Preparation method of heterojunction device and heterojunction device

Abstract

The preparation method of the heterojunction device comprises the steps that a boron nitride thin film is prepared with ammonia borane as a precursor, then a gallium nitride layer grows on the boron nitride thin film to form a heterojunction structure, and the ratio of the usage amount of the ammonia borane to the area of a substrate is 150 mg / cm < 2 > to 250 mg / cm < 2 >. According to the preparation method provided by the embodiment of the invention, a high-quality BN-GaN heterojunction neutron device can be provided, and a foundation is laid for research, development and application of a novel neutron detector for replacing a 3He tube. Ammonia borane is non-toxic, non-flammable and non-explosive at normal temperature, is stable and easy to store, has a stoichiometric ratio of B / N of 1: 1, is relatively low in decomposition temperature and pollution-free in decomposition product, can be used as a boron source and a nitrogen source, and is a single precursor. The quality of the heterojunction device is guaranteed, the production cost is reduced, and the heterojunction device has the advantages of simple structure, relatively small size, good linear range, short response time, easy n / gamma discrimination, high detection efficiency and the like.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of semiconductor detectors, and in particular, to a method for preparing a heterojunction device and a heterojunction device. Background Art

[0002] As one of the important basic particles that make up the atomic nucleus of matter, neutrons are electrically neutral. The development of neutron detection technology is crucial for fields such as core neutron fluence rate monitoring, nuclear power plant radiation safety monitoring, environmental monitoring, nuclear fuel detection, nuclear explosion detection, accelerator operating sites, aerospace, and space physics. An ideal neutron detector should have the following characteristics: (1) a flat energy response curve; (2) insensitivity to gamma-ray interference; (3) high sensitivity; (4) good radiation resistance of the detector; (5) fast response speed. Existing neutron detectors include track detectors, gas detectors, scintillator detectors, semiconductor detectors, etc. Currently, the widely used neutron detection internationally has problems such as low sensitivity, narrow measurement range, poor n-γ discrimination ability, short lifespan of neutron conversion materials, high dependence on environmental conditions, and high equipment cost. In recent years, each nuclear power has invested a large amount of resources in researching new neutron detectors that are cheap, lightweight, easy to manufacture, small in size, and high in detection efficiency, mainly focusing on research in new neutron conversion materials, new scintillators, new detector principles and structures, etc.

[0003] Compared with traditional neutron detectors, semiconductor neutron detectors have many advantages such as simple structure, relatively small volume, good linear range, short response time, easy n / γ discrimination, and high detection efficiency, and belong to emerging technologies that are key development areas for various countries. The remarkable feature of semiconductor neutron detectors is that they take semiconductor devices as the core, and the performance of the detector depends on the semiconductor device structure and the properties of the semiconductor materials used in the device. Neutron detectors made of traditional semiconductor materials perform well in general environments, but in high-temperature and strong-radiation environments, the detector performance will deteriorate and it cannot work stably and reliably for a long time. Moreover, most of the heterojunction devices in traditional technologies rely on boron powder, resulting in an increase in the cost of heterojunction devices. Therefore, preparing neutron detector semiconductor materials suitable for actual working conditions, exploring new sensing principles, and studying the manufacturing process of semiconductor neutron detectors are the technical keys to developing high-quality semiconductor neutron detectors. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0005] To this end, in the first aspect of the present invention, a method for preparing a heterojunction device is provided.

[0006] In the second aspect of the present invention, a heterojunction device is provided.

[0007] In view of this, according to a first aspect of an embodiment of the present application, a method for preparing a heterojunction device is proposed, comprising:

[0008] Boron nitride thin films were prepared using ammonia borane as a precursor;

[0009] growing a gallium nitride layer on the boron nitride film to form a heterojunction structure;

[0010] Etching the heterojunction structure and preparing an electrode layer to obtain a heterojunction device;

[0011] The ratio of the amount of ammonia borane to the area of the substrate is 150 mg / cm 2 Up to 250mg / cm 2 .

[0012] In a feasible embodiment, the step of preparing a boron nitride film using ammonia borane as a precursor includes:

[0013] providing a substrate and cleaning the substrate;

[0014] Weighing ammonia borane, and placing the substrate and the ammonia borane in a chemical vapor deposition system;

[0015] Repeating the steps of evacuating the chemical vapor deposition system and introducing an inert gas until the air in the chemical vapor deposition system is exhausted;

[0016] introducing nitrogen into the chemical vapor deposition system and heating the system to a growth temperature;

[0017] The boron nitride film is prepared by deposition on the substrate based on the ammonia borane.

[0018] In a feasible embodiment, the step of depositing the boron nitride film on the substrate based on the ammonia borane includes:

[0019] After the chemical vapor deposition system is heated to a growth temperature, annealing is performed to prepare the boron nitride film on the substrate;

[0020] The growth temperature is 1200°C to 1300°C.

