InSe-Te van der Waals heterostructures for current rectification and photodetection

As the basis of modern electronics and optoelectronics,high-performance,multi-functional p-n junctions have manifested and occupied an important position.However,the performance of the silicon-based p-n junctions declines gradually as the thickness approaches to few nanometers.The heterojunction constructed by two-dimensional(2D)materials can significantly improve the device performance compared with traditional technologies.Here,we report the In Se-Te type-II van der Waals heterostructures with rectification ratio up to 1.56×10^(7) at drain-source voltage of±2 V.The p-n junction exhibits a photovoltaic and photoelectric effect under different laser wavelengths and densities and has high photoresponsivity and detectivity under low irradiated light power.Moreover,the heterojunction has stable photo/dark current states and good photoelectric switching characteristics.Such high-performance heterostructured device based on 2D materials provides a new way for futural electronic and optoelectronic devices.

8-nm narrowband photodetection in diamonds

Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broadband photodetectors and filters,which complicates the architecture and constrains imaging quality.Here,we introduce an electronic-grade diamond single-crystal photodetector exhibiting an exceptionally narrow spectral response in the DUV range with a full width at half maximum of 8 nm.By examining diamond photodetectors with varying dislocation densities,we propose that mitigating the defect-induced trapping effect to achieve charge collection narrowing,assisted by free exciton radiative recombination,is an effective strategy for narrowband photodetection.The superior performance of this device is evidenced through the imaging of DUV light sources,showcasing its capability to differentiate between distinct light sources and monitor human-safe sterilization systems.Our findings underscore the promising potential applications of electronicgrade diamond in narrowband photodetection and offer a valuable technique for identifying electronic-grade diamond.

Surface plasmon enhanced infrared photodetection

Infrared photodetectors have been used extensively in biomedicine, surveillance, communication and astronomy. However, state of the art technology based on III-V and II-VI compounds still lacks excellent performance for high-temperature operation. Surface plasmon polaritons (SPPs) have demonstrated their capability in improving the light detection from visible to infrared wave range due to their light confinement in subwavelength scale. Advanced fabrication techniques such as electron-beam lithography (EBL) and focused ion-beam (FIB), and commercially available numerical design tool like Finite-Difference Time-Domain (FDTD) have enabled rapid development of surface plasmon (SP) enhanced photodetectors. In this review article, the basic mechanisms behind the SP-enhanced photodetection, the different type of plasmonic nanostructures utilized for enhancement, and the reported SP-enhanced infrared photodetectors will be discussed.

Fast-speed self-powered PEDOT:PSS/α-Ga_(2)O_(3)nanorod array/FTO photodetector with solar-blind UV/visible dual-band photodetection

Theα-Ga2 O_(3)nanorod array is grown on FTO by hydrothermal and annealing processes.And a self-powered PEDOT:PSS/α-Ga_(2)O_(3)nanorod array/FTO(PGF)photodetector has been demonstrated by spin coating PEDOT:PSS on theα-Ga_(2)O_(3)nanorod array.Successfully,the PGF photodetector shows solar-blind UV/visible dual-band photodetection.Our device possesses comparable solar-blind UV responsivity(0.18 mA/W at 235 nm)and much faster response speed(0.102 s)than most of the reported self-poweredα-Ga_(2)O_(3)nanorod array solar-blind UV photodetectors.And it presents the featured and distinguished visible band photoresponse with a response speed of 0.136 s at 540 nm.The response time is also much faster than the other non-self-poweredβ-Ga_(2)O_(3)DUV/visible dual-band photodetectors due to the fast-speed separation of photogenerated carries by the built-in electric field in the depletion regions of PEDOT:PSS/α-Ga_(2)O_(3)heterojunction.The results herein may prove a promising way to realize fast-speed self-poweredα-Ga_(2)O_(3)photodetectors with solar-blind UV/visible dual-band photodetection by simple processes for the applications of multiple-target tracking,imaging,machine vision and communication.

New approach for deriving density operator for describing continuum photodetection process

By introducing the two-mode entangled state representation 〈η｜ whose one mode is a fictitious one accompanying the system mode, this paper presents a new approach for deriving density operator for describing continuum photodetection process.

Realization of stimulated emission-based detector and its application to antinormally ordered photodetection

Using a stimulated parametric down-conversion process combined with a conventional detector, we theoretically propose a scheme to realize the stimulated emission-based detector, and investigate the antinormalty ordered correlation function and Fano factor for the coherent field based on it. Such a detection has advantages over the normally ordered one especially when the intensity of the field is weak.

