A high linearity radio frequency GaN-based HEMT device and a preparation method thereof

Abstract

The application belongs to the technical field of semiconductor devices, and specifically discloses a high-linearity radio frequency GaN-based HEMT device and a preparation method thereof, which comprises a substrate, a nucleation layer, a buffer layer, a channel layer, a barrier layer, a source electrode, a drain electrode, a gate electrode, a first passivation layer and a second passivation layer, and the channel layer is internally provided with an N+ type buried layer on the side of the source electrode; the N+ type buried layer is located in the upper part of the channel layer and keeps a certain distance from the interface between the barrier layer and the channel layer; and the source electrode and two-dimensional electron gas form a Schottky diode structure through the N+ buried layer. The application sets a heavily doped GaN region below the source electrode to the gate electrode in the channel layer, and the source electrode and the heavily doped GaN region form an ohmic contact, so that the two-dimensional electron gas below the gate electrode and the source electrode form a Schottky diode structure through the N+ type buried layer, the device keeps a relatively stable transconductance in a larger current range, the linearity of the GaN-based HEMT is improved, and signal distortion is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a high-linearity radio frequency GaN-based HEMT device and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN) is a wide-bandgap semiconductor material that excels in high-frequency, high-power, and high-temperature applications due to its unique electrical and thermal properties. It is considered a highly promising candidate material for RF / microwave power amplifiers. GaN electronic devices are primarily GaN heterostructure high electron mobility transistors (HEMTs). The two-dimensional electron gas (2DEG) formed at the interface of nitride heterostructures such as AlGaN / GaN exhibits high mobility, extremely high 2DEG density, and electron saturation velocity. This enables GaN-based HEMT devices to achieve high output current and high output power, making them ideal for high-frequency and high-power applications and a key component of power amplifiers (PAs).

[0003] In 4G LTE and 5G communication systems, the power amplifiers in RF modules must exhibit excellent linearity to minimize distortion between input and output signals, thereby improving data transmission rates and spectral efficiency. Therefore, the core GaN HEMT devices must exhibit high linearity, meaning their transconductance should remain stable as the output current changes. However, currently reported GaN HEMT devices often exhibit severe nonlinear characteristics, which are more pronounced at high frequencies. This can cause signal distortion during transmission, reducing transmission efficiency and causing signal distortion.

[0004] The main physical mechanisms that cause the low linearity of GaN HEMT devices include: (1) significant self-heating effects inside GaN HEMT devices when operating at high power; (2) velocity saturation effects at high carrier density in the GaN HEMT two-dimensional electron gas (2DEG) channel; (3) the influence of interface scattering and barrier alloy scattering on carriers under high gate voltage; and (4) limited gate-source channel current supply at high output current. To address these physical mechanisms, existing technologies have proposed improving the linearity of GaN HEMT devices by using structures such as composite channels, multi-channels, doped channels, and under-gate nanowire / band channels. However, these methods have disadvantages such as complex epitaxial structures and cumbersome processes. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a high-linearity RF GaN-based HEMT device and a preparation method thereof, which can achieve a shorter distance between the source electrode and the gate electrode, thereby reducing the source access resistance and improving the device performance.

[0006] In order to achieve the above object, the present application is implemented according to the following technical scheme:

[0007] One of the technical schemes of the present application is a high linearity radio frequency GaN-based HEMT device, which comprises, from bottom to top, a substrate, a nucleation layer, a buffer layer, a channel layer and a barrier layer, a two-dimensional electron gas is formed in the interface between the channel layer and the barrier layer, the upper end surface of the barrier layer is provided with a drain electrode and a gate electrode, and the upper end surface of the barrier layer between the drain electrode and the gate electrode is provided with a first passivation layer.

