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Showing papers on "Responsivity published in 2016"


Journal ArticleDOI
TL;DR: Noise measurements show that such BP photodetectors are capable of sensing mid-infrared light in the picowatt range, and the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BP's moderate bandgap.
Abstract: Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for photonic applications due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid-infrared detectors at 3.39 μm with high internal gain, resulting in an external responsivity of 82 A/W. Noise measurements show that such BP photodetectors are capable of sensing mid-infrared light in the picowatt range. Moreover, the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BP’s moderate bandgap. The high photoresponse at mid-infrared wavelengths and the large dynamic bandwidth, together with its unique polarization dependent response induced by low crystalline symmetry,...

598 citations


Journal ArticleDOI
TL;DR: Optoelectronic analysis reveals that the heterojunction device is virtually blind to light illumination with wavelength longer than 280 nm, but is highly sensitive to 254 nm light with very good stability and reproducibility.
Abstract: A deep UV light photodetector is assembled by coating multilayer graphene on beta-gallium oxide (β-Ga2 O3 ) wafer. Optoelectronic analysis reveals that the heterojunction device is virtually blind to light illumination with wavelength longer than 280 nm, but is highly sensitive to 254 nm light with very good stability and reproducibility.

491 citations


Journal ArticleDOI
01 Feb 2016-Small
TL;DR: The results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.
Abstract: A graphene/n-type silicon (n-Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high-performance photodetectors. However, graphene/n-Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n-Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n-Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10(13) cm Hz(1/2) W(-1) at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n-Si heterojunction photodetectors possess high responsivity of 0.73 A W(-1) and high photo-to-dark current ratio of ≈10(7) . The current noise spectral density of the graphene/n-Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.

386 citations


Journal ArticleDOI
TL;DR: The devices show high photoresponse in a broadband spectral range with a record-high photoresponsivity of 4.3 × 10(6) A W(-1) at 300 K for the 100 nm device.
Abstract: An array of black-phosphorus photodetectors with channel lengths down to 100 nm is fabricated, and temperature-dependent photodetection measurements from 300 K down to 20 K are carried out. The devices show high photoresponse in a broadband spectral range with a record-high photoresponsivity of 4.3 × 10(6) A W(-1) at 300 K for the 100 nm device.

344 citations


Journal ArticleDOI
TL;DR: This study reports the first photodetector based on individual 2D (C4H9NH3)2PbBr4 perovskite crystals, built with the protection and top contact of graphene film, and paves the way to build high-performance optoelectronic devices based on the emerging 2D single-crystal perovkite materials.
Abstract: Two-dimensional (2D) layered hybrid perovskites of (RNH3)2PbX4 (R is an alkyl and X is a halide) have been recently synthesized and exhibited rich optical properties including fluorescence and exciton effects. However, few studies on transport and optoelectronic measurements of individual 2D perovskite crystals have been reported, presumably owing to the instability issue during electronic device fabrications. Here we report the first photodetector based on individual 2D (C4H9NH3)2PbBr4 perovskite crystals, built with the protection and top contact of graphene film. Both a high responsivity (∼2100 A/W) and extremely low dark current (∼10–10 A) are achieved with a design of interdigital graphene electrodes. Our study paves the way to build high-performance optoelectronic devices based on the emerging 2D single-crystal perovskite materials.

313 citations


Journal ArticleDOI
Shan Chen1, Changjiu Teng1, Miao Zhang1, Yingru Li1, Dan Xie1, Gaoquan Shi1 
TL;DR: A lateral photodetector based on the bilayer composite film of a perovskite and a conjugated polymer is reported that exhibits significantly enhanced responsivity in the UV-vis region and sensitive photoresponse in the near-IR (NIR) region at a low applied voltage.
Abstract: A lateral photodetector based on the bilayer composite film of a perovskite and a conjugated polymer is reported. It exhibits significantly enhanced responsivity in the UV-vis region and sensitive photoresponse in the near-IR (NIR) region at a low applied voltage. This broadband photodetector also shows excellent mechanical flexibility and improved environmental stability.

