Two-dimensional bismuth compound / gallium arsenide heterojunction, preparation method thereof and application of two-dimensional bismuth compound / gallium arsenide heterojunction in photoelectric detector

Abstract

The invention discloses a two-dimensional bismuth compound / gallium arsenide heterojunction, a preparation method thereof and application of the two-dimensional bismuth compound / gallium arsenide heterojunction in a photoelectric detector, and belongs to the field of semiconductor devices. Two-dimensional bismuth compounds (bismuth selenide or bismuth telluride) are prepared on a cleaned and pre-masked gallium arsenide substrate through an electron beam evaporation method, the two-dimensional bismuth compound / gallium arsenide heterojunction is formed, and the thickness of a two-dimensional bismuth compound film is controllable. And preparing a symmetric or asymmetric electrode by electron beam evaporation to obtain a prototype device of the photoelectric detector. The preparation process is simple, the repeatability is good, the detector can achieve the high detection rate (up to-1014 Jones) of optical signals from the ultraviolet band to the near-infrared band (367-1064 nm) under the room temperature condition and without bias voltage, and meanwhile the excellent cycling stability and air stability are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and particularly relates to a two-dimensional bismuthide / gallium arsenide heterojunction, a preparation method thereof, and an application thereof in a photodetector Background Art

[0002] Two-dimensional materials have excellent electron transport and optoelectronic conversion properties. At the same time, their bandgap coverage range is wide, and they have attracted much attention in the field of new-generation electronics and optoelectronic devices. Heterojunctions based on two-dimensional materials can not only utilize the excellent optoelectronic properties of two-dimensional materials, but the junction region formed at the interface can also provide a built-in electric field, effectively reducing the dark current, promoting the separation of photo-generated carriers, and improving the photodetection performance, becoming a research hotspot of two-dimensional material-based photodetectors. Effectively integrating the advantages of two-dimensional materials and other semiconductor materials to prepare high-performance, wide-band, and self-powered photodetectors based on heterojunctions is of great significance in both military and civilian fields. Typical two-dimensional bismuthides: bismuth telluride (Bi2Te3) and bismuth selenide (Bi2Se3) have a narrow bulk bandgap (0.14 - 0.3 eV), show strong light-matter interaction in the long-wave range, and exhibit great application potential in the fields of infrared and visible light detection. In addition, due to the electron-orbital coupling effect, this material has topological insulating properties, and its surface is a Dirac cone-type topological surface state protected by time-reversal symmetry, with a carrier mobility as high as ~10 3 cm 2 V -1 s -1 , which is the basis for the fast response of the device. The van der Waals layered structure of two-dimensional bismuthides also ensures that the material surface is smooth and has no dangling bonds, which is beneficial to its integration with other materials to form a heterojunction and can avoid the lattice mismatch problem in the heteroepitaxial process. Therefore, based on the above application advantages of two-dimensional bismuthides in the field of photodetection, combining with semiconductor materials with ultraviolet band response capabilities to prepare heterojunctions, such as III-V semiconductors such as gallium arsenide and gallium nitride, is a feasible means to construct high-performance, wide-band, and self-powered detectors

