A graphene long-wave infrared tunable surface phonon-plasmon coupled device

Abstract

The application belongs to the technical field of infrared modulation devices, and discloses a graphene long-wave infrared tunable surface phonon-plasmon coupling device, which comprises, from bottom to top, a substrate layer (1), a dielectric layer (2), a graphene layer (3) and a metal structure layer; wherein the substrate layer is a SiC homoepitaxial wafer, which comprises, from bottom to top, a heavily doped SiC substrate (101) and a SiC epitaxial layer (103); the doping concentration of the heavily doped SiC substrate is not lower than 1*10 18 cm ‑3 ; and the SiC epitaxial layer is in an intrinsic state or in a lightly doped state with a doping concentration not higher than 1*10 17 cm ‑3 . The obtained device can be regulated by combining a continuous pump light source (such as an ultraviolet continuous laser, an LED, etc.), a built-in electric field and an external electric field, has low pump power density, small thermal effect and low cost, solves the problem of difficult regulation of existing graphene and SiC integrated devices, and realizes the steady-state response regulation of the SiC surface phonon mode.

Description

Technical Field

[0001] This invention belongs to the field of infrared modulation device technology, and more specifically, relates to a graphene long-wave infrared tunable surface phonon-plasm coupling device. Background Technology

[0002] Long-wave infrared (wavenumber 714–1250 cm⁻¹) -1 Optical technology is widely used in military and civilian fields, such as environmental monitoring, low-light night vision, communication, navigation, and tracking. Among these, long-wave infrared modulation devices play a crucial role in signal sensing and processing, and are one of the core components of infrared systems. In recent years, the optical properties of SiC polar dielectrics have attracted considerable attention. Compared to surface plasmons in metals, SiC exhibits superior optical properties within its afterglow band (797–973 cm⁻¹). -1 The surface phonon modes supported by these modes typically have stronger field confinement and lower optical loss, which brings new opportunities and challenges to the development of long-wave infrared tunable devices.

[0003] Existing technologies have been used to study the application of SiC materials in long-wavelength infrared tunable devices. However, these studies often require high peak power laser sources for modulation, resulting in high costs and a significant gap from practical commercial applications. For example, the paper "Active tuning of surface phonon polariton resonances via carrier photoinjection" (Nature Photonics, 2018, 12:50-56) discloses a SiC nanopillar surface phonon modulation device that uses an ultraviolet femtosecond pulsed pump laser to increase the carrier concentration of the entire semiconductor layer, thereby achieving transient modulation of the surface phonon mode. However, this device requires a high level of carrier injection, which cannot be achieved through continuous pumping and can only rely on high peak power pulsed lasers. Therefore, the device cannot achieve steady-state response modulation of the surface phonon mode, which undoubtedly limits its practical application range. Furthermore, the femtosecond pumping requirement increases operating costs and complicates the device system. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a graphene long-wavelength infrared tunable surface phonon-plasmic coupling device. This device utilizes an improved structure, employing a SiC homoepitaxial wafer comprising a heavily doped SiC substrate and a lightly doped SiC epitaxial layer as the substrate (wherein the doping concentration of the heavily doped SiC substrate is not less than 1 × 10⁻⁶). 18 cm -3 The doping concentration of the lightly doped SiC epitaxial layer is no higher than 1×10⁻⁶. 17 cm-3 Both have the same doping type, for example, both can be preferably N-type doped; of course, the lightly doped SiC epitaxial layer can also be an intrinsic state. The graphene long-wave infrared tunable surface phonon-plasm coupling device formed by the combination of dielectric layer, graphene layer and metal structure layer can be controlled by combining continuous pump light source (such as ultraviolet continuous laser, LED, etc.), built-in electric field and external electric field. It has low pump power density, small thermal effect and low cost, which solves the problem of difficult control of existing graphene and SiC integrated devices, and realizes steady-state response control of SiC surface phonon mode.

