Graphene-based Photodetectors Research Articles

Spectrally Tunable Ultrafast Long Wave Infrared Detection at Room Temperature.

Room-temperature longwave infrared (LWIR) detectors are preferred over cryogenically cooled solutions due to the cost effectiveness and ease of operation. The performance of present uncooled LWIR detectors such as microbolometers, is limited by reduced sensitivity, slow response time, and the lack of dynamic spectral tunability. Here, we present a graphene-based efficient room-temperature LWIR detector with high detectivity and fast response time utilizing its tunable optical and electronic characteristics. The inherent weak light absorption is enhanced by Dirac plasmons on the patterned graphene coupled to an optical cavity. The absorbed energy is converted into photovoltage by the Seebeck effect with an asymmetric carrier generation environment. Further, dynamic spectral tunability in the 8-12 μm LWIR band is achieved by electrostatic gating. The proposed detection platform paves the path to a fresh generation of uncooled graphene-based LWIR photodetectors for wide ranging applications such as molecular sensing, medical diagnostics, military, security and space.

Lithium niobate waveguide-integrated Bi2Te3/graphene heterojunction photodetector.

We demonstrate an on-chip photodetector by integrating a graphene and topological insulator Bi2Te3 heterostructure on a thin-film lithium niobate waveguide. Lithium niobate on insulator (LNOI) waveguides are fabricated by the photolithography-assisted chemical mechanical etching method. The bismuth telluride (Bi2Te3) and graphene heterostructure design provides enhanced photocurrent due to the effective photocarrier generation. The lithium niobate waveguide-integrated Bi2Te3/graphene heterojunction presents a high absorption coefficient of 2.1 dB/µm. The Bi2Te3/graphene heterojunction photodetector exhibits a responsivity of 2.54 mA/W without external bias at a 1.55 µm wavelength, which is enhancement of sevenfold as compared to the pure graphene-based photodetector. The photodetector has a 3 dB bandwidth of over 4.7 GHz. This work provides a potentially viable method for a self-powered, high responsivity, and fast response of the photodetector integrated with the LNOI photonic platform.

Patterned 3D-graphene for self-powered broadband photodetector

The remarkable ultra-wideband energy capabilities of zero-bandgap two-dimensional (2D) graphene have made it an outstanding material for photon absorption and charge carrier generation across a broad spectrum. However, atomically thick 2D-graphene only exhibits a light absorption efficiency of 2.3%, posing a challenge for graphene-based photodetectors to harness photon energy effectively. This study utilized plasma-enhanced chemical vapor deposition technology and a mask to create in situ patterned 3D-graphene/Si-based Schottky heterojunctions. The porous structure and natural nano-resonant cavities of the 3D-graphene enhanced the probability of light absorption, while the curved and sharp edges and corners of the patterned 3D-graphene concentrated the local electromagnetic field and induced localized surface plasmon resonance. Both theoretical and experimental analyses confirmed the improved light absorption mechanisms and charge transfer of photogenerated carriers under the built-in electric field. The photodetector based on the patterned 3D-graphene/Si Schottky structure exhibits excellent broadband response characteristics spanning from 380 to 1550 nm, with responsivity and specific detectivity of 68.47 A/W and 1.43 × 1012 Jones at a wavelength of 1550 nm. Furthermore, the photodetector demonstrated ultrafast microsecond-level response times (116/120 μs rise/fall times) along with exceptional stability and reliability. The potential applications of as-fabricated photodetector include logic devices such as “AND” and “OR” gates and information encryption. This research holds valuable scientific significance for the design of future optoelectronic devices and provides crucial insights and technical support for developing high-performance Si-based graphene detectors.