[0021] In a feasible implementation manner, the substrate is a sapphire substrate with a thickness of 400 μm to 450 μm.

[0022] In a feasible embodiment, the step of growing a gallium nitride layer on the boron nitride film to form a heterojunction structure includes:

[0023] A gallium nitride layer is grown on the boron nitride film by a metal organic compound chemical vapor deposition process to form a heterojunction structure.

[0024] In a feasible implementation, the step of growing a gallium nitride layer on a boron nitride thin film by metal-organic chemical vapor deposition to form a heterojunction structure includes:

[0025] Clean the reaction furnace chamber and the tray;

[0026] Vacuum the reaction chamber to remove the air in the reaction chamber;

[0027] Heat the reaction chamber. When the heating temperature reaches the preset temperature, introduce hydrogen and ammonia into the reaction chamber to nitride the surface of the boron nitride thin film substrate to form an aluminum nitride nucleation layer;

[0028] Stop introducing hydrogen, keep introducing ammonia, and simultaneously introduce trimethylgallium and silane to grow a gallium nitride layer on the boron nitride thin film.

[0029] In a feasible implementation, the step of cleaning the reaction furnace chamber and the tray includes:

[0030] Dust the reaction furnace chamber;

[0031] Heat the reaction furnace chamber to the cleaning temperature, and simultaneously introduce a cleaning gas to bake the reaction furnace chamber and the tray;

[0032] Clean the tray with a cleaning liquid, and then dry the tray.

[0033] In a feasible implementation, the step of etching the heterojunction structure and preparing an electrode layer to obtain a heterojunction device includes:

[0034] Clean the surface of the epitaxial wafer of the heterojunction structure;

[0035] Etch the heterojunction structure to form an electrode pattern;

[0036] Prepare an ohmic contact electrode and an insulating layer based on the electrode pattern to obtain the heterojunction device.

[0037] In a feasible implementation, the method for preparing a heterojunction device further includes:

[0038] Provide a packaging shell and package the heterojunction device in the packaging shell;

[0039] Wherein, the electrodes of the heterojunction device are connected to the pins of the packaging shell.

[0040] According to a second aspect of the embodiments of the present application, a heterojunction device is proposed. The heterojunction device is prepared by the preparation method of the heterojunction device described in any of the above technical solutions.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] In the preparation method of the heterojunction device provided by the embodiments of the present application, ammonia borane is used as a precursor to prepare a boron nitride thin film, and then a gallium nitride layer is grown on the boron nitride thin film to form a heterojunction structure. The ratio of the amount of ammonia borane to the area of the substrate is 150 mg / cm 2 to 250 mg / cm 2 . Through the preparation method provided by the embodiments of the present application, a high-quality BN-GaN heterojunction neutron device can be provided, laying a foundation for the research and application of a new type of neutron detector to replace 3 the He tube. Based on using ammonia borane as a precursor to prepare a boron nitride thin film and then growing a gallium nitride layer on the boron nitride thin film, ammonia borane is non-toxic, non-flammable, non-explosive at room temperature, and stable and easy to store. It has a B / N stoichiometric ratio of 1:1. More importantly, its decomposition temperature is relatively low and the decomposition products are also pollution-free. It can serve as both a boron source and a nitrogen source and is a single precursor. This ensures the quality of the heterojunction device, reduces production costs, and has the advantages of a simple structure, relatively small volume, good linear range, short response time, easy n / γ discrimination, and high detection efficiency compared with traditional neutron detectors.

[0043] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following specific embodiments of the present invention are specifically given. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. And throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0045] Figure 1 is a schematic step flow chart of a preparation method of a heterojunction device according to an embodiment provided by the present application;

[0046] Figure 2 is a schematic structural diagram of a heterojunction device according to an embodiment provided by the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To better understand the above technical solution, the technical solution of the embodiments of the present application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solution of the embodiments of the present application, rather than limitations on the technical solution of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0048] As Figure 1 shown, according to the first aspect of the embodiments of the present application, a method for preparing a heterojunction device is proposed, including:

[0049] Step 101: Prepare a boron nitride thin film using ammonia borane as a precursor;

[0050] Step 102: Grow a gallium nitride layer on the boron nitride thin film to form a heterojunction structure;

[0051] Step 103: Etch the heterojunction structure and prepare an electrode layer to obtain a heterojunction device;