312 citations


Journal ArticleDOI
TL;DR: An on-chip integrated metal graphene–silicon plasmonic Schottky photodetector with 85 mA/W responsivity at 1.55 μm and 7% internal quantum efficiency is reported, paving the way to graphene integrated silicon photonics.
Abstract: We report an on-chip integrated metal graphene–silicon plasmonic Schottky photodetector with 85 mA/W responsivity at 1.55 μm and 7% internal quantum efficiency. This is one order of magnitude higher than metal–silicon Schottky photodetectors operated in the same conditions. At a reverse bias of 3 V, we achieve avalanche multiplication, with 0.37A/W responsivity and avalanche photogain ∼2. This paves the way to graphene integrated silicon photonics.

279 citations


Journal ArticleDOI
02 May 2016-ACS Nano
TL;DR: The successful preparation of high-quality topological insulator Bi2Se3/Si heterostructure having an atomically abrupt interface by van der Waals epitaxy growth of Bi2 Se3 films on Si wafer is reported.
Abstract: As an exotic state of quantum matter, topological insulators have promising applications in new-generation electronic and optoelectronic devices. The realization of these applications relies critically on the preparation and properties understanding of high-quality topological insulators, which however are mainly fabricated by high-cost methods like molecular beam epitaxy. We here report the successful preparation of high-quality topological insulator Bi2Se3/Si heterostructure having an atomically abrupt interface by van der Waals epitaxy growth of Bi2Se3 films on Si wafer. A simple, low-cost physical vapor deposition (PVD) method was employed to achieve the growth of the Bi2Se3 films. The Bi2Se3/Si heterostructure exhibited excellent diode characteristics with a pronounced photoresponse under light illumination. The built-in potential at the Bi2Se3/Si interface greatly facilitated the separation and transport of photogenerated carriers, enabling the photodetector to have a high light responsivity of 24.2...

276 citations


Journal ArticleDOI
14 Sep 2016-ACS Nano
TL;DR: Flexible photodetectors for visible wavelengths fabricated by stacking centimeter-scale chemical vapor deposited graphene (SLG) and single layer CVD MoS2, both wet transferred onto a flexible polyethylene terephthalate substrate make them attractive for wearable applications.
Abstract: We present flexible photodetectors (PDs) for visible wavelengths fabricated by stacking centimeter-scale chemical vapor deposited (CVD) single layer graphene (SLG) and single layer CVD MoS2, both wet transferred onto a flexible polyethylene terephthalate substrate. The operation mechanism relies on injection of photoexcited electrons from MoS2 to the SLG channel. The external responsivity is 45.5A/W and the internal 570A/W at 642 nm. This is at least 2 orders of magnitude higher than bulk-semiconductor flexible membranes. The photoconductive gain is up to 4 × 105. The photocurrent is in the 0.1–100 μA range. The devices are semitransparent, with 8% absorptance at 642 nm, and are stable upon bending to a curvature of 1.4 cm. These capabilities and the low-voltage operation (<1 V) make them attractive for wearable applications.

265 citations


Journal ArticleDOI
TL;DR: In this article, an improved chemical vapor deposition route is provided to synthesize large-size SnS2 nanosheets, the side length of which can surpass 150 μm.
Abstract: 2D SnS2 nanosheets have been attracting intensive attention as one potential candidate for the modern electronic and/or optoelectronic fields. However, the controllable large-size growth of ultrathin SnS2 nanosheets still remains a great challenge and the photodetectors based on SnS2 nanosheets suffer from low responsivity, thus hindering their further applications so far. Herein, an improved chemical vapor deposition route is provided to synthesize large-size SnS2 nanosheets, the side length of which can surpass 150 μm. Then, ultrathin SnS2 nanosheet-based phototransistors are fabricated, which achieve high photoresponsivities up to 261 A W−1 (with a fast rising time of 20 ms and a falling time of 16 ms) in air and 722 A W−1 in vacuum, respectively. Furthermore, the effects of back-gate voltage and air adsorbates on the optoelectronic properties of the SnS2 nanosheet have been systematically investigated. In addition, a high-performance flexible photodetector based on SnS2 nanosheet is also fabricated with a high responsivity of 34.6 A W−1.

