Preparation method and application of vibration device based on h-BN / GaN heterojunction piezoelectric sensor

Abstract

The invention provides a preparation method and application of a piezoelectric sensor vibration device based on an h-BN / GaN heterojunction, and belongs to the technical field of piezoelectric sensors, a third-generation semiconductor material gallium nitride is used as a core material of a novel piezoelectric sensor, and the piezoelectric sensor vibration device based on the h-BN / GaN heterojunction is prepared by using piezoelectric characteristics determined by inherent asymmetry of a GaN wurtzite crystal structure. The problem of heat temperature failure caused by Curie temperature limitation of conventional piezoelectric materials such as piezoelectric ceramics is solved, and meanwhile, the technical problems that a traditional piezoelectric sensor is narrow in frequency response range, poor in temperature stability and slow in dynamic response are solved by utilizing the characteristics of high forbidden bandwidth, high electron mobility and high temperature resistance of GaN. On the basis of a GaN material, an h-BN / GaN heterostructure is constructed by means of hexagonal boron nitride (h-BN), the piezoelectric effect of a strain engineering and interface collaborative polarization enhancement device is utilized, the technical problem that the piezoelectric coefficient is low when GaN is singly used for preparing a piezoelectric sensor is solved, meanwhile, the two-dimensional structural characteristic of the h-BN is utilized, the flexible piezoelectric detector can be prepared in cooperation with the GaN, and the flexible piezoelectric sensor has the advantages of being simple in structure, low in cost and the like. And light-weight and thin-film device design is realized.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric sensor technology, and in particular to a method for fabricating and applying a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor. Background Technology

[0002] With the rapid development of microelectromechanical systems (MEMS), intelligent sensing, and Internet of Things (IoT) technologies, the demand for vibration monitoring is increasing in many fields such as industrial equipment fault diagnosis, structural health monitoring, and precision manufacturing. Piezoelectric sensors, due to their advantages of simple structure, fast response speed, and no need for external power supply, have become one of the core components of vibration monitoring.

[0003] Currently, vibration monitoring mainly employs silicon-based piezoresistive and capacitive sensors, as well as traditional piezoelectric material sensors such as piezoelectric ceramics (PZT). However, with the rapid expansion of industrial applications, demands for resistance to extreme environments, high-frequency, low-amplitude vibration accuracy, and miniaturization and lightweight design are becoming increasingly apparent. Silicon-based devices suffer from weak piezoelectric performance and low sensitivity, while materials like PZT exhibit problems such as high-temperature failure during fabrication, poor detection performance for weak signals, and excessive size. With the development of third-generation semiconductor technology, GaN, with its excellent piezoelectric properties, high electron mobility, and thermal stability, has become an ideal alternative to traditional materials. GaN-based piezoelectric sensors are gradually becoming a research hotspot, but their application and promotion are still limited by their relatively weak piezoelectric conversion ratio.

[0004] Current research on GaN piezoelectric detectors mainly focuses on improving piezoelectric properties through microstructure growth and modulation. For example, the development of a fabrication process for flexible capacitive piezoelectric sensors using vertically aligned ultralong gallium nitride (GaN) lines involves embedding self-catalytic metal-organic vapor phase epitaxy (MOV) N-polar GaN lines into a PDMS matrix and then peeling them off from a sapphire substrate. This allows for effective control of the line direction and superposition of piezoelectric signals, resulting in a piezoelectric output increase from 2.9 pC / N to 5.1 pC / N. For heterostructure piezoelectric detectors, much research currently focuses on ZnO-based devices. Interface engineering is used to construct p-CuI / n-ZnO heterojunctions, effectively suppressing the piezoelectric potential shielding effect of free electrons in n-type ZnO, thus increasing the output voltage of ZnO-based piezoelectric nanogenerators from 0.8 V to 5.0 V.

