AlN-based RF power transistors with high thermal conductivity BeO passivation and their fabrication method

Abstract

This invention discloses an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation and its fabrication method, comprising: a substrate layer, an AlN nucleation layer, a GaN channel layer, and an AlN barrier layer stacked sequentially from bottom to top; a source and a drain located at opposite ends of the upper surface of the AlN barrier layer; a first passivation layer located on the upper surface of the AlN barrier layer between the source and drain; a second passivation layer located on the upper surface of the first passivation layer; wherein the second passivation layer is made of high thermal conductivity material BeO; a T-type gate penetrating the second passivation layer to the upper surface of the first passivation layer, and overlapping a portion of the upper surface of the second passivation layer, and close to the source. This invention has significant advantages in improving thermal conductivity, increasing device breakdown voltage and power density, reducing current collapse, lowering device operating temperature, and enhancing device operating stability, indicating broad application prospects in high-frequency and high-power fields.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation and its fabrication method. Background Technology

[0002] Radio frequency (RF) power transistors are widely used in wireless communication, radar systems, and various high-frequency electronic devices. With the rapid development of new energy vehicles, 5G communication, aerospace, and other fields, there are increasing demands on electronic devices, including integration, miniaturization, high voltage and high power, and low loss. This places increasingly higher demands on the performance of RF power devices, especially in terms of power handling capabilities and operating frequencies. In high-voltage, high-power scenarios, RF power transistors generate a significant amount of heat. If this heat cannot be effectively dissipated, the device temperature will rise, affecting its performance and shortening its lifespan.

[0003] GaN, a third-generation semiconductor material, possesses superior material properties such as a wide bandgap, high electron drift velocity, and high breakdown field strength. GaN-based radio frequency (RF) power devices, fabricated using GaN as a substrate, are widely used in modern communication and radar systems due to their excellent electrical and thermal properties. However, RF power devices are mostly used in applications requiring high power, high frequency performance, high efficiency, and high temperature resistance, placing stringent requirements on heat dissipation, high temperature resistance, and breakdown voltage. Currently, GaN-based RF power transistors face the following challenges:

[0004] (1) Existing research results indicate that, in most cases, the breakdown of GaN-based RF power transistors under high voltage conditions is due to the punch-through effect caused by a large number of electrons crossing the barrier layer below the gate depletion region. For existing GaN-based RF power transistors, electrons are well confined by the barrier height between the AlGaN barrier layer above the GaN channel layer and the channel. However, the barrier height generated by the AlGaN barrier layer depends heavily on the Al content. If the Al content of the barrier layer is low, the lower barrier will result in weaker carrier confinement, which may cause the device to break down even at lower voltages.

[0005] (2) Although GaN-based RF power transistors currently use SiC substrates with good thermal conductivity for heat dissipation, the low thermal conductivity of the single-layer SiN passivation layer results in insufficient thermal conductivity of the GaN-based RF power transistors when operating at high power. This leads to heat accumulation in GaN-based RF power transistors under normal operating conditions. Poor heat dissipation limits the power density of the device, which in turn affects the overall efficiency and performance of the transistor. As a result, GaN-based RF power transistors are not suitable for applications in high-frequency, high-voltage, and high-power scenarios.

[0006] (3) At present, GaN-based radio frequency power transistors are surface devices. Their conductive channels are only tens of nanometers away from the device surface. Channel carriers are easily affected by surface states, resulting in current collapse, which causes device reliability problems and affects the overall efficiency and performance of the device.

[0007] Therefore, designing RF power transistors that simultaneously possess high voltage resistance, high power, high heat dissipation, and high reliability has become a key research direction. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0009] In a first aspect, embodiments of the present invention provide an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, the AlN-based radio frequency power transistor comprising:

[0010] The substrate layer, AlN nucleation layer, GaN channel layer, and AlN barrier layer are stacked sequentially from bottom to top.

[0011] The source and drain are located at opposite ends of the upper surface of the AlN barrier layer;

[0012] The first passivation layer is located on the upper surface of the AlN barrier layer between the source and the drain;

[0013] A second passivation layer is located on the upper surface of the first passivation layer; wherein the second passivation layer is a high thermal conductivity material BeO;

[0014] The T-shaped gate extends through the second passivation layer to the upper surface of the first passivation layer, overlaps a portion of the upper surface of the second passivation layer, and is close to the source electrode.

