A light-regulated graphene heterojunction transistor and its preparation method

Abstract

A light-controlled graphene heterojunction transistor is characterized by being composed of a gate, an insulating layer, a graphene nanoribbon array, a source electrode, a drain electrode, and an organic semiconductor layer. The insulating layer is disposed on the gate, the graphene nanoribbon array is disposed on the surface of the insulating layer, the source and drain electrodes are disposed on the surface of the graphene nanoribbon array and at both ends along the direction of extension of the graphene nanoribbon array, and the organic semiconductor layer is disposed between the source and drain electrodes, on the surface of the graphene nanoribbon array, and between the bands of the graphene nanoribbon array. The interband width of the graphene nanoribbon array is configured to excite graphene plasmons in the infrared band. The present invention organically combines a graphene metasurface with an organic semiconductor, using infrared light to directly control the Fermi level of graphene, providing a method for controlling the carrier concentration of graphene, thereby achieving flexible control of graphene plasmons in the infrared band.

Description

Technical Field

[0001] The present invention belongs to the field of transistors, and in particular relates to a light-regulated graphene heterojunction transistor and a preparation method thereof. Background Art

[0002] Graphene is a semi-metallic material whose conduction band and valence band intersect at a point (the Dirac point). The Fermi level (EF) of graphene can be dynamically adjusted through electrical or chemical doping, thereby adjusting its optical properties. Specifically, when the incident photon energy is less than 2EF, due to the Pauli exclusion principle, its inter-band transition is prohibited. Graphene's absorption of photons mainly comes from intra-band transitions of free carriers. The graphene plasmons generated by the collective oscillation of graphene free carriers occur in this frequency range, generally in the infrared and terahertz range. Therefore, the Fermi level of graphene can be controlled by applying voltage, thereby regulating graphene plasmons. Graphene plasmons have important applications in biochemical sensors, active devices, spectroscopy, and infrared / terahertz detection.

[0003] Graphene, with its unique electronic band structure and material tunability, demonstrates exceptional plasmon excitation and electromagnetic confinement capabilities in the infrared and terahertz bands. Compared to metals, graphene exhibits lower electromagnetic losses, enabling ultra-high electromagnetic enhancement effects. More importantly, graphene's Fermi level can be tuned via gate voltage, whereas conventional metal plasmons cannot be modulated due to the high electron density of metals. Therefore, graphene opens the possibility of realizing transistor devices with active control mechanisms.

[0004] Currently, actively controllable graphene transistors are primarily traditional electrostatically gated transistors. In 2015, Rodrigo et al. published a paper in Science demonstrating the realization of an actively controllable graphene device in the mid-infrared band. They first fabricated a nanoribbon array on graphene, with the width of the graphene ribbons matching the plasmon wave vector, enabling the excitation of graphene plasmons in the infrared band. They then linearly controlled the Fermi level and charge carrier concentration of the graphene material by applying an external bias voltage. When the bias voltage varied between 20 and 230 V, the resonant frequency of the graphene plasmons could be flexibly adjusted within a wavenumber range of 1450 to 1800, ultimately enabling efficient infrared detection of trace protein molecules.

[0005] Existing actively controlled graphene transistor devices rely primarily on electrical control, achieved by applying a bias voltage to the graphene metasurface to alter its Fermi level. This method requires electrodes to be placed on the device and connected to an external device to apply voltage, making it complex to implement and limiting the modulation range. Summary of the Invention

[0006] The present invention provides a transistor that is different from the existing technology that requires an additional gate to apply a bias voltage to graphene to achieve a control effect. The present invention combines graphene with an organic semiconductor to form a heterojunction structure, and directly uses infrared light to control the carrier concentration in the graphene without connecting to other instruments, thereby obtaining a plasmon response and realizing light control of graphene transistor devices in the infrared band.

