Plasmonic-enhanced 4h-sic msms ultraviolet photodetector with superstructured surface and preparation method thereof

Abstract

The application discloses a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a super-structured surface and a preparation method thereof. The ultraviolet photodetector comprises a 4H-SiC substrate layer, an N-type buffer layer arranged on the 4H-SiC substrate layer, a lightly-doped N-epitaxial layer arranged on the N-type buffer layer, a super-structured surface structure and a graphene transparent electrode arranged on the lightly-doped N-epitaxial layer, wherein the graphene transparent electrode is an interdigital electrode, the super-structured surface structure is located in the gap of the graphene transparent electrode, and an Al nanostructure is arranged on the top of the super-structured surface structure. The application increases the number of photo-generated electron-hole pairs through the super-structured surface, the graphene electrode and the plasmonic-enhanced light absorption, thereby effectively improving the responsivity and quantum efficiency of the device and improving the application performance of the ultraviolet photodetector.

Description

Technical Field

[0001] This invention relates to the field of semiconductor detector technology, and more specifically, to a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface and its fabrication method. Background Technology

[0002] With the rapid development of semiconductor technology, semiconductor ultraviolet photodetectors have emerged. 4H-SiC is a wide bandgap semiconductor material with excellent properties such as a large bandgap, high critical breakdown electric field, high thermal conductivity, high electron saturation drift velocity, and strong radiation resistance. 4H-SiC has become the preferred semiconductor material for preparing ultraviolet photodetectors, mainly because: (1) 4H-SiC substrates and homoepitaxial growth have high quality. Currently, mass production of 8-inch substrates and epitaxy has been achieved, and the density of various defects has been significantly reduced, resulting in a relatively long photogenerated carrier lifetime for SiC detectors. (2) SiC is an indirect bandgap semiconductor with a small absorption coefficient and less surface absorption, resulting in high efficiency in the generation and separation of photogenerated carriers. (3) SiC materials can directly grow high-quality SiOx layers at high temperature through thermal oxidation on their Si surfaces, which can effectively passivate the dangling bonds on the surface, thereby reducing leakage current. (4) The fabrication process of SiC photodetectors is also relatively mature and has good compatibility with silicon processes. It is expected to prepare detectors with larger photosensitive areas, and the yield of devices is higher, which is also more conducive to commercial production.

[0003] Therefore, ultraviolet photodetectors made of 4H-SiC material will have advantages such as low dark current, high response speed, high detection sensitivity, and high stability.

[0004] However, with the rise of many emerging industries, the demand for higher device performance is increasing. Traditional MSM ultraviolet detectors have low responsivity. To improve the detector's responsivity, surface structuring methods, such as surface plasmon resonance enhancement, can be used. Therefore, plasmon-enhanced 4H-SiC MSM photodetectors with metasurfaces are of great significance for improving the performance of 4H-SiC ultraviolet photodetectors. Summary of the Invention

[0005] To address the aforementioned technical problems in related technologies, this invention proposes a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface and its fabrication method, which can overcome the above-mentioned shortcomings of the prior art.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is implemented as follows:

[0007] A plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface includes a 4H-SiC substrate, an N-type buffer layer on the 4H-SiC substrate, a lightly doped N-epitaxial layer on the N-type buffer layer, a metasurface structure and a graphene transparent electrode on the lightly doped N-epitaxial layer, the graphene transparent electrode being an interdigitated electrode, the metasurface structure being located in the gaps between the graphene transparent electrode, and an Al nanostructure on the top of the metasurface structure.

[0008] Furthermore, the metasurface structure is a tilted mesa grating structure, a nanoporous structure, or a nanopillar structure.

[0009] Furthermore, the mesa width of the grating structure is 50nm-500nm, and the spacing between the grating structures is 100nm-1000nm.

[0010] Furthermore, the Al nanostructure is disk-shaped, triangular prism-shaped, or spherical.

[0011] Furthermore, the metasurface structure and Al nanostructure are located in the gaps between the graphene transparent electrode.

[0012] According to another aspect of the present invention, a method for fabricating a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface is provided, the method comprising the following steps:

[0013] S1 is grown on a 4H-SiC substrate by chemical vapor deposition, followed by homogeneous growth of an N-type buffer layer and an N-epitaxial layer, and then RCA standard cleaning.

