Showing papers on "Photodetection published in 2018"

Ultrasmall Bismuth Quantum Dots: Facile Liquid-Phase Exfoliation, Characterization, and Application in High-Performance UV–Vis Photodetector

Abstract: Two-dimensional (2D) monoelemental bismuth (Bi) crystal, one of the pnictogens (group VA), has recently attracted increasing interest because of its intriguing characteristics. Here, uniformly sized 2D Bi quantum dots (BiQDs) with an average diameter (thickness) of 4.9 ± 1.0 nm (2.6 ± 0.7 nm) were fabricated through a facile liquid-phase exfoliation (LPE) method, and the corresponding photoresponse was evaluated using photoelectrochemical (PEC) measurements. The as-fabricated BiQDs-based photodetector not only exhibits an appropriate capacity for self-driven broadband photoresponse but also shows high-performance photoresponse under low bias potentials ranging from UV to visible light in association with long-term stability of the ON/OFF switching behavior. In terms of these findings, it is further anticipated that the resultant BiQDs possess promising potential in UV–visible photodetection as well as in liquid optoelectronics. Our work may open a new avenue for delivering high-quality monoelemental pnict...

Ultrafast and sensitive photodetector based on a PtSe2/silicon nanowire array heterojunction with a multiband spectral response from 200 to 1550 nm

Abstract: The newly discovered Group-10 transition metal dichalcogenides (TMDs) like PtSe2 have promising applications in high-performance microelectronic and optoelectronic devices due to their high carrier mobilities, widely tunable bandages and ultrastabilities. However, the optoelectronic performance of broadband PtSe2 photodetectors integrated with silicon remains undiscovered. Here, we report the successful preparation of large-scale, uniform and vertically grown PtSe2 films by simple selenization method for the design of a PtSe2/Si nanowire array heterostructure, which exhibited a very good photoresponsivity of 12.65 A/W, a high specific detectivity of 2.5 × 1013 Jones at −5 V and fast rise/fall times of 10.1/19.5 μs at 10 kHz without degradation while being capable of responding to high frequencies of up to 120 kHz. Our work has demonstrated the compatibility of PtSe2 with the existing silicon technology and ultrabroad band detection ranging from deep ultraviolet to optical telecommunication wavelengths, which can largely cover the limitations of silicon detectors. Further investigation of the device revealed pronounced photovoltaic behavior at 0 V, making it capable of operating as a self-powered photodetector. Overall, this representative PtSe2/Si nanowire array-based photodetector offers great potential for applications in next-generation optoelectronic and electronic devices. Aligning ultra-thin semiconductors with silicon nanowires enables high-speed sensing of an unusually broad range of ultraviolet, visible, and infrared light frequencies. The shapes of silicon nanowires enable quicker and more effective light detection than conventional thin films, but their spectral response still falls outside the parameters needed for various applications, including optical telecommunication. Researchers led by Di Wu from China’s Zhengzhou University and Yuen Hong Tsang at Hong Kong Polytechnic University turned to the broadband absorption of graphene-like platinum selenide (PtSe2) films to extend the light sensitivity. To parallel the geometry of nanowires, the team used precision deposition techniques to grow 2D PtSe2 films into vertically-oriented layers, some tens of nanometers thick. Direct transfer of the PtSe2 film onto a large-scale nanowire array produced a microsecond-fast device sensitive to multiple optical bands. Platinum diselenide (PtSe2) is a newly discovered Group-10 transition metal dichalcogenide (TMD) which has unique electronic properties, in particular a semimetal-to-semiconductor transition. In this work, we have demonstrated the proposed vertically standing layered structure PtSe2 nanofilms based on hybrid heterojunction with high overall performance was realized for broadband light photodetection ranging from 200 nm to 1550 nm. The high-performance broadband photodetector will open up a new pathway for the development of next-generation two dimensional Group-10 materials based optoelectronic devices.

Air-Stable In-Plane Anisotropic GeSe2 for Highly Polarization-Sensitive Photodetection in Short Wave Region

Abstract: In-plane anisotropic layered materials such as black phosphorus (BP) have emerged as an important class of two-dimensional (2D) materials that bring a new dimension to the properties of 2D materials, hence providing a wide range of opportunities for developing conceptually new device applications. However, all of recently reported anisotropic 2D materials are relatively narrow-bandgap semiconductors (<2 eV), and there has been no report about this type of materials with wide bandgap, restricting the relevant applications such as polarization-sensitive photodetection in short wave region. Here we present a new member of the family, germanium diselenide (GeSe2) with a wide bandgap of 2.74 eV, and systematically investigate the in-plane anisotropic structural, vibrational, electrical, and optical properties from theory to experiment. Photodetectors based on GeSe2 exhibit a highly polarization-sensitive photoresponse in short wave region due to the optical absorption anisotropy induced by in-plane anisotropy ...