[0015] In one embodiment of the present invention, the AlN-based radio frequency power transistor further includes an AlGaN buffer layer or a GaN buffer layer; the AlGaN buffer layer or the GaN buffer layer is located between the GaN channel layer and the AlN barrier layer.

[0016] In one embodiment of the present invention, the substrate layer is one of SiC substrate, diamond substrate, and sapphire substrate.

[0017] In one embodiment of the present invention, the material of the first passivation layer is one of SiN, Al2O3, and SiO2.

[0018] In one embodiment of the present invention, the thickness of the first passivation layer is 25 nm to 35 nm.

[0019] In one embodiment of the present invention, the thickness of the second passivation layer is 20 nm to 50 nm.

[0020] Secondly, embodiments of the present invention provide a method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, the method comprising:

[0021] Obtain the substrate layer and clean the substrate layer;

[0022] An AlN nucleation layer is grown on the substrate.

[0023] A GaN channel layer is grown on the AlN nucleation layer;

[0024] An AlN barrier layer is grown on the GaN channel layer;

[0025] A first passivation layer is formed on the AlN barrier layer;

[0026] A second passivation layer is grown on the first passivation layer; wherein the second passivation layer is a high thermal conductivity material BeO;

[0027] The second passivation layers at both ends of the device are etched up to the upper surface of the AlN barrier layer, so as to deposit ohmic metal on the AlN barrier layer at one end of the device to form the source, and deposit ohmic metal on the AlN barrier layer at the other end to form the drain.

[0028] The second passivation layer near the source is etched until the upper surface of the first passivation layer is formed to create a gate groove. Gate metal is deposited in the gate groove and on part of the upper surface of the second passivation layer to form a T-shaped gate.

[0029] In one embodiment of the present invention, a first passivation layer is grown on the AlN barrier layer, comprising:

[0030] A first passivation layer with a thickness of 25 nm to 35 nm was grown on the AlN barrier layer using the PECVD process.

[0031] In one embodiment of the present invention, growing a second passivation layer on the first passivation layer includes:

[0032] Using the ALD process, a second passivation layer with a thickness of 20 nm to 50 nm is grown on the first passivation layer.

[0033] In one embodiment of the present invention, before growing an AlN barrier layer on the GaN channel layer, the method further includes:

[0034] An AlGaN buffer layer or a GaN buffer layer is grown on the GaN channel layer to grow an AlN barrier layer on the AlGaN buffer layer or the GaN buffer layer.

[0035] The beneficial effects of this invention are:

[0036] The AlN-based RF power transistor based on high thermal conductivity BeO passivation proposed in this invention has significant advantages in improving thermal conductivity, increasing device breakdown voltage and power density, reducing current collapse, lowering device operating temperature, and enhancing device operating stability, indicating broad application prospects in high-frequency and high-power fields. Unlike traditional GaN-based RF power transistors, the AlN-based RF power transistor proposed in this invention replaces the AlGaN barrier layer in traditional GaN-based RF power transistors with an AlN barrier layer. Furthermore, it employs a double passivation layer combining a first passivation layer and a second passivation layer. This avoids the problem of insufficient thermal conductivity in traditional GaN-based RF power transistors, which only include a single SiN passivation layer, failing to meet high power and high frequency requirements. Because a high thermal conductivity material, BeO, is grown on top of the first passivation layer as the second passivation layer, it effectively dissipates heat during power transistor operation, preventing heat accumulation. Simultaneously, it avoids the lattice mismatch problem caused by directly growing BeO on the AlN barrier layer. The combination of the first and second passivation layers achieves excellent heat dissipation in the AlN-based RF power transistor, thereby improving performance in high power and high frequency scenarios. In summary, this invention innovatively introduces BeO, a material with high thermal conductivity, into AlN-based RF power transistors. By combining the superior properties of BeO with AlN-based RF power transistors, it is possible to achieve higher power and higher frequency processing capabilities while solving the current technology's shortcomings in heat dissipation performance. This research direction not only has important theoretical significance but also has a profound impact on promoting the advancement and application of RF device technology.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of another AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation provided in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of a fabrication method for an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, provided by an embodiment of the present invention.