[0005] To achieve the above objectives, according to one aspect of the present invention, a graphene long-wave infrared tunable surface phonon-plasm coupling device is provided, characterized in that it comprises, from bottom to top, a substrate layer (1), a dielectric layer (2), a graphene layer (3), and a metal structure layer; wherein,

[0006] The substrate (1) is a SiC homoepitaxial wafer, comprising, from bottom to top, a heavily doped SiC substrate (101) and a SiC epitaxial layer (103); the doping concentration of the heavily doped SiC substrate (101) is not less than 1×10⁻⁶. 18 cm -3 The SiC epitaxial layer (103) is either an intrinsic state or has a doping concentration not exceeding 1×10⁻⁶. 17 cm -3 The SiC epitaxial layer (103) is in a lightly doped state; and when the SiC epitaxial layer (103) is in a lightly doped state, the doping type of the heavily doped SiC substrate (101) and the SiC epitaxial layer (103) is the same.

[0007] The metal structure layer includes a two-dimensional metal grating (4), a source (401), and a drain (402); the two-dimensional metal grating (4) is distributed directly above the graphene layer (3); for either the source (401) or the drain (402), a portion of it is in contact with the graphene layer (3), and the other portion is in contact with the dielectric layer (2).

[0008] As a further preferred embodiment of the present invention, both the heavily doped SiC substrate (101) and the SiC epitaxial layer (103) are N-type doped.

[0009] As a further preferred embodiment of the present invention, the heavily doped SiC substrate (101) and the SiC epitaxial layer (103) have the same crystal form, both being 4H or 6H crystal form.

[0010] As a further preferred embodiment of the present invention, the thickness of the heavily doped SiC substrate (101) is greater than 300 μm; and the thickness of the SiC epitaxial layer (103) is 5 to 10 μm.

[0011] As a further preferred embodiment of the present invention, the dielectric layer (2) is an AlN, Al2O3, MgF2 or SiO2 thin film with a thickness of 30 to 200 nm; preferably an AlN thin film.

[0012] As a further preferred embodiment of the present invention, the number of graphene layers (3) is not higher than 10, and is preferably a single-layer graphene.

[0013] As a further preferred embodiment of the present invention, the thickness of the two-dimensional metal grating (4) is 100-150 nm, the period is 5-10 μm, and the duty cycle is 50%-90%; preferably, it includes 20-40 periods.

[0014] As a further preferred embodiment of the present invention, the thickness of the source electrode (401) and the drain electrode (402) are the same as the thickness of the two-dimensional metal grating (4).

[0015] According to another aspect of the present invention, a method for controlling the above-mentioned graphene long-wave infrared tunable surface phonon-plasm coupling device is provided, characterized in that the control is performed by a continuous pump light source; the continuous pump light source is capable of providing photon energy greater than the bandgap of 4H-SiC or 6H-SiC.

[0016] Preferably, in addition to continuous light pumping of the light source for control, an external electric field is also used for control.

[0017] More preferably, the continuous pump light source is an ultraviolet LED light source or a continuous laser.

[0018] Compared with the prior art, the above technical solutions conceived in this invention can achieve the following results.

[0019] Beneficial effects:

[0020] (1) The graphene long-wave infrared tunable surface phonon-plasmic coupling device proposed in this invention uses a SiC homoepitaxial wafer comprising a heavily doped SiC substrate and a lightly doped SiC epitaxial layer as the substrate layer, wherein the doping concentration of the heavily doped SiC substrate is not less than 1×10⁻⁶. 18 cm -3 The doping concentration of the lightly doped SiC epitaxial layer is no higher than 1×10⁻⁶. 17 cm -3Both have the same doping type (considering the practical cost of N-type and P-type doping, N-type doping is preferred). During operation, based on the interface light-gated effect, the lightly doped SiC epitaxial layer can absorb pump light radiation (e.g., ultraviolet radiation) and generate photogenerated carriers. Under the influence of a built-in or external electric field, photogenerated holes and electrons separate, thereby inducing highly localized carrier aggregation in the graphene and SiC depletion layers to alter their doping characteristics. Therefore, effective control of the mixed surface phonon-plasmic mode can be achieved, significantly improving the control performance of graphene-SiC integrated devices. The doping concentration of the lightly doped SiC epitaxial layer is no higher than 1 × 10⁻⁶. 17 cm -3 The lower the doping concentration of the epitaxial layer, the lower the optical loss it introduces (for example, the doping concentration of a lightly doped SiC epitaxial layer can be as low as close to the intrinsic state, or even be an undoped intrinsic state).