Polymer: Non-fullerene acceptor heterojunction-based phototransistor for short-wave infrared photodetection

It remains full of challenge for extending short-wave infrared(SWIR)spectral response and weak-light detection in the context of broad spectral responses for phototransistor.In this work,a novel poly(2,5-bis(4-hexyldodecyl)-2,5-dihydro-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thiophene)(PDPPT3-HDO):COTIC-4F organic bulk-heterojunction is prepared as active layer for bulk heterojunction phototransistors.PDPPT3-HDO serves as a hole transport material,while COTIC-4F enhances the absorption of SWIR light to 1020 nm.As a result,smooth and connected PDPPT3-HDO film is fabricated by blade coating method and exhibits high hole mobility up to 2.34 cm^(2)·V^(-1)·s^(-1) with a current on/off ratio of 4.72×10^(5) in organic thin film transistors.PDPPT3-HDO:COTIC-4F heterojunction phototransistors exhibit high responsivity of 2680 A·W^(-1) to 900 nm and 815 A·W^(-1) to 1020 nm,with fast response time(rise time~20 ms and fall time~100 ms).The photosensitivity of the heterojunction phototransistor improves as the mass ratio of non-fullerene acceptors increases,resulting in an approximately two orders of magnitude enhancement compared to the bare polymer phototransistor.Importantly,the phototransistor exhibits decent responsivity even under ultra-weak light power of 43μW·cm^(-2) to 1020 nm.This work represents a highly effective and general strategy for fabricating efficient and sensitive SWIR light photodetectors.

Anomalous magnetic property and broadband photodetection in ultrathin non-layered manganese selenide semiconductor

Two-dimensional(2D)semiconductors with intrinsic ferromagnetism are highly desirable for potential applications in nextgeneration spintronic and optoelectronic devices.However,controllable synthesis of intrinsic 2D magnetic semiconductor on a substrate is still a challenging task.Herein,large-area 2D non-layered rock salt(α-phase)MnSe nanosheets were grown on mica substrates,with the thickness changing from 54.2 to 0.9 nm(one unit cell),by chemical vapour deposition.The X-ray diffraction,Raman spectroscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy measurements confirmed that the resulting 2Dα-MnSe nanosheets were obtained as high-quality single crystals.The magnetic hysteresis loops and synchrotron X-ray measurements directly indicated the anomalous magnetic properties inα-MnSe nanosheets.Comprehensive analysis of the reasons for magnetic property revealed that the low-temperature phase transition,small number of stacking differences in crystals,and surface weak oxidation in(111)-orientedα-MnSe were the main mechanisms.Furthermore,α-MnSe nanosheets exhibited broadband photoresponse from 457 to 671 nm with an outstanding detectivity and responsivity behaviours.This study presents the detailed growth process of ultrathin 2D magnetic semiconductorα-MnSe,and its outstanding magnetic properties and broadband photodetection,which provide an excellent platform for magneto-optical and magneto-optoelectronic research.

On-chip integrated GeSe_(2)/Si vdW heterojunction for ultravioletenhanced broadband photodetection,imaging,and secure optical communication

Broadband photodetection,spanning from ultraviolet(UV)to infrared(IR),is pivotal in diverse technological domains including astronomy,remote sensing,environmental monitoring,and medical diagnostics.However,current commercially available broadband photodetectors,predominately based on conventional narrow-bandgap semiconductors,exhibit limited sensitivity in the UV region.This limitation,stemming from the significant energy disparity between the semiconductor bandgap and UV photon,narrows their application scope.Herein,we report an innovative approach involving the in-situ van der Waals(vdW)integration of two-dimensional(2D)GeSe_(2)layers onto a Si substrate.This process yields a high-quality GeSe_(2)/Si vdW heterojunction device,which features a broad response range covering from UV to near-IR(NIR)with a greatly-enhanced sensitivity in the UV region.The device possesses high responsivities of 325 and 533.4 mA/W,large detectivities of 1.24×10^(13)and 2.57×10^(13)Jones,and fast response speeds of 20.6/82.1 and 17.7/81.0μs under 360 and 980 nm,respectively.Notably,the broadband image sensing and secure invisible optical communication capabilities of the GeSe_(2)/Si heterojunction device are demonstrated.Our work provides a viable approach for UV-enhanced broadband photodetection technology,opening up new possibilities and applications across various scientific and technological domains.

Wafer-scale patterned growth of type-II Dirac semimetal platinum ditelluride for sensitive room-temperature terahertz photodetection

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.

Enhancement of silicon sub‑bandgap photodetection by helium‑ion implantation

Silicon sub-bandgap photodetectors can detect light at the infrared telecommunication wavelengths but with relatively weak photo-response.In this work,we demonstrate the enhancement of sub-bandgap photodetection in silicon by helium-ion implantation,without afecting the transparency that is an important benefcial feature of this type of photodetectors.With an implantation dose of 1×10^(13)ions/cm^(2),the minimal detectable optical power can be improved from−33.2 to−63.1 dBm,or,by 29.9 dB,at the wavelength of 1550 nm,and the photo-response at the same optical power(−10 dBm)can be enhanced by approximately 18.8 dB.Our work provides a method for strategically modifying the intrinsic trade-of between transparency and strong photo-responses of this type of photodetectors.

