A gallium nitride alpha particle detector and its preparation method

Abstract

The present application provides a gallium nitride alpha particle detector and a preparation method thereof, including a silicon substrate, a multi-stage intermediate layer, and a GaN epitaxial layer. The multi-stage intermediate layer is formed between the silicon substrate and the GaN epitaxial layer, and the multi-stage intermediate layer at least includes a grading layer with a gradually changing Al element content. By forming a grading layer between the silicon substrate and the GaN epitaxial layer and gradually decreasing the content of the Al element in the grading layer from the side close to the silicon substrate to the side close to the GaN epitaxial layer, the gradual regulation of the lattice constant of the grading layer is realized, thereby effectively alleviating the lattice mismatch between the GaN epitaxial layer and the silicon substrate, reducing the defect density of the GaN epitaxial layer, and improving its crystallization quality. Finally, a high-quality thick film GaN epitaxial layer is grown on the silicon substrate to realize the preparation of a gallium nitride alpha particle detector based on the silicon substrate.

Description

Technical Field

[0001] This application relates to the field of α-particle detection technology, and particularly to a gallium nitride α-particle detector and a preparation method thereof. Background Art

[0002] An α-particle is a common particle generated during the decay process of radioactive substances. It is a particle composed of two protons and two neutrons and has relatively high energy. α-particle detectors have important applications in multiple fields, especially in radioactive monitoring, environmental protection, medical treatment, nuclear power safety, and fusion research. α-particle detectors can efficiently detect radioactive substances, thereby protecting public health and environmental safety, promoting scientific research, and playing a key role in safety monitoring.

[0003] Gallium nitride (GaN) is a wide-bandgap semiconductor material with excellent physical and electrical properties, which shows significant advantages in the field of α-particle detection. Although gallium nitride materials have excellent physical and electrical properties, showing significant advantages in the field of α-particle detection. However, existing gallium nitride α-particle detectors still face many technical problems and challenges in the actual application process and are difficult to achieve the expected high performance. Currently, there is no report on high-performance gallium nitride α-particle detectors based on silicon substrates. First, due to the large lattice mismatch and difference in thermal expansion coefficient between the silicon substrate and gallium nitride material, when growing a thick film GaN epitaxial layer on the silicon substrate by epitaxial growth, a large number of defects are likely to appear in the GaN epitaxial layer, and even the GaN epitaxial layer may crack. To solve this problem, existing technologies usually need to introduce a buffer layer to relieve the lattice mismatch and thermal mismatch and reduce the generation of defects. However, traditional buffer layer processes are difficult to effectively obtain a high-quality thick film GaN epitaxial layer, and high-performance α-particle detectors require the GaN epitaxial layer to be able to completely absorb the energy of α-particles, which requires the GaN epitaxial layer to have sufficient thickness and excellent quality. Second, the good electrical conductivity of the silicon substrate also easily leads to an increase in the leakage current of silicon substrate devices, and gallium nitride α-particle detectors have strict requirements for leakage current, and excessive leakage current will significantly affect the performance of α-particle detectors. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems in the related technologies to some extent.

[0005] To this end, the first object of this application is to propose a gallium nitride α-particle detector and a preparation method thereof, which can grow a high-quality thick film GaN epitaxial layer on a silicon substrate, effectively reduce the leakage current of the gallium nitride α-particle detector, and realize the preparation of a gallium nitride α-particle detector based on a silicon substrate.

[0006] To achieve the above object, an embodiment of the first aspect of the present application provides a gallium nitride alpha particle detector for detecting alpha particles, the alpha particle detector comprising:

[0007] A silicon substrate;

[0008] A multi-stage intermediate layer formed on the silicon substrate;

[0009] A GaN epitaxial layer formed on the multi-stage intermediate layer;

[0010] Wherein, the multi-stage intermediate layer at least includes a grading layer containing Al element, the content of Al element in the grading layer changes gradually, and the content of Al element gradually decreases from the side close to the silicon substrate to the side close to the GaN epitaxial layer.

[0011] Optionally, the grading layer at least includes an AlN layer, an AlGaN layer and a GaN layer stacked in sequence from bottom to top; wherein, the content of Al element in the AlGaN layer changes gradually, and the content of Al element gradually decreases from the side close to the AlN layer to the side close to the GaN layer.

