Large-current organic field-effect transistor based on tunneling effect and preparation method thereof

Abstract

The present invention relates to a high-current organic field-effect transistor based on the tunneling effect, which includes a gate electrode, an insulating layer is provided on the gate electrode, an active layer is provided on the insulating layer, and a source electrode and a drain electrode are respectively provided on the active layer; it is characterized in that a first modification layer is provided between the source electrode and the active layer, and the first modification layer is used to form a tunneling effect between the source electrode and the active layer; a second modification layer is provided between the drain electrode and the active layer, and the second modification layer is used to form a tunneling effect between the drain electrode and the active layer. Based on the tunneling effect of quantum mechanics, in this embodiment, by adding a modification layer between the active layer and the source electrode and the drain electrode, a tunneling effect is generated between the active layer and the source electrode and the drain electrode, thereby increasing the output current of the organic field-effect transistor and greatly improving the driving ability of the organic field-effect transistor.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic field-effect transistors, and relates to a high-current organic field-effect transistor based on tunneling effect and a preparation method thereof. Background Art

[0002] An organic field-effect transistor (OFET) is a field-effect transistor that uses an organic semiconductor to form a channel. Currently, in the manufacturing process of OFETs, the most widely used p-type organic semiconductor materials often need to be matched with high-work-function metals such as gold (Au) and platinum (Pt) as electrodes to reduce the contact resistance and thus obtain a larger output current.

[0003] In the prior art, CN107845728A provides an OFET tube with a large output current and a preparation method thereof, and discloses that the structure of the OFET includes a gate electrode, an insulating layer, an active layer, a source electrode and a drain electrode. The active layer includes copper phthalocyanine, and at least two layers of molybdenum oxide are sandwiched in the copper phthalocyanine. It also discloses that the preparation method of the OFET includes the following steps: 1. Pretreatment of the ITO substrate; 2. Spin-coating the insulating layer on the substrate; 3. Evaporating a multi-layer composite active layer; 4. Preparation of the source and drain electrodes. The output current of the OFET prepared by the above technical solution is significantly increased, and the driving ability of the OFET tube is improved. However, according to the description in its specification, the test result of the OFET is that when the drain voltage is 50V, its maximum saturation current is -2.92 μA, which cannot meet the application scenarios with greater current requirements. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high-current organic field-effect transistor based on tunneling effect and a preparation method thereof.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A high-current organic field-effect transistor based on tunneling effect includes a gate electrode, an insulating layer is disposed on the gate electrode, an active layer is disposed on the insulating layer, and a source electrode and a drain electrode are respectively disposed on the active layer; a first modification layer is disposed between the source electrode and the active layer, and the first modification layer is used to form a tunneling effect between the source electrode and the active layer; a second modification layer is disposed between the drain electrode and the active layer, and the second modification layer is used to form a tunneling effect between the drain electrode and the active layer.

[0007] Further, the material of the active layer is a hexathiophene thin film, and the materials of the first modification layer and the second modification layer are both DNTPD thin films.

[0008] Further, the materials of the source and the drain are both metals with a work function between -4.6 eV and -4.5 eV.

[0009] Further, the materials of the source and the drain are both copper.

[0010] Further, the thicknesses of the first modification layer and the second modification layer are 1 nm to 2 nm.

[0011] Further, the material of the gate is silicon, and the material of the insulating layer is silicon dioxide.

[0012] A method for fabricating a high-current organic field-effect transistor based on the tunneling effect, comprising the following steps:

[0013] S1. Take a substrate, the substrate having a semiconductor material layer and an insulating layer;

[0014] S2. Clean the substrate, and then dry it by heating;

[0015] S3. Deposit an active layer on the insulating layer of the substrate;

[0016] S4. Deposit two modification layers on the active layer respectively;

[0017] S5. Deposit metal layers on the two modification layers respectively.