262 citations


Journal ArticleDOI
TL;DR: A flexible, transparent, high-stability and ultra-broadband photodetector made using large-area and highly-crystalline WSe2 films that were prepared by pulsed-laser deposition (PLD) with great potential for practical applications in the wearable optoelectronic devices.
Abstract: Although two-dimensional (2D) materials have attracted considerable research interest for use in the development of innovative wearable optoelectronic systems, the integrated optoelectronic performance of 2D materials photodetectors, including flexibility, transparency, broadband response and stability in air, remains quite low to date. Here, we demonstrate a flexible, transparent, high-stability and ultra-broadband photodetector made using large-area and highly-crystalline WSe2 films that were prepared by pulsed-laser deposition (PLD). Benefiting from the 2D physics of WSe2 films, this device exhibits excellent average transparency of 72% in the visible range and superior photoresponse characteristics, including an ultra-broadband detection spectral range from 370 to 1064 nm, reversible photoresponsivity approaching 0.92 A W(-1), external quantum efficiency of up to 180% and a relatively fast response time of 0.9 s. The fabricated photodetector also demonstrates outstanding mechanical flexibility and durability in air. Also, because of the wide compatibility of the PLD-grown WSe2 film, we can fabricate various photodetectors on multiple flexible or rigid substrates, and all these devices will exhibit distinctive switching behavior and superior responsivity. These indicate a possible new strategy for the design and integration of flexible, transparent and broadband photodetectors based on large-area WSe2 films, with great potential for practical applications in the wearable optoelectronic devices.

Journal ArticleDOI
TL;DR: In this paper, high responsivity phototransistors based on few-layer rhenium disulfide (ReS2) are presented, where the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2.
Abstract: 2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few-layer rhenium disulfide (ReS2) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few-layer ReS2 flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications.

Journal ArticleDOI
05 Sep 2016-Small
TL;DR: A high sensitivity self-powered solar-blind photodetector is successfully constructed based on the polyaniline/MgZnO bilayer.
Abstract: A high sensitivity self-powered solar-blind photodetector is successfully constructed based on the polyaniline/MgZnO bilayer. The maximum responsivity of the photodetector is 160 μA W-1 at 250 nm under 0 V bias. The device also exhibits a high on/off ratio of ≈104 under 250 nm illumination at a relatively weak light intensity of 130 μW cm-2 without any power.

Journal ArticleDOI
TL;DR: The simple and scalable fabrication of homogeneous, large-size and transferable WS2 films with tens-of-nanometers thickness through magnetron sputtering and post annealing process paves new way towards the large scale growth of transferable high quality, uniformWS2 films for various important applications including high performance photodetectors, solar cell, photoelectrochemical cell and so on.
Abstract: The two-dimensional layered semiconducting tungsten disulfide (WS2) film exhibits great promising prospects in the photoelectrical applications because of its unique photoelectrical conversion property. Herein, in this paper, we report the simple and scalable fabrication of homogeneous, large-size and transferable WS2 films with tens-of-nanometers thickness through magnetron sputtering and post annealing process. The produced WS2 films with low resistance (4.2 kΩ) are used to fabricate broadband sensitive photodetectors in the ultraviolet to visible region. The photodetectors exhibit excellent photoresponse properties, with a high responsivity of 53.3 A/W and a high detectivity of 1.22 × 1011 Jones at 365 nm. The strategy reported paves new way towards the large scale growth of transferable high quality, uniform WS2 films for various important applications including high performance photodetectors, solar cell, photoelectrochemical cell and so on.

Journal ArticleDOI
TL;DR: In this article, β -Ga 2 O 3 /Si p-n heterojunctions are formed as a deep ultraviolet (UV) solar-blind photodetector, and the corresponding external quantum efficiency is over 1.8 × 10 5 %.

