Gallium nitride alpha particle detector and preparation method thereof

Abstract

The invention provides a gallium nitride alpha particle detector and a preparation method thereof, the gallium nitride alpha particle detector comprises 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 comprises a grading layer with gradually changed Al element content. The grading layer is formed between the silicon substrate and the GaN epitaxial layer, and the content of the Al element in the grading layer is gradually reduced from the side close to the silicon substrate to the side close to the GaN epitaxial layer, so that the lattice constant of the grading layer is gradually regulated and controlled, the lattice mismatch between the GaN epitaxial layer and the silicon substrate is effectively relieved, the defect density of the GaN epitaxial layer is reduced, and the performance of the device is improved. And finally, growing a high-quality thick-film GaN epitaxial layer on the silicon substrate, thereby realizing the preparation of the gallium nitride alpha particle detector based on the silicon substrate.

Description

Technical Field

[0001] The present application relates to the technical field of alpha particle detection, and in particular to a gallium nitride alpha particle detector and a preparation method thereof. Background Art

[0002] Alpha particles are common particles produced during the decay of radioactive materials. They are composed of two protons and two neutrons and have high energy. Alpha particle detectors have important applications in many fields, especially in radiation monitoring, environmental protection, medical treatment, nuclear power safety, and fusion research. Alpha particle detectors can efficiently detect radioactive materials, 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 makes it show significant advantages in the field of alpha particle detection. Although gallium nitride materials have excellent physical and electrical properties, which makes them show significant advantages in the field of alpha particle detection. However, the existing gallium nitride alpha particle detectors still face many technical problems and challenges in practical applications, and it is difficult to achieve the expected high performance. At present, there is no report on high-performance gallium nitride alpha particle detectors based on silicon substrates. First, due to the large lattice mismatch and thermal expansion coefficient difference between the silicon substrate and the gallium nitride material, when the thick film GaN epitaxial layer is epitaxially grown on the silicon substrate, a large number of defects are prone to occur in the GaN epitaxial layer, and even the GaN epitaxial layer may crack. In order to solve this problem, the existing technology usually needs to introduce a buffer layer to alleviate the lattice mismatch and thermal mismatch and reduce the generation of defects. However, the traditional buffer layer process is difficult to effectively obtain high-quality thick film GaN epitaxial layers, and high-performance alpha particle detectors require the GaN epitaxial layer to be able to completely absorb the energy of alpha particles, which requires the GaN epitaxial layer to have sufficient thickness and excellent quality. Secondly, the good conductivity of the silicon substrate can easily lead to an increase in the leakage current of silicon substrate devices. The gallium nitride α-particle detector has strict requirements on the leakage current, and excessive leakage current will significantly affect the performance of the α-particle detector. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

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

[0006] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a gallium nitride alpha particle detector for detecting alpha particles, wherein the alpha particle detector comprises: Silicon substrate; A multi-level intermediate layer is formed on the silicon substrate; A GaN epitaxial layer formed on the multi-level intermediate layer; The multi-level intermediate layer at least includes a graded layer containing Al element, the content of Al element in the graded layer changes gradually, and the content of Al element decreases gradually from the side close to the silicon substrate to the side close to the GaN epitaxial layer.

[0007] Optionally, the graded layer includes at least an AlN layer, an AlGaN layer and a GaN layer stacked in sequence from bottom to top; wherein the content of the Al element in the AlGaN layer changes gradually, and the content of the Al element decreases gradually from a side close to the AlN layer to a side close to the GaN layer.

[0008] Optionally, the multi-level intermediate layer also includes 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, and the GaN high-resistance layer is formed on the graded layer, and the GaN epitaxial layer is formed on the GaN gradient layer.

[0009] Optionally, the content of Al element in the AlGaN graded layer changes gradually, and the content of Al element gradually decreases from a side close to the GaN high resistance layer to a side close to the GaN low resistance layer.

[0010] Optionally, 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.

[0011] Optionally, the GaN graded layer contains Si elements with a gradient doping concentration, and the doping concentration of the Si elements in the GaN graded layer gradually decreases from a side close to the GaN low-resistance layer to a side close to the GaN epitaxial layer.

[0012] Optionally, the thickness of the GaN graded layer ranges from 100 nm to 1000 nm, and the thickness of the GaN epitaxial layer ranges from 10 μm to 30 μm.