[0003] However, the construction of two-dimensional material-based heterojunctions is often restricted by the preparation methods. The commonly used preparation method for two-dimensional material heterojunctions is to stack the nanosheets prepared by mechanical exfoliation or chemical vapor deposition using the transfer method, such as the Bi2Se3 / Bi2O2Se single crystal sheet heterojunction, etc. However, it is often difficult to achieve the preparation of large-scale heterojunctions with uniform and controllable thickness by this method, and its application is limited in the development trend of automated and integrated device preparation. Chemical vapor deposition and molecular beam epitaxy are two main means for directly growing and constructing heterojunctions. These two methods have high requirements for the growth temperature, and the growth of two-dimensional materials is selective to the substrate. In addition, molecular beam epitaxy is expensive and cannot be widely applied industrially. Magnetron sputtering has no strict requirements for the substrate, but the materials prepared by this method have uneven thickness and large roughness, making it difficult to construct high-quality heterojunctions. Therefore, there is an urgent need to develop a preparation method for two-dimensional bismuthide-based heterojunctions with controllable thickness, and select semiconductor materials with appropriate band gaps as substrates to construct wide-band self-powered photodetectors, so as to obtain high detection rates in the infrared-visible-ultraviolet range without an external bias voltage. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of poor controllability of the thickness of two-dimensional materials, high growth temperature, and strong substrate dependence in existing two-dimensional material-based heterojunctions, and provide a highly efficient, low-cost, two-dimensional bismuthide / gallium arsenide heterojunction with controllable thickness, its preparation method, and its application in photodetectors. The present invention uses electron beam evaporation technology to prepare two-dimensional bismuthides with controllable thickness, Bi2Te3 and Bi2Se3, on a gallium arsenide substrate, and designs a wide-band self-powered photodetector with high detection rates and on-off ratios in the infrared-visible-ultraviolet range under zero bias based on this heterojunction. The materials in the present invention are rich in reserves, the method adopted is low-cost and the process is simple, which can adapt to automated industrial production and has application prospects in the field of semiconductor optoelectronic integrated devices.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] A two-dimensional bismuthide / gallium arsenide heterojunction, wherein the heterojunction uses gallium arsenide as a semiconductor substrate, and a two-dimensional bismuthide thin film covers a partial area of the substrate, and there is a clear demarcation line between the two-dimensional bismuthide and gallium arsenide.

[0007] Further, the bismuthide is bismuth selenide or bismuth telluride.

[0008] A photodetector containing the above two-dimensional bismuthide / gallium arsenide heterojunction, wherein rectangular or square metal electrodes are used on the surfaces of the bismuthide thin film and gallium arsenide; the two electrodes are distributed in parallel on both sides of the demarcation line between the two-dimensional bismuthide and gallium arsenide, and the area between the two electrodes is the light incident area.

[0009] Further, the material of the metal electrode is one or two of gold, aluminum, nickel, silver, platinum or copper. The electrodes on the bismuthide thin film and gallium arsenide are the same or different metals, which are respectively called symmetric electrodes and asymmetric electrodes, and the electrode thickness is 20 - 100 nm.

[0010] A preparation method of the above-mentioned two-dimensional bismuthide / gallium arsenide heterojunction, and the method is as follows:

[0011] Step 1: Clean the gallium arsenide substrate;

[0012] Step 2: Fix a mask on the gallium arsenide substrate to expose part of the gallium arsenide. Fix the mask face down on the sample area at the top of the chamber of the electron beam evaporation equipment. Place the evaporation target bismuthide in a graphite crucible and place it in the target area of the chamber. The evaporation target used is bismuth selenide or bismuth telluride powder (purity 99.99%), which is respectively used to prepare bismuth selenide and bismuth telluride thin films.

[0013] Step 3: Use the electron beam evaporation equipment to prepare a bismuthide thin film on the gallium arsenide substrate;

[0014] Step 4: Place the bismuthide / gallium arsenide heterojunction obtained in Step 3 in a quartz tube, which is located at the heating center of the tube furnace. Seal the quartz tube and continuously introduce an inert gas, and set the pressure in the quartz tube to atmospheric pressure;

[0015] Step 5: Anneal the bismuthide / gallium arsenide heterojunction. After the annealing is completed and it is naturally cooled to room temperature, take out the sample to obtain a bismuthide / gallium arsenide heterojunction with good crystallinity.

[0016] Further, the specific content of Step 1 is: ultrasonically clean with deionized water, ethanol, acetone, and isopropanol in sequence for 30 min, then treat the cleaned substrate with oxygen plasma for 15 min, and then place it in a hot oven and let it stand for 20 min to dry.

[0017] Further, in Step 3, when the electron beam evaporation equipment prepares the bismuthide thin film, the vacuum degree is not higher than 10 -4 Pa, the electron beam current is 0.5 - 1.5 mA, and the evaporation rate is The time is 10 - 100 min. By controlling the evaporation time, a bismuthide thin film with controllable thickness is obtained. After annealing, the film thickness is 30 - 150 nm.

