High-Responsivity GrapheneâBoron Nitride Photodetector and

Subscriber access provided by CMU Libraries - http://library.cmich.edu

Communication

High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit Ren-Jye Shiue, Yuanda Gao, Yifei Wang, Cheng Peng, Alexander D. Robertson, Dmitri Efetov, Solomon Assefa, Frank H.L. Koppens, James Hone, and Dirk Englund Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.5b02368 • Publication Date (Web): 15 Sep 2015 Downloaded from http://pubs.acs.org on September 16, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Nano Letters is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

High-Responsivity Graphene-Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit Ren-Jye Shiue,∗,†,k Yuanda Gao,‡,k Yifei Wang,†,k Cheng Peng,† Alexander D. Robertson,‡ Dmitri K. Efetov,† Solomon Assefa,¶ Frank H. L. Koppens,§ James Hone,‡ and Dirk Englund∗,† †Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology ‡Department of Mechanical Engineering, Columbia University ¶IBM T. J. Watson Research Center §ICFO - Institut de Ciencies Fotoniques kThese authors contribute equally to this work E-mail: [email protected]; [email protected]

Keywords: Graphene, Photodetectors, Optoelectronics, Silicon photonics, Autocorrelators, Boron nitride 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

1

ACS Paragon Plus Environment

Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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 0.36 A/W and high-speed operation with a 3 dB cut-off 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 photoresponse enables optical on-chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers.

The past decades have seen concerted efforts to combine optical and electrical components into integrated optoelectronic circuits for a variety of applications, including optical interconnects, 1–3 biochemical sensing, 4 and all-optical signal processing. 5 The leading photodetector architectures for photonic integrated circuits (PICs), are presently based on bulk semiconductor materials, predominantly Ge 6 and InP. 7 However, the integration of bulk semiconductor-based on-chip detectors has faced important challenges, including in some cases front-end changes in complementary metal-oxide-semiconductor (CMOS) processing, a spectral response limited by the material’s bandgap—e.g. up to the L telecommunication band for strained Ge—and an intrinsic speed limited by the material’s carrier mobility. In addition, because of the weak nonlinear optical response of these bulk semiconductor materials, high optical powers are required in nonlinear applications including optical pulse characterization, sampling, and signal processing. 8–10 Recently, the family of two-dimensional (2D) materials has emerged as an alternative optoelectronic platform with new functionalities, 11,12 including broadband ultrafast photodetection, 13–17 on-chip electro-optic modulation, 18–21 light emission, 22,23 saturable absorption, 24 and parametric nonlinearities. 25–27 Moreover, distinct 2D materials can be assembled nearly defect-free into entirely new types of 2D heterostructures, 28,29 enabling optoelectronic properties and device concepts that were

2


Page 2 of 21

Page 3 of 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

not feasible using bulk semiconductors. Here, we introduce a 2D heterostructure consisting of single-layer graphene (SLG) encapsulated by hexagonal boron nitride (hBN) that enables both high-responsivity photodetection and ultrafast pulse metrology in a compact waveguide-integrated design. The mobility of BN-encapsulated graphene can reach up to 80,000 cm2 /Vs at room temperature, exceeding that of traditional semiconductors such as Ge by 1-3 orders of magnitude. We use one-dimensional contacts to the hBN/SLG/hBN stack combined with a wide channel design to achieve a device resistance as low as ∼ 77 Ω. We measure operating speeds exceeding 40 GHz (3dB cut-off) and a record-high detection responsivity exceeding 350 mA/W, approaching responsivities of on-chip Si-Ge photodetectors. 6 We fabricated this 2D heterostructure in a back-end-of-the-line (BEOL) step on a silicon-on-oxide (SOI) PIC, which was fabricated in a CMOS-compatible process. The strong electron-electron interaction and weak electron-phonon coupling of the SLG 30–32 result in a nonlinear photoresponse above ∼ 50 mW of peak input power, enabling direct autocorrelation characterization of ultrafast pulses. Unlike traditional free-space autocorrelators, optical nonlinear time-lens techniques, 33 and frequency-resolved optical gating (FROG), 34,35 this on-chip 2D heterostructure-based autocorrelator does not require parametric nonlinear effects, passive dispersive optics, or separate photodetectors. We measured a minimum timing resolution of 3 ps with a minimum required peak power of 67 mW, comparable to autocorrelators based on two-photon absorption (TPA) of silicon or III-V compound semiconductors, though TPA-based autocorrelators must be orders of magnitude longer than the graphene detector. 36 The ability for high responsivity photodetection and ultrafast optical autocorrelation in one small-footprint device opens the door to new applications and device concepts in integrated optics. Fig. 1a illustrates the device architecture. Silicon waveguides were fabricated in an SOI wafer with a 220 nm silicon membrane on a 3-µm-thick SiO2 layer. This step used shallow trench isolation (STI) commonly used in CMOS processing. A waveguide width of 520 nm supports a single transverse-electric (TE) mode shown in the simulated mode

