Silicon/2D-material photodetectors: from near-infrared to mid-infrared
doi: 10.1038/s41377-021-00551-4
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Abstract: Two-dimensional materials (2DMs) have been used widely in constructing photodetectors (PDs) because of their advantages in flexible integration and ultrabroad operation wavelength range. Specifically, 2DM PDs on silicon have attracted much attention because silicon microelectronics and silicon photonics have been developed successfully for many applications. 2DM PDs meet the imperious demand of silicon photonics on low-cost, high-performance, and broadband photodetection. In this work, a review is given for the recent progresses of Si/2DM PDs working in the wavelength band from near-infrared to mid-infrared, which are attractive for many applications. The operation mechanisms and the device configurations are summarized in the first part. The waveguide-integrated PDs and the surface-illuminated PDs are then reviewed in details, respectively. The discussion and outlook for 2DM PDs on silicon are finally given.
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Figure 1. Summary of the working mechanisms of 2DM PDs.
a–f Photon-type mechanisms: a The photovoltaic (PV) effect. The photo-excited e-h pairs driven by the built-in electric fields contribute to the photocurrents. b The internal photon emission (IPE) effect. For example, in a G-Si Schottky junction, the photo-excited hot carriers in graphene emitted over the Schottky barrier contribute to the photocurrent. c The direct tunneling (DT). d The Fowler-Nordheim (F-N) tunneling. e The photoconductive (PC) effect. The carrier density increment leads to the change of channel conductivity in a phototransistor. f The photo-gating (PG) effect. The photo-induced gating leads to the change of the channel conductivity in a phototransistor. g The thermal relaxation process in 2DMs. The carrier–carrier scattering results in the increment of the electron temperature Te, and then the optical/acoustic phonon emissions lead to the increment of lattice temperature TL. h, i Thermal-type mechanisms: h The bolometric (BOL) effect. The increment of Te or TL can be extracted by different read-outs. i The photo-thermoelectric (PTE) effect. Here Seebeck effect plays a major role. In the present example, S1 and S2 are respectively the positive and negative Seebeck coefficients.
Figure 2. The relation between the working mechanisms and the configurations of the 2DM PDs.
Both metal-2DM-metal and metal-2DM+X-metal configurations have a phototransistor structure featuring a 2DM channel. The former has a pure 2DM channel, while the latter has a 2DM channel contacted with another specific material "X", such as zero-dimensional (0D) quantum dots, 1D carbon nanotubes (CNTs), 2DMs, and even bulk materials. In the 2DM-heterostructure configuration, the electrodes are connected to different materials. PV photovoltaic, IPE internal photon emission, DT direct tunneling, F-N tunneling Fowler-Nordheim (F-N) tunneling, PC photoconductive, PG Photo-gating, BOL bolometric, PTE photo-thermoelectric, QDs quantum dots, CNT carbon nanotubes.
Figure 3. The waveguide-integrated Si/2DM PDs with metal-2DM-metal configurations.
a A graphene plasmonic PD working with the PV effect. b A plasmonically enhanced graphene PD working on the BOL effect. c A horizontally asymmetric graphene PD with one gate electrode based on the PTE effect. d A microring resonator-integrated two-gate graphene PD based on the PTE effect. e The Si-G hybrid plasmonic waveguide PDs operating at 1.55 and 2 μm. f A two-gate MoTe2 PD operating at 1.16 μm based on the PV effect. g A strain-engineered MoTe2 PD integrated on a microring resonator operating at 1.55 μm. h A PtSe2 PD operating at 1.55 μm. i A black-phosphorus PD operating at 1.55 μm with 3 GHz bandwidth. j A black-phosphorus PD operating at 2 μm. k A PG effect-based black phosphorus PD operating at the wavelength band of 3.68–4.03 μm. Figures reproduced with permissions from: a ref. 108, ©2020 De Gruyter, Berlin/Boston, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); b ref. 119, ©2018 American Chemical Society; c ref. 60, ©2015 American Chemical Society; d ref. 115, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); e ref. 58, ©2020 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); f ref. 64 ©2017 Springer Nature Limited. g ref. 70, ©2020 Springer Nature Limited; h ref. 121, ©2020 American Chemical Society; i ref. 71, ©2015 Springer Nature Limited; j ref. 72, ©2019 John Wiley & Sons, Inc. k ref. 68, ©2018 American Chemical Society. Further permissions related to the figures should be directed to the copyright holders.