[0008] The inner part of one end of the channel layer away from the drain electrode is provided with an N+ type buried layer, the N+ type buried layer is located in the upper middle part of the channel layer, the upper end surface of the barrier layer at one end of the gate electrode is provided with a first groove, the bottom of the first groove is located on the upper end surface of the channel layer, the upper end surface of one end of the channel layer is provided with a second groove, at this time, in the channel layer below the first groove, there is no two-dimensional electron gas, and the source electrode and the two-dimensional electron gas below the gate electrode can be isolated, the bottom of the second groove is located on the upper end surface of one end of the N+ type buried layer, the second groove is provided with a source electrode, the source electrode forms an ohmic contact with the N+ type buried layer, the source electrode and the two-dimensional electron gas form a Schottky diode structure through the N+ buried layer, so as to improve the linearity of the GaN-based HEMT device, the upper end surface of the channel layer between the source electrode and the gate electrode is provided with a second passivation layer, and the channel layer and the barrier layer between the source electrode and the gate electrode form a high resistance area, so as to isolate the two-dimensional electron gas below the source electrode and the gate electrode.

[0009] Further, the drain electrode forms an ohmic contact with the two-dimensional electron gas of the channel layer, or the drain electrode forms a Schottky contact with the two-dimensional electron gas of the channel layer, the gate electrode forms a Schottky contact with the barrier layer, or a layer of insulating medium arranged on the lower end surface of the gate electrode forms a metal-insulator-semiconductor (MIS) structure with the barrier layer.

[0010] Further, the N+ type buried layer is made of GaN, the doping type is N type, the doping concentration is 1x10 18- 1x10 21 cm -3 , and the thickness is 10-200nm.

[0011] Further, the material of the buffer layer is undoped GaN or AlGaN, and the thickness is 200nm to 5μm.

[0012] Further, the material of the channel layer is one or a combination of more than one of GaN, InGaN and AlGaN, and the thickness is 50nm-500nm.

[0013] Further, the material of the barrier layer is one or a combination of more than one of AlGaN, InGaN and AlN, and the thickness is 5nm-50nm.

[0014] Furthermore, the material of the first passivation layer and the second passivation layer is any one of Si3N4, SiO2, and Al2O3, and the thickness of the first passivation layer and the second passivation layer are both 10nm-200nm.

[0015] Furthermore, the material of the drain electrode is one or more combinations of Ti, Al, Ni, Mo, Pt, Nb, and Au; the material of the gate electrode and the source electrode is one of Ni / Au, Ti / Au, TiN / Au, Ta / Au, and Ni / Cr stacked metals.

[0016] Furthermore, the nucleation layer consists of a low-temperature AlN nucleation layer and a pulsed high-temperature AlN nucleation layer from bottom to top, a transition layer is provided between the pulsed high-temperature AlN nucleation layer and the buffer layer, an isolation layer is provided between the channel layer and the barrier layer, and a cap layer is provided on the upper end surface of the barrier layer.

[0017] A second technical solution of the present invention is a method for preparing a high-linearity radio frequency GaN-based HEMT device, comprising the following steps:

[0018] Step 1: Clean the surface of the substrate;

[0019] Step 2: growing a nucleation layer, a buffer layer and a channel layer of a certain thickness on the substrate in sequence;

[0020] Step 3: Set a heavily doped N+ buried layer and continue growing the channel layer, ensuring that a certain distance is maintained between the N+ buried layer and the barrier layer;

[0021] Step 4: growing a barrier layer;

[0022] Step 5: Clean the epitaxial wafer and isolate the device;

[0023] Step 6: Grow a drain electrode on the barrier layer and perform annealing to form an ohmic contact;

[0024] Step 7: Etching is performed on a portion of the barrier layer and the channel layer; a source electrode is deposited and annealed to form an ohmic contact between the source electrode and the N+ buried layer;

[0025] Step 8: Depositing the gate electrode;

[0026] Step 9: Etch between the gate electrode and the source electrode to form a groove, completely etch away the barrier layer, and etch the groove to the upper surface of the channel layer;

[0027] Step 10: Deposit a first passivation layer and a second passivation layer.

