Synergistic Effects of Plasmonics and Electrons Trapping in Graphene Short-Wave Infrared Photodetectors with Ultrahigh Responsivity (original) (raw)
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InfoMat, 2022
Graphene with linear energy dispersion and weak electron-phonon interaction is highly anticipated to harvest hot electrons in a broad wavelength range. However, the limited absorption and serious backscattering of hot-electrons result in inadequate quantum yields, especially in the mid-infrared range. Here, we report a macroscopic assembled graphene (nMAG) nanofilm/silicon heterojunction for ultrafast mid-infrared photodetection. The assembled Schottky diode works in 1.5-4.0 μm at room temperature with fast response (20-30 ns, rising time, 4 mm 2 window) and high detectivity (1.6 Â 10 11 to 1.9 Â 10 9 Jones from 1.5 to 4.0 μm) under the pulsed laser, outperforming single-layer-graphene/silicon photodetectors by 2-8 orders. These performances are attributed to the greatly enhanced Li Peng and Lixiang Liu contributed equally to this work.
arXiv (Cornell University), 2021
We present a proof of concept for a spectrally selective near-infrared (NIR) and short-wavelength infrared (SWIR) photodetector based on nanopatterned multilayer graphene intercalated with FeCl3 (NPMLG-FeCl3), enabling large modulation p-doping of graphene. The localized surface plasmons (LSPs) on the graphene sheets in NPMLG-FeCl3 allow for electrostatic tuning of the photodetection in the NIR and SWIR regimes from λ = 1.3 µm to 3 µm, which is out of range for nanopatterned monolayer graphene (NPG). Most importantly, the LSPs along with an optical cavity increase the absorbance from about N × 2.6% for N-layer graphene-FeCl3 (without patterning) to nearly 100% for NPMLG-FeCl3, where the strong absorbance occurs locally inside the graphene sheets only. Our NIR and SWIR detection scheme relies on the photo-thermoelectric effect induced by asymmetric patterning of the multi-layer graphene (MLG) sheets. The LSPs on the nanopatterned side create hot carriers that give rise to Seebeck photodetection at room temperature achieving a responsivity of R = 6.15 × 10 3 V/W, a detectivity of D * = 2.3 × 10 9 Jones, and an ultrafast response time of the order of 100 ns. Our theoretical results pave the way to graphene-based photodetection, optical IR communication, IR color displays, and IR spectroscopy in the NIR, SWIR, mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR) regimes.
Direct Observation of High Photoresponsivity in Pure Graphene Photodetectors
Nanoscale research letters, 2017
Ultrafast and broad spectral bandwidth photodetectors are desirable attributable to their unique bandstructure s. Photodetectors based on graphene have great potential due to graphene's outstanding optical and electrical properties. However, the highest reported values of the photoresponsivity of pure graphene are less than 10 mA/W at room temperature, which significantly limits its potential applications. Here, we report a photoresponsivity of 32 A/W in pure monolayer graphene photodetectors, an improvement of over one order of magnitude for functional graphene nanostructures (<3 A/W). The high photocurrent generation in our devices can be attributed to the high sensitivity of graphene's resistivity to a local change of the electric field induced by photo-excited carriers generated in the light-doping substrate. This dramatically increases the feasibility of using graphene for the next generation of photodetectors.
Advanced Optical Materials, 2018
photoejected hot carriers excited through photon absorption in metal structures and extracted via internal photoemission [1,2] with the intriguing prospect of direct below-bandgap photodetection at room temperature (RT). However, the collection efficiency of photoejected hot carriers at metal-semiconductor (MS) interface [3] or metal-insulator-metal (MIM) junctions [4] is severely hindered by (i) the fast internal relaxation process, (ii) momentum mismatch, and (iii) the lack of effective lighttrapping mechanisms. To date, plasmonic modes in metals have been widely utilized to enhance photoemission of hot electrons since they can concentrate photon energy in a deep subwavelength region, where extensive amounts of hot electrons can be generated. [5-7] Therefore, the working wavelength can be tuned by simply adjusting the frequency of metal plasmonic resonance rather than the bandgap of materials. Hot carriers can be generated in a femtosecond timescale via the Laudau damping of plasmonic modes [8] and they are lifted from electronic states below the Fermi level with appropriate energy hυ. However, they lose their energy very fast, as a consequence, only a small portion of them is able to escape from the MS or MIM interface. Despite the presence of Photodetectors exploiting photoejected hot electrons have the potential to achieve ultrahigh sensitivity and broadband detection capabilities, which are controlled by the structure of the device rather than the bandgap of the employed materials. However, the achievement of photodetectors of long-wavelength photons with both high responsivity and bandwidth is still challenging. Here, a novel class of high-gain photodetectors based on the manipulation of intrinsic hot carriers by exploiting the electromagnetic engineering of a graphene-based active channel is presented. Light field is focused in a split-finger gated structure to create a potential gradient in the channel, which is able to trap and detrap the charges laterally transferred from low resistive Au-graphene interface, finally leading to a high photoconductive gain. Correspondingly, the device activity can be easily switched from photovoltaic to photoconductive, depending on the photoinduced hot-carrier distribution, just by controlling the electric field. The device shows tunable sensitivity, higher energy efficiency, and photoconductive gain. In particular, the responsivity (0.6-6.0 kV W −1) and the noise-equivalent power (less than 0.1 nW Hz −0.5 at room temperature) are significantly improved even at low-energy terahertz band with respect to state-of-the-art devices based on extrinsically coupled hot carriers operating in the near infrared.