[0013] Optionally, 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, and the GaN epitaxial layer is formed on the upper mesa.

[0014] Optionally, 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.

[0015] To achieve the above-mentioned purpose, a second embodiment of the present application proposes a method for preparing a gallium nitride alpha particle detector, which is used to prepare any one of the above-mentioned alpha particle detectors, comprising: 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. The gallium nitride alpha particle detector and the preparation method thereof provided by the present application have at least the following beneficial effects: The present application provides a gallium nitride alpha particle detector and a preparation method thereof, comprising a silicon substrate, a multi-level intermediate layer and a GaN epitaxial layer, wherein the multi-level intermediate layer is formed between the silicon substrate and the GaN epitaxial layer, and the multi-level intermediate layer at least comprises a graded layer with a gradual change in the Al element content. By forming a graded layer between the silicon substrate and the GaN epitaxial layer, and gradually reducing the Al element content in the graded layer from the side close to the silicon substrate to the side close to the GaN epitaxial layer, a gradual change control of the lattice constant of the graded layer is achieved, 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, and finally, growing a high-quality thick-film GaN epitaxial layer on the silicon substrate, and realizing the preparation of a gallium nitride alpha particle detector based on a silicon substrate. Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which: Figure 1 It is a schematic diagram of a top view structure of a gallium nitride alpha particle detector according to an embodiment of the present application.

[0017] Figure 2 Based on Figure 1 Schematic diagram of the cross-sectional structure of a gallium nitride alpha particle detector taken along the AA' section line.

[0018] Figure 3 It is a schematic flow chart of a method for preparing a gallium nitride alpha particle detector according to an embodiment of the present application.

[0019] 100 silicon substrate; 210 graded layer; 220 GaN high resistance layer; 230 AlGaN graded layer; 240 GaN low resistance layer; 250 GaN graded layer; 300 GaN epitaxial layer; 410 first electrode; 420 second electrode; 500 passivation layer. DETAILED DESCRIPTION

[0020] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0021] 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 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 new generation alpha particle detectors. In addition, the high temperature and strong radiation resistance of gallium nitride devices give it significant advantages in the application of nuclear radiation detection.

[0022] However, in practical applications, GaN α-particle detectors still face many technical problems and challenges in preparation methods, making it difficult to achieve the expected high performance. Currently, there are no reports of high-performance GaN α-particle detectors based on silicon substrates. The main reasons are as follows: First, due to the large lattice mismatch and thermal expansion coefficient difference between silicon and GaN materials, when growing a thick GaN epitaxial layer on a silicon substrate, a large number of defects are prone to occur in the GaN epitaxial layer, and even the GaN epitaxial layer may crack. In order to solve this problem, the existing technology usually needs to introduce a buffer layer to alleviate the lattice mismatch and thermal mismatch and reduce the internal defect density of the GaN epitaxial layer. However, it is difficult for the traditional buffer layer process to effectively obtain a high-quality thick-film GaN epitaxial layer on a silicon substrate, and the high-performance gallium nitride α-particle detector requires the GaN epitaxial layer to be able to completely deposit the energy of the α particles, which requires the GaN epitaxial layer to have sufficient thickness and excellent quality. In other words, the GaN epitaxial layer is used as the effective detection area of ​​the α-particle detector to receive and deposit the α 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 a gallium nitride α-particle detector based on a silicon substrate.

[0023] Secondly, the silicon substrate has good conductivity, which can easily lead to an increase in the leakage current of silicon substrate devices. The gallium nitride α-particle detector has strict requirements on the leakage current. Excessive leakage current will also significantly affect the performance of the α-particle detector.

[0024] Based on the above problems, an embodiment of the present application provides a gallium nitride alpha particle detector and a method for preparing the same. The alpha particle detector sets a multi-level intermediate layer between the silicon substrate and the GaN epitaxial layer, and utilizes the multi-level intermediate layer to improve the epitaxial quality of the GaN epitaxial layer, while significantly reducing the leakage current between the silicon substrate and the GaN epitaxial layer, thereby realizing the preparation of a gallium nitride alpha particle detector based on a silicon substrate.

[0025] According to the first aspect of the present application, a gallium nitride alpha particle detector is provided, such as Figure 1 and Figure 2 As 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. The multi-level intermediate layer includes a graded 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 stacked in sequence from bottom to top, and the GaN epitaxial layer 300 is formed on the GaN graded layer 250. The GaN epitaxial layer 300 is a thick film non-doped GaN epitaxial layer 300, and the thickness of the GaN epitaxial layer 300 can range from 10 μm to 30 μm.