[0018] Further, the material of the active layer is a hexathiophene thin film; the material of the modification layer is a DNTPD thin film; the materials of the metal layers are both metals with a work function between -4.6 eV and -4.5 eV.

[0019] Further, the thickness of the substrate is 250 nm to 350 nm, the thickness of the hexathiophene thin film is 20 nm to 30 nm, and the thickness of the metal layer is 120 nm to 180 nm.

[0020] Further, in the step S2, the substrate is cleaned by an ultrasonic cleaning method; in the steps S3, S4, and S5, the deposition method is vacuum evaporation.

[0021] In the present invention, the tunneling effect of quantum mechanics is applied in the structure of the organic field-effect transistor, and a modification layer is added between the active layer and the source and the drain. The tunneling effect is generated between the active layer and the source and the drain through the modification layer, thereby increasing the output current of the organic field-effect transistor, and the driving ability is greatly improved. The improvement amplitude is up to 33% compared with the prior art. In addition, by selecting the material of the active layer, copper can be used as the material of the source and the drain, thereby greatly reducing the production cost. Description of the Drawings

[0022] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail and preferably with reference to the accompanying drawings, where:

[0023] Figure 1 It is a schematic structural diagram of a preferred embodiment of the high-current organic field-effect transistor based on the tunneling effect of the present invention.

[0024] Figure 2 It is a flowchart of a preferred embodiment of the preparation method of the high-current organic field-effect transistor based on the tunneling effect of the present invention.

[0025] Figure 3 It is an output characteristic curve diagram of the leakage current when the thickness of the DNTPD film is 2 nm.

[0026] Figure 4 It is a flowchart of a preferred embodiment of the preparation method of the high-current organic field-effect transistor based on the tunneling effect of the present invention.

[0027] Figure 5 It is a flowchart of ultrasonic cleaning of the substrate.

[0028] Figure 6 It is a flowchart of the vacuum evaporation process in steps S3, S4 and S5.

[0029] In the figure: 1. Gate, 2. Insulating layer, 3. Active layer, 4. First modification layer, 5. Second modification layer, 6. Source electrode, 7. Drain electrode. Detailed implementation manners

[0030] The following illustrates the implementation manners of the present invention through specific specific examples. The diagrams provided in the following examples only illustrate the basic concept of the present invention schematically. Without conflict, the following examples and the features in the examples can be combined with each other.

[0031] The present invention discloses a high-current organic field-effect transistor based on the tunneling effect, such as Figure 1As shown in the figure, a preferred embodiment of the high-current organic field-effect transistor based on the tunneling effect of the present invention includes a gate 1, and the gate 1 is made of a semiconductor material, such as: silicon (Si), germanium (Ge), preferably a heavily doped n-type silicon wafer; an insulating layer 2 is provided on the gate 1, and the insulating layer 2 is made of an insulating material, such as: a compound of silicon and germanium, preferably silicon dioxide (SiO2); for example: the Si layer of the Si / SiO2 substrate can be used as the gate 1, and the SiO2 layer can be used as the insulating layer 2. An active layer 3 is provided on the insulating layer 2, and the material of the active layer 3 is preferably an α-sexithiophene (α-6T) thin film; a first modification layer 4 and a second modification layer 5 are respectively provided on the active layer 3, the first modification layer 4 and the second modification layer 5 are preferably symmetrically arranged, and the materials of the first modification layer 4 and the second modification layer 5 are preferably DNTPD thin films, and DNTPD is the abbreviation of 4′-bis(N-{4-[N-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl. The thickness of the first modification layer 4 and the second modification layer 5 is 1 nm to 2 nm, preferably 2 nm.

