The present invention relates to high-speed mid-infrared (MIR) photodetectors with high sensitivity at room temperature.
High-speed MIR photodetectors with high sensitivity are needed for many applications, including MIR hyper-spectral imaging, biomedical sensing, environment monitoring, and astronomy. Yet, it remains a great challenge to realize sensitive and cost-effective MIR photodetectors with short response time (nanoseconds or picoseconds) at room temperature, especially in the longer wavelength range (>8 μm), due to the fundamental limitations in current detection technologies and their lack of compatibility with complementary metal-oxide-semiconductor (CMOS) circuits.
Graphene-based CMOS-compatible photodetectors operable over the MIR wavelength region (i.e., 2-24 μm) with room temperature operation, high sensitivity (D*>2×108 cm-Hz1/2/W), short response time (nanoseconds), and ultra-compact size (area: 10 μm×10 μm, thickness: <1 μm) are described. These photodetectors enhance the optical absorption in graphene to close to 90% and realize close to unity photocarrier collection. In addition, detector noise due to dark current is effectively eliminated, and response time can be as short as sub-nanosecond.
Thus, particular implementations have been described. Variations, modifications, and enhancements of the described implementations and other implementations can be made based on what is described and illustrated. In addition, one or more features of one or more implementations may be combined. The details of one or more implementations and various features and aspects are set forth in the accompanying drawings, the description, and the claims below.
The MIR devices described herein are graphene hybrid/heterostructure photodetectors (GHPD) based on two-dimensional semiconductor materials and plasmonic metasurfaces including metallic optical antenna arrays. These MIR photodetectors, fabricated at wafer scale on silicon substrates, operate at room temperature with high sensitivity (D*>2×108 cm-Hz1/2/W), short response time (nanoseconds), and ultra-compact size (area: 10 μm×10 μm, thickness: <1 μm). These MIR photodetectors are also compatible with CMOS technology, allowing low-cost, large-scale production of MIR imaging systems at room temperature. As described herein, plasmonic metasurface structures are designed to realize up to 90% optical absorption in graphene over the MIR spectral region from 8 μm to 12 μm.
Plots 110, 112, and 114 in
In some implementations, antenna electrode 122 includes first metal layer 124 formed of palladium and second metal layer 126 formed of gold, and antenna electrode 122′ includes first metal layer 124′ formed of titanium and second metal layer 126′ formed of gold. In some implementations, antenna electrode 122 includes first metal layer 124 formed of palladium and second metal layer 126 formed of gold, and antenna electrode 122′ includes first metal layer 124′ formed of palladium and second metal layer 126′ formed of gold. In some implementations, antenna-assisted photovoltaic graphene detector 120 is fabricated on silicon layer 128 in contact with metal layer 102. The inset to
To achieve low noise metasurface-assisted graphene photodetectors with high photocarrier collection efficiency (e.g., close to 100%) at room temperature, antenna electrodes made of different metals (e.g., Pd and Ti) are patterned to create a built-in potential (e.g., ˜0.1 V) across the nanogap (nanoscale antenna gap or channel length) g (e.g., ˜100 nm) between antenna electrodes 122, 122′, as depicted in
Calculations indicate that the internal quantum efficiency (defined as the ratio of the number of collected photocarriers to that of absorbed photons) increases as the graphene channel length between the antenna electrodes decreases, as shown in
Vertical tunneling in some graphene heterostructures (e.g., graphene/boron nitride/graphene or graphene/molybdenum disulfide/graphene) may be exploited to increase the photocarrier lifetime in graphene. Reference is made to
Plots 200, 202, and 204 in
The maximum absorption can be designed at different wavelengths by tailoring the dimensions of the antenna electrodes formed on the graphene heterostructure and the dielectric layer. More than 95% absorption can be realized at the cavity resonance wavelength. Near field distribution shows that light is highly focused in the nanogap between the antenna electrodes. Therefore, most of the photocarriers will be generated in the gap so that they will be collected very efficiently by the antenna electrodes via built-in potential. Plots 210, 212, and 214 in
In graphene photoconductors, an external bias is typically necessary to collect photocarriers efficiently, which however, lead to high dark currents and thus high noise. Improvement of the photocarrier collection efficiency while minimizing the dark current is achieved with antenna-assisted photovoltaic graphene detectors to achieve highly sensitive graphene photodetectors.