[0018] Further, in Step 4, the inert gas is argon (Ar) gas, the gas flow rate is 20 - 80 sccm, and the pressure is atmospheric pressure.

[0019] Further, in Step 5, the temperature of the annealing treatment is 250 - 350 °C, and the time is 120 - 200 min.

[0020] A method for preparing the above-mentioned photodetector, the method comprising: covering an electrode mask on the bismuthide / gallium arsenide heterojunction, and using an electron beam evaporation device to prepare metal electrodes for the bismuthide / gallium arsenide heterojunction; the electrode mask includes two rectangular or square holes, which are distributed in parallel, the length and width of the electrodes are 10-400 μm, and the spacing is 50-500 μm, which are respectively located on the surfaces of bismuthide and gallium arsenide. Under zero bias, use lasers with wavelengths of 367 nm, 405 nm, 520 nm, 638 nm, 850 nm, 940 nm, and 1064 nm to irradiate, and measure the current change between the two electrodes of the photodetector, thereby obtaining the switching ratio and detectivity of the device in the ultraviolet-visible-infrared wavelength range. Utilizing the photoresponse, the heterojunction detector can also achieve the imaging function of a unit device.

[0021] The beneficial effects of the present invention compared with the prior art are as follows: The present invention prepares high-quality and thickness-controllable two-dimensional bismuthide / gallium arsenide heterojunctions, including bismuth selenide / gallium arsenide (Bi2Se3 / GaAs) and bismuth telluride / gallium arsenide (Bi2Te3 / GaAs) heterojunctions, by means of electron beam evaporation technology supplemented by low-temperature annealing. The method of the present invention has simple material and device preparation processes and good repeatability, and is easy to realize device integration; at the same time, the raw materials used are rich in reserves and low in cost, and are suitable for large-scale and automated industrial production. Symmetric electrode and asymmetric electrode photodetectors are designed based on the bismuthide / gallium arsenide heterojunction. The detector has the self-powered characteristic, can work at room temperature and zero bias, saves energy, and is environmentally friendly. The detector responds to optical signals in the ultraviolet-visible-infrared range, can achieve wide-band photodetection, has a high switching ratio and detectivity, can achieve nanowatt-level weak light detection, and has a sensitive response. The detector has excellent cycle stability and air stability, and still exhibits excellent photodetection performance after being stored in air for 2 months. In addition, the detector of the present invention also has multi-band imaging capabilities. Description of the Drawings

[0022] Figure 1 Atomic force microscope images of bismuth telluride thin film / gallium arsenide heterojunctions with different thicknesses prepared in Example 1;

[0023] Figure 2 Raman spectrum of the bismuth telluride / gallium arsenide heterojunction prepared in Example 1;

[0024] Figure 3 Raman spectrum of the bismuth selenide / gallium arsenide heterojunction prepared in Example 2;

[0025] Figure 4 Optical photograph of the bismuth telluride / gallium arsenide heterojunction photodetector prepared in Example 3;

[0026] Figure 5On-off photocurrent-time curves of bismuth telluride / gallium arsenide heterojunction photodetectors with different thicknesses prepared in Example 3 under 940 nm light illumination;

[0027] Figure 6 On-off photocurrent-time curves of bismuth telluride / gallium arsenide heterojunction detectors prepared in Example 3 under 940 nm light illumination after storage for 1 day and 2 months;

[0028] Figure 7 On-off photocurrent-time curves of the bismuth telluride / gallium arsenide heterojunction described in Example 4 under ultraviolet (367 nm), visible (405 nm, 520 nm, 638 nm), and infrared light (850 nm, 940 nm, 1064 nm) illumination;

[0029] Figure 8 Comparison chart of detectivities of the bismuth telluride / gallium arsenide heterojunction described in Example 4 under different light illuminations;

[0030] Figure 9 Imaging diagrams of the bismuth telluride / gallium arsenide heterojunction described in Example 4 as a single-pixel sensing unit under ultraviolet (367 nm), visible (520 nm), and infrared light (1064 nm) illumination. Detailed implementation manners

[0031] The following describes the preferred embodiments of the present invention. It should be understood that the described embodiments are for explaining the present invention in detail, and are only partial embodiments of the invention, not for limiting the present invention. All other embodiments obtained based on the present invention, without creative progress, fall within the scope protected by the present invention.