Optimal design of graphene-based plasmonic enhanced photodetector using PSO

In this paper, we report a graphene-based plasmonic photodetector optimized using the particle swarm optimization (PSO) algorithm and compatible with complementary metal–oxide–semiconductor (CMOS) technology. The proposed photodetector structure is designed to minimize fabrication challenges and reduce production costs compared to more complex alternatives. Graphene has been used for its unique properties in the detection region, titanium nitride (TiN) as a CMOS-compatible metal, and both to aid in plasmonic excitation. Photodetectors have key parameters influenced by multiple independent variables. However, practical constraints prevent thorough adjustment of all variables to achieve optimal parameter values, often resulting in analysis based on several simplified models. Here we optimize these variables by presenting a new approach in the field of photodetectors using the capabilities of the PSO algorithm. As a result, for the proposed device at the wavelength of 1550 nm, the voltage responsivity is 210.6215 V/W, the current responsivity is 3.7213 A/W, the ultra-compressed length is less than 3μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu {\ ext{m}}$$\\end{document}, and the specific detectivity is 2.566×107\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{7}$$\\end{document} Jones were obtained. Furthermore, the device in question works under the photothermoelectric effect (PTE) at zero bias and has zero dark current, which ultimately resulted in a very low noise equivalent power (NEP) of 4.5361 pW/Hz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{pW}}/\\sqrt{\ ext{Hz}}$$\\end{document}.

Impact of device resistances in the performance of graphene-based terahertz photodetectors

In recent years, graphene field-effect-transistors (GFETs) have demonstrated an outstanding potential for terahertz (THz) photodetection due to their fast response and high-sensitivity. Such features are essential to enable emerging THz applications, including 6G wireless communications, quantum information, bioimaging and security. However, the overall performance of these photodetectors may be utterly compromised by the impact of internal resistances presented in the device, so-called access or parasitic resistances. In this work, we provide a detailed study of the influence of internal device resistances in the photoresponse of high-mobility dual-gate GFET detectors. Such dual-gate architectures allow us to fine tune (decrease) the internal resistance of the device by an order of magnitude and consequently demonstrate an improved responsivity and noise-equivalent-power values of the photodetector, respectively. Our results can be well understood by a series resistance model, as shown by the excellent agreement found between the experimental data and theoretical calculations. These findings are therefore relevant to understand and improve the overall performance of existing high-mobility graphene photodetectors.Graphical

High-quality lateral monolayer-multilayer graphene junction formed by selective laser thinning for self-powered photodetection

The formation of an asymmetric junction is key to graphene-based photodetectors of high-sensitive photodetectability, because such a junction can not only facilitate the diffusion or drift of photogenerated carriers but also realize a self-powered operation. Here, a monolayer-multilayer graphene junction photodetector is accomplished by selectively thinning part of a multilayer graphene to a high-quality monolayer. Benefiting from the large photoabsorption cross section of multilayer graphene and strong asymmetry caused by the significant differences in optoelectronic properties between monolayer and multilayer graphene, the monolayer-multilayer graphene junction shows a 7-fold increase in short-circuit photocurrent as compared with that at the monolayer graphene-metal contact in scanning photocurrent images. The asymmetric configuration also enables the photodetector to work at zero bias with minimized dark current noise and stand-by power consumption. Under global illumination with visible light, a photoswitching ratio of 3.4 × 103, a responsivity of 8.8 mA W−1, a specific detectivity of 1.3 × 108 Jones and a response time of 11 ns can be obtained, suggesting a promising photoresponse. Moreover, it is worth mentioning that such a performance enhancement is achieved without compromising the broadband spectral response of graphene photodetector and it is hence applicable for long wavelength spectral range including infrared and terahertz.

Hybrid graphene-high-aspect ratio plasmonic nanograting systems

One-dimensional plasmonic nanogratings (1D-PNGs) with high aspect ratios and narrow grooves promise enhanced coupling for hybrid graphene systems with the localized surface plasmon of the metallic grating and graphene surface plasmons. However, both the fabrication of the 1D-PNG and the application of graphene to it are difficult. We developed 1D-PNGs with a high aspect ratio of 15 and narrow grooves of 100 nm in width using the tapered mold method and a dry graphene-transfer procedure. Raman spectroscopy measurements showed that monolayer graphene was successfully transferred onto the 1D-PNGs, and the graphene was strongly doped with Au in the 1D-PNGs. Graphene on narrow grooves (free-standing graphene) demonstrated an almost identical p-doping level to graphene on Au because the narrow groove width allowed sufficient doping by Au for graphene on grooves. Reflectance measurements showed that the 1D-PNGs exhibited polarization- and wavelength-selective absorption at infrared (IR) wavelengths, and the effect of graphene blue-shifted the absorption peak wavelength induced by the surface plasmon resonance of 1D-PNGs. Numerical calculations agree well with these experimental results and indicate that the electric field strongly localizes on graphene in the grooves. Moreover, the doping level tunes the absorption wavelength owing to the coupling with graphene plasmons and the surface plasmon resonance of 1D-PNGs. This could provide electrical tunability to the graphene plasmons. Our fabrication procedure produced hybrid graphene-1D-PNGs with high aspect ratios and narrow groove systems for IR wavelengths. This system can contribute to developing high-performance electrically tunable graphene-based IR photodetectors, tunable IR emitters/absorbers, and biological sensors.