[0014] S2 etches metasurface structures using photolithography and ICP etching techniques;

[0015] S3 grows a silicon dioxide passivation layer on the device surface using a thermal oxidation method;

[0016] S4 uses photolithography to etch away the silicon dioxide at the interdigitated electrode positions and transfer graphene material to form a transparent graphene electrode.

[0017] S5 utilizes electron beam evaporation of Al metal films on metasurface structures, followed by thermal annealing to form Al nanostructures.

[0018] Furthermore, the doping concentration of the N-type buffer layer is 1×10⁻⁶. 18 cm -3 - 2×10 20 cm -3 The thickness is 0.5μm-2μm.

[0019] Furthermore, the doping concentration of the N-epipolar layer is 1×10⁻⁶. 15 cm -3 - 1×10 17 cm -3 The thickness is 2μm-20μm.

[0020] Furthermore, the deposition thickness of the Al metal film is 5nm-50nm.

[0021] Furthermore, the thickness of the silicon dioxide passivation layer is 10-100 nm.

[0022] The beneficial effects of this invention are as follows: A metasurface with tilted mesa is formed through photolithography and ICP etching. A passivation layer of silicon dioxide is thermally oxidized on the surface, which reduces the reflection of incident light, allowing more ultraviolet light to be absorbed by the device. When graphene is transferred to the surface, some of it forms interdigitated electrodes, enhancing the absorption of ultraviolet light. At the same time, the passivation layer remaining on the sidewalls of the tilted mesa increases the photosensitive area of ​​the device. Finally, due to the presence of Al nanostructures on the metasurface, localized surface plasmon resonance is induced under the action of incident light, enhancing the absorption of ultraviolet photons. The metasurface, graphene electrodes, and plasmon-enhanced light absorption increase the number of photogenerated electron-hole pairs, thereby effectively improving the responsivity and quantum efficiency of the device and enhancing the application performance of the ultraviolet photodetector. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a cross-sectional schematic diagram of a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface according to an embodiment of the present invention.

[0025] Figure 2 This is a top view of a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface according to an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0027] The plasmon-enhanced 4H-SiC MSM ultraviolet photodetector with metasurface according to an embodiment of the present invention includes a 4H-SiC substrate layer 1, an N-type buffer layer 2 disposed on the 4H-SiC substrate layer 1, a lightly doped N-epitaxial layer 3 disposed on the N-type buffer layer 2, a metasurface structure 4 and a graphene transparent electrode 5 disposed on the lightly doped N-epitaxial layer 3, the graphene transparent electrode 5 being an interdigitated electrode, the metasurface structure 4 being located in the gaps between the graphene transparent electrode 5, and an Al nanostructure 6 disposed on the top of the metasurface structure 4 for improving the photosensitive area and the transmittance of ultraviolet light.

[0028] The metasurface structure 4 is a tilted mesa grating structure, a nanoporous structure, or a nanopillar structure. The Al nanostructure 6 is disk-shaped, triangular prism-shaped, or spherical.

[0029] The metasurface structure 4 and Al nanostructure 6 are located in the gap between the graphene transparent electrode 5, which enables a more uniform electric field distribution.

[0030] The fabrication method of the above-mentioned plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with metasurface includes the following steps:

[0031] S1 An N-type buffer layer 2 and an N-epitaxial layer 3 are sequentially grown on a 4H-SiC substrate 1 using chemical vapor deposition, followed by RCA standard cleaning.

[0032] S2 etched the metasurface structure 4 using photolithography and ICP etching techniques;

[0033] S3 grows a silicon dioxide passivation layer on the device surface through thermal oxidation, so that its sidewalls also have a passivation layer;

[0034] S4 uses photolithography with BOE solution to etch away the silicon dioxide at the interdigitated electrode position, transfers graphene material to form graphene transparent electrode 5, surrounds the metasurface structure 4, that is, all the metasurface structures 4 are in the gaps between the graphene transparent electrode 5, making the electric field distribution more uniform.

[0035] S5 uses electron beam evaporation of Al metal film on metasurface structure 4, followed by thermal annealing to form Al nanostructure 6, in order to induce plasmon enhancement.