[0032] As Figure 2 As shown in the figure, a channel is formed between the first modification layer 4 and the second modification layer 5, the channel width (W) of the channel is 2 mm to 10 mm, preferably 5 mm, and the channel length (L) is 20 μm to 100 μm, preferably 50 μm. A source electrode 6 is provided on the first modification layer 4, and a drain electrode 7 is provided on the second modification layer 5; the first modification layer 4 is used to form a tunneling effect between the source electrode 6 and the active layer 3, and the second modification layer 5 is used to form a tunneling effect between the drain electrode 7 and the active layer 3. The materials of the source electrode 6 and the drain electrode 7 are both metals with a work function between -4.6 eV and -4.5 eV, preferably copper (Cu), and the thickness of the source electrode 6 and the drain electrode 7 is 120 nm to 180 nm, preferably 150 nm. The reasons for the material selection of the active layer 3 and the source electrode 6 and the drain electrode 7 are as follows: sexithiophene is a commonly used p-type organic semiconductor material, and its HOMO energy level is -4.5 eV; the work function of copper is -4.6 eV. Using copper as the material of the source electrode 6 and the drain electrode 7, there is only a difference of 0.1 eV between the active layer 3 and the source electrode 6 and the drain electrode 7, and the compatibility is relatively high. Moreover, compared with precious metals such as gold, using copper as the electrode material of the source electrode 6 and the drain electrode 7 can greatly reduce the cost and is suitable for large-scale commercial use. However, it is found in actual applications that there is still a large contact resistance at the interface between the active layer 3 and the copper electrode; to reduce the contact resistance, a layer of DNTPD thin film is added between the active layer 3 and the source electrode 6 and the drain electrode 7 in this embodiment, and the sexithiophene of the active layer 3 is modified by using DNTPD as a hole injection material.

[0033] To verify the effects of different thicknesses of the modification layer (hereinafter, the first modification layer 4 and the second modification layer 5 are collectively referred to as the modification layer), in the specific implementation, organic field-effect transistors with modification layer DNTPD thicknesses of 0 nm, 2 nm, 5 nm, 10 nm, and 30 nm were prepared respectively, and their performances were detected respectively. The comparison of the detection results is shown in the following table:

[0034]

[0035]

[0036] From the data in the above table, it can be seen that when using DNTPD thin films with different thicknesses as the modification layer, the maximum drain currents of the 5-nm structure and the 10-nm structure are both between -1 μA and -2 μA, and the maximum drain current of the 30-nm structure is close to the level of the prior art. However, when the thickness of the DNTPD thin film is 2 nm, an obvious phenomenon of increased drain current occurs. The output characteristic curve is as Figure 3 shown. When the drain voltage is 50 V, the maximum drain current is -3.77 μA, which is 33% higher than -2.92 μA in the prior art. Analyzing the reason, it is because under the modification of the 2-nm-thick DNTPD thin film, a tunneling effect is induced at the interface between α-6T and Cu, improving the carrier injection efficiency and making the effect of increasing the output current more obvious.

[0037] The tunneling effect is a concept proposed by quantum mechanics, referring to the quantum behavior that although microscopic particles such as electrons do not have the energy required to cross the potential barrier, they can penetrate or cross the potential barrier. Quantum mechanics believes that when a large number of particles rush towards the potential barrier, even if the particle energy is less than the threshold energy, some particles can still pass through, as if there is a tunnel in the potential barrier.

[0038] Based on the tunneling effect of quantum mechanics, in this embodiment, a modification layer is added between the active layer 3 and the source electrode 6 and the drain electrode 7. Through the modification layer, a tunneling effect is generated between the active layer 3 and the source electrode 6 and the drain electrode 7, thereby obtaining an organic field-effect transistor with a significantly larger output current, greatly improving the driving ability of the organic field-effect transistor, with a 33% increase compared to the prior art. In addition, by selecting the material of the active layer 3, copper can be used as the material of the source electrode 6 and the drain electrode 7, thereby greatly reducing the production and manufacturing cost.

