WS2 (Er / Yb) / Si Van der Waals heterojunction optical detector

Abstract

The invention belongs to the field of manufacturing of optoelectronic devices, and relates to a WS2 (Er / Yb) / Si Van der Waals heterojunction photodetector, which comprises the following steps of: growing a WS2 (Er / Yb) / Si heterojunction layer doped with a rare earth material on an SOI (Silicon On Insulator) substrate through CVD (Chemical Vapor Deposition), and photoetching the WS2 (Er / Yb) / Si heterojunction layer according to a designed electrode pattern; carrying out magnetron sputtering on the WS2 (Er / Yb) / Si heterojunction layer after photoetching so as to grow a metal electrode on the WS2 (Er / Yb) / Si heterojunction layer; and removing the photoresist to obtain the WS2 (Er / Yb) / Si heterojunction optical detector. On the basis of a CVD method, reactants containing rare earth elements are added into reaction raw materials, so that substitution doping is realized, and the defect density is reduced; according to the method, the WS2 (Er / Yb) / Si heterojunction is constructed by adopting a direct growth method, so that the pollution problems of residual glue, impurities and the like in a transfer method are avoided.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic device manufacturing, and relates to a WS 2 (Er / Yb) / Si van der Waals heterojunction photodetector. Background Art

[0002] In recent years, transition metal dichalcogenides (TMDs) in two-dimensional materials have attracted extensive attention in various promising application fields due to their excellent physical and chemical properties and mature large-area preparation technology. Chemical vapor deposition (CVD) is considered the most promising method for preparing high-quality two-dimensional materials. However, according to the second law of thermodynamics, when materials are grown by CVD, defects will occur in two-dimensional materials, which usually leads to a reduction in crystal quality and further affects the performance of two-dimensional material devices. Therefore, reducing the defect density is crucial.

[0003] Constructing van der Waals heterojunctions is the key to improving the performance of TMDs optoelectronic devices. At present, transfer technology is mostly used to prepare van der Waals heterojunctions, but impurities will be introduced during the transfer process, thus affecting the optoelectronic performance of the heterojunctions. Summary of the Invention

[0004] To solve the above problems in the prior art, the present invention adopts a WS 2 (Er / Yb) / Si van der Waals heterojunction photodetector, which is characterized by including the following preparation steps:

[0005] S1. Grow a WS 2 (Er / Yb) / Si heterojunction layer doped with rare earth materials on an SOI substrate by CVD; wherein, CVD is chemical vapor deposition;

[0006] S2. Lithograph the WS 2 (Er / Yb) / Si heterojunction layer according to the designed electrode pattern;

[0007] S3. Magnetron sputter the lithographed WS 2 (Er / Yb) / Si heterojunction layer to grow a metal electrode on the WS 2 (Er / Yb) / Si heterojunction layer;

[0008] S4. Remove the photoresist to obtain a WS 2 (Er / Yb) / Si heterojunction photodetector.

[0009] Advantageous Effects:

[0010] 1. Based on the CVD method, the present invention adds reactants containing rare earth elements to the reaction raw materials, realizes substitution doping, and reduces the defect density; 2. The present invention adopts the direct growth method to construct WS 2(Er / Yb) / Si heterojunction avoids contamination problems such as residual glue and impurities existing in the transfer method; 3. In the present invention, two-dimensional material WS 2 (Er / Yb) is prepared on three-dimensional semiconductor material SOI, so that the bonding quality of the two materials is very high, and the generation process will not damage the two-dimensional material thin film; 4. The present invention only needs to grow one kind of two-dimensional material, and this kind of two-dimensional material directly forms a heterojunction with Si on the upper layer of SOI, improving the preparation efficiency. Description of the Drawings

[0011] Figure 1 The flowchart of a preparation method of a WS 2 (Er / Yb) / Si van der Waals heterojunction photodetector provided by an embodiment of the present invention;

[0012] Figure 2 The schematic diagram of a double-temperature-zone quartz tube furnace provided by an embodiment of the present invention;