[0041] Figures 4a to 4h This is a schematic diagram of the corresponding structure during the fabrication process of the AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation provided in the embodiments of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0043] The inventors discovered that AlN material, as an AlGaN material with 100% Al composition, not only has an ultra-wide direct bandgap (6.2 eV), high thermal conductivity, high resistivity, high breakdown field strength, excellent piezoelectric properties, good optical properties, and high temperature resistance, but also has high lattice constant matching, thermal matching, and compatibility with GaN. Therefore, radio frequency power transistors using AlN as a barrier layer can greatly improve the device's voltage withstand capability and high-frequency performance, and can be better applied in high-power, high-frequency radio frequency devices. However, directly replacing the AlGaN barrier layer with an AlN barrier layer in RF power transistors still cannot meet application requirements under high power and high frequency conditions. This is because, in high power and high frequency scenarios, while using a single-layer SiN dielectric layer or other ceramic materials as a passivation layer for heat dissipation can improve the device's heat dissipation performance to some extent, current passivation layer technologies are mostly silicon-based passivation or silicon nitride passivation. These materials perform well in terms of electrical insulation, but their thermal conductivity is still not high enough, leading to heat accumulation, excessively high operating temperatures, and instability. This can damage the device itself or even cause the entire module circuit to fail, thus limiting the heat dissipation effect and operational stability in high-power applications. Therefore, finding effective passivation and heat dissipation materials to optimize device heat dissipation has become a key research direction.

[0044] To address this issue, the inventors further discovered that BeO (beryllium oxide), a material with high thermal conductivity, can serve as an ideal passivation layer material due to its excellent thermal conductivity and electrical insulation properties. BeO's thermal conductivity can reach several hundred watts per meter per Kelvin (W / m·K), far exceeding that of traditional materials. This allows BeO to effectively and rapidly transfer the heat generated by the device to the substrate or external heat dissipation system, thereby reducing the device's operating temperature. Furthermore, BeO possesses good dielectric properties, effectively isolating current, preventing breakdown, and improving the long-term stability and stability of the device. However, the inventors found that directly growing BeO on the AlGaN barrier layer in GaN-based RF power devices results in a smaller lattice mismatch between AlGaN and BeO, achieving a passivation effect and good heat dissipation. Conversely, directly growing BeO on the AlN barrier layer in Al-based RF power devices leads to a larger lattice mismatch between the nitride and oxide, causing lattice distortion and affecting interface quality and passivation performance. To address this issue, the inventors added a layer of material such as SiN between the AlN barrier layer and BeO as a first passivation layer. This not only avoids the lattice mismatch problem caused by direct contact between BeO and the AlN barrier layer, but also addresses the surface charge of the device and reduces current collapse. Based on this, BeO is then used as a second passivation layer, which not only serves as a passivation layer but also provides heat dissipation with high thermal conductivity. This makes it possible to design AlN-based RF power transistors for high-power, high-frequency applications.

[0045] Based on the above research, this invention proposes an AlN-based radio frequency power transistor with high thermal conductivity BeO passivation and its fabrication method.

[0046] Firstly, please see Figure 1 This invention provides an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, the AlN-based radio frequency power transistor comprising:

[0047] The substrate layer, AlN nucleation layer, GaN channel layer, and AlN barrier layer are stacked sequentially from bottom to top.

[0048] The source and drain are located at opposite ends of the upper surface of the AlN barrier layer;

[0049] The first passivation layer is located on the upper surface of the AlN barrier layer between the source and drain.

[0050] The second passivation layer is located on the upper surface of the first passivation layer; wherein, the second passivation layer is a high thermal conductivity material BeO;

[0051] The T-shaped gate extends through the second passivation layer to the upper surface of the first passivation layer, overlaps a portion of the upper surface of the second passivation layer, and is close to the source.

[0052] In embodiments of the present invention, the substrate layer can be one of SiC substrate, diamond substrate, or sapphire substrate.

[0053] In this embodiment of the invention, the thickness of the AlN nucleation layer is 45nm to 55nm, more preferably 50nm; the thickness of the GaN channel layer is 90nm to 110nm, more preferably 100nm; and the thickness of the AlN barrier layer is 15nm to 25nm, more preferably 20nm. This embodiment of the invention uses an AlN barrier layer, which increases the barrier height between the channel layer and the barrier layer, improving the barrier height during electron penetration and enhancing the confinement of charge carriers, thereby improving the device's high-voltage withstand capability. By increasing the barrier height between the barrier layer and the GaN channel layer, the concentration of 2DEG generated by spontaneous polarization and piezoelectric polarization is increased, thereby increasing the device's current density and power density, ultimately fabricating an AlN-based radio frequency power transistor applicable to high power and high frequency applications.

