WO2020035695A1 - Guides d'ondes actifs à commande électrique - Google Patents

Guides d'ondes actifs à commande électrique Download PDF

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Publication number
WO2020035695A1
WO2020035695A1 PCT/GB2019/052301 GB2019052301W WO2020035695A1 WO 2020035695 A1 WO2020035695 A1 WO 2020035695A1 GB 2019052301 W GB2019052301 W GB 2019052301W WO 2020035695 A1 WO2020035695 A1 WO 2020035695A1
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Prior art keywords
sheet
waveguide
heterostructure
sheets
acts
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PCT/GB2019/052301
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English (en)
Inventor
Vladimir FALKO
Roman Gorbachev
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The University Of Manchester
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Publication of WO2020035695A1 publication Critical patent/WO2020035695A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/12004—Combinations of two or more optical elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0232—Optical elements or arrangements associated with the device
    • H01L31/02327—Optical elements or arrangements associated with the device the optical elements being integrated or being directly associated to the device, e.g. back reflectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035209—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/09—Devices sensitive to infrared, visible or ultraviolet radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/12—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto
    • H01L31/125—Composite devices with photosensitive elements and electroluminescent elements within one single body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/40—Materials therefor

Definitions

  • This invention relates to optical waveguides that have active optoelectric devices embedded in their core.
  • the optoelectric devices comprise heterostructure formed of 2-D materials.
  • Optical waveguides are key components in the telecommunication industry and remote sensing. In the majority of applications, they are used for the passive transmission of optical signals.
  • the active functions, such as signal generation, detection and amplification are performed by dedicated devices placed in the optical path and connected to the waveguide.
  • Such equipment can include, but not limited by fault locators, power meters and optical time domain reflectometers.
  • the 2-D material was positioned outside or on the surface of the waveguide core. They operate as sensors or modulators using the evanescent field - decaying part of electromagnetic field penetrating through the core’s surface.
  • the present invention relates to novel devices whereby atomically flat electronic components can be integrated into an optical waveguide to perform detection of transmitted light and/or emit light into the waveguide.
  • an optical waveguide comprising:
  • said optoelectric device comprises a heterostructure comprising a plurality of stacked sheets; wherein each sheet comprises a 2-dimensional (2D) material and is from 1 to 15 molecular layers thick; wherein the heterostructure comprises at least two different 2D materials; and wherein at least one sheet comprises an optically active 2D material.
  • 2D 2-dimensional
  • the heterostructure may comprise at least one sheet of graphene or modified (e.g. doped) graphene.
  • the heterostructure may comprise at least one sheet of hBN.
  • Typical optically active 2D materials are selected from a post-transition metal chalcogenide (PTMC) or a transition metal dichalcogenide (TMDC).
  • PTMC post-transition metal chalcogenide
  • TMDC transition metal dichalcogenide
  • the light emitted or detected by the device may be any wavelength, e.g. visible, infrared and even terahertz range.
  • the light emitted or detected by the optoelectric device may be of wavelength in the infrared range, e.g. the far-infrared range.
  • the light emitted or detected by the optoelectric device may be of wavelength in the infrared range.
  • the light emitted or detected by the optoelectric device may be of wavelength in the far-infrared range.
  • the optoelectric device may be configured to emit light.
  • the light may have a wavelength in the infrared, e.g. the far-infrared, range.
  • an electric bias is applied between two contacts (typically graphene: G r and QG B , see Figure 2), injecting an electron and hole into the optically active layer.
  • the e-h pair then recombines emitting a photon with energy equal to the optical bandgap of the chosen 2D semiconductor of which the optically active layer is comprised.
  • the optoelectric device may be a light emitting diode.
  • the LED may be orientated such that the optical signals are emitted from the LED along the optical axis of the core. It may be that the planes of the sheets of the heterostructure are orientated substantially parallel to the optical axis of the waveguide.
  • heterostructure may thus emit light in a direction parallel to the plane of the sheets of the heterostructure.
