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations in detail. We confirm that the first excited state, which belongs to the quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. Aided by band structure calculations, we propose a model of the double excited states that determine the working mechanism in VLW QWIPs. Secondly, we present an overview of a VLW QWIP focal plane array(FPA)with 320×256 pixels based on the bound to quasi-bound(BTQB) design. The technology of the manufacturing FPA based on the QWIP structures has been demonstrated. At the operating temperature of 45 K, the detectivity of QWIP FPA is larger than 1.4×10^(10) cm·Hz^(1/2)/W with a cutoff wavelength larger than 16 μm. Finally, to meet the needs of space applications, we proposed a new long wavelength quantum cascade detector with a broadband detection ranging from 7.6 μm to 10.4 μm. With a pair of identical coupled quantum wells separated by a thin barrier, acting as absorption regions, the relative linewidth(?E/E) of response can be dramatically broadened to 30.7%. It is shown that the spectral shape and linewidth can be tuned by the thickness of the thin barrier, while it is insensitive to the working temperature. The device can work above liquid nitrogen temperature with a peak responsivity of 63 mA/W and Johnson noise limited detectivity of 5.1×10~9 cm·Hz^(1/2)/W.展开更多
The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of th...The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.展开更多
Two-dimensional transition metal dichalcogenides(TMDs) provide fertile ground to study the interplay between dimensionality and electronic properties because they exhibit a variety of electronic phases, such as semico...Two-dimensional transition metal dichalcogenides(TMDs) provide fertile ground to study the interplay between dimensionality and electronic properties because they exhibit a variety of electronic phases, such as semiconducting, superconducting, charge density waves(CDW) states, and other unconventional physical properties. Compared with other classical TMDs, such as Mott insulator 1T–TaS_2 or superconducting 2H–NbSe_2, bulk 2H–TaSe_2 has been a canonical system and a touchstone for modeling the CDW measurement with a less complex phase diagram. In contrast to ordinary semiconductors that have only single-particle excitations, CDW can have collective excitation and carry current in a collective fashion. However, manipulating this collective condensation of these intriguing systems for device applications has not been explored. Here, the CDW-induced collective driven of non-equilibrium carriers in a field-effect transistor has been demonstrated for the sensitive photodetection at the highly-pursuit terahertz band. We show that the 2H–TaSe_2-based photodetector exhibits a fast photoresponse, as short as 14 μs, and a responsivity of over 27 V/W at room temperature. The fast response time, relative high responsivity and ease of fabrication of these devices yields a new prospect of exploring CDW condensate in TMDs with the aim of overcoming the existing limitations for a variety of practical applications at THz spectral range.展开更多
The staggered InGaN quantum well (QW) structure and the conventional InGaN QW structure for the emission at a particu-lar wavelength of 400 nm are designed and theoretically investigated,including the distribution of ...The staggered InGaN quantum well (QW) structure and the conventional InGaN QW structure for the emission at a particu-lar wavelength of 400 nm are designed and theoretically investigated,including the distribution of the carriers’ concentration,the radiative recombination rate,the Shockley-Read-Hall (SRH) recombination rate as well as the output performance and the internal quantum efficiency. The theoretical result indicates that the staggered QW structure offers significant improve-ment of carriers’ concentration in the QW,especially the hole concentration. The output power and the internal quantum efficiency also show 32.6 % and 32.5 % enhancement,respectively,in comparison with that of the conventional InGaN QW structure. The reduction of the electron overflow can be the main factor for the improvement of the optical perfor-mance for novel staggered InGaN QW structure.展开更多