[0054] In this embodiment of the invention, the first passivation layer is made of one of SiN, Al2O3, or SiO2; the thickness of the first passivation layer is 25 nm to 35 nm. In this embodiment of the invention, the second passivation layer is made of BeO, a material with high thermal conductivity; the thickness of the second passivation layer is 20 nm to 50 nm. This embodiment of the invention employs a double-layer passivation structure with a first passivation layer and a second passivation layer. The first passivation layer reduces the lattice mismatch between the second passivation layer and the AlN barrier layer. Simultaneously, the double-layer passivation significantly improves heat dissipation performance and reduces the impact of current collapse on the device, thereby improving the device's operational reliability.

[0055] In this embodiment of the invention, the gate material can be Ni / Au (45nm / 200nm); the source and drain materials can be Ti / Al / Ni / Au (20nm / 120nm / 45nm / 55nm). Figure 1 In the diagram, S represents the source, D represents the drain, and G represents the gate.

[0056] Please see Figure 2 In this embodiment of the invention, the AlN-based radio frequency power transistor further includes an AlGaN buffer layer or a GaN buffer layer; the AlGaN buffer layer or GaN buffer layer is located between the GaN channel layer and the AlN barrier layer; the thickness of the AlGaN buffer layer or GaN buffer layer is 100nm to 200nm, more preferably 180nm. Adding a buffer layer between the substrate layer and the GaN channel layer can reduce lattice mismatch and stress mismatch caused by the difference between the GaN and substrate materials, effectively reduce dislocation density, and prevent current leakage from the substrate during device operation.

[0057] This invention, based on the combination of AlN-based RF power transistors and BeO material as the top passivation layer, has broad application prospects: First, in 5G and future 6G communication technologies, the demand for high-frequency, high-power RF devices is constantly increasing. The structure proposed in this invention can effectively improve the power handling capability and thermal management performance of the device, thereby meeting the stringent requirements for RF components in high-speed communication. Second, with the rapid development of emerging applications such as the Internet of Things, smart homes, and autonomous driving, the integration and reliability of RF power devices are particularly important. The structure proposed in this invention, by optimizing thermal management, reducing device current collapse, and improving device stability, can achieve more reliable signal transmission and reduce system failure rates in these fields. Finally, high-end application scenarios such as aerospace, automotive electronics, and radar systems have extremely high performance requirements for RF devices. The structure proposed in this invention can maintain excellent performance under high voltage, high frequency, and high power conditions, which is helpful for practical applications.

[0058] In summary, the AlN-based RF power transistor based on high thermal conductivity BeO passivation proposed in this invention has significant advantages in improving thermal conductivity, increasing device breakdown voltage and power density, reducing current collapse, lowering device operating temperature, and enhancing device operating stability, indicating broad application prospects in high-frequency and high-power fields. Unlike traditional GaN-based RF power transistors, the AlN-based RF power transistor proposed in this invention replaces the AlGaN barrier layer in traditional GaN-based RF power transistors with an AlN barrier layer. It also employs a double passivation layer combining a first passivation layer and a second passivation layer. This avoids the problem of insufficient thermal conductivity in traditional GaN-based RF power transistors, which only include a single SiN passivation layer, failing to meet high power and high frequency requirements. Because a high thermal conductivity material, BeO, is grown on top of the first passivation layer as the second passivation layer, it effectively dissipates heat during power transistor operation, preventing heat accumulation. Simultaneously, it avoids the lattice mismatch problem caused by directly growing BeO on the AlN barrier layer. The combination of the first and second passivation layers achieves excellent heat dissipation in the AlN-based RF power transistor, thereby improving performance in high power and high frequency scenarios. In summary, the embodiments of this invention innovatively introduce BeO, a material with high thermal conductivity, into AlN-based RF power transistors. By combining the superior properties of BeO with AlN-based RF power transistors, higher power and higher frequency processing capabilities can be achieved while solving the shortcomings of current technologies in heat dissipation performance. This research direction not only has important theoretical significance, but also has a profound impact on promoting the progress and application of RF device technology.

[0059] Secondly, please see Figure 3 This invention provides a method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation. The method includes:

[0060] S10. Obtain the substrate layer and clean the substrate layer.

[0061] In this embodiment of the invention, a substrate layer is first obtained, which can be a SiC substrate, a diamond substrate, or a sapphire substrate. Then, the obtained substrate layer is cleaned. Specifically, the substrate layer is sequentially immersed in acetone, ethanol, and deionized water for ultrasonic cleaning for 10 minutes, and then dried with a nitrogen gun.