[0028] Compared with the existing technology, the present invention provides a heavily doped GaN region between the source electrode and the bottom of the gate electrode in the channel layer. The source electrode forms an ohmic contact with the heavily doped GaN region, so that the two-dimensional electron gas below the gate electrode and the source electrode form a Schottky diode structure through the N+ type buried layer. This allows the device to maintain a relatively stable transconductance over a larger current range, improves the linearity of the GaN-based HEMT, and reduces signal distortion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a high-linearity radio frequency GaN-based HEMT device according to an embodiment of the present invention.

[0030] Figure 2 It is a schematic flow chart of a method for preparing a high-linearity radio frequency GaN-based HEMT device according to an embodiment of the present invention.

[0031] Figure 3 It is a schematic diagram of the process of a method for preparing a high-linearity radio frequency GaN-based HEMT device according to an embodiment of the present invention.

[0032] Figure 4 It is a structural schematic diagram of a high-linearity radio frequency GaN-based HEMT device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] like Figure 1As shown, the embodiment exemplarily shows a high linearity radio frequency GaN-based HEMT device, which comprises, from bottom to top, a substrate 1, a nucleation layer 2, a buffer layer 3, a channel layer 4 and a barrier layer 5, a two-dimensional electron gas is formed in the interface of the channel layer 4 and the barrier layer 5, an upper end surface of the barrier layer 5 is provided with a drain electrode 6 and a gate electrode 7, and an upper end surface of the barrier layer 5 between the drain electrode 6 and the gate electrode 7 is provided with a first passivation layer 10; an inner portion of one end of the channel layer 4 away from the drain electrode 6 is provided with an N+ buried layer 9, the N+ buried layer 9 is located in an upper middle portion of the channel layer 4; an upper end surface of the barrier layer 5 at one end of the gate electrode 7 is provided with a first groove, a bottom of the first groove is located on an upper end surface of the channel layer 4, at this time, no two-dimensional electron gas is formed in the channel layer below the first groove, and isolation of a source electrode from the two-dimensional electron gas below the gate electrode can be realized; an upper end surface of one end of the channel layer 4 is provided with a second groove, a bottom of the second groove is located on an upper end surface of one end of the N+ buried layer 9, and a source electrode 8 is arranged in the second groove, the source electrode 8 forms an ohmic contact with the N+ buried layer 9, and the source electrode 8 and the two-dimensional electron gas form a Schottky diode structure through the N+ buried layer 9, so that the device maintains a relatively stable transconductance in a larger current range, the linearity of the GaN-based HEMT is improved, and signal distortion is reduced; an upper end surface of the channel layer 4 between the source electrode 8 and the gate electrode 7 is provided with a second passivation layer 11, at this time, a high resistance region is formed in the channel layer 4 and the barrier layer 5 between the source electrode 8 and the gate electrode 7, and isolation of the source electrode 8 from the two-dimensional electron gas below the gate electrode 7 is realized.

[0036] In actual use, the drain electrode 6 directly forms an ohmic contact with the two-dimensional electron gas of the channel layer 4, or forms a Schottky contact with the two-dimensional electron gas of the channel layer 4; at the same time, the gate electrode 7 forms a Schottky contact with the barrier layer 5, or forms a metal-insulator-semiconductor (MIS) structure with the barrier layer 5 through an insulating medium layer below the gate electrode 7.

[0037] In the embodiment, the N+ buried layer 9 is made of GaN, the doping type is N type, the doping concentration is 1×1018cm-3, and the thickness is 10-200nm. 18 -1×10 21 cm -3 .

[0038] The substrate 1 is made of one of silicon carbide, sapphire and diamond, and preferably is silicon carbide with a thickness of 500μm.

[0039] The nucleation layer 2 is made of AlN with a thickness of 100nm, and is used to release the lattice mismatch stress and thermal stress between the buffer layer 3 and the substrate.

[0040] The material of the buffer layer 3 is undoped GaN or AlGaN, and the thickness is 200nm to 5μm; preferably, the thickness of the GaN is 1.2μm.