Fast and Sensitive Colloidal Quantum Dot Mid-Wave Infrared Photodetectors.

Abstract: Colloidal quantum dots (CQDs) with a band gap tunable in the mid-wave infrared (MWIR) region provide a cheap alternative to epitaxial commercial photodetectors such as HgCdTe (MCT) and InSb. Photoconductive HgTe CQD devices have demonstrated the potential of CQDs for MWIR photodetection but face limitations in speed and sensitivity. Recently, a proof-of-concept HgTe photovoltaic (PV) detector was realized, achieving background-limited infrared photodetection at cryogenic temperatures. Using a modified PV device architecture, we report up to 2 orders of magnitude improvement in the sensitivity of the HgTe CQD photodetectors. A solid-state cation exchange method was introduced during device fabrication to chemically modify the interface potential, leading to an order of magnitude improvement of external quantum efficiency at room temperature. At 230 K, the HgTe CQD photodetectors reported here achieve a sensitivity of 109 Jones with a cutoff wavelength between 4 and 5 μm, which is comparable to that of comm...

100 GHz Plasmonic Photodetector

Abstract: Photodetectors compatible with CMOS technology have shown great potential in implementing active silicon photonics circuits, yet current technologies are facing fundamental bandwidth limitations. Here, we propose and experimentally demonstrate for the first time a plasmonic photodetector achieving simultaneously record-high bandwidth beyond 100 GHz, an internal quantum efficiency of 36% and low footprint. High-speed data reception at 72 Gbit/s is demonstrated. Such superior performance is attributed to the subwavelength confinement of the optical energy in a photoconductive based plasmonic-germanium waveguide detector that enables shortest drift paths for photogenerated carriers and a very small resistance-capacitance product. In addition, the combination of plasmonic structures with absorbing semiconductors enables efficient and highest-speed photodetection. The proposed scheme may pave the way for a cost-efficient CMOS compatible and low temperature fabricated photodetector solution for photodetection b...

Solution-Processed 3D RGO-MoS2 /Pyramid Si Heterojunction for Ultrahigh Detectivity and Ultra-Broadband Photodetection.

Abstract: Molybdenum disulfide (MoS2 ), a typical 2D metal dichalcogenide (2DMD), has exhibited tremendous potential in optoelectronic device applications, especially in photodetection. However, due to the weak light absorption of planar mono-/multilayers, limited cutoff wavelength edge, and lack of high-quality junctions, most reported MoS2 -based photodetectors show undesirable performance. Here, a structurized 3D heterojunction of RGO-MoS2 /pyramid Si is demonstrated via a simple solution-processing method. Owing to the improved light absorption by the pyramid structure, the narrowed bandgap of the MoS2 by the imperfect crystallinity, and the enhanced charge separation/transportation by the inserted reduced graphene oxide (RGO), the assembled photodetector exhibits excellent performance in terms of a large responsivity of 21.8 A W-1 , extremely high detectivity up to 3.8 × 1015 Jones (Jones = cm Hz1/2 W-1 ) and ultrabroad spectrum response ranging from 350 nm (ultraviolet) to 4.3 µm (midwave infrared). These device parameters represent the best results for MoS2 -based self-driven photodetectors, and the detectivity value sets a new record for the 2DMD-based photodetectors reported thus far. Prospectively, the design of novel 3D heterojunction can be extended to other 2DMDs, opening up the opportunities for a host of high-performance optoelectronic devices.