As the lastly unexplored electromagnetic wave,terahertz(THz)radiation has been exploited in a plenty of contexts such as fundamental research,military and civil fields.Most recently,representative two-dimensional(2D)t...As the lastly unexplored electromagnetic wave,terahertz(THz)radiation has been exploited in a plenty of contexts such as fundamental research,military and civil fields.Most recently,representative two-dimensional(2D)topological semimetal,platinum ditelluride(PtTe_(2))has attracted considerable research interest in THz detection due to its unique physical properties.However,to achieve practical applications,the low-cost,large-scale,controllable synthesis and efficient patterning of 2D materials are key requirements,which remain a challenge for PtTe_(2)and its photodetectors(PDs).Herein,a facile approach is developed to obtain waferscale(2-inches)patterned PtTe_(2)arrays using one-step tellurium-vapor transformation method and micro-Nano technology.PtTe_(2)PD arrays are fabricated with the as-grown PtTe_(2)arrays evenly distributed on a 2-inch wafer,exhibiting high conductivity(~2.7×105 S m^(-1))and good electrical consistency.Driven by the Dirac fermions,PtTe_(2)PDs achieve a broadband(0.02-0.3 THz)response with a fast response speed(~4.7μs),a high sensitivity(~47 pW Hz^(-1/2))and high-resolution transmission THz-imaging capability,which displays the potential of large-area THz array imaging.These results are one step towards the practical applications of integrated PD arrays based on 2D materials.展开更多
Broadband response is pursued in both infrared(IR)and terahertz(THz)detection technologies,which find their applications in both terrestrial and astronomical realms.Herein,we report an ultrabroadband and multiband IR/...Broadband response is pursued in both infrared(IR)and terahertz(THz)detection technologies,which find their applications in both terrestrial and astronomical realms.Herein,we report an ultrabroadband and multiband IR/THz detector based on blocked-impurity-band detecting principle.The detectors are prepared by implanting phosphorus into germanium(Ge:P),where photoresponses with a P impurity band,a self-interstitial defect band,and a vacancy-P(V-P)pair defect band are realized simultaneously.The response spectra of the detectors show ultrabroad and dual response bands in a range of 3-28μm(IR band)and 40-165μm(THz band),respectively.Additionally,a tiny mid-IR(MIR)band within 3-4.2μm is embedded in the IR band.The THz band arises from the P impurity band,whereas the IR and the MIR bands are ascribed to the two defect bands.At150 m V and 4.5 K,the peak detectivities of the three bands are obtained as 2.9×10^(12) Jones(at 3.9μm),6.8×10^(12) Jones(at 16.3μm),and 9.9×10^(12) Jones(at 116.5μm),respectively.The impressive coverage andsensitivity of the detectors are promising for applications in IR and THz detection technologies.展开更多
Platinum telluride(PtTe_(2)),a member of metallic transition metal dichalcogenides,provides a new platform for investigating various properties such as type-II Dirac fermions,topological superconductivity,and wide-ban...Platinum telluride(PtTe_(2)),a member of metallic transition metal dichalcogenides,provides a new platform for investigating various properties such as type-II Dirac fermions,topological superconductivity,and wide-band photodetection.However,the study of PtTe_(2)is largely limited to exfoliated flakes,and its direct synthesis remains challenging.Herein,we report the controllable synthesis of highly crystalline 2D PtTe_(2)crystals with tunable morphology and thickness via chemical vapor deposition(CVD)growth on Au substrate.By adjusting Te amount and substrate temperature,anisotropic and isotropic growth modes of PtTe_(2)were realized on the solid and molten Au substrates,respectively.The domain size of PtTe_(2)crystal was achieved up to 30μm,and its thickness can be tuned from 5.6 to 50 nm via controlling the growth time.Furthermore,a metal–PtTe_(2)–metal structural device was fabricated to validate the wide-band terahertz(THz)photodetection from 0.04 to 0.3 THz at room temperature.Owing to the high crystallinity of PtTe_(2)crystal,the photodetector acquires high responsivity(30–250 mA W-1 from 0.12 to 0.3 THz),fast response rate(rise time:7μs,decay time:8μs),and high-quality imaging ability.Our work demonstrates the feasibility for realistic exploitation of high-performing photodetection system at THz band based on the CVDgrown 2D Dirac semimetal materials.展开更多
Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small ...Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal.Here,we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe_(2)and its van der Waals heterostructures.Explicitly,we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime(λ/10^(4)),featuring colossal photoresponse by in-plane symmetry breaking.The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe_(2)Dirac semimetal,yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding∼0.2 A/W and noise-equivalent power(NEP)less than~38 pW/Hz^(0.5),as well as superb ambient stability.Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging,remote sensing or security applications.展开更多