[0012] Optionally, the multi-stage intermediate layer further includes a GaN high-resistance layer, an AlGaN graded layer, a GaN low-resistance layer and a GaN graded layer stacked in sequence from bottom to top, and the GaN high-resistance layer is formed on the grading layer, and the GaN epitaxial layer is formed on the GaN graded layer.

[0013] Optionally, the content of Al element in the AlGaN graded layer changes gradually, and the content of Al element gradually decreases from the side close to the GaN high-resistance layer to the side close to the GaN low-resistance layer.

[0014] Optionally, the GaN low-resistance layer contains heavily doped Si element, and the doping concentration range of Si element in the GaN low-resistance layer is between 5 10 17 cm -3 ~ 1 10 20 cm -3 .

[0015] Optionally, the GaN graded layer contains Si element with a gradually changing doping concentration, and the doping concentration of Si element in the GaN graded layer gradually decreases from the side close to the GaN low-resistance layer to the side close to the GaN epitaxial layer.

[0016] Optionally, the thickness range of the GaN graded layer is between 100 nm and 1000 nm, and the thickness range of the GaN epitaxial layer is between 10 μm and 30 μm.

[0017] Optionally, a stepped portion is provided on a side of the GaN low-resistance layer away from the silicon substrate. The stepped portion includes a stepped upper surface and a lower surface surrounding the upper surface, and the GaN epitaxial layer is formed on the upper surface.

[0018] Optionally, the α-particle detector further includes an electrode structure. The electrode structure includes a first electrode and a second electrode arranged at intervals. The first electrode is located on the upper surface, and the second electrode is located on the lower surface, and the second electrode is arranged to surround the first electrode on its circumference.

[0019] To achieve the above object, a second aspect embodiment of the present application provides a method for manufacturing a gallium nitride α-particle detector for manufacturing the α-particle detector described in any one of the above, including:

[0020] Providing a silicon substrate;

[0021] Forming an epitaxial stack layer on the silicon substrate. The epitaxial stack layer includes a grading layer, a GaN high-resistance layer, an AlGaN graded layer, a GaN low-resistance layer, a GaN graded layer, and a GaN epitaxial layer stacked in sequence from bottom to top;

[0022] Etching on a side of the epitaxial stack layer away from the silicon substrate to form an epitaxial structure with a stepped step. The stepped step includes an upper step and a lower step. The upper step is the upper surface of the GaN epitaxial layer, and the lower step is the surface of the GaN low-resistance layer exposed by etching;

[0023] Forming an electrode structure on the epitaxial structure. The electrode structure includes a first electrode and a second electrode. The first electrode is formed on the upper step, and the second electrode is formed on the lower step;

[0024] Forming a passivation layer on the epitaxial structure. The passivation layer covers the stepped step and the sides of the electrode structure and exposes the upper surfaces of the first electrode and the second electrode respectively.

[0025] The gallium nitride α-particle detector and its manufacturing method provided by the present application at least include the following beneficial effects:

[0026] The present application provides a gallium nitride alpha particle detector and a preparation method thereof, including a silicon substrate, a multi-stage intermediate layer, and a GaN epitaxial layer. The multi-stage intermediate layer is formed between the silicon substrate and the GaN epitaxial layer, and the multi-stage intermediate layer at least includes a grading layer with a gradually changing Al element content. By forming a grading layer between the silicon substrate and the GaN epitaxial layer and gradually reducing the Al element content in the grading layer from the side close to the silicon substrate to the side close to the GaN epitaxial layer, the gradual regulation of the lattice constant of the grading layer is realized, thereby effectively alleviating the lattice mismatch between the GaN epitaxial layer and the silicon substrate, reducing the defect density of the GaN epitaxial layer, and improving its crystallization quality. Finally, a high-quality thick-film GaN epitaxial layer is grown on the silicon substrate to realize the preparation of a gallium nitride alpha particle detector based on the silicon substrate.

[0027] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present application. Description of the Drawings

[0028] The above-mentioned and / or additional aspects and advantages of the present application will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0029] Figure 1 FIG. is a schematic top view structure diagram of a gallium nitride alpha particle detector shown according to an embodiment of the present application.

[0030] Figure 2 As shown in Figure 1 FIG. is a schematic cross-sectional structure diagram of a gallium nitride alpha particle detector taken along the AA' cut line in

[0031] Figure 3 FIG. is a schematic flow chart of a preparation method of a gallium nitride alpha particle detector shown according to an embodiment of the present application.