[0021] (2) The graphene long-wave infrared tunable surface phonon-plasm coupling device proposed in this invention uses a SiC homoepitaxial wafer comprising a heavily doped SiC substrate and a lightly doped SiC epitaxial layer as the substrate. Due to the interface light gating effect employed, it has a strong weak light detection capability. Compared with the prior art (Nature photonics, 2018, 12:50-56), it can achieve steady-state response modulation of surface phonon modes with a lower pump light power density. In particular, it can use commonly available ultraviolet LEDs as a continuous pump light source. In the prior art, SiC homoepitaxial wafers are often used to fabricate high-temperature, high-pressure, and high-power semiconductor devices. This invention is the first to use it for long-wave infrared phonon modulation devices and can significantly improve the modulation performance of the device.

[0022] The device of this invention can be modulated by combining a pump source, a built-in electric field, and an external electric field. The built-in electric field is determined by the lightly doped SiC epitaxial layer and the dielectric layer, and is fixed once the device is constructed. Therefore, in practical use, the constructed device can be modulated by combining a pump source and an external electric field (the external electric field can be controlled by the gate voltage). Alternatively, it can be modulated solely by the pump source without applying an external electric field. This invention is suitable for applications where the pump source is continuous light, has low pump power density, minimal thermal effect, and low cost.

[0023] (3) In particular, the present invention can use AlN thin film as the dielectric layer in the device. AlN crystal has low optical loss in the long-wave infrared band and the lattice mismatch rate with SiC is only 1%. The AlN thin film epitaxially grown on the SiC substrate will have high crystal quality and good electrical insulation, which is more conducive to the function of graphene long-wave infrared tunable surface phonon-plasm coupling device.

[0024] (4) The graphene long-wave infrared tunable surface phonon-plasm coupling device proposed in this invention can tune graphene to its intrinsic state by utilizing the interface light gating effect and improve the absorption rate of intrinsic graphene by utilizing the phonon polarization mode of the polar medium, which helps to realize a high-performance intrinsic graphene infrared detector.

[0025] (5) The graphene long-wave infrared tunable surface phonon-plasmonic coupling device of this invention has a layered structure, which is simple in structure and compatible with third-generation semiconductor processing technology. This device can significantly improve the tuning performance of graphene and SiC integrated devices. It can not only achieve steady-state response tuning of surface phonon modes, but also tune graphene to its intrinsic state, providing a new approach for tuning phonon polarization modes in polar media. This is of great significance to the development of tunable infrared devices and intrinsic graphene infrared detectors.

[0026] The graphene long-wave infrared tunable surface phonon-plasmonic coupling device proposed in this invention features a SiC material with a negative real part of its dielectric constant within the afterglow band. The lightly doped SiC epitaxial layer reduces optical losses introduced by charge carriers. Combined with a dielectric layer (e.g., AlN, Al2O3, MgF2, or SiO2 thin film; particularly AlN dielectric, which exhibits lower optical losses in the long-wave infrared band), surface phonon modes at the dielectric layer / SiC interface are easily excited under long-wave infrared irradiation. The required additional wave vector is provided by a two-dimensional metal grating. This two-dimensional metal grating can also form a metal-insulator-metal-like structure with the dielectric layer / SiC, supporting magnetic localization modes derived from the interaction between metal surface plasmons and SiC optical phonons. Furthermore, both the magnetic and surface phonon modes in this heterostructure can couple with graphene surface plasmons to form hybrid surface phonon-plasmonic modes, and the optical phonons in the SiC material can couple with free charge carriers, causing a change in its dielectric constant. Therefore, by utilizing the interfacial optical gating effect to alter the carrier concentration or doping characteristics of the graphene channel and the SiC depletion region, the hybrid surface phonon-plasmic mode can be effectively controlled. Furthermore, the structural parameters of the graphene long-wavelength infrared tunable surface phonon-plasmic coupling device proposed in this invention can be further optimized through simulation and scanning using the finite-difference time-domain method to meet different practical application requirements. Attached Figure Description

