Two-dimensional material / silicon heterojunction photoelectric detector with semi-conformal structure and preparation method thereof

Abstract

The invention discloses a two-dimensional material / silicon heterojunction photoelectric detector with a semi-conformal structure and a preparation method of the two-dimensional material / silicon heterojunction photoelectric detector. The heterojunction photoelectric detector comprises pyramid silicon, a silicon dioxide layer, a chromium / gold electrode, a single-layer two-dimensional material and an in-situ growth two-dimensional material. The preparation method comprises the following specific steps of: etching a silicon window on a silicon / silicon dioxide sheet by adopting photoetching and plasma etching technologies; etching the exposed silicon into pyramid-shaped silicon by using an alkali etching method; depositing a top electrode on the silicon dioxide around the pyramid silicon through a photoetching technology and thermal evaporation; transferring the single-layer two-dimensional material film to the pyramid silicon structure by adopting wet transfer to form semi-conformal contact; and finally, growing a large-area two-dimensional material in situ on the single-layer two-dimensional material / silicon with the semi-conformal structure. The photoelectric detector provided by the invention has the advantages of high response rate, wide spectral response, ultra-large linear dynamic range and quick response capability.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic materials and devices, and in particular to a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure and a preparation method thereof. Background Art

[0002] In recent decades, layered two-dimensional materials have attracted significant attention due to their unique electrical and optoelectronic properties. A key advantage of these materials is their surface passivation and the absence of dangling bonds. Therefore, arbitrary heterostructures can be constructed by stacking layer-by-layer 2D materials without worrying about lattice mismatch. This capability has greatly facilitated the exploration of novel optoelectronic devices. However, the atomically thin thickness of layered 2D materials results in extremely weak light absorption, which limits the performance of devices, particularly photodetectors. Furthermore, large-scale fabrication of heterostructures based solely on layered 2D materials remains a significant challenge. Alternatively, van der Waals heterostructures, which span both layered 2D materials and bulk materials, offer a promising avenue for large-scale device fabrication by leveraging the mature processing techniques of bulk materials. Among the various van der Waals heterostructures composed of layered 2D materials and 3D bulk materials, layered 2D material / silicon van der Waals heterostructures have garnered considerable attention due to the mature processing techniques of silicon and the superior optoelectronic performance exhibited by heterostructured devices. However, numerous reports have shown a sublinear relationship between the photocurrent and light intensity of these devices. These nonlinear relationships in heterojunction photodetectors can be attributed to defects in the materials and interfaces. Furthermore, these heterostructure photodetectors exhibit limited photoresponsivity. Typically, Schottky or pn photodiodes lack gain unless avalanche breakdown occurs, limiting the maximum achievable responsivity. Therefore, the fabrication of layered 2D material / silicon van der Waals heterostructure photodetectors with simultaneously high responsivity, large linear dynamic range, and fast response speed remains a significant challenge. Summary of the Invention

[0003] The present invention aims to provide a semi-conformal 2D material / silicon heterojunction photodetector. The key point is the wet transfer of a single layer of 2D material to form a semi-conformal contact interface with the pyramidal silicon. This overcomes the significant challenge of current layered 2D material / silicon heterojunction photodetectors, which currently lack the performance characteristics of high responsivity, large linear dynamic range, and fast response speed. The present invention designs a semi-conformal 2D material / silicon heterojunction photodetector.

[0004] To achieve the above-mentioned purpose, the present invention provides a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure and a preparation method thereof, characterized in that it comprises a pyramid silicon (1), silicon dioxide (2), a chromium-gold electrode (3), a single-layer two-dimensional material (4) and an in-situ grown large-area two-dimensional material (5) arranged from bottom to top; wherein the silicon / silicon dioxide is exposed to the regionalized pyramid silicon (1) by plasma etching and alkaline wet etching, the chromium-gold electrode (3) is deposited on the silicon dioxide layer (2) by thermal evaporation to form a top electrode, the single-layer two-dimensional material (4) is transferred to the pyramid silicon (1) by a wet transfer method to form a semi-conformal interface and an air nanogap, and finally the large-area two-dimensional material (5) is grown in situ.

[0005] In an embodiment of the present invention, the pyramid silicon (1) and silicon dioxide (2) are obtained by plasma etching and alkaline wet etching using a silicon / silicon dioxide wafer composed of an n-type silicon wafer (1-10Ω·cm) and 100-300nm thick silicon dioxide as a substrate.

[0006] In an embodiment of the present invention, the chromium-gold electrode (3) is deposited as an upper electrode on the silicon dioxide (2) surrounding the pyramid silicon structure, with thicknesses of 2-5 nm and 35-50 nm, respectively.