[0032] 100 Silicon substrate; 210 Grading layer; 220 GaN high-resistance layer; 230 AlGaN gradient layer; 240 GaN low-resistance layer; 250 GaN gradient layer; 300 GaN epitaxial layer; 410 First electrode; 420 Second electrode; 500 Passivation layer. Detailed Embodiments

[0033] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.

[0034] Gallium nitride materials can work stably for a long time in high-temperature and high-radiation environments. At the same time, due to its wide bandgap characteristics, it can significantly reduce the dark current and improve the sensitivity and signal-to-noise ratio of the detector, making gallium nitride gradually become an ideal choice for the preparation of a new generation of alpha particle detector materials. In addition, the high-temperature and strong-radiation resistance characteristics of gallium nitride devices give them significant advantages in nuclear radiation detection.

[0035] However, in practical applications, gallium nitride alpha particle detectors still face many technical problems and challenges in preparation methods, and it is difficult to achieve the expected high performance. Currently, there is no report on high-performance gallium nitride alpha particle detectors based on silicon substrates, and the main reasons are as follows:

[0036] First of all, due to the large lattice mismatch and difference in thermal expansion coefficient between silicon and GaN materials, when growing a thick film GaN epitaxial layer on a silicon substrate, a large number of defects are likely to appear in the GaN epitaxial layer, and even cause cracking of the GaN epitaxial layer. To solve this problem, existing technologies usually need to introduce a buffer layer to relieve the lattice mismatch and thermal mismatch and reduce the internal defect density of the GaN epitaxial layer. However, traditional buffer layer processes are difficult to effectively obtain a high-quality thick film GaN epitaxial layer on a silicon substrate, and high-performance gallium nitride alpha particle detectors require the GaN epitaxial layer to be able to completely deposit the energy of alpha particles, which requires the GaN epitaxial layer to have sufficient thickness and excellent quality. That is to say, the GaN epitaxial layer, as the effective detection area of the alpha particle detector, is used to receive and deposit the alpha particles incident on the detector. How to grow a GaN epitaxial layer with high epitaxial quality and large thickness on a silicon substrate plays a key role in the successful preparation of gallium nitride alpha particle detectors based on silicon substrates.

[0037] Secondly, the good conductivity of the silicon substrate also easily leads to an increase in the leakage current of silicon substrate devices, while gallium nitride alpha particle detectors have strict requirements for leakage current, and excessive leakage current will also significantly affect the performance of alpha particle detectors.

[0038] Based on the above problems, the embodiments of the present application provide a gallium nitride alpha particle detector and its preparation method. The alpha particle detector sets multiple intermediate layers between the silicon substrate and the GaN epitaxial layer, uses the multiple intermediate layers to improve the epitaxial quality of the GaN epitaxial layer, and at the same time significantly reduces the leakage current between the silicon substrate and the GaN epitaxial layer, thereby realizing the preparation of gallium nitride alpha particle detectors based on silicon substrates.

[0039] According to the embodiments of the first aspect of the present application, a gallium nitride alpha particle detector is provided, as Figure 1 and Figure 2As shown, the α-particle detector structure includes a substrate 100, a multi-level intermediate layer, and a GaN epitaxial layer 300, and the multi-level intermediate layer is formed between the substrate 100 and the GaN epitaxial layer 300. Among them, the multi-level intermediate layer includes a grading layer 210, a GaN high-resistance layer 220, an AlGaN graded layer 230, a GaN low-resistance layer 240, and a GaN graded layer 250 that are stacked in sequence from bottom to top. The GaN epitaxial layer 300 is formed on the GaN graded layer 250. The GaN epitaxial layer 300 is a thick-film undoped GaN epitaxial layer 300, and the thickness range of the GaN epitaxial layer 300 can be between 10 μm and 30 μm.