3


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment

Page 4 of 21

Page 5 of 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

in Fig. 1a (lower right panel). The chip was planarized by backfilling with a thick SiO2 layer, followed by chemical mechanical polishing to reach the top silicon surface. We then transferred the multilayered hBN/SLG/hBN stack onto the photonic chip using van der Waals (vdW) assembly. 28 The graphene channel spans 40 µm of the waveguide. We applied one-dimensional edge contacts to the encapsulated graphene layer using a series of etching and metallization steps. 28 A polymer electrolyte (poly(ethylene oxide) and LiClO4 ) layer was spin-coated on the entire chip to gate the graphene device. 37 Fig. 1b shows the completed structure. The drain electrode is positioned only 200 nm from the waveguide to induce a pn junction near the optical mode. 38 Confocal scanning beam excitation measurements confirm a strong photoresponse region near this metal/graphene interface, as demonstrated previously 39 and shown for this particular device in Fig. S1 in the supporting information. Measurements of the device resistance as a function of gate voltage, shown in Fig. 1c, indicate a charge neutrality point (CNP) at a gate-source voltage of VGS = 2 V and a minimum device resistance of 77 Ω. From similar hBN/SLG/hBN stacks assembled on SiO2 substrates, which also included a Hall-bar geometry that was not possible for us to include on the waveguide-integrated device, the mobility of graphene is in the range of 40,000–60,000 cm2 /V·s at carrier densities between 2–4×1012 cm−2 . 28 We characterized the transmission of the completed device in the telecommunications band at 1550 nm, using lensed fibers for edge-coupling to SiN mode converters at the input and output of the ∼ 4-mm-long Si waveguide, as reported previously. 39 The hBN/SLG/hBN detector stack is located at the center of the waveguide, ∼ 2 mm from either edge facet. Depositing the stack increased the waveguide transmission loss from 11 dB to 13.2 dB. Attributing this 2.2 dB excess loss to the 40-µm-long graphene-waveguide overlap, we calculate an absorption coefficient of 0.055 dB/µm. This coefficient is slightly higher than the absorption of 0.043 dB/µm that we estimated independently from a finite element simulation of the waveguide evanescent field coupling to the SLG 39 (note that the hBN is transparent in the telecom band since it has a bandgap of 5.2 eV). We attribute the slightly higher

5


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

loss (0.48 dB) of the experimental device to additional scattering and reflection losses at the waveguide-detector stack interface. We observed negligible transmission loss from the electrolyte. Fig. 2a presents responsivity measurements as a function of VGS and VDS when the detector is illuminated via the waveguide at 25 µW continuous-wave (c.w.) laser inside the waveguide. Here the responsivity is defined as the ratio of the short-circuit photocurrent (supporting information) to the optical power in the waveguide, R = Iph /Pin . Unlike previous waveguide-integrated graphene photodetectors, which included only drain-source voltage control, 38–40 the additional top electrolyte-gate allows us to independently tune the graphene Fermi level and electric field across the waveguide mode. Scanning VGS and VDS produces a six-fold pattern in the photocurrent, which qualitatively matches the behavior of the photothermoelectric (PTE) effect. 30,41 The photocurrent reaches a maximum of 0.36 A/W at VGS = 2 V and VDS = 1.2 V; this represents a more than three-fold improvement over previous waveguide-integrated graphene photodetectors. 38–40

6


Page 6 of 21

Page 7 of 21

Nano Letters


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 21

contacts is given by

IP h = G

Z

L

S(x)∇Tel (x)dx

(1)

0

where G is the conductance of graphene and L the is length of the graphene channel. From the Mott formula, 30,42–44 S can be expressed as