[0005] Although research on improving the piezoelectric coefficient of GaN piezoelectric detectors through microstructure growth and tuning has achieved some success, the following technical shortcomings still exist: (1) The control of GaN piezoelectric properties of vertical nanowires depends heavily on the precise density and orientation control of nanowires. The mechanical stability is very weak, and the process requirements are demanding, making it difficult to promote on a large scale.

[0006] (2) Although there are studies on ZnO piezoelectric detectors, which are also wide-bandgap semiconductors, they are significantly weaker than GaN piezoelectric detectors in key dimensions such as extreme environment adaptability, high-frequency response, integration capability, and mechanical stability. Furthermore, the techniques for enhancing the piezoelectric effect through ZnO heterojunction engineering have not been effectively replicated in GaN devices. This is because conventional heterojunction combinations such as AlN / GaN suffer from severe lattice mismatch, making it impossible to guarantee efficient charge flow at the interface. At the same time, the thermal management of piezoelectric thin films still needs further improvement in high-temperature industrial applications.

[0007] (3) Currently, when GaN-based piezoelectric sensors are used for measurement in specific engineering applications, the extraction of their electrical signals still relies on a matching signal amplification circuit. The complexity of this application circuit limits its widespread use. Furthermore, the amplification circuit faces various noise interferences in high-frequency vibration industrial environments, and the accuracy of the device cannot be guaranteed. Therefore, it is necessary to design a piezoelectric sensor based on h-BN / GaN heterojunction. Summary of the Invention

[0008] The purpose of this invention is to provide a method for fabricating and applying a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor, thereby solving the technical problems existing in the background art.

[0009] This invention uses gallium nitride (GaN), a third-generation semiconductor material, as the core material of a novel piezoelectric sensor. By leveraging the piezoelectric properties determined by the inherent asymmetry of the GaN wurtzite crystal structure, it solves the thermal failure problem caused by the Curie temperature limitation of conventional piezoelectric materials such as piezoelectric ceramics (PZT). At the same time, by utilizing GaN's high bandgap, high electron mobility, and high temperature resistance, it effectively solves the technical problems of narrow frequency response range, poor temperature stability, and slow dynamic response of traditional piezoelectric sensors. Based on GaN materials, an h-BN / GaN heterostructure was constructed using hexagonal boron nitride (h-BN). By utilizing strain engineering and interface synergistic polarization to enhance the piezoelectric effect of the device, the technical challenge of low piezoelectric coefficient when using GaN alone to fabricate piezoelectric sensors was solved. At the same time, by utilizing the two-dimensional structural characteristics of h-BN, it can be combined with GaN to fabricate flexible piezoelectric detectors, realizing lightweight and thin-film device design.

[0010] Based on the microstructure of the h-BN / GaN heterostructure piezoelectric sensor, a mechanical vibration signal amplification structure consisting of an aluminum plate, two inertial mass blocks, and a frame was designed. This solves the problem of complex structure and electromagnetic interference associated with GaN-based piezoelectric sensors requiring additional circuitry to amplify their piezoelectric signals, thus improving the reliability and simplicity of the device.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for fabricating a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor, the method comprising the following steps: Step 1: Substrate selection for h-BN / GaN devices. A 4-micron-thick commercial Si-doped n-type GaN layer grown on a patterned sapphire substrate using the MOVPE method is used as the device substrate. Step 2: Pre-treat the substrate used to construct the heterojunction. The GaN layer thin film sample is ultrasonically cleaned for 20 minutes in acetone, anhydrous ethanol and deionized water. After the sample is taken out, it is dried by purging with nitrogen. The middle area of ​​the GaN surface is covered with a tungsten sheet, leaving the two sides for selective preparation of h-BN. Step 3: h-BN is prepared by PECVD. Ammonia borane is placed in a precursor preheating reactor. The sample from Step 2 is placed in the main reaction chamber. The vacuum degree of the reaction chamber is adjusted to 3.7~4.5 Pa, and the reaction temperature is set to 90~110℃. After the set reaction temperature is reached, nitrogen gas with a flow rate of 40~50 sccm is introduced to carry the precursor into the main reactor for reaction. After the reaction time is reached, the main reactor is cooled to room temperature by furnace cooling and the radio frequency device is turned off at the same time. Finally, h-BN is prepared on GaN. Step 4: Clean the prepared sample to remove reaction byproducts, place the sample in deionized water for two ultrasonic cleanings, and then perform heat annealing at 600°C under nitrogen atmosphere. Step 5: H-BN layer doping, achieved by immersion ion implantation, with the ion implantation energy set at 10 keV and the ion source being Mg. 2+ After injection, it undergoes heat annealing at 1000℃ under a nitrogen atmosphere; Step 6: Clean the substrate from Step 5, load the high-purity copper target (purity ≥ 99.99%) into the electron gun crucible, close the vacuum chamber and evacuate to 5 × 10⁻⁶. -4 Below Pa, the electron gun beam spot is calibrated and focused on the copper target surface. The beam current is controlled to evaporate the copper target. The coating thickness is monitored in real time using a quartz crystal film thickness gauge. After the preset thickness is reached, the beam current is reduced to zero, a vacuum is maintained, the gas is released to atmospheric pressure, the substrate is removed, and nitrogen-protected annealing is used to eliminate internal stress. The electrode sheet resistance and film uniformity are then tested.