[0026] It can be understood that the alpha particle detector provided in the present application is used to detect the incident energy of alpha particles. When the incident alpha particles enter the GaN epitaxial layer 300, they can generate a large number of electron-hole pairs by Coulomb interaction with the shell electrons of the atoms in the GaN epitaxial layer 300. Therefore, 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 in a direction under the action of the electric field and generate corresponding electrical signals. By receiving the electrical signals and combining with the energy spectrum analysis system, the incident energy of the alpha particles in the environment can be calculated. The present application forms a multi-level intermediate layer between the silicon substrate 100 and the GaN epitaxial layer 300, and utilizes the multi-level intermediate layer to reduce the lattice mismatch and thermal mismatch between the silicon substrate 100 and the GaN epitaxial layer 300, 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.

[0027] Furthermore, the multi-level intermediate layer may include at least a graded layer 210 , wherein the graded layer 210 contains Al elements with a gradient content, and the content of the Al element gradually decreases from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300 .

[0028] 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 formed on the silicon substrate 100, the epitaxially formed GaN epitaxial layer 300 will have a high defect density, and even directly cause the formed GaN epitaxial layer 300 to crack. However, the present application forms a graded layer 210 between the silicon substrate 100 and the GaN epitaxial layer 300, and gradually reduces the content of the Al element in the graded layer 210 from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300. The Al element with a gradually changing content in the graded layer 210 is used to achieve a gradual regulation of the lattice constant of the graded layer 210, 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.

[0029] As an example, the graded layer 210 includes at least an AlN layer, an AlGaN layer and a GaN layer stacked sequentially from bottom to top, wherein the content of Al in the AlGaN layer changes gradually, and the content of Al decreases gradually from the side close to the AlN layer to the side close to the GaN layer.

[0030] The hierarchical layer 210 is set to be an AlN layer, an AlGaN layer, and a GaN layer stacked in sequence from bottom to top, so that the lattice constant of the hierarchical layer 210 can 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, the present application also sets the AlGaN layer to have a gradual change in the content of the Al element, and by regulating the Al content in a graded manner, the lattice constant of the AlGaN layer gradually transitions from close to the AlN layer to close to the GaN layer, so as to more effectively reduce the lattice mismatch caused by the difference in lattice constants, reduce the internal defect density of the GaN layer, and improve the crystal 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 gradual change in 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.

[0031] Furthermore, a GaN high resistance layer 220 is provided between the graded layer 210 and the GaN epitaxial layer 300. By forming the GaN high resistance layer 220 on the graded 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 alpha particle detector. As an example, the GaN high resistance layer 220 is an iron-doped GaN high resistance layer 220, and the resistance of the GaN high resistance layer 220 is increased by doping the GaN high resistance layer 220 with iron.

[0032] It should be noted that the above-mentioned substrate may include but is not limited to a silicon substrate 100 .

[0033] In some embodiments, a GaN low resistance layer 240 , as well as an electrode structure and a passivation layer 500 located on the GaN low resistance layer 240 are further disposed on the GaN high resistance layer 220 .

[0034] The GaN low resistance layer 240 is a heavily Si-doped GaN low resistance layer 240. By forming a GaN low resistance layer 240 of a certain thickness between the GaN high resistance layer 220 and the GaN epitaxial layer 300, when a vertical electric field is subsequently applied in the 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.

[0035] The metal material of the electrode structure and the GaN material generally have a high contact resistance. The high contact resistance will cause a large voltage loss in the transmission process of the electrical signal, reduce the integrity and stability of the signal, and the 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, the present application sets the GaN low resistance layer 240 as a heavily Si-doped GaN low resistance layer 240, and uses the heavily doped Si element of the GaN low resistance layer 240 to reduce the resistivity of the GaN material, thereby providing key support for reducing the contact resistance between the electrode structure and the GaN low resistance layer 240. The reduction in the contact resistance between the electrode structure and the GaN low resistance layer 240 can reduce the voltage loss caused by resistance during signal transmission, thereby improving the transmission efficiency and integrity of the signal. 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 the foundation for achieving high-performance detection.