[0052] wherein, the ratio of the dosage of ammonia borane to the area of the substrate is 150 mg / cm 2 to 250 mg / cm 2 . As Figure 1 and Figure 2 shown, in the method for preparing a heterojunction device provided by the embodiments of the present application, a boron nitride thin film 120 is prepared using ammonia borane as a precursor, and then a gallium nitride layer 130 is grown on the boron nitride thin film 120 to form a heterojunction structure, and the ratio of the dosage of ammonia borane to the area of the substrate 110 is 150 mg / cm 2 to 250 mg / cm 2 . Through the preparation method provided by the embodiments of the present application, a high-quality BN-GaN heterojunction neutron device can be provided, laying a foundation for the research and application of a new type of neutron detector to replace 3 He tubes. Based on using ammonia borane as a precursor to prepare a boron nitride thin film 120 and then growing a gallium nitride layer 130 on the boron nitride thin film 120, ammonia borane is non-toxic, non-flammable, non-explosive at room temperature, and stable and easy to store. It has a B / N stoichiometric ratio of 1:1. More importantly, its decomposition temperature is relatively low and the decomposition products are also pollution-free. It can serve as both a boron source and a nitrogen source and is a single precursor. This ensures the quality of the heterojunction device, reduces production costs, and has the advantages of a simple structure, relatively small volume, good linear range, short response time, easy n / γ discrimination, and high detection efficiency compared with traditional neutron detectors.

[0053] The heterojunction device prepared by the preparation method of the heterojunction device provided by the embodiments of the present application can be applied to neutron devices in a BN-GaN heterojunction. The heterojunction device effectively combines the respective advantages of BN and GaN materials in a neutron detector, integrates neutron conversion and conversion signal detection into one, and can use the Flux method to grow a large-area BN single crystal as a neutron conversion layer and an n-type semiconductor layer, and epitaxially grow a GaN single crystal thin film on the surface of the BN single crystal by MOCVD, which can significantly improve the energy resolution and lower the detection limit, thereby greatly improving the efficiency of neutron detection.

[0054] For the preparation method provided by the embodiments of the present application, a boron nitride thin film 120 is first grown and prepared, and then a gallium nitride layer 130 is grown on the boron nitride thin film 120, which can improve the crystal quality of the heterojunction device, reduce defects, and further achieve the improvement of device performance, such as improving the charge carrier transport efficiency: the optimized energy band alignment of the heterojunction can significantly improve the transport efficiency of electrons and holes, reduce the recombination loss at the interface, and thus improve the output power and efficiency of the device. Reducing dark current and noise: a high-quality heterojunction structure can reduce interface defects and impurities, thereby reducing the dark current and noise levels, and improving the signal-to-noise ratio and sensitivity of the device. It can also improve the stability of the heterojunction device, such as improving thermal stability: by selecting a material combination with high thermal stability and optimizing the heterojunction structure, the stability and reliability of the device in a high-temperature environment can be improved. Enhancing chemical stability: certain heterojunction structures can resist chemical corrosion and oxidation, thereby extending the service life of the device. Reducing interface degradation: precisely controlling the interface quality of the heterojunction and reducing interface defects helps to reduce the interface recombination rate and reduce the degradation of the device during long-term use.

[0055] It can be understood that the BN-GaN heterojunction device prepared by the preparation method of the heterojunction device provided by the embodiments of the present application can reach the following technical indicators: (1) 10 The size of the BN crystal is greater than 1 cm2, and the thickness reaches more than 3 μm; (2) The thickness of the GaN single crystal thin film can be adjusted from 0.1 μm to 5 μm. The heterojunction device is small in volume; has a flat energy response curve; is insensitive to gamma-ray interference; has high sensitivity; has good anti-irradiation performance for the detector; and has a fast response speed. Compared with the first- and second-generation semiconductor materials such as Si and GaAs, the third-generation semiconductor GaN material has outstanding advantages such as a large bandgap, good thermal stability, high thermal conductivity, and excellent anti-irradiation ability. It is a preferred material for the preparation and research of high-frequency, high-temperature, and anti-irradiation devices, and can meet the material performance requirements for neutron detection under high-temperature and strong-irradiation conditions. h-BN, as a fourth-generation ultra-wide bandgap n-type semiconductor, has extremely high resistivity, high chemical stability, high negative electron affinity, and high thermal conductivity, and the isotope 10B has a very large thermal neutron absorption cross-section (about 3840 barns) and is very suitable for neutron detection. The present invention breaks through 10 the key growth technologies of BN, GaN, and 10BN-GaN heterojunction neutron detection materials, designs and fabricates 10 BN-GaN heterojunction devices. It lays a solid theoretical and experimental foundation for studying 10 BN-GaN heterojunction neutron detectors and mastering independent intellectual property rights, and will help to get rid of the unfavorable situation of being restricted by others in neutron detector technology for a long time.

[0056] As Figure 1 and Figure 2 shown, in a feasible implementation, the steps of preparing boron nitride thin film 120 using ammonia borane as a precursor include: providing a substrate 110 and cleaning the substrate 110; weighing ammonia borane and placing the substrate 110 and ammonia borane in a chemical vapor deposition system; repeatedly performing evacuation of the chemical vapor deposition system and introduction of inert gas until the air in the chemical vapor deposition system is exhausted; introducing nitrogen gas into the chemical vapor deposition system and heating to the growth temperature; depositing and preparing boron nitride thin film 120 on the substrate 110 based on ammonia borane.