In this study,we report the growth of free-standing InAs nanosheets using Au catalysts in molecular beam epitaxy.Detailed structural characterizations suggest that wurtzite structured InAs nanosheets,with features of ...In this study,we report the growth of free-standing InAs nanosheets using Au catalysts in molecular beam epitaxy.Detailed structural characterizations suggest that wurtzite structured InAs nanosheets,with features of extensive{1120}surfaces,grown along the<1102>direction and adopted{0001}nanosheet/catalyst interfaces,are initiated from wurtzite structured[0001]nanowires as the inclined epitaxial growth due to relatively higher In concentrations in Au catalysts,and grown from these inclined nanostructures through catalyst-induced axial growth and their enhanced lateral growth under the high growth temperature.Based on the facts that the nanosheets contain large low energy{1120}surfaces and{0001}nanosheet/catalyst interfaces,the growth of our nanosheets is a thermodynamically driven process.This study provides new insights into fabricating free-standing Ⅲ-Ⅴ nanosheets for their applications in future nanoscale devices.展开更多
Semiconductor nanowires(NWs)could simultaneously provide gain medium and optical cavity for performing nanoscale lasers with easy integration,ultracompact footprint,and low energy consumption.Here,we report Ⅲ-Ⅴsemic...Semiconductor nanowires(NWs)could simultaneously provide gain medium and optical cavity for performing nanoscale lasers with easy integration,ultracompact footprint,and low energy consumption.Here,we report Ⅲ-Ⅴsemiconductor NW lasers can also be used for self-frequency conversion to extend their output wavelengths,as a result of their non-centrosymmetric crystal structure and strongly localized optical field in the NWs.From a GaAs/In0.16Ga0.84As core/shell NW lasing at 1016 nm,an extra visible laser output at 508 nm is obtained via the process of second-harmonic generation,as confirmed by the far-field polarization dependence measurements and numerical modeling.From another NW laser with a larger diameter which supports multiple fundamental lasing wavelengths,multiple self-frequency-conversion lasing modes are observed due to second-harmonic generation and sum-frequency generation.The demonstrated self-frequency conversion of NW lasers opens an avenue for extending the working wavelengths of nanoscale lasers,even to the deep ultraviolet and THz range.展开更多
In this study,we demonstrate the axiotaxy driven growth of belt-shaped InAs nanowires using Au catalysts by molecular beam epitaxy.It is found that,the zinc-blende structured InAs nanowires,with the features of[113]gr...In this study,we demonstrate the axiotaxy driven growth of belt-shaped InAs nanowires using Au catalysts by molecular beam epitaxy.It is found that,the zinc-blende structured InAs nanowires,with the features of[113]growth direction and extensive{110}side-surfaces,are induced by catalysts in Au–In α phase through the axiotaxy growth,in which the lattice mismatch between the projections of atomic planes onto nanowire/catalyst interfaces is minimized by forming extraordinary tilted interfaces.Our atomic-resolution in situ TEM heating experiments show that the catalysts remained in the solid state of Au–In α phase during the axiotaxy growth,by which the vapor–solid–solid growth mechanism can be confirmed.Through manipulating the growth direction,this unusual growth mechanism can provide a practical pathway to control the morphology of the low-dimensional nanomaterials,from conventional nanowires to belt-shaped nanowires utilizing a significant lateral growth,simply using nanoparticles as catalyst.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12227901,12393830,and 12274429)the STCSM(Grant No.22QA1410600)。
文摘Interfacial disorders in semiconductor quantum wells(QWs)determine material properties and device performance and have attracted great research efforts using different experimental methods.However,so far,there has been no way to quantify the lateral length distribution of the interfacial disorders in QWs.Since photoluminescence(PL)is sensitive to exciton localization,the evolutions of PL energy and linewidth under external perpendicular magnetic fields have served as effective measurement methods for QW analysis;however,the evolution of PL intensity has not played a matching role.In this paper,we develop a theoretical model correlating the PL intensity with the interfacial disorders of type-I QWs under an external perpendicular magnetic field.We verify the model's rationality and functionality using In Ga(N)As/Ga As single QWs.In addition,we derive the Urbach energy and determine the lateral length distribution of interfacial disorders.The results show that the magnetic field-dependent PL intensity,as described by our model,serves as a valid probe for quantifying the interface flatness.The model also reveals that the mechanism of magnetic-field-induced intensity enhancement is a joint effect of interfacial disorder-induced exciton localization and the transfer of excitons from dark to bright states.These insights may benefit performance improvements of type-I QW materials and devices.
