Heterojunction photoelectric detector and preparation method thereof

Abstract

The heterojunction photoelectric detector comprises a substrate, a gallium nitride layer is arranged on the surface of the substrate, a perovskite layer and an electrode are sequentially arranged on the surface of one side of the gallium nitride layer, and an electrode is arranged on the surface of the other side of the gallium nitride layer; and the perovskite layer is a (PEA) 2PbI4 layer. The preparation method comprises the following steps: growing a gallium nitride layer on a substrate through an MOCVD (Metal Organic Chemical Vapor Deposition) method; controlling an area for spin coating of a (PEA) 2PbI4 precursor solution on the gallium nitride layer by using a heat release adhesive tape; carrying out spin coating of a PEA 2PbI4 precursor solution on the gallium nitride layer through a one-step spin coating method, and carrying out annealing treatment to form a perovskite layer so as to obtain a heterojunction surface; and evaporating an electrode on the surface of the heterojunction. Compared with a traditional ultraviolet photoelectric detector, the spectrum response range is wide because the response wavelength of the two-dimensional perovskite can reach about 510 nm; compared with a three-dimensional perovskite heterojunction photoelectric detector, the three-dimensional perovskite heterojunction photoelectric detector has the advantages of being short in response time and the like.

Description

Technical Field

[0001] The present invention relates to a photoelectric detector and a manufacturing method thereof, and in particular to a heterojunction photoelectric detector and a manufacturing method thereof. Background Art

[0002] The two-dimensional perovskite material (PEA) 2PbI4 exhibits efficient light absorption ability, especially with a significant absorption peak in the band corresponding to its band gap. This property can significantly improve the response sensitivity of photodetectors to light signals in a specific band. Its layered structure enhances the Coulomb interaction between electrons and holes, allowing excitons to exist stably at room temperature, thereby improving the light absorption efficiency. By changing the organic ligands, inorganic layer thickness or chemical composition, the band gap of the two-dimensional perovskite can be precisely controlled over a wide range. This adjustable property allows the working band of the photodetector to be designed according to specific needs, such as ultraviolet, visible or near-infrared bands. Two-dimensional perovskite materials can be prepared into high-quality films through simple processes such as low-temperature solution method and spin coating method, which has a significant advantage in reducing production costs.

[0003] Gallium nitride (GaN) is a typical wide bandgap semiconductor material. With its excellent optoelectronic properties, it has become one of the core materials for high-performance photodetectors. The bandgap width of GaN is 3.4eV, which gives it unique optical and electrical properties. It has strong chemical bond binding energy, high thermal conductivity, excellent thermal stability and radiation resistance, and still shows good performance in photoelectric detection under harsh environments. It can be grown on a variety of substrates such as silicon, sapphire and silicon carbide, which is compatible with existing optoelectronic device processes. GaN photodetectors have irreplaceable advantages, and their potential in multi-band detection and new heterojunction device design in the future deserves further exploration.

[0004] Existing perovskite photodetectors have low response speed and sensitivity, especially at high frequencies or low light intensities. At the same time, many perovskite-based photodetectors have problems with poor band docking, resulting in low carrier transfer efficiency, which in turn affects the performance of the detector. In particular, perovskite materials may degrade during operation, resulting in reduced device performance. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a heterojunction photodetector with fast response time, wide spectral response range and stable performance. Another purpose of the present invention is to provide a method for preparing a heterojunction photodetector with simple process, low cost and readily available raw materials.

[0006] Technical solution: A heterojunction photodetector described in the present invention includes a substrate, a gallium nitride layer is arranged on the surface of the substrate, a perovskite layer and an electrode are arranged in sequence on one side surface of the gallium nitride layer, and an electrode is arranged on the other side surface; the perovskite layer is a (PEA)2PbI4 layer.

[0007] Further, the electrode is made of Ag or In.

[0008] Furthermore, the substrate is a sapphire substrate.

[0009] Furthermore, the thickness of the substrate is 400-450 μm, the thickness of the gallium nitride layer is 4-5 μm, the thickness of the perovskite layer is 495-505 nm, and the thickness of the electrode is 99-101 nm.

[0010] A method for preparing a heterojunction photodetector according to the present invention comprises the following steps:

[0011] S1, growing a gallium nitride layer on a substrate by MOCVD method;

[0012] S. Use a thermal release tape to control the area on the gallium nitride layer for spin coating (PEA) 2PbI4 precursor solution;

[0013] S3, spin coating a (PEA)2PbI4 precursor solution on the gallium nitride layer by a one-step spin coating method, annealing, forming a perovskite layer, and obtaining a heterojunction surface;

[0014] S4. Vapor deposit an electrode on the surface of the heterojunction to obtain a heterojunction photodetector.