[0057] In this technical solution, further provided for preparing boron nitride thin film 120 using ammonia borane as a precursor, first weigh ammonia borane, then evacuate the chemical vapor deposition system and introduce inert gas, and then introduce nitrogen gas as a carrier gas to grow boron nitride thin film 120, which is beneficial to the formation of boron nitride thin film 120 and beneficial to controlling the thickness of boron nitride thin film 120.

[0058] As Figure 1 and Figure 2 shown, in a feasible implementation, the steps of depositing and preparing boron nitride thin film 120 on the substrate 110 based on ammonia borane include: after the chemical vapor deposition system is heated to the growth temperature, annealing is performed to prepare boron nitride thin film 120 on the substrate; wherein, the growth temperature is 1200 °C to 1300 °C.

[0059] In this technical solution, further provided for the growth temperature of boron nitride thin film 120, by setting the growth temperature to 1200 °C to 1300 °C, it is beneficial to the formation of boron nitride thin film 120 and beneficial to controlling the thickness of boron nitride thin film 120.

[0060] In a feasible implementation, the substrate 110 is a sapphire substrate 110 with a thickness of 400 μm to 450 μm.

[0061] In this technical solution, the specific style of the substrate 110 is further provided. The substrate 110 is a sapphire substrate 110 with a thickness of 400 μm to 450 μm. Based on this, combined with the selection of ammonia borane as the precursor, the lattice mismatch between the sapphire substrate 110 (Al2O3) and h-BN is only 6.64%. Using a self-built low-pressure chemical vapor deposition system (LPCVD) to grow the h-BN thin film on the single-side polished sapphire substrate 110, on the premise that other growth conditions are the same, the crystal quality of the heterojunction structure can be improved and the defects can be reduced.

[0062] In some examples, preparing the boron nitride thin film 120 using ammonia borane as the precursor may include the following specific steps: The substrate 110 used is a sapphire substrate 110 (Al2O3) with a c-plane (0001) of 1×1 cm 2 and the thickness of the substrate 110 is 430 μm. First, place the substrate 110 in an ultrasonic cleaner and ultrasonically clean it with C3H6O (acetone), anhydrous C2H6O (ethanol), and deionized water in sequence for 15 minutes. After the ultrasonic cleaning is completed, take out the sapphire substrate 110, dry it with nitrogen (N2), and place it in a cleaned corundum boat. Then, push the corundum boat to the center position of the tube furnace temperature zone through a furnace hook, and finally tighten the vacuum flanges at both ends of the tube furnace. Weigh 200 mg of ammonia borane using an electronic balance, put it into a quartz boat, and send the quartz boat containing ammonia borane into the box furnace through a furnace hook, waiting for program-controlled heating. Turn on the mechanical pump and pump the system vacuum to 1 Pa. Then, turn off the mechanical pump and introduce the inert gas Ar (10 sccm) to increase the system pressure to 2000 Pa. At this time, close the Ar gas valve, and turn on the mechanical pump again to repeat the above steps 2 times to evacuate the air in the system. After the last time the system vacuum is pumped to 1 Pa in the previous step, start the heating program of the tube furnace, introduce N2 (100 sccm) to keep the temperature rising process in the atmosphere required for annealing. After the temperature stabilizes at the growth temperature (1200 - 1300 °C), start annealing for 30 min. 10 minutes before the annealing treatment of the substrate 110 ends, turn on the heating program of the box furnace, and raise the temperature to 110 °C at a uniform rate in 10 minutes and maintain it for 120 min. After the annealing treatment of the substrate 110 for 30 min ends, at this time, the box furnace also heats up to 110 °C. Open the source supply valve, turn on the source carrier gas Ar (20 sccm), keep the carrier gas flow rate unchanged, and continue to grow for 120 min. After the growth ends, cut off the source supply, introduce Ar (100 sccm), and start cooling to room temperature. After cooling to room temperature, keep it warm for 24 - 72 hours and then cool it to 15 - 25 °C at a rate of 0.5 °C / h. The h-BN crystals precipitate on the metal surface, and then quickly quench to room temperature. Thus, the boron nitride thin film 120 can be grown on the substrate 110.

[0063] In some examples, after the growth of the boron nitride thin film 120 is completed, the sample can be taken out to start the characterization test. By changing the temperature parameters in the experiment under a specific system, the quantity and quality of nucleation can be observed and characterized. For the experimental observation of the nucleation process, SEM can be used to statistically calculate the crystal nucleation rate under different growth conditions. In addition, techniques such as synchrotron radiation X-ray and HRTEM can also directly obtain crystal nucleation information. Specifically, its morphology and structure can be characterized by an optical microscope, a scanning electron microscope, and a high-resolution transmission electron microscope; its crystal quality and composition can be analyzed by Raman spectroscopy, X-ray diffraction, electron energy loss spectroscopy, energy spectrum analysis, etc.

