Van Der Waals Hybrid Integration of 2D Semimetals for Broadband Photodetection

Abstract

Hybrid heterostructures are pivotal in the advanced broadband detection technology. The emergence of 2D semimetals has expanded the range of materials in heterostructures beyond conventional narrow-gap materials for room-temperature broadband detection applications due to their extraordinary optical and electrical properties. This review outlines the cutting-edge and latest advancements in broadband photodetectors (PDs) engineered from heterostructures that synergistically combine 2D semimetals with several different dimensional materials. It begins with a fundamental investigation, offering an in-depth explanation of the essential material properties and a summary of synthesis methodologies. Then, the discussion advances to provide an analytical overview of the categorization, underlying photodetection mechanism, and figures-of-merit of these advanced PDs. Subsequently, the narrative shifts to a comprehensive analysis of heterogeneous integrated devices. The review further highlights the diverse optoelectronic applications of broadband PDs, spanning image sensing, optical communication, position-sensitive detection, integrated sensing and computing, spintronics, and computational spectroscopy are thoroughly highlighted. Finally, the review concludes by addressing the challenges and opportunities in advancing 2D semimetal materials for photodetection.

Keywords: 2D semimetal; Van der Waals heterostructures; broadband photodetection; hybrid integration.

Figure 1

Summary diagram of the review.

Figure 2

2D semimetals and their classification. PtTe₂: Reproduced with permission.^{[ 49 ]} Copyright 2020, American Chemical Society. PtSe₂: Reproduced with permission.^{[ 50 ]} Copyright 2019, American Chemical Society. NiTeSe: Reproduced with permission.^{[ 51 ]} Copyright 2021, The Authors, published by Wiley‐VCH. Ir_{1− x} Pt _x Te₂: Reproduced with permission.^{[ 52 ]} Copyright 2021, American Chemical Society. NiTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 53 ]} Copyright 2021, The Authors, published by Springer Nature. PdTe₂: Reproduced with permission.^{[ 54 ]} Copyright 2023, American Chemical Society. TaIrTe₄: Reproduced with permission.^{[ 55 ]} Copyright 2023, The Authors, published by Springer Nature. WTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 56 ]} Copyright 2022, The Authors, published by Springer Nature. MoTe₂: Reproduced with permission.^{[ 57 ]} Copyright 2021, American Chemical Society. NbIrTe₄: Reproduced with permission.^{[ 58 ]} Copyright 2022, Wiley‐VCH. ZrGeSe: Reproduced with permission.^{[ 59 ]} Copyright 2021, American Chemical Society. CuSe: Reproduced with permission.^{[ 60 ]} Copyright 2018, Wiley‐VCH. Au₂Ge: Reproduced with permission.^{[ 61 ]} Copyright 2024, American Chemical Society. Gu₂Si: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 62 ]} Copyright 2017, The Authors, published by Springer Nature.

Figure 3

Preparation methods of 2D semimetals.

Figure 4

a) Schematic diagram of roll‐to‐roll production of graphene films (left) and a photograph of 30‐inch graphene (right). Reproduced with permission.^{[ 120 ]} Copyright 2010, Springer Nature. b) Left: Schematic diagram of the (W, Mo)Te₂ film preparation. Middle: Optical image of patterned WTe₂ grown on a 4‐inch SiO₂/Si substrate. Right: optical image captured at marked points on the WTe₂ wafer. Reproduced with permission.^{[ 122 ]} Copyright 2020, The Authors, published by Springer Nature. c) Left: Photograph of patterned PtTe₂ grown on a 2‐inch SiO₂/Si substrate. Right: OM image captured from the left image. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 123 ]} Copyright 2022, The Authors, published by Springer Nature. d) Left: Schematic diagram of wafer‐scale growth of WTe₂ layers. Right: Photograph of a large number of synthesized WTe₂ samples. Reproduced with permission.^{[ 124 ]} Copyright 2024, AIP Publishing. e) Left: Photograph of PtSe₂ films with different thicknesses grown on a 4‐inch SiO₂/Si substrate. Right: Raman peak intensity statistical of the PtSe₂ wafer. Reproduced with permission.^{[ 126 ]} Copyright 2024, American Chemical Society. f) Left: Photograph of large‐area patterned PdTe₂ films grown on a quartz substrate. Right: STEM image of the PdTe₂ layer. Reproduced with permission.^{[ 54 ]} Copyright 2023, American Chemical Society.

