Patent Application
20230098095
This patent application claims the benefit and priority of the Chinese Pat. Application No. 202111093985.3 filed on Sep. 17, 2021. The entire disclosure of the above application is incorporated herein by reference.
The present disclosure belongs to the technical field of mixed-dimensional van der Waals heterojunctions, and in particular relates to a photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction and a preparation method and use thereof.
GaAs belongs to the second-generation N-type semiconductor materials of group III-V compounds, has a direct band gap of 1.42 eV and high electron mobility, and is very suitable for forming light-emitting diodes, photovoltaic cells and near-infrared photodetectors with high performances. However, the high surface density of state of GaAs greatly reduces the light on/off ratio and photoresponsivity of photodetectors. Since the discovery of graphene, two-dimensional (2D) materials with unique photoelectric properties have attracted extensive attention. Due to the structural advantages of no surface dangling-bonds, no need for lattice matching and generally weak van der Waals interactions of the 2D materials, random assembling and stacking may be allowed to generate various types of van der Waals heterojunctions. In post-Moore era, research based on the mixed-dimensional heterojunctions of two-dimensional materials/three-dimensional materials has greatly promoted the integration technology development of 3D semiconductors such as Si and GaAs, and has become one of the hottest researching frontiers in the fields of material science and condensed matter physics. For example, Dhyani et al. have verified that a molybdenum disulfide/Si device has a photoresponsivity of 8.75 A/W and a fast response time of 10 µs. Meanwhile, Wu et al. have found that a molybdenum disulfide/GaAs device is improved in light absorption coefficient, thereby greatly improving specific detectivity under zero bias.
In the 2D material system of the post-transition metal chalcogenide (PTMC), stannous sulfide and stannous selenide are layered nano-materials with a band gap in a range of 0.7-1.55 eV, and are P-type semiconductor materials with great advantages such as low cost, non-toxicity and abundant yield. Among them, the α-phase crystal structure with excellent thermal stability is an orthorhombic crystal system, which has obvious in-plane anisotropy especially in optics and electricity. According to theoretical speculation, the light absorption coefficient and the carrier mobility of stannous sulfide in the visible-infrared range may reach 5 × 104 cm-1 and 7.35 × 104 cm2V-1s-1, respectively. Stannous selenide also shows an ultra-high light absorption coefficient (about 1 × 105 cm-1) and a relatively high thermoelectric ZT factor. The characteristics as above indicate that these two binary compounds have great application prospects in the fields of thermoelectric conversion, ferroelectric conversion, polarization imaging, solar photovoltaic cell and flexible devices. However, due to the strong interlayer force, considerable deep-level defects and strong electric field shielding effect between layers, the materials above have the problems such as difficulty in mechanical peeling, slow photoresponse, mediocre current on/off properties and limited light absorption efficiency, seriously hindering the development of these materials.
In recent years, alloy engineering has been an important research mean that may not only effectively control the band structures and the optical and electrical properties of semiconductors, but also suppress the deep-level defects in binary compounds. For example, Tan et al. have found that stannous selenide sulfide has a higher carrier mobility and better thermodynamic stability. In addition, Padha et al. have reported that a stannous selenide sulfide alloy (with a mass ratio of sulfur to selenium of 2:3) is significantly improved in light absorption coefficient (>105 cm-1). Chong et al. have studied the polarization properties of stannous selenide sulfide by using Raman spectroscopy and have found that the polarization behavior of stannous selenide sulfide is closely related to excitation wavelength. The research team of the inventor has made some achievements in preparation, anisotropy and photoelectric devices of stannous selenide sulfide single-crystal nanosheets. Despite the great progress in exploring the preparation, anisotropy and photoelectric devices of stannous selenide sulfide in recent years, there is still a long way to go to achieve the photodetectors with high performances. At present, the mixed-dimensional P-N heterojunctions of P-type stannous selenide sulfide/N-type GaAs have not been reported yet. The combination of the two may form a built-in electric field which is expected to realize self-driven broad-spectrum photoelectronic functions and polarization imaging functions, thus promoting the research and development of GaAs integration technologies.
In order to overcome the above deficiencies and shortcomings in the prior art, an objective of the present disclosure is to provide a photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction.
Another objective of the present disclosure is to provide a method for preparing the above photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction.
A yet another objective of the present disclosure is to provide use of the above photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction.