[0064] In a feasible implementation, the steps of growing a gallium nitride layer 130 on the boron nitride thin film 120 to form a heterojunction structure include: growing a gallium nitride layer 130 on the boron nitride thin film 120 by metalorganic chemical vapor deposition process to form a heterojunction structure.

[0065] In this technical solution, a specific preparation method of the gallium nitride layer 130 is further provided. A gallium nitride layer 130 can be grown on the boron nitride thin film 120 by metalorganic chemical vapor deposition process. By utilizing the thermal decomposition reaction of organometallic compounds and performing epitaxial growth in the gas phase, a high-quality thin film can be prepared. This thin film has excellent crystallinity and purity and can meet the high requirements of high-performance devices for material quality. By precisely controlling parameters such as the flow rate of the raw material gas, reaction temperature, and time, precise control of the film composition and thickness can be achieved. This precise control helps to prepare a thin film with a specific composition and thickness, thus meeting the needs of device design.

[0066] In a feasible implementation, the steps of growing a gallium nitride layer 130 on the boron nitride thin film 120 by metalorganic chemical vapor deposition process to form a heterojunction structure include: cleaning the reaction furnace chamber and the tray; evacuating the reaction chamber to remove the air in the reaction chamber; heating the reaction chamber, and when the heating temperature reaches the preset temperature, introducing hydrogen and ammonia into the reaction chamber to nitride the surface of the substrate 110 of the boron nitride thin film 120 to form an aluminum nitride nucleation layer; stopping the introduction of hydrogen, maintaining the introduction of ammonia, and simultaneously introducing trimethylgallium and silane to grow a gallium nitride layer 130 on the boron nitride thin film 120.

[0067] This application takes into account that since there is no natural GaN single crystal material in nature, and it is an extremely stable and hard high melting point material (with a melting point as high as 1750 °C), it is necessary to rely on material growth methods to achieve GaN single crystal materials (GaN belongs to group III-V compounds). The present invention uses MOCVD technology as the key technology applied in the epitaxial growth of GaN devices. The organic precursors in the MOCVD system include metal organic materials and hydrides. For the growth of group III-V nitride semiconductors, there are usually five types of metal organic precursors and two types of hydride precursors, which are trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMAl), triethylgallium (TEGa), bis(cyclopentadienyl)magnesium (Cp2Mg), ammonia (NH3) and silane (SiH4). TMGa, TEGa and TMAl are liquids, while TMIn and Cp2Mg are solids at room temperature. AlN and AlGaN are two very important materials in the nitride material system. As an excellent subsequent epitaxial basis, the quality of AlN can determine the quality of the GaN epitaxial layer.

[0068] In this technical solution, specific steps for metal-organic chemical vapor deposition are further provided. First, clean the reaction furnace chamber and the tray, and then remove the air in the reaction chamber to be able to remove the influence of impurities on the growth of the gallium nitride layer 130. Then, introduce hydrogen and ammonia into the reaction chamber to nitride the surface of the substrate 110 of the boron nitride thin film 120 to form an aluminum nitride nucleation layer. After that, keep the ammonia introduced, and at the same time introduce trimethylgallium and silane, which can ensure the stable growth of the gallium nitride layer 130, thereby improving the crystal quality of the heterojunction device, reducing defects, and further realizing the improvement of device performance.

[0069] In a feasible implementation manner, the steps for cleaning the reaction furnace chamber and the tray include: dust collection in the reaction furnace chamber; heating the reaction furnace chamber to the cleaning temperature and introducing a cleaning gas at the same time to bake the reaction furnace chamber and the tray; cleaning the tray with a cleaning liquid and then drying the tray. Such a setting can make the removal of impurities more thorough.