[0032] Example 1:

[0033] A preparation method of a bismuth telluride / gallium arsenide heterojunction, in which the thickness of the bismuth telluride thin film is controllable. The specific implementation steps are as follows: Clean the gallium arsenide substrate, fix the mask on the gallium arsenide substrate to expose half of the surface of the gallium arsenide substrate, fix it face down on the sample area at the top of the electron beam evaporation equipment cavity, and place the bismuth telluride in the graphite crucible in the cavity. Open the vacuum pump to make the vacuum degree in the cavity reach 10 -4 Pa, the electron beam current is 1.0 mA, and the evaporation rate is controlled at Within the range. The evaporation time of the telluride thin film was set to 20, 30, 40, and 50 minutes, and telluride thin films with thicknesses of 51, 80, 102, and 117 nm were obtained on the gallium arsenide substrate respectively. The bismuth telluride / gallium arsenide heterojunction was placed in the heating center of the tube furnace in the quartz tube. The quartz tube was sealed and pumped to a vacuum state, and then high-purity argon gas was introduced to purify the quartz tube for 5 minutes. Then, high-purity argon gas was introduced to make the pressure inside the tube reach atmospheric pressure, and the gas flow rate was 60 sccm. The tube furnace was set to hold at 270 °C for 150 minutes for annealing treatment. After the treatment was completed and the sample was naturally cooled to room temperature, the sample was taken out, and a bismuth telluride / gallium arsenide heterojunction with good crystal quality could be obtained.

[0034] Figure 1 Shown are the atomic force microscopy images of bismuth telluride thin film / gallium arsenide heterojunctions with different thicknesses, and the sample height changes along the white solid line in the figure. On the left side of the figure is bismuth telluride, and on the right side is the gallium arsenide substrate. The thicknesses of the bismuth telluride thin films are 51, 80, 102, and 117 nm respectively, indicating that a heterojunction of a bismuth telluride thin film with a controllable thickness and a gallium arsenide substrate can be obtained by controlling the electron beam evaporation time. Figure 2 Is the Raman spectrum of the bismuth telluride / gallium arsenide heterojunction, where the thickness of bismuth telluride is 80 nm. The Raman spectrum shows that two characteristic peaks of bismuth telluride are located at 102 and 131 cm -1 , which are related to the in-plane vibration and out-of-plane vibration phonons of the atomic plane respectively, proving that the crystal quality of the bismuth telluride thin film is good. In addition, there are two characteristic peaks of gallium arsenide in the Raman spectrum, located at 266 and 288 cm -1 , which are the TO and LO vibration modes of gallium arsenide.

[0035] Example 2:

[0036] This example provides a preparation method of a bismuth selenide / gallium arsenide heterojunction. The difference in the specific implementation steps from Example 1 is that the target material in Example 1 was replaced with bismuth selenide powder, the evaporation time of the selenide thin film was set to 30 minutes, the electron beam current was 1.0 mA, and the evaporation rate was During the annealing process, the temperature of the tube furnace was set to 300 °C, and the annealing time was 180 minutes. The operation steps and other conditions remained unchanged, thus obtaining a bismuth selenide / gallium arsenide heterojunction.

[0037] Figure 3 Is the Raman spectrum of the bismuth selenide / gallium arsenide heterojunction. In addition to the TO and LO vibration modes of gallium arsenide, the other two Raman peaks are the Raman characteristic peaks of bismuth selenide, located at 129 and 174 cm -1 . It is confirmed that the crystal quality of the bismuth selenide / gallium arsenide heterojunction prepared by the method described in the present invention is excellent.