[0039] The present invention also discloses a preparation method of a high-current organic field-effect transistor based on the tunneling effect. As Figure 4 shown, a preferred embodiment of the preparation method of the high-current organic field-effect transistor based on the tunneling effect of the present invention includes the following steps:

[0040] S1. Take a substrate, which has a semiconductor material layer and an insulating layer 2, and the thickness of the substrate is 250 nm to 350 nm. The semiconductor material layer serves as the gate 1 of the organic field-effect transistor and is made of semiconductor materials such as silicon (Si) and germanium (Ge), preferably a heavily doped n-type silicon wafer; the insulating layer 2 is made of insulating materials such as compounds of silicon and germanium, preferably silicon dioxide (SiO2); for example, the substrate can be a Si / SiO2 substrate with a thickness of 300 nm, and the Si layer of the Si / SiO2 substrate is used as the gate 1, and the SiO2 layer is used as the insulating layer 2.

[0041] S2. Clean the substrate, and then dry it by heating. Preferably, the ultrasonic cleaning method is used to clean the substrate, as Figure 5 shown, this step can specifically include the following steps:

[0042] S201. Place the substrate into a tetrafluoro cleaning rack to make the orientation of the polished surface uniform.

[0043] S202. Rinse the substrate with tap water to remove the debris and particles brought by cutting on the surface of the substrate.

[0044] S203. Wipe the substrate with a dust-free cloth dipped in a detergent.

[0045] S204. Place the entire tetrafluoro cleaning rack into a beaker, pour in deionized water to submerge the substrate, and clean for 20 minutes. Then replace the deionized water and clean again for 20 minutes.

[0046] S205. Pour out the deionized water, pour in anhydrous ethanol, seal the beaker mouth with tin foil, and clean for 30 minutes.

[0047] S206. Pour the anhydrous ethanol into an ethanol recovery bucket, pour in acetone, seal and clean for 30 minutes, and set the temperature to 30 - 40 degrees.

[0048] S207. Pour the acetone into an organic waste liquid bucket, pour in isopropanol, seal and clean for 20 minutes.

[0049] S208. Use clean tweezers to pick out the substrate from the isopropanol solution piece by piece, dry it with nitrogen, and place it into a clean petri dish.

[0050] S209. Place the cleaned substrate on a constant-temperature heating table, dry it at 120 °C for 1 hour, and then it can be used.

[0051] S3. Deposit an active layer 3 on the insulating layer 2 of the substrate. In this embodiment, preferably, the vacuum evaporation process is used to deposit a 25-nm-thick hexathiophene film on the SiO2 insulating layer 2 of the substrate at a fixed rate. As Figure 6As shown, the vacuum evaporation process of this step may specifically include the following steps:

[0052] S301. After loading the substrate into the bracket of the vacuum evaporation machine and embedding it in the carrier table, close the substrate baffle of the vacuum evaporation machine.

[0053] S302. Add an appropriate amount of evaporation material (i.e., hexathiophene) into the evaporation boat of the vacuum evaporation machine, and close the evaporation boat baffle through the console.

[0054] S303. Close the hatch of the vacuum evaporation machine, fasten it, and then open the mechanical pump and the angular valve.

[0055] S304. After the air pressure is lower than 7 Pa, close the angular valve, open the solenoid valve, and then open the gate valve.

[0056] S305. Start the molecular pump of the vacuum evaporation machine and wait for the molecular pump to reach the maximum rotation speed and operate stably.

[0057] S306. After the air pressure reaches 6×10 -4 Pa, turn on the thin film monitor and set it to the current evaporation material (i.e., hexathiophene).

[0058] S307. Rotate the carrier table of the vacuum evaporation machine at a low speed.

[0059] S308. Turn on the evaporation source, open the evaporation boat baffle, slowly increase the current to the vaporization temperature of the current material, and fine-tune the current after observing the change in the crystal oscillator frequency until the evaporation rate meets the experimental requirements.

[0060] S309. Open the substrate baffle, and at the same time press the zero button of the thin film monitor to start evaporation.

[0061] S310. After the evaporated coating (i.e., hexathiophene film) reaches the target thickness, sequentially close the substrate baffle, evaporation source, evaporation boat baffle, gate valve, and molecular pump. After the molecular pump stops rotating, close the solenoid valve and mechanical pump.