[0012] Step 7: Remove the patterned sapphire substrate and use polyimide high-temperature curing adhesive to cover Au and h-BN with a PI film as a top protective layer and a temporary support structure to prevent the GaN layer from deforming or cracking in subsequent processes. Step 8: Repeat step 6 to deposit copper electrodes on the exposed GaN back side. Finally, remove the PI film, clean the surface of the aluminum plate and the surface of the flexible h-BN / GaN piezoelectric film, remove oil and impurities, and ensure that the bonding surface is flat. Apply non-conductive adhesive evenly to the central area of ​​the aluminum plate, and bond the flexible h-BN / GaN piezoelectric film along the symmetry line of the aluminum plate, ensuring that the flexible h-BN / GaN piezoelectric film completely covers the central area of ​​the aluminum plate and that the polarization direction is perpendicular to the surface of the aluminum plate. Step 9: Fabricate a mechanical vibration signal amplification structure to complete the preparation.

[0013] Furthermore, in step 1, the carrier concentration of the GaN layer is 2 × 10⁻⁶. 18 cm -3 .

[0014] Furthermore, in step 3, the purity of ammonia borane is 95%, the heating rate of the reaction temperature in the main reaction chamber is set to 10℃ / min, the reaction temperature in the main reaction chamber is set to 1000℃, the reaction time is 60min, the heating rate is set to 10℃ / min, and the RF generator is started with a power of 150W.

[0015] Furthermore, in step 8, the adhesive is cured at room temperature or under heating conditions to ensure that the flexible h-BN / GaN piezoelectric film does not slide relative to the aluminum plate and has good insulation properties, thus ultimately transferring the prepared flexible h-BN / GaN piezoelectric film device onto the aluminum plate.

[0016] Furthermore, in step 6, the specific process of cleaning the substrate is as follows: ultrasonically clean with anhydrous ethanol for 15-20 minutes to remove impurities, rinse with deionized water and dry with nitrogen, place it in a vacuum chamber substrate holder, and bombard with plasma for 5-8 minutes to enhance surface adhesion.

[0017] Further, in step 6, the electron gun is preheated until the target material glows red and is degassed for 10 minutes, the electron gun acceleration voltage is adjusted to 10-15kV, the evaporation rate is stabilized at 0.5-1nm / s, the annealing temperature is 200-300℃, and the time is 30 minutes.

[0018] Further, in step 7, the PSS substrate is removed by wet etching using a mixture of 49% hydrofluoric acid, 50% acetic acid, and 70% nitric acid in a volume ratio of 0.80:0.15:0.05 to expose the back side of the GaN layer.