Journal ArticleDOI
TL;DR: In this paper, a systematically study on the CVD growth of continuous bilayer ReS2 film and single crystalline hexagonal ReS 2 flake, as well as their corresponding optoelectronic properties is reported.
Abstract: Rhenium disulfide (ReS2) is attracting more and more attention for its thickness-depended direct band gap. As a new appearing 2D transition metal dichalcogenide, the studies on synthesis method via chemical vapor deposition (CVD) is still rare. Here a systematically study on the CVD growth of continuous bilayer ReS2 film and single crystalline hexagonal ReS2 flake, as well as their corresponding optoelectronic properties is reported. Moreover, the growth mechanism has been proposed, accompanied with simulation study. High-performance photodetector based on ReS2 flake shows a high responsivity of 604 A·W−1, high external quantum efficiency of 1.50 × 105 %, and fast response time of 2 ms. ReS2 film-based photodetector exhibits weaker performance than the flake one; however, it still demonstrates a much faster response time (≈103 ms) than other reported CVD-grown ReS2-based photodetector (≈104–105 ms). Such good properties of ReS2 render it a promising future in 2D optoelectronics.

Journal ArticleDOI
Hao Lu1, Wei Tian1, Fengren Cao1, Yulong Ma1, Bangkai Gu1, Liang Li1 
TL;DR: In this paper, a CH3NH3PbI3-based perovskite photodetector was constructed on the flexible indium tin oxide (ITO) coated substrate even after 200 bending cycles.
Abstract: Hybrid organic–inorganic perovskites have attracted intensive interest as light absorbing materials in solid-state solar cells. Herein, we demonstrate a high-performance CH3NH3PbI3-based perovskite photodetector constructed on the flexible indium tin oxide (ITO) coated substrate even after 200 bending cycles. The as-fabricated devices show high responsivity, broad spectrum response from ultraviolet to whole visible light, long-term stability, and high on-off ratio. Particularly, atomic layer deposition technique was used to deposit the ultrathin Al2O3 film on devices, functioning as a protection layer to effectively enhance the stability and durability of perovskite photodetectors. The first all-perovskite self-powered nanosystem was successfully assembled by integrating a perovskite solar cell with a perovskite photodetector. Driven by the perovskite solar cell, the photodetector exhibits fast and stable response to illuminated light at a low working voltage less than 1.0 V. This stable integrated nanosystem has promising applications in which photodetectors can work in harsh environments without external power sources.

Journal ArticleDOI
TL;DR: It is demonstrated that it is possible to engineer a state-of-the-art organic photodetector approaching the performances of Si-based photodiodes in terms of dark current, responsivity and detectivity.
Abstract: Printed organic photodetectors can transform plastic, paper or glass into smart surfaces. This innovative technology is now growing exponentially due to the strong demand in human-machine interfaces. To date, only niche markets are targeted since organic sensors still present reduced performances in comparison with their inorganic counterparts. Here we demonstrate that it is possible to engineer a state-of-the-art organic photodetector approaching the performances of Si-based photodiodes in terms of dark current, responsivity and detectivity. Only three solution-processed layers and two low-temperature annealing steps are needed to achieve the performance that is significantly better than most of the organic photodetectors reported so far. We also perform a long-term ageing study. Lifetimes of over 14,000 hours under continuous operation are more than promising and demonstrate that organic photodetectors can reach a competitive level of stability for successful commercialization of this new and promising technology.

Journal ArticleDOI
01 Feb 2016-Small
TL;DR: The findings suggest that the multilayered MoS2 /Si homotype heterojunction have great potential application in the field of visible-near-infrared detection and might be used as elements for construction of high-speed integrated optoelectronic sensor circuitry.
Abstract: c2D transition metal dichalcogenides (TMDCs)-based heterostructures have been demonstrated to achieve superior light absorption and photovoltaic effects theoretically and experimentally, making them extremely attractive for realizing optoelectronic devices. In this work, a vertical multilayered n-MoS2/n-silicon homotype heterojunction is fabricated, which takes advantage of multilayered MoS2 grown in situ directly on plane silicon. Electrical characterization reveals that the resultant device exhibits high sensitivity to visible-near-infrared light with responsivity up to 11.9 A W(-1). Notably, the photodetector shows high-speed response time of ≈ 30.5 µs/71.6 µs and capability to work under higher pulsed light irradiation approaching 100 kHz. The high response speed could be attributed to a good quality of the multilayer MoS2 , as well as in situ device fabrication process. These findings suggest that the multilayered MoS2 /Si homotype heterojunction have great potential application in the field of visible-near-infrared detection and might be used as elements for construction of high-speed integrated optoelectronic sensor circuitry.