[0070] In some examples, the steps for growing the gallium nitride layer 130 may specifically include: First, perform maintenance on the equipment and bake the tray. Clean the reaction furnace chamber with a dust suction device to remove the particles and dust in the chamber. Use a baking tray furnace to bake the tray carrying the substrate 110 at a temperature of 1300 °C, a high-temperature zone pressure of 530 Pa, and a H2 ratio of 7% in the gas to remove the dust and particles on the tray. Clean the substrate 110. Ultrasonically clean the substrate 110 successively with acetone, ethanol, and deionized water for 15 minutes. After three cleanings, dry it with high-purity nitrogen. Evacuate the reaction chamber. Place the cleaned substrate 110 on the tray, install it into the reaction chamber, close the reaction chamber door, and successively turn on the mechanical pump and valve to evacuate the reaction chamber to remove the air in the chamber for 60 minutes until the vacuum degree reaches 1×10 -2 Pa, then close the valve and the vacuum mechanical pump. Preheat the substrate 110. Introduce H2 into the chamber, keep the flow rate of the introduced H2 unchanged, set the temperature to 1080 °C, and keep it for 10 minutes after the temperature rise is stable. Nitridize the substrate 110. Keep introducing H2 into the chamber, and at the same time keep the temperature of the substrate 110 at 1080 °C. Introduce NH3 into the chamber and keep it for 10 minutes to make 10 the surface of the BN substrate 110 undergo nitridation to form an AlN nucleation layer with a thickness of 20 nm. Subsequently, stop introducing H2 and keep NH3 continuously introduced into the chamber. Epitaxially grow n-type GaN. Set the pressure to 0.3 MPa, adjust the temperature to 1020 °C, and start gradually growing n-type lightly doped Al x Ga 1-x N, where the Al component is 0.02, and control the flow rates and ratios of trimethylgallium, silane, and ammonia; then grow lightly doped n-Al x Ga 1-x N, with an Al component of 0.02 and a controllable material thickness, and control the flow rates and ratios of trimethylgallium, silane, and ammonia; adjust the temperature condition to 1040 °C and the pressure to 0.3 MPa, and start growing n-type doped Al x Ga 1-x N, with an Al component of 0.02 and a controllable thickness. By setting it in this way, the stable growth of the gallium nitride layer 130 can be ensured, and the quality of the heterojunction device can be guaranteed. In this way, using an ultra-pure single crystal as the seed crystal and the growth technology of MOCVD, GaN epitaxial layers with different thicknesses and doping concentrations can be epitaxially grown on the large-size 10 BN-based substrate 110, overcoming the interfacial stress in heterojunction epitaxial growth. The raw materials used in the preparation mainly include: trimethylgallium, trimethylaluminum, trimethylindium, high-purity SF6, high-purity SiH4, 6-inch Si substrate 110, graphite disk, high-purity Au, high-purity Pt, high-purity W, high-purity Ti, high-purity N, high-purity Fe and other auxiliary materials.

[0071] In a feasible implementation manner, the steps of etching the heterojunction structure and preparing the electrode layer to obtain the heterojunction device include: cleaning the surface of the epitaxial wafer of the heterojunction structure; etching the heterojunction structure to form an electrode pattern; preparing an ohmic contact electrode 140 and an insulating layer based on the electrode pattern to obtain the heterojunction device. With such a setting, it is convenient to excite the heterojunction structure.

[0072] In some examples, forming the electrode pattern may specifically include the following steps:

[0073] First, surface cleaning. This step removes the contaminants adhering to the surface of the GaN epitaxial wafer and the oxide on the GaN surface. Ultrasonic cleaning is performed with acetone and ethanol in sequence for 15 minutes each, followed by deionized water cleaning and nitrogen blowing dry; the temperature of the mixed solution of concentrated sulfuric acid / hydrogen peroxide / water with a volume ratio of 5:1:1 is stabilized at 60 °C, and the sample is soaked for 5 minutes, then the sample is cleaned; the sample is soaked in 20% dilute hydrochloric acid for 5 minutes, then the sample is cleaned and spun dry.

[0074] Tabletop etching. This step mainly etches out n-GaN and BN for subsequent electrode fabrication. The sample is preheated and baked on a hot plate at 105 °C; spin coating (positive photoresist); pre-baking at 105 °C; exposure, the sample is exposed using a tabletop etching photomask; development; hard baking at 125 °C; tabletop etching, the sample is subjected to ICP etching (reactive ion etching) with BCl3 plasma; stripping the photoresist, the temperature of the photoresist stripping solution is stabilized at 75 - 85 °C, soaked for 20 minutes, after cleaning the sample, the residual photoresist between the lines and at the steps is further removed with oxygen plasma, and the removal time is 90 s.

[0075] h -10 BN surface electrode preparation. This step is to prepare an ohmic contact electrode 140 on h -10 BN for subsequent device lead testing. First, the sample is preheated and baked on a hot plate at 105 °C for 1 minute; spin coating (positive photoresist); pre-baking; exposure, the sample is exposed using a h -10 BN electrode pattern photomask; development; hard baking; depositing metal, Cr / Ni / Au are sequentially deposited on the sample surface by electron beam evaporation with thicknesses of 30 nm / 13 nm / 1200 nm respectively. Stripping the metal, the sample is placed in the stripping solution and soaked for 30 minutes. This step removes the excess metal on the sample surface, making the metal film on the sample surface into the designed positive and negative electrode patterns.