  • the photons are predominantly polarised perpendicular to the basal plane. This may occur through intersubband optical transition in few molecular layer film. Alternatively it may occur through the recombination between electrons at the Gamma point of PTMC and holes at the Gamma point of few molecular layer TMDC film.
  • TMDCs In plane emission has been demonstrated for TMDCs (G. Wang et ai, ⁇ h-Plane Propagation of Light in Transition Metal Dichalcogenide Monolayers: Optical Selection Rules,” Phys. Rev. Lett., vol. 119, no. 4, pp. 1-10, 2017.).
  • the inventors have also demonstrated similar effects for InSe (see figure 5).
  • the heterostructure may comprise, stacked in the following order:
  • Such heterostructures may be excited, and thus caused to emit light, by a higher energy light (so called optical pumping).
  • the heterostructure may comprise, stacked in the following order:
  • a first sheet that acts as a contact e.g. a transparent contact
  • a first sheet that acts as an insulating barrier a sheet that is optically active
  • a second sheet that acts as a contact e.g. a transparent contact
  • Such heterostructures are excited, and thus caused to emit light, by generating an electrical potential between the two contacts (so-called electrical pumping). Electrons and/or holes tunnel through the insulating material.
  • the heterostructure may also have a protective coating.
  • Said coating may be an amorphous material or it may be a 2D-material.
  • the heterostructure may comprise, stacked in the following order:
  • a first sheet that acts as a contact e.g. a transparent contact
  • a second sheet that acts as a contact e.g. a transparent contact
  • the sheets are stacked such that the face of one of the above listed sheets is in contact with the face of the next of the above listed sheets.
  • the contact will typically extend substantially across the full face of the sheet.
  • the sheets that act as contact may comprise graphene (e.g. single layer graphene or few layer graphene), modified graphene, or other two-dimensional conductive materials (such as NbSe 2 VSe 2 , PtSe 2 , etc).
  • graphene e.g. single layer graphene or few layer graphene
  • modified graphene e.g. single layer graphene or few layer graphene
  • two-dimensional conductive materials such as NbSe 2 VSe 2 , PtSe 2 , etc.
  • the sheets that act as contact comprise graphene or a modified graphene.
  • Graphene and modified graphenes are typically transparent.
  • the graphene may be from 1 to 4 atomic layers thick.
  • the graphene is preferably a single atomic layer thick.
  • the sheets that act as contacts each comprise pristine graphene.
  • one of the sheets that act as contacts may comprise modified graphene (e.g. doped graphene).
  • both of the sheets that act as contacts may comprise modified graphene (e.g. doped graphene).
  • first sheet that acts as a contact comprises pristine and a second sheet that acts as a contact (e.g. a transparent contact) comprises graphene (e.g. doped graphene).
  • the sheets that act as contact may comprise different materials.
  • the term‘different materials’ is intended to include differentially doped graphene (including the case where one sheet comprises graphene and the other comprises a doped graphene).
  • the sheets that act as insulating barriers comprise hBN or layered oxides (e.g. AI 2 O 3 or HfC>2). Alternatively, other wide bandgap 2D semiconductors could be used.
  • the sheets that act as insulating barriers may comprise the same 2D material, e.g. hBN. Alternatively, they may comprise different 2D materials.
  • hBN is used as an insulating barrier, it will typically be in the form of a sheet that is less than 20 molecular layers thick. It may be less than 10 layers thick. It may be less than 8 layers thick.
  • hBN will typically be in the form of a sheet that is more than 3 molecular layers thick. Most preferably, it will be from 3 to 8 layers thick.
  • the protective sheets if present, comprise hBN or layered oxides (e.g. AI 2 O 3 or HfC>2).
  • the protective sheets may comprise a polymer film.
  • the protective sheets may comprise the same 2D material, e.g. hBN.
  • they may comprise different materials, e.g. different 2D materials.
  • hBN is used in a protective sheet, it will typically be in the form of a sheet that is less than 100 molecular layers thick. It may be less than 50 layers thick. It may be less than 20 layers thick.
  • the optically active sheet comprises a PTMC.