Journal ArticleDOI
TL;DR: A 67 GHz bandwidth silicon-contacted germanium waveguide p-i-n photodetector operating at -1 V with 6.8 fF capacitance is demonstrated with clear open eye diagrams in both the C-band and O-band.
Abstract: We demonstrate a 67 GHz bandwidth silicon-contacted germanium waveguide p-i-n photodetector operating at −1 V with 6.8 fF capacitance. The dark current is below 4 nA. The responsivity is 0.74 A/W at 1550 nm and 0.93 A/W at 1310 nm wavelength. 56 Gbps on-off-keying data reception is demonstrated with clear open eye diagrams in both the C-band and O-band.

Journal ArticleDOI
TL;DR: The interference between surface plasmon polaritons and the incident wave introduces new functionalities, such as light flux attraction or repulsion from the contact edges, enabling the tailored design of the photodetector's spectral response.
Abstract: The combination of plasmonic nanoparticles and graphene enhances the responsivity and spectral selectivity of graphene-based photodetectors. However, the small area of the metal–graphene junction, where the induced electron–hole pairs separate, limits the photoactive region to submicron length scales. Here, we couple graphene with a plasmonic grating and exploit the resulting surface plasmon polaritons to deliver the collected photons to the junction region of a metal–graphene–metal photodetector. This gives a 400% enhancement of responsivity and a 1000% increase in photoactive length, combined with tunable spectral selectivity. The interference between surface plasmon polaritons and the incident wave introduces new functionalities, such as light flux attraction or repulsion from the contact edges, enabling the tailored design of the photodetector’s spectral response. This architecture can also be used for surface plasmon biosensing with direct-electric-redout, eliminating the need of bulky optics.

Journal ArticleDOI
01 Sep 2016-Small
TL;DR: The Se dope induces over 20-fold enhancement of responsivity (R) for BP-based 2D photodetectors, resulting in a high R and external quantum efficiency of 15.33 A W-1 and 2993%, respectively.
Abstract: Se-doped black phosphorus (BP) crystal, in centimeter scale, is synthesized by a scalable gas-phase growth method under mild conditions. The Se-doped BP exhibits high quality with excellent electrical properties. The Se dope induces over 20-fold enhancement of responsivity (R) for BP-based 2D photodetectors, resulting in a high R and external quantum efficiency of 15.33 A W-1 and 2993%, respectively.

Journal ArticleDOI
TL;DR: In this paper, benzyl viologen (BV) was used as an effective electron dopant to part of the area of a (p-type) few-layer BP flake and achieved an ambient stable, in-plane P-N junction.

Journal ArticleDOI
TL;DR: The use of a few-layer graphene membrane as a squeeze-film pressure sensor shows a reproducible response and no hysteresis, and the measured responsivity is a factor 45 higher than state-of-the-art MEMS-based squeeze- film pressure sensors while using a 25 times smaller membrane area.
Abstract: The operating principle of squeeze-film pressure sensors is based on the pressure dependence of a membrane’s resonance frequency, caused by the compression of the surrounding gas which changes the resonator stiffness. To realize such sensors, not only strong and flexible membranes are required, but also minimization of the membrane’s mass is essential to maximize responsivity. Here, we demonstrate the use of a few-layer graphene membrane as a squeeze-film pressure sensor. A clear pressure dependence of the membrane’s resonant frequency is observed, with a frequency shift of 4 MHz between 8 and 1000 mbar. The sensor shows a reproducible response and no hysteresis. The measured responsivity of the device is 9000 Hz/mbar, which is a factor 45 higher than state-of-the-art MEMS-based squeeze-film pressure sensors while using a 25 times smaller membrane area.