Figure 5

Operational mechanism of PDs based on 2D materials.

Figure 6

Broadband photoconductive PDs based on semimetal. Clockwise from top‐left: Graphene: Reproduced with permission.^{[ 128 ]} Copyright 2014, Springer Nature. MoTe₂: Reproduced with permission.^{[ 16 ]} Copyright 2018, Wiley‐VCH. MoTe₂: Reproduced with permission.^{[ 130 ]} Copyright 2021, The Authors, published by Wiley‐VCH. Ir_{1− x} Pt _x Te₂: Reproduced with permission.^{[ 52 ]} Copyright 2021, American Chemical Society. NiTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 53 ]} Copyright 2021, The Authors, published by Springer Nature. PtTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 131 ]} Copyright 2021, The Authors, published by UESTC and John Wiley & Sons Australia, Ltd. WTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 134 ]} Copyright 2023, The Authors, published by Springer Nature. PtTe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 133 ]} Copyright 2023, The Authors, published by UESTC and John Wiley & Sons Australia, Ltd. TiSe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 23 ]} Copyright 2023, The Authors, published by UESTC and John Wiley & Sons Australia, Ltd. PtSe₂: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 132 ]} Copyright 2022, The Authors, published by Springer Nature. NbIrTe₄: Reproduced with permission.^{[ 58 ]} Copyright 2022, Wiley‐VCH. PtTe₂: Reproduced with permission.^{[ 114 ]} Copyright 2021, American Chemical Society. WTe₂: Reproduced with permission.^{[ 129 ]} Copyright 2018, Wiley‐VCH.

Figure 7

Mixed‐dimensional heterojunction.

Figure 8

a,b) Schematic and energy band diagram of graphene–quantum dot hybrid phototransistor. c) The spectral responsivity of single‐layer and bilayer graphene phototransistors with PbS quantum dots of varying sizes. a–c) Reproduced with permission.^{[ 142 ]} Copyright 2012, Springer Nature. d,e) Energy band diagram of graphene/PdS QDs transistor. f) Characteristics of responsivity of graphene/PdS QDs transistor grown on flexible substrates as a function of light irradiance before and after bending test. d–f) Reproduced with permission.^{[ 143 ]} Copyright 2012, Wiley‐VCH. g) Schematic diagram of a hybrid PD integrating graphene with Ti₂O₃ nanoparticles. h) Photocurrent of graphene/Ti₂O₃ hybrid PD with the size of Ti₂O₃ nanoparticles. i) Comparison of the performance of hybrid graphene/Ti₂O₃ PD with literature reported previously. g–i) Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 147 ]} Copyright 2018, The Authors, published by Springer Nature. j) Schematic of graphene/HgTe nanocrystal heterostructure PD. k) Specific detectivity of graphene/HgTe/graphene junctions at 1.55 µm under different bias voltages. l) The response time of the graphene/HgTe/graphene heterostructure under 1.55 µm light illumination. j–l) Reproduced with permission.^{[ 148 ]} Copyright 2020, American Chemical Society.

Figure 9

a) Schematic diagram and b) broadband response of BNQDs/PtSe₂/p‐Si PDs. a,b) Reproduced with permission.^{[ 149 ]} Copyright 2023, IEEE. c) Schematic diagram, d) energy band diagram and e) absorption spectrum of the device based on WTe₂/CsPbI₃ perovskite heterojunction. c–e) Reproduced with permission.^{[ 151 ]} Copyright 2023, IOP Publishing. f) Schematic diagram of MoTe₂/CsPbBr₃ device. g) I–V curves and h) responsivity of the two devices based on CsPbBr₃ perovskite and MoTe₂/CsPbBr₃ heterojunction. f–h) Reproduced with permission.^{[ 152 ]} Copyright 2022, IOP Publishing.