[0062] S20. An AlN nucleation layer is grown on the substrate.

[0063] In this embodiment of the invention, the cleaned substrate is immersed in HF (hydrofluoric acid) solution for 30 seconds, cleaned with an organic solvent and dried. The substrate is then placed in the reaction chamber of an MOCVD (Metal-organic Chemical Vapor Deposition) system. Using the MOCVD process, an AlN nucleation layer with a thickness of 45 nm to 55 nm is epitaxially grown on the substrate; more preferably, an AlN nucleation layer with a thickness of 50 nm is epitaxially grown. Figure 4a As shown.

[0064] S30. Grow a GaN channel layer on the AlN nucleation layer.

[0065] In this embodiment of the invention, a Ga source, hydrogen, and ammonia are simultaneously introduced into the MOCVD reaction chamber to grow a GaN channel layer with a thickness of 90 nm to 110 nm on the AlN nucleation layer, more preferably a GaN channel layer with a thickness of 100 nm. Figure 4b As shown.

[0066] S40. An AlN barrier layer is grown on the GaN channel layer.

[0067] In this embodiment of the invention, an Al source, hydrogen, and ammonia are simultaneously introduced into the MOCVD reaction chamber to grow an AlN barrier layer with a thickness of 15 nm to 25 nm on the GaN channel layer, more preferably, an AlN barrier layer with a thickness of 20 nm is grown. Figure 4c As shown, remove it after growth is complete.

[0068] It should be noted that before growing the AlN barrier layer on the GaN channel layer, the process may further include: growing an AlGaN buffer layer or GaN buffer layer with a thickness of 100nm to 200nm on the GaN channel layer, more preferably growing an AlGaN buffer layer or GaN buffer layer with a thickness of 180nm, to grow an AlN barrier layer on the AlGaN buffer layer or GaN buffer layer. Taking the GaN buffer layer as an example: simultaneously introducing a Ga source, hydrogen, and ammonia into the MOCVD reaction chamber, growing a GaN buffer layer with a thickness of 100nm to 200nm on the GaN channel layer, more preferably growing a GaN buffer layer with a thickness of 180nm, such as... Figure 4d As shown.

[0069] S50, the first passivation layer is generated on the AlN barrier layer.

[0070] In this embodiment of the invention, the device structure obtained in S40 is placed in a PECVD (Plasma Enhanced Chemical Vapor Deposition) reaction chamber, and a first passivation layer with a thickness of 25 nm to 35 nm is deposited at a high temperature of 400 °C using the PECVD process. More preferably, a first passivation layer with a thickness of 30 nm is deposited. Figure 4e As shown. The material of the first passivation layer can be SiN, Al2O3, or SiO2, and it is removed after growth.

[0071] S60. A second passivation layer is grown on the first passivation layer; wherein the second passivation layer is BeO, a material with high thermal conductivity.

[0072] In this embodiment of the invention, the device structure obtained in S50 is placed in an ALD (Atomic Layer Deposition) reaction chamber. Using the ALD process, a high thermal conductivity material BeO with a thickness of 20nm to 50nm is deposited at 300°C to form a second passivation layer. More preferably, a high thermal conductivity material BeO with a thickness of 45nm is deposited to form the second passivation layer. Figure 4f As shown, the thickness and quality of the grown high thermal conductivity material BeO can be precisely controlled through the ALD process.

[0073] S70. Etch the second passivation layer at both ends of the device down to the upper surface of the AlN barrier layer, so as to deposit ohmic metal on the AlN barrier layer at one end of the device to form the source, and deposit ohmic metal on the AlN barrier layer at the other end to form the drain.

[0074] In this embodiment of the invention, a mask is fabricated on the second passivation layer. Using this mask, the second passivation layers at both ends of the device obtained in S60 are etched down to the upper surface of the AlN barrier layer. Then, Ti / Al / Ni / Au (20nm / 120nm / 45nm / 55nm) is deposited on the AlN barrier layer using an electron beam evaporation apparatus. This allows ohmic metal to be deposited on the AlN barrier layer at one end of the device to form the source, and ohmic metal to be deposited on the AlN barrier layer at the other end to form the drain. Figure 4g As shown. At this point, simultaneous etching achieves mesa isolation.