[0041] The material of the channel layer 4 is GaN, InGaN or AlGaN, and the thickness is 50 nm to 500 nm; preferably, the thickness of the channel layer 4 is 300 nm.

[0042] The barrier layer 5 is made of AlGaN, InGaN or AlN, with a thickness of 5 nm to 50 nm; preferably, AlGaN with a thickness of 20 nm and an Al composition of 0.3.

[0043] The material of the drain electrode 6 is any one or more combinations of Ti / Al / Ni, Mo, Pt, and Nb / Au; preferably, an alloy consisting of four layers of metal films of Ti / Al / Ni / Au, with corresponding film thicknesses of 22nm / 150nm / 55nm / 45nm respectively.

[0044] The material of the gate electrode 7 and the source electrode 8 is any one of Ni / Au, Ti / Au, TiN / Au, Ta / Au, and Ni / Cr laminated metals; the gate electrode 7 is preferably Ni / Au (50nm / 150nm) laminated metal; the source electrode 8 is preferably Ni / Cr (50nm / 150nm) laminated metal.

[0045] The material of the first passivation layer 10 and the second passivation layer 11 is any one of Si3N4, SiO2, and Al2O3, and the thickness of the first passivation layer 10 and the second passivation layer 11 are both 10nm-200nm; the first passivation layer 10 is preferably a Si3N4 film with a thickness of 150nm; the second passivation layer 11 is preferably a Si3N4 film with a thickness of 170nm.

[0046] Reference Figure 2 、 Figure 3 The specific process of preparing the high linearity RF GaN-based HEMT device of this embodiment is as follows:

[0047] Step 1: Cleaning the surface of a selected SiC substrate 1 having a thickness of 500 μm;

[0048] At 1000°C, hydrogen is introduced into the reaction chamber to remove contaminants from the surface of substrate 1 and form a microscopic step structure on the surface of substrate 1, thereby preparing for the subsequent epitaxial growth process of various epitaxial layers.

[0049] Step 2: using metal organic chemical vapor deposition to sequentially grow a nucleation layer 2, a buffer layer 3, and a channel layer 4 of a certain thickness on the substrate 1;

[0050] The nucleation layer 2 is made of AlN with a thickness of 100 nm, the buffer layer 3 is made of GaN with a thickness of 1.2 μm, and the channel layer 4 is made of GaN with a thickness of 300 nm. However, only 200 nm of the channel layer 4 is deposited first.

[0051] The barrier layer 5 is made of AlGaN with a thickness of 20 nm and an Al composition of 0.3;

[0052] Step 3: Using ion implantation, a heavily doped N+ buried layer 9 is placed below the source electrode and gate electrode in the channel layer 4 that has been deposited to a certain thickness. 100 nm of the N+ buried layer is deposited on top of the N+ buried layer 9 to complete the deposition of the channel layer 4, ensuring that the N+ buried layer 9 is at a certain distance from the barrier layer 5.

[0053] Step 4: using metal organic chemical vapor deposition to grow a barrier layer 5 on the channel layer 4;

[0054] The barrier layer 5 is made of AlGaN with a thickness of 20 nm and an Al composition of 0.3;

[0055] Step 5: Clean the epitaxial wafer and isolate the device;

[0056] The work of cleaning epitaxial wafers mainly includes cleaning organic matter, cleaning inorganic matter and removing the surface passivation layer. Use acetone solution to ultrasonically clean the sample for 2 minutes, then place the sample in ethanol solution and ultrasonicate for 3 minutes to remove the residual acetone liquid on the sample surface. Soak the sample in diluted HF solution for 1 minute to remove surface oxides and inorganic contaminants, and finally rinse with running deionized water and blow dry with a nitrogen gun. Removal of residual photoresist during the photolithography process and cleaning of the sample surface before metal evaporation are also required;

[0057] The mesa isolation adopts the mesa isolation technology which is less complex, lower cost and easier to implement. The etching gas is Cl2 and the etching depth is 400nm.