[0027] Figure 1 This is a top view schematic diagram of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided by the present invention.

[0028] Figure 2 for Figure 1 The diagram shows a cross-sectional view of the graphene long-wave infrared tunable surface phonon-plasm coupling device along the dashed line A.

[0029] Figure 3 The Raman spectrum of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 1 is shown.

[0030] Figure 4 The graph shows the transfer characteristics and gate current curve of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 1.

[0031] Figure 5 The reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 1 (gate voltage is 20V).

[0032] Figure 6 The reflectance spectra of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 1 under different gate voltages with pump light.

[0033] Figure 7 The reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 2 (gate voltage is 20V).

[0034] Figure 8 The reflectance spectra of the graphene long-wave infrared tunable surface phonon-plasm coupling device provided in Example 2 under different gate voltages with pump light.

[0035] Figure 1 , Figure 2 The meanings of the reference numerals in the figures are as follows: 1-substrate layer, 101-heavily doped SiC substrate, 102-SiC buffer layer, 103-SiC epitaxial layer (i.e., lightly doped SiC epitaxial layer), 2-dielectric layer (e.g., AlN dielectric layer), 3-graphene layer (e.g., monolayer graphene), 4-two-dimensional metal grating, 401-source, 402-drain. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1

[0038] The graphene long-wave infrared tunable surface phonon-plasmic coupling device in this embodiment includes, from bottom to top, a substrate layer 1, a dielectric layer 2, a graphene layer 3, and a metal structure layer; its top view is shown below. Figure 1 As shown, the metal structure layer includes a two-dimensional metal grating 4, a source electrode 401, and a drain electrode 402.

[0039] Example 1 describes the fabrication of a graphene long-wave infrared tunable surface phonon-plasmic coupling device using commercially available SiC homoepitaxial wafers. The crystal type is 4H, purchased from Beijing Century Golden Light Semiconductor Co., Ltd. The heavily doped SiC substrate 101 has a thickness of 350 μm (according to the manufacturer's information, the resistivity of this heavily doped SiC substrate 101 is 0.015–0.025 Ω·cm, and the doping concentration is 1 × 10⁻⁶). 18 ~1×10 19 cm -3 The epitaxial layer 103 has a thickness of 6.5 μm and a doping concentration of 1 × 10⁻⁶. 16 cm -3 Both the substrate and epitaxial layers are doped with nitrogen atoms, and both exhibit N-type conductivity. However, due to practical limitations in epitaxial growth, existing commercially available SiC homoepitaxial wafers often include a thin SiC buffer layer between the heavily doped SiC substrate and the lightly doped SiC epitaxial layer to ensure the crystal quality of the lightly doped SiC epitaxial layer. In this embodiment, the buffer layer 102 of the commercially available SiC homoepitaxial wafer has a thickness of 1 μm and a doping concentration of 1 × 10⁻⁶. 18 cm -3 The dopants in the buffer layer are also nitrogen atoms, and the conductivity type is N-type.

[0040] Along Figure 1 The cross-sectional view along the axis indicated by the dashed line A is as follows: Figure 2 As shown; the substrate 1 includes a heavily doped SiC substrate 101, a SiC buffer layer 102, and a lightly doped SiC epitaxial layer 103.