[0076] Fabrication of n-GaN surface electrodes. In this step, an ohmic contact electrode 140 is fabricated on n-GaN for subsequent device lead testing. The steps are as follows: preheat the sample by baking it on a hot plate at 100 °C; spin-coat (positive photoresist); pre-bake at 105 °C; expose the sample using a lithography mask with the n-GaN electrode pattern; develop; hard-bake at 125 °C; deposit metal by sequentially depositing Cr / Ni / Au on the sample surface using electron beam evaporation; strip the metal by placing the sample in a stripping solution, which removes the excess metal on the sample surface and forms the designed positive and negative electrode patterns on the metal film on the sample surface.

[0077] Fabrication of the insulating layer and via holes for the electrodes. In this step, SiO2 is deposited around the device to protect the electrodes, prevent conduction, and reduce leakage. First, use electron beam evaporation to deposit a 100-nm-thick SiO2 layer on both sides of the sample. Then preheat the sample by baking it on a hot plate at 100 °C for 1 minute; spin-coat (positive photoresist); pre-bake at 105 °C for 90 s; expose the sample using a lithography mask with the electrode interface pattern; develop; hard-bake at 125 °C for 30 minutes; etch the SiO2 layer by placing the sample in a buffered hydrofluoric acid solution and soaking for 15 min, followed by rinsing with deionized water; strip the photoresist by placing the sample in a stripping solution and soaking for 30 minutes, which removes the excess photoresist on the sample surface.

[0078] In a feasible embodiment, the method for fabricating a heterojunction device further includes: providing a packaging case and encapsulating the heterojunction device in the packaging case; wherein, the electrodes of the heterojunction device are connected to the pins of the packaging case. This arrangement facilitates connecting the fabricated heterojunction device to other devices.

[0079] As Figure 2 shown, according to the second aspect of the embodiments of the present application, a heterojunction device is provided, and the heterojunction device is fabricated by the method for fabricating a heterojunction device according to any of the above technical solutions.

[0080] The heterojunction device provided by the embodiments of the present application is fabricated by the method for fabricating a heterojunction device according to any of the above technical solutions, so the heterojunction device has all the beneficial effects of the method for fabricating a heterojunction device of the above technical solutions.

[0081] The crystal provided by the embodiment of the present application has high quality and few defects, thereby realizing the improvement of device performance, such as improving the charge carrier transport efficiency: the optimized energy band alignment of the heterojunction can significantly improve the transport efficiency of electrons and holes, reduce the recombination loss at the interface, and thus improve the output power and efficiency of the device. Reducing dark current and noise: The high-quality heterojunction structure can reduce interface defects and impurities, thereby reducing the dark current and noise levels, and improving the signal-to-noise ratio and sensitivity of the device. It can also improve the stability of the heterojunction device, such as improving thermal stability: By selecting a material combination with high thermal stability and optimizing the heterojunction structure, the stability and reliability of the device in a high-temperature environment can be improved. Enhancing chemical stability: Certain heterojunction structures can resist chemical corrosion and oxidation, thereby extending the service life of the device. Reducing interface degradation: Precise control of the interface quality of the heterojunction and reduction of interface defects help to reduce the interface recombination rate and reduce the degradation of the device during long-term use, laying a foundation for the research and development and application of a new type of neutron detector to replace 3 the He tube.

[0082] The heterojunction device provided by the embodiment of the present application can reach the following technical indicators: (1) 10 The size of the BN crystal is greater than 1 cm2, and the thickness reaches more than 3 μm; (2) The thickness of the GaN single crystal thin film can be adjusted from 0.1 μm to 5 μm. This heterojunction device is small in volume; has a flat energy response curve; is insensitive to gamma-ray interference; has high sensitivity; has good anti-irradiation performance for the detector; and has a fast response speed. Compared with the first- and second-generation semiconductor materials such as Si and GaAs, the third-generation semiconductor GaN material has outstanding advantages such as a large bandgap, good thermal stability, high thermal conductivity, and excellent anti-irradiation ability. It is an ideal material for the preparation and research of high-frequency, high-temperature, and anti-irradiation devices, and can meet the material performance requirements for neutron detection under high-temperature and strong-irradiation conditions. h-BN, as a fourth-generation ultra-wide bandgap n-type semiconductor, has extremely high resistivity, high chemical stability, high negative electron affinity, and high thermal conductivity, and the isotope 10 B has a very large thermal neutron absorption cross-section (about 3840 barns), which is very suitable for neutron detection. The present invention has broken through 10 the key growth technologies of BN, GaN, and 10BN-GaN heterojunction neutron detection materials, and designed and prepared 10 the BN-GaN heterojunction device. It has laid a solid theoretical and experimental foundation for the research of 10 the BN-GaN heterojunction type neutron detector and the acquisition of independent intellectual property rights, and will help to get rid of the unfavorable situation of being restricted by others in neutron detector technology for a long time. Combining 10Due to the excellent thermal neutron absorption and conversion ability of BN, the effective detection of the products after neutron conversion by single-crystalline GaN thin films is a key step in the generation of the detector signal. High-quality single-crystalline GaN thin films can reduce the scattering and trapping of radiation-generated carriers by defects, which is the key to improving the detector performance. In specific implementation, through the GaN buffer layer technology, adjusting the growth parameters of MOCVD, epitaxially growing a GaN epitaxial layer with a thickness of more than 3 μm on a large-size substrate 110, and using XRD and wafer warp measurement technologies to evaluate the dislocation density and wafer warp, and mastering the stress control technology of large-size GaN thick films. Adopting the surface reaction enhanced pulsed MOCVD growth method with continuous metal organic sources and pulsed ammonia gas to solve 10 the key technology of epitaxially growing GaN materials on a BN substrate.