[0036] As an example, the doping concentration of the heavily doped Si element in the GaN low resistance layer 240 ranges from 5 10 17 cm -3 ~1 10 20 cm -3 In this example, the doping concentration of the heavily doped Si element in the GaN low resistance layer 240 is 1 10 19 cm -3 .

[0037] Furthermore, a step portion is provided on the side of the GaN low-resistance layer 240 away from the silicon substrate 100, and the step portion includes a stepped upper table and a lower table surrounding the upper table, and the GaN epitaxial layer 300 is formed on the upper table. The electrode structure also includes a first electrode 410 and a second electrode 420 arranged at intervals, and the second electrode 420 is formed around the periphery of the first electrode 410. By arranging the first electrode 410 on the GaN epitaxial layer 300 and the second electrode 420 on the lower table of the GaN low-resistance layer 240, the first electrode 410 and the second electrode 420 can form an electric field in a vertical direction on the GaN epitaxial layer 300 through an external circuit. Among them, the first electrode 410 is equivalent to a Schottky contact electrode, which is electrically connected to the negative end of the external circuit, and the second electrode 420 is equivalent to an ohmic contact electrode, which is electrically connected to the positive end of the external circuit.

[0038] 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 Ni / Au, Pd / Au or Pt / Au metal combinations.

[0039] The thickness of the first electrode 410 is in the range of 10 nm to 200 nm. Since the first electrode 410 is located on the GaN epitaxial layer 300, the energy of the incident α-particle mainly enters the GaN epitaxial layer 300 through the first electrode 410. In other words, the lower the thickness of the first electrode 410, the smaller the incident energy loss of the α-particle when passing through the first electrode 410. Therefore, by limiting the thickness of the first electrode 410 to be between 10 nm and 200 nm, the incident energy loss of the α-particle can be reduced, and the sensitivity of α-particle detection can be further improved.

[0040] The passivation layer 500 is formed on the GaN low-resistance layer 240, covers the surface of the lower mesa circuit of the GaN low-resistance layer 240, and extends upward to the side wall of the GaN epitaxial layer 300 and part of the upper surface of the GaN epitaxial layer 300, so as to cover the exposed surface of the GaN low-resistance layer 240 and the GaN epitaxial layer 300, and play a role of passivation protection, so that the inside of the GaN epitaxial layer 300 can be protected from the influence of the external environment, such as air, moisture, dust, etc., so as to ensure the stability of the GaN epitaxial layer 300. At the same time, the passivation layer 500 also covers the side of the electrode structure and exposes part of the upper surface of the first electrode 410 and the second electrode 420, so that the exposed surface of the first electrode 410 and the second electrode 420 can transmit the output electrons-holes at 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 alpha particles.

[0041] 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 .

[0042] Since the GaN high resistance layer 220 generally has a relatively high lattice constant compared to the GaN low resistance layer 240. Therefore, the use of AlGaN materials with a higher Al content can better match the GaN high resistance layer 220 and reduce the stress caused by lattice mismatch. Similarly, the lattice constant of the heavily silicon-doped GaN low resistance layer 240 is generally small, and the use of AlGaN materials with a lower Al content helps to better match the lattice of the GaN low resistance layer 240, reducing the stress and defects caused by lattice mismatch in the GaN low resistance layer 240. By gradually regulating the content of the Al element in the AlGaN gradient layer 230 and gradually transitioning the Al content from high to low, the lattice constants of the GaN high resistance layer 220 and the GaN low resistance layer 240 are effectively matched, and the epitaxial quality of the GaN low resistance layer 240 is improved.

[0043] In some embodiments, a GaN gradient layer 250 is further formed on the GaN low resistance layer 240, and the GaN gradient layer 250 is located between the GaN low resistance layer 240 and the GaN epitaxial layer 300. The thickness of the GaN gradient layer 250 is in the range of 100 nm to 1000 nm. Since the GaN low-resistance layer 240 contains heavily doped Si elements, and the content of Si elements in the GaN epitaxial layer 300 is usually very low, there is a large Si element concentration difference between the GaN low-resistance layer 240 and the GaN epitaxial layer 300 .