[0041] The device in this embodiment is fabricated using the aforementioned commercial SiC homoepitaxial wafer. An AlN thin film is grown on the lightly doped SiC epitaxial layer as the dielectric layer 2 using metal-organic chemical vapor deposition (MOCVD). A single layer of graphene 3 is transferred onto the dielectric layer 2 using a wet transfer technique. In this embodiment, the dielectric layer 2 has a thickness of 100 nm, and the graphene layer 3 is a single layer with a thickness of 0.34 nm.

[0042] Next, an electron beam lithography (EBL) and electron beam thermal evaporation (EBE) machine are used to fabricate the metal structure layer of the device, forming a two-dimensional metal grating layer 4, a source electrode 401, and a drain electrode 402. Finally, an EBE machine is used to fabricate the gate electrode on the back side of the device before encapsulation and wire bonding. In this embodiment, the two-dimensional metal grating layer and the source / drain electrodes have the same thickness, 100 nm; a portion of the source / drain electrodes is in contact with the graphene layer, and another portion is in contact with the dielectric layer; the two-dimensional metal grating layer has a period of 5 μm, a duty cycle of 90%, and a total of 24 periods.

[0043] Performance testing:

[0044] The Raman spectrum of the graphene long-wave infrared tunable surface phonon-plasmite coupling device obtained in Example 1 is as follows: Figure 3 As shown, the Raman spectra of graphene and AlN / SiC overlap significantly, causing the G peak of graphene to be submerged; the characteristic spectrum of graphene after subtracting the Raman signal of AlN / SiC is shown in the figure. Figure 3 As shown in the illustration, the G peak and 2D peak of graphene are located at 1593 cm⁻¹. -1 and 2684cm -1 The graphene is located near the same area, and the intensity ratio of the two is about 1 / 1.8, indicating that the graphene is a single layer; the characteristic Raman spectrum of the graphene does not have an obvious D peak, indicating that the graphene has a high quality.

[0045] For the graphene long-wave infrared tunable surface phonon-plasmonic coupling device obtained in Example 1, an existing ultraviolet LED was used as the continuous pump source for the device, with a peak wavelength of 365 nm. Its photon energy (3.40 eV) is greater than the band gap of 4H-SiC (3.23 eV), which can excite electrons in the valence band of 4H-SiC to the conduction band, thereby generating photogenerated carriers. The vertical illumination power density of the pump source is 30-40 mW / cm². -2 .

[0046] For the graphene long-wave infrared tunable surface phonon-plasm coupling device obtained in Example 1, the transfer characteristics and gate current curves were tested using a common source connection method. The positive and negative terminals of one digital source meter were connected to the drain and source terminals of the device, respectively, and the positive and negative terminals of another digital source meter were connected to the gate and source terminals of the device, respectively. For the reflectivity spectrum test of the device, it is only necessary to connect the positive and negative terminals of one digital source meter to the gate and source terminals of the device, respectively.

[0047] Using the same ultraviolet LED as the pump light source, the transfer characteristics and gate current curves of the graphene long-wave infrared tunable surface phonon-plasm coupling device obtained in Example 1 are as follows: Figure 4As shown, the drain-source bias voltage is fixed at 50mV. Without pump light, as the gate voltage increases, the lightly doped SiC epitaxial layer 103 is continuously depleted, leading to a continuous decrease in the total gate capacitance. The drain-source current of the device does not change significantly, and the device's tunability is suppressed. When pump light is present, the lightly doped SiC epitaxial layer 103 absorbs the pump light and generates photogenerated carriers. Under the combined action of the built-in electric field and the external electric field (gate voltage), photogenerated electrons and holes separate, with a large number of holes concentrated in the lightly doped SiC epitaxial layer 103. At the interface between AlN dielectric layer 2 and AlN dielectric layer 3, the drain-source current of the device changes significantly. The doping characteristics of the graphene channel and the SiC depletion region also change significantly. The graphene layer can even be tuned to the Dirac point position, corresponding to its intrinsic state. In addition, during the application of the gate voltage, the gate current of the device is always less than 1 nA, which is due to the good crystal quality and electrical insulation of the AlN dielectric layer. The asymmetry of the gate voltage that can be applied in the forward and reverse directions of the device originates from the heterojunction barrier between AlN and SiC.