[0075] S80. Etch the second passivation layer near the source electrode until the upper surface of the first passivation layer is formed to create a gate groove. Deposit gate metal in the gate groove and on part of the upper surface of the second passivation layer to form a T-shaped gate.

[0076] In this embodiment of the invention, a mask is fabricated on the second passivation layer near the source electrode. Using this mask, the second passivation layer is etched until a gate groove is formed on the upper surface of the first passivation layer. Then, an electron beam evaporation apparatus is used to deposit gate metal, such as Ni / Au (45nm / 200nm), on a portion of the second passivation layer within and on both sides of the gate groove, forming a T-shaped gate. Figure 4h As shown.

[0077] The present invention provides a preparation method based on the structure proposed in the first aspect. The manufacturing process is simple, economical, and suitable for large-scale commercial production and application.

[0078] As for the preparation method embodiment of the second aspect, since it is basically similar to the structural embodiment of the first aspect, the description is relatively simple. For relevant details, please refer to the description of the structural embodiment of the first aspect.

[0079] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0080] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the specification and accompanying drawings, will understand and implement other variations of the disclosed embodiments in carrying out the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0081] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, characterized in that, The AlN-based radio frequency power transistor includes: The substrate layer, AlN nucleation layer, GaN channel layer, and AlN barrier layer are stacked sequentially from bottom to top. The source and drain are located at opposite ends of the upper surface of the AlN barrier layer; The first passivation layer is located on the upper surface of the AlN barrier layer between the source and the drain; A second passivation layer is located on the upper surface of the first passivation layer; wherein the second passivation layer is a high thermal conductivity material BeO; The T-shaped gate extends through the second passivation layer to the upper surface of the first passivation layer, overlaps a portion of the upper surface of the second passivation layer, and is close to the source electrode.

2. The AlN-based RF power transistor based on high thermal conductivity BeO passivation according to claim 1, characterized in that, The AlN-based radio frequency power transistor further includes an AlGaN buffer layer or a GaN buffer layer; the AlGaN buffer layer or the GaN buffer layer is located between the GaN channel layer and the AlN barrier layer.

3. The AlN-based RF power transistor based on high thermal conductivity BeO passivation according to claim 1, characterized in that, The substrate is one of SiC substrate, diamond substrate, and sapphire substrate.

4. The AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation according to claim 1, characterized in that, The material of the first passivation layer is one of SiN, Al2O3, and SiO2.

5. The AlN-based RF power transistor based on high thermal conductivity BeO passivation according to claim 1, characterized in that, The thickness of the first passivation layer is 25nm to 35nm.

6. The AlN-based RF power transistor based on high thermal conductivity BeO passivation according to claim 1, characterized in that, The thickness of the second passivation layer is 20nm to 50nm.

7. A method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation, characterized in that, The preparation method includes: Obtain the substrate layer and clean the substrate layer; An AlN nucleation layer is grown on the substrate. A GaN channel layer is grown on the AlN nucleation layer; An AlN barrier layer is grown on the GaN channel layer; A first passivation layer is formed on the AlN barrier layer; A second passivation layer is grown on the first passivation layer; wherein the second passivation layer is a high thermal conductivity material BeO; The second passivation layers at both ends of the device are etched up to the upper surface of the AlN barrier layer, so as to deposit ohmic metal on the AlN barrier layer at one end of the device to form the source, and deposit ohmic metal on the AlN barrier layer at the other end to form the drain. The second passivation layer near the source is etched until the upper surface of the first passivation layer is formed to create a gate groove. Gate metal is deposited in the gate groove and on part of the upper surface of the second passivation layer to form a T-shaped gate.

8. The method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation according to claim 7, characterized in that, A first passivation layer is grown on the AlN barrier layer, comprising: A first passivation layer with a thickness of 25 nm to 35 nm was grown on the AlN barrier layer using the PECVD process.

9. The method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation according to claim 7, characterized in that, Growing a second passivation layer on the first passivation layer includes: Using the ALD process, a second passivation layer with a thickness of 20 nm to 50 nm is grown on the first passivation layer.

10. The method for fabricating an AlN-based radio frequency power transistor based on high thermal conductivity BeO passivation according to claim 7, characterized in that, Before growing the AlN barrier layer on the GaN channel layer, the method further includes: An AlGaN buffer layer or a GaN buffer layer is grown on the GaN channel layer to grow an AlN barrier layer on the AlGaN buffer layer or the GaN buffer layer.

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