The internal quantum efficiency can be obtained by G=2τR/τtr, in which the carrier recombination time τR≈0:23 ps (extracted from experimental results from a CVD graphene sample). The carrier transit time τtr across the graphene channel between the two electrodes (channel length g) can be calculated by τtr=g/νd, where νd is the drift velocity. Assuming a saturation velocity of 5.5×105 m/s at low carrier density, the drift velocity is approximated by a velocity saturation model, i.e.,
The electrical field E in the graphene channel inside the gap is determined by the built-in potential, i.e., E=VIN/g. Plots 310, 312, and 314 in
Artificial heterostructures assembled from van der Waals materials are thought to combine materials without the traditional restrictions in heterostructure growth such as lattice matching conditions and atom interlayer-diffusion. Because the interaction between planes is very weak, only small changes in the electronic structure are expected by stacking these materials on top of each other. The carrier tunneling process in heterostructures formed by graphene and other two-dimensional materials, such as boron nitride and molybdenum disulfide, is exploited to realize MIR photodetectors.
Boron nitride (BN) and molybdenum disulfide (MoS2), which have different band gaps, are used in different layer thicknesses. For a single layer of BN used as the barrier, the coupling strength is estimated to be 2ℏΩ˜10 meV and the tunneling rate is RTB=2Ω2τ, where τ is the carrier relaxation time in graphene (τ≈30 fs, extracted from transport measurement of CVD graphene samples). Thus, the tunneling rate is ˜3×1012 s−1, which is fast enough to separate more than 25% photogenerated electrons and holes in the graphene before they recombine (photocarrier lifetime τR≈0.23 ps). Integration of graphene heterostructures with plasmonic metasurfaces, as depicted, for example, in
The detector responsivity is calculated as
The noise current at zero-bias and in absence of signal light radiation is
where the first term represents the shot noise and the second term represent the thermal noise, respectively. B is the detector bandwidth. At zero external bias, the thermal noise can be estimated to be
where RG is the graphene detector resistance. The noise equivalent power (NEP) and detectivity D* can be calculated as
and D*=√{square root over (A)}/NEP, respectively (A is the detector area). The responsivity and detectivity (D*) of the antenna-assisted photovoltaic graphene detector 300 are calculated around wavelength λ0=8 μm and shown as plots 500 and 502, respectively, in
Models that can be used for photodetector device modeling include a closed analytical model and a three-dimensional numerical model of antenna-assisted photovoltaic graphene detectors based on the finite element method (COMSOL). The analytical model is sufficient to obtain general trends for improving device performance, for example, when combined with full wave optical simulation results, e.g., the antenna gap size and the carrier mobility.
To obtain a more accurate prediction of the device performance, a 3D numerical model based on finite element method (FEM, COMSOL Inc. http://www.comsol.com/) can be used. A model with COMSOL is used to simulate the electrical transport behavior of the antenna-assisted graphene detectors. The simulated current density distribution in a portion of the graphene-antenna structure for a bias voltage VDS=0.2 V and a gate voltage VG=5 V is shown in
Antenna-assisted photovoltaic graphene detectors described herein may be fabricated on a silicon wafer. In one example, fabrication includes evaporation of an aluminum layer (e.g., about 300 nm thick) onto the top surface of the silicon wafer, followed by atomic layer deposition (ALD) of a dielectric layer, such as an aluminum oxide (AlOx) layer (e.g., 300-400 nm thick). A thin barrier layer (e.g., BN) may be transferred onto the dielectric layer, followed by the transfer of a monolayer or double-layer graphene sheet. Mechanically exfoliated thin layers of BN and chemical vapor deposition (CVD) grown monolayer or few layer BN (purchased from companies such as graphene-supermarket.com) are suitable. The graphene sheet is then transferred onto the dielectric layer or barrier layer. In one example, to make two different metal contacts, the antenna electrodes made with Pd/Au are first patterned on graphene, and the Ti/Au antenna electrodes are then fabricated. The metal electrodes may be fabricated by electron beam lithography (EBL), electron beam evaporation of Pd (or Ti) and 30 nm Au, and lift-off. In the second EBL step, alignment is required. An alignment error of ˜30-50 nm is tolerable.