  • Illustrative PTMCs include InSe, GaSe, GaS and GaTe.
  • the PTMC may be p-doped.
  • the PTMC may be n- doped.
  • the optically active sheet comprises TMDC.
  • Illustrative TMDCs include M0S2, WS2, WSe2, MoSe2, MoTe2, WTe2, ZrS2, ZrSe2 and HfSe2.
  • the TMDC may be p-doped.
  • the TMDC may be n-doped.
  • the heterostructure comprises two optically active sheets in contact with each other, one optically active sheet comprising a TMDC and the other optically active sheet comprising a PTMC.
  • the TMDC may be p-doped.
  • the PTMC may be n- doped.
  • n-Doping or p-doping may be induced using a gate electrode.
  • the optically active sheet comprises black phosphorous.
  • the optically active material will typically be from 1 to 10 layers thick, e.g. from 1 to 8 layers thick.
  • the number of layers of the 2D material alters the bandgaps and therefore the wavelength of light at which the device will operate.
  • the optically active sheet may be active with respect to light having a wavelength in the infrared, e.g. the far-infrared, range.
  • TMDCs are well known for their outstanding optical properties and have high efficiency for both photodetection and light emission.
  • the key advantage of using 2D materials is their low absorption and easiness of surface integration due to them being only few atoms thick.
  • Fiber- optical communication industry generally employs photon energies in the range of 0.75 - 1 eV (bands O, E, S, C, L and U ranging from 1260 nm to 1675 nm). However, for remote sensing and other potential applications a broader range may be required, from 0.5 to 1.2 eV.
  • bandgaps in this range, for instance:
  • Suitable light emitting diode devices comprising heterostructures of 2D materials are described in the art, e.g. W02016/03184; F. Withers et ai,“Light-emitting diodes by band-structure engineering in van der Waals heterostructures,” Nat Mater, vol. 14, no. 3, pp. 301-306, 2015; G. Wang et ai,“In-Plane Propagation of Light in Transition Metal Dichalcogenide Monolayers: Optical Selection Rules,” Phys. Rev. Lett., vol. 119, no. 4, pp. 1-10, 2017).
  • the optoelectrical device may be a single photon emitter (SPE).
  • SPE single photon emitter
  • a single photon emitter will typically have the general structure described above but the optically active layer comprises an optically active 2D-material (e.g. PTMC or TMDC) that has been modified to make the energy linewidth of emission very small.
  • An SPE may be achieved by doping the optically active material (e.g. TMDC or PTMC), e.g. by exchanging a proportion of the S, Se or Te with other chemical elements (e.g. oxygen or carbon) to create defects.
  • replacing the single optically active sheet with two sheets comprising different optically active 2D materials arranged face to face with their lattices at an angle relative to each other can give rise to an SPE.
  • 2D materials have also been proposed as a promising source for single photon emission - a fundamental resource for many scalable quantum information technologies.
  • the ideal on-demand SPE emits exactly one photon at a time into a given spatiotemporal mode, and all photons are identical.
  • Such SPEs play a central role in a range of proposed quantum computing schemes.
  • efforts to engineer solid-state SPEs have expanded to include two-dimensional (2D) materials, several SPE hosts have been identified: hBN (T.
  • the optoelectric device may be configured to detect light.
  • the light may have a wavelength in the infrared range, e.g. the far-infrared, range.
  • the optoelectric device may be an optical receiver, also known as a photodiode.
  • the optical receiver will typically be orientated such that the optical signals travelling along the optical axis of the core are received by the optical receiver.
  • a typical device comprises of an optically active layer (TMDC or PTMC), two or more electrical contacts to measure photoconductivity (graphene is often used due to its optical transparency) and
  • protection/encapsulation layers hBN is typically used.
  • the device conductivity is measured in response to incident light.
  • the heterostructure comprises, stacked in the following order:
  • both said sheets being in electrical contact with the sheet that is optically active but not being in electrical contact with each other.
  • the heterostructure may also have a protective coating.
  • Said coating may be an amorphous material or it may be a 2D-material.