[0048] Using the same ultraviolet LED as the pump source, the reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasm coupling device obtained in Example 1 is as follows: Figure 5 As shown, in the absence of pump light and with a gate voltage of 20V, a surface phonon-plasmic coupling mode is formed in the heterostructure composed of the two-dimensional metal grating layer 4, graphene layer 3, AlN dielectric layer 2, and substrate layer 1, with two strong peaks located at points a1 and b1, respectively. When pump light is present and the gate voltage is 20V, under the action of the gate voltage and the built-in electric field, photogenerated electrons and holes in the lightly doped SiC epitaxial layer 103 are separated, which significantly changes the doping characteristics of the graphene channel and the SiC depletion region, and the two strong peaks shift to points a2 and b2, respectively.

[0049] Using the same ultraviolet LED as the pump light source, the reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasmoid coupling device obtained in Example 1 under different gate voltages with pump light is shown below. Figure 6 As shown. Without pump light, the gate voltage causes the lightly doped SiC epitaxial layer 103 to be continuously depleted, suppressing the device's tunability, and its reflectivity spectrum remains almost unchanged. However, when pump light is present, under the influence of the gate voltage and the built-in electric field, photogenerated electrons and holes in the lightly doped SiC epitaxial layer 103 are separated, significantly altering the doping characteristics of the graphene channel and the SiC depletion region, thus greatly improving the device's tuning performance. Figure 6As shown, when the gate voltage is -4V, the two strong surface phonon-plasmic coupling mode peaks are located at points c1 and d1, respectively. As the gate voltage increases, the c1 peak is greatly affected by the doping characteristics of the SiC depletion region and continues to undergo a blue shift. The d1 peak is greatly affected by the doping characteristics of the graphene channel and begins to undergo a red shift. When the gate voltage increases and causes the graphene to cross its Dirac point, the d1 peak undergoes a blue shift.

[0050] Example 2

[0051] This embodiment 2 is largely the same as embodiment 1, except for the parameters of the metal structure layer; in embodiment 2, the period of the two-dimensional metal grating is 10 μm, the duty cycle is 57.5%, and there are a total of 35 periods.

[0052] Using the same ultraviolet LED as the pump source, the reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasm coupling device obtained in Example 2 is as follows: Figure 7 As shown, in the absence of pump light and with a gate voltage of 20V, a surface phonon-plasmic coupling mode is formed in the heterostructure composed of the two-dimensional metal grating layer 4, graphene layer 3, AlN dielectric layer 2, and substrate layer 1, with two strong peaks located at points a3 and b3, respectively. When pump light is present and the gate voltage is 20V, under the action of the gate voltage and the built-in electric field, photogenerated electrons and holes in the lightly doped SiC epitaxial layer 103 are separated, which significantly changes the doping characteristics of the graphene channel and the SiC depletion region, and the two strong peaks shift to points a4 and b4, respectively.

[0053] Using the same ultraviolet LED as the pump light source, the reflectance spectrum of the graphene long-wave infrared tunable surface phonon-plasmoid coupling device obtained in Example 2 under different gate voltages with pump light is shown below. Figure 8 As shown. Without pump light, the gate voltage causes the lightly doped SiC epitaxial layer 103 to be continuously depleted, suppressing the device's tunability, and its reflectivity spectrum remains almost unchanged. However, when pump light is present, under the influence of the gate voltage and the built-in electric field, photogenerated electrons and holes in the lightly doped SiC epitaxial layer 103 are separated, significantly altering the doping characteristics of the graphene channel and the SiC depletion region, thus greatly improving the device's tuning performance. Figure 8 As shown, when the gate voltage is -4V, the two strong surface phonon-plasmic coupling mode peaks are located at points c2 and d2, respectively. As the gate voltage increases, the c2 peak is greatly affected by the doping characteristics of the SiC depletion region and continues to undergo a blue shift. The d2 peak is greatly affected by the doping characteristics of the graphene channel and begins to undergo a red shift. When the gate voltage increases and causes the graphene to cross its Dirac point, the d2 peak undergoes a blue shift.