The objectives of the present disclosure are achieved by the following technical solutions:
A photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction, wherein the photodiode comprises a structure of the stannous selenide sulfide nanosheet/GaAs heterojunction, obtained by overlapping a stannous selenide sulfide nanosheet and GaAs, forming Au electrodes through thermal vapor deposition on the stannous selenide sulfide nanosheet and GaAs, respectively, and conducting an annealing treatment in a protective gas at a temperature in a range of 150-250° C.
In some embodiments, the Au electrode has a thickness of 20-500 nm; the protective gas is nitrogen or argon; the annealing treatment is conducted for 15-120 min; the stannous selenide sulfide nanosheet has a lateral dimension of 10-100 µm and a thickness of 5-100 nm.
In some embodiments, the photodiode comprises a photodiode based on a lateral stannous selenide sulfide nanosheet/GaAs heterojunction and a photodiode based on a vertical stannous selenide sulfide nanosheet/GaAs heterojunction; in the photodiode based on a lateral stannous selenide sulfide nanosheet/GaAs heterojunction, the Au electrodes are formed through thermal vapor deposition on the stannous selenide sulfide nanosheet and GaAs, respectively; in the photodiode based on a vertical stannous selenide sulfide nanosheet/ GaAs heterojunction, the Au electrodes are formed through thermal vapor deposition on the stannous selenide sulfide nanosheet and a back of GaAs, respectively.
A method for preparing the photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction, comprising:
S1, cleaning an N-type GaAs substrate with acetone, isopropanol and deionized water in sequence and drying with a nitrogen gun, and depositing a medium layer film on the N-type GaAs substrate by atomic layer deposition or plasma enhanced chemical vapor deposition;
S2, photoetching and developing a window on the medium layer film by using ultraviolet lithography, and placing in an etchant to completely etch an exposed medium layer window to obtain a GaAs window;
S3, spin-coating a surface of a stannous selenide sulfide nanosheet/substrate with a soluble polymer solution, and heating and solidifying at a temperature in a range of 100-150° C. to obtain a polymer film/stannous selenide sulfide nanosheet/substrate;
S4, immersing the polymer film/stannous selenide sulfide nanosheet/substrate in a treatment solution, then aligning the polymer film/stannous selenide sulfide nanosheet separated from the substrate with the GaAs window obtained in step S2, and heating at a temperature in a range of 100-150° C. to make the stannous selenide sulfide nanosheet contact with the GaAs window to form a van der Waals heterojunction, so as to obtain a polymer film/stannous selenide sulfide nanosheet/GaAs substrate; and
S5, heating the polymer film/stannous selenide sulfide nanosheet/GaAs substrate in acetone at 70° C., then transferring to a fresh acetone solution for immersion, and cleaning to remove the polymer film; forming Au electrodes through thermal vapor deposition on the stannous selenide sulfide nanosheet and the GaAs window, respectively, and then conducting an annealing treatment in a protective gas at a temperature in a range of 150-250° C. to obtain the photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction.
In some embodiments, in step S1, the medium layer film is of SiO2, Al2O3 or HfO2, and has a thickness of 12-300 nm.
In some embodiments, in step S2, the etchant comprises an aqueous hydrofluoric acid solution and an aqueous ammonium fluoride solution; a volume ratio of the aqueous hydrofluoric acid solution to the aqueous ammonium fluoride solution is in a range of (1-4):(6-24); a volume concentration of the aqueous hydrofluoric acid solution is in a range of 40-49%, and a volume concentration of the aqueous ammonium fluoride solution is in a range of 30-40%.
In some embodiments, in step S3, the stannous selenide sulfide nanosheet has a lateral dimension of 10-100 µm and a thickness of 5-100 nm; the substrate is of SiO2/Si, mica or sapphire.
In some embodiments, in step S3, the soluble polymer solution is an anisole solution of polymethyl methacrylate or a toluene solution of polystyrene with a mass percentage of 8-10 wt.%; the spin-coating is conducted at a speed in a range of 3,000-7,000 rpm for 30-120 S; the heating is conducted for 15-45 min.