  • the heterostructure may comprise, stacked in the following order:
  • both said sheets being in electrical contact with the same face of the sheet that is optically active but not being in electrical contact with each other;
  • the two sheets that act as contacts are both in electrical contact with the same face of the sheet that is optically active without being in electrical contact with each other.
  • a first sheet that acts as a contact e.g. a transparent contact
  • a second sheet that acts as a contact e.g. a transparent contact
  • an insulating material e.g. a sheet of an insulating 2D material, e.g. hBN
  • the first sheet that acts as a contact is in contact with a first face of the optically active sheet and the second sheet that acts as a contact (e.g. a transparent contact) is in contact with a second face of the optically active sheet.
  • the sheets are stacked such that the face of one of the above listed sheets is in contact with the face of the next of the above listed sheets.
  • the sheets that act as contact e.g. a transparent contact
  • the sheets that act as contact comprise graphene, modified graphene, few layer graphitic films or other two-dimensional conductive materials (such as NbSe2 VSe 2 , PtSe 2 , etc).
  • the sheets that act as contacts comprise graphene or a modified graphene.
  • the graphene may be from 1 to 4 atomic layers thick. Graphene and modified graphenes are typically transparent. The graphene is preferably a single atomic layer thick.
  • the sheets that act as contacts each comprise pristine graphene.
  • one of the sheets that act as contacts may comprise modified graphene (e.g. doped graphene).
  • both of the sheets that act as contacts may comprise modified graphene (e.g. doped graphene).
  • a first sheet that acts as a contact comprises pristine and a second sheet that acts as contact (e.g. a transparent contact) comprises graphene (e.g. doped graphene).
  • the sheets that act as contact may comprise different materials.
  • the term‘different materials’ is intended to include differentially doped graphene (including the case where one sheet comprises graphene and the other comprises a doped graphene).
  • the protective sheets if present, comprise hBN or layered oxides (e.g. Si0 2 , AI 2 C>3 or Hf0 2 ).
  • the protective sheets may comprise a polymer film.
  • the protective sheets may comprise the same 2D material, e.g. hBN. Alternatively, they may comprise different materials, e.g. different 2D materials.
  • hBN is used in a protective sheet, it will typically be in the form of a sheet that is less than 100 molecular layers thick. It may be less than 50 layers thick. It may be greater than 20 layers thick.
  • the optically active sheet comprises a PTMC.
  • PTMCs include InSe, GaSe, GaS and GaTe.
  • the optically active sheet comprises TMDC.
  • TMDCs include MoS 2 , WS 2 , WSe 2, MoSe 2 , MoTe 2 , WTe 2 , ZrS 2 , ZrSe 2 and HfSe 2 .
  • the optically active sheet comprises black phosphorous.
  • the optically active material will typically be from 1 to 8 layers thick. The number of layers of the 2D material alters the bandgaps and therefore the wavelength of light at which the device will operate. [0062]
  • the optically active sheet may be active with respect to light having a wavelength in the infrared, e.g. the far-infrared, range.
  • Suitable optical receivers comprising heterostructures of 2D materials are described in the art, e.g. W02013/140181 , L. Britnell et al.,“Strong light-matter interactions in heterostructures of atomically thin films,” Science (80-J, vol. 340, no. 6138, pp. 1311-1314, 2013.
  • the waveguide can both detect and emit light. It may be that the waveguide comprises a single optical device that can both detect and emit light. In this embodiment, the device may comprise a heterostructure that comprises both a
  • heterostructures will form part of the same stack of sheets and may be separated by a sheet of an insulator (e.g. hBN).
  • the waveguide may comprise two optical devices in electrical contact, each embedded in the core.
  • a first device may be configured to emit light, for example, a device as described above under the title light emitter’ above.
  • a second device may be configured to detect light, for example, a device as described above under the title light detector’ above.
  • the waveguide may comprise a plurality of devices. It may comprise a plurality of devices configured to emit light. It may comprise a plurality of devices configured to detect light. It may comprise a plurality of devices configured to emit light and a plurality of devices configured to detect light.