Gold-patched graphene nano-stripes for high-responsivity and ultrafast photodetection from the visible to infrared regime

Abstract: Graphene is a very attractive material for broadband photodetection in hyperspectral imaging and sensing systems. However, its potential use has been hindered by tradeoffs between the responsivity, bandwidth, and operation speed of existing graphene photodetectors. Here, we present engineered photoconductive nanostructures based on gold-patched graphene nano-stripes, which enable simultaneous broadband and ultrafast photodetection with high responsivity. These nanostructures merge the advantages of broadband optical absorption, ultrafast photocarrier transport, and carrier multiplication within graphene nano-stripes with the ultrafast transport of photocarriers to gold patches before recombination. Through this approach, high-responsivity operation is realized without the use of bandwidth-limiting and speed-limiting quantum dots, defect states, or tunneling barriers. We demonstrate high-responsivity photodetection from the visible to infrared regime (0.6 A/W at 0.8 μm and 11.5 A/W at 20 μm), with operation speeds exceeding 50 GHz. Our results demonstrate improvement of the response times by more than seven orders of magnitude and an increase in bandwidths of one order of magnitude compared to those of higher-responsivity graphene photodetectors based on quantum dots and tunneling barriers.

Narrow bandgap oxide nanoparticles coupled with graphene for high performance mid-infrared photodetection

Abstract: The pursuit of optoelectronic devices operating in the mid-infrared regime is driven by both fundamental interests and envisioned applications ranging from imaging, sensing to communications. Despite continued achievements in traditional semiconductors, notorious obstacles such as the complicated growth processes and cryogenic operation preclude the usage of infrared detectors. As an alternative path towards high-performance photodetectors, hybrid semiconductor/graphene structures have been intensively explored. However, the operation bandwidth of such photodetectors has been limited to visible and near-infrared regimes. Here we demonstrate a mid-infrared hybrid photodetector enabled by coupling graphene with a narrow bandgap semiconductor, Ti2O3 (Eg = 0.09 eV), which achieves a high responsivity of 300 A W−1 in a broadband wavelength range up to 10 µm. The obtained responsivity is about two orders of magnitude higher than that of the commercial mid-infrared photodetectors. Our work opens a route towards achieving high-performance optoelectronics operating in the mid-infrared regime. Coupling graphene with narrow band-gap Ti2O3 nanoparticles can enable efficient mid-infrared photodetection. Here, the authors report a graphene-Ti2O3 based hybrid photodetector with high responsivity of ~300 A W-1 up to 10 μm by varying the number of graphene layers and size of Ti2O3 nanoparticles.

Plasmonic Resonance Enhanced Polarization-Sensitive Photodetection by Black Phosphorus in Near Infrared.

Abstract: Black phosphorus, a recently intensely investigated two-dimensional material, is promising for electronic and optoelectronic applications due to its higher mobility and thickness-dependent direct band gap. With its low direct band gap and anisotropic properties in nature, black phosphorus is also suitable for near-infrared polarization-sensitive photodetection. To enhance photoresponsivity of a black phosphorus based photodetector, we demonstrate two designs of plasmonic structures. In the first design, plasmonic bowtie antennas are used to increase the photocurrent, particularly in the armchair direction, where the optical absorption is higher than that in the zigzag direction. The simulated electric field distribution with bowtie structures shows enhanced optical absorption by localized surface plasmons. In the second design, bowtie apertures are used to enhance the inherent polarization selectivity of black phosphorus. A high photocurrent ratio (armchair to zigzag) of 8.7 is obtained. We choose a near-...

Nanophotonics with 2D transition metal dichalcogenides [Invited].

Abstract: Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) have recently become attractive materials for several optoelectronic applications, such as photodetection, light harvesting, phototransistors, light-emitting diodes, and lasers. Their bandgap lies in the visible and near-IR range, and they possess strong excitonic resonances, high oscillator strengths, and valley-selective response. Coupling these materials to optical nanocavities enhances the quantum yield of exciton emission, enabling advanced quantum optics and nanophotonics devices. Here, we review the state-of-the-art advances of hybrid exciton-polariton structures based on monolayer TMDCs coupled to plasmonic and dielectric nanocavities. We discuss the optical properties of 2D WS2, WSe2, MoS2 and MoSe2 materials, paying special attention to their energy bands, photoluminescence/absorption spectra, excitonic fine structure, and to the dynamics of exciton formation and valley depolarization. We also discuss light-matter interactions in such hybrid exciton-polariton structures. Finally, we focus on weak and strong coupling regimes in monolayer TMDCs-based exciton-polariton systems, envisioning research directions and future opportunities for this material platform.

Perpendicular Optical Reversal of the Linear Dichroism and Polarized Photodetection in 2D GeAs.