Ga/GaSb nanostructures:Solution-phase growth for highperformance infrared photodetection

Gallium antimonide(GaSb)-based nanostructures have been reported via various vapor-phase synthetic routes while there is not a report on the growth of GaSb nanostructures via a complete one-step solution-phase synthetic strategy.Herein we report the design and synthesis of tadpole-like Ga/GaSb nanostructures by a one-step solution-phase synthetic route typically from the precursors of commercial triphenyl antimony(Sb(Ph)_(3))and trimethylaminogallium(Ga(NMe_(2))_(3))at 260°C in 1-octadecene.The GaSb nanocrystals are grown based on a solution–liquid–solid(SLS)mechanism with zinc blende phase,and their size and shape can be controlled in the procedures via manipulating the reaction conditions.Meanwhile,the tadpole-like Ga/GaSb nanostructures can be applied for the fabrication of a GaSb/Si nanostructured heterojunction-like photodetector over silicon wafer,which demonstrates excellent photoresponse and detection performances from wavelength of 405 to 1,064 nm with high photoresponding rate.Typically,the photodetector exhibits a high responsivity of 18.9 A·W^(−1),a superior detectivity of 1.1×10^(13)Jones,and an ultrafast response speed of 44 ns.The present work provides a new strategy to group III–V antimonide-based semiconducting nanostructures that are capable for the fabrication of photodetector with broadband,high-detectivity,and high-speed photodetecting performances.

Photo-driven fin field-effect transistors

The integration between infrared detection and modern microelectronics offers unique opportunities for compact and high-resolution infrared imaging.However,silicon,the cornerstone of modern microelectronics,can only detect light within a limited wavelength range(<1100 nm)due to its bandgap of 1.12 eV,which restricts its utility in the infrared detection realm.Herein,a photo-driven fin field-effect transistor is presented,which breaks the spectral response constraint of conventional silicon detectors while achieving sensitive infrared detection.This device comprises a fin-shaped silicon channel for charge transport and a lead sulfide film for infrared light harvesting.The lead sulfide film wraps the silicon channel to form a“three-dimensional”infrared-sensitive gate,enabling the photovoltage generated at the lead sulfide-silicon junction to effectively modulate the channel conductance.At room temperature,this device realizes a broadband photodetection from visible(635 nm)to short-wave infrared regions(2700 nm),surpassing the working range of the regular indium gallium arsenide and germanium detectors.Furthermore,it exhibits low equivalent noise powers of 3.2×10^(-12) W·Hz^(-1/2) and 2.3×10^(-11) W·Hz^(-1/2) under 1550 nm and 2700 nm illumination,respectively.These results highlight the significant potential of photo-driven fin field-effect transistors in advancing uncooled silicon-based infrared detection.

Enhancement of MoTe2 near-infrared absorption with gold hollow nanorods for photodetection

Infrared(IR)light photodetection based on two dimensional(2D)materials of proper bandgap has attracted increasing attention.However,the weak IR absorption in 2D materials,due to their ultrathin attribute and indirect bandgap in multilayer structures,degrades their performance when used as IR photodetectors.In this work,we utilize the fact that few-layer MoTe2 flake has a near-IR(NIR)bandgap and demonstrate a^60-fold enhancement of NIR response by introducing a gold hollow nanorods on the surface.Such gold hollow nanorods have distinct absorption peak located also at the NIR regime,therefore induces strong resonance,benefitting NIR absorption in MoTe2,resulting in strong near-field enhancement.With the evidence from steady and transient state optical spectra,we confirm that the enhancement of NIR response originates only photon absorption,rather than electron transport at interfaces as observed in other heterostructures,therefore,precluding the requirement of high-quality interfaces for commercial applications.

Controllable growth of type-II Dirac semimetal PtTe2 atomic layer on Au substrate for sensitive room temperature terahertz photodetection

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.