In step S3, the conditions for preparing a stannous selenide sulfide single-crystal nanosheet by physical vapor deposition (PVD) of the stannous selenide sulfide are as follows: placing a precursor on a quartz boat, which is performed by mixing stannous sulfide and stannous selenide high-purity powders in a predetermined proportion, placing a SiO2/Si wafer surface-treated with oxygen plasma above the quartz boat with a polished side down, with a pressure of 10-3 \-10 Torr, a heating rate of 20° C./min, a growth temperature in a range of 750-800° C., under an atmosphere selected from the group consisting of nitrogen and argon, and with a gas flow of 2-10 sccm. When the growth temperature reaches 750-800° C., the quartz boat is moved to the center of a heating zone by moving a quartz tube for holding for 2-4 min, and the quartz tube is moved to move the quartz boat out of the heating zone. After cooling at room temperature, a large number of flake samples are observed with the help of an optical microscope. The stannous selenide sulfide nanosheet has a thickness of 5-200 nm and a lateral dimension of 10-100 µm.
In some embodiments, in step S4, the heating is conducted for 5-20 min; in step S5, the heating is conducted for 7-15 min, the immersion is conducted for 10 min-12 h, and the cleaning is conducted with solvents of isopropanol, anhydrous ethanol and deionized water successively.
Use of the photodiode based on a stannous selenide sulfide nanosheet/GaAs heterojunction in the field of photovoltaic devices or self-driven polarization-sensitive photodetectors is provided.
Compared with the prior art, the present disclosure has the following benefits:
The technical solutions in the examples of the present disclosure will be described below clearly and completely with reference to the drawings in the present disclosure, which should not be construed as limiting the protection scope of the present disclosure. All other examples obtained by those ordinary skilled in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure. The experimental methods described in the following examples are conventional methods unless otherwise specified; and the reagents and equipment can be obtained from commercial sources unless otherwise specified. The present disclosure will be further described in detail below.
Step 1. A 2-inch Si-doped N-type GaAs substrate was cut into a size of 1 cm × 1 cm, and ultrasonically cleaned with acetone, isopropanol and deionized water in sequence for 5-10 min to obtain a clean GaAs substrate. A SiO2 film with a thickness of 300 nm was deposited on the GaAs substrate at 300° C. by PECVD (Plasma Enhanced Chemical Vapor Deposition).
Step 2. A 1 mm × 1 mm window was developed on the substrate with a maskless UV lithography machine, and then placed in a plastic beaker containing an etchant (the etchant was a mixture of 20 mL of an aqueous hydrofluoric acid solution with a volume concentration of 49% and 120 mL of an aqueous ammonium fluoride solution with a volume concentration of 40%) for etching for 1 min to expose the GaAs surface, and immersed in acetone and deionized water successively to obtain an etched GaAs window.
Step3. A stannous selenide sulfide nanosheet was prepared by PVD as the following steps: stannous sulfide and stannous selenide powders were compounded according to a mass ratio of 1:1, uniformly shaken well through a centrifugal tube, and slowly transferred to a quartz boat. A 1 cm × 1 cm SiO2/Si wafer surface-treated with O2 plasma was placed above the quartz boat with a polished side down. The above steps were performed with a pressure of 10-3 \-10 Torr, a heating rate of 20° C./min, under an atmosphere selected from the group consisting of nitrogen and argon, and with a gas flow of 2-10 sccm, preferably 5 sccm. When the temperature reached 750-800° C., the quartz boat was moved to the center of a heating zone by moving a quartz tube for holding for 2-4 min, and the quartz tube was moved to move the quartz boat out of the heating zone. After cooling at room temperature, a large number of dark green flake samples were observed with a microscope. The stannous selenide sulfide single-crystal nanosheet had a thickness of 5-200 nm and a lateral dimension of 10-100 µm. The stannous selenide sulfide alloy nanosheet with a thickness of about 22 nm was selected for subsequent transfer.
Step 4. A PMMA-anisole film was formed by spin-coating with an 8 wt.% PMMA anisole solution on the stannous selenide sulfide nanosheet with a spin coater at 4000 rpm for 1 min. After spin-coating two times, the spin-coated product was heated on a heating plate at 150° C. for 30 min to remove the anisole solvent, and then the stannous selenide sulfide nanosheet/PMMA was transferred to a buffered oxide etchant (BOE) for immersion and etching for 90 s and immediately transferred to a glass Petri dish filled with deionized water. The stannous selenide sulfide nanosheet/PMMA film was carefully lifted with a tweezer and cleaned three times with deionized water. The stannous selenide sulfide nanosheet/PMMA film was transferred to the GaAs substrate, such that the stannous selenide sulfide nanosheet was in contact with the GaAs window, and an overlapping part of the two formed a van der Waals heterojunction. Then, the PMMA film was softened by heating in hot acetone at 70° C. for 7 min, and immersed in a new acetone solution for 15 min to dissolve PMMA, obtaining a clean stannous selenide sulfide nanosheet/GaAs heterojunction.