[0036] Example 1

[0037] A plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface, the structure of which is as follows: Figure 1-2As shown, the system includes a 4H-SiC substrate 1, an N-type buffer layer 2 on the 4H-SiC substrate 1, a lightly doped N-epitaxial layer 3 on the N-type buffer layer 2, a metasurface structure 4 and a graphene transparent electrode 5 on the lightly doped N-epitaxial layer 3, the graphene transparent electrode 5 being an interdigitated electrode, the metasurface structure 4 being located in the gaps between the graphene transparent electrode 5, and an Al nanostructure 6 on top of the metasurface structure 4 to improve the photosensitive area and the transmittance of ultraviolet light. The metasurface structure 4 is a tilted mesa grating structure, and the Al nanostructure 6 is spherical.

[0038] Example 2

[0039] A method for fabricating a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface includes the following steps:

[0040] S1 in highly doped N + On a 4H-SiC substrate 1, an N-type buffer layer 2 and an N-type buffer layer 3 are sequentially grown using chemical vapor deposition (CVD) for homogeneous epitaxy. - Epitaxial layer 3. The doping concentration of the N-type buffer layer can be 1×10⁻⁶. 18 cm -3 - 2×10 20 cm -3 The thickness can be 0.5μm-2μm; N - The doping concentration of the epitaxial layer can be 1×10 15 cm -3 - 1×10 17 cm -3 The thickness can be 2μm-20μm, and then the epitaxial wafer is cleaned according to RCA standard.

[0041] S2 uses silicon dioxide and AZ5421E photoresist as a barrier layer. The tilted mesa of the grating can be etched using photolithography and etching technology. The mesa width is 50nm-500nm, and the spacing between the grating mesa is 100nm-1000nm to ensure the absorption efficiency of ultraviolet light.

[0042] S4 grows a silicon dioxide passivation layer on the device surface using a thermal oxidation method, and the thickness of the silicon dioxide can be 10nm-100nm.

[0043] S5 uses photolithography with BOE solution to etch away the silicon dioxide at the interdigital electrode positions and transfer graphene material to form the interdigital electrode.

[0044] S6 uses electron beam evaporation of Al metal films with a thickness of 5nm-50nm, followed by thermal annealing to form spherical Al nanostructures.

[0045] The specific steps for the above-mentioned RCA standard cleaning are as follows:

[0046] S1 is sonicated with toluene, acetone and ethanol for 3-5 minutes, repeated 3 times, and then rinsed with deionized water.

[0047] S2 is boiled in solution No. 3 at 250℃ for 15-20 minutes, and then rinsed with hot and cold deionized water; the volume ratio of solution No. 3 is H2SO4∶H2O2=4∶1;

[0048] S3 Immerse the sample in diluted hydrofluoric acid for 3-5 minutes, then rinse with hot and cold deionized water; the diluted hydrofluoric acid is prepared in a volume ratio of HF:H2O = 1:20.

[0049] S4 is boiled in solution No. 1 for 5-10 minutes, then rinsed with hot and cold deionized water; the solution No. 1 is prepared in a volume ratio of NH3·H2O∶H2O2∶H2O=1∶1∶4;

[0050] S5 Immerse the sample in diluted hydrofluoric acid for 3-5 minutes, then rinse with hot and cold deionized water;

[0051] S6 is boiled in solution No. 2 for 5-10 minutes, then rinsed with hot and cold deionized water, and then dried with nitrogen gas for later use; the volume ratio of solution No. 2 is HCl∶H2O2∶H2O=1∶1∶4.

[0052] The specific steps of the above-mentioned inclined mesa etching are as follows: using photoresist reflow technology, coating, pre-baking, exposure with the first mask, development, and rinsing to form the mesa pattern, then post-baking to collapse the photoresist, and finally forming the mesa structure through ICP etching.

[0053] The specific steps for growing the passivation layer are as follows: After etching the grating, the passivation layer is grown. Silicon dioxide is also present on the sidewalls of the grating mesa, which can reduce dark current. First, a layer of silicon dioxide is grown as a sacrificial layer using alternating dry and wet oxidation. The sample after the first oxidation is removed and etched in a buffered hydrofluoric acid solution to remove the oxide layer formed in the first oxidation. The sample is then rinsed with deionized water. The wafer is placed in an oxidation furnace, and another layer of dense silicon dioxide, approximately 10-100 nm thick, is grown again using alternating dry, wet, and dry oxidation.