Figure 4. The waveguide-integrated Si/2DM PDs with heterostructure configurations.
a A high-speed G-Si PD with p-i-n doping distributions for both Si and graphene. b A Si-G plasmonic Schottky photodetector. c A MoTe2-G heterostructure PD. d A G-hBN-G heterostructure PD. Figures reproduced with permissions from: a ref. 122, ©2018 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); b ref. 99, ©2016 American Chemical Society; c ref. 90, ©2020 Springer Nature Limited; d ref. 123; ©2019 The Optical Society, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/). Further permissions related to the figures should be directed to the copyright holders.
Figure 5. Performance summary for the waveguide-integrated Si/2DM PDs.
■: photovoltaic (PV) effect, ●: photo-thermoelectric (PTE) effect, ▲: bolometric (BOL) effect, ♦: photoconductive (PC) effect, : Photo-gating (PG) effect, ◄: tunneling effects, ►: internal photon emission.(IPE) effect; blue: metal-graphene-metal (M-G-M); green: metal-TMDC-metal; black: metal-BP-metal; red: 2DM-heterostructure
Figure 6. The surface-illuminated Si/2DM PDs with metal-2DM-metal configuration.
a A wide-band plasmonic enhanced graphene PD and the measured responsivity/photoconductive-gain. b A cavity-coupled graphene bolometer with Johnson noise read-out. Left: the 3D schematic. Right: the NEP and thermal relaxation time of hot electrons as a function of lattice temperature. c A metal-graphene+X-metal configuration PD, for which X is carbon nanotube. d A short-wave infrared graphene PD with a plasmonic enhanced structure on channel. e A ferroelectric polarization gating MoS2 photodetector with an operation wavelength extended to 1.55 μm. f A mid-infrared black-phosphorus PD with a high gain. g A mid-infrared black-phosphorus PD with an operation wavelength extended to 7.7 μm by applying a vertical electric field. Left: the 3D schematic. Right: the NEP and dark current at different wavelengths. h The specific detectivities of the mid-infrared black phosphorus PD and black-PAs-alloy PD as a function of wavelength. i A short-wave infrared tellurene PD. Figures reproduced with permissions from: a ref. 128, ©2018 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); b ref. 53, ©2018 Springer Nature Limited; c ref. 76, ©2015 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); d ref. 78, ©2017 American Chemical Society; e ref. 81. ©2015 John Wiley & Sons, Inc. f ref. 67, ©2016 American Chemical Society; g ref. 29, ©2017 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); h ref. 129, ©2017 American Chemical Society. i ref. 131, ©2019 American Chemical Society. Further permissions related to the figures should be directed to the copyright holders.
Figure 7. Surface-illuminated Si/2DM PDs with heterostructure configurations.
a A MoS2-G-WSe2 PD. b A G-WSe2-G PD with the IPE effect.c A colloidal quantum dot-graphene (CQD-G) hybrid PD with tunneling layer. d A G-Si heterostructure position-sensitive PD operating at near-infrared wavelengths. e A G-Si PD operating at 1.55 μm. f A G/vertical-MoSe2/Si heterojunction PD. g A mid-infrared WS2-HfS2 heterostructure PD based on interlayer excitons. h A mid-infrared BP-MoS2 heterostructure PD. i A mid-infrared BP-InSe avalanche photodetector. Figures reproduced with permissions from: a ref. 86, ©2016 American Chemical Society; b ref. 100, ©2016 Springer Nature Limited, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); c ref. 103, ©2020 American Chemical Society; d ref. 135, ©2018 The Optical Society, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); e ref. 136, ©2017 American Chemical Society; f ref. 139, ©2016 John Wiley & Sons, Inc, under Creative Commons Attribution 4.0 International license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); g ref. 13 ©2020 Springer Nature Limited. h ref. 94, ©2018 Springer Nature Limited; i ref. 97, ©2019 Springer Nature Limited. Further permissions related to the figures should be directed to the copyright holders.