Journal ArticleDOI
TL;DR: In this paper, a self-powered photodetector based on a ZnO/CH3NH3PbI3 heterojunction and a MoO3 hole-transport layer is reported.
Abstract: Here we report a self-powered photodetector based on a ZnO/CH3NH3PbI3 heterojunction and a MoO3 hole-transport layer. The organolead iodide perovskite photodetector is sensitive to broadband wavelengths from the ultraviolet light to the entire visible light region (250–800 nm), showing a high photo-responsivity of 24.3 A W−1 and a high detectivity value of 3.56 × 1014 cm Hz1/2 W−1 at 500 nm without external bias voltage. Meanwhile, we found that the photodetective performances are closely related to the thickness of the MoO3 layer, which acts as a hole-transport layer and an electron-blocking layer and can effectively decrease the recombination of holes and electrons. Additionally, the as-fabricated photodetector exhibits good stability and only 9.3% photoelectric response current decay after a 3-month illumination test. The high detectivity and responsivity of such a ZnO nanorod/perovskite heterojunction are clearly demonstrated and should be widely applicable to other photoelectric detection devices.

Journal ArticleDOI
TL;DR: In this paper, the transport mechanism of individual Zn2GeO4 nanowires is discussed in the frame of the small polaron theory, which reveals a high gain under high energy electron beam.
Abstract: Solar-blind deep ultraviolet (DUV) photodetectors have been a hot topic in recent years because of their wide commercial and military applications. A wide bandgap (4.68 eV) of ternary oxide Zn2GeO4 makes it an ideal material for the solar-blind DUV detection. Unfortunately, the sensing performance of previously reported photodetectors based on Zn2GeO4 nanowires has been unsatisfactory for practical applications, because they suffer from long response and decay times, low responsivity, and quantum efficiency. Here, high-performance solar-blind DUV photodetectors are developed based on individual single-crystalline Zn2GeO4 nanowires. The transport mechanism is discussed in the frame of the small polaron theory. In situ electrical characterization of individual Zn2GeO4 nanowires reveals a high gain under high energy electron beam. The devices demonstrate outstanding solar-blind light sensing performances: a responsivity of 5.11 × 103 A W−1, external quantum efficiency of 2.45 × 106%, detectivity of ≈2.91 × 1011 Jones, τrise ≈ 10 ms, and τdecay ≈ 13 ms, which are superior to all reported Zn2GeO4 and other ternary oxide nanowire photodetectors. These results render the Zn2GeO4 nanowires particularly valuable for optoelectronic devices.

Journal ArticleDOI
20 Oct 2016
TL;DR: In this article, the authors proposed a Graphene-based photodetectors with an interfacial gating mechanism for weak signal detection, which is capable of detecting a signal of < 1 nW with a responsivity of ∼ 1000 nW.
Abstract: Graphene-based photodetectors have recently received much attention for their potential to detect weak signals and their short response time, both of which are crucial in applications such as optical positioning, remote sensing, and biomedical imaging. However, existing devices for detecting weak signals are limited by the current photogating mechanism, so the price for achieving ultrahigh sensitivity is to sacrifice response time. In this work, we bridge the gap between ultrafast response and ultrahigh sensitivity by employing a graphene/SiO2/lightly doped Si architecture with an interfacial gating mechanism. Our device is capable of detecting a signal of <1 nW (with a responsivity of ∼1000 AW−1), and the spectral response extends from the visible to near-IR. More important, the photoresponse time of our device has been pushed to ∼400 ns. The current device structure does not need a complicated fabrication process and is fully compatible with silicon technology. This work not only will open up a route to graphene-based high-performance optoelectronic devices but also has great potential for ultrafast weak signal detection.

Journal ArticleDOI
TL;DR: In this paper, a self-trapped hole formation near the Schottky barrier in reverse bias was found to produce photoconductive gain, which can explain the operation of a variety of β-Ga2O3 photodetectors.
Abstract: Solar-blind photodetection and photoconductive gain >50 corresponding to a responsivity >8 A/W were observed for β-Ga2O3 Schottky photodiodes. The origin of photoconductive gain was investigated. Current-voltage characteristics of the diodes did not indicate avalanche breakdown, which excludes carrier multiplication by impact ionization as the source for gain. However, photocapacitance measurements indicated a mechanism for hole localization for above-band gap illumination, suggesting self-trapped hole formation. Comparison of photoconductivity and photocapacitance spectra indicated that self-trapped hole formation coincides with the strong photoconductive gain. It is concluded that self-trapped hole formation near the Schottky diode lowers the effective Schottky barrier in reverse bias, producing photoconductive gain. Ascribing photoconductive gain to an inherent property like self-trapping of holes can explain the operation of a variety of β-Ga2O3 photodetectors.

Journal ArticleDOI
TL;DR: Fabricated n-MoS2/p-Si 0D/3D heterojunctions exhibiting excellent rectification behavior have been studied for light emission in the forward bias and photodetection in the reverse bias and are found to be superior to the reported results on large areaPhotodetector devices fabricated using two dimensional materials.
Abstract: Silicon compatible wafer scale MoS2 heterojunctions are reported for the first time using colloidal quantum dots. Size dependent direct band gap emission of MoS2 dots are presented at room temperature. The temporal stability and decay dynamics of excited charge carriers in MoS2 quantum dots have been studied using time correlated single photon counting spectroscopy technique. Fabricated n-MoS2/p-Si 0D/3D heterojunctions exhibiting excellent rectification behavior have been studied for light emission in the forward bias and photodetection in the reverse bias. The electroluminescences with white light emission spectra in the range of 450–800 nm are found to be stable in the temperature range of 10–350 K. Size dependent spectral responsivity and detectivity of the heterojunction devices have been studied. The peak responsivity and detectivity of the fabricated heterojunction detector are estimated to be ~0.85 A/W and ~8 × 1011 Jones, respectively at an applied bias of −2 V for MoS2 QDs of 2 nm mean diameter. The above values are found to be superior to the reported results on large area photodetector devices fabricated using two dimensional materials.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated the potential of WS2 for photodetectors by passivating SiO2 substrates with layered Bi2Te3, a representative three dimensional topological insulator.
Abstract: Transition metal dichalcogenides (TMDs) manifest excellent phonon-limited mobility and strong light–matter interaction, which, however, conflict with the long response time and low responsivity of TMD-based photodetectors. The extreme susceptibility of TMDs' electronic qualities to the large density of unscreened disturbances from the SiO2 substrate accounts for such inconformity. Here, we evaluated the potential of WS2 for photodetectors by passivating SiO2 substrates with layered Bi2Te3, a representative three dimensional topological insulator. Comparative photoswitching measurements of the WS2/Bi2Te3 photodetector demonstrated its stable and broadband photoresponse from 370 to 1550 nm. Meanwhile, WS2 and Bi2Te3 allied a high responsivity of 30.7 A W−1, a pronounced detectivity of 2.3 × 1011 cm Hz1/2 W−1 as well as a short response time of 20 ms, which make the device stand out among previously reported WS2 photodetectors. In fact, the responsivity and detectivity are comparable to those of state-of-the-art commercial Si and Ge photodetectors (R ∼ 0.5 to 0.85 A W−1, D* ∼ 3 × 1011 to 3 × 1012 cm Hz1/2 W−1), suggesting its great potential for practical applications. In addition, we also established that the excellent device performance is attributed to the synergy of the passivation of the SiO2 substrate, efficient carrier separation at the WS2/Bi2Te3 heterointerface and excellent carrier transport along the time-reversal-symmetry protected surface channel of Bi2Te3. In summary, these findings suggest that the WS2/Bi2Te3 photodetector will launch a significant advance in next-generation photodetection. Moreover, the interface engineering strategy depicts a universal scenario for development of TMD devices in the future.