Figure 10

a) Schematic of the heterostructure PD consisting of graphene and Au nanoparticles. b) The photocurrent and responsivity as a function of incident light power for graphene with and without Au nanoparticles. c) Enlarged views of the temporal photocurrent of PD with and without Au nanoparticles. a–c) Reproduced with permission.^{[ 154 ]} Copyright 2016, American Chemical Society. d) Schematic of graphene/Si‐QDs heterostructure PD. e) Two different optical phenomena in the working process of graphene/Si‐QDs PD. f) Energy band diagram and charge transfer schematic of graphene/Si‐QDs PD after UV‐NIR irradiation. g) The relationship between the responsivity and incident light irradiance under different wavelengths ranging from UV to NIR. d–g) Reproduced with permission.^{[ 155 ]} Copyright 2017, American Chemical Society. h) Schematic diagram of the integrated device with plasmonic nanoparticles and graphene. i) Plasmonic enhanced photocurrent as a function of laser wavelength. j) Photocurrent enhancement induced by Au thin films of different thicknesses. i,j) Reproduced with permission.^{[ 156 ]} Copyright 2011, Springer Nature. k) Schematic diagram of WO_2.9–graphene heterojunction PD. l) Illustration of the thermal electron transfer process between graphene and WO_2.9. m) Transient response of WO_2.9–graphene and PbS–graphene devices under excitation at a wavelength of 1550 nm. k–m) Reproduced with permission.^{[ 157 ]} Copyright 2019, Wiley‐VCH.

Figure 11

2D/1D vdW heterojunction. Reproduced with permission.^{[ 162 ]} Copyright 2021, IOP Publishing. a) Schematic illustration of CdSe nanobelt/graphene photovoltaic Schottky junction detector. b) Photocurrent response of the CdSe nanobelt/graphene detector and the external quantum efficiency at different wavelengths. a,b) Reproduced with permission.^{[ 163 ]} Copyright 2013, RSC Publishing. c) Schematic representation of Te/MoTe₂ heterostructure device. d) Response time of Te/MoTe₂ heterostructure device. c,d) Reproduced with permission.^{[ 164 ]} Copyright 2021, Wiley‐VCH. e) Graphical illustration of PD based on SWNT–graphene hybrid film. f) The relationship between the responsivity of SWNT–graphene device and the optical power under different wavelengths of light irradiation. e,f) Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 165 ]} Copyright 2015, The Authors, published by Springer Nature. g) Schematic of graphene–Bi₂Te₃ hybrid structures. h) Responsivity (γ) of graphene–Bi₂Te₃ hybrid structures under different wavelengths of light irradiation. g,h) Reproduced with permission.^{[ 166 ]} Copyright 2019, RSC Publishing. i) Schematic diagram of the PtSe₂/SiNWA structure. j) Photoresponse of the PtSe₂/SiNWA structure. i,j) Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 167 ]} Copyright 2018, The Authors, published by Springer Nature. k) Schematic diagram of the Gr/SiNWA heterojunctions. l) Photoresponse of the photocurrent of Gr/SiNWA device under different wavelengths of light irradiation. k,l) Reproduced with permission.^{[ 168 ]} Copyright 2021, American Chemical Society.

Figure 12

a) Schematic of IR detector based on Te/graphene heterostructure. b) The normalized photoresponse versus modulated frequency of Te/graphene PD. The inset depicts the response time of the device. c) Responsivity and quantum efficiency of Te/graphene device as a function of wavelengths. a–c) Reproduced with permission.^{[ 169 ]} Copyright 2022, American Chemical Society. d) Schematic of BP/PtSe₂ device. e) The temperature‐dependent D* of BP/PtSe₂ Schottky junction, BP film, and PtSe₂ film. d,e) Reproduced with permission.^{[ 170 ]} Copyright 2023, Wiley‐VCH. f) Schematic diagram of PdTe₂/WSe₂ FET. g) D* and R of PdTe₂/WSe₂ FET as a function of wavelengths. f,g) Reproduced with permission.^{[ 22 ]} Copyright 2023, Wiley‐VCH.