[0015] Furthermore, in step S1, the substrate is cleaned with a cleaning agent, deionized water, acetone and anhydrous ethanol in sequence, then dried, and then subjected to ultraviolet irradiation, which is beneficial to increasing the wettability of the surface of the quartz glass substrate and removing organic and inorganic impurities. The gallium nitride layer is specifically grown by evacuating the vacuum, introducing ammonia, trimethyl gallium, and carrier gas, growing a 20-50nm buffer layer at 500-600°C, and then raising the temperature to 1000-1100°C to grow the gallium nitride layer to 4-5μm.

[0016] Furthermore, in step S2, before using the thermal release tape, the gallium nitride layer is ultrasonically cleaned with deionized water, acetone, and anhydrous ethanol in sequence, and then blown dry with nitrogen.

[0017] Further, in step S3, the preparation method of the (PEA)2PbI4 precursor solution is: PbI2 powder and PEAI powder with a molar ratio of 1:2 are weighed respectively, mixed with DMF, heated and stirred at 65-75°C in a nitrogen atmosphere until completely dissolved, and then filtered with PTFE to obtain a (PEA)2PbI4 precursor solution. The rotation speed of the spin coating (PEA)2PbI4 precursor solution is 2000rpm, the spin coating time is 30s, the annealing temperature is 90-100°C, and the annealing time is 15-20min.

[0018] Working principle: By forming a heterojunction interface between (PEA)2PbI4 and the GaN layer, the high exciton binding energy of (PEA)2PbI4 and the high mobility of GaN are combined to significantly enhance the separation and transmission efficiency of photogenerated carriers, thereby achieving high-sensitivity photodetection in the ultraviolet to visible light range. In this structure, the two-dimensional perovskite material (PEA)2PbI4 can efficiently absorb photons in the visible light band and generate stable exciton states due to its band gap tunability and high light absorption coefficient. The GaN layer has a wide band gap characteristic, which can selectively absorb ultraviolet light and provide a high-speed transmission channel for photogenerated carriers. By constructing a heterojunction interface between (PEA)2PbI4 and GaN, photogenerated electrons and holes can be separated quickly, reducing recombination losses and improving photoelectric conversion efficiency. More importantly, this structure also significantly improves the response speed and signal-to-noise ratio of the photodetector through the built-in electric field in the heterojunction interface. Thanks to the high absorption characteristics of (PEA)2PbI4 materials and the excellent electrical properties of GaN, the detector can achieve a wide spectral response in the ultraviolet and visible light ranges and maintain high detection sensitivity under weak light conditions. This photodetector based on the (PEA)2PbI4 / GaN heterojunction has broad application prospects in the field of optoelectronic devices, especially in weak light imaging, high-speed optical communications, and multi-band photodetection. At the same time, the low-cost preparation process of (PEA)2PbI4 materials combined with the high-temperature stability of GaN ensures low energy consumption and long-term stability of the device. By combining the advantages of (PEA)2PbI4 and GaN, the photodetector fully realizes the photoelectric detection function of high sensitivity, wide spectrum, and high stability, providing a new technical solution for the development of the optoelectronic field.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. Compared with traditional ultraviolet photodetectors, the spectral response range is wider because the response wavelength of two-dimensional perovskite can reach about 510nm;

[0021] 2. Compared with the three-dimensional perovskite heterojunction photodetector, the present invention has the characteristics of high responsiveness;

[0022] 3. The preparation method of the two-dimensional perovskite heterojunction proposed in the present invention has the advantages of simple process, low cost, and raw materials are all readily available commercial products, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the present invention;

[0024] Figure 2 is a SEM cross-sectional view of the present invention;

[0025] Figure 3 is the XRD pattern of the present invention;

[0026] Figure 4 It is the absorption spectra of GaN film, (PEA)2PbI4 film and (PEA)2PbI4 / GaN heterojunction;

[0027] Figure 5 is an IV diagram of the heterojunction photodetector of the present invention;

[0028] Figure 6 1 is an IT diagram of the heterojunction photodetector of the present invention, wherein (a) is a light response diagram under forward bias, and (b) is a light response diagram under reverse bias;