基金Project supported by National Key Research and Development Program of China(Grant No.2016YFB0402402)the National Natural Science Foundation of China(Grant No.61521005)
文摘This paper presents a review of recent advances in quantum well and quantum cascade infrared photodetectors developed in Shanghai Institute of Technical Physics, Chinese Academy of Sciences(SITP/CAS). Firstly, the temperature-and bias-dependent photocurrent spectra of very long wavelength(VLW) GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations in detail. We confirm that the first excited state, which belongs to the quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. Aided by band structure calculations, we propose a model of the double excited states that determine the working mechanism in VLW QWIPs. Secondly, we present an overview of a VLW QWIP focal plane array(FPA)with 320×256 pixels based on the bound to quasi-bound(BTQB) design. The technology of the manufacturing FPA based on the QWIP structures has been demonstrated. At the operating temperature of 45 K, the detectivity of QWIP FPA is larger than 1.4×10^(10) cm·Hz^(1/2)/W with a cutoff wavelength larger than 16 μm. Finally, to meet the needs of space applications, we proposed a new long wavelength quantum cascade detector with a broadband detection ranging from 7.6 μm to 10.4 μm. With a pair of identical coupled quantum wells separated by a thin barrier, acting as absorption regions, the relative linewidth(?E/E) of response can be dramatically broadened to 30.7%. It is shown that the spectral shape and linewidth can be tuned by the thickness of the thin barrier, while it is insensitive to the working temperature. The device can work above liquid nitrogen temperature with a peak responsivity of 63 mA/W and Johnson noise limited detectivity of 5.1×10~9 cm·Hz^(1/2)/W.
基金Project supported by the National Natural Science Foundation of China(Grant No.61991441)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000).
文摘The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.
基金Project supported by the State Key Basic Research Program of China(Grant Nos.2017YFA0205801,2017YFA0305500,and 2013CB632705)the National Natural Science Foundation of China(Grant Nos.11334008,61290301,61521005,61405230,and 61675222)+1 种基金the Youth Innovation Promotion Association(CAS)the Aviation Science Fund(Grant No.20162490001)
文摘Two-dimensional transition metal dichalcogenides(TMDs) provide fertile ground to study the interplay between dimensionality and electronic properties because they exhibit a variety of electronic phases, such as semiconducting, superconducting, charge density waves(CDW) states, and other unconventional physical properties. Compared with other classical TMDs, such as Mott insulator 1T–TaS_2 or superconducting 2H–NbSe_2, bulk 2H–TaSe_2 has been a canonical system and a touchstone for modeling the CDW measurement with a less complex phase diagram. In contrast to ordinary semiconductors that have only single-particle excitations, CDW can have collective excitation and carry current in a collective fashion. However, manipulating this collective condensation of these intriguing systems for device applications has not been explored. Here, the CDW-induced collective driven of non-equilibrium carriers in a field-effect transistor has been demonstrated for the sensitive photodetection at the highly-pursuit terahertz band. We show that the 2H–TaSe_2-based photodetector exhibits a fast photoresponse, as short as 14 μs, and a responsivity of over 27 V/W at room temperature. The fast response time, relative high responsivity and ease of fabrication of these devices yields a new prospect of exploring CDW condensate in TMDs with the aim of overcoming the existing limitations for a variety of practical applications at THz spectral range.
基金the National Natural Science Foundation of China (Grant No.10474020)Knowledge Innovation Program of the Chinese Academy of Sciences (No.C2-14)
文摘The staggered InGaN quantum well (QW) structure and the conventional InGaN QW structure for the emission at a particu-lar wavelength of 400 nm are designed and theoretically investigated,including the distribution of the carriers’ concentration,the radiative recombination rate,the Shockley-Read-Hall (SRH) recombination rate as well as the output performance and the internal quantum efficiency. The theoretical result indicates that the staggered QW structure offers significant improve-ment of carriers’ concentration in the QW,especially the hole concentration. The output power and the internal quantum efficiency also show 32.6 % and 32.5 % enhancement,respectively,in comparison with that of the conventional InGaN QW structure. The reduction of the electron overflow can be the main factor for the improvement of the optical perfor-mance for novel staggered InGaN QW structure.