Figure 8. The image sensors based on Si/2DM PDs.
a An image sensor array based on graphene-CMOS integration, covering ultraviolet, visible and infrared light. Left: the schematic of the graphene transfer process on wafer. Right: the schematic of the graphene/colloidal quantum dot PDs integrated with CMOS read-outs. b Concept of a focal stack light-field imaging system using graphene transparent PDs (inset). c An artificial neural network image-sensor based on a reconfigurable WSe2 PD array. Left: the schematic of the PD array. Right: the schematic of the single-element WSe2 PD. d A multispectral imaging system based on a black phosphorus PD. Figures reproduced with permissions from: a ref. 124, ©2017 Springer Nature Limited; b ref. 126, ©2020 Springer Nature Limited; c ref. 125, ©2020 Springer Nature Limited; d ref. 127, ©2014 American Chemical Society. Further permissions related to the figures should be directed to the copyright holders.
Table 1. Summary of waveguide-integrated Si/2DM PDs
Structure λ Mechanism Responsivity |Bias voltage| Bandwidtha Refs. M-G-M ~1.35 μm PV 0.2 A W−1 0.5 V – 106 BOL 0.67 A W−1 M-G-M ~1.55 μm PV 7–50b mA W−1 0 V 3–110 GHz 107, 109, 110, 111 57–108 mA W−1 1 V 360 mA W−1 2.2 V M-G-M ~1.55 μm PTE 35–78 mA W−1 0 V 12–67 GHz 60, 112, 114, 115, 116, 117 3.5–90 V W−1 M-G-M ~1.55 μm BOL 90–500 mA W−1 0.3–0.4 V 40–110 GHz 58, 119 M-G-M ~2 μm BOL 45–70 mA W−1 0.3 V 20 GHz 58 M-G-M ~3.8 μm No stated 2.2 mA W−1 1 V – 160 M-MoTe2-M ~1.16 μm PV 4.8 mA W−1 0 V 200 MHz 64 M-MoTe2-M ~1.55 μm PC 468 mA W−1 2 V 35 MHz 70 M-PtSe2-M ~1.55 μm PC 12 mA W−1 8 V 35 GHz 121 M-BP-M ~1.55 μm PV 135–657 mA W−1 0.4–2 V 3 GHz 71 M-BP-M ~1.55 μm PC 6.25 A W−1 0.7 V 150 MHz 161 M-BP-M 3.68 μm PG 0.7–23 A W−1 1 V – 68 4 μm 0.5–2 A W−1 M-BP-M ~3.825 μm PG 0.1–11.31 A W−1 0.5 V 550 Hz 69 M-BP-M 2 μm PV 0.026–0.307 A W−1 0.4 V 0.5–1.33 GHz 72 MoTe2-G ~1.31 μm PV; PC 23–400 mA W−1 3 V 0.5 GHz 89 MoTe2-G 1.26–1.34 μm PV; PC ~ 7–150 mA W−1 0.6 V 12–46 GHz 90 G-hBN-G ~1.55 μm DT; F-N tunneling 240 mA W−1 10 V 28 GHz 123 G-Si 2.75 μm IPE 0.13 A W−1 1.5 V – 98 Au-G-Si ~1.55 μm IPE 85 mA W−1 1 V – 99 G-Si ~1.55 μm IPE 11 mA W−1 0 V > 50 GHz 122 PV photovoltaic, IPE internal photon emission, DT direct tunneling, F-N tunneling, Fowler-Nordheim (F-N) tunneling, PC photoconductive, PG Photo-gating, BOLbolometric, PTE photo-thermoelectric.
aThe measured bandwidths may be setup limited.
bIn ref. 107, the graphene has two or three layers.Table 2. Performances of surface-illuminated Si/2DM PDs at the NIR and MIR range.