Unconventionally anisotropic growth of PbSe nanorods:Controllable fabrication under solution-solid-solid regime over Ag2Se catalysis for broadband photodetection

Broadband optoelectronic devices intrigue enormous interests on account of their promising potential in optical communications,sensors and environmental monitoring.PbSe nanocrystals are promising candidates for the construction of next-generation photodetectors due to their fascinating intrinsic properties and solution-processed compatibility with varied substrates.Here,we report the fabrication of a broadband photodetector on the basis of high-quality solution-processed PbSe nanorods in rock-salt phase grown along unconventionally anisotropic growth direction of<112>zone axis.The rock-salt PbSe nanorods are synthesized in solution phase over the catalysis of Ag2Se with relatively high-temperature body-centered cubic phase via a solution-solid-solid growth regime using oleylamine and oleic acid as solvents and stabilizer surfactants,from which the PbSe nanorods with the unconventionally anisotropic growth direction are controllably grown in size and shape in the synthetic procedure typically with about 17 nm in diameter and 58 nm in length on average.Meanwhile,the PbSe nanorods-based photodetector exhibits a broadband response from 405 to 1,064 nm with a high responsivity of 0.78 A·W^(-1)and a fast response time of 17.5μs.The response time is much faster in comparison with most of the PbSe-based photodetectors with response time in millisecond level.

Plasmonic silicon quantum dots extend photodetection into mid-infrared range

Nowadays the development of Internet of Things(IoT)and defense technologies imperatively needs high-performance photodetectors that can work in a broadband wavelength range,in particular,covering the mid-infrared(MIR)region[1].This generates great interest in the incorporation of a series of novel optoelectronic materials and structures into the photodetectors.Graphene and colloidal quantum dots(QDs)are key players among novel materials used to fabricate high-performance photodetectors[2–4].By taking advantage of the high mobility of

Thickness-dependent highly sensitive photodetection behavior of lead-free all-inorganic CsSnBr_(3) nanoplates

Non-layered two-dimensional(2D) lead-free all-inorganic perovskites nanoplates have recently attracted considerable attention in photodetectors;however, the indepth investigation of thickness on photodetection performance is still lacking. In this work, by constructing the famous metal-semiconductor-metal photodetectors, the photodetection behaviors of thickness-controlled CsSnBr;nanoplates are investigated systematically. Ni electrodes are adopted for ensuring the good ohmic contact behaviors of as-fabricated photodetectors. With the increase in thickness, the photodetection performances improve accordingly, such as photocurrent increases from 0.22 to 19.40 nA, responsivity increases from 72.9 to 4893.7 mA·W^(-1), rise/decay time decreases from 11/35 to 3/10 ms, respectively. Notability, the dark current also increases with the increase in thickness, making the further investigation on the reduction in dark current meaningful.All of the as-fabricated photodetectors are stable, suggesting the careful thickness selection in next-generation high-performance lead-free all-inorganic perovskites photodetectors.

Stoichiometric effect on electrical and near-infrared photodetection properties of full-composition-range GaAs1−xSbx nanowires

As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the whole near-infrared (NIR) region, for technological applications in next-generation high-performance electronics and NIR photodetection. However, it is still a challenge to the synthesis of high-quality GaAs1−xSbx NWs across the entire range of composition, resulting in the lack of correlation investigation among stoichiometry, microstructure, electronics, and NIR photodetection. Here, we demonstrate the success growth of high-quality GaAs1−xSbx NWs with full composition range by adopting a simple and low-cost surfactant-assisted solid source chemical vapor deposition method. All of the as-prepared NWs are uniform, smooth, and straight, without any phase segregation in all stoichiometric compositions. The lattice constants of each NW composition have been well correlated with the chemical stoichiometry and confirmed by high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectrum. Moreover, with the increase of Sb concentration, the hole mobility of the as-fabricated field-effect-transistors and the responsivity and detectivity of the as-fabricated NIR photodetectors increase accordingly. All the results suggest a careful stoichiometric design is required for achieving optimal NW device performances.

High-performance and broadband photodetection of bicrystalline(GaN)_(1-x)(ZnO)_(x)solid solution nanowires via crystal defect engineering

Crystal defect engineering is widely used as an effective approach to regulate the optical and optoelectronic properties of semiconductor nanostructures.However,photogenerated electron-hole pair recombination centers caused by structural defects usually lead to the reduction of optoelectronic performance.In this work,a high-performance photodetector based on(GaN)_(1-x)(ZnO)_(x)solid solution nanowire with bicrystal structure is fabricated and it shows excellent photoresponse to ultraviolet and visible light.The highest responsivity of the photodetector is as high as 60,86 and 43 A/W under the irradiation of365 nm,532 nm and 650 nm,respectively.The corresponding response time is as fast as 170,320 and 160 ms.Such wide spectral responses can be attributed to various intermediate energy levels induced by the introduction of various structural defects and dopants in the solid solution nanowire.Moreover,the peculiar bicrystal boundary along the axial direction of the nanowire provides two parallel and fast transmission channels for photo-generated carriers,reducing the recombination of photo-generated carriers.Our findings provide a valued example using crystal defect engineering to broaden the photoresponse range and improve the photodetector performance and thus can be extended to other material systems for various optoelectronic applications.