[0013] Figure 3 The schematic diagram of the temperature curves of temperature zone Ⅰ and temperature zone Ⅱ provided by an embodiment of the present invention;

[0014] Figure 4 The optical microscope image of the WS 2 (Er / Yb) heterojunction layer provided by an embodiment of the present invention;

[0015] Figure 5 a is the high-resolution XPS spectrum of S2p of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0016] Figure 5 b is the high-resolution XPS spectrum of W4f-5p of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0017] Figure 5 c is the high-resolution XPS spectrum of Er4d of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0018] Figure 5 d is the high-resolution XPS spectrum of Yb4d of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0019] Figure 6a The EDS-SEM image of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0020] Figure 6b The elemental mapping image of WS 2 (Er / Yb) provided by an embodiment of the present invention;

[0021] Figure 7 WS provided in the embodiment of the present invention 2 (Er / Yb) / Si heterojunction photodetector; optical microscope image

[0022] Figure 8 a is the I-V characteristic curve schematic diagram of the WS 2 (Er / Yb) / Si heterojunction photodetector under irradiation with different laser power densities

[0023] Figure 8 b is the I-T curve schematic diagram of the WS 2 (Er / Yb) / Si / Si heterojunction photodetector under a -4V bias voltage and laser irradiation with a power density of 61.95 mW / cm2 Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] As Figure 1 shown, the present invention adopts a WS 2 (Er / Yb) / Si van der Waals heterojunction photodetector, including:

[0026] S1. Growing a WS 2 (Er / Yb) / Si heterojunction layer doped with rare earth materials on an SOI substrate by CVD; where SOI is silicon on insulator, and CVD is chemical vapor deposition;

[0027] Growing a WS 2 (Er / Yb) / Si heterojunction layer doped with rare earth materials on an SOI substrate by CVD includes:

[0028] S11. Cutting and cleaning the SOI substrate, and drying the cleaned SOI substrate with high-purity nitrogen

[0029] The cutting and cleaning of the SOI substrate include: cutting the SOI substrate into a size of 1.2 cm × 2.2 cm and placing it in a beaker; pouring a cleaning agent into the beaker and placing the beaker in an ultrasonic cleaner for cleaning. The replacement order of the cleaning agent in the beaker is deionized water → absolute ethanol → acetone → absolute ethanol → deionized water. It is cleaned 5 times, 10 minutes each time. After cleaning, it is placed in a beaker filled with absolute ethanol for storage.

[0030] S12. Preparation of WS by CVD method 2 (Er / Yb) experiment was carried out in a 2-foot double-temperature zone quartz tube furnace. The schematic diagram of the device is as Figure 2 shown; Weigh 60 mg of S powder (>99.5%) and place it in a corundum boat as a non-metallic precursor, and place the boat in Heating zone Ⅰ of the quartz tube furnace; Weigh 30 mg of WO 3 (purity >99.0%), 3 mg of NaCl (99.99%), 3 mg of ErCl 3 (99.99%) and 3 mg of YbCl 3 (99.99%), mix them evenly and place them in another corundum boat, and place the boat in Heating zone Ⅱ of the quartz tube furnace; Invert the dried SOI substrate on the corundum boat in Heating zone Ⅱ of the quartz tube furnace; Among them, S is sulfur, WO 3 is tungsten trioxide, that is, the metal precursor, NaCl is sodium chloride, that is, the reaction promoter, ErCl 3 is erbium chloride, YbCl 3 is ytterbium chloride, ErCl 3 and YbCl 3 are rare earth dopants;

[0031] S13. Close the quartz tube furnace, pump the air pressure in the quartz tube furnace to vacuum, open the inlet valve of the quartz tube furnace and introduce high-purity Ar gas (argon) at a flow rate of 200 mL / min. When the pressure in the quartz tube furnace reaches the standard atmospheric pressure, open the outlet valve of the quartz tube furnace and adjust the Ar gas flow rate to 60 mL / min;