Giant Negative Photoresponse in van der Waals Graphene/AgBiP2Se6/Graphene Trilayer Heterostructures.

The positive photoconductive (PPC) effect is a well-established primary detection mechanism employed by photodetectors. In contrast, the negative photoconductive (NPC) effect is not extensively investigated thus far, and research on the NPC effect is still in its early stage. Herein, a quaternary van der Waals material, AgBiP2Se6 atomic layers, is discovered to achieve a giant NPC effect. Through experimental observations in a Graphene/AgBiP2Se6/ Graphene-based vertical photodetector, an irreversible conversion is identified from common PPC photoresponse to atypical NPC photoresponse. Notably, this device demonstrates an exceptionally high negative responsivity (R) of 4.9×105AW-1, surpassing the previous records for NPC photodetectors. Additionally, it exhibits remarkable optoelectronic performances, including an external quantum efficiency of 1.3×108% and a detectivity (D) of 3.60×1012Jones. The exceptionally high NPC photoresponse observed in this device can be attributed to the swift suppression of photogenerated free carriers at robust recombination centers situated at significant depths, induced by the elevated drain-source voltage bias. The remarkably high NPC photoresponse also positions AgBiP2Se6 as a promising 2D material for multifunctional optoelectronic devices and an excellent platform for systematic exploration of the NPC effect.

Highly efficient organic-graphene hybrid photodetectors via molecular peripheral editing.

Hybrid systems based on graphene and organic molecules are highly appealing for "correcting" the limited optoelectronic properties of 2D materials. However, an in-depth understanding of the correlation between the structure of the molecular sensitizer and the physical properties of the hybrid toward high-performance organic-graphene hybrid photodetectors remains elusive. Herein, an ad hoc molecular design via a peripheral editing approach on the organic molecules is employed to elucidate the structure-property relationship when interfaced with graphene forming hybrid systems. Efficient doping of graphene can be attained by physisorption of tetrathiafulvalene molecules exposing electron-donating peripheral groups, benefiting from a strong coupling yielding efficient charge transfer, ultimately leading to photodetectors with an ultra-high responsivity of 1.1 × 107 A W-1 and a specific detectivity of 6.5 × 1014 Jones, thereby outperforming state-of-the-art graphene-based photodetectors. These results offer valuable insights for future optimization of graphene-based photodetectors through molecular functionalization.

High-Performance Photodetectors Based on Semiconducting Graphene Nanoribbons.

The inherent zero-band gap nature of graphene and its fast photocarrier recombination rate result in poor optical gain and responsivity when graphene is used as the light absorption medium in photodetectors. Here, semiconducting graphene nanoribbons with a direct bandgap of 1.8 eV are synthesized and employed to construct a vertical heterojunction photodetector. At a bias voltage of -5 V, the photodetector exhibits a responsivity of 1052 A/W, outperforming previous graphene-based heterojunction photodetectors by several orders of magnitude. The achieved detectivity of 3.13 × 1013 Jones and response time of 310 μs are also among the best values for graphene-based heterojunction photodetectors reported until date. Furthermore, even under zero bias, the photodetector demonstrates a high responsivity and detectivity of 1.04 A/W and 2.45 × 1012 Jones, respectively. The work shows a great potential of graphene nanoribbon-based photodetection technology.

Plasmon resonance-enhanced graphene nanofilm-based dual-band infrared silicon photodetector

Graphene-based photodetectors have attracted much attention due to their unique properties, such as high-speed and wide-band detection capability. However, they suffer from very low external quantum efficiency in the infrared (IR) region and lack spectral selectivity. Here, we construct a plasmon-enhanced macro-assembled graphene nanofilm (nMAG) based dual-band infrared silicon photodetector. The Au plasmonic nanostructures improve the absorption of long-wavelength photons with energy levels below the Schottky barrier (between metal and Si) and enhance the interface transport of electrons. Combined with the strong photo-thermionic emission (PTI) effect of nMAG, the nMAG–Au–Si heterojunctions show strong dual-band detection capability with responsivities of 52.9 mA/W at 1342 nm and 10.72 mA/W at 1850 nm, outperforming IR detectors without plasmonic nanostructures by 58–4562 times. The synergy between plasmon–exciton resonance enhancement and the PTI effect opens a new avenue for invisible light detection.