[0029] Figure 7 is an IT diagram of the heterojunction photodetector of the present invention at 0 bias voltage;

[0030] Figure 8 1 is a response speed diagram of the heterojunction photodetector of the present invention, wherein (a) is a response diagram under a bias voltage of +5 V, and (b) is a response diagram under a bias voltage of -5 V. DETAILED DESCRIPTION

[0031] In the following embodiments, the (PEA)2PbI4 precursor solution is obtained according to the following preparation steps:

[0032] Step 1: Use an electronic balance to weigh PbI2 powder (115.3 mg) and PEAI powder (124.5 mg) in a molar ratio of 1:2 and slowly pour them into a glass bottle. Then add 1 mL of DMF organic solvent and heat and stir on a heating table at 70 °C in a nitrogen atmosphere for 12 h until completely dissolved.

[0033] Step 2: Filter the completely dissolved solution with 0.35 μm PTFE to obtain a (PEA)2PbI4 precursor solution.

[0034] Example 1

[0035] A method for preparing a heterojunction photodetector based on (PEA)2PbI4 / GaN comprises the following steps:

[0036] S1. Sapphire substrate 1 treatment: in an ultrasonic cleaning apparatus, cleaning agent, deionized water, acetone and anhydrous ethanol are used in sequence to clean the substrate 1 for 20 minutes, then the substrate is placed in a drying oven at 100° C. for drying, and then the surface of the dried quartz glass substrate 1 is irradiated with ultraviolet light for 15 minutes using a UV light cleaning machine. The purpose of this step is to increase the wettability of the surface of the quartz glass substrate 1 and remove organic and inorganic impurities.

[0037] S2. Place the cleaned sapphire substrate 1 in the MOCVD system and carefully place the sapphire substrate 1 on the substrate carrier using dust-free tweezers (make sure the polished surface faces upward). Adjust the position of the substrate 1 to center it to ensure uniform gas flow. Use a high vacuum pump to evacuate the chamber to a base vacuum state (usually within 10 -5 Torr), set the temperature to 500°C to grow a low-temperature buffer layer. Introduce ammonia (NH3, as a nitrogen source) and trimethylgallium (TMGa, as a gallium source) into the reaction chamber, with hydrogen or nitrogen as a carrier gas. Maintain low-temperature growth conditions for about a few minutes to ten minutes to ensure uniform growth of the buffer layer, usually with a thickness of 20nm. Raise the temperature to 1000°C for the growth of high-quality GaN films. Increase the flow of ammonia and trimethylgallium, and continue deposition at high temperature to ensure that the gallium nitride layer 2 grows to 4.5μm.

[0038] S3. After the growth is completed, take out the sample and perform pretreatment before spin coating again: use deionized water, acetone and anhydrous ethanol to clean it in an ultrasonic cleaner for 5 minutes, then blow it dry with nitrogen, and then use thermal release tape to frame a 1×1 cm 2 area to ensure the consistency of sample performance each time.

[0039] S4, the product obtained in step S3 is transferred and placed in the center of the stage of the coating machine, and the (PEA)2PbI4 precursor solution is dropped at the center, and the (PEA)2PbI4 precursor solution is spin-coated at a high speed of 2000 rpm for 30 seconds to spread evenly. During the high-speed rotation of the coating machine to form a film, it is then annealed on a heating table at 100°C for 15 minutes to form a perovskite layer 3, which is a (PEA)2PbI4 layer.

[0040] S5. On the perovskite layer 3, a Ag electrode 4 is deposited by thermal evaporation, and finally a (PEA)2PbI4 / GaN heterojunction photodetector is obtained.

[0041] like Figure 1As shown, the heterojunction photodetector obtained in this embodiment includes a sapphire substrate 1, a gallium nitride layer 2, a perovskite layer 3 and a silver electrode layer 4. The heterojunction photodetector uses the built-in electric field formed by (PEA)2PbI4 / GaN, and with the help of the diffusion and migration of photogenerated carriers, forms a current-voltage curve similar to that of a diode. Due to the quantum tunneling phenomenon, a small current will also pass through the reverse bias, so there can be an effective photoelectric response regardless of the positive or negative external bias, which expands the direction of its device utilization. The response spectrum range of the detector can be from (300nm-510nm), realizing a wide-spectrum ultraviolet detector, and when the bias voltage is zero, self-driven detection can be achieved. In addition, its response time is faster than that of a three-dimensional perovskite heterojunction. Because it has the characteristics of wide band, self-drive, and fast response, the (PEA)2PbI4 / GaN heterojunction photodetector has great application prospects in high-performance detection.