[0032] S14. Start the quartz tube furnace to heat Heating zone Ⅰ and Heating zone Ⅱ. The curves of the temperature (Temperature) of the two heating zones with respect to time (Time) are as Figure 3 shown. When Heating zone Ⅱ is heated to 150 °C, repeat step S13 to remove the impurity gases and attached dust generated during the heating process;

[0033] S15. 5 minutes before Heating zone Ⅰ and Heating zone Ⅱ are heated to the highest temperature, introduce an Ar / H 2 mixed gas at a flow rate of 60 mL / min; Ar:H2 = 9:1; The highest temperature of Zone I is 200 °C, and that of Zone II is 930 °C; where, H 2 is hydrogen;

[0034] S16. When Zone I and Zone II are heated to the highest temperature, hold at the highest temperature for ten minutes; after ten minutes, introduce Ar gas at a flow rate of 60 mL / min until Zone I and Zone II cool naturally to room temperature, then the sample can be taken out, i.e., WS 2 (Er / Yb) / Si heterojunction layer; The grown WS 2 (Er / Yb) heterojunction layer's optical microscope picture is as Figure 4 shown.

[0035] To confirm the successful doping of rare earth elements, WS 2 (Er / Yb) was respectively detected by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometer (EDS).

[0036] Figure 5 a - d are the X-ray photoelectron spectroscopy (XPS) diagrams of WS 2 (Er / Yb), Figure 5 a is the high-resolution XPS spectrum of S2p. The binding energies of the characteristic peaks at 163.18 eV and 164.38 eV respectively correspond to S2p 3 / 2 and S2p 1 / 2 . Figure 5 b is the high-resolution XPS spectrum of W4f - 5p. The binding energies of the characteristic peaks at 33.58 eV, 35.68 eV and 39.28 eV respectively correspond to W4f 7 / 2 、W4f 5 / 2 and W5p 3 / 2 . Figure 5 c and Figure 5 d are respectively the high-resolution XPS spectra of Er4d and Yb4d. Compared with pure WS 2 , in the spectrum of WS 2 (Er / Yb), two obvious characteristic peaks are added. The binding energies are 174.08 eV and 186.98 eV respectively, corresponding to Er4d and Yb4d. This indicates that Er and Yb are successfully incorporated into WS 2 ; where, Binding energy is the binding energy and Intensity is the intensity.

[0037] As Figure 6a shown, the EDS-SEM (energy-dispersive X-ray spectroscopy - scanning electron microscope) image of WS 2 (Er / Yb) reveals the presence of S, W, Er and Yb elements. The elemental mapping image of WS 2 (Er / Yb) is as Figure 6bAs shown, it further confirms that the distributions of S, W, Er, and Yb in WS2(Er / Yb) are relatively uniform; among which,...

[0038] S2. Lithography is performed on the WS 2 (Er / Yb) / Si heterojunction layer according to the designed electrode pattern;

[0039] Lithography is performed on the WS 2 (Er / Yb) / Si heterojunction layer according to the designed electrode pattern, including:

[0040] S21. Use a spin coater to spin coat the first layer of LOR photoresist on the WS 2 (Er / Yb) / Si heterojunction layer, and bake it on a drying platform at a temperature of 170°C for 10 min to remove the excess moisture in the photoresist and increase the adhesion between the photoresist and the substrate.

[0041] In this embodiment, spin coating the first layer of LOR photoresist includes two stages: The specific parameter settings are: The rotation speed in the first stage is 500 rmp, and the time is 5 s; the rotation speed in the second stage is 3500 rmp, and the time is 35 s;

[0042] S22. Use a spin coater to spin coat the second layer of S1805 photoresist on the first layer of LOR photoresist, and bake it on a drying platform at a temperature of 100°C for 10 min. The function is the same as the first time;

[0043] In this embodiment, spin coating the second layer of S1805 photoresist includes two stages: The specific parameter settings are: The rotation speed in the first stage is 500 rmp, and the time is 5 s; the rotation speed in the second stage is 2000 rmp, and the time is 25 s (seconds);

[0044] S23. Use the designed electrode pattern to perform laser direct writing on the WS 2 (Er / Yb) / Si heterojunction layer obtained in step S22; The photoresist is an organic substance, and its properties change after exposure, so as to transfer the electrode pattern to the substrate;

[0045] S24. Immerse the WS 2 (Er / Yb) / Si heterojunction layer obtained in step S23 in AZ300 developer for 60 s. The developer can remove the deteriorated photoresist in the exposed part. After 60 s (seconds), rinse it with deionized water to remove the residual developer, and dry it with a nitrogen gun.