A self-aligned angle-deposition technique, such as that depicted in
In some implementations, the first metal is titanium or palladium, the second metal is titanium or palladium, and the third and fourth metals are gold. When the first metal is different from the second metal (e.g., the first metal is palladium and the second metal is titanium), the three angle-evaporation steps depicted in
Antenna-assisted photovoltaic graphene detectors can be characterized with a MIR laser scanning photovoltage mapping setup, with the samples mounted on a two-dimensional motorized stage. The output of quantum cascade (QC) lasers (based on a broadband laser design, wavelength λ0=7-13 μm) is focused onto the sample by a MIR microscope objective. This is introduced based on the closeness of the detector area (˜10×10 μm2) to the diffraction limit. Incoherent broadband MIR sources typically cannot provide such a small beam size. The local photovoltage response of larger area detectors may be measured by scanning the position of the focused laser beam on the sample with a spatial resolution of ˜2 μm to determine device uniformity.
Device characterization results include optical measurement, detector responsivity, dark current, and detector noise. Depicts optical characterization setup 800 for characterization of sample 802. Optical characterization setup 800 includes detector 804, aperture 806, beam splitter 808, objective 810, Fourier transform infrared spectrometer 812, and polarizer 814. Experimental results may be compared with simulation results obtained by the graphene detector model to extract the photocarrier collection efficiency and to characterize the built-in potential introduced by antenna electrodes with different metal contact layers.
Two types of graphene-metasurface detectors are shown in
In the detectors depicted in
The antenna electrodes in detectors 900, 920 are connected to the drain and source electrodes via thin metal wires. The metal wires do not interfere with antenna resonance so that the optical response of detector does not change significantly, and perfect absorption can be achieved by small adjustment of the design parameters, such as antenna length and the thickness of the dielectric layer (aluminum oxide). According to full wave simulation, the maximum optical absorption in single and double layer graphene can be more than 50% and 70%, respectively.
In detectors 900 and 920, the RC time constant is estimated to be τRC≈50 ps, assuming the load resistance is 50Ω and the area of the contact pads is 104 μm2. Besides the RC time constant, other factors may affect the response time of graphene photodetectors, for example, the photocarrier recombination time in graphene (τR), and the carrier transit time across the graphene channel between the two antenna electrodes (τtr). The carrier recombination time in graphene is ˜1 ps or shorter. The carrier transit time τtr is also shorter than 1 ps for a built-in potential of 60 meV over a 100 nm-long graphene channel. Therefore, in graphene detectors, the RC time limited bandwidth is estimated to be fT=3.5/2πτRC≈10 GHz. The detector bandwidth can be further improved by increasing the dielectric thickness underneath the contact pad and thus reducing the parasitic capacitance.
Graphene-metasurface photodetectors described herein are applicable to the whole MIR wavelength region (e.g., 3-24 μm).
Further modifications and alternative embodiments of various aspects will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. It is to be understood that the forms shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description. Changes may be made in the elements described herein without departing from the spirit and scope as described in the following claims.