[0042] like Figure 2 As shown, (PEA)2PbI4 is uniformly formed on the gallium nitride layer 2.

[0043] like Figure 3 As shown in the figure, the XRD phase diagrams of (PEA)2PbI4, GaN and (PEA)2PbI4 / GaN heterojunction all show diffraction peaks. There are no diffraction peaks of other substances in the diffraction diagram, indicating that (PEA)2PbI4 and GaN have good crystallization performance and high purity, and the (PEA)2PbI4 / GaN heterojunction contains the diffraction peaks of the first two crystals, and the film quality is high.

[0044] like Figure 4 As shown in the figure, the absorption spectra of the heterojunction of (PEA)2PbI4, GaN and (PEA)2PbI4 / GaN. The perovskite layer 3 and the gallium nitride layer 2 show two obvious absorption peaks in the visible light and ultraviolet bands, which just correspond to the energy bands of the two. The heterojunction of (PEA)2PbI4 / GaN has absorption peaks in both visible light and ultraviolet, indicating that the heterojunction of the two is well formed.

[0045] like Figure 5 As shown, the detector obtained in this embodiment exhibits bidirectional current in both positive and negative directions, showing a significant diode effect. However, under reverse voltage, a small current still passes through, indicating a quantum tunneling phenomenon.

[0046] like Figure 6 As shown in the figure, the detection rate of the detector obtained in this embodiment can reach 8.71×10 10 mA / W, the response can reach 1390mA / W.

[0047] like Figure 7As shown in the figure, the switch test results of the detector obtained in this embodiment under 0V bias and multiple light powers indicate that even if the light intensity is small (0.5mW / cm 2 ), a relatively stable switching response can still be achieved.

[0048] like Figure 8 As shown, the detector obtained in this embodiment is biased at ±5V, and its 2 The response speed diagram under illumination shows that under -5V bias, the response speed is 0.13s / 0.18s, which is faster than the forward bias and has a more stable waveform. This is because, in the forward photoconductive mode, the forward bias accelerates the collection of carriers, but also increases the concentration of carriers, resulting in a higher recombination rate and a lower photocurrent response speed. In contrast, the thicker depletion region in the reverse depletion mode reduces carrier recombination, and although the photocurrent is lower, the overall response is more stable. Under 0V bias, the detector still exhibits a stable self-driven signal and has a faster response time (46.9ms / 55.9ms).

[0049] Example 2

[0050] A method for preparing a heterojunction photodetector based on (PEA)2PbI4 / GaN comprises the following steps:

[0051] S1. Sapphire substrate 1 treatment: in an ultrasonic cleaning apparatus, cleaning agent, deionized water, acetone and anhydrous ethanol are used in sequence to clean the substrate 1 for 20 minutes, then the substrate is placed in a drying oven at 100° C. for drying, and then the surface of the dried quartz glass substrate 1 is irradiated with ultraviolet light for 15 minutes using a UV light cleaning machine. The purpose of this step is to increase the wettability of the surface of the quartz glass substrate 1 and remove organic and inorganic impurities.

[0052] S2. Place the cleaned sapphire substrate 1 in the MOCVD system and carefully place the sapphire substrate 1 on the substrate carrier using dust-free tweezers (make sure the polished surface faces upward). Adjust the position of the substrate 1 to center it to ensure uniform gas flow. Use a high vacuum pump to evacuate the chamber to a base vacuum state (usually within 10 -5 Torr), set the temperature to 500°C to grow a low-temperature buffer layer. Introduce ammonia (NH3, as a nitrogen source) and trimethylgallium (TMGa, as a gallium source) into the reaction chamber, with hydrogen or nitrogen as a carrier gas. Maintain low-temperature growth conditions for about a few minutes to ten minutes to ensure uniform growth of the buffer layer, usually with a thickness of 20nm. Raise the temperature to 1000°C for the growth of high-quality GaN films. Increase the flow of ammonia and trimethylgallium, and continue deposition at high temperature to ensure that the gallium nitride layer 2 grows to 4μm.

[0053] S3. After the growth is completed, take out the sample and perform pretreatment before spin coating again: use deionized water, acetone and anhydrous ethanol to clean it in an ultrasonic cleaner for 5 minutes, then blow it dry with nitrogen, and then use thermal release tape to frame a 1×1 cm 2 area to ensure the consistency of sample performance each time.