[0046] S3. Perform magnetron sputtering on the lithographed WS 2 (Er / Yb) / Si heterojunction layer to grow metal electrodes on the WS 2 (Er / Yb) / Si heterojunction layer;

[0047] Magnetron sputtering is carried out using a sputtering coating machine. In this embodiment, the sputtering metal electrodes are chromium (Cr) and gold (Au), with thicknesses of 5 nm and 50 nm respectively.

[0048] S4. Remove the photoresist to obtain WS 2 (Er / Yb) / Si heterojunction photodetector.

[0049] Immerse the sample obtained in step S3 in acetone for 20 - 30 minutes. Acetone can dissolve the S1805 photoresist to separate the Au other than the electrodes from the substrate. Peel it off under a microscope until the electrodes are successfully peeled off; dissolve the remaining LOR photoresist with AZ300 developer (30S), then wash the sample with absolute ethanol, finally gently rinse the sample with deionized water, and blow off the moisture on the sample surface with high-purity nitrogen.

[0050] WS 2 (Er / Yb) / Si heterojunction photodetector's optical microscope picture is as Figure 7 shown.

[0051] The optoelectronic properties of the photodetector are tested by a 2636B type Keithley digital source meter combined with a commercial 635 nm laser light source (VCL - 635 nm M0 - 150 mW, Blueprint). Figure 8 a shows WS 2 (Er / Yb) / Si heterojunction photodetector's I - V characteristic curves under irradiation with different laser power densities. At a - 4V bias voltage, as the laser power density increases from 1.77 mW / cm 2 to 77.88 mW / cm 2 , the current of the WS 2 (Er / Yb) / Si device increases from - 6.47 μA to - 11.1 μA. Figure 8 b is the I - T curve of the WS2(Er / Yb) / Si heterojunction device under a - 4V bias voltage and laser irradiation with a power density of 61.95 mW / cm2. It can be seen that during the laser on - off switching process, the optical response of the device has good stability; among them, Voltage is voltage, and Current is current.

[0052] The above - mentioned embodiments further elaborate on the purpose, technical solutions, and advantages of the present invention. It should be understood that the above - mentioned embodiments are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made to the present invention within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector, characterized in that: The method comprises the following preparation steps: S1. Growing a WS2(Er / Yb) / Si heterojunction layer doped with rare earth materials on an SOI substrate by CVD; wherein CVD is chemical vapor deposition; S2, photolithography of the WS2(Er / Yb) / Si heterojunction layer according to the designed electrode pattern; S3, magnetron sputtering the WS2(Er / Yb) / Si heterojunction layer after photolithography to grow a metal electrode on the WS2(Er / Yb) / Si heterojunction layer; S4. Remove the photoresist to obtain a WS2(Er / Yb) / Si heterojunction photodetector.

2. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 1, characterized in that: The WS2(Er / Yb) / Si heterojunction layer doped with rare earth materials grown by CVD on SOI substrate includes: S11, cutting and cleaning the SOI substrate, and drying the cleaned SOI substrate with high-purity nitrogen; S12, weigh S powder and place it in a corundum boat, and place the corundum boat in temperature zone Ⅰ of a quartz tube furnace; weigh WO3, NaCl, ErCl3 and YbCl3, mix them evenly and place them in another corundum boat, and place the corundum boat in temperature zone Ⅱ of a quartz tube furnace; place the blow-dried SOI substrate upside down on the corundum boat in temperature zone Ⅱ of the quartz tube furnace; wherein S is sulfur, WO3 is tungsten trioxide, NaCl is sodium chloride, ErCl3 is erbium chloride, and YbCl3 is ytterbium chloride; S13, closing the quartz tube furnace, evacuating the gas pressure in the quartz tube furnace to vacuum, opening the gas inlet valve of the quartz tube furnace and introducing Ar gas at a flow rate of 200 mL / min, and when the pressure in the quartz tube furnace reaches the standard atmospheric pressure, opening the gas outlet valve of the quartz tube furnace and adjusting the flow rate of Ar gas to 60 mL / min; wherein the Ar gas is argon gas; S14, start the quartz tube furnace to heat temperature zone I and temperature zone II, and when temperature zone II is heated to 150° C., repeat step S13; S15, when temperature zone I and temperature zone II are heated to the first 5 minutes of the highest temperature, Ar / H2 mixed gas is introduced at a flow rate of 60 mL / min; wherein H2 is hydrogen; S16. When temperature zone I and temperature zone II are heated to the highest temperature, keep them at the highest temperature for ten minutes; after ten minutes, introduce Ar gas at a flow rate of 60 mL / min until temperature zone I and temperature zone II are naturally cooled to room temperature to obtain a WS2 (Er / Yb) / Si heterojunction layer.

3. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 2, characterized in that: Cutting and cleaning the SOI substrate include: cutting the SOI substrate into a size of 1.2 cm×2.2 cm and placing it in a beaker; pouring a cleaning agent into the beaker and placing the beaker in an ultrasonic cleaning machine for cleaning; and storing the cleaned SOI substrate in a beaker filled with anhydrous ethanol.

4. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 2, characterized in that: The masses of S powder, WO3, NaCl, ErCl3 and YbCl3 are 60mg, 30mg, 3mg, 3mg and 3mg respectively.

5. The WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 2, characterized in that: The ratio of Ar / H2 mixed gas is Ar:H2=9:1; wherein H2 is hydrogen.

6. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 2, characterized in that: The maximum temperature of temperature zone I is 200℃, and the maximum temperature of temperature zone II is 930℃.

7. The WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 1, characterized in that: The photolithography of the WS2(Er / Yb) / Si heterojunction layer according to the designed electrode pattern includes: S21, using a coating machine to spin-coat the first layer of LOR photoresist on the WS2 (Er / Yb) / Si heterojunction layer, and baking it on a drying platform at a temperature of 170° C. for 10 minutes; S22, using a coating machine to spin-coat a second layer of S1805 photoresist on the first layer of LOR photoresist, and baking it on a drying platform at a temperature of 100° C. for 10 minutes; S23, performing laser direct writing on the WS2(Er / Yb) / Si heterojunction layer obtained in step S22 using the designed electrode pattern; S24. Place the WS2(Er / Yb) / Si heterojunction layer obtained in step S23 in AZ300 developer for 60 seconds. After 60 seconds, rinse with deionized water and blow dry with high-purity nitrogen.

8. A WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 7, characterized in that: When the first layer of LOR photoresist is spin-coated on the WS2(Er / Yb) / Si heterojunction layer using a coating machine, the first stage speed of the coating machine is 500 rpm, the time is 5 s, and the second stage speed is 3500 rpm, the time is 35 s; When the second layer of S1805 photoresist is spin-coated on the first layer of LOR photoresist using a coating machine, the first stage speed of the coating machine is 500 rpm, the time is 5 s; the second stage speed is 2000 rpm, the time is 25 s.

9. The WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 1, characterized in that: The metal electrodes are chromium and gold, with thicknesses of 5nm and 50nm respectively.

10. The WS2(Er / Yb) / Si van der Waals heterojunction photodetector according to claim 1, characterized in that: Removing the photoresist includes: dissolving the S1805 photoresist of the sample obtained in step S3 with acetone, dissolving the LOR photoresist of the sample with AZ300 developer, cleaning the sample with anhydrous ethanol, rinsing the sample with deionized water, and blowing dry the moisture on the surface of the sample with high-purity nitrogen.

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