  • the waveguide comprises both a device that is configured to emit light and a device that is configured to detect light
  • the two devices may be configured to amplify a signal received by the device configured to detect light, said device configured to emit light emitting said amplified signal.
  • the waveguide will typically comprise two electrical contacts connecting the optoelectric device to an electrical system external to the waveguide. These contacts may be embedded into the core and in electrical communication with contacts (e.g. transparent contacts) in the heterostructure.
  • contacts in the heterostructure may extend outside the core and be in electrical communication with contacts external to the core. It may be that no contacts are present.
  • some light emitting heterostructures can be induced to emit light via optical pumping.
  • the waveguide may be an optical fibre.
  • the waveguide can be either multimode, single mode or more specialized, e.g.
  • PMF polarization-maintaining optical fiber
  • Illustrative examples of PMFs include “elliptical clad”,“bow-tie”,“panda”.
  • the core of the waveguide may be any material that can transmit light.
  • Illustrative examples include glass, silica (e.g. quartz), polymer, air or a vacuum. Where the core of the waveguide is air or a vacuum, the device will need to be supported within the core.
  • the waveguide may be a junction between two optical fibres.
  • the waveguide may further comprise one or more coatings on the core.
  • coatings are well known in fibreoptics and may include cladding, buffer and jacket coatings.
  • a light emitting device comprising a heterostructure comprising a plurality of stacked sheets; wherein each sheet comprises a 2-dimensional (2-D) material; wherein the heterostructure comprises, stacked in the following order:
  • PTMC post-transition metal chalcogenide
  • TMDC transition metal dichalcogenide
  • the heterostructure may emit light in a direction parallel to the plane of the sheets of the heterostructure.
  • the TMDC or PTMC may be few-molecular layers thick.
  • the central sheet may be a sheet of a PTM).
  • the central sheet may be a sheet of a TMDC.
  • the heterostructure may further comprise a sheet of TMDC in contact with the sheet of PTMC.
  • the TMDC may be p-doped.
  • the PTMC may be n-doped.
  • a light emitting device comprising a heterostructure comprising a plurality of stacked sheets; wherein each sheet comprises a 2-dimensional (2-D) material; wherein the heterostructure comprises, stacked in the following order: a first sheet that acts as a transparent contact;
  • PTMC post-transition metal chalcogenide
  • TMDC transition metal dichalcogenide
  • the heterostructure may emit light in a direction parallel to the plane of the sheets of the heterostructure.
  • the TMDC or PTMC may be few-molecular layers thick.
  • the central sheet may be a sheet of a PTMC).
  • the central sheet may be a sheet of a TMDC.
  • the heterostructure may further comprise a sheet of TMDC in contact with the sheet of PTMC.
  • the TMDC may be p-doped.
  • the PTMC may be n-doped.
  • the light emitting devices of the second and third aspects typically emit light in the plane of the heterostructure (see figure 5).
  • the PTMC may be InSe or GaSe.
  • the PTMC or TMDC sheets may be optically active with respect to light having a wavelength in the infrared, e.g. far-infrared, range.
  • the embodiments described above for the first aspect under the title Light Emitters’ apply equally to the second and third aspects.
  • the optoelectric device embedded in the core of the first aspect may be an LED device of the second or third aspects.
  • Figure 1 shows the experimental photoluminescence of encapsulated InSe (a) and GaSe (b) as a function of number of layers.
  • Figure 2 shows examples of atomic structure of 2D light emitting diodes (a) Atomic arrangements of 2DM in the heterostructure (b) STEM cross-sectional imaging of the 2D LED (c) Experimental emission spectra for 2D LEDs with different optically active layers
  • Figure 3a shows a general schematic of the active waveguide device of the invention. The top part of outer layers is not shown for simplicity.
  • Figure 3b shows an optical micrograph showing layered hBN/lnSe/hBN heterostructure transferred onto an exposed core of an optical fiber with diameter of 65 pm. Orange and green lines show edges of hBN crystals, blue - monolayer InSe.
  • Figure 4 shows calculated inter-sub-band transition energies (a) and line shapes of InSe (b)
  • Figure 5 shows the in plane emission of InSe of two different thicknesses.
  • Figure 6 shows a schematic of light emitting device based on 2D materials.
  • Figure 7 shows a schematic of optical receiver based on 2D materials
  • Figure 8a shows a schematic of an intermediate waveguide, in which the core has been removed and a device has been transferred onto the device. An optical micrograph of this is shown in figure 3b.
  • Figure 8b shows a schematic of a fibre junction comprising an optoelectric device.
  • Figure 9 shows scanning electron microscope images of various stages in FIB lamella preparation (a) deposition of Pt protective strip and alignment markers, side view; (b) after FIB milling lamella can be seen, top view; (c) lamella is removed using micromanipulator and attached to a sample holder at 90 degree rotation, side view; (d) resulting specimen, top view.
  • Figure 10 shows a schematic representation of experiment on detection of InSe emission propagating long basal plane of the crystal (not to scale)
  • heterostructure refers to a plurality of two-dimensional sheets arranged in a stack.
  • the sheets are arranged such that the heterostructures are substantially parallel and are arranged to be in face-to-face contact with each other, forming a laminate.
  • each individual sheet in the heterostructure will be a single crystal of the 2D- material but it may be that each sheet is made of a plurality of smaller nanoplatelets of the 2D-material. It is possible that any given sheet will comprise a mixture of smaller nanoplatelets of two or more different 2D-materials. Preferably, however, each sheet comprises a single 2D-material.
  • Heterostructures may be formed by placing two-dimensional crystals upon one another mechanically, epitaxially, from solution and/or using any other means which would be apparent to the person skilled in the art.
  • the term‘two-dimensional material’ refers to a large family of crystalline materials with strong anisotropy in chemical bonding, comprised of atoms strongly bonded within molecular layers that are themselves together by weaker van der Waals interactions.
  • a ‘two dimensional material generally means a material which is so thin that it exhibits different properties than the same material when in bulk. Not all of the properties of the material will differ between a two-dimensional material and the same material in bulk but one or more properties are likely to be different.
  • two-dimensional material refers to a material that is in the form of sheets that are 100 or fewer molecular layers thick, e.g. one molecular layer thick, but this depends on the material. Crystals of graphene which have more than 10 molecular layers (i.e. 10 atomic layers) generally exhibit properties more similar to graphite than to graphene. So graphene may be considered to means a material that is less than 10 molecular layers thick. Other 2D materials, such as hBN, PTMCs and TMDCs may be up to 20 molecular layers thick. A molecular layer is the minimum thickness it is possible to obtain that material while only breaking van der Waals interactions.
  • two-dimensional materials are generally in the form of sheets less than 50 nm thick, depending on the material and are preferably less than 20 nm thick.
  • Graphene two-dimensional sheets are generally less than 3.5 nm thick and may be less than 2 nm thick.
  • heterostructures of the invention include graphene, hBN, NbSe2, BhTe3, MgB2, NiTe2, post-transition metal chalcogenides (PTMCs), transition metal dichalcogenide (TMDCs) and layered oxides (e.g. S1O2, AI 2 O 3 , HfC>2, micas, vermiculites).
  • PTMCs post-transition metal chalcogenides
  • TMDCs transition metal dichalcogenide
  • layered oxides e.g. S1O2, AI 2 O 3 , HfC>2, micas, vermiculites.
  • TMDCs are a family of crystalline materials. Their chemical formula is of the type MX 2, where M is a transition metal (Mo, Ta, W, Zr, Hf etc.) and is a chalcogen (S, Se or Te). TMDCs are themselves structured such that each molecular layer of the material consists of three atomic layers: a one atom thick layer of transition metal atoms sandwiched between two one atom thick layers of chalcogen atoms. In one embodiment, the TMDC is a compound of one or more of Mo, Ta, W, Zr, Hf with one or more of S, Se and Te.
  • TMDCs are well known for their outstanding optical properties and have high efficiency for both photodetection and light emission.
  • M0S2 an illustrative TMDC, has a molecular layer thickness of 0.65 nm.