This application claims the benefit of U.S. Patent Application Ser. No. 62/323,133 entitled “ANTENNA-ASSISTED PHOTOVOLTAIC GRAPHENE DETECTORS” and filed on Apr. 15, 2016, which is incorporated by reference herein in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
8554022 | Hochberg | Oct 2013 | B1 |
9293627 | Beechem, III | Mar 2016 | B1 |
9297638 | Dyer | Mar 2016 | B1 |
20120068158 | Komiyama | Mar 2012 | A1 |
20130026442 | Kim | Jan 2013 | A1 |
20140021446 | Lee | Jan 2014 | A1 |
20140224989 | Long | Aug 2014 | A1 |
20140346357 | Jarrahi | Nov 2014 | A1 |
20150162993 | Akyildiz | Jun 2015 | A1 |
20150369660 | Yu | Dec 2015 | A1 |
20150369928 | Reese | Dec 2015 | A1 |
20160111180 | Joo | Apr 2016 | A1 |
20160161340 | Colli | Jun 2016 | A1 |
20160172527 | Beechem, III | Jun 2016 | A1 |
20170227797 | Long | Aug 2017 | A1 |
Entry |
---|
K. F. Mak, L. Ju, F. Wang, and T. F. Heinz, “Optical spectroscopy of graphene: From the far infrared to the ultraviolet,” Solid State Communications, vol. 152, pp. 1341-1349, Aug. 2012. |
S. Bae, H. Kim, Y. Lee, X. F. Xu, J. S. Park, Y. Zheng, et al., “Roll-to-roll production of 30-inch graphene films for transparent electrodes,” Nature Nanotechnology, vol. 5, pp. 574-578, Aug. 2010. |
F. N. Xia, T. Mueller, Y. M. Lin, A. Valdes-Garcia, and P. Avouris, “Ultrafast graphene photodetector,” Nature Nanotechnology, vol. 4, pp. 839-843, Dec. 2009. |
T. Mueller, F. N. A. Xia, and P. Avouris, “Graphene photodetectors for high-speed optical communications,” Nature Photonics, vol. 4, pp. 297-301, May 2010. |
A. Urich, K. Unterrainer, and T. Mueller, “Intrinsic Response Time of Graphene Photodetectors,” Nano Letters, vol. 11, pp. 2804-2808, Jul. 2011. |
S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, et al., “Carrier Relaxation in Epitaxial Graphene Photoexcited Near the Dirac Point,” Physical Review Letters, vol. 107, Nov. 28, 2011. |
J. M. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana, and M. G. Spencer, “Measurement of ultrafast carrier dynamics in epitaxial graphene,” Applied Physics Letters, vol. 92, Jan. 28, 2008. |
Y. Yao, M. A. Kats, P. Genevet, N. Yu, Y. Song, J. Kong, et al., “Broad electrical tuning of graphene-loaded plasmonic antennas,” Nano letters, vol. 13, pp. 1257-1264, 2013. |
Y. Yao, M. A. Kats, R. Shankar, Y. Song, J. Kong, M. Loncar, et al., “Wide wavelength tuning of optical antennas on graphene with nanosecond response time,” Nano letters, vol. 14, pp. 214-219, 2013. |
Y. Yao, R. Shankar, M. A. Kats, Y. Song, J. Kong, M. Loncar, et al., “Electrically Tunable Metasurface Perfect Absorbers for Ultrathin Mid-Infrared Optical Modulators,” Nano Letters, vol. 14, pp. 6526-6532, 2014. |
Y. Yao, R. Shankar, P. Rauter, Y. Song, J. Kong, M. Loncar, et al., “High-responsivity mid-infrared graphene detectors with antenna-enhanced photocarrier generation and collection,” Nano letters, vol. 14, pp. 3749-3754, 2014. |
C. Dean, A. Young, I. Meric, C. Lee, L. Wang, S. Sorgenfrei, et al., “Boron nitride substrates for high-quality graphene electronics,” Nature nanotechnology, vol. 5, pp. 722-726, 2010. |
W. Liu, S. Kraemer, D. Sarkar, H. Li, P. M. Ajayan, and K. Banerjee, “Controllable and rapid synthesis of high-quality and large-area Bernal stacked bilayer graphene using chemical vapor deposition,” Chemistry of Materials, vol. 26, pp. 907-915, 2013. |
