High-linearity radio frequency GaN-based HEMT device and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor devices, and particularly discloses a high-linearity radio frequency GaN-based HEMT device and a preparation method thereof.The high-linearity radio frequency GaN-based HEMT device comprises a substrate, a nucleating 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; the N + type buried layer is located on the upper middle portion of the channel layer and keeps a certain distance from the interface of the barrier layer and the channel layer, and the source electrode and the two-dimensional electron gas form a Schottky diode structure through the N + type buried layer. A heavily-doped GaN region is arranged below a source electrode and a gate electrode in a channel layer, and the source electrode and the heavily-doped GaN region form ohmic contact, so that two-dimensional electron gas below the gate electrode and the source electrode form a Schottky diode structure through an N + type buried layer; therefore, the device keeps 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 performs well in high-frequency, high-power and high-temperature applications with its unique electrical and thermal properties. It is considered to be one of the most promising candidate materials for RF / microwave power amplifiers. GaN electronic devices are mainly GaN heterostructure high electron mobility transistors (HEMTs). The two-dimensional electron gas (2DEG) formed at the interface of nitride heterostructures such as AIGaN / GaN has high mobility, extremely high two-dimensional electron gas density and electron saturation velocity, which enables GaN-based HEMT devices to have high output current and high output power capabilities, which are very suitable for high-frequency and high-power applications and have become a key component of power amplifiers (PAs).

[0003] In 4G LTE and 5G communication systems, the power amplifier of the RF module needs to have good linear characteristics to reduce the distortion between the input and output signals, thereby improving the data transmission rate and spectrum efficiency. Therefore, the core GaN HEMT device needs to have high linearity, that is, its transconductance should remain stable as the output current changes. However, the existing reported GaN HEMT devices usually exhibit serious nonlinear characteristics, which are more obvious under high-frequency conditions, which can cause signal distortion during transmission, thereby reducing transmission efficiency and causing signal distortion and other problems.

[0004] The main physical mechanisms that cause the low linearity of GaN HEMT devices include: (1) significant self-heating effect inside GaN HEMT devices when working at high power; (2) velocity saturation effect under 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; (4) limited gate-source channel current supply at high output current. To address these physical mechanisms, existing technologies propose to improve the linearity of GaN HEMT devices by using structures such as composite channel, multi-channel, doped channel, and nanowire / band channel under the gate, but these methods have disadvantages such as complex epitaxial structure and cumbersome process. 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] To achieve the above object, the present invention is implemented according to the following technical solutions:

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

[0008] An N+ buried layer is arranged inside one end of the channel layer away from the drain electrode, and the N+ buried layer is located in the middle and upper part of the channel layer; a first groove is arranged on the upper end surface of the barrier layer at one end of the gate electrode, and the bottom of the first groove is located on the upper end surface of the channel layer, and a second groove is arranged on the upper end surface of one end of the channel layer. At this time, there is no two-dimensional electron gas in the channel layer below the first groove, and the isolation of the source electrode and the two-dimensional electron gas below the gate electrode can be achieved; the bottom of the second groove is located on the upper end surface of one end of the N+ buried layer, and a source electrode is arranged in the second groove, and the source electrode forms an ohmic contact with the N+ buried layer, and the source electrode and the two-dimensional electron gas form a Schottky diode structure through the N+ buried layer to improve the linearity of the GaN-based HEMT device; a second passivation layer is arranged on the upper end surface of the channel layer between the source electrode and the gate electrode; the channel layer and the barrier layer between the source electrode and the gate electrode form a high-resistance region to achieve the isolation of the source electrode and the two-dimensional electron gas below the gate electrode.

[0009] Furthermore, 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 and the barrier layer form a metal-insulating layer-semiconductor MIS structure.

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

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

[0012] Furthermore, the material of the channel layer is one or more combinations of GaN, InGaN and AlGaN, and the thickness is 50nm-500nm.

[0013] Furthermore, the material of the barrier layer is one or more combinations 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 Si 3 N 4 、SiO 2 、Al 2 O 3 In any one of the embodiments, 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 laminated metals.