[0019] Further, in step 9, the signal amplification structure is set with a "gate" shaped support frame. The top height of the two side columns is higher than the thickness of the aluminum plate. The top beam is used to fix the two ends of the aluminum plate. The left and right ends of the aluminum plate are fixed to the columns of the support frame by bolts or welding to ensure that the aluminum plate deforms only in the vertical direction when vibrating, thus limiting lateral displacement. A hole is drilled at the center of the aluminum plate, and after tapping, screws and washers are installed. Two brass mass blocks are fixed to the upper and lower surfaces of the aluminum plate by screws, ensuring that the mass blocks are symmetrically distributed and that the center of gravity coincides with the center of the aluminum plate to avoid introducing additional torque. Insulated wires are welded to the upper and lower surfaces of the h-BN / GaN piezoelectric film as signal output terminals. The wires need to be led out through the reserved holes in the support frame to avoid short circuits with the metal frame. The electrode solder joints and wire connections are insulated.

[0020] An application of an h-BN / GaN heterojunction piezoelectric sensor, characterized in that it is used for vibration signal monitoring.

[0021] Furthermore, the specific process of vibration signal monitoring is as follows: a compressive stress of 1 MPa is applied to the heterojunction piezoelectric sensor through an external mechanical device to simulate the mechanical excitation in actual work, and the open circuit voltage is recorded using a RIGOL DHO1000 oscilloscope.

[0022] The present invention, by adopting the above-described technical solution, has the following beneficial effects: (1) The h-BN of this invention has a similar hexagonal crystal structure to GaN. The growth of h-BN on GaN has good crystal structure guidance. The plasma-enhanced chemical vapor deposition method can achieve high-quality GaN / h-BN heterostructure construction without complex microstructure adjustment. The spontaneous polarization direction of h-BN and GaN along the c-axis is consistent, and net polarization enhancement is formed at the interface. At the same time, since the in-plane lattice of h-BN is slightly smaller, GaN is subjected to in-plane compressive strain. The two work together to efficiently enhance the piezoelectric effect of GaN-based piezoelectric detector.

[0023] (2) h-BN atomically flat surface (roughness <0.1nm) without dangling bonds. By growing h-BN on GaN and then peeling off its own sapphire substrate, h-BN can be used as a flexible support for the device and transferred to the deformable aluminum plate. At the same time, the ultra-high thermal conductivity of h-BN can improve the stability of the device in high temperature environment.

[0024] (3) A matching mechanical signal amplification structure is designed, consisting of a piezoelectric element, an aluminum plate, two inertial mass blocks, and a frame structure. When the vibration input is transmitted to the aluminum plate through the frame, the aluminum plate acts as a spring to mechanically amplify the signal. The inertial mass blocks, fixed along the symmetry line of the aluminum plate, further amplify the vibration, acting as another amplifier. This design effectively converts vertical input vibration into planar stress, thereby generating an electrical signal in the piezoelectric element, solving the problem of difficult signal extraction in GaN-based piezoelectric detectors, and avoiding interference problems caused by using electronic amplification circuits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the device structure of h-BN / GaN of the present invention; Figure 2 This is a process flow diagram of the device fabrication of h-BN / GaN according to the present invention; Figure 3 This is a schematic diagram of the h-BN / GaN piezoelectric detector with mechanical vibration signal amplification function of the present invention; Figure 4 This is a comparison diagram of the output voltage of the h-BN / GaN piezoelectric detector and the GaN piezoelectric detector under a compressive stress of 1 MPa. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0027] like Figure 1-3 As shown, a method for fabricating a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor is disclosed, the method comprising the following steps: Step 1: Substrate selection for the device. A 4-micrometer-thick commercial Si-doped n-type GaN layer grown on a patterned sapphire substrate (PSS) using the MOVPE method was used as the device substrate. The carrier concentration of the GaN layer was 2 × 10⁻⁶. 18 cm -3 .