Step 5. A 60 nm Au electrode was prepared on the stannous selenide sulfide nanosheet/GaAs heterojunction with a maskless UV lithography system and a thermal evaporation machine, and then annealed at 200° C. for 30 min under argon to remove small molecular impurities between the electrode and semiconductor materials to reduce the contact barrier, obtaining a photodiode based on lateral stannous selenide sulfide/GaAs heterojunction.
The difference from Example 1 is that in step 3, the precursor was prepared by mixing stannous sulfide and stannous selenide powders in a mass ratio of 1:3. It should be noted that due to the lower equilibrium vapor pressure of stannous selenide, selenium in the obtained stannous selenide sulfide nanosheet had a relatively high content. Therefore, the mass of stannous selenide could be reduced as appropriate.
The difference from Example 1 is that in step 5, the Au electrodes were formed through thermal vapor deposition. In addition to preparing a 60 nm Au electrode on the surface of the stannous selenide sulfide nanosheet/GaAs heterojunction, a 100 nm Au film was also formed through thermal vapor deposition on a back of the GaAs. Then the sample was bonded to a copper sheet through a silver paste, and heated at 80° C. for 20 min on a heating plate, obtaining a photodiode based on a vertical stannous selenide sulfide nanosheet/GaAs heterojunction. Source and drain probes were respectively tied on the stannous selenide sulfide nanosheet and the copper sheet to test the vertical current.
The difference from Example 1 is that in step 4, when the stannous selenide sulfide nanosheet was transferred to the GaAs substrate, the stannous selenide sulfide nanosheet was spin-coated with a polystyrene (PS) toluene solution with a mass fraction of 9% at a high speed of 3,000 rpm for 1 min. Then the spin-coated product was heated on a heating plate at 90° C. for 20 min to form a PS film. The PS film was immersed in a glass petri dish filled with deionized water. The edge was carefully scraped with a sharp-nose tweezer and the film was slowly lifted, obtaining a stannous selenide sulfide nanosheet/PS film. After aligning the stannous selenide sulfide nanosheet/PS film with the GaAs window through an optical microscope, the GaAs substrate was continuously heated at 90° C. to make the PS film fully contact with the GaAs substrate, and finally immersed in a toluene solvent for 1-12 h, obtaining the stannous selenide sulfide nanosheet/GaAs heterojunction.
In the present disclosure, the photodiode includes a photodiode based on a lateral stannous selenide sulfide nanosheet/GaAs heterojunction and a photodiode based on a vertical stannous selenide sulfide nanosheet/GaAs heterojunction. In the photodiode based on a lateral stannous selenide sulfide nanosheet/GaAs heterojunction, the Au electrodes are formed through thermal vapor deposition on the stannous selenide sulfide nanosheet and a window of GaAs, respectively; in the photodiode based on a vertical stannous selenide sulfide nanosheet/ GaAs heterojunction, the Au electrodes are formed through thermal vapor deposition on the stannous selenide sulfide nanosheet and a back of GaAs, respectively. The Au electrode has a thickness of 20-500 nm. The protective gas is of nitrogen or argon. The annealing treatment is conducted for 15-120 min. The stannous selenide sulfide nanosheet has a lateral dimension of 10-100 µm and a thickness of 5-100 nm. In the present disclosure, the photodiode based on a stannous selenide sulfide nanosheet (an element mass ratio of sulfur to selenium is 1:1)/GaAs heterojunction has a wide spectral response (405-1,064 nm) and self-driven photoelectric performance (under 405 nm laser irradiation, its maximum photoresponsivity reaches 10.2 A·W-1, the maximum specific detectivity reaches 4.8×1012 Jones, and the rise and fall times are 0.5/3.47 ms). In addition, the stannous selenide sulfide nanosheet/GaAs heterojunction has dichroic ratios of 1.25 at 405 nm and 1.45 at 635 nm, and a remarkable polarized photocurrent can be obtained, which shows good potential for use in self-driven polarization-sensitive photodetectors at specific wavelengths.
The above examples are preferred embodiments of the present disclosure. However, the embodiments of the present disclosure are not limited by the above examples. Any change, modification, substitution, combination and simplification made without departing from the spiritual essence and principle of the present disclosure should be an equivalent replacement manner, and all are included in the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111093985 .3 | Sep 2021 | CN | national |