[0044] Thus, by adaptively adjusting the doping concentration of Si element in GaN gradient layer 250, the doping concentration of Si element in GaN gradient layer 250 is gradually changed, and the doping concentration of Si element in GaN gradient layer 250 is gradually reduced from the side close to GaN low resistance layer 240 to the side close to GaN epitaxial layer 300, so that GaN gradient layer 250 can effectively realize the smooth transition of carrier concentration between GaN low resistance layer 240 and GaN epitaxial layer 300, avoid defects and instability caused by mutation, and improve the accuracy and stability of alpha particle detection. At the same time, the gradual change of Si element doping concentration can also alleviate the stress caused by the difference in lattice constants between GaN low resistance layer 240 and GaN epitaxial layer 300 to a certain extent, and further improve the epitaxial quality of thick film GaN epitaxial layer 300.

[0045] According to the second aspect of the present application, a method for preparing a gallium nitride alpha particle detector is also provided, which is used to prepare the alpha particle detector described in any of the above embodiments, such as Figure 1~Figure 3 As shown, the method includes: S1, providing a silicon substrate 100; S2, forming an epitaxial stack layer on the silicon substrate 100, the epitaxial stack layer including a graded 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 stacked in sequence from bottom to top; 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 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 300, and the lower step is the surface of the GaN low-resistance layer 240 exposed by etching; S4, forming an electrode structure on the epitaxial structure, the electrode structure including 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; S5, forming a passivation layer 500 on the epitaxial stack structure, the passivation layer 500 covers the stepped steps and the side of the electrode structure, and exposes the upper surfaces of the first electrode 410 and the second electrode 420 respectively.

[0046] As an example, the first electrode 410 is a Ni / Au metal stack with a thickness of 50 nm deposited on the surface of the GaN epitaxial layer 300. The second electrode 420 is a Ti / Al / Ni / Au metal stack with a thickness of 230 nm deposited on the lower step of the GaN low-resistance layer 240.

[0047] It should be noted that for details not disclosed in the method for preparing 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 the present application, and no further details will be given here.

[0048] In summary, the present application provides a gallium nitride alpha particle detector and a preparation method thereof, comprising a silicon substrate 100, a multi-level intermediate layer and a GaN epitaxial layer 300, wherein the multi-level intermediate layer is formed between the silicon substrate 100 and the GaN epitaxial layer 300, and the multi-level intermediate layer at least comprises a graded layer 210 with a gradient Al element content. By forming a graded layer 210 between the silicon substrate 100 and the GaN epitaxial layer 300, and gradually reducing the Al element content in the graded layer 210 from the side close to the silicon substrate 100 to the side close to the GaN epitaxial layer 300, a gradual regulation of the lattice constant of the graded layer 210 is achieved, 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 crystal quality, and finally, growing a high-quality thick film GaN epitaxial layer 300 on the silicon substrate 100, and preparing a gallium nitride alpha particle detector based on the silicon substrate 100.

[0049] In the description of the aforementioned embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction 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, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they contradict each other.

[0050] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and 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; A GaN epitaxial layer formed on the multi-level intermediate layer; The multi-level intermediate layer at least includes a graded layer containing Al element, the content of Al element in the graded layer changes gradually, and the content of Al element decreases gradually from the side close to the silicon substrate to the side close to the GaN epitaxial layer.

2. The alpha particle detector according to claim 1, characterized in that: The graded 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 a side close to the AlN layer to a side close to the GaN layer.

3. The alpha particle detector according to claim 2, characterized in that: The multi-level intermediate layer also includes 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, and the GaN high-resistance layer is formed on the graded layer, and the GaN epitaxial layer is formed on the GaN gradient layer.

4. The alpha particle detector according to claim 3, characterized in that: The content of Al element in the AlGaN graded layer changes gradually, and the content of Al element decreases gradually from a side close to the GaN high resistance layer to a side close to the GaN low resistance layer.

5. The alpha particle detector according to claim 3, 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.

6. The alpha particle detector according to claim 3, characterized in that: The GaN graded layer contains Si elements with a gradually changing doping concentration, and the doping concentration of the Si elements in the GaN graded layer gradually decreases from a side close to the GaN low-resistance layer to a side close to the GaN epitaxial layer.

7. The alpha particle detector according to claim 3, characterized in that The thickness of the GaN gradient layer ranges from 100 nm to 1000 nm, and the thickness of the GaN epitaxial layer ranges from 10 μm to 30 μm.

8. The alpha particle detector according to claim 3, 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.

9. The alpha particle detector according to claim 8, 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.

10. A method for preparing a gallium nitride alpha particle detector, used for preparing the alpha particle detector according to any one of claims 2 to 9, 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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