[0007] In one aspect, the present invention provides a light-controlled graphene heterojunction transistor, which is made of a gate, an insulating layer, a graphene nanoribbon array, a source electrode, a drain electrode, and an organic semiconductor layer. The insulating layer is provided on the gate electrode, the graphene nanoribbon array is provided on the surface of the insulating layer, the source electrode and the drain electrode are provided on the surface of the graphene nanoribbon array and at both ends along the extension direction of the graphene nanoribbon array, and the organic semiconductor layer is provided between the source electrode and the drain electrode, on the surface of the graphene nanoribbon array, and between the ribbons of the graphene nanoribbon array.

[0008] The interband width of the graphene nanoribbon array is set so that it can excite graphene plasmons in the infrared band.

[0009] Furthermore, the inter-ribbon width of the graphene nanoribbon array is 20 nm to 60 nm, for example, 30 nm, 40 nm, 50 nm, or 60 nm.

[0010] Furthermore, the valence band energy level of the organic semiconductor layer is lower than the Fermi level of graphene.

[0011] Furthermore, the material of the organic semiconductor layer is selected from P3HT, pBTTT, and pDA2T-C16.

[0012] Furthermore, the organic semiconductor layer is replaced by quantum dots.

[0013] Furthermore, the quantum dots are selected from PbS and PbSe.

[0014] Furthermore, the gate material is a silicon wafer.

[0015] Furthermore, the insulating layer is silicon dioxide or calcium fluoride; preferably, the silicon dioxide is a silicon dioxide layer with a thickness of 300 nm.

[0016] Furthermore, the source and drain electrodes are made of conductive metals, preferably gold, silver, or aluminum.

[0017] Another aspect of the present invention provides a method for preparing a light-controlled transistor, the method comprising the following steps:

[0018] S1) obtaining a gate substrate having an insulating layer;

[0019] S2) transferring the single-layer graphene to the surface of the insulating layer;

[0020] S3) etching grooves on the surface of the single-layer graphene to form a graphene array layer;

[0021] S4) using a vacuum evaporation method on the surface of the graphene nanoarray to set a source electrode and a drain electrode at both ends of the graphene nanoarray along the extension direction using a mask,

[0022] S5) Arranging an organic semiconductor layer between the source electrode and the drain electrode, on the surface of the graphene nanoribbon array, and between the ribbons of the graphene nanoribbon array by using a liquid phase deposition method.

[0023] Furthermore, in step S3), grooves are etched on the surface of the monolayer graphene by electron beam etching or oxygen plasma. Preferably, the interband width of the graphene nanoarray is 20 nm to 60 nm, for example, 30 nm, 40 nm, 50 nm, or 60 nm.

[0024] Another aspect of the present invention provides use of the light-regulated graphene heterojunction transistor of the present invention in preparing an infrared light sensor.

[0025] Another aspect of the present invention provides an infrared light sensor, which includes the graphene heterojunction transistor described in the present invention.

[0026] Furthermore, the wavelength of the infrared light is 0.75μm to 1000μm, for example, 0.75μm, 1μm, 1.50μm, 1.50μm, 2μm, 3μm, 4μm, 5μm, 6μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm or any band therebetween.

[0027] In the technical solution of the present invention, the graphene heterojunction transistor does not require gate voltage to be applied through the gate, but instead achieves active light-induced regulation through infrared light illumination. The present invention first directly prepares a nanoribbon array on graphene, and the width of the nanoribbon array will match the graphene plasmon wave vector in the infrared band. Then, an organic semiconductor is deposited on the graphene metasurface. The organic semiconductor absorbs infrared light to generate electron-hole pairs, which are separated at the interface between graphene and the organic semiconductor. Since the valence band energy level of the organic semiconductor is lower than the chemical potential of graphene, the electrons in the graphene are transferred to the valence band of the organic semiconductor, that is, the holes in the valence band of the organic semiconductor are transferred to the graphene. When the photogenerated electrons are captured in the organic semiconductor, due to the electrostatic coupling effect, the negatively charged organic semiconductor introduces holes in the graphene. At the same time, the electrons captured by the organic semiconductor produce a grating effect similar to a gate voltage, thereby causing the Fermi level of graphene to move and increasing the carrier concentration. The purpose of introducing the gate is to improve the performance of the transistor. By applying voltage to the intrinsic graphene, the optimized graphene carrier concentration and plasmon response are obtained to obtain the optimal infrared light regulation effect.