S(µ) = −

2 π 2 kB T 1 dσ 3e σ dµ′

(2)

where kB is the Boltzmann constant, T is the lattice temperature, e is the electron charge, σ is the conductivity of graphene, and µ is the chemical potential. Eq. 2 indicates that S depends strongly on the carrier density and the chemical potential of graphene, which can be tuned by VGS and VDS in our device. Fig. 2c and 2d show examples of the spatially resolved S(x) using parameters obtained from the measured conductance and the capacitance of the electrolyte (supporting information). By integrating S(x) and ∇Tel along the source and drain contacts using Eq. 1, we can therefore calculate the photocurrent with respect to VGS and VDS , producing the photocurrent mapping in Fig. 2b, which shows a six-fold pattern qualitatively similar to the measured gate- and bias-dependent responsivity. From Fig. 2bd, the photoresponse is maximized when the integral of Eq. 1 is maximized at specific VGS and VDS voltages. Therefore, tuning VGS and VDS in our device allows us to optimize the responsivity compared with previous works without VGS tuning. 38–40 It is also important to consider photovoltaic (PV) effects that generate photocurrent at the graphene p−n junction. However, the PV effect only produces a single sign reversal with respect to VGS and VDS and does not agree to the measured six-fold pattern in the experiment. 30,43,44 We therefore estimate the PV effect to be small compared with the PTE, which is confirmed by theoretical approximations presented in the supporting information. To test the dynamic response of the hBN/SLG/hBN detector, we coupled two narrowband (1 MHz) laser sources with a detuning frequency ∆f ranging from 1 to 50 GHz into the

8


Page 9 of 21

waveguide. The interference of these two laser fields produces an intensity in the detector that oscillates at frequency ∆f . Fig.3a displays the measured power at ∆f , obtained on an electrical spectrum analyzer (maximum frequency 50 GHz) via high-speed RF probes (Cascade FPC-GS-150). This measurement indicates a 3-dB cutoff frequency at 42 GHz, matching the highest reported graphene photodetector speeds. 16 We observed this ultrafast photoresponse even under zero drain-source bias, which distinguishes graphene from typical semiconductor high-speed photodiodes. 6 The detected photocurrent at VDS = 0 (Fig. 3b) linearly reduces with input power, indicating vanishing dark current. The responsivity at VDS = 0 reaches 78 mA/W. The internal quantum efficiency (IQE) of the detector, defined as the number of generated charge carriers normalized by the absorbed photon number, can be expressed as IQE = 1.24/λ[µm]×R/Ag , where R is the responsivity of the detector, λ is the input laser wavelength, and Ag is the absorption of graphene. Accounting for the fact that the graphene absorbs ∼ 33 − 40% (1.7 − 2.2 dB) of the optical power in the waveguide at 1550 nm, we can thus estimate an IQE of 16 − 19% at VDS = 0 and a maximum IQE of 72 − 87% at maximum responsivity (0.36 A/W). As shown in Fig. 3c, the spectral response of the detector under c.w. laser excitation varies uniformly in the spectral range from 1510 nm to 1570 nm.

(a)

(b)

!42 !44

VDS = VGS = 0 V

78 mAW-1

!1

10

VDS = 0 V VGS = 2.9 V !2

10

!48 0 10

1

10

Frequency (GHz)

2

10

!4

!3

10

10

Power (mW)

Photocurrent (a.u.)

Photocurrent (!A)

!40

!46

(c) 1

!38

Response (dBm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

0.8 0.6 0.4 0.2 0

1520

1540

1560

Wavelength (nm)

Figure 3: (a) High-speed response of the graphene photodetector. The red dashed line shows the fitting to the experiment results with a RC low-pass filter model. The extracted 3 dB cut-off frequency is at 42 GHz. (b) Photocurrent as a function of input optical power. (c) Spectral response of the normalized photocurrent for c.w. laser excitation.

9


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

We next tested the detector using 250-fs pulses at 1800 nm, produced by an optical parametric oscillator pumped by a Ti:Sapphire oscillator with 78 MHz repetition rate. As shown in Fig. 4a, the photocurrent shows a nonlinear photoresponse that is fit well by 0.47±0.003 IP h ∝ Pin . This approximately square root dependence in photocurrent with pump √ power suggests a supercollision-dominated cooling mechanism, for which IP h ∝ Pin . 32