High responsivity photodetectors based on graphene/WSe2 heterostructure by photogating effect

Graphene, with its zero-bandgap electronic structure, is a highly promising ultra-broadband light absorbing material. However, the performance of graphene-based photodetectors is limited by weak absorption efficiency and rapid recombination of photoexcited carriers, leading to poor photodetection performance. Here, inspired by the photogating effect, we demonstrated a highly sensitive photodetector based on graphene/WSe2 vertical heterostructure where the WSe2 layer acts as both the light absorption layer and the localized grating layer. The graphene conductive channel is induced to produce more carriers by capacitive coupling. Due to the strong light absorption and high external quantum efficiency of multilayer WSe2, as well as the high carrier mobility of graphene, a high photocurrent is generated in the vertical heterostructure. As a result, the photodetector exhibits ultra-high responsivity of 3.85 × 104 A/W and external quantum efficiency of 1.3 × 107%. This finding demonstrates that photogating structures can effectively enhance the sensitivity of graphene-based photodetectors and may have great potential applications in future optoelectronic devices.

Graphene-based midinfrared photodetector with bull’s eye plasmonic antenna

Graphene-based midinfrared photodetector with bull’s eye plasmonic antenna

Metamaterial graphene photodetector with bandwidth exceeding 500 gigahertz.

Although graphene has met many of its initially predicted optoelectronic, thermal, and mechanical properties, photodetectors with large spectral bandwidths and extremely high frequency responses remain outstanding. In this work, we demonstrate a >500 gigahertz, flat-frequency response, graphene-based photodetector that operates under ambient conditions across a 200-nanometer-wide spectral band with center wavelengths adaptable from <1400 to >4200 nanometers. Our detector combines graphene with metamaterial perfect absorbers with direct illumination from a single-mode fiber, which breaks with the conventional miniaturization of photodetectors on an integrated photonic platform. This design allows for much higher optical powers while still allowing record-high bandwidths and data rates. Our results demonstrate that graphene photodetectors can outperform conventional technologies in terms of speed, bandwidth, and operation across a large spectral range.

Interface engineering by inserting Al2O3 tunneling layer to enhance the performance of graphene/GaAs heterojunction photodetector

Interface engineering is an effective way to improve the performance of graphene-based photodetectors. Here, a graphene/GaAs heterojunction photodetector is fabricated, and when inserting an Al2O3 tunneling layer, its performance is improved through direct tunneling (DT) and Fowler-Nordheim tunneling (FNT). According to the experimental results, it is found that the thickness of the tunneling layer has a great influence on the performance of the photodetector. Compared with graphene/GaAs photodetector, the performance of graphene/Al2O3(2 nm)/GaAs photodetector is significantly improved with the responsivity, detectivity, and external quantum efficiency value of 0.80 A/W, 3.02 × 1011 Jones and 306% under 1 mW/cm2 light intensity at 2 V bias. Meanwhile, fast response is also observed (rise/decay time of 3 ms/8.6 ms). The improvement of the photodetector's performance in this work is mainly attributed to the effective modification of the interface state by the Al2O3 tunneling layer and the effect of the two tunneling mechanisms based on DT and FNT.

Graphene-Quantum Dots Hybrid Based Dual Band Photodetector

Graphene, which can detect a broad spectrum from ultraviolet to terahertz, is a promising photodetector material because it offers a broad spectral bandwidth and fast response times. However, the nature of weak light absorption has limited the responsivity of graphene-based photodetectors. Here, we demonstrate a responsivity of up to ∼6.7×103 A/W in a hybrid photodetector that consists of monolayer or bilayer graphene covered with a thin film of colloidal quantum dots. At the same time, benefits from gate-tunability, the device can response from the short-wavelength infrared to the visible, and compatibility with current circuit technologies.

Self-Driven Photo-Polarized Water Molecule-Triggered Graphene-Based Photodetector.