Abstract: The ability to detect linearly polarized light is central to practical applications in polarized optical and optoelectronic fields and has been successfully demonstrated with polarized photodetection of in-plane anisotropic two-dimensional (2D) materials. Here, we report the anisotropic optical characterization of a group IV-V compound-2D germanium arsenic (GeAs) with anisotropic monoclinic structures. High-quality 2D GeAs crystals show the representative angle-resolved Raman property. The in-plane anisotropic optical nature of the GeAs crystal is further investigated by polarization-resolved absorption spectra (400-2000 nm) and polarization-sensitive photodetectors. From the visible to the near-infrared range, 2D GeAs nanoflakes demonstrate the distinct perpendicular optical reversal with a 75-80° angle on both the linear dichroism and polarization-sensitive photodetection. Obvious anisotropic features and the high dichroic ratio of Ipmax /Ipmin ∼ 1.49 at 520 nm and Ipmax /Ipmin ∼ 4.4 at 830 nm are achieved by the polarization-sensitive photodetection. The polarization-dependent photocurrent mapping implied that the polarized photocurrent mainly occurred at the Schottky photodiodes between electrode/GeAs interface. These experimental results are consistent with the theoretical calculation of band structure and band realignment. Besides the excellent polarization-sensitive photoresponse properties, GeAs-based photodetectors also exhibit rapid on/off response. These results demonstrate that the 2D GeAs crystals have promising potential for polarization optical applications.

Highly In-Plane Anisotropic 2D GeAs2 for Polarization-Sensitive Photodetection.

Abstract: Due to the intriguing anisotropic optical and electrical properties, low-symmetry 2D materials are attracting a lot of interest both for fundamental studies and fabricating novel electronic and optoelectronic devices. Identifying new promising low-symmetry 2D materials will be rewarding toward the evolution of nanoelectronics and nano-optoelectronics. In this work, germanium diarsenide (GeAs2 ), a group IV-V semiconductor with novel low-symmetry puckered structure, is introduced as a favorable highly anisotropic 2D material into the rapidly growing 2D family. The structural, vibrational, electrical, and optical in-plane anisotropy of GeAs2 is systematically investigated both theoretically and experimentally, combined with thickness-dependent studies. Polarization-sensitive photodetectors based on few-layer GeAs2 exhibit highly anisotropic photodetection behavior with lineally dichroic ratio up to ≈2. This work on GeAs2 will excite interests in the less exploited regime of group IV-V compounds.

Plasmonically enhanced graphene photodetector featuring 100 GBd, high-responsivity and compact size

Abstract: Graphene has shown great potentials for high-speed photodetection. Yet, the responsivities of graphene-based high-speed photodetectors are commonly limited by the weak effective absorption of atomically thin graphene. Here, we propose and experimentally demonstrate a plasmonically enhanced waveguide-integrated graphene photodetector. The device which combines a 6 micron long layer of graphene with field-enhancing nano-sized metallic structures, demonstrates a high external responsivity of 0.5 A/W and a fast photoresponse way beyond 110 GHz. The high efficiency and fast response of the device enables for the first time 100 Gbit/s PAM-2 and 100 Gbit/s PAM-4 data reception with a graphene based device. The results show the potential of graphene as a new technology for highest-speed communication applications.

Flexible and High-Performance All-2D Photodetector for Wearable Devices.

Abstract: Emerging novel applications at the forefront of innovation horizon raise new requirements including good flexibility and unprecedented properties for the photoelectronic industry. On account of diversity in transport and photoelectric properties, 2D layered materials have proven as competent building blocks toward next-generation photodetectors. Herein, an all-2D Bi2 Te3 -SnS-Bi2 Te3 photodetector is fabricated with pulsed-laser deposition. It is sensitive to broadband wavelength from ultraviolet (370 nm) to near-infrared (808 nm). In addition, it exhibits great durability to bend, with intact photoresponse after 100 bend cycles. Upon 370 nm illumination, it achieves a high responsivity of 115 A W-1 , a large external quantum efficiency of 3.9 × 104 %, and a superior detectivity of 4.1 × 1011 Jones. They are among the best figures-of-merit of state-of-the-art 2D photodetectors. The synergistic effect of SnS's strong light-matter interaction, efficient carrier separation of Bi2 Te3 -SnS interface, expedite carrier injection across Bi2 Te3 -SnS interface, and excellent carrier collection of Bi2 Te3 topological insulator electrodes accounts for the superior photodetection properties. In summary, this work depicts a facile all-in-one fabrication strategy toward a Bi2 Te3 -SnS-Bi2 Te3 photodetector. More importantly, it reveals a novel all-2D concept for construction of flexible, broadband, and high-performance photoelectronic devices by integrating 2D layered metallic electrodes and 2D layered semiconducting channels.