[0083] It can be understood that the heterojunction device provided in the embodiment of the present application includes a substrate 110, a boron nitride thin film 120, a gallium nitride layer 130, an ohmic contact electrode 140, an insulating layer, and a circuit board 150 layer sequentially arranged on the substrate 110.

[0084] In the present invention, the terms "first", "second", and "third" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. Terms such as "installed", "connected", "connected", and "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0086] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a heterojunction device, characterized in that, Including: Preparing a boron nitride thin film using ammonia borane as a precursor; Growing a gallium nitride layer on the boron nitride thin film to form a heterojunction structure; Etching the heterojunction structure and preparing an electrode layer to obtain a heterojunction device; Among them, the ratio of the dosage of the ammonia borane to the area of the substrate is 150 mg / cm 2 to 250 mg / cm 2 .

2. The preparation method of the heterojunction device according to claim 1, characterized in that, The step of preparing a boron nitride thin film using ammonia borane as a precursor includes: Providing a substrate and cleaning the substrate; Weighing ammonia borane and placing the substrate and the ammonia borane in a chemical vapor deposition system; Repeatedly performing evacuation of the chemical vapor deposition system and introduction of an inert gas until the air in the chemical vapor deposition system is exhausted; Introducing nitrogen into the chemical vapor deposition system and heating to a growth temperature; Depositing and preparing the boron nitride thin film on the substrate based on the ammonia borane.

3. The manufacturing method of the heterojunction device according to claim 2, characterized in that, The step of depositing and preparing the boron nitride thin film on the substrate based on the ammonia borane includes: After the chemical vapor deposition system is heated to the growth temperature, annealing is performed to prepare the boron nitride thin film on the substrate; Wherein, the growth temperature is 1200 °C to 1300 °C.

4. The method for preparing a heterojunction device according to claim 2, wherein The substrate is a sapphire substrate with a thickness of 400 μm to 450 μm.

5. The preparation method of the heterojunction device according to claim 1, characterized in that, The step of growing a gallium nitride layer on the boron nitride thin film to form a heterojunction structure includes: Growing a gallium nitride layer on the boron nitride thin film by metalorganic chemical vapor deposition to form a heterojunction structure.

6. The manufacturing method of the heterojunction device according to claim 5, characterized in that, The step of growing a gallium nitride layer on the boron nitride thin film by metalorganic chemical vapor deposition to form a heterojunction structure includes: Cleaning the reaction furnace chamber and the tray; Evacuating the reaction chamber to remove the air in the reaction chamber; Heating the reaction chamber, and when the heating temperature reaches a preset temperature, introducing hydrogen and ammonia into the reaction chamber to nitride the surface of the substrate of the boron nitride thin film to form a gallium nitride nucleation layer; Stopping the introduction of hydrogen, maintaining the introduction of ammonia, and simultaneously introducing trimethylgallium and silane to grow a gallium nitride layer on the boron nitride thin film.

7. The manufacturing method of the heterojunction device according to claim 6, characterized in that, The step of cleaning the reaction furnace chamber and the tray includes: Collecting dust from the reaction furnace chamber; Heating the reaction furnace chamber to a cleaning temperature and simultaneously introducing a cleaning gas to bake the reaction furnace chamber and the tray; Cleaning the tray with a cleaning liquid and then drying the tray.

8. The manufacturing method of the heterojunction device according to claim 6, characterized in that, The step of etching the heterojunction structure and preparing an electrode layer to obtain a heterojunction device includes: Cleaning the surface of the epitaxial wafer of the heterojunction structure; Etching the heterojunction structure to form an electrode pattern; Preparing an ohmic contact electrode and an insulating layer based on the electrode pattern to obtain the heterojunction device.

9. The preparation method of the heterojunction device according to any one of claims 1 to 8, characterized in that, Further including: Providing a packaging shell and packaging the heterojunction device in the packaging shell; Wherein, the electrodes of the heterojunction device are connected to the pins of the packaging shell.

10. A heterojunction device, wherein The heterojunction device is prepared by the method for preparing a heterojunction device according to any one of claims 1 to 8.

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