Flowing water can be used as an energy source for generators, providing a major part of the energy for daily life. However, water is rarely used for information or electronic devices. Herein, we present the feasibility of a polarized liquid-triggered photodetector in which polarized water is sandwiched between graphene and a semiconductor. Due to the polarization and depolarization processes of water molecules driven by photogenerated carriers, a photo-sensitive current can be repeatedly produced, resulting in a high-performance photodetector. The response wavelength of the photodetector can be fine-tuned as a result of the free choice of semiconductors as there is no requirement of lattice match between graphene and the semiconductors. Under zero voltage bias, the responsivity and specific detectivity of Gr/NaCl (0.5 M)W/N-GaN reach values of 130.7 mA/W and 2.3 × 109 Jones under 350 nm illumination, respectively. Meanwhile, using a polar liquid photodetector can successfully read the photoplethysmography signals to produce accurate oxygen blood saturation and heart rate. Compared with the commercial pulse oximetry sensor, the average errors of oxygen saturation and heart rate in the designed photoplethysmography sensor are ~1.9% and ~2.1%, respectively. This study reveals that water can be used as a high-performance photodetector in informative industries.

Graphene/Al2O3/InGaAs-based nanostructures for near-infrared photodetectors passivated by InP layer

In the past decade, graphene-based near infrared photodetectors (NIR PDs) have attracted attention for their high response speed and high responsivity. As a promising graphene-based nanostructure, the InGaAs/Al2O3/graphene device has been proven to have important applications in the detection of the near infrared light. The monolayer graphene and a thin Al2O3 layer could improve the device performance. However, the device degraded the current-voltage (I–V) characteristics. To enhance the resistance of this Schottky nanostructure NIR PD to the irreversible degradation, a layer of p-InP under the SiNx is expected to reduce the defects and enhance the absorption of NIR light. In this work, the Schottky nanostructure NIR PD with the InP layer has a high detectivity of 2.3⨯1013 cm Hz1/2 W−1, a high response speed of 557 ns/3.22 μs, and a high responsivity of 11.23 A/W at −1.5 V and 1.32 A/W at 0 V to 1550 nm infrared light, which is even larger than that of the metal-oxidation-semiconductor (MOS) structure. The wavelength-responsivity (λ-R) characteristics measured by different infrared lasers ranging from 808 nm to 1870 nm indicated a wide response spectrum. Moreover, the phenomenon of the reverse photocurrent was observed and analyzed.

Graphene nanoribbon/graphene hybrid broadband infrared photodetectors

Graphene nanoribbons (GNRs) and graphene hybrid photodetectors were demonstrated in the middle- and long-wavelength infrared (MWIR and LWIR, respectively) regions. Graphene transistors were prepared using Si substrates with an SiO2 layer and source and drain electrodes. Single-layer graphene fabricated by chemical vapor deposition was transferred onto the substrates to form a channel; the GNR was formed on this channel by solution dispersion. The formation of graphene and the GNR was confirmed by position mapping of the Raman spectra. The photoresponse was measured in the MWIR and LWIR regions, and was found to be drastically enhanced for devices with the GNR when compared with those without it. Although the devices without the GNR could not respond at temperatures higher than 15 K, those with the GNR could be operated at temperatures up to 150 K. This was attributed to photogating by the GNR layers that absorbed the MWIR and LWIR radiation, leading to a significant temperature change. These results can potentially contribute toward developing high-performance and broadband IR graphene-based photodetectors.

Hexagonal-boron nitride/graphene van der Waals heterostructure-based wavelength-selective infrared absorbers using plasmonic metasurfaces for multi-spectral infrared photodetectors

Graphene has promising applications for novel optoelectronic devices. However, graphene-based photodetectors have two major drawbacks that need attention. The first is how to preserve graphene’s original high carrier mobility, and the second is how to enhance graphene’s absorption to improve its performance. Hexagonal boron nitride (hBN)/graphene van der Waals (vdW) heterostructure-based plasmonic metasurfaces (PMs) are proposed for wavelength-selective infrared (IR) photodetectors. hBN preserves graphene’s high carrier mobility, and PMs enhance graphene’s absorption. Numerical calculations demonstrate sufficient wavelength-selective absorption in the broadband IR wavelength range. Such optical properties are realized by coupling the localized surface plasmon resonance (SPR) of PMs and propagating SPR of graphene. The proposed vdW heterostructure-based PMs could be used for high-performance multi-spectral IR photodetectors.