[0007] In an embodiment of the present invention, the single-layer two-dimensional material (4) is obtained by chemical vapor deposition and wet-transferred onto the pyramid silicon (1) to form a semi-conformal interface and an air nanogap. This semi-conformal structure is formed by capillary forces between the wet-transferred single-layer two-dimensional material film and the pyramid silicon.

[0008] In an embodiment of the present invention, the large-area two-dimensional material (5) is grown in situ on a single-layer two-dimensional material / silicon structure.

[0009] The present invention provides a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure and a preparation method thereof, comprising the following steps:

[0010] Step 1: Select an n-type silicon wafer (1-10Ω·cm) with a 100-300nm thermally oxidized silicon dioxide layer as the substrate. Use photolithography to open a square window with a side length of 10-500μm, and use plasma to etch the silicon dioxide layer (2) in the window;

[0011] Step 2: Wet-etch the pyramidal silicon structure (1) using an alkaline method. The alkaline solution includes potassium hydroxide (2.98 g), isopropyl alcohol (20 ml), and deionized water (80 ml). The etching time is about 40 minutes and the etching temperature is about 95°C.

[0012] Step 3: Depositing a top chromium-gold electrode (3) on the silicon dioxide (2) surrounding the pyramid silicon structure using standard semiconductor processes;

[0013] Step 4: a single layer of two-dimensional material (4) is prepared by a chemical vapor deposition process, and a large area single layer of two-dimensional material film (4) is transferred onto the pyramid silicon by a wet transfer method, thereby forming a semi-conformal interface;

[0014] Step 5: In situ growing a large area of ​​two-dimensional material on the constructed single-layer two-dimensional material / silicon heterojunction (5);

[0015] In an embodiment of the present invention, the method for preparing the silicon window in step 1 is as follows:

[0016] Step 1-1: ultrasonically clean the silicon dioxide / silicon substrate in acetone, anhydrous ethanol, and deionized water for 15 minutes, and blow dry with nitrogen;

[0017] Step 1-2: A square window with a side length of 10 to 500 μm is obtained by photolithography. The substrate with the developed etched pattern is placed in the vacuum chamber of the reactive ion etcher. The silicon dioxide in the developed photolithography pattern window is reactively ion etched using carbon tetrafluoride and argon. The carbon tetrafluoride and argon flow rates are controlled by a mass flow meter to a volume ratio of 2:1. The etching power is 100 W and the etching time is about 360 seconds.

[0018] In an embodiment of the present invention, the preparation method of the pyramid silicon in step 2 is as follows:

[0019] Step 2-1: A pyramid silicon structure was prepared by alkaline wet etching; wherein the alkaline solution included potassium hydroxide (2.98 g), isopropyl alcohol (20 ml) and deionized water (80 ml); the etching time was 40 min and the etching temperature was 95° C.;

[0020] Step 2-2: Rinse the pyramid silicon with deionized water several times to ensure that the residual alkaline solution is removed, and blow dry with high-speed nitrogen;

[0021] In an embodiment of the present invention, the preparation method of the top electrode in step 3 is as follows:

[0022] Step 3-1: Obtain the top electrode pattern by photolithography, place the substrate with the developed electrode pattern into the vacuum chamber of the thermal evaporation coating machine, and evacuate the chamber until the pressure reaches 1×10 -6 ~1×10 -5 Pa;

[0023] Step 3-2: sequentially deposit 2nm to 5nm of chromium and 35nm to 50nm of gold;

[0024] Step 3-3: Place the substrate with the electrode deposited thereon into the degumming solution. After the photoresist is removed, rinse it with anhydrous ethanol and deionized water in sequence, and finally blow it dry with nitrogen.

[0025] In an embodiment of the present invention, the wet transfer method of the single-layer two-dimensional material in step 4 is as follows:

[0026] Step 4-1: Spin-coat a polystyrene solution onto the single-layer 2D material film grown on the substrate and bake at 100°C for about 10 minutes;

[0027] Step 4-2: placing the substrate coated with a single-layer polystyrene two-dimensional material into a potassium hydroxide solution to separate the single-layer two-dimensional material film from the substrate;

[0028] Step 4-3: Wash the single-layer two-dimensional material film with polystyrene on one side four times in deionized water, transfer it to the substrate with the deposited electrode, and dry it for 1-2 hours;

[0029] Step 4-4: Place the transferred substrate in a vacuum tank and evacuate for 30 to 60 minutes, then bake at 120°C for about 8 minutes;

[0030] Step 5-5: Soak the treated substrate in a toluene solution for 20 to 30 minutes. After removing the polystyrene on the surface of the single-layer two-dimensional material film, blow it dry directly with nitrogen.