[0054] S4, the product obtained in step S3 is transferred and placed in the center of the stage of the coating machine, and the (PEA)2PbI4 precursor solution is dropped at the center, and the (PEA)2PbI4 precursor solution is spin-coated at a high speed of 2000 rpm for 30 seconds to spread evenly. During the process of high-speed rotation of the coating machine to form a film, it is then annealed on a 90°C heating table for 20 minutes to form a perovskite layer 3, which is a (PEA)2PbI4 layer.

[0055] S5. On the perovskite layer 3, an In electrode 4 is deposited by thermal evaporation, and finally a (PEA)2PbI4 / GaN heterojunction photodetector is obtained.

[0056] Example 3

[0057] A method for preparing a heterojunction photodetector based on (PEA)2PbI4 / GaN comprises the following steps:

[0058] S1. Sapphire substrate 1 treatment: in an ultrasonic cleaning apparatus, cleaning agent, deionized water, acetone and anhydrous ethanol are used in sequence to clean the substrate 1 for 20 minutes, then the substrate is placed in a drying oven at 100° C. for drying, and then the surface of the dried quartz glass substrate 1 is irradiated with ultraviolet light for 15 minutes using a UV light cleaning machine. The purpose of this step is to increase the wettability of the surface of the quartz glass substrate 1 and remove organic and inorganic impurities.

[0059] S2. Place the cleaned sapphire substrate 1 in the MOCVD system and carefully place the sapphire substrate 1 on the substrate carrier using dust-free tweezers (make sure the polished surface faces upward). Adjust the position of the substrate 1 to center it to ensure uniform gas flow. Use a high vacuum pump to evacuate the chamber to a base vacuum state (usually within 10 -5 Torr), set the temperature to 600℃ to grow a low-temperature buffer layer. Introduce ammonia (NH3, as a nitrogen source) and trimethylgallium (TMGa, as a gallium source) into the reaction chamber, with hydrogen or nitrogen as a carrier gas. Maintain low-temperature growth conditions for about a few minutes to ten minutes to ensure uniform growth of the buffer layer, usually with a thickness of 50nm. Raise the temperature to 1100℃ for the growth of high-quality GaN films. Increase the flow of ammonia and trimethylgallium, and continue deposition at high temperature to ensure that the gallium nitride layer 2 grows to 5μm.

[0060] S3. After the growth is completed, take out the sample and perform pretreatment before spin coating again: use deionized water, acetone and anhydrous ethanol to clean it in an ultrasonic cleaner for 5 minutes, then blow it dry with nitrogen, and then use thermal release tape to frame a 1×1 cm 2 area to ensure the consistency of sample performance each time.

[0061] S4, the product obtained in step S3 is transferred and placed in the center of the stage of the coating machine, and the (PEA)2PbI4 precursor solution is dropped at the center, and the (PEA)2PbI4 precursor solution is spin-coated at a high speed of 2000 rpm for 30 seconds to spread evenly. During the high-speed rotation of the coating machine to form a film, it is then annealed on a 95°C heating table for 18 minutes to form a perovskite layer 3, which is a (PEA)2PbI4 layer.

[0062] S5. On the perovskite layer 3, an In electrode 4 is deposited by thermal evaporation, and finally a (PEA)2PbI4 / GaN heterojunction photodetector is obtained.

[0063] Comparative Example 1

[0064] The steps of this comparative example are the same as those of Example 1, except that the gallium nitride layer 2 is replaced with gallium oxide, and step S2 is replaced with: Place the cleaned sapphire substrate 1 in the MOCVD system, and carefully place the sapphire substrate 1 on the substrate carrier using dust-free tweezers (make sure the polished surface faces upward). Adjust the position of the substrate 1 to center it to ensure uniform gas flow. Use a high vacuum pump to evacuate the chamber to a base vacuum state (usually at 10 -5 Torr), set the temperature to 750°C, introduce oxygen (O2, as oxygen source) and trimethyl gallium (TMGa, as gallium source) into the reaction chamber, and use hydrogen or nitrogen as carrier gas. Continue deposition at high temperature to ensure that the gallium oxide layer 2 grows to 5μm. Perform a photoelectric response test and find that its responsivity is 2.5mA / W.