[0038] Example 3:

[0039] This embodiment provides a method for preparing a bismuth telluride / gallium arsenide heterojunction broadband self-powered photodetector and its application at an infrared light wavelength of 940 nm. The specific implementation steps are as follows:

[0040] Using the bismuth telluride / gallium arsenide heterojunction obtained in Example 1, fix the mask template of the metal electrode on the sample, and expose the predetermined electrode area on the gallium arsenide surface. Place it in the sample area of the electron beam evaporation equipment cavity, place the gold target in the graphite crucible, and put it in the target area of the cavity. Evacuate to 10 -4 Pa. Start electron beam evaporation, adjust the electron beam current to 90.0 mA, melt the metal target, and prepare a gold electrode on the gallium arsenide substrate surface. After preparation, take out the sample. Re-fix the electrode mask template to expose the predetermined electrode area on the bismuth telluride surface, replace the target with an aluminum target, repeat electron beam evaporation, set the electron beam current to 30.0 mA, and prepare an aluminum electrode on the bismuth telluride surface. The two electrodes are 250 μm long, 150 μm wide, and the electrode spacing is 250 μm. Finally, a bismuth telluride / gallium arsenide heterojunction broadband self-powered photodetector with asymmetric electrodes is obtained. Figure 4 Is the optical photograph of an 80-nm-thick bismuth telluride / gallium arsenide heterojunction photodetector.

[0041] Subsequently, connect the device to a semiconductor analyzer and other current-measuring devices through the two electrodes, and test the detection performance of the heterojunction device by periodically turning on / off infrared light (940 nm) under room temperature conditions and without an externally applied bias voltage. Figure 5 Shows the on / off photocurrent-time curves of heterojunctions formed by bismuth telluride and gallium arsenide with thicknesses of 51, 80, 102, and 117 nm under 940-nm light illumination. When the light is illuminated, the device current rapidly increases, and when the light is removed, the current rapidly returns to the initial level, indicating that the device is sensitive to 940-nm light illumination. The photocurrent of the device remains stable within multiple cycles, indicating its excellent detection ability of stability, sustainability, and repeatability. In addition, the thickness has an obvious influence on the response performance of the photodetector, and the device performance can be optimized in practical applications through the preparation method with controllable thickness described in the present invention.

[0042] After storing the device in air for 1 day and 2 months, repeat the above detection performance test steps to obtain the on / off photocurrent-time curves of the heterojunction device under 940-nm light illumination, as shown in Figure 6 . The test shows that the device performance remains good after being stored for 2 months without special packaging, and the photocurrent can still reach 95% of the initial value, proving that the device has good stability.

[0043] Example 4:

[0044] This embodiment provides a detection application and an imaging application of a bismuth telluride / gallium arsenide heterojunction broadband self-powered photodetector at multiple wavelengths. The specific implementation steps are as follows:

[0045] Use the bismuth telluride / gallium arsenide heterojunction photodetector obtained in Example 3 to test its detection applications for ultraviolet (367 nm), visible (405 nm, 520 nm, 638 nm), and infrared light (850 nm, 1064 nm) at room temperature and zero bias. Connect the device to a device that can measure current, such as a semiconductor analyzer, and test the current change of the device at zero bias by periodically turning on / off the light sources of the above different wavelengths to obtain the on / off light response current-time curve. At the same time, summarize it together with the current-time curve measured under 940 nm light illumination in Example 3 to Figure 7 . It can be seen that the heterojunction photodetector described in the present invention has the ability to detect ultraviolet, visible, and infrared light, and it remains stable and responds quickly within multiple cycles. Figure 8 Shows the calculated detectivity of the device at zero bias under different light illumination conditions, and the highest detectivity can reach Jones (850 nm). Except for 1064 nm light illumination, at other wavelengths, the detectivity of the device is about 10 13 ~10 14 Jones, indicating that the detector described in the present invention has excellent broadband self-powered detection performance.