S. Najmaei, Z. Liu, W. Zhou, X. Zou, G. Shi, S. Lei, et al., “Vapour phase growth and grain boundary structure of molybdenum disulphide atomic layers,” Nature materials, vol. 12, pp. 754-759, 2013. |
Z. Liu, Y. Gong, W. Zhou, L. Ma, J. Yu, J. C. Idrobo, et al., “Ultrathin high-temperature oxidation-resistant coatings of hexagonal boron nitride,” Nature communications, vol. 4, 2013. |
Z. Liu, L. Song, S. Zhao, J. Huang, L. Ma, J. Zhang, et al., “Direct growth of graphene/hexagonal boron nitride stacked layers,” Nano letters, vol. 11, pp. 2032-2037, 2011. |
L. Ci, L. Song, C. Jin, D. Jariwala, D. Wu, Y. Li, et al., “Atomic layers of hybridized boron nitride and graphene domains,” Nature materials, vol. 9, pp. 430-435, 2010. |
Z. Liu, L. Ma, G. Shi, W. Zhou, Y. Gong, S. Lei, et al., “In-plane heterostructures of graphene and hexagonal boron nitride with controlled domain sizes,” Nature nanotechnology, vol. 8, pp. 119-124, 2013. |
Y. Yao, M. Kats, P. Genevet, N. Yu, Y. Song, J. Kong, et al., “Broad electrical tuning of graphene-loaded plasmonic antennas,” Nano letters, 2013. |
G. Giovannetti, P. Khomyakov, G. Brocks, V. Karpan, J. Van den Brink, and P. Kelly, “Doping graphene with metal contacts,” Physical Review Letters, vol. 101, p. 026803, 2008. |
T. Mueller, F. Xia, and P. Avouris, “Graphene photodetectors for high-speed optical communications,” Nature Photonics, vol. 4, pp. 297-301, 2010. |
M. P. Levendorf, C.-J. Kim, L. Brown, P. Y. Huang, R. W. Havener, D. A. Muller, et al., “Graphene and boron nitride lateral heterostructures for atomically thin circuitry,” Nature, vol. 488, pp. 627-632, 2012. |
A. Mishchenko, J. Tu, Y. Cao, R. Gorbachev, J. Wallbank, M. Greenaway, et al., “Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures,” Nature nanotechnology, vol. 9, pp. 808-813, 2014. |
N. Myoung, K. Seo, S. J. Lee, and G. Ihm, “Large current modulation and spin-dependent tunneling of vertical graphene/MoS2 heterostructures,” Acs Nano, vol. 7, pp. 7021-7027, 2013. |
T. Niu and A. Li, “From two-dimensional materials to heterostructures,” Progress in Surface Science, vol. 90, pp. 21-45, Feb. 2015. |
Z. Liu, Y. J. Gong, W. Zhou, L. L. Ma, J. J. Yu, J. C. Idrobo, et al., “Ultrathin high-temperature oxidation-resistant coatings of hexagonal boron nitride,” Nature Communications, vol. 4, Oct. 2013. |
Y. Gong, G. Shi, Z. Zhang, W. Zhou, J. Jung, W. Gao, et al., “Direct chemical conversion of graphene to boron- and nitrogen- and carbon-containing atomic layers,” Nature communications, vol. 5, 2014. |
Y. Yao, R. Shankar, M. A. Kats, Y. Song, J. Kong, M. Loncar, et al., “Electrically Tunable Metasurface Perfect Absorbers for Ultrathin Mid-Infrared Optical Modulators,” Nano Letters, 2014. |
A. Yariv, “Critical coupling and its control in optical waveguide-ring resonator systems,” Ieee Photonics Technology Letters, vol. 14, pp. 483-485, Apr. 2002. |
M. A. Kats, R. Blanchard, P. Genevet, and F. Capasso, “Nanometre optical coatings based on strong interference effects in highly absorbing media,” Nature Materials, vol. 12, pp. 20-24, Jan. 2013. |
M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, et al., “Ultra-thin perfect absorber employing a tunable phase change material,” Applied Physics Letters, vol. 101, Nov. 26, 2012. |