Figure 13

a) Schematic of PtSe₂/graphene heterostructure PD. Inset: the optical image of the PD. b) Band diagram of PtSe₂/graphene heterojunction. c) The dependency of photocurrent and responsivity of PtSe₂/graphene PD on bias voltage at 0.3 THz. a–c) Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 132 ]} Copyright 2022, The Authors, published by Springer Nature. d) Schematic of PtTe₂/graphene device. e) Band diagram of PtTe₂/graphene heterojunction. f) R and D* of PtTe₂/graphene device as a function of wavelengths. d–f) Reproduced with permission.^{[ 25 ]} Copyright 2022, American Chemical Society. g) Schematic diagram of NbIrTe₄–graphene heterojunction detector. h) Band diagram of NbIrTe₄–graphene heterojunction. i) The responsivity of NbIrTe₄ and its heterojunction with graphene. g–i) Reproduced with permission.^{[ 171 ]} Copyright 2023, Wiley‐VCH.

Figure 14

a) Schematic illustration of PD based on PSN heterojunction. b) Optical image (top) and schematic diagram (bottom) of MoS₂/graphene/WSe₂ heterojunction device. c) D* and R of detector composed of MoS₂–graphene–WSe₂ as a function of wavelengths. a–c) Reproduced with permission.^{[ 172 ]} Copyright 2016, American Chemical Society. d) Optical image (top) and schematic diagram (bottom) of p‑WSe₂/TaIrTe₄/n‐MoS₂ vdW heterojunction PD. e) Photocurrent response characteristics of p‑WSe₂/TaIrTe₄/n‐MoS₂ PD under different wavelength light illumination. f) The relationship between the normalized photocurrent of p‑WSe₂/TaIrTe₄/n‐MoS₂ PD and the polarization angle under 635 nm polarized light illumination. d–f) Reproduced with permission.^{[ 173 ]} Copyright 2021, American Chemical Society. g) Schematic of 2H‐MoTe₂/1T‐MoTe₂/SnSe₂ PD. h) R of 2H‐MoTe₂/1T‐MoTe₂/SnSe₂ device as a function of wavelengths i) The variation law of photocurrent with polar coordinate angle for 2H‐MoTe₂/1T‐MoTe₂/SnSe₂ PD under linearly polarized lasers at 635 nm, 1310 nm, and 1550 nm. g–i) Reproduced with permission.^{[ 174 ]} Copyright 2021, Springer Nature.

Figure 15

a) Left: schematic illustration of PtTe₂/Si PD. Middle: working mechanism of PtTe₂/Si heterojunction. Right: The specific detectivity of PtTe₂/Si PD is compared with that of previously reported devices. Reproduced with permission.^{[ 175 ]} Copyright 2020, Wiley‐VCH. b) Schematic diagram (top) and D* (bottom) of PdTe₂/Si Schottky junction‐based PD. Reproduced with permission.^{[ 54 ]} Copyright 2023, American Chemical Society. c) Schematic diagram (left) and D* (right) of 1T'‐MoTe₂/Si Schottky junction devices. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 125 ]} Copyright 2023, The Authors, published by Springer Nature. d) Top: schematic diagram of PtSe₂/Pyramid Si heterojunction PD. Bottom: Responsiveness and specific detectability of PtSe₂/pyramid Si device under different wavelengths of light. Reproduced with permission.^{[ 176 ]} Copyright 2022, IEEE. e) Left: schematic illustration of PtSe₂/ultrathin SiO₂/Si heterojunction PD. Middle: I–V curves in the dark for PtSe₂/Si devices with and without ultrathin SiO₂ layers; The illustration shows an optical image of a produced PD. Right: specific detectivity of PtTe₂/Si PD is compared with that of previously reported devices. Reproduced with permission.^{[ 177 ]} Copyright 2022, Springer Nature. f) Schematic illustration (left), energy band diagram (middle), and R (right) of graphene/Si PD with an insulating layer of AlN. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 178 ]} Copyright 2021, The Authors, published by Springer Nature.