[0028] Step 2: Pretreatment of the substrate used to construct the heterojunction. The GaN thin film sample was ultrasonically cleaned sequentially in acetone, anhydrous ethanol, and deionized water for 20 minutes each. After removing the sample, it was dried by purging with nitrogen for 10 minutes. The central region on the GaN surface (e.g., tungsten sheet) was then used to cover the central region. Figure 2 As shown in the figure, both sides are reserved for selective preparation of h-BN. Step 3: Preparation of h-BN via PECVD. 95% pure ammonia borane was placed in a precursor preheating reactor. The sample from Step 2 was placed in the main reaction chamber. The vacuum level in the reaction chamber was adjusted to 3.7–4.5 Pa. The reaction temperature was set to 90–110 °C, and the heating rate was set to 10 °C / min. After reaching the set reaction temperature, nitrogen gas was introduced at a flow rate of 40–50 sccm to carry the precursor into the main reactor. The main reaction chamber temperature was set to 1000 °C, the reaction time to 60 min, and the heating rate to 10 °C / min. Simultaneously, the RF generator (13.56 MHz) was started with a power of 150 W. After the reaction time was reached, the main reactor was cooled to room temperature using furnace cooling, and the RF generator was simultaneously turned off. Finally, h-BN was prepared on GaN.

[0029] Step 4: Clean the prepared sample to remove reaction byproducts. Place the sample in deionized water for two ultrasonic cleanings (10 minutes each); then perform rapid thermal annealing (RTA) at 600°C under nitrogen atmosphere.

[0030] Step 5: h-BN layer doping. Doping was achieved by immersion ion implantation, with the ion implantation energy set at 10 keV and the ion source being Mg. 2+ After injection, rapid thermal annealing at 1000℃ for 1 hour is performed under a nitrogen atmosphere.

[0031] Step 6: Clean the substrate from Step 4 using anhydrous ethanol via ultrasonic cleaning for 15-20 minutes to remove impurities. Rinse with deionized water, dry with nitrogen, and place in the vacuum chamber substrate holder. Bombard with plasma for 5-8 minutes to enhance surface adhesion. Load a high-purity copper target (purity ≥99.99%) into the electron gun crucible, close the vacuum chamber, and evacuate to 5 × 10⁻⁶. -4 Below Pa, calibrate the electron gun beam spot and focus it on the copper target surface. Preheat the electron gun until the target material is slightly red and degassed for 10 minutes. Adjust the electron gun accelerating voltage to 10-15kV, control the beam current to stabilize the copper target evaporation rate at 0.5-1nm / s, and monitor the coating thickness in real time using a quartz crystal film thickness gauge. After reaching the preset thickness (usually 100-500nm), reduce the beam current to zero and maintain vacuum for 15 minutes. Slowly release the gas to atmospheric pressure, remove the substrate, and perform nitrogen-protected annealing (200-300℃, 30 minutes) to eliminate internal stress. Check the electrode sheet resistance and film uniformity.

[0032] Step 7: Patterned Sapphire Substrate (PSS) Removal. A polyimide (PI) high-temperature curable adhesive is used to cover Au and h-BN as a top protective layer and a temporary support structure to prevent deformation or cracking of the GaN layer in subsequent processes. The PSS substrate is removed by wet etching using a mixture of hydrofluoric acid (HF, 49%), acetic acid (50%), and nitric acid (70%) in a volume ratio of 0.80:0.15:0.05, exposing the back side of the GaN layer.

[0033] Step 8: Repeat Step 6 to deposit copper electrodes on the exposed GaN back side, and finally remove the PI film. Clean the surface of the aluminum plate and the surface of the flexible h-BN / GaN piezoelectric film to remove oil and impurities, ensuring a smooth bonding surface. Apply non-conductive adhesive evenly to the central area of ​​the aluminum plate, and attach the flexible h-BN / GaN piezoelectric film along the symmetry line of the aluminum plate, ensuring that the flexible h-BN / GaN piezoelectric film completely covers the central area of ​​the aluminum plate and that the polarization direction is perpendicular to the surface of the aluminum plate. Cure the adhesive at room temperature or under heating conditions to ensure that there is no relative slippage between the flexible h-BN / GaN piezoelectric film and the aluminum plate, and that the insulation performance is good. Finally, the prepared flexible h-BN / GaN piezoelectric film device is transferred to the aluminum plate (e.g., ...). Figure 3 (As shown).