[0054] The specific steps for fabricating graphene interdigitated electrodes are as follows: the interdigitated electrode area is photolithographically patterned using a second mask, and the oxide layer at the electrode image is etched away using a buffered hydrofluoric acid solution to prepare for the transfer of graphene material as the interdigitated electrode. After the graphene is transferred to the surface, the photoresist and graphene on the mesa and sidewalls are removed using an acetone solution.

[0055] Pad fabrication: The pad area is formed by photolithography using a third mask, and then Ti / Au metal is sputtered by magnetron sputtering as the pad for the device.

[0056] The specific steps for fabricating Al nanostructures on the mesa are as follows: the first mask is used for exposure, development, and washing to form the pattern of the Al film. Photoresist is used as a barrier layer in areas where metal should not be deposited. Electron beam evaporation is used to deposit a 5nm-50nm metal Al film. Acetone is used to remove the metal in areas other than the mesa. Finally, thermal annealing is used to form an ordered spherical Al nanoparticle structure.

[0057] In summary, by utilizing the technical solution described above, the dimensions of the metasurface structure, the size and spacing of the Al nanostructures are rationally calculated to ensure maximum absorption of ultraviolet light when incident on the device surface. When ultraviolet light is incident on the detector surface, on the one hand, graphene is a transparent and excellent conductor, and the metasurface sidewalls also have passivation layers, increasing the photosensitive area of ​​the device and reducing light reflection; on the other hand, free electrons in the Al metal on the metasurface generate collective oscillations under the action of incident light. When the frequency of the collective electron oscillations is comparable to the frequency of the incident light, localized surface plasmon resonance is generated. The enhanced light absorption by the metasurface, graphene electrodes, and plasmon resonance increases the number of photogenerated electron-hole pairs, thereby improving the detector's responsivity and quantum efficiency, and enhancing the application performance of the ultraviolet photodetector.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface, characterized in that, The material includes a 4H-SiC substrate (1), an N-type buffer layer (2) on the 4H-SiC substrate (1), a lightly doped N-epitaxial layer (3) on the N-type buffer layer (2), a metasurface structure (4) and a graphene transparent electrode (5) on the lightly doped N-epitaxial layer (3), the graphene transparent electrode (5) being an interdigitated electrode, the metasurface structure (4) being located in the gap of the graphene transparent electrode (5), an Al nanostructure (6) being provided on the top of the metasurface structure (4), the metasurface structure (4) being a grating structure with a tilted mesa, and the sidewall of the tilted mesa having a silicon dioxide passivation layer.

2. The plasmon-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface according to claim 1, characterized in that, The mesa width of the grating structure is 50nm-500nm, and the spacing between the grating structures is 100nm-1000nm.

3. The plasmon-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface according to claim 1, characterized in that, The Al nanostructure (6) is disc-shaped, triangular prism-shaped, or spherical.

4. The plasmon-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface according to claim 1, characterized in that, The metasurface structure (4) and Al nanostructure (6) are located in the gap between the graphene transparent electrode (5).

5. A method for fabricating a plasmonic-enhanced 4H-SiC MSM ultraviolet photodetector with a metasurface as described in claim 1, characterized in that, Includes the following steps: S1 An N-type buffer layer (2) and an N-epitaxial layer (3) are grown on a 4H-SiC substrate (1) by chemical vapor deposition, and then RCA standard cleaning is performed. S2 etched a metasurface structure using photolithography and ICP etching techniques (4); S3 grows a silicon dioxide passivation layer on the device surface using a thermal oxidation method; S4 The silicon dioxide at the interdigitated electrode position is etched away using photolithography, and graphene material is transferred to form a graphene transparent electrode (5). S5 uses electron beam evaporation of Al metal film on metasurface structure (4), followed by thermal annealing process to form Al nanostructure (6).

6. The preparation method according to claim 5, characterized in that, The N-type buffer layer (2) has a doping concentration of 1×10⁻⁶. 18 cm -3 - 2×10 20 cm -3 The thickness is 0.5μm-2μm.

7. The preparation method according to claim 5, characterized in that, The doping concentration of the N-epipolar layer (3) is 1×10⁻⁶. 15 cm -3 - 1×10 17 cm -3 The thickness is 2μm-20μm.

8. The preparation method according to claim 5, characterized in that, The Al metal film has a deposition thickness of 5nm-50nm.

9. The preparation method according to claim 5, characterized in that, The thickness of the silicon dioxide passivation layer is 10-100 nm.

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