Nanophotonics with 2D Transition Metal Dichalcogenides

Abstract: Two-dimensional transition metal dichalcogenides (TMDCs) have recently become attractive semiconductor materials for several optoelectronic applications, such as photodetection, light harvesting, phototransistors, light-emitting diodes, and lasers. They are particularly appealing because their bandgap lies in the visible and near-IR range, and they possess strong excitonic resonances, high oscillator strengths, and valley-selective response. Coupling these materials to optical nanocavities enhances the quantum yield of exciton emission, enabling advanced quantum optics and nanophotonic devices. Here, we review state-of-the-art advances on hybrid exciton-polariton structures based on monolayer TMDCs coupled to plasmonic and dielectric nanocavities. We first generally discuss the optical properties of 2D WS2, WSe2, MoS2 and MoSe2 materials, paying special attention to their energy and photoluminescence/absorption spectra, excitonic fine structure, and to the dynamics of exciton formation and valley depolarization. We then discuss light-matter interactions in hybrid exciton-polariton structures. Finally, we focus on weak and strong coupling regimes in monolayer TMDCs-based exciton-polariton systems, envisioning research directions and future opportunities based on this novel material platform.

Wafer-Scale Fabrication of Two-Dimensional PtS2/PtSe2 Heterojunctions for Efficient and Broad band Photodetection

Abstract: The fabrication of van der Waals heterostructures mainly extends to two-dimensional (2D) materials that are exfoliated from their bulk counterparts, which is greatly limited by high-volume manufacturing. Here, we demonstrate multilayered PtS2/PtSe2 heterojunctions covering a large area on the SiO2/Si substrate with a maximum size of 2″ in diameter, offering throughputs that can meet the practical application demand. Theoretical simulation was carried out to understand the electronic properties of the PtS2/PtSe2 heterojunctions. Zero-bias photoresponse in the heterojunctions is observed under laser illumination of different wavelengths (405–2200 nm). The PtS2/PtSe2 heterojunctions exhibit broad band photoresponse and high quantum efficiency at infrared wavelengths with lower bounds for the external quantum efficiencies being 1.2% at 1064 nm, 0.2% at 1550 nm, and 0.05% at 2200 nm, and also relatively fast response time at the dozens of millisecond level. The large area, broad band 2D heterojunction photodet...

Vacuum-Ultraviolet Photodetection in Few-Layered h-BN.

Abstract: Over the past 20 years, astro and solar physicists have been working hard to develop a new-generation semiconductor-based vacuum-ultraviolet (VUV, 100-200 nm) photodetector with small size and low power consumption, to replace the traditional microchannel detection system, which is ponderous and has high energy consumption, and finally to reduce the power load and launch costs of explorer satellites. However, this expectation has hardly been achieved due to the relatively low photoresponsivity and external quantum efficiency (EQE) of the reported VUV photoconductive detectors based on traditional wide-band-gap materials and structures. Here, on the basis of few-layer h-BN, we fabricated a high-performance two-dimensional photodetector with selective response to VUV light. Typically, it has high sensitivity (EQE = 2133%, at 20 V) to the extremely weak 160 nm light (3.25 pW). This excellent photoresponsivity can be attributed to the high carrier collection efficiency and existing surface trap states of few-layer h-BN. In addition, this device can maintain a stable performance in a wide temperature range (80-580 K), which is quite favorable for application in deep space with huge temperature fluctuation.

Combining Plasmonic Hot Carrier Generation with Free Carrier Absorption for High-Performance Near-Infrared Silicon-Based Photodetection

Abstract: Plasmonic hot-carrier-based photodetectors detect light at frequencies below the semiconductor bandgap with room temperature operation and can exhibit spectrally narrowband behavior, potentially el...

Fast MoTe2 Waveguide Photodetector with High Sensitivity at Telecommunication Wavelengths

Abstract: Two-dimensional (2D) materials integrated with planar photonic elements enable a new class of electro-optical components and hold much promise for a novel 2D material integrated circuit technology. Here, we present a few-layer MoTe2 waveguide photodetector that is operable across the entire O-band of the near-infrared optical telecommunication spectral range. The device is realized in a two-terminal in-plane electrode configuration without applying external gating. It features a competitive photoresponsivity of 23 mA/W as well as a low dark current, both of which lead to a highly sensitive photodetection with a large dynamic range. Moreover, the design of the photodetector exhibits a fast photoresponse with a bandwidth approaching 1 GHz, outperforming prior TMDC-based photodetectors. Optical data experiments proved the operation of our device at data rates of 1 Gbit/s, revealing the applicability of integrating 2D materials for practical optical data communication applications.