[0016] Furthermore, the nucleation layer consists of a low-temperature AlN nucleation layer and a pulse high-temperature AlN nucleation layer from bottom to top, a transition layer is provided between the pulse 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] The 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: Cleaning the surface of the substrate;

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

[0020] Step 3: Set a heavily doped N+ buried layer and continue to grow the channel layer to ensure 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: growing a drain electrode on the barrier layer and performing 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: Etching is performed between the gate electrode and the source electrode to etch a groove, completely etching away the barrier layer, and the groove is etched 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 prior art, the present invention provides a heavily doped GaN region from the source electrode to below the gate electrode in the channel layer, and 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, so that the device maintains a relatively stable transconductance within 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 schematic structural 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 schematic structural 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 solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0034] Example 1

[0035] like Figure 1As shown, this embodiment exemplarily shows a high linearity RF GaN-based HEMT device, which includes a substrate 1, a nucleation layer 2, a buffer layer 3, a channel layer 4 and a barrier layer 5 from bottom to top, 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; 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 on the upper end surface of the channel layer 4. At this time, there is no two-dimensional electron gas in the channel layer below the first groove, which can achieve Isolation of the two-dimensional electron gas under the source electrode and the gate electrode; a second groove is provided on the upper end surface of one end of the channel layer 4, the bottom of the second groove is located at the upper end surface of one end of the N+ buried layer 9, a source electrode 8 is provided in the second groove, the source electrode 8 forms an ohmic contact with the N+ buried layer 9, 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 within a larger current range, improves the linearity of the GaN-based HEMT, and reduces signal distortion; 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, at this time, the channel layer 4 and the barrier layer 5 between the source electrode 8 and the gate electrode 7 form a high-resistance region, so as to achieve isolation of the two-dimensional electron gas under the source electrode 8 and the gate electrode 7.

[0036] During 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 a layer of insulating medium under the gate electrode 7.

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

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

[0039] The nucleation layer 2 is made of AlN with a thickness of 100 nm, and the nucleation layer 2 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, with a thickness of 200 nm to 5 μm; preferably, GaN with a thickness of 1.2 μm.

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

[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, and the corresponding film thicknesses are 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 Si 3 N 4 、SiO 2 、Al 2 O 3 In any one of the above, the first passivation layer 10 and the second passivation layer 11 have a thickness of 10nm-200nm; the first passivation layer 10 is preferably Si with a thickness of 150nm. 3 N 4 The second passivation layer 11 preferably has a thickness of 170nm Si 3 N 4 film.

[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 the selected SiC substrate 1 with a thickness of 500 μm;

[0048] At 1000°C, hydrogen is introduced into the reaction chamber to remove pollutants on the surface of the substrate 1 and form a microscopic step structure on the surface of the 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 core 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, but 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 provided below the source electrode to the gate electrode in the channel layer 4 that has been deposited to a certain thickness, and 100 nm of the N+ buried layer 9 is further deposited 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 of organic matter, cleaning of inorganic matter and removal of surface passivation layer. Use acetone solution to ultrasonically clean the sample for 2 minutes, then put the sample into ethanol solution for ultrasonication 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 pollutants, 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 with low complexity, low cost and easier implementation. The etching gas is Cl 2 , the etching depth is 400nm;

[0058] Step 6: Making 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 heated to 880℃ in N 2 Rapid annealing for 30 seconds to form ohmic contact through alloying;

[0060] Step 7: Etch away the barrier layer 5 and part of the channel layer 4, and use low-damage Cl 2 / BCl 3Etching process: the etching equipment is reactive ion etching (RIE), the etching rate is 2.5nm / min, and the etching depth is 100nm;

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

[0062] The gate electrode 7 is usually made of a metal with a higher work function. In this embodiment, Ni / Au laminated metal is used. Electron beam evaporation equipment is used to deposit Ni / Au (50 / 150nm) double-layer metal. After the metal is evaporated, the sample is placed in N at 450°C. 2 Rapid annealing in atmosphere for 5 min to form gate Schottky contact;

[0063] The source electrode 8 is made by selecting a metal with a higher work function as the source metal. In this embodiment, Ni / Cr laminated metal is used. 2 Rapid annealing 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 layer of Si is deposited on the surface of the barrier layer by plasma enhanced chemical vapor deposition (PECVD). 3 N 4 The film has a thickness of 150nm;

[0067] A layer of Si is deposited in the groove between the source electrode and the gate electrode by plasma enhanced chemical vapor deposition (PECVD). 3 N 4 The film has a thickness of 170nm.

[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. When the series resistance R is ignored, S and R D The transconductance obtained in the case of 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 from the gate-free channel region between the gate source and the gate drain and the source-drain ohmic contact resistance R C .

[0072] