Showing papers on "Photodetection published in 2015"
TL;DR: In this paper, a hybrid perovskite single-crystal photodetector with a very narrow spectral response with a full width at half-maximum of <20 nm was presented.
Abstract: Organolead trihalide perovskite is an emerging low-cost, solution-processable material with a tunable bandgap from the violet to near-infrared, which has attracted a great deal of interest for applications in high-performance optoelectronic devices. Here, we present hybrid perovskite single-crystal photodetectors that have a very narrow spectral response with a full-width at half-maximum of <20 nm. The response spectra are continuously tuned from blue to red by changing the halide composition and thus the bandgap of the single crystals synthesized by solution processes. The narrowband photodetection can be explained by the strong surface-charge recombination of the excess carriers close to the crystal surfaces generated by short-wavelength light. The excess carriers generated by below-bandgap excitation locate away from the surfaces and can be much more efficiently collected by the electrodes, assisted by the applied electric field. This provides a new design paradigm for a narrowband photodetector with broad applications where background noise emission needs to be suppressed. Perovskite-based devices typically exhibit broadband spectral responses. Here narrowband (< 20 nm FWHM) response is achieved for a photodetector application.
1,133 citations
TL;DR: A broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750‽nm is demonstrated and might provide new functionalities in novel optical and optoelectronic device applications.
Abstract: The ability to detect light over a broad spectral range is central to practical optoelectronic applications and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and MoS2. However, polarization sensitivity within such a photodetector remains elusive. Here, we demonstrate a broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750 nm. The polarization sensitivity is due to the strong intrinsic linear dichroism, which arises from the in-plane optical anisotropy of this material. In this transistor geometry, a perpendicular built-in electric field induced by gating can spatially separate the photogenerated electrons and holes in the channel, effectively reducing their recombination rate and thus enhancing the performance for linear dichroism photodetection. The use of anisotropic layered black phosphorus in polarization-sensitive photodetection might provide new functionalities in novel optical and optoelectronic device applications. The anisotropic optical properties of black phosphorus can be exploited to fabricate photodetectors with linear dichroism operating over a broad spectral range.
973 citations
TL;DR: In this paper, the first material-tailoring of perovskite/spiro-OMeTAD junction-based photodiodes toward applications in photodetection was reported.
Abstract: Organometallic halide perovskites are a class of solution-processed semiconductors exhibiting remarkable optoelectronic properties. They have seen rapid strides toward enabling efficient third-generation solar cell technologies. Here, we report the first material-tailoring of TiO2/perovskite/spiro-OMeTAD junction-based photodiodes toward applications in photodetection, a field in need of fast, sensitive, low-cost, spectrally tunable materials that offer facile integration across a broad range of substrates. We report photodetection that exhibits 1 μs temporal response, and we showcase stable operation in the detection of over 7 billion transient light pulses through a continuous pulsed-illumination period. The perovskite diode photodetector has a peak responsivity approaching 0.4 A W–1 at 600 nm wavelength, which is superior to red light detection in crystalline silicon photodiodes used in commercial image sensors. Only by developing a composite Al2O3/PCBM front contact interface layer were we able to sta...
275 citations
TL;DR: P pulsed-laser deposition is introduced to prepare multilayered WS2 films and it is stressed that the PLD-grown WS2 film may constitute a new paradigm for the next-generation stable, broadband and highly-responsive photodetectors.
Abstract: The progress in the field of graphene has aroused a renaissance of keen research interest in layered transition metal dichalcogenides (TMDs). Tungsten disulfide (WS2), a typical TMD with favorable semiconducting band gap and strong light-matter interaction, exhibits great potential for highly-responsive photodetection. However, WS2-based photodetection is currently unsatisfactory due to the low optical absorption (2%-10%) and poor carrier mobility (0.01-0.91 cm(2) V(-1) s(-1)) of the thin WS2 layers grown by chemical vapor deposition (CVD). Here, we introduce pulsed-laser deposition (PLD) to prepare multilayered WS2 films. Large-area WS2 films of the magnitude of cm(2) are achieved. Comparative measurements of a WS2-based photoresistor demonstrate its stable broadband photoresponse from 370 to 1064 nm, the broadest range demonstrated in WS2 photodetectors. Benefiting from the large optical absorbance (40%-85%) and high carrier mobility (31 cm(2) V(-1) s(-1)), the responsivity of the device approaches a high value of 0.51 A W(-1) in an ambient environment. Such a performance far surpasses the CVD-grown WS2-based photodetectors (μA W(-1)). In a vacuum environment, the responsivity is further enhanced to 0.70 A W(-1) along with an external quantum efficiency of 137% and a photodetectivity of 2.7 × 10(9) cm Hz(1/2) W(-1). These findings stress that the PLD-grown WS2 film may constitute a new paradigm for the next-generation stable, broadband and highly-responsive photodetectors.
256 citations
TL;DR: The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat and the spectral response is examined and finds a constant spectral responsivity of between 500 and 1,500 nm, consistent with efficient electron heating.
Abstract: Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies have addressed the general operation of graphene-based photothermoelectric devices and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster timescale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 fs. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 fs laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity of between 500 and 1,500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.
249 citations
TL;DR: In this article, a hybrid photodetector that consists of monolayer graphene covered with a thin layer of dispersive organolead halide perovskite (CH3NH3PbBr2I) islands was demonstrated.
Abstract: Graphene is an attractive optoelectronic material for light detection because of its broadband light absorption and fast response time. However, the relatively low absorption cross-section, fast recombination rate, and the absence of gain mechanism have limited the responsivity of pure graphene-based phototransistor to ≈10−2 A W−1. In this work, a photoconductive gain of ≈109 electrons per photon and a responsivity of ≈6.0 × 105 A W−1 are demonstrated in a hybrid photodetector that consists of monolayer graphene covered with a thin layer of dispersive organolead halide perovskite (CH3NH3PbBr2I) islands. The unprecedented performance is attributed to the effective charge transfer and photogating effect, which were evidenced by photoluminescence quenching, time-resolved photoluminescence decay, scanning near-field optical microscopy, and photocurrent mapping. Unlike previous report which used perovskite bulk thin film, the perovskite islands have low bulk recombination rate of photogenerated carriers. The device also shows broad photodetection spectral range from ultraviolet to visible (250–700 nm), affording new opportunities for scalable UV detectors and imaging sensors.
239 citations
TL;DR: It is demonstrated that TI-based heterostructures hold great promise for addressing the long lasting predicament of stable room-temperature high-performance broadband photodetectors.
Abstract: Broadband photodetection is central to various technological applications including imaging, sensing and optical communications. On account of their Dirac-like surface state, Topological insulators (TIs) are theoretically predicted to be promising candidate materials for broadband photodetection from the infrared to the terahertz. Here, we report a vertically-constructed ultra-broadband photodetector based on a TI Bi2Te3–Si heterostructure. The device demonstrated room-temperature photodetection from the ultraviolet (370.6 nm) to terahertz (118 μm) with good reproducibility. Under bias conditions, the visible responsivity reaches ca. 1 A W−1 and the response time is better than 100 ms. As a self-powered photodetector, it exhibits extremely high photosensitivity approaching 7.5 × 105 cm2 W−1, and decent detectivity as high as 2.5 × 1011 cm Hz1/2 W−1. In addition, such a prototype device without any encapsulation suffers no obvious degradation after long-time exposure to air, high-energy UV illumination and acidic treatment. In summary, we demonstrate that TI-based heterostructures hold great promise for addressing the long lasting predicament of stable room-temperature high-performance broadband photodetectors.
200 citations
TL;DR: An on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride that enables optical on- chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers.
Abstract: Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation These optoelectronic capabilities can augment complementary metal–oxide–semiconductor (CMOS) devices for high-speed and low-power optical interconnects Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 036 A/W and high-speed operation with a 3 dB cutoff at 42 GHz From photocurrent measurements as a function of the top-gate and source-drain voltages, we conclude that the photoresponse is consistent with hot electron mediated effects At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron–phonon supercollision cooling This nonlinear photore
193 citations
TL;DR: A method for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection is demonstrated.
Abstract: The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 μm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.
190 citations
TL;DR: Sub-bandgap photocurrent originating from the injection of hot electrons into MoS2 as well as photoamplification that yields a photogain of 10(5) results in a photoresponsivity of 5.2 A/W at 1070 nm, which is far above similar silicon-based hot electron photodetectors in which no photo amplification is present.
Abstract: Recently, there has been much interest in the extraction of hot electrons generated from surface plasmon decay, as this process can be used to achieve additional bandwidth for both photodetectors and photovoltaics. Hot electrons are typically injected into semiconductors over a Schottky barrier between the metal and semiconductor, enabling generation of photocurrent with below bandgap photon illumination. As a two-dimensional semiconductor single and few layer molybdenum disulfide (MoS2) has been demonstrated to exhibit internal photogain and therefore becomes an attractive hot electron acceptor. Here, we investigate hot electron-based photodetection in a device consisting of bilayer MoS2 integrated with a plasmonic antenna array. We demonstrate sub-bandgap photocurrent originating from the injection of hot electrons into MoS2 as well as photoamplification that yields a photogain of 105. The large photogain results in a photoresponsivity of 5.2 A/W at 1070 nm, which is far above similar silicon-based hot ...
189 citations
TL;DR: A photoresponsivity of approximately 104 AW−1 and a photogain of approximately 107 electrons per photon is demonstrated in an n-n heterostructure photodetector that consists of a multilayer MoS2 thin film covered with a thin layer of graphene quantum dots (GQDs).
Abstract: Molybdenum disulphide (MoS2), which is a typical semiconductor from the family of layered transition metal dichalcogenides (TMDs), is an attractive material for optoelectronic and photodetection applications because of its tunable bandgap and high quantum luminescence efficiency. Although a high photoresponsivity of 880–2000 AW−1 and photogain up to 5000 have been demonstrated in MoS2-based photodetectors, the light absorption and gain mechanisms are two fundamental issues preventing these materials from further improvement. In addition, it is still debated whether monolayer or multilayer MoS2 could deliver better performance. Here, we demonstrate a photoresponsivity of approximately 104 AW−1 and a photogain of approximately 107 electrons per photon in an n-n heterostructure photodetector that consists of a multilayer MoS2 thin film covered with a thin layer of graphene quantum dots (GQDs). The enhanced light-matter interaction results from effective charge transfer and the re-absorption of photons, leading to enhanced light absorption and the creation of electron-hole pairs. It is feasible to scale up the device and obtain a fast response, thus making it one step closer to practical applications.
TL;DR: Coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal is demonstrated, demonstrating their potential for on-chip scalable quantum light–matter interfaces.
Abstract: Quantum light–matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent ^4I_(9/2)–^4F_(3/2) optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T_2~100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light–matter interfaces.
TL;DR: Using two-pulse photovoltage correlation technique, it is shown that monolayer molybdenum disulfide photodetector can have intrinsic response times as short as 3 ps implyingPhotodetection bandwidths as wide as 300 GHz.
Abstract: The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications. In this work, using two-pulse photovoltage correlation technique, we show that monolayer molybdenum disulfide photodetector can have intrinsic response times as short as 3 ps implying photodetection bandwidths as wide as 300 GHz. The fast photodetector response is a result of the short electron-hole and exciton lifetimes in this material. Recombination of photoexcited carriers in most two-dimensional metal dichalcogenides is dominated by nonradiative processes, most notable among which is Auger scattering. The fast response time, and the ease of fabrication of these devices, make them interesting for low-cost ultrafast optical communication links.
TL;DR: The observed unique PD characteristics prove to be dominated by the tunneling of charge carriers through the energy states in GQDs, based on bias-dependent variations of the band profiles, resulting in novel dark current and PC behaviors.
Abstract: Graphene quantum dots (GQDs) have received much attention due to their novel phenomena of charge transport and light absorption/emission. The optical transitions are known to be available up to ~6 eV in GQDs, especially useful for ultraviolet (UV) photodetectors (PDs). Thus, the demonstration of photodetection gain with GQDs would be the basis for a plenty of applications not only as a single-function device in detecting optical signals but also a key component in the optoelectronic integrated circuits. Here, we firstly report high-efficient photocurrent (PC) behaviors of PDs consisting of multiple-layer GQDs sandwiched between graphene sheets. High detectivity (>1011 cm Hz1/2/W) and responsivity (0.2 ~ 0.5 A/W) are achieved in the broad spectral range from UV to near infrared. The observed unique PD characteristics prove to be dominated by the tunneling of charge carriers through the energy states in GQDs, based on bias-dependent variations of the band profiles, resulting in novel dark current and PC behaviors.
TL;DR: It is shown that the excitation of localized plasmons in doped, nanostructured graphene can enhance optical absorption in its surrounding medium including both bulky and two-dimensional materials by tens of times, which may lead to a new generation of photodetectors with high efficiency and tunable spectral selectivity in the mid-infrared and THz ranges.
Abstract: Plasmonics can be used to improve absorption in optoelectronic devices and has been intensively studied for solar cells and photodetectors. Graphene has recently emerged as a powerful plasmonic material. It shows significantly less loss compared to traditional plasmonic materials such as gold and silver and its plasmons can be tuned by changing the Fermi energy with chemical or electrical doping. Here we propose the use of graphene plasmonics for light trapping in optoelectronic devices and show that the excitation of localized plasmons in doped, nanostructured graphene can enhance optical absorption in its surrounding medium including both bulky and two-dimensional materials by tens of times, which may lead to a new generation of photodetectors with high efficiency and tunable spectral selectivity in the mid-infrared and THz ranges.
TL;DR: The proposed photodetector with the capacity to store a photonic signal in memory represents a significant step toward the use of graphene in optoelectronic devices.
Abstract: The advantages of graphene photodetectors were utilized to design a new multifunctional graphene optoelectronic device. Organic semiconductors, gold nanoparticles (AuNPs), and graphene were combined to fabricate a photodetecting device with a nonvolatile memory function for storing photonic signals. A pentacene organic semiconductor acted as a light absorption layer in the device and provided a high hole photocurrent to the graphene channel. The AuNPs, positioned between the tunneling and blocking dielectric layers, acted as both a charge trap layer and a plasmonic light scatterer, which enable storing of the information about the incident light. The proposed pentacene-graphene-AuNP hybrid photodetector not only performed well as a photodetector in the visible light range, it also was able to store the photonic signal in the form of persistent current. The good photodetection performance resulted from the plasmonics-enabled enhancement of the optical absorption and from the photogating mechanisms in the p...
TL;DR: A large area terahertz detector utilizing a tunable plasmonic resonance in subwavelength graphene microribbons on SiC(0001) to increase the absorption efficiency is reported.
Abstract: We report a large area terahertz detector utilizing a tunable plasmonic resonance in subwavelength graphene microribbons on SiC(0001) to increase the absorption efficiency. By tailoring the orientation of the graphene ribbons with respect to an array of subwavelength bimetallic electrodes, we achieve a condition in which the plasmonic mode can be efficiently excited by an incident wave polarized perpendicular to the electrode array, while the resulting photothermal voltage can be observed between the outermost electrodes.
TL;DR: In this paper, the photon blockade effect with a single quantum dot coupled to a nanocavity was investigated and the second-order correlation function at zero time delay g(2) was reduced by two orders of magnitude.
Abstract: We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay g(2)(0) in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing.
TL;DR: The photovoltaic response of thin films of HgTe colloidal quantum dots in the 3-5μm range was observed in this paper, with no applied bias, internal quantum efficiency exceeding 40%, specific detectivity above 1010 Jones and microseconds response times at 140
Abstract: The photovoltaic response of thin films of HgTe colloidal quantum dots in the 3–5 μm range is observed. With no applied bias, internal quantum efficiency exceeding 40%, specific detectivity above 1010 Jones and microseconds response times are obtained at 140 K. The cooled devices detect the ambient thermal radiation. A detector with 5.25 μm cut-off achieves Background Limited Infrared Photodetection at 90 K.
TL;DR: In this article, the quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that with a classical optical readout in this configuration.
Abstract: Surface plasmon resonance (SPR) sensors can reach the quantum noise limit of the optical readout field in various configurations. We demonstrate that two-mode intensity squeezed states produce a further enhancement in sensitivity compared with a classical optical readout when the quantum noise is used to transduce an SPR sensor signal in the Kretschmann configuration. The quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that with a classical optical readout in this configuration. Furthermore, the theoretical potential of this technique points to resolving particle concentrations with more accuracy than is possible via classical approaches to optical transduction.
Journal Article•
TL;DR: In this paper, a quasi-3D large-area plasmonic crystals (PC) was used for hot-electron photodetection, with a tunable response across the visible and near-infrared.
Abstract: In view of their exciting optoelectronic light–matter interaction properties, plasmonic–hot-electron devices have attracted significant attention during the last few years as a novel route for photodetection and light-energy harvesting. Herein we report the use of quasi-3D large-area plasmonic crystals (PC) for hot-electron photodetection, with a tunable response across the visible and near-infrared. The strong interplay between the different PC modes gives access to intense electric fields and hot-carrier generation confined to the metal–semiconductor interface, maximizing injection efficiencies with responsivities up to 70 mA/W. Our approach, compatible with large-scale manufacturing, paves the way for the practical implementation of plasmonic–hot-electron optoelectronic devices.
TL;DR: These findings show that the polycrystalline TI Bi2Te3 film working as a multifunctional photodetector can not only detect the light intensity, but also measure the polarization state of the incident light, which is remarkably different from conventionalPhotodetectors that usually only detectThe light intensity.
Abstract: Three dimensional Z2 Topological insulator (TI) is an unconventional phase of quantum matter possessing insulating bulk state as well as time-reversal symmetry-protected Dirac-like surface state, which is demonstrated by extensive experiments based on surface sensitive detection techniques. This intriguing gapless surface state is theoretically predicted to exhibit many exotic phenomena when interacting with light, and some of them have been observed. Herein, we report the first experimental observation of novel polarization dependent photocurrent of photodetectors based on the TI Bi2Te3 film under irradiation of linearly polarized light. This photocurrent is linearly dependent on both the light intensity and the applied bias voltage. To pursue the physical origin of the polarization dependent photocurrent, we establish the basic TI surface state model to treat the light irradiation as a perturbation, and we adopt the Boltzmann equation to calculate the photocurrent. It turns out that the theoretical results are in nice qualitative agreement with the experiment. These findings show that the polycrystalline TI Bi2Te3 film working as a multifunctional photodetector can not only detect the light intensity, but also measure the polarization state of the incident light, which is remarkably different from conventional photodetectors that usually only detect the light intensity.
TL;DR: Graphene with gold oxide (AuOx), a transparent and high-work-function electrode material, is combined to achieve a high-efficient, low-bias, large-area, flexible, transparent, broadband, and bifacial-operable photodetector that exhibits great flexibility and stability.
Abstract: In this study, we combine graphene with gold oxide (AuOx), a transparent and high-work-function electrode material, to achieve a high-efficient, low-bias, large-area, flexible, transparent, broadband, and bifacial-operable photodetector. The photodetector operates through hot electrons being generated in the graphene and charge separation occurring at the AuOx–graphene heterojunction. The large-area graphene covering the AuOx electrode efficiently prevented reduction of its surface; it also acted as a square-centimeter-scale active area for light harvesting and photodetection. Our graphene/AuOx photodetector displays high responsivity under low-intensity light illumination, demonstrating picowatt sensitivity in the ultraviolet regime and nanowatt sensitivity in the infrared regime for optical telecommunication. In addition, this photodetector not only exhibited broadband (from UV to IR) high responsivity—3300 A W–1 at 310 nm (UV), 58 A W–1 at 500 nm (visible), and 9 A W–1 at 1550 nm (IR)—but also required...
TL;DR: In this paper, a broad band photodetector is demonstrated that is based on II-VI binary CdSe/ZnTe core/shell nanowire arrays, in which photoderetection is greatly enhanced by the piezo-phototronic effect.
Abstract: The piezo-phototronic effect is of immense importance for improving the performance of optoelectronic nanodevices. This is accomplished by tuning the charge carrier generation, separation, and transport under the influence of the inner piezopotential. In this paper, a broad band photodetector is demonstrated that is based on II-VI binary CdSe/ZnTe core/shell nanowire arrays, in which photodetection is greatly enhanced by the piezo-phototronic effect. The photodetector performance under UV (385 nm), blue (465 nm), and green (520 nm) illumination infers a saturation free response with an intensity variation near two orders of magnitude, where the peak photocurrent (125 μA) is two orders higher at 0.25 kilogram force (kgf) compared to no load (0.71 μA). The resulting (%) responsivity changed by four orders of magnitude. The significant increase in responsivity is believed to arise from: 1) the piezo-phototronic effect induced by a change in the Schottky barrier height at the Ag–ZnTe junction, and in the type-II band alignment at the CdSe–ZnTe interfaces, in conjugation with 2) a small lattice mismatch between the CdSe and ZnTe epitaxial layers, which lead to reduced charge carrier recombination. This work thus extends the piezo-phototronic effect to a group II-VI binary semiconductor heterostructure and demonstrates the importance of the epitaxial interface in a core/shell nanowire photodetector.
20 Feb 2015
TL;DR: In this paper, it was shown that the excess timing noise in the photodetection of a periodic train of ultrashort optical pulses behaves as flicker noise (1/f) with amplitude of 4 Ã as/√Hz at 1 Ã offset.
Abstract: The most frequency-stable sources of electromagnetic radiation are produced optically, and optical frequency combs provide the means for high-fidelity frequency transfer across hundreds of terahertz and into the microwave domain. A critical step in this photonic-based synthesis of microwave signals is the optical-to-electrical conversion process. Here, we show that attosecond (as) timing stability can be preserved across the opto-electronic interface of a photodiode, despite an intrinsic temporal response that is more than six orders of magnitude slower. The excess timing noise in the photodetection of a periodic train of ultrashort optical pulses behaves as flicker noise (1/f) with amplitude of 4 as/√Hz at 1 Hz offset. The corresponding fractional frequency fluctuations are 1.4×10−17 at 1 s and 5.5×10−20 at 1000 s. These results demonstrate that direct photodetection, as part of frequency-comb-based microwave synthesis, can support the timing performance of the best optical frequency standards, and thereby opens the possibility for generating microwave signals with significantly better stability than any existing source.
Journal Article•
TL;DR: Zhu et al. as mentioned in this paper proposed a general approach to achieve angle-selective perfect light absorption in 2D materials by placing large-area single-layer graphene on a structure consisting of a chalcogenide layer atop a mirror and achieving a total absorption of 77.6% in the mid-infrared wavelength range.
Abstract: Two-dimensional (2D) materials have great potential in photonic and optoelectronic devices. However, the relatively weak light absorption in 2D materials hinders their application in practical devices. Here, we propose a general approach to achieve angle-selective perfect light absorption in 2D materials. As a demonstration of the concept, we experimentally show giant light absorption by placing large-area single-layer graphene on a structure consisting of a chalcogenide layer atop a mirror and achieving a total absorption of 77.6% in the mid-infrared wavelength range (~13 μm), where the graphene contributes a record-high 47.2% absorptivity of mid-infrared light. Construction of such an angle-selective thin optical element is important for solar and thermal energy harvesting, photo-detection and sensing applications. Our study points to a new opportunity to combine 2D materials with photonic structures to enable novel device applications. A sandwich structure of graphene, chalcogenide and gold on top of a silicon wafer creates a thin, strong absorber in the mid-infrared. The structure, which was made by Linxiao Zhu and co-workers from the USA and China, absorbed as much as 77.6% of incident light at a wavelength of about 13 μm. Interestingly, the researchers say that their design approach is compatible with a wide range of 2D materials, not just graphene, and should in principle support perfect absorption at a specific angle. Giant absorption in such thin films could prove useful for applications such as photodetection and sensing as well as harvesting solar and thermal energy. The design does not feature any complex nanoscale structures, and so it should be possible to easily fabricate in large areas.
TL;DR: In this article, a bandgap-engineered GaAs0.26Sb0.74 alloy nanowires were synthesized via a chemical vapor deposition method, which showed a wide response in the near-infrared region with a high response peak located in the optical communication region (1.31 μm), as well as an external quantum efficiency of 1.62 × 105%, a responsivity of 17 × 103 A W−1 and a short response time of 60 ms.
Abstract: Single-nanowire photodetectors have potential applications in integrated optoelectronic devices and systems. Here, bandgap-engineered GaAs0.26Sb0.74 alloy nanowires were synthesized via a chemical vapor deposition method. The synthesized nanowires are single crystals grown along the [111]B direction with length up to 50 μm and diameter ranging from 40 to 500 nm. Photodetectors are built based on these single-alloy nanowires, which show a wide response in the near-infrared region with a high response peak located in the optical communication region (1.31 μm), as well as an external quantum efficiency of 1.62 × 105%, a responsivity of 1.7 × 103 A W−1 and a short response time of 60 ms. These novel near-infrared photodetectors may find promising potential applications in integrated infrared photodetection, thermal imaging, information communication and processing.
TL;DR: In this paper, the authors provide an overview of photodetection and then evaluate physical and chemical methods available for the fabrication of graphene p-n junctions, mainly focusing on the coupling of graphene with photonic structures and building vertical heterostructures.
TL;DR: In this paper, the feasibility of a possible implementation of microwave quantum teleportation in a realistic scenario with losses is discussed, and how to implement quantum repeaters in the microwave regime without using photodetection, a key prerequisite to achieve long distance entanglement distribution.
Abstract: Propagating quantum microwaves have been proposed and successfully implemented to generate entanglement, thereby establishing a promising platform for the realisation of a quantum communication channel. However, the implementation of quantum teleportation with photons in the microwave regime is still absent. At the same time, recent developments in the field show that this key protocol could be feasible with current technology, which would pave the way to boost the field of microwave quantum communication. Here, we discuss the feasibility of a possible implementation of microwave quantum teleportation in a realistic scenario with losses. Furthermore, we propose how to implement quantum repeaters in the microwave regime without using photodetection, a key prerequisite to achieve long distance entanglement distribution.