High Speed and Stable Solution-Processed Triple Cation Perovskite Photodetectors

Abstract: Photodetectors, which can convert light signals into electrical signals, are important opto‐electronic devices in imaging, optical communication, biomedical/biological sensing, and so on. Here a solution‐processed photodetector based on the triple cation perovskite is demonstrated. The perovskite photodetectors show a high detectivity, high speed, as well as excellent environmental stability. Operating at a low voltage bias of 2 V, the photodetectors exhibit a large on/off ratio of 105, high specific detectivity of ≈1013 Jones, and a fast photoresponse with 3 dB bandwidth up to 0.82 MHz. Further analysis demonstrates that such performance originates from the modulated Schottky barrier height by illumination. The barrier suppresses dark current without any illumination, but it can be effectively lowered under illumination, thus resulting in a more efficient charge extraction and collection. The results demonstrate a great potential of triple cation perovskite in photodetection and provide a route to achieve high performance devices.

Multilayer ReS2 Photodetectors with Gate Tunability for High Responsivity and High-Speed Applications.

Abstract: Rhenium disulfide (ReS2) is an attractive candidate for photodetection applications owing to its thickness-independent direct band gap. Despite various photodetection studies using two-dimensional semiconductors, the trade-off between responsivity and response time under varying measurement conditions has not been studied in detail. This report presents a comprehensive study of the architectural, laser power and gate bias dependence of responsivity and speed in supported and suspended ReS2 phototransistors. Photocurrent scans show uniform photogeneration across the entire channel because of enhanced optical absorption and a direct band gap in multilayer ReS2. A high responsivity of 4 A W-1 (at 50 ms response time) and a low response time of 20 μs (at 4 mA W-1 responsivity) make this one of the fastest reported transition-metal dichalcogenide photodetectors. Occupancy of intrinsic (bulk ReS2) and extrinsic (ReS2/SiO2 interface) traps is modulated using gate bias to demonstrate tunability of the response time (responsivity) over 4 orders (15×) of magnitude, highlighting the versatility of these photodetectors. Differences in the trap distributions of suspended and supported channel architectures, and their occupancy under different gate biases enable switching the dominant operating mechanism between either photogating or photoconduction. Further, a new metric that captures intrinsic photodetector performance by including the trade-off between its responsivity and speed, besides normalizing for the applied bias and geometry, is proposed and benchmarked for this work.

Growth of Wafer-Scale Standing Layers of WS2 for Self-Biased High-Speed UV–Visible–NIR Optoelectronic Devices

Abstract: This work describes the wafer-scale standing growth of (002)-plane-oriented layers of WS2 and their suitability for use in self-biased broad-band high-speed photodetection. The WS2 layers are grown using large-scale sputtering, and the effects of the processing parameters such as the deposition temperature, deposition time, and sputtering power are studied. The structural, physical, chemical, optical, and electrical properties of the WS2 samples are also investigated. On the basis of the broad-band light absorption and high-speed in-plane carrier transport characteristics of the WS2 layers, a self-biased broad-band high-speed photodetector is fabricated by forming a type-II heterojunction. This WS2/Si heterojunction is sensitive to ultraviolet, visible, and near-infrared photons and shows an ultrafast photoresponse (1.1 μs) along with an excellent responsivity (4 mA/W) and a specific detectivity (∼1.5 × 1010 Jones). A comprehensive Mott–Schottky analysis is performed to evaluate the parameters of the devi...

A highly polarization sensitive antimonene photodetector with a broadband photoresponse and strong anisotropy

Abstract: Photodetectors based on two-dimensional materials have shown impressive performance including fast and broadband photoresponse and high responsivity However, their polarization sensitivity remains to be improved Here, we propose an antimonene photodetector having a strong polarization sensitivity with a broadband photoresponse, based on quantum transport calculations A robust photocurrent is generated for almost the whole visible range under small bias, and it saturates at a small bias voltage for most of the photon energies The photocurrent shows a perfect cosine dependence on the polarization angle, which originates from a second-order response to the electric field of the light This leads to a strong polarization sensitivity to the linearly polarized light with a large extinction ratio For a higher photon energy around 32 eV, a rather high extinction ratio greater than 100 can be achieved along with a larger photocurrent Moreover, there is an evident anisotropy between the armchair and zigzag directions, as the photocurrent intensity in the zigzag direction can be approximately 17 times larger than that in the armchair direction at a small bias These results suggest that antimonene is a promising candidate for anisotropic photodetection in the visible range especially for high frequency visible light

Highly Efficient Infrared Photodetection in a Gate-Controllable Van der Waals Heterojunction with Staggered Bandgap Alignment.