[0058] Step 6: Make Ohmic Contact for Drain Electrode 6

[0059] Four metal layers were grown in this area by electron beam evaporation, using Ti / Al / Ni / Au with corresponding film thicknesses of 22nm / 150nm / 55nm / 45nm, and then rapidly annealed in N2 at 880℃ for 30s to alloy and form ohmic contacts;

[0060] Step 7: Etch away the barrier layer 5 and part of the channel layer 4 using a low-damage Cl2 / BCl3 etching process. The etching equipment is a reactive ion etching (RIE) with an etching rate of 2.5 nm / min and an etching depth of 100 nm.

[0061] Step 8: Making gate electrode 7 and source electrode 8;

[0062] The gate electrode 7 is typically made of a metal with a high work function. In this embodiment, a Ni / Au stack is used. A Ni / Au (50 / 150 nm) double layer is deposited using electron beam evaporation. After evaporation, the sample is rapidly annealed in an N2 atmosphere at 450°C for 5 minutes to form a gate Schottky contact.

[0063] Fabricate the source electrode 8. Select a metal with a high work function as the source metal. In this embodiment, a Ni / Cr stacked metal is used. Rapidly anneal the metal at 880°C in N2 for 30 seconds to form an ohmic contact between the source electrode 8 and the n+ buried layer 9.

[0064] Step 9: Reactive ion etching (RIE) is used to etch the barrier layer region between the source electrode and the gate electrode to form a groove, completely etching away the barrier layer portion, and etching to the upper surface of the channel layer;

[0065] Step 10: preparing a first passivation layer 10 and a second passivation layer 11;

[0066] A Si3N4 film with a thickness of 150 nm is deposited on the surface of the barrier layer by plasma enhanced chemical vapor deposition (PECVD);

[0067] A Si3N4 film with a thickness of 170 nm is deposited in the groove between the source electrode and the gate electrode by plasma enhanced chemical vapor deposition (PECVD).

[0068] According to the AC small signal equivalent circuit of the actual HEMT device, including the intrinsic field effect tube part and the series resistor R S and R D Parasitic effects caused by etc.

[0069] Transconductance g m It reflects the gate's ability to control the channel current, ignoring the series resistance R S and R D The transconductance obtained in the case of intrinsic transconductance g m *, the saturation transconductance of the HEMT device is:

[0070]

[0071] In actual devices, the series resistance R S and R D In this case, I DS The source-drain series resistor R S and R D The voltage drop across R S and R D The channel resistance comes from the gate-free channel region between the gate source and the gate drain, as well as the source-drain ohmic contact resistance R C .

[0072] Source resistance R S The effective gate voltage between the gate and source decreases, which affects the saturation region transconductance g. m . Leakage resistance R D The source-drain voltage V when the current begins to saturate Dsat Increase, but V DS >V Dsat V DS has no effect on the output current, so R D For g m No impact.

[0073] The formula satisfied by the measured transconductance is:

[0074]

[0075] A heavily doped N+ type buried layer is provided at one end of the channel layer of a conventional GaN-based HEMT device, and the source electrode forms an ohmic contact with the channel layer through the N+ type buried layer.

[0076] This structure can reduce the source contact resistance R c , so that the source series resistance R S At a certain V gs The range is basically unchanged, making the measured transconductance g m In this V gs The device exhibits wide transconductance and high linearity, which solves the problem of conventional GaN-based HEMT devices. m Relatively narrow problem, resulting in a flat g m , thereby stabilizing the gate's ability to control the channel current, making GaN-based HEMT devices have higher linearity, which is of great value to high-linearity RF devices.

[0077] Example 2

[0078] like Figure 4 As shown, this embodiment exemplarily shows the structure of another high-linearity RF GaN-based HEMT device. The difference from the embodiment is that: this embodiment divides the nucleation layer 2 into two layers, a low-temperature AlN nucleation layer 12 and a pulsed high-temperature AlN nucleation layer 22, introduces a transition layer 13 between the nucleation layer 22 and the buffer layer 3, introduces an isolation layer 14 between the channel layer 4 and the barrier layer 5, and introduces a cap layer 15 on the barrier layer 5.