Ultrafast graphene photodetector
Nature Nanotechnology, 2009
The electronic properties of graphene are unique and are attracting increased attention to this novel 2-dimensional system. Its photonic properties are not less impressive. For example, this single atomic layer absorbs through direct interband transitions a considerable fraction of the light (~2.3%) over a very a broad wavelength range. However, while applications in electronics are vigorously being pursued, photonic applications have not attracted as much attention. Here, we report on ultrafast photocurrent response measurements in graphene (single and few-layers) field-effect-transistors (FETs) up to 40 GHz light intensity modulation frequencies, using a 1.55 micron excitation laser. No photoresponse degradation is observable up to the highest measured frequency, demonstrating the feasibility and unique benefits of using graphene in photonics. Further analysis suggests that the intrinsic bandwidth of such graphene FET based photodetectors may exceed 500 GHz. Most notably, the generation and transport of the photo-carriers in such graphene photodetectors are fundamentally different from those in currently known semiconductor photodetectors, leading to a remarkably high bandwidth, zero source-drain bias (hence zero dark current) operation, and good internal quantum efficiency.
Substrate-Sensitive Mid-infrared Photoresponse in Graphene
ACS Nano, 2014
We report mid-infrared photocurrent spectra of graphene nanoribbon arrays on SiO 2 dielectrics showing dual signatures of the substrate interaction. First, hybrid polaritonic modes of graphene plasmons and dielectric surface polar phonons produce a thermal photocurrent in graphene with spectral features that are tunable by gate voltage, nanoribbon width, and light polarization. Secondly, phonon-polaritons associated with the substrate are excited, which indirectly heat up the graphene leading to a graphene photocurrent with fixed spectral features. Models for other commonly used substrates show that the responsivity of graphene infrared photodetectors can be tailored to specific mid-IR frequency bands by the choice of the substrate.
Scientific Reports, 2013
Graphene's unique optoelectronic properties are promising to realize photodetectors with ultrafast photoresponse over a wide spectral range from far-infrared to ultraviolet radiation. The underlying mechanism of the photoresponse has been a particular focus of recent work and was found to be either photoelectric or photo-thermoelectric in nature and enhanced by hot carrier effects. Graphene supported by a substrate was found to be dominated by the photo-thermoelectric effect, which is known to be an order of magnitude slower than the photoelectric effect. Here we demonstrate fully-suspended chemical vapor deposition grown graphene microribbon arrays that are dominated by the faster photoelectric effect. Substrate removal was found to enhance the photoresponse by four-fold compared to substrate-supported microribbons. Furthermore, we show that the light-current input/output curves give valuable information about the underlying photophysical process responsible for the generated photocurrent. These findings are promising towards wafer-scale fabrication of graphene photodetectors approaching THz cut-off frequencies.
Optics Express, 2017
We study the operation of infrared photodetectors based on van der Waals heterostructures with the multiple graphene layers (GLs) and n-type emitter and collector contacts. The operation of such GL infrared photodetectors (GLIPs) is associated with the photoassisted escape of electrons from the GLs into the continuum states in the conduction band of the barrier layers due to the interband photon absorption, the propagation of these electrons and the electrons injected from the emitter across the heterostructure and their collection by the collector contact. The space charge of the holes trapped in the GLs provides a relatively strong injection and large photoelectric gain. We calculate the GLIP responsivity and dark current detectivity as functions of the energy of incident infrared photons and the structural parameters. It is shown that both the periodic selective doping of the inter-GL barrier layers and the GL doping lead to a pronounced variation of the GLIP spectral characteristics, particularly near the interband absorption threshold, while the doping of GLs solely results in a substantial increase in the GLIP detectivity. The doping "engineering" opens wide opportunities for the optimization of GLIPs for operation in different parts of radiation spectrum from near infrared to terahertz.