Abstract: In recent years, various van der Waals (vdW) materials have been used in implementing high-performance photodetectors with high photoresponsivity over a wide detection range. However, in most studies reported so far, photodetection in the infrared (IR) region has not been achieved successfully. Although several vdW materials with narrow bandgaps have been proposed for IR detection, the devices based on these materials exhibit notably low photoresponsivity under IR light illumination. Here, highly efficient near-infrared (NIR) photodetection based on the interlayer optical transition phenomenon in a vdW heterojunction structure consisting of ReS2 and ReSe2 is demonstrated. In addition, by applying the gate-control function to the two-terminal vdW heterojunction photodetector, the photoresponsivity is enhanced to 3.64 × 105 A W-1 at λ = 980 nm and 1.58 × 105 A W-1 at λ = 1310 nm. Compared to the values reported for previous vdW photodetectors, these results are the highest levels of photoresponsivity in the NIR range. The study offers a novel device platform for achieving high-performance IR photodetectors.

Subwavelength angle-sensing photodetectors inspired by directional hearing in small animals.

Abstract: Sensing the direction of sounds gives animals clear evolutionary advantage. For large animals, with an ear-to-ear spacing that exceeds audible sound wavelengths, directional sensing is simply accomplished by recognizing the intensity and time differences of a wave impinging on its two ears1. Recent research suggests that in smaller, subwavelength animals, angle sensing can instead rely on a coherent coupling of soundwaves between the two ears2–4. Inspired by this natural design, here we show a subwarvelength photodetection pixel that can measure both the intensity and incident angle of light. It relies on an electrical isolation and optical coupling of two closely spaced Si nanowires that support optical Mie resonances5–7. When these resonators scatter light into the same free-space optical modes, a non-Hermitian coupling results that affords highly sensitive angle determination. By straightforward photocurrent measurements, we can independently quantify the stored optical energy in each nanowire and relate the difference in the stored energy between the wires to the incident angle of a light wave. We exploit this effect to fabricate a subwavelength angle-sensitive pixel with angular sensitivity, δθ = 0.32°. Two Si resonators couple through a non-Hermitian interaction to sense both the intensity and the incident angle of light with subwavelength resolution.

Room-Temperature Ultrabroadband Photodetection with MoS 2 by Electronic-Structure Engineering Strategy.

Abstract: Photodetection using semiconductors is critical for capture, identification, and processing of optical information. Nowadays, broadband photodetection is limited by the underdeveloped mid-IR photodetection at room temperature (RT), primarily as a result of the large dark currents unavoidably generated by the Fermi-Dirac distribution in narrow-bandgap semiconductors, which constrains the development of some modern technologies and systems. Here, an electronic-structure strategy is proposed for designing ultrabroadband covering mid- and even far-IR photodetection materials operating at RT and a layered MoS2 is manifested with an engineered bandgap of 0.13 eV and modulated electronic state density. The sample is designed by introducing defect energy levels into layered MoS2 and its RT photodetection is demonstrated for wavelengths from 445 nm to 9.5 µm with an electronic state density-dependent peak photoresponsivity of 21.8 mA W-1 in the mid-IR region, the highest value among all known photodetectors. This material should be a promising candidate for modern optoelectronic devices and offers inspiration for the design of other optoelectronic materials.

Balanced Photodetection in One-Step Liquid-Phase-Synthesized CsPbBr3 Micro-/Nanoflake Single Crystals

Abstract: Here, we reported a low-cost and high-compatibility one-step liquid-phase synthesis method for synthesizing high-purity CsPbBr3 micro-/nanoflake single crystals. On the basis of the high-purity CsPbBr3, we further prepared a low-dimensional photodetector capable of balanced photodetection, involving both high external quantum efficiency and rapid temporal response, which is barely realized in previously reported low-dimensional photodetectors.