[0034] Step 9: Construct the mechanical vibration signal amplification structure. The support frame is a "gate" shaped structure, with the height of the two side columns slightly higher than the thickness of the aluminum plate, and the top beam used to fix the two ends of the aluminum plate. Fix the left and right ends of the aluminum plate to the columns of the support frame using bolts or welding, ensuring that the aluminum plate deforms only in the vertical direction (Z-axis) during vibration, limiting lateral displacement. Drill a hole at the center of the aluminum plate (above the h-BN / GaN piezoelectric film), tap it, and then install screws and washers. Fix two brass mass blocks (60 g each) to the upper and lower surfaces of the aluminum plate respectively using screws, ensuring that the mass blocks are symmetrically distributed and their centers of gravity coincide with the center of the aluminum plate to avoid introducing additional torque. Weld insulated wires to the upper and lower surfaces of the h-BN / GaN piezoelectric film as signal output terminals. The wires must be led out through the pre-drilled holes in the support frame to avoid short circuits from contact with the metal frame. Insulate the electrode solder joints and wire connections.

[0035] The detailed implementation method for device testing is as follows: A compressive stress of 1 MPa was applied to the flexible device using an external mechanical device to simulate the mechanical excitation in actual operation. The open-circuit voltage was recorded using a RIGOL DHO1000 oscilloscope. The results are as follows: Figure 4 As shown, the piezoelectric detector designed in this invention has better piezoelectric characteristics.

[0036] Matters not covered in this invention are common knowledge.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a h-BN / GaN heterojunction piezoelectric sensor vibration device, characterized by: The method comprises the following steps: Step 1: Selecting the substrate of the h-BN / GaN device, using a 4-micron-thick commercial Si-doped n-type GaN layer grown on a patterned sapphire substrate by MOVPE method as the device base; Step 2: Preprocessing the substrate for building a heterojunction, and sequentially performing ultrasonic cleaning on the GaN layer film sample in an acetone, anhydrous ethanol and deionized water environment for 20 minutes; after taking out the sample, drying treatment is performed by blowing nitrogen; the middle area on the GaN surface is covered by a tungsten sheet, and two sides are left for selective preparation of h-BN; Step 3: Preparing h-BN by PECVD, placing ammonia borane in a precursor preheating reaction furnace, and placing the sample in step 2 into a main reaction chamber; the vacuum degree of the reaction chamber is adjusted to 3.7-4.5 Pa, the reaction temperature is set to 90-110 DEG C, after reaching the set reaction temperature, nitrogen gas with a flow rate of 40-50 sccm is introduced into the main reaction furnace to react; after the reaction time reaches, the main reaction furnace is cooled to room temperature by adopting the way of furnace cooling, and at the same time, the radio frequency generator is turned off; finally, h-BN is prepared on GaN; Step 4: Cleaning the prepared sample to remove reaction byproducts, placing the sample into ionized water for twice ultrasonic cleaning, and then performing thermal annealing treatment at 600 DEG C in a nitrogen environment; Step 5: h-BN layer doping, doping is realized by means of immersion ion implantation, ion implantation energy is set to 10 keV, ion source is Mg 2+ , after implantation, heat annealing treatment at 1000°C under nitrogen atmosphere is performed; Step 6: The substrate in step 5 is cleaned, a high-purity copper target (purity ≥ 99.99%) is loaded into the electron gun crucible, the vacuum chamber is closed and vacuumed to 5 × 10 -4 Below Pa, the electron gun beam spot is calibrated to focus on the surface of the copper target, the beam current is controlled to evaporate the copper target, the coating thickness is monitored in real time by a quartz crystal film thickness gauge, after reaching the preset thickness, the beam current is first reduced to zero, the vacuum is maintained, the pressure is released to normal pressure, the substrate is taken out, nitrogen protection annealing is adopted to eliminate internal stress, and the electrode sheet resistance and film layer uniformity are detected. Step 7: Removing the patterned sapphire substrate, using polyimide high-temperature curing glue to cover the PI film to Au and h-BN as a top protective layer, and at the same time as a temporary support structure, preventing the GaN layer from deforming or breaking in the subsequent process; Step 8: Repeating step 6, evaporating a copper electrode on the exposed GaN back surface, and finally removing the PI film, cleaning the surface of the aluminum plate and the surface of the flexible h-BN / GaN piezoelectric film piece, removing oil stains and impurities, ensuring that the sticking surface is flat, uniformly coating non-conductive glue in the center area of the aluminum plate, and sticking the flexible h-BN / GaN piezoelectric film piece along the symmetry line of the aluminum plate, ensuring that the flexible h-BN / GaN piezoelectric film piece completely covers the center area of the aluminum plate, and the polarization direction is perpendicular to the surface of the aluminum plate; Step 9: Making a mechanical vibration signal amplification structure, and completing the preparation.