  • PTMCs are a family of crystalline materials group. Their chemical formula is of the type NX, where N is a post transition metal (Ga, In, etc.) and X is a chalcogen (S, Se or Te).
  • TMDCs are themselves structured such that each molecular layer of the material consists of four atomic layers: two one atom thick layers of metal atoms sandwiched between two one atom thick layers of chalcogen atoms. There is strong covalent bonding between the atoms within each molecular layer of the post-transition metal chalcogenide and predominantly weak Van der Waals bonding between adjacent molecular layers.
  • an illustrative TMDC has a molecular layer thickness of 0.8 nm.
  • a layer of graphene consists of a sheet of sp 2 -hybridized carbon atoms. Each carbon atom is covalently bonded to three neighboring carbon atoms to form a
  • graphene is intended to mean a carbon nanostructure with up to 10 graphene molecular layers.
  • Graphene is often referred to as a 2-dimensional structure because it represents a single sheet or layer of carbon of nominal (one atom) thickness.
  • Graphene can be considered to be a single sheet of graphite.
  • the graphene in the heterostructures of the invention is preferably pristine graphene.
  • pristine graphene is that that is obtained without the introduction of heteroatoms (O, N, Cl etc) to or removal of heteroatoms from the carbon network.
  • Pristine graphene may be obtained by mechanical exfoliation or by chemical vapour deposition (CVD).
  • Pristine graphene may be considered to have a oxygen content of less than 5 mol%.
  • the graphene may, on the other hand, be a reduced graphene oxide or a partially oxidised graphene oxide having a higher oxygen content.
  • Graphene is both an excellent conductor and is substantially transparent to actinic radiation, e.g. visible and near visible light. Graphene is also very flexible. Many of its derivatives retain these properties.
  • Graphene also has a variable work function which can be changed easily using electrostatic gating.
  • the graphene in the heterostructures of the invention is a single atomic layer thick. As more layers of graphene are added there is an increase in the amount of absorption. However, it is possible to have a few layers of graphene and thus the invention contemplates 2, 3, 4, and 5 layers. Consequently, the or each graphene sheet is from about 0.3nm to 2nm thick. If the graphene layer is too thick, this results in a large absorption and a loss in
  • this graphene layer could be, for example, up to 50 nm or 100nm thick.
  • modified graphene refers to a graphene-like structure that has been modified in some way.
  • the modified graphene may be graphene which has been doped. This may have the purpose of modifying the work function of graphene without significantly reducing its conductivity.
  • compounds which can be used to dope graphene are: NO2, H2O and I2, which act as acceptors to provide a p-doped graphene; or N H3, CO and C1-C3 alcohols (e.g. ethanol), which act as donors to provide an n-doped graphene. Small amounts of doping can increase the transparency of the doped graphene relative to graphene but the dopant itself may absorb or reflect light.
  • a preferred dopant is one which is not chemically bonded to graphene but which is able to transfer charge to graphene, effectively altering the graphene’s work function.
  • a 2D material is indicated as being‘few layers thick’, this means that the material is in the range from 2 to 5 layers thick. Thus, if a material is indicated as being a few atomic layers thick, the material is in the range from 2 to 5 atomic layers thick. If a material is indicated as being a few molecular layers thick, the material is in the range from 2 to 5 molecular layers thick.
  • the waveguide of the invention can be fabricated in different ways. If the core manufacturing process does not require high temperatures, e.g. where the core is made of a polymer, the optical device can be embedded during the core manufacturing process, e.g. by allowing molten polymer to set around the device or by curing uncured polymer around the device. For other materials, e.g. silica, the optical device can be embedded into the waveguide as follows: Remove a section of the core or split it in two, for example using a laser cutter. The pre-fabricated optical device (descriptions of how the optical devices might be made can be found in the prior art provided elsewhere in this specification) is then transferred onto the open segment of the core.
  • the pre-fabricated optical device (descriptions of how the optical devices might be made can be found in the prior art provided elsewhere in this specification) is then transferred onto the open segment of the core.