Using this nonlinear photoresponse, we characterized our photodetector’s ultimate speed limitations, which are dictated by the internal carrier dynamics. Fig. 4b plots photocurrent traces as a function of the time delay ∆t between pairs of 250-fs laser pulses for a range of incident powers. These traces show a clear dip at ∆t = 0 with a width that corresponds to the carrier relaxation time, i.e., the time needed for the graphene detector to return to equilibrium. The half-width at half-maximum response times τ are plotted in Fig. 4c for a sweep of input powers. The minimum response time is approximately ∼ 3 ps. The slight increase of the response time at higher input power is unclear to us at this point and requires future studies. The picosecond-scale nonlinear photocurrent from the photodetector can be used for on-chip autocorrelation measurements for, e.g., ultrafast optical sampling. We tested the autocorrelator with an average power of only 1.4 µW (peak power of 67 mW) in the waveguide. The autocorrelation trace (Fig. 4d) shows a clear dip with a minimum resolution down to 3 ps. With optimized coupling efficiency (> 80%) from optical fibers to waveguides, 45 our on-chip autocorrelator would require a lower peak power than free-space autocorrelators based on parametric frequency conversion

46

and is comparable to TPA-based semiconduc-

tor autocorrelators with waveguide integration, though these require more than 10 mm of waveguide length 36,47,48 compared with the 40 µm length of the graphene device. We noticed that the femtosecond-scale heating of the hot-electrons in graphene in a recent report could in principle improve the timing resolution of the on-chip autocorrelator to sub-50 fs. 17 It is also important to note that this graphene-based autocorrelator supports a broad spectral range that is identical to the spectral response of the graphene detector, which, in this work,

10


Page 10 of 21

Page 11 of 21

Nano Letters


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

photonic integrated circuits for ultrafast measurements, mode-locking, and other high-speed optoelectronic applications.

Acknowledgement The authors thank Prof. Xuetao Gan for helpful discussion on the experiment scheme and data analysis. Financial support was provided by the Office of Naval Research (Awards N00014-13-1-0662 and N00014-14-1-0349). Device fabrication was partly carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the US Department of Energy, Office of Basic Energy Sciences (contract no. DE-AC0298CH10886). R.-J.S. was supported in part by the Center for Excitonics, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under award no. DE-SC0001088. YF. W. was supported in part by Tsinghua Xuetang Talents Program.

Supporting Information Available Electrical measurement setup, spatial photocurrent mapping of the graphene detector, modeling of PTE effects, experimental setup of the autocorrelation measurement and the characterization of TPA effects in silicon. This material is available free of charge via the Internet at http://pubs.acs.org/.

Notes and References (1) Hochberg, M.; Baehr-Jones, T. Nature Photonics 2010, 4, 492–494. (2) Miller, D. A. B. Proceedings of the IEEE 2009, 97, 1166–1185.

12


Page 12 of 21

Page 13 of 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

(3) Bergman, K.; Carloni, L. P.; Biberman, A.; Chan, J.; Hendry, G. Photonic Networkon-Chip Design; Springer, 2014. (4) Estevez, M.; Alvarez, M.; Lechuga, L. Laser & Photonics Reviews 2012, 6, 463–487. (5) Wabnitz, S.; Eggleton, B. J. All-Optical Signal Processing: Data Communication and Storage Applications; Springer, 2015; Vol. 194. (6) Wang, J.; Lee, S. Sensors (Basel, Switzerland) 2011, 11, 696–718. (7) Liang, D.; Roelkens, G.; Baets, R.; Bowers, J. E. Materials 2010, 3, 1782–1802. (8) Slav´ık, R. et al. Nature Photonics 2010, 4, 690–695. (9) Ferdous, F.; Miao, H.; Leaird, D. E.; Srinivasan, K.; Wang, J.; Chen, L.; Varghese, L. T.; Weiner, A. M. Nature Photonics 2011, 5, 770–776. (10) Weiner, A. M. Review of Scientific Instruments 2000, 71, 1929. (11) Koppens, F. H. L.; Mueller, T.; Avouris, P.; Ferrari, a. C.; Vitiello, M. S.; Polini, M. Nature Nanotechnology 2014, 9, 780–793. (12) Avouris, P.; Freitag, M. IEEE Journal of Selected Topics in Quantum Electronics 2014, 20, 6000112–6000112. (13) Xia, F.; Wang, H.; Xiao, D.; Dubey, M.; Ramasubramaniam, A. Nature Photonics 2014, 8, 899–907. (14) Gan, X.; Shiue, R.-J.; Gao, Y.; Assefa, S.; Hone, J.; Englund, D. Selected Topics in Quantum Electronics, IEEE Journal of 2013, 20, 6000311–6000311. (15) Youngblood, N.; Chen, C.; Koester, S. J.; Li, M. Nature Photonics 2015, 9, 247–252. (16) Schall, D.; Neumaier, D.; Mohsin, M.; Chmielak, B.; Bolten, J.; Porschatis, C.; Prinzen, A.; Matheisen, C.; Kuebart, W.; Junginger, B.; Templ, W.; Giesecke, A. L.; Kurz, H. ACS Photonics 2014, 1, 781–784. 13