2. The preparation method of a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 1, the GaN layer carrier concentration is 2 x 1018cm-3 18 cm -3 -3.

3. The preparation method of a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 3, the purity of ammonia borane is 95%, the reaction temperature in the main reaction chamber is set to 1000 DEG C at a heating rate of 10 DEG C / min, the reaction time is 60 min, the heating rate is set to 10 DEG C / min, and the radio frequency generator is started at a power of 150 W.

4. The preparation method of a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 8, the glue is cured at room temperature or under heating conditions to ensure that the flexible h-BN / GaN piezoelectric film piece and the aluminum plate do not slide relative to each other, and the insulation performance is good, and finally the prepared flexible h-BN / GaN piezoelectric film device is transferred to the aluminum plate.

5. The preparation method of a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 6, the specific process of cleaning the substrate is to remove impurities by ultrasonic cleaning with anhydrous ethanol for 15-20 min, to blow dry with nitrogen after deionized water washing, to place into a vacuum chamber substrate holder, and to enhance surface adhesion by plasma bombardment for 5-8 min.

6. The preparation method of a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 6, the electron gun is preheated to the target red outgassing for 10 min, the electron gun acceleration voltage is adjusted to 10-15 kV, the evaporation rate is stabilized at 0.5-1 nm / s, the annealing temperature is 200-300℃, and the time is 30 min.

7. The method for fabricating a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 7, the PSS substrate is removed by using 49% hydrofluoric acid, 50% acetic acid, and 70% nitric acid as a mixed etchant in a volume ratio of 0.80:0.15:0.05 to expose the back of the GaN layer.

8. The method for fabricating a vibration device based on an h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: In step 9, the signal amplification structure is set as a "door" type structure, the top of the two side columns is higher than the thickness of the aluminum plate, the top beam is used to fix the two ends of the aluminum plate, the left and right ends of the aluminum plate are fixed to the columns of the support frame by bolts or welding, ensuring that the aluminum plate only deforms vertically when vibrating, limiting lateral displacement, a hole is drilled in the center of the aluminum plate, and a screw and a washer are installed after tapping, two brass masses are fixed on the upper and lower surfaces of the aluminum plate by screws, ensuring that the masses are symmetrically distributed, the center of gravity coincides with the center of the aluminum plate, and no additional torque is introduced, insulating wires are welded on the upper and lower surfaces of the h-BN / GaN piezoelectric film sheet as signal output terminals, the wires need to be led out through the reserved holes of the support frame to avoid short circuit with the metal frame, and the electrode welding point and the wire connection are insulated.

9. The application of a h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: The vibration signal is monitored.

10. The application of a h-BN / GaN heterojunction piezoelectric sensor according to claim 1, characterized in that: The specific process of vibration signal monitoring is as follows: an external mechanical device is used to apply a compression stress of 1 MPa to the heterojunction piezoelectric sensor to simulate the mechanical excitation in actual work, and an RIGOL DHO1000 oscilloscope is used to record the open circuit voltage.

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