Configuration Year Structure λ(μm) Mechanism Responsivity@input power (λ) |Bias| Bandwidth/Response timea D*(Jones)@Tb Refs. Metal-2DM-metal 2009 M-G-M ~1.55 PV 0.5 mA W−1 - > 40 GHz - 59 2010 M-G-M ~1.55 PV 6.1 mA W−1@0.4 V - 16 GHz ~1.08 × 105c 141 2018 M-G-M 0.8-20 PV
PC0.6-0.075 A W−1@2.5-50 μW (0.8 μm) 0.02 V 50 GHz (0.8 μm) ~1.5-15 × 108(3-20 μm)* 128 11.5 A W−1@2.5 μW (20 μm) 2013 M-GQDs-M 0.532-10.3 PG 0.2-1.25 A W−1(0.53 μm) 0.02 V - - 142 2012 M-G (bilayer)-M 0.658-10.6 BOL 2 × 105 V W−1(10.6 μm) - > 1 GHz (1.03 μm) ~3.03 × 1010(10.6 μm)@5 K* 51d 2018 M-G-M 1.531 BOL - - 30 ps@5 K (read out-limited) ~3.5 × 107@5 K 53 2020 M-G-M 3.4-12 BOL 1.4-5.1 mA W−1 0.5 V 47 MHz ~7.22 × 104-2.65 × 105* 162 2017 M-BP-M 2.5-3.7 PV; PC 160 mA W−1@25 μW 22 mA W−1@785 μW 0.2 V > 0.88 MHz - 163 2017 M-bPAs-M 2-8 PV 180-20.3 mA W−1@0.07-44.3 μW (3.66 μm) 0 V ~0.65 kHz (4.03 μm)~11.4 kHz (1.55 μm) > 1.06 × 108(2-8 μm) 130 2017 M-BP-M 3.4 PC 518 mA W−1@40 μW, 77 K 1.2 V > > 10 kHz (1.3 GHz estimated) ~2.67 × 1010* 29 5 30 mA W−1@50 μW, 77 K ~2.29 × 107* 7.7 2.2 mA W−1@100 μW, 77 K ~1.19 × 106* 2017 M-BP-M M-bPAs-M 1-4.6 PC ~11 A W−1@RT (3.6 μm) 0.5 V 117 kHz (0.98 μm) 1 × 1010-6 × 1010@1V 129 2016 M-BP-M 3.39 PG 82 A W−1@1.6 nW 0.9 A W−1@30 μW 0.5 V 1.1-2.2 kHz ~1.2 × 108* 67 2018 M-BP-M 0.514-1.8 PG 5 × 103-6 × 104A W−1@1.6 W cm−2, 70 K 2 V ~35 kHz (0.632 μm) ~2.1 × 1010(0.632 μm) 143 2018 M-BP-M 1.55 PG 230 A W−1@11 nW 1 V ~73 Hz - 144 2018 M-bAsP-M 3.4 PG
PTE
PV190 mA W−1 1 V - ~2.86 × 107* 164 5 16 mA W−1 ~2.16 × 106* 7.7 1.2 mA W−1 ~1.86 × 105* 2018 M-Te-M 1.4-2.4 PG 27 A W−1@78 K (1.7 μm)16 A W−1@297 K (1.7 μm) 5 V - 2.9 × 109@RT 2.6 × 1011@78 K 33 2019 M-Te-M 0.52 PG 383 A W−1@1.6 nW 1 V ~1 kHz@0.95 nW - 131 1.55 PV ~19.2 mA W−1@0~30 μW 37 MHz@39-250 μW 3.39 PG ~18.9 mA W−1@0-30 μW 35 Hz@30 μW 2019 M-ReS2-M 0.8−1.2 BOL 380-350 A W−1 0.1 V ~117 Hz ~1.3 × 1010 165 2020 M-PtSe2-M 0.765-1.55 PC