[0062] S311. After the substrate cools down, open the intake valve to increase the pressure, open the hatch, and complete the evaporated coating of the vacuum evaporation.

[0063] S4. Deposit two modification layers, namely the first modification layer 4 and the second modification layer 5, on the active layer 3 respectively. Preferably, the vacuum evaporation process is adopted to deposit DNTPD on the hexathiophene film at a fixed rate as the modification layer. The thickness of the DNTPD film is preferably 2 nm. The vacuum evaporation process adopted in this step is basically the same as the steps of the vacuum evaporation process in step S2 of this embodiment, and will not be elaborated here.

[0064] S5. Deposit metal layers on the two modification layers respectively. The two metal layers serve as the source electrode 6 and the drain electrode 7 of the organic field-effect transistor respectively. The materials of the metal layers are all metals with a work function between -4.6 eV and -4.5 eV, preferably copper, and the thickness of the metal layer is preferably 150 nm. When depositing the metal layer, vacuum evaporation process is preferably adopted.

[0065] The technical solution of this embodiment applies the tunneling effect of quantum mechanics in the preparation process of the organic field-effect transistor, increases the output current of the field-effect transistor, and improves the driving ability; and copper can be used to make the electrodes, which greatly reduces the production and manufacturing costs.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A high-current organic field-effect transistor based on the tunneling effect, comprising a gate, an insulating layer is provided on the gate, an active layer is provided on the insulating layer, and a source electrode and a drain electrode are respectively provided on the active layer; characterized in that, A first modification layer is provided between the source electrode and the active layer, and the first modification layer is used to form a tunneling effect between the source electrode and the active layer; A second modification layer is provided between the drain electrode and the active layer, and the second modification layer is used to form a tunneling effect between the drain electrode and the active layer; The material of the active layer is a hexathiophene thin film, and the materials of the first modification layer and the second modification layer are both DNTPD thin films.

2. The high-current organic field-effect transistor based on the tunneling effect according to claim 1, wherein The materials of the source electrode and the drain electrode are both metals with a work function between -4.6 eV and -4.5 eV.

3. The large current organic field effect transistor based on tunneling effect according to claim 2, wherein The materials of the source electrode and the drain electrode are both copper.

4. The large-current organic field-effect transistor based on the tunneling effect according to claim 1, characterized in that, The thicknesses of the first modification layer and the second modification layer are 1 nm to 2 nm.

5. The high-current organic field-effect transistor based on the tunneling effect according to any one of claims 1 to 4, characterized in that The material of the gate electrode is silicon, and the material of the insulating layer is silicon dioxide.

6. A method for fabricating a high-current organic field-effect transistor based on the tunneling effect, characterized in that It includes the following steps: S1. Take a substrate, and the substrate has a semiconductor material layer and an insulating layer; S2. Clean the substrate and then dry it by heating; S3. Deposit an active layer on the insulating layer of the substrate; the material of the active layer is a hexathiophene thin film; S4. Deposit two modification layers on the active layer respectively; the material of the modification layer is a DNTPD thin film; S5. Deposit metal layers on the two modification layers respectively.

7. The method for preparing a high-current organic field-effect transistor based on the tunneling effect according to claim 6, wherein The materials of the metal layers are both metals with a work function between -4.6 eV and -4.5 eV.

8. The method for preparing a high-current organic field-effect transistor based on the tunneling effect according to claim 7, wherein, The thickness of the substrate is 250 nm to 350 nm, the thickness of the hexathiophene thin film is 20 nm to 30 nm, and the thickness of the metal layer is 120 nm to 180 nm.

9. The method for preparing a high-current organic field-effect transistor based on the tunneling effect according to claim 6, wherein, In the step S2, the substrate is cleaned by ultrasonic cleaning; in the steps S3, S4, and S5, the deposition method is vacuum evaporation.

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