Figure 16

a) Upper panel: schematic illustration and optical image of graphite/WTe₂/Ge mixed vdW heterostructure. Bottom panel: energy band diagram of graphite/WTe₂/Ge PD. Normalized photocurrent of graphite/WTe₂/Ge PD as a function of wavelength (right). Reproduced with permission.^{[ 180 ]} Copyright 2023, IEEE. b) Upper panel: schematic diagram of PD‐based PtSe₂/Ge Schottky junction (left). I–V curves of PtSe₂/Ge PD with and without an aluminum oxide layer under dark conditions and 1550 nm light illumination. Bottom panel: temporal photovoltaic response of the PD with and without an aluminum oxide layer under 1550 nm light illumination. R varies with light intensity under MIR illumination at different wavelengths. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 181 ]} Copyright 2023, The Authors, published by UESTC and John Wiley & Sons Australia, Ltd. c) Schematic of PD based on PdTe₂/Ge heterostructure with quasi‐2D perovskite antireflection. Schematic illustration of the anti‐reflection light trapping mechanism of quasi‐2D perovskite layer on PdTe₂/Ge heterostructure. The electric field distribution of the heterostructure covered with the quasi‐2D perovskite layer in different thicknesses under 1550 nm light illumination. Wavelength‐dependent R of PdTe₂/Ge device with and without quasi‐2D perovskite layer. The illustration shows the electric field distribution of a PdTe₂/Ge heterostructure device without and with quasi‐2D perovskite layer under 700 nm light illumination. Reproduced with permission.^{[ 182 ]} Copyright 2022, Royal Society of Chemistry.

Figure 17

a) Left: separation and migration process of photogenerated carriers in the PtSe₂/GaAs heterojunction region. Right: wavelength‐dependent R and D* of PtSe₂/GaAs PD. Reproduced with permission.^{[ 183 ]} Copyright 2018, Wiley‐VCH. b) Left: schematic diagram of PD based WTe₂/GaAs Schottky junction. Right: wavelength‐dependent normalized I _ph of PDs based on WTe₂/GaAs heterojunction and GaAs semiconductor. Reproduced with permission.^{[ 184 ]} Copyright 2022, AIP Publishing. c) Left: schematic of PtSe₂/CdTe PD. Right: sensitivity of PtSe₂/CdTe PD as a function of wavelength. Reproduced with permission.^{[ 185 ]} Copyright 2018, American Chemical Society. d) Schematic illustration (left) and R (right) of PdTe₂/GaN device. Reproduced with permission.^{[ 186 ]} Copyright 2021, IEEE.

Figure 18

a) Left: schematic diagram of 1Tʹ‐MoTe₂/Si Schottky junction device for imaging. Right: The device captures the LWIR pattern at 10.6 µm. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 125 ]} Copyright 2023, The Authors, published by Springer Nature. b) PtTe₂/Si‐based PD exhibits imaging results of the “POLYU” and “ZZU” patterns under illumination at 4.55 and 10.6 µm, respectively. Reproduced with permission.^{[ 175 ]} Copyright 2020, Wiley‐VCH. c) Graphene–NiTeSe heterojunction PD performs terahertz imaging of a pattern composed of Cu‐foils. Reproduced with permission.^{[ 199 ]} Copyright 2022, Wiley‐VCH. d) The ZrGeSe‐based PD enables terahertz imaging of concealed ink and scissors. Reproduced with permission.^{[ 188 ]} Copyright 2021, The Authors, published by Wiley‐VCH. e) NiTe₂‐based detector exhibits imaging results of a blade and metal ring inside an envelope. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 53 ]} Copyright 2021, The Authors, published by Springer Nature. f) Ir_0.7Pt_0.3Te₂–graphene PD scans a metal key inside an envelope. g) Metal–Ir_0.7Pt_0.3Te₂–metal PD performs terahertz imaging of a capsule. f,g) Reproduced with permission.^{[ 52 ]} Copyright 2021, American Chemical Society. h) Terahertz imaging of a fresh leaf and a metal ring is achieved using PtSe₂/graphene device. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 132 ]} Copyright 2022, The Authors, published by Springer Nature.