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(17) Tielrooij, K. J.; Piatkowski, L.; Massicotte, M.; Woessner, a.; Ma, Q.; Lee, Y.; Myhro, K. S.; Lau, C. N.; Jarillo-Herrero, P.; van Hulst, N. F.; Koppens, F. H. L. Nature Nanotechnology 2015, 10, 437–443. (18) Liu, M.; Yin, X.; Ulin-Avila, E.; Geng, B.; Zentgraf, T.; Ju, L.; Wang, F.; Zhang, X. Nature 2011, 474, 64–67. (19) Gao, Y.; Shiue, R.-J.; Gan, X.; Li, L.; Peng, C.; Meric, I.; Wang, L.; Szep, A.; Walker, D.; Hone, J.; Englund, D. Nano Letters 2015, 15, 2001–2005, PMID: 25700231. (20) Phare, C. T.; Daniel Lee, Y.-H.; Cardenas, J.; Lipson, M. Nature Photonics 2015, 9, 511–514. (21) Hu, Y. T.; Pantouvaki, M.; Brems, S.; Asselberghs, I.; Huyghebaert, C.; Geisler, M.; Alessandri, C.; Baets, R.; Absil, P.; Van Thourhout, D.; Van Campenhout, J. Broadband 10Gb/s graphene electro-absorption modulator on silicon for chip-level optical interconnects. 2014 IEEE International Electron Devices Meeting. 2014; pp 5.6.1–5.6.4. (22) Baugher, B. W. H.; Churchill, H. O. H.; Yang, Y.; Jarillo-Herrero, P. Nature nanotechnology 2014, 9, 262–7. (23) Pospischil, A.; Furchi, M. M.; Mueller, T. Nature nanotechnology 2014, 9, 257–61. (24) Sun, Z.; Hasan, T.; Torrisi, F.; Popa, D.; Privitera, G.; Wang, F.; Bonaccorso, F.; Basko, D. M.; Ferrari, A. C. ACS Nano 2010, 4, 803–810. (25) Gu, T.; Petrone, N.; Mcmillan, J. F.; Zande, A. V. D.; Yu, M.; Lo, G. Q.; Kwong, D. L.; Hone, J.; Wong, C. W. Nature photonics 2012, 43, 1–6. (26) Hendry, E.; Hale, P. J.; Moger, J.; Savchenko, A. K.; Mikhailov, S. A. Physical Review Letters 2010, 105, 097401. (27) Gullans, M.; Chang, D.; Koppens, F.; de Abajo, F.; Lukin, M. Physical Review Letters 2013, 111, 247401. 14


Page 14 of 21

Page 15 of 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

(28) Wang, L.; Meric, I.; Huang, P. Y.; Gao, Q.; Gao, Y.; Tran, H.; Taniguchi, T.; Watanabe, K.; Campos, L. M.; Muller, D. a.; Guo, J.; Kim, P.; Hone, J.; Shepard, K. L.; Dean, C. R. Science (New York, N.Y.) 2013, 342, 614–7. (29) Geim, A. K.; Grigorieva, I. V. Nature 2013, 499, 419–25. (30) Song, J. C. W.; Rudner, M. S.; Marcus, C. M.; Levitov, L. S. Nano letters 2011, 11, 4688–4692. (31) Song, J. C. W.; Reizer, M. Y.; Levitov, L. S. Physical Review Letters 2012, 109, 106602. (32) Graham, M. W.; Shi, S.-F.; Ralph, D. C.; Park, J.; McEuen, P. L. Nature Physics 2012, 9, 103–108. (33) Foster, M. a.; Salem, R.; Geraghty, D. F.; Turner-Foster, A. C.; Lipson, M.; Gaeta, A. L. Nature 2008, 456, 81–4. (34) Tien, E.-K.; Sang, X.-Z.; Qing, F.; Song, Q.; Boyraz, O. Applied Physics Letters 2009, 95, 051101. (35) Walmsley, I. A.; Dorrer, C. Advances in Optics and Photonics 2009, 1, 308. (36) Liang, T. K.; Tsang, H. K.; Day, I. E.; Drake, J.; Knights, A. P.; Asghari, M. Applied Physics Letters 2002, 81, 1323. (37) Lu, C.; Fu, Q.; Huang, S.; Liu, J. Nano Letters 2004, 4, 623–627. (38) Pospischil, A.; Humer, M.; Furchi, M. M.; Bachmann, D.; Guider, R.; Fromherz, T.; Mueller, T. Nature Photonics 2013, 7, 892–896. (39) Gan, X.; Shiue, R.-J.; Gao, Y.; Meric, I.; Heinz, T. F.; Shepard, K.; Hone, J.; Assefa, S.; Englund, D. Nature Photonics 2013, 7, 883–887. (40) Wang, X.; Cheng, Z.; Xu, K.; Tsang, H. K.; Xu, J.-B. Nature Photonics 2013, 7, 888–891. 15


Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(41) Gabor, N. M.; Song, J. C. W.; Ma, Q.; Nair, N. L.; Taychatanapat, T.; Watanabe, K.; Taniguchi, T.; Levitov, L. S.; Jarillo-Herrero, P. Science (New York, N.Y.) 2011, 334, 648–52. (42) Ashcroft, N. W.; Mermin, N. D. Solid State Physics; Holt, Rinehart and Winston, 1976; p 826. (43) Liu, C.-H.; Dissanayake, N. M.; Lee, S.; Lee, K.; Zhong, Z. ACS nano 2012, 6, 7172–6. (44) Lemme, M. C.; Koppens, F. H. L.; Falk, A. L.; Rudner, M. S.; Park, H.; Levitov, L. S.; Marcus, C. M. Nano letters 2011, 11, 4134–4137. (45) Cardenas, J.; Poitras, C. B.; Luke, K.; Luo, L.-W.; Morton, P. A.; Lipson, M. IEEE Photonics Technology Letters 2014, 26, 2380–2382. (46) Reef femtosecond autocorrelator Reef-RTD and Femtochrome Research Inc. FR103WS. (47) Hayat, A.; Nevet, A.; Ginzburg, P.; Orenstein, M. Semiconductor Science and Technology 2011, 26, 083001. (48) Duchesne, D.; Razzari, L.; Halloran, L.; Morandotti, R.; SpringThorpe, A. J.; Christodoulides, D. N.; Moss, D. J. Two-Photon Detection in a MQW GaAs Laser at 1.55µm. Conference on Lasers and Electro-Optics/International Quantum Electronics Conference. Washington, D.C., 2009; p IMH5.

16


Page 16 of 21

Page 17 of 21

(a)

Graphene

Gate Source

Si

hBN SLG cross-section hBN

Drain

Waveguide

Graphene Si

SiO2

(b)

(c) 10 μm 100

1 um

Waveguide

Au BN/SLG/BN

Resistance (Ω)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

95 90 85 80 75


−4

−2

0

VGS (V)

2

4

6

Nano Letters

Responsivity (A/W)

Responsivity (a.u.)

(b)

VDS (V)

VDS (V)

(a)

VGS (V) 1

0.5 0 100 0 −100 −3

−2

−1

0

x (µm)

1

VGS (V)

(d)

2

3

S (µV/K) Tel (a.u.)

(c) S (µV/K) Tel (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 21

1 0.5 0

100 0 −100 −3


−2

−1

0

x (µm)

1

2

3

Page 19 of 21

(b)

1

−38 −40 −42 −44 −46

(c)

VDS = VGS = 0 V

78

−1

10

mAW-1

VDS = 0 V VGS = 2.9 V −2

10

−48 0 10

1

10

Frequency (GHz)

2

10

−4

10

−3

10

Power (mW)


Photocurrent (a.u.)

Response (dBm)

(a)

Photocurrent (μA)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

0.8 0.6 0.4 0.2 0

1520

1540

1560

Wavelength (nm)

Nano Letters

(a)

(b)

(c) 5

200 150 100 50 0 0

2

4

6

(ps)

Photocurrent (nA)

Photocurrent (nA)

250

200 150

(d)

100

1.5 W 1.2 W 0.81 W 0.57 W

−20

−10

0

10

20

IPhoto (nA)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 21

4 3 2 0

1

Delay (ps)


3

4

Peak power (W) 22 20 −20

Peak power (W)

2

−10

0

10

Delay (ps)

20

Page 21 of 21

Responsivity (A/W) hBN/Graphene/hBN

Gate

Drain Source

VDS (V)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

SiO2

Waveguide

Si ACS Paragon Plus Environment

VGS (V)

High-Responsivity GrapheneâBoron Nitride Photodetector and

Recommend Documents

High-Responsivity GrapheneâBoron Nitride Photodetector and