[0079] In the embodiment, the sapphire substrate 1 has a thickness of 300 μm; the gallium nitride buffer layer 3 has a thickness of 1.5 μm; the gallium nitride channel layer 4 has a thickness of 200 nm; the barrier layer 5 is made of indium aluminum nitride with an indium component of 0.17 and a thickness of 15 nm; and the first passivation layer 10 and the second passivation layer 11 are made of Al2O3 and have a thickness of 150 nm.

[0080] The low-temperature AlN nucleation layer 12 and the pulse high-temperature AlN nucleation layer 22 are grown in sequence on the substrate 1 to the channel layer 4 by the MOCVD method in a two-step growth method, and each has a thickness of 50-150 nm. Different from the embodiment 1, the sapphire substrate 1 is provided with the low-temperature AlN nucleation layer 12, so that a GaN epitaxial layer with higher crystalline quality can be obtained, the growth temperature is 500-650 ℃, the pulse high-temperature AlN nucleation layer 22 can reduce the interface free energy between the gallium nitride and the substrate, so that a high-quality GaN epitaxial layer can be realized, and on the other hand, the leakage problem can be effectively overcome, and the growth temperature is 1000-1100 ℃.

[0081] The AlGaN transition layer 13 is grown on the pulse high-temperature nucleation layer 22 by the MOCVD method, and has a thickness of 200-1000 nm. Different from the embodiment 1, the introduction of the transition layer 13 can reduce the interface tension caused by the lattice mismatch between the substrate 1 and the gallium nitride layer.

[0082] The insertion layer 14 is grown above the channel layer 4 by the MOCVD method, and has a thickness in a range of 0.5 nm-2 nm. Different from the embodiment 1, the insertion layer 14 can improve the channel electron density and electron mobility, and improve the effect of the heterojunction interface.

[0083] The cap layer 15 is grown above the barrier layer 5 by the MOCVD method, and has a thickness in a range of 50 nm-200 nm. Different from the embodiment 1, if the surface of the heterojunction is directly the surface of the AlGaN barrier layer, the oxidation property of Al may cause the problem that the characteristics of the heterojunction deteriorate over time, and the introduction of the cap layer 15 can improve the properties of the heterojunction surface and the whole material.

[0084] It should be noted that when one or two of the above low-temperature nucleation layer 12, the pulse high-temperature nucleation layer 22, the transition layer 13, the isolation layer 14 and the cap layer 15 are cancelled, the effect of the remaining layers is not affected.

[0085] In summary, the present application mainly forms a Schottky diode structure by the two-dimensional electron gas below the gate electrode and the source electrode through the N+ type buried layer, so that the device can maintain a relatively stable transconductance in a larger current range, the linearity of the GaN-based HEMT is improved, and signal distortion is reduced.

[0086] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A high-linearity radio frequency GaN-based HEMT device, comprising, from bottom to top, a substrate (1), a nucleation layer (2), a buffer layer (3), a channel layer (4), and a barrier layer (5), wherein a two-dimensional electron gas is formed at the interface between the channel layer (4) and the barrier layer (5), a drain electrode (6) and a gate electrode (7) are provided on the upper end surface of the barrier layer (5), and a first passivation layer (10) is provided on the upper end surface of the barrier layer (5) between the drain electrode (6) and the gate electrode (7); characterized in that: An N+ type buried layer (9) is provided inside one end of the channel layer (4) away from the drain electrode (6), and the N+ type buried layer (9) is located in the middle and upper part of the channel layer (4); a first groove is provided on the upper end surface of the barrier layer (5) at one end of the gate electrode (7), and the bottom of the first groove is located at the upper end surface of the channel layer (4); a second groove is provided on the upper end surface of one end of the channel layer (4), and the bottom of the second groove is located at the upper end surface of one end of the N+ type buried layer (9); a source electrode (8) is provided in the second groove, and the source electrode (8) forms an ohmic contact with the N+ type buried layer (9), and the source electrode (8) and the two-dimensional electron gas form a Schottky diode structure through the N+ buried layer (9); and a second passivation layer (11) is provided on the upper end surface of the channel layer (4) between the source electrode (8) and the gate electrode (7).