  • the removed section can then be replaced or the two halves of the core can be reunited to restore core’s integrity.
  • This latter step may require the use of an adhesive to make the core sufficiently robust.
  • the core may then be coated as required. Where contacts are required, these can be in the form of conductive pads (most likely thin metal layer, e.g. gold) deposited or transferred onto the core or onto the protective cladding.
  • JP 2014052530 each provide means by which an optoelectric device may be integrated into an optical fibre.
  • hBN refers to hexagonal boron nitride, a 2D material having molecular layers that are a single atom thick (0.3 nm).
  • the term‘transparent’ means that light passes through a sheet of material. It is not necessarily the case that all light passes through the sheet that is considered to be transparent.
  • a sheet of single atomic layer graphene, for example, is considered to be transparent but absorbs about 2% of light that passes through. In thicker graphene, each layer absorbs about 2% of the light that passes through.
  • The‘transparency’ of any given material is dependent on the thickness of the material.
  • the term‘transparent’ is considered to mean that a sheet absorbs less than 25% of the light that passes through, e.g. less than 10% of the light that passes through.
  • Infrared light is generally considered to be that having a wavelength in the range 700 n to 1 millimeter mm.
  • Far infrared light is generally considered to be that having a wavelength in the range 15 pm to 1 millimeter .
  • Example 1 Preparation of a waveguide of the invention
  • InSe crystals have been cleaved using a process also known as“micromechanical exfoliation” and deposited onto a silicon wafer in inert gas environment to avoid oxidation.
  • Appropriate thicknesses of InSe have been selected using optical contrast in reflected light and subsequently encapsulated in layers of hexagonal boron nitride, using process know as“stamping” or“dry pick-up” technique [Nano Lett. 15, 4914-4921 (2015)].
  • the optical fibre comprised of core (silica) and cladding (2 layers of polymer) have been prepared by polishing (grinding) to cut approximately half way into its diameter.
  • the heterostructure was transferred onto the exposed fibre core while supported by a thin layer of polymer (PMMA). The supporting polymer membrane was then peeled off to release the
  • the core can be restored to its original shape using focused ion beam (FIB) deposition of S1O2.
  • FIB focused ion beam
  • Example 2 preparation and testing of an in plane InSe light emitting heterostructure
  • hBN/lnSe/hBN heterostructure was assembled on oxidised silicon wafer in argon environment. Two thicknesses of InSe were selected: 3 and 10 layers; while relatively thick hBN was used for encapsulation on both sides (bottom ⁇ 50 nm, top 100- 200 nm). Thick hBN was picked to protect the InSe from the following FIB treatment. In addition, the following layers were deposited on top: 3nm AuPd uniform film + 1 micrometre of Pt in a narrow strip (1 pmx1 pmx20pm) to provide conductive layer for discharging and further protect the specimen (result shown in Figure 9a).

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Abstract

La présente invention concerne des guides d'ondes optiques qui ont des dispositifs opto-électriques actifs intégrés dans leur cœur. Les dispositifs opto-électriques émettent typiquement de la lumière et/ou détectent la lumière et comprennent des hétérostructures constituées de matériaux bidimensionnels. Les parties optiquement actives de l'hétérostructure 2D peuvent comprendre des feuilles bidimensionnelles de dichalcogénures de métaux de transition ou de chalcogénures de métaux de post-transition.
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WO2023239543A3 (fr) * 2022-05-19 2024-03-28 The Administrators Of The Tulane Educational Fund Photovoltaïques à jonction schottky de grande surface utilisant des dichalcogénures de métaux de transition

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113865702A (zh) * 2021-09-02 2021-12-31 暨南大学 一种具有起偏功能的光纤集成光电探测器
CN113865702B (zh) * 2021-09-02 2024-04-30 暨南大学 一种具有起偏功能的光纤集成光电探测器
WO2023239543A3 (fr) * 2022-05-19 2024-03-28 The Administrators Of The Tulane Educational Fund Photovoltaïques à jonction schottky de grande surface utilisant des dichalcogénures de métaux de transition

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