基金National Natural Science Foundation of China,Grant/Award Numbers:61875223,61922082,61927813National Key R&D Program of China,Grant/Award Number:2021YFB2800702+3 种基金Jiangsu Province Key R&D Program,Grant/Award Numbers:BE2021007-3,BE2021007-2Shanghai Municipal Science and Technology Major Project,Grant/Award Number:2019SHZDZX01Science and Technology Commission of Shanghai Municipality,Grant/Award Number:21ZR1473800Vacuum Interconnected Nanotech Workstation(Nano-X)of Suzhou Institute of Nano-tech and Nano-bionics(SINANO),Chinese Academy of Sciences。
文摘As the lastly unexplored electromagnetic wave,terahertz(THz)radiation has been exploited in a plenty of contexts such as fundamental research,military and civil fields.Most recently,representative two-dimensional(2D)topological semimetal,platinum ditelluride(PtTe_(2))has attracted considerable research interest in THz detection due to its unique physical properties.However,to achieve practical applications,the low-cost,large-scale,controllable synthesis and efficient patterning of 2D materials are key requirements,which remain a challenge for PtTe_(2)and its photodetectors(PDs).Herein,a facile approach is developed to obtain waferscale(2-inches)patterned PtTe_(2)arrays using one-step tellurium-vapor transformation method and micro-Nano technology.PtTe_(2)PD arrays are fabricated with the as-grown PtTe_(2)arrays evenly distributed on a 2-inch wafer,exhibiting high conductivity(~2.7×105 S m^(-1))and good electrical consistency.Driven by the Dirac fermions,PtTe_(2)PDs achieve a broadband(0.02-0.3 THz)response with a fast response speed(~4.7μs),a high sensitivity(~47 pW Hz^(-1/2))and high-resolution transmission THz-imaging capability,which displays the potential of large-area THz array imaging.These results are one step towards the practical applications of integrated PD arrays based on 2D materials.
基金National Natural Science Foundation of China(11933006,61775229,61805060,61927813)Key Research and Development Program of Zhejiang Province(2020C01120)Sino-German Science Center(GZ1580)。
文摘Broadband response is pursued in both infrared(IR)and terahertz(THz)detection technologies,which find their applications in both terrestrial and astronomical realms.Herein,we report an ultrabroadband and multiband IR/THz detector based on blocked-impurity-band detecting principle.The detectors are prepared by implanting phosphorus into germanium(Ge:P),where photoresponses with a P impurity band,a self-interstitial defect band,and a vacancy-P(V-P)pair defect band are realized simultaneously.The response spectra of the detectors show ultrabroad and dual response bands in a range of 3-28μm(IR band)and 40-165μm(THz band),respectively.Additionally,a tiny mid-IR(MIR)band within 3-4.2μm is embedded in the IR band.The THz band arises from the P impurity band,whereas the IR and the MIR bands are ascribed to the two defect bands.At150 m V and 4.5 K,the peak detectivities of the three bands are obtained as 2.9×10^(12) Jones(at 3.9μm),6.8×10^(12) Jones(at 16.3μm),and 9.9×10^(12) Jones(at 116.5μm),respectively.The impressive coverage andsensitivity of the detectors are promising for applications in IR and THz detection technologies.
基金Science and Technology Program of Shaanxi Province,Grant/Award Number:2017KJXX-16Natural Science Basic。
文摘Platinum telluride(PtTe_(2)),a member of metallic transition metal dichalcogenides,provides a new platform for investigating various properties such as type-II Dirac fermions,topological superconductivity,and wide-band photodetection.However,the study of PtTe_(2)is largely limited to exfoliated flakes,and its direct synthesis remains challenging.Herein,we report the controllable synthesis of highly crystalline 2D PtTe_(2)crystals with tunable morphology and thickness via chemical vapor deposition(CVD)growth on Au substrate.By adjusting Te amount and substrate temperature,anisotropic and isotropic growth modes of PtTe_(2)were realized on the solid and molten Au substrates,respectively.The domain size of PtTe_(2)crystal was achieved up to 30μm,and its thickness can be tuned from 5.6 to 50 nm via controlling the growth time.Furthermore,a metal–PtTe_(2)–metal structural device was fabricated to validate the wide-band terahertz(THz)photodetection from 0.04 to 0.3 THz at room temperature.Owing to the high crystallinity of PtTe_(2)crystal,the photodetector acquires high responsivity(30–250 mA W-1 from 0.12 to 0.3 THz),fast response rate(rise time:7μs,decay time:8μs),and high-quality imaging ability.Our work demonstrates the feasibility for realistic exploitation of high-performing photodetection system at THz band based on the CVDgrown 2D Dirac semimetal materials.
基金This work was supported by the National Key R&D Program of China(No.2021YFB2800702)the National Natural Science Foundation of China(Nos.61521005,61875217,91850208)+4 种基金the STCSM Grants(Nos.1859078100,19590780100)The project was funded by State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(KF1809)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Zhejiang Lab(No.2021MB0AB01)the Natural Science Foundation of Shanghai(No.21ZR1402200).