[0046] Further demonstrate the imaging application of the photodetector. First, an imaging system is built. A mask plate engraved with the letter "HIT" is fixed on a bracket and located in the middle position between the detector and the light source as the imaging target. Use a computer to set a program to move the imaging target in a plane to achieve the scanning of the target image, and at the same time measure the current of the detector at zero bias, which is related to the position. The light sources used include ultraviolet (367 nm), visible (520 nm), and infrared (1064 nm) light. When the light source is incident on the detector through the etched area, the measured current is larger, which is the current in the bright state; when the light source is blocked, the current is smaller, which is the dark state current. This current signal is further converted into a pixel image through computer processing, as Figure 9 shown, presenting a clear target image "HIT", which confirms that the photodetector described in the present invention has a broadband self-powered imaging function.

Claims

1. A two-dimensional bismuth / gallium arsenide heterojunction, characterized in that: The heterojunction uses gallium arsenide as a semiconductor substrate, and a two-dimensional bismuth film is covered on a partial area of ​​the substrate.

2. A two-dimensional bismuth / gallium arsenide heterojunction according to claim 1, characterized in that: The bismuth compound is bismuth selenide or bismuth telluride.

3. A photodetector comprising the two-dimensional bismuth / gallium arsenide heterojunction according to claim 1 or 2, characterized in that: Rectangular or square metal electrodes are used on the bismuth film and the surface of gallium arsenide; the two electrodes are parallelly distributed on both sides of the boundary line between the two-dimensional bismuth and gallium arsenide, and the area between the two electrodes is the light incident area.

4. A photodetector containing a two-dimensional bismuth / gallium arsenide heterojunction according to claim 3, characterized in that: The material of the metal electrode is one or two of gold, aluminum, nickel, silver, platinum or copper. The electrodes on the bismuth film and gallium arsenide are the same or different metals, respectively called symmetric electrodes and asymmetric electrodes, and the electrode thickness is 20 to 100 nm.

5. A method for preparing a two-dimensional bismuth / gallium arsenide heterojunction according to claim 1 or 2, characterized in that: The method is: Step 1: Cleaning the GaAs substrate; Step 2: Fix the mask on the gallium arsenide substrate to expose part of the gallium arsenide, fix the mask face down on the sample area at the top of the electron beam evaporation chamber, and place the bismuth evaporation target in a graphite crucible in the target area of ​​the chamber; Step 3: using electron beam evaporation equipment to prepare a bismuth oxide film on a gallium arsenide substrate; Step 4: placing the bismuth / gallium arsenide heterojunction obtained in step 3 in a quartz tube located at the heating center of the tube furnace, sealing the quartz tube and continuously introducing an inert gas, and setting the pressure inside the quartz tube to atmospheric pressure; Step 5: Annealing the bismuth / gallium arsenide heterojunction, and after the annealing is completed and the heterojunction is naturally cooled to room temperature, a bismuth / gallium arsenide heterojunction is obtained.

6. The preparation method according to claim 5, characterized in that: The step 1 is specifically as follows: ultrasonically clean the substrate with deionized water, ethanol, acetone, and isopropanol for 30 minutes in sequence, then treat the cleaned substrate with oxygen plasma for 15 minutes, and then place the substrate in a hot oven for 20 minutes to dry.

7. The preparation method according to claim 5, characterized in that: In step 3, when the electron beam evaporation device is used to prepare the bismuth film, the vacuum degree is not higher than 10 -4 Pa, the electron beam current is 0.5~1.5mA, and the evaporation rate is The time is 10 to 100 minutes.

8. The preparation method according to claim 5, characterized in that: In step 4, the inert gas is argon (Ar) gas, the gas flow rate is 20-80 sccm, and the pressure is atmospheric pressure.

9. The preparation method according to claim 5, characterized in that: In step five, the annealing treatment is performed at a temperature of 250 to 350° C. and for a time of 120 to 200 minutes.

10. A method for preparing the photoelectric detector according to claim 3 or 4, characterized in that: The method comprises: covering an electrode mask on a bismuthide / gallium arsenide heterojunction, and using an electron beam evaporation device to prepare a metal electrode for the bismuthide / gallium arsenide heterojunction; the electrode mask comprises two rectangular or square holes, which are distributed in parallel, and the electrode length and width are 10 to 400 μm, and the spacing is 50 to 500 μm, and the holes are located on the surface of the bismuthide and the gallium arsenide, respectively.

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