[0054] The above embodiments are merely examples. For instance, the doping concentration of the lightly doped SiC epitaxial layer 103 can also be less than 1 × 10⁻⁶. 17 cm -3 Other concentrations are possible, even intrinsic states; the thickness can also be flexibly adjusted. The thickness of the source / drain electrodes and the two-dimensional metal grating can be kept consistent, which simplifies the device fabrication process (of course, inconsistency does not affect device operation, but the fabrication process will be slightly more complex).

[0055] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A graphene long-wave infrared tunable surface phonon-plasmon coupled device, characterized in that, From bottom to top, it includes a base layer (1), a dielectric layer (2), a graphene layer (3), and a metal structure layer; among which, The substrate (1) is a SiC homoepitaxial wafer, comprising, from bottom to top, a heavily doped SiC substrate (101) and a SiC epitaxial layer (103); the doping concentration of the heavily doped SiC substrate (101) is not less than 1. 10 18 cm -3 The SiC epitaxial layer (103) is either an intrinsic state or has a doping concentration not exceeding 1. 10 17 cm -3 The SiC epitaxial layer (103) is in a lightly doped state; and when the SiC epitaxial layer (103) is in a lightly doped state, the doping type of the heavily doped SiC substrate (101) and the SiC epitaxial layer (103) is the same. The metal structure layer includes a two-dimensional metal grating (4), a source (401), and a drain (402); the two-dimensional metal grating (4) is distributed directly above the graphene layer (3); for either the source (401) or the drain (402), a portion of it is in contact with the graphene layer (3), and the other portion is in contact with the dielectric layer (2); The gate electrode is fabricated on the back side of the device.

2. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The heavily doped SiC substrate (101) and the SiC epitaxial layer (103) are both N-type doped.

3. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The heavily doped SiC substrate (101) and the SiC epitaxial layer (103) have the same crystal form, both being 4H or 6H crystal form.

4. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The thickness of the heavily doped SiC substrate (101) is greater than 300 μm; the thickness of the SiC epitaxial layer (103) is 5~10 μm.

5. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The dielectric layer (2) is an AlN, Al2O3, MgF2 or SiO2 thin film with a thickness of 30~200nm.

6. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 5, characterized in that, The dielectric layer (2) is an AlN thin film.

7. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The number of graphene layers (3) is no more than 10.

8. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 7, characterized in that, The graphene layer (3) is a single layer of graphene.

9. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The thickness of the two-dimensional metal grating (4) is 100~150nm, the period is 5~10μm, and the duty cycle is 50%~90%.

10. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 9, characterized in that, The two-dimensional metal grating (4) comprises 20 to 40 periods.

11. The graphene long-wave infrared tunable surface phonon-plasmic coupling device as described in claim 1, characterized in that, The thickness of the source (401) and the drain (402) is the same as the thickness of the two-dimensional metal grating (4).

12. The method for controlling the graphene long-wave infrared tunable surface phonon-plasm coupling device as described in any one of claims 1-11, characterized in that, The photon energy is controlled by a continuously pumped light source; the continuously pumped light source can provide photon energy greater than the bandgap of 4H-SiC or 6H-SiC.

13. The control method as described in claim 12, characterized in that, In addition to continuous light pumping of the light source, an external electric field is also used for further control.

14. The control method as described in claim 12, characterized in that, The continuous pump light source is an ultraviolet LED light source or a continuous laser.

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