2. The high-linearity RF GaN-based HEMT device according to claim 1, characterized in that: The drain electrode (6) forms an ohmic contact with the two-dimensional electron gas of the channel layer (4); or the drain electrode (6) forms a Schottky contact with the two-dimensional electron gas of the channel layer (4); the gate electrode (7) forms a Schottky contact with the barrier layer (5); or a metal-insulating layer-semiconductor MIS structure is formed with the barrier layer (5) through a layer of insulating medium provided on the lower end surface of the gate electrode (7).

3. The high-linearity RF GaN-based HEMT device according to claim 1, wherein: The N+ type buried layer (9) is made of GaN, with an N-type doping type and a doping concentration of 1×10 18 -1×10 21 cm -3 , with a thickness of 10-200nm.

4. The high-linearity RF GaN-based HEMT device according to claim 1, wherein: The material of the buffer layer (3) is undoped GaN or AlGaN, and the thickness is 200 nm to 5 μm.

5. The high-linearity RF GaN-based HEMT device according to claim 1, characterized in that: The material of the channel layer (4) is one or more combinations of GaN, InGaN and AlGaN, and the thickness is 50nm-500nm.

6. The high-linearity RF GaN-based HEMT device according to claim 1, characterized in that: The barrier layer (5) is made of a material selected from the group consisting of AlGaN, InGaN and AlN, and has a thickness of 5 nm to 50 nm.

7. The high-linearity RF GaN-based HEMT device according to claim 1, characterized in that: The material of the first passivation layer (10) and the second passivation layer (11) is any one of Si3N4, SiO2, and Al2O3, and the thickness of the first passivation layer (10) and the second passivation layer (11) are both 10nm-200nm.

8. The high-linearity RF GaN-based HEMT device according to claim 1, characterized in that: The material of the drain electrode (6) is one or more combinations of Ti, Al, Ni, Mo, Pt, Nb, and Au; the material of the gate electrode (7) and the source electrode (8) is one of Ni / Au, Ti / Au, TiN / Au, Ta / Au, and Ni / Cr laminated metals.

9. The high-linearity RF GaN-based HEMT device according to any one of claims 1 to 8, characterized in that: The nucleation layer (2) consists of a low-temperature AlN nucleation layer (12) and a pulse high-temperature AlN nucleation layer (22) from bottom to top; a transition layer (13) is provided between the pulse high-temperature AlN nucleation layer (22) and the buffer layer 3; an isolation layer (14) is provided between the channel layer (4) and the barrier layer (5); and a cap layer (15) is provided on the upper end surface of the barrier layer (5).

10. A method for preparing a high-linearity RF GaN-based HEMT device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Cleaning the surface of the substrate (1); Step 2: sequentially growing a nucleation layer (2), a buffer layer (3) and a channel layer (4) of a certain thickness on the substrate; Step 3: Arrange a heavily doped N+ type buried layer (9), continue to grow the channel layer (4), and ensure that a certain distance is maintained between the N+ type buried layer (9) and the barrier layer (5); Step 4: growing a barrier layer (5); Step 5: Clean the epitaxial wafer and isolate the device; Step 6: growing a drain electrode (6) on the barrier layer (5) and performing annealing to form an ohmic contact; Step 7: Etching is performed on a portion of the barrier layer (5) and the channel layer (4); a source electrode (8) is deposited and annealed to form an ohmic contact between the source electrode and the N+ type buried layer (9); Step 8: depositing the gate electrode (7); Step 9: Etching is performed between the gate electrode (7) and the source electrode (8) to form a groove, completely etching away the barrier layer (5), and the groove is etched to the upper surface of the channel layer (4); Step 10: Depositing a first passivation layer (10) and a second passivation layer (11).

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