Figure 19

a) Broadband imaging schematic and results of graphene–CMOS integrated sensor. Reproduced with permission.^{[ 219 ]} Copyright 2017, Springer Nature. b) NIR imaging demonstrated by PtTe₂‐based PD array. Reproduced with permission.^{[ 207 ]} Copyright 2020, American Chemical Society. c) Top: statistical analysis of dark current, photocurrent, and rectification ratio of a 9 × 9 PD array based on PtSe₂/ultrathin SiO₂/Si heterojunction. Bottom: Schematic diagram of an NIR imaging device and its imaging result for the letter “U”. Reproduced with permission.^{[ 177 ]} Copyright 2022, Springer Nature. d) Optical photograph of an 8 × 8 array device integrated with 1Tʹ‐MoTe₂/Si heterojunctions and MIR imaging for “heart” pattern. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 125 ]} Copyright 2023, The Authors, published by Springer Nature.

Figure 20

a) Transmission of the ASCII code character “NIR” is based on PdTe₂/WSe₂ devices. Reproduced with permission.^{[ 22 ]} Copyright 2023, Wiley‐VCH. b) The “MoTe₂” character encoded in ASCII is successfully transmitted using a 1Tʹ‐MoTe₂/Si Schottky junction device. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 125 ]} Copyright 2023, The Authors, published by Springer Nature. c) The character “MIR” is decoded based on PdTe₂/Si devices. Reproduced with permission.^{[ 54 ]} Copyright 2023, American Chemical Society. d) The character “MoTe₂” is transmitted through IR light communication based on a 1T’‐MoTe₂/Ge position detector. Reproduced with permission.^{[ 212 ]} Copyright 2024, Springer Nature.

Figure 21

a) Upper panel: Schematic of the Gr‐readout SiGe/Si micro‐tube PD (left). Omnidirectional photodetection of the PD (middle). Allocated bit distribution of discrete multi‐tone signals at a data rate of 778 Mbps (right). Bottom panel: Polarized current signals for visible light communication. Reproduced with permission.^{[ 225 ]} Copyright 2024, Wiley‐VCH. b) Schematic (top) and frequency response (bottom) of metamaterial perfect absorber graphene PD. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 226 ]} Copyright 2024, The Authors, published by Springer Nature. c) Left: Schematic of the tBLG PD. Middle: Band structure and density of states of tBLG. Right: Frequency response of the tBLG PD. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 227 ]} Copyright 2024, The Authors, published by Springer Nature.

Figure 22

a) Left: schematic diagram of carrier diffusion and band diagram in Si and graphene/Si heterojunction PSDs. Right: Optical image and trajectory tracking schematic diagram of graphene/Si. Reproduced with permission.^{[ 233 ]} Copyright 2018, Optical Society of America. b) Schematic diagram and trajectory tracking of Graphene/Ge PSD. Reproduced with permission.^{[ 234 ]} Copyright 2019, American Chemical Society. c) Left: schematic diagram and band diagram of graphene/Ga₂O₃ heterojunction PSD. Right: trajectory tracking of graphene/Ga₂O₃ PSD. Reproduced with permission.^{[ 235 ]} Copyright 2022, American Chemical Society. d) Left: Schematic diagram of carrier diffusion in graphene/Si PSD before and after plasma treatment. Right: schematic diagram of PSD tracking human arm swing. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 236 ]} Copyright 2020, The Authors, published by UESTC and John Wiley & Sons Australia, Ltd. e) Schematic diagram of graphene field‐effect transistor and position‐sensitive light response. Reproduced with permission.^{[ 237 ]} Copyright 2017, Springer Nature.

Figure 23

a) Broadband image sensing and convolution processing of PdSe₂/MoTe₂ PD. Reproduced with permission.^{[ 238 ]} Copyright 2022, The Authors, published by Springer Nature. b) IR gesture recognition and interaction system based on Gr/PtSe₂/Si heterojunction. Reproduced with permission.^{[ 239 ]} Copyright 2024, Wiley‐VCH. c) High‐frequency rectifier utilizing semimetal NiTe₂. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 53 ]} Copyright 2021, The Authors, published by Springer Nature. d) Spin‐galvanic effect in graphene/MoTe₂ device. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 240 ]} Copyright 2021, The Authors, published by Springer Nature. e) Mode‐division demultiplexing spectrometer based on graphene‐based PDs. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0).^{[ 244 ]} Copyright 2022, The Authors, published by Institute of Optics and Electronics, Chinese Academy of Sciences.