[0040] It can be understood that the α-particle detector provided in this application is used to detect the incident energy of α-particles. When the incident α-particles enter the GaN epitaxial layer 300, they can generate a large number of electron-hole pairs due to the Coulomb interaction with the shell electrons of the atoms in the GaN epitaxial layer 300. Thus, when an electric field is applied to both sides of the GaN epitaxial layer 300 along the thickness direction, the electrons and holes generated in the GaN epitaxial layer 300 can drift directionally under the action of the electric field and generate corresponding electrical signals. By receiving the electrical signals and combining with an energy spectrum analysis system, the incident energy of α-particles in the environment can be calculated. In this application, by forming the multi-level intermediate layer between the silicon substrate 100 and the GaN epitaxial layer 300, the lattice mismatch and thermal mismatch between the silicon substrate 100 and the GaN epitaxial layer 300 are reduced by using the multi-level intermediate layer, so that during the process of epitaxial growth to form a thick GaN epitaxial layer 300, the internal lattice mismatch and defect density of the GaN epitaxial layer 300 can be greatly reduced, thereby improving the epitaxial quality of the thick GaN epitaxial layer 300.

[0041] Furthermore, the multi-level intermediate layer can at least include a grading layer 210. The grading layer 210 contains Al elements with a gradually changing content, and the content of Al elements gradually decreases from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300.

[0042] Due to the large lattice constant difference between the silicon substrate 100 and the GaN epitaxial layer 300, when the GaN epitaxial layer 300 is directly epitaxially formed on the silicon substrate 100, the formed GaN epitaxial layer 300 will have a very high defect density, and even directly cause the formed GaN epitaxial layer 300 to crack. In this application, a grading layer 210 is formed between the silicon substrate 100 and the GaN epitaxial layer 300, and the content of internal Al element in the grading layer 210 is configured to gradually decrease from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300. By using the gradually changing Al element in the grading layer 210, the gradual regulation of the lattice constant of the grading layer 210 is realized, thereby alleviating the lattice mismatch between the GaN epitaxial layer 300 and the silicon substrate 100, reducing the defect density of the GaN epitaxial layer 300, and improving the epitaxial quality of the thick-film GaN epitaxial layer 300 grown on the silicon substrate 100.

[0043] As an example, the grading layer 210 at least includes an AlN layer, an AlGaN layer, and a GaN layer that are stacked in sequence from bottom to top. Among them, the content of Al element in the AlGaN layer changes gradually, and the content of Al element gradually decreases from the side close to the AlN layer to the side close to the GaN layer.

[0044] Setting the grading layer 210 as an AlN layer, an AlGaN layer, and a GaN layer that are stacked in sequence from bottom to top can make the lattice constant of the grading layer 210 show a gradient change from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300. At the same time, in this application, the AlGaN layer is also set to have a gradually changing content of Al element. By grading the regulation of the Al content, the lattice constant of the AlGaN layer gradually transitions from being close to the AlN layer to being close to the GaN layer, so as to more effectively reduce the lattice mismatch caused by the lattice constant difference and reduce the internal defect density of the GaN layer, improving the crystallization quality of the GaN layer. In addition, the difference in thermal expansion coefficients between the AlN layer and the GaN layer will also cause stress. Through the AlGaN layer with a gradually changing Al content, a smooth transition of the thermal expansion coefficient between the AlN layer and the GaN layer can be achieved, reducing the risk of cracks in the GaN layer.

[0045] Furthermore, a GaN high-resistance layer 220 is also provided between the grading layer 210 and the GaN epitaxial layer 300. By forming the GaN high-resistance layer 220 on the grading layer 210, the leakage path between the GaN low-resistance layer 240 and the silicon substrate 100 can be effectively blocked, thereby improving the performance of the α-particle detector. As an example, the GaN high-resistance layer 220 is an iron-doped GaN high-resistance layer 220, and by doping iron elements in the GaN high-resistance layer 220, the resistance of the GaN high-resistance layer 220 is increased.

[0046] It should be noted that the above-mentioned substrate may include but is not limited to the silicon substrate 100.

[0047] In some embodiments, a GaN low-resistance layer 240 is further provided on the GaN high-resistance layer 220, as well as an electrode structure and a passivation layer 500 located above the GaN low-resistance layer 240.

[0048] The GaN low-resistance layer 240 is a heavily Si-doped GaN low-resistance layer 240. By forming a GaN low-resistance layer 240 with a certain thickness between the GaN high-resistance layer 220 and the GaN epitaxial layer 300, when a vertical electric field is applied in the subsequent GaN epitaxial layer 300, the electrode structure can apply a positive voltage to the GaN epitaxial layer 300 close to the side of the silicon substrate 100 through the GaN low-resistance layer 240, thereby reducing the contact resistance between the external electrode and the GaN low-resistance layer 240.