[0065] Comparative Example 2

[0066] This comparative example is the same as Example 1 in steps, except that the CH3NH3PbI3 precursor solution is replaced by CH3NH3PbI3, and step S4 is replaced by: the product of step S3 is transferred and placed in the center of the stage of the glue spreader, and the (PEA)2PbI4 precursor solution is dropped at the center, and the CH3NH3PbI3 precursor solution is spin-coated at a high speed of 2000rpm for 30s and spread evenly. During the high-speed rotation of the glue spreader to form a film, it is then annealed on a 100°C heating table for 15 minutes to form a perovskite layer 3, which is a (PEA)2PbI4 layer. A photoelectric response test was conducted, and it was found that its responsivity was 37mA / W.

[0067] Comparative Example 3

[0068] This comparative example is the same as Example 1 in steps, except that step S2 is replaced by: the product of step S3 is transferred and placed in the center of the stage of the coating machine, and the (PEA)2PbI4 precursor solution is dropped at the center, and the (PEA)2PbI4 precursor solution is spin-coated at a high speed of 2000 rpm for 25s or 35s, and spread evenly. During the high-speed rotation of the coating machine to form a film, it is then annealed on a heating table at 100°C for 15 minutes to form a perovskite layer 3, which is a (PEA)2PbI4 layer. The photoelectric response test was carried out, and the results showed that the responsivities were 1112mA / W and 834mA / W, respectively.

Claims

1. A heterojunction photodetector, characterized in that: The invention comprises a substrate (1), wherein a gallium nitride layer (2) is arranged on the surface of the substrate (1), a perovskite layer (3) and an electrode (4) are arranged in sequence on one side surface of the gallium nitride layer (2), and an electrode (4) is arranged on the other side surface; the perovskite layer (3) is a (PEA)2PbI4 layer.

2. The heterojunction photodetector according to claim 1, characterized in that: The electrode (4) is made of Ag or In.

3. The heterojunction photodetector according to claim 1, characterized in that: The substrate (1) is a sapphire substrate (1).

4. The heterojunction photodetector according to claim 1, characterized in that: The thickness of the substrate (1) is 400-450 μm, the thickness of the gallium nitride layer (2) is 4-5 μm, the thickness of the perovskite layer (3) is 495-505 nm, and the thickness of the electrode (4) is 99-101 nm.

5. A method for preparing a heterojunction photodetector, characterized in that: The following steps are involved: S1, growing a gallium nitride layer (2) on a substrate (1) by MOCVD; S2, using a thermal release tape to control an area on the gallium nitride layer (2) for spin coating (PEA) 2PbI4 precursor solution; S3, spin coating a (PEA)2PbI4 precursor solution on the gallium nitride layer (2) by a one-step spin coating method, annealing, forming a perovskite layer (3), and obtaining a heterojunction surface; S4, evaporating an electrode (4) on the surface of the heterojunction to obtain a heterojunction photodetector.

6. The method for preparing a heterojunction photodetector according to claim 5, characterized in that: In the step S1, the substrate (1) is cleaned with a cleaning agent, deionized water, acetone and anhydrous ethanol in sequence, then dried, and then subjected to ultraviolet irradiation.

7. The method for preparing a heterojunction photodetector according to claim 5, characterized in that: In the step S1, the gallium nitride layer (2) is grown by evacuating the air, introducing ammonia, trimethyl gallium and carrier gas, growing a buffer layer of 20 to 50 nm at 500 to 600° C., and then raising the temperature to 1000 to 1100° C. to grow the gallium nitride layer (2) to 4 to 5 μm.

8. The method for preparing a heterojunction photodetector according to claim 5, characterized in that: In the step S2, before using the thermal release tape, the gallium nitride layer (2) is ultrasonically cleaned using deionized water, acetone, and anhydrous ethanol in sequence, and then blown dry with nitrogen.

9. The method for preparing a heterojunction photodetector according to claim 5, characterized in that: In step S3, the preparation method of the (PEA)2PbI4 precursor solution is: PbI2 powder and PEAI powder in a molar ratio of 1:2 are weighed respectively, mixed with DMF, heated and stirred at 65-75°C in a nitrogen atmosphere until completely dissolved, and then filtered with PTFE to obtain a (PEA)2PbI4 precursor solution.

10. The method for preparing a heterojunction photodetector according to claim 5, characterized in that: In the step S3, the rotation speed of spin coating (PEA) 2PbI4 precursor solution is 2000 rpm, the spin coating time is 30 s, the annealing temperature is 90-100° C., and the annealing time is 15-20 min.

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