PV0.19 mA W−1(1.55 μm) 5 V 4.5-17 GHz ~1.2 × 107(1.55 μm)* 35 Metal-2DM+X-metal 2014 M-G+Ta2O5+G-M 1.2 PG 20 A W−1 1 V - - 166 2.4 0.45 A W−1 2015 M-G+CNT-M 0.405-1.55 PG 20 A W−1@0.3 μW (1.55 μm) 0.5 V ~3.5 kHz (0.65 μm) - 76 2017 M-G+SiQDs-M 0.375-1.87 PG 1.2-22 × 108 A W−1@0.2 μW cm−2 1 V sub-Hz scale ~1013@RT 75 2.5-3.9 0.22-44.9 A W−1@375 mW cm−2 ~105@77 K 2017 M-BP+G-M 1.55 PG 1300 A W−1@11 nW 210 A W−1@211 nW 1 V ~88 Hz - 46 2017 M-Au+G+Si-M ~1.55 PG 83 A W−1@0.3 μW 10 V ~580 kHz ~108 78 2DM-heterostructure 2016 G-WSe2-G ~1.55 IPE 0.12 mA W−1 0.6 V - - 100 2016 WSe2-G-MoS2 0.4-2.4 PV 0.1-1 A W−1(1.3-2.4 μm) 1 V ~7 kHz (0.53-0.94 μm) 2 × 109-2 × 1010 86 2018 G-GaSe-G 0.73 IPE 10 mA W−1 1 V 3.9 Hz ~5.76 × 107c 167 1.33 3 mA W−1 2.2 Hz ~1.73 × 107c 1.55 0.05 mA W−1 1.5 Hz ~2.9 × 105c 2019 G-hBN-G ~0.532 IPE
F-N tunneling13 μA W−1 Few volts - 5 × 1014 101 ~1.55 70 nA W−1 - 2017 G-Si ~1.55 IPE ~20 mA W−1 10 V - 5.1 × 107 136 2018 G-Si 2 IPE 0.16 mA W−1 0 V - 2.56 × 107 138 2019 G nanowalls-Au-Si 1.55 IPE 21 mA W−1@0.19 μW 1 V ~0.95 kHz 1.6 × 109 168 3.5 0.44 μA W−1 0 V - - 2020 CQDs+G-TiO2-Ti 1.625 PG 70 A W−1 0.5 V 1.1 kHz ~8.1 × 107*e 103 2020 WS2-HfS2 4.3-10 ILE ~92.4-3510 A W−1@0.5 nW 1.5 V 100-200 Hz 7 × 1012(7 μm) 13 2016 BP-MoS2 ~0.532 PV
PG22.3 A W−1@1 nW 3 V - 3.1 × 1011 92 1.55 153.4 mA W1@1 nW ~23.3 kHz 2.13 × 109 2017 WS2-BP-MoS2 ~0.532 PV
PG6.32 A W−1@13.5 nW 3 V - 1.01 × 109 93 1.55 1.12 A W−1@13.5 nW 1.74 × 108 2017 BP-MoS2 2-8 PV 115.4-216.1 mA W−1(2.36-4.29 μm) 0 V - > 4.9 × 109(3-5 μm) 130 2018 BP-MoS2 1.6-4 PV 0.1-0.9 A W−1 0 V ~100 kHz 1.1 × 1010(3.8 μm) 94 2020 BP-MoS2 2-4 PV 0.11 A W−1(3 μm) 0 V ~0.1-1 GHz 1.7 × 109(3.0 μm) 95 GQDs graphene quantum dot-like arrays, CQDs colloidal quantum dots, SiQDs Si quantum dots, PV photovoltaic, IPE internal photon emission, DT direct tunneling, F-N tunneling Fowler-Nordheim tunneling, PC photoconductive, PG photo-gating, BOL bolometric, PTE photo-thermoelectric, ILE interlayer exciton, RT room temperature.
aThe measured values are counted.
bThe data marked with asterisk (*) are extracted by using the provided NEP and the device active region area.
cExtracted by the measured data considering the shot noise and the thermal noise.
dThe responsivity and the related specific detectivity D* may be overestimated because the optical absorption was ignored here.
eExtracted from the measured value NEP = 1.8 × 10−11 W at the modulation frequency of 30 Hz with a device active area of ~210 μm2. -
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