[0049] Generally, there is a relatively high contact resistance between the metal material of the electrode structure and the GaN material. The relatively high contact resistance will cause a large voltage loss during the transmission of electrical signals, reducing the integrity and stability of the signals. Moreover, the relatively high contact resistance will also increase the power consumption of the α-particle detector due to the thermal effect, thereby affecting the reliability of the long-term operation of the α-particle detector. Therefore, in this application, by setting the GaN low-resistance layer 240 as a heavily Si-doped GaN low-resistance layer 240, the resistivity of the GaN material is reduced by the heavily doped Si element in the GaN low-resistance layer 240, thereby providing key support for reducing the contact resistance between the electrode structure and the GaN low-resistance layer 240. The reduction of the contact resistance between the electrode structure and the GaN low-resistance layer 240 can, in turn, reduce the voltage loss caused by the resistance during signal transmission, thereby improving the transmission efficiency and integrity of the signals. This optimized design can not only effectively reduce the power consumption and thermal effect of the α-particle detector, but also significantly enhance the sensitivity and response speed of the α-particle detector, ultimately laying a foundation for achieving high-performance detection.

[0050] As an example, the doping concentration range of the heavily doped Si element in the GaN low-resistance layer 240 is between 5 10 17 cm -3 ~1 10 20 cm -3 In this example, the doping concentration of the heavily doped Si element inside the GaN low-resistance layer 240 is 1 10 19 cm -3 .

[0051] Further, a stepped portion is provided on a side of the GaN low-resistance layer 240 away from the silicon substrate 100. The stepped portion includes a stepped upper surface and a lower surface surrounding the upper surface, and the GaN epitaxial layer 300 is formed on the upper surface. The electrode structure further includes a first electrode 410 and a second electrode 420 arranged at intervals, and the second electrode 420 is formed around the circumference of the first electrode 410. By disposing the first electrode 410 on the GaN epitaxial layer 300 and the second electrode 420 on the lower surface of the GaN low-resistance layer 240, an electric field in the vertical direction can be formed between the first electrode 410 and the second electrode 420 through an external circuit in the GaN epitaxial layer 300. Among them, the first electrode 410 is equivalent to a Schottky contact electrode and is electrically connected to the negative terminal of the external circuit, and the second electrode 420 is equivalent to an ohmic contact electrode and is electrically connected to the positive terminal of the external circuit.

[0052] As an example, the first electrode 410 is composed of a metal material with a high work function, including but not limited to any one of metal combinations such as Ni / Au, Pd / Au, or Pt / Au.

[0053] The thickness range of the first electrode 410 is between 10 nm and 200 nm. Since the first electrode 410 is located on the GaN epitaxial layer 300, the energy of the incident α particles mainly enters the GaN epitaxial layer 300 through the first electrode 410. That is to say, the lower the thickness of the first electrode 410, the smaller the incident energy loss of the α particles when passing through the first electrode 410. Thus, by limiting the thickness of the first electrode 410 to be between 10 nm and 200 nm, the incident energy loss of the α particles can be reduced, and the sensitivity of α particle detection can be further improved.

[0054] A passivation layer 500 is formed on the GaN low-resistance layer 240, covering the surface of the lower surface circuit of the GaN low-resistance layer 240 and extending upward along the side wall of the GaN epitaxial layer 300 and a part of the upper surface of the GaN epitaxial layer 300 to cover the exposed surfaces of the GaN low-resistance layer 240 and the GaN epitaxial layer 300, playing a role of passivation protection, so that the inside of the GaN epitaxial layer 300 can be protected from the external environment, such as air, moisture, dust, etc., thereby ensuring the stability of the GaN epitaxial layer 300. At the same time, the passivation layer 500 also wraps the side of the electrode structure and exposes a part of the upper surface of the first electrode 410 and the second electrode 420, so that the exposed surfaces of the first electrode 410 and the second electrode 420 can transmit electrons and holes output from the upper and lower ends of the GaN epitaxial layer 300 to the external circuit to form an electrical signal reflecting the energy of the α particles.

[0055] In some embodiments, an AlGaN graded layer 230 is further formed on the GaN high-resistance layer 220, and the AlGaN graded layer 230 is located between the GaN high-resistance layer 220 and the GaN low-resistance layer 240.