[0031] In the embodiment of the present invention, there is no specific standard for the method of preparing the large-area two-dimensional material in situ grown in step 5. It is only necessary to adopt a suitable method to in situ grow the large-area two-dimensional material;

[0032] The present invention presents a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure, exhibiting an exceptionally large linear dynamic range and responsivity, attributed to its unique semi-conformal interface structure. The contact region functions as a conventional Schottky photodiode, while the air gap functions as a vacuum diode. This air gap provides an additional transmission channel for electrons, generating photoconductive gain. Furthermore, the device exhibits an ultrafast response speed. Our research provides a new approach to improving the performance of two-dimensional material / silicon heterostructure photodetectors.

[0033] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure.

[0035] Figure 2SEM image of single-layer two-dimensional material / pyramid silicon.

[0036] Figure 3 SEM images of in situ grown large-area two-dimensional materials / single-layer two-dimensional materials / pyramid silicon.

[0037] Figure 4 Current-voltage curves of the device in the dark and under 520 nm light illumination.

[0038] Figure 5 The current curve of the device under 520nm light as the light intensity changes.

[0039] Figure 6 Photoresponsivity spectra of the device at -5V and 0V bias (left); photoresponse curve of the device under 1550nm light (right).

[0040] Figure 7 The IQE / EQE curve of the device under -5V bias changes with the illumination band.

[0041] Figure 8 Under 520nm light, the relative balance of the device (I max -I min ) / I max The relationship between the incident light frequency and f 3dB 10kHz (left) and a single amplified transient photoresponse curve of the device (right). DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the embodiments.

[0043] like Figure 1 As shown, in order to achieve the above-mentioned purpose, the present invention provides a two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure and a preparation method thereof, characterized in that it includes a pyramid silicon (1), silicon dioxide (2), a chromium-gold electrode (3), a single layer of tungsten disulfide (4) and platinum ditelluride (5) arranged from bottom to top; wherein the silicon / silicon dioxide is exposed to regionalized pyramid silicon (1) by plasma etching and alkaline wet etching, the chromium-gold electrode (3) is deposited on the silicon dioxide layer (2) by thermal evaporation to form a top electrode, the single layer of tungsten disulfide film (4) is transferred to the pyramid silicon (1) by a wet transfer method to form a semi-conformal interface and an air nanogap, and finally a platinum film is radio frequency sputtered and tellurized to form a platinum ditelluride film (5). The specific steps are as follows:

[0044] 1. A silicon window (2) is obtained by photolithography and plasma etching; a silicon dioxide / silicon substrate (1) is sequentially placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 5 minutes, and then blown dry with nitrogen; an arrayed photoresist window is obtained by photolithography; the substrate with the developed photoresist pattern is placed in a vacuum chamber of a reactive ion etcher, and the silicon dioxide in the developed photoresist pattern window is subjected to reactive ion etching using carbon tetrafluoride and argon to expose the regionalized underlying silicon; the flow rate of carbon tetrafluoride and argon is controlled by a mass flow meter to a volume ratio of 2:1, the etching power is 100W, and the etching time is about 360s; the substrate is taken out and immersed in acetone, and after the photoresist is removed, silicon dioxide (2) with an opening is obtained, which is sequentially rinsed with anhydrous ethanol and deionized water, and finally blown dry with nitrogen.

[0045] 2. Pyramid silicon (1) is obtained by alkaline wet etching; an alkaline solution etching solution is prepared: wherein the alkaline solution includes potassium hydroxide (2.98g), isopropyl alcohol (20ml) and deionized water (80ml); the etching solution is heated to 95°C in a water bath, and the exposed silicon area is etched for 40 minutes to obtain regionalized pyramid silicon (1); the pyramid silicon is washed with deionized water multiple times to ensure that the residual alkaline solution is removed, and then blown dry with high-speed nitrogen gas;

[0046] 3. Photolithography and evaporation of the top electrode (3) The top electrode pattern is obtained by photolithography, and the substrate with the electrode pattern is placed in the vacuum chamber of the thermal evaporation coating machine, and the chamber is evacuated to a pressure of 1×10 -5 Pa; first evaporate into the degumming solution at a rate of 0.02nm / s, and after the photoresist is removed, rinse with anhydrous ethanol and deionized water in sequence, and finally blow dry with nitrogen.