[0028] Beneficial effects

[0029] The present invention organically combines a graphene metasurface with an organic semiconductor, uses infrared light to directly regulate the Fermi level of graphene, provides a method for regulating the carrier concentration of graphene, and further realizes flexible regulation of graphene plasmons in the infrared band.

[0030] The control method of the present invention is simple, does not need to be connected to other external instruments, and does not require other special conditions. After the device is prepared, direct control of graphene plasmons can be achieved.

[0031] In addition, the present invention can use quantum dots (such as PbS) to replace the organic semiconductor layer. The quantum dots absorb infrared light and can also generate electron-hole pairs, thereby moving the Fermi level of graphene.

[0032] More preferably, the present invention can be combined with electric gate regulation to effectively optimize the carrier concentration in graphene, thereby more flexibly adjusting graphene plasmons in the infrared band. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A side view of a transistor structure based on a graphene heterojunction.

[0034] Figure 2 A top view of a transistor structure based on a graphene heterojunction.

[0035] Figure 3Schematic diagram of infrared light modulation in a graphene heterojunction transistor using graphene and organic semiconductor layers. (a) The organic semiconductor (or quantum dot) absorbs infrared light to generate electron-hole pairs, which separate at the interface between the graphene and organic semiconductor (or quantum dot). (b) Because the valence band energy level of the organic semiconductor (or quantum dot) is lower than the chemical potential of graphene, electrons in graphene transfer to the valence band of the organic semiconductor (or quantum dot), and holes in the valence band of the organic semiconductor (or quantum dot) transfer to graphene, shifting the Fermi level of graphene and increasing the carrier concentration. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0037] Combine Figure 1 and 2 The structure and preparation method of the light-regulated graphene heterojunction transistor of the present invention are described.

[0038] In some specific embodiments, the present invention provides a light-regulated graphene heterojunction transistor, which is made of a gate, an insulating layer, a graphene nanoribbon array, a source, a drain and an organic semiconductor layer, wherein an insulating layer is arranged on the gate, a graphene nanoribbon array is arranged on the surface of the insulating layer, a source and a drain are arranged on the surface of the graphene nanoribbon array and at both ends along the extension direction of the graphene nanoribbon array, and an organic semiconductor layer is arranged between the source and the drain, on the surface of the graphene nanoribbon array and between the bands of the graphene nanoribbon array, and the inter-band width of the graphene nanoribbon array is set so that it can excite graphene plasmons in the infrared band.

[0039] The valence band energy level of the organic semiconductor layer is lower than the Fermi level of graphene, and the material of the organic semiconductor layer is selected from P3HT, pBTTT, and pDA2T-C16.

[0040] In some specific embodiments, the organic semiconductor layer may be replaced by quantum dots, which are selected from PbS and PbSe.

[0041] In some specific embodiments, the inter-ribbon width of the graphene nanoribbon array is 20 nm to 60 nm, for example, 30 nm, 40 nm, 50 nm, or 60 nm.

[0042] In some specific embodiments, the gate is a silicon wafer.

[0043] In some specific embodiments, the insulating layer is silicon dioxide or calcium fluoride; preferably, the silicon dioxide is a silicon dioxide layer with a thickness of 300 nm.

[0044] In some specific embodiments, the source and drain electrodes are made of conductive metals, preferably gold, silver, or aluminum.