[0056] Since the GaN high-resistance layer 220 generally has a relatively higher lattice constant compared to the GaN low-resistance layer 240. Thus, an AlGaN material with a higher Al element content can better match the GaN high-resistance layer 220, reducing the stress caused by lattice mismatch. Similarly, the lattice constant of the heavily Si-doped GaN low-resistance layer 240 is usually smaller, and using an AlGaN material with a lower Al element content helps to better match the lattice of the GaN low-resistance layer 240, reducing the stress and defects in the GaN low-resistance layer 240 caused by lattice mismatch. By gradually regulating the content of the Al element in the AlGaN graded layer 230 and making the Al element content gradually transition from high to low, the lattice constants of the GaN high-resistance layer 220 and the GaN low-resistance layer 240 are effectively matched, improving the epitaxial quality of the GaN low-resistance layer 240.

[0057] In some embodiments, a GaN graded layer 250 is further formed on the GaN low-resistance layer 240, and the GaN graded layer 250 is located between the GaN low-resistance layer 240 and the GaN epitaxial layer 300. Wherein, the thickness range of the GaN graded layer 250 is between 100 nm and 1000 nm.

[0058] Since the GaN low-resistance layer 240 contains heavily doped Si elements, while the content of Si elements in the GaN epitaxial layer 300 is usually extremely low, there is a large Si element concentration difference between the GaN low-resistance layer 240 and the GaN epitaxial layer 300.

[0059] Thus, by adaptively adjusting the doping concentration of Si elements in the GaN graded layer 250, making the doping concentration of Si elements in the GaN graded layer 250 change gradually, and making the doping concentration of Si elements in the GaN graded layer 250 gradually decrease from the side close to the GaN low-resistance layer 240 to the side close to the GaN epitaxial layer 300, the GaN graded layer 250 can effectively achieve a smooth transition of the carrier concentration between the GaN low-resistance layer 240 and the GaN epitaxial layer 300, avoiding defects and instabilities caused by mutations, and improving the accuracy and stability of α-particle detection. At the same time, the gradual change of the Si element doping concentration can also relieve the stress generated by the lattice constant difference between the GaN low-resistance layer 240 and the GaN epitaxial layer 300 to a certain extent, further improving the epitaxial quality of the thick-film GaN epitaxial layer 300.

[0060] According to the embodiments of the second aspect of the present application, a method for manufacturing a gallium nitride α-particle detector is further provided, which is used to manufacture the α-particle detector described in any of the above embodiments, as Figures 1 to 3 shown, the method includes:

[0061] S1, providing a silicon substrate 100;

[0062] S2. An epitaxial stack layer is formed on the silicon substrate 100. The epitaxial stack layer includes a grading layer 210, a GaN high-resistance layer 220, an AlGaN graded layer 230, a GaN low-resistance layer 240, a GaN graded layer 250, and a GaN epitaxial layer 300 that are stacked in sequence from bottom to top.

[0063] S3. Etching is performed on the side of the epitaxial stack layer away from the silicon substrate 100 to form an epitaxial stack structure with stepped steps. The stepped steps include an upper step and a lower step. The upper step is the upper surface of the GaN epitaxial layer 300, and the lower step is the surface of the GaN low-resistance layer 240 exposed by etching.

[0064] S4. An electrode structure is formed on the epitaxial structure. The electrode structure includes a first electrode 410 and a second electrode 420. The first electrode 410 is formed on the upper step, and the second electrode 420 is formed on the lower step.

[0065] S5. A passivation layer 500 is formed on the epitaxial stack structure. The passivation layer 500 covers the stepped steps and the sides of the electrode structure, and exposes the upper surfaces of the first electrode 410 and the second electrode 420 respectively.

[0066] As an example, the first electrode 410 is a Ni / Au metal stack deposited on the surface of the GaN epitaxial layer 300 with a thickness of 50 nm. The second electrode 420 is a Ti / Al / Ni / Au metal stack deposited on the lower step of the GaN low-resistance layer 240 with a thickness of 230 nm.

[0067] It should be noted that for the details not disclosed in the preparation method of the gallium nitride alpha particle detector provided in this embodiment, please refer to the details disclosed in the gallium nitride alpha particle detector in the embodiments of this application, and will not be specifically described here.