[0047] 4. Transfer a single-layer tungsten disulfide film (4) by wet transfer, spin-coat a polystyrene solution on the surface, and bake it at 100°C for 10 minutes; place the tungsten disulfide substrate coated with polystyrene in a 20% concentration of sodium hydroxide solution to separate the single-layer tungsten disulfide film (4) from the sapphire substrate; wash the single-layer tungsten disulfide film (4) with polystyrene on one side in deionized water four times, deposit it on the substrate with the electrode, and dry it for 2 hours; place the transferred substrate in a vacuum tank and evacuate it for 30 minutes, and bake it at 120°C for 8 minutes; soak the treated substrate in a toluene solution for 20 minutes, and after removing the polystyrene on the surface of the single-layer tungsten disulfide film (4), blow it dry directly with nitrogen.

[0048] 5. Prepare platinum ditelluride thin film (5) by radio frequency magnetron sputtering and plasma enhanced chemical vapor deposition; Place the constructed tungsten disulfide / pyramid silicon heterojunction substrate with a semi-conformal structure into the magnetron sputtering chamber and evacuate to 1×10 -5Pa; adjust the argon flow rate to 90 sccm, the sputtering pressure to 3.5 Pa, the RF sputtering power and time to 15 W and 100 s respectively; place the substrate with the platinum film in the downstream of the tube furnace, and place the tellurium powder with a concentration of 99.99% in the upstream of the tube furnace; pump the pressure in the tube furnace to 2 Pa and then inject argon to atmospheric pressure, and cycle three times to ensure that the contaminated gas residue in the tube furnace is minimal; finally, maintain the argon carrier gas flow rate to 4 sccm and the tube pressure to 10 Pa; the middle furnace temperature is 290 ° C; use a RF coil with a power of 400 W to induce argon plasma in the tube to perform tellurization to form a top layer of platinum ditelluride film (5);

[0049] The above describes in detail the specific embodiments of the present invention. It should be understood that numerous modifications and variations based on the concepts of the present invention can be made by those skilled in the art without inventive effort. Therefore, any technical solution that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the existing technology should be within the scope of protection defined by the claims.

Claims

1. A two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure and a method for preparing the same, characterized in that: The invention comprises a pyramid silicon (1), silicon dioxide (2), a chromium-gold electrode (3), a single-layer two-dimensional material (4), and an in-situ grown large-area two-dimensional material (5) arranged from bottom to top; wherein the silicon / silicon dioxide is exposed to the regionalized pyramid silicon (1) by plasma etching and alkaline wet etching, the chromium-gold electrode (3) is deposited on the silicon dioxide layer (2) by thermal evaporation to form a top electrode, the single-layer two-dimensional material (4) is transferred to the pyramid silicon (1) by a wet transfer method to form a semi-conformal interface and an air nano-gap, and finally the large-area two-dimensional material (5) is grown.

2. The two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure according to claim 1, wherein: The pyramid silicon (1) and silicon dioxide (2) are obtained by using a silicon / silicon dioxide wafer composed of an n-type silicon wafer (1-10Ω·cm) and 100-300nm thick silicon dioxide as a substrate through photolithography, plasma etching and alkaline wet etching.

3. The two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure according to claim 1, wherein: The chromium-gold electrode (3) is deposited as an upper electrode on the silicon dioxide (2) surrounding the pyramid silicon structure, with thicknesses of 2-5 nm and 35-50 nm respectively.

4. The two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure according to claim 1, wherein: The single-layer two-dimensional material (4) is wet-transferred onto the pyramid silicon (1) to form a semi-conformal interface.

5. The two-dimensional material / silicon heterojunction photodetector with a semi-conformal structure according to claim 1, wherein: The large-area two-dimensional material (5) is a two-dimensional material that is directly grown in situ on a single-layer two-dimensional material / pyramid silicon heterostructure.

6. The method for preparing a two-dimensional material / silicon heterojunction photodetector having a semi-conformal structure according to claims 1 to 5, characterized in that: The steps include: Step 1: Select an n-type silicon wafer (1-10Ω·cm) with a 100-300nm thermally oxidized silicon dioxide layer as the substrate. Using photolithography, open a square window with a side length of 10-500μm and use plasma to etch the silicon dioxide layer (2) in the window. Step 2: Wet-etch the pyramidal silicon structure (1) using an alkaline method. The alkaline solution includes potassium hydroxide (2.98 g), isopropyl alcohol (20 ml), and deionized water (80 ml). The etching time is about 40 minutes and the etching temperature is about 95°C. Step 3: Depositing a top chromium-gold electrode (3) on the silicon dioxide (2) surrounding the pyramid silicon structure using standard semiconductor processes; Step 4: a single layer of two-dimensional material (4) is prepared by a chemical vapor deposition process, and a large area single layer of two-dimensional material film (4) is transferred to the pyramid silicon by a wet transfer method to form a semi-conformal interface; Step 5: In situ growth of large-area two-dimensional materials on the constructed single-layer two-dimensional material / silicon heterojunction (5).

Images