文摘Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal.Here,we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe_(2)and its van der Waals heterostructures.Explicitly,we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime(λ/10^(4)),featuring colossal photoresponse by in-plane symmetry breaking.The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe_(2)Dirac semimetal,yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding∼0.2 A/W and noise-equivalent power(NEP)less than~38 pW/Hz^(0.5),as well as superb ambient stability.Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging,remote sensing or security applications.
基金the Australian Research Council,the National Key R&D Program of China(No.2016YFB0402401)the National Natural Science Foundation of China(Nos.11634009 and 11774016)+1 种基金the Key Programs of Frontier Science of the Chinese Academy of Sciences(No.QYZDJ-SSW-JSC007)The Australian Microscopy&Microanalysis Research Facility is also gratefully acknowledged for providing microscopy facilities for this study.
文摘In this study,we report the growth of free-standing InAs nanosheets using Au catalysts in molecular beam epitaxy.Detailed structural characterizations suggest that wurtzite structured InAs nanosheets,with features of extensive{1120}surfaces,grown along the<1102>direction and adopted{0001}nanosheet/catalyst interfaces,are initiated from wurtzite structured[0001]nanowires as the inclined epitaxial growth due to relatively higher In concentrations in Au catalysts,and grown from these inclined nanostructures through catalyst-induced axial growth and their enhanced lateral growth under the high growth temperature.Based on the facts that the nanosheets contain large low energy{1120}surfaces and{0001}nanosheet/catalyst interfaces,the growth of our nanosheets is a thermodynamically driven process.This study provides new insights into fabricating free-standing Ⅲ-Ⅴ nanosheets for their applications in future nanoscale devices.
基金This work is supported by the National Key R&D Program of China(Grant Nos.2018YFA0307200 and 2017YFA0303800)the National Natural Science Foundation of China(Grant Nos.61775183,11634010,61905196,and 62005222)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.3102017jc01001,3102019JC008,and 3102019110x032)the Natural Science Basic Research Program of Shaanxi Province(2020JQ 222).
文摘Semiconductor nanowires(NWs)could simultaneously provide gain medium and optical cavity for performing nanoscale lasers with easy integration,ultracompact footprint,and low energy consumption.Here,we report Ⅲ-Ⅴsemiconductor NW lasers can also be used for self-frequency conversion to extend their output wavelengths,as a result of their non-centrosymmetric crystal structure and strongly localized optical field in the NWs.From a GaAs/In0.16Ga0.84As core/shell NW lasing at 1016 nm,an extra visible laser output at 508 nm is obtained via the process of second-harmonic generation,as confirmed by the far-field polarization dependence measurements and numerical modeling.From another NW laser with a larger diameter which supports multiple fundamental lasing wavelengths,multiple self-frequency-conversion lasing modes are observed due to second-harmonic generation and sum-frequency generation.The demonstrated self-frequency conversion of NW lasers opens an avenue for extending the working wavelengths of nanoscale lasers,even to the deep ultraviolet and THz range.
基金This work was supported by the Australian Research Council,the National Key R&D Program of China(No.2016YFB0402401)the National Natural Science Foundation of China(Nos.11634009,11774016,and 61974138)+2 种基金the Natural Science Basic Research Program of Shaanxi Province(No.2020JQ-222)the Key Programs of Frontier Science of the Chinese Academy of Sciences(No.QYZDJ-SSW-JSC007)Dong Pan acknowledges the support from the Youth Innovation Promotion Association,the Chinese Academy of Sciences(Grant 2017156).
文摘In this study,we demonstrate the axiotaxy driven growth of belt-shaped InAs nanowires using Au catalysts by molecular beam epitaxy.It is found that,the zinc-blende structured InAs nanowires,with the features of[113]growth direction and extensive{110}side-surfaces,are induced by catalysts in Au–In α phase through the axiotaxy growth,in which the lattice mismatch between the projections of atomic planes onto nanowire/catalyst interfaces is minimized by forming extraordinary tilted interfaces.Our atomic-resolution in situ TEM heating experiments show that the catalysts remained in the solid state of Au–In α phase during the axiotaxy growth,by which the vapor–solid–solid growth mechanism can be confirmed.Through manipulating the growth direction,this unusual growth mechanism can provide a practical pathway to control the morphology of the low-dimensional nanomaterials,from conventional nanowires to belt-shaped nanowires utilizing a significant lateral growth,simply using nanoparticles as catalyst.