[0068] In summary, this application provides a gallium nitride alpha particle detector and its preparation method, including a silicon substrate 100, a multi-stage intermediate layer, and a GaN epitaxial layer 300. The multi-stage intermediate layer is formed between the silicon substrate 100 and the GaN epitaxial layer 300, and the multi-stage intermediate layer at least includes a grading layer 210 with a gradually changing Al element content. By forming the grading layer 210 between the silicon substrate 100 and the GaN epitaxial layer 300, and gradually decreasing the content of Al element in the grading layer 210 from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300, the gradient regulation of the lattice constant of the grading layer 210 is realized, thereby effectively alleviating the lattice mismatch between the GaN epitaxial layer 300 and the silicon substrate 100, reducing the defect density of the GaN epitaxial layer 300, and improving its crystallization quality. Finally, a high-quality thick film GaN epitaxial layer 300 is grown on the silicon substrate 100 to realize the preparation of a gallium nitride alpha particle detector based on the silicon substrate 100.

[0069] In the descriptions of the foregoing embodiments, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc., mean 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 application. 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0070] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A gallium nitride alpha particle detector for detecting alpha particles, characterized in that: include: Silicon substrate; A multi-level intermediate layer is formed on the silicon substrate; The multi-level intermediate layer also includes a graded layer, a GaN high resistance layer, an AlGaN gradient layer, a GaN low resistance layer and a GaN gradient layer stacked in sequence from bottom to top; A GaN epitaxial layer is formed on the GaN graded layer, the GaN epitaxial layer is a thick film non-doped GaN epitaxial layer, and the thickness of the GaN epitaxial layer ranges from 10 μm to 30 μm; Among them, the graded layer at least includes an AlN layer, an AlGaN layer and a GaN layer stacked in sequence from bottom to top; the content of the Al element in the AlGaN layer changes gradually, and the content of the Al element gradually decreases from the side close to the AlN layer to the side close to the GaN layer; the content of the Al element in the AlGaN gradient layer changes gradually, and the content of the Al element gradually decreases from the side close to the GaN high resistance layer to the side close to the GaN low resistance layer; the GaN gradient layer contains Si elements with a gradient doping concentration, and the doping concentration of the Si element in the GaN gradient layer gradually decreases from the side close to the GaN low resistance layer to the side close to the GaN epitaxial layer.

2. The alpha particle detector according to claim 1, characterized in that The GaN low resistance layer contains heavily doped Si elements, and the doping concentration of the Si elements in the GaN low resistance layer ranges from 5 10 17 cm -3 ~ 1 10 20 cm -3 between.

3. The alpha particle detector according to claim 1, characterized in that The thickness of the GaN gradient layer ranges from 100 nm to 1000 nm.

4. The alpha particle detector according to claim 1, characterized in that: A step portion is provided on a side of the GaN low-resistance layer away from the silicon substrate. The step portion includes a stepped upper mesa and a lower mesa surrounding the upper mesa. The GaN epitaxial layer is formed on the upper mesa.

5. The alpha particle detector according to claim 4, characterized in that: The alpha particle detector further includes an electrode structure, which includes a first electrode and a second electrode arranged at intervals, wherein the first electrode is located on the upper table, the second electrode is located on the lower table, and the second electrode is arranged around the first electrode.

6. A method for preparing a gallium nitride alpha particle detector, used for preparing the alpha particle detector according to any one of claims 1 to 5, characterized in that: include: providing a silicon substrate; Forming an epitaxial stack layer on the silicon substrate, the epitaxial stack layer comprising a graded layer, a GaN high-resistance layer, an AlGaN gradient layer, a GaN low-resistance layer, a GaN gradient layer and a GaN epitaxial layer stacked in sequence from bottom to top; Etching is performed on a side of the epitaxial stack layer away from the silicon substrate to form an epitaxial structure with a stepped step, wherein the stepped step includes an upper step and a lower step, wherein the upper step is the upper surface of the GaN epitaxial layer, and the lower step is the surface of the GaN low-resistance layer exposed by etching; forming an electrode structure on the epitaxial structure, the electrode structure comprising a first electrode and a second electrode, the first electrode being formed on the upper step, and the second electrode being formed on the lower step; A passivation layer is formed on the epitaxial structure, wherein the passivation layer covers the stepped steps and the side edges of the electrode structure and exposes the upper surfaces of the first electrode and the second electrode respectively.

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