M. A. Kats, R. Blanchard, S. Ramanathan, and F. Capasso, “Thin-Film Interference in Lossy, Ultra-Thin Layers,” Optics and Photonics News, vol. 25, pp. 44-47, 2014. |
H. Dotan, O. Kfir, E. Sharlin, O. Blank, M. Gross, I. Dumchin, et al., “Resonant light trapping in ultrathin films for water splitting,” Nature Materials, vol. 12, pp. 158-164, Feb. 2013. |
N. Yu and F. Capasso, “Flat optics with designer metasurfaces,” Nature materials, vol. 13, pp. 139-150, 2014. |
F. Aieta, P. Genevet, M. A. Kats, N. Yu, R. Blanchard, Z. Gaburro, et al., “Aberration-free ultrathin flat lenses and axicons at telecom wavelengths based on plasmonic metasurfaces,” Nano letters, vol. 12, pp. 4932-4936, 2012. |
F. Aieta, M. A. Kats, P. Genevet, and F. Capasso, “Multiwavelength achromatic metasurfaces by dispersive phase compensation,” Science, vol. 347, pp. 1342-1345, 2015. |
M. Khorasaninejad, F. Aieta, P. Kanhaiya, M. A. Kats, P. Genevet, D. Rousso, et al., “Achromatic metasurface lens at telecommunication wavelengths,” Nano letters, vol. 15, pp. 5358-5362, 2015. |
G. Giovannetti, P. A. Khomyakov, G. Brocks, V. M. Karpan, J. van den Brink, and P. J. Kelly, “Doping graphene with metal contacts,” Physical Review Letters, vol. 101, Jul. 11, 2008. |
I. Meric, M. Y. Han, A. F. Young, B. Ozyilmaz, P. Kim, and K. L. Shepard, “Current saturation in zero-bandgap, top-gated graphene field-effect transistors,” Nature nanotechnology, vol. 3, pp. 654-659, 2008. |
L. Britnell, R. Gorbachev, A. Geim, L. Ponomarenko, A. Mishchenko, M. Greenaway, et al., “Resonant tunnelling and negative differential conductance in graphene transistors,” Nature communications, vol. 4, p. 1794, 2013. |
Y. Yao, Quantum cascade lasers with extended spectral range and tunability, 2011. |
G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. P. G. de Arquer, et al., “Hybrid graphene-quantum dot phototransistors with ultrahigh gain,” Nature nanotechnology, vol. 7, pp. 363-368, 2012. |
P. Giannozzi, S. Baroni, N. Bonini, M. Calandra, R. Car, C. Cavazzoni, et al., “Quantum Espresso: a modular and open-source software project for quantum simulations of materials,” Journal of Physics: Condensed Matter, vol. 21, p. 395502, 2009. |
M. Saraniti and S. M. Goodnick, “Hybrid fullband cellular automaton/Monte Carlo approach for fast simulation of charge transport in semiconductors,” Electron Devices, IEEE Transactions on, vol. 47, pp. 1909-1916, 2000. |
R. Hathwar, M. Saraniti, and S. Goodnick, “Full band Monte Carlo simulation of In 0.7 Ga 0.3 As junctionless nanowire field effect transistors,” in Nanotechnology (IEEE-NANO), 2014 IEEE 14th International Conference on, 2014, pp. 645-649. |
R. Shishir, D. Ferry, and S. Goodnick, “Room temperature velocity saturation in intrinsic graphene,” in Journal of Physics: Conference Series, 2009, p. 012118. |
S.-J. Han, A. V. Garcia, S. Oida, K. A. Jenkins, and W. Haensch, “Graphene radio frequency receiver integrated circuit,” Nature communications, vol. 5, 2014. |
Y.-M. Lin, A. Valdes-Garcia, S.-J. Han, D. B. Farmer, I. Meric, Y. Sun, et al., “Wafer-scale graphene integrated circuit,” Science, vol. 332, pp. 1294-1297, 2011. |
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20170301819 A1 | Oct 2017 | US |
Number | Date | Country | |
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62323133 | Apr 2016 | US |