[0045] The method for preparing a light-controlled graphene heterojunction transistor of the present invention comprises the following steps:

[0046] 1. Place the silicon wafer (containing a 300nm SiO2 layer) substrate in acetone, anhydrous ethanol and ultrapure water in turn for 10 minutes and blow dry with an N2 gun.

[0047] 2. Use wet transfer to transfer the single-layer graphene on the copper base to a clean silicon wafer substrate.

[0048] 3. Use electron beam etching and oxygen plasma technology to etch specific graphene metasurface structures on the graphene surface.

[0049] 4. Using a vacuum evaporation method on the graphene metasurface, a mask is used to set the source and drain at both ends of the graphene nanoarray along the extension direction.

[0050] 5. The organic semiconductor (P3HT) light-absorbing layer is prepared by liquid phase deposition method to complete the preparation of heterojunction transistor devices.

[0051] 6. Place the heterojunction transistor device under an infrared microscope and collect its infrared reflectance spectrum over a 50μm x 50μm area. Adjust the infrared light energy, collecting infrared spectra of the device at various energies and observing the movement of graphene plasmons within the spectrum.

Claims

1. A light-controlled graphene heterojunction transistor, characterized in that: The device is made of a gate, an insulating layer, a graphene nanoribbon array, a source electrode, a drain electrode, and an organic semiconductor layer. The insulating layer is provided on the gate electrode, the graphene nanoribbon array is provided on the surface of the insulating layer, the source electrode and the drain electrode are provided on the surface of the graphene nanoribbon array and at both ends along the extension direction of the graphene nanoribbon array, and the organic semiconductor layer is provided between the source electrode and the drain electrode, on the surface of the graphene nanoribbon array, and between the bands of the graphene nanoribbon array. The inter-band width of the graphene nanoribbon array is set so that it can excite graphene plasmons in the infrared band; The organic semiconductor layer is used to absorb infrared light to generate electron-hole pairs, which are separated at the interface between the graphene nanoribbon array and the organic semiconductor layer; The valence band energy level of the organic semiconductor layer is lower than the Fermi level of graphene.

2. The light-controlled graphene heterojunction transistor according to claim 1, wherein: The material of the organic semiconductor layer is selected from P3HT, pBTTT, and pDA2T-C16.

3. The light-controlled graphene heterojunction transistor according to claim 1, wherein: The width between bands of the graphene nanoribbon array is 20 nm to 60 nm.

4. The light-controlled graphene heterojunction transistor according to claim 1, wherein: The gate material is silicon wafer.

5. The light-controlled graphene heterojunction transistor according to claim 1, wherein: The insulating layer is a silicon dioxide layer and a calcium fluoride layer; The thickness of the silicon dioxide layer is 200nm-400nm.

6. The light-controlled graphene heterojunction transistor according to claim 1, wherein: The organic semiconductor layer is replaced by quantum dots, The quantum dots are selected from PbS and PbSe.

7. The method for preparing the light-controlled graphene heterojunction transistor according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1) obtaining a gate substrate having an insulating layer; S2) transferring the single-layer graphene to the surface of the insulating layer; S3) etching grooves on the surface of the single-layer graphene to form a graphene array layer; S4) using a vacuum evaporation method on the surface of the graphene nanoarray to set a source electrode and a drain electrode at both ends of the graphene nanoarray along the extension direction using a mask, S5) disposing an organic semiconductor layer between the source electrode and the drain electrode, on the surface of the graphene nanoribbon array, and between the ribbons of the graphene nanoribbon array by a liquid phase deposition method; In step S3), grooves are etched on the surface of the monolayer graphene by electron beam etching and oxygen plasma method; The inter-band width of the graphene nanoarrays is 20 nm to 60 nm.

8. Use of the light-regulated graphene heterojunction transistor according to any one of claims 1 to 6 in the preparation of an infrared light sensor.

9. An infrared light sensor, characterized in that: The infrared light sensor comprises the light-regulated graphene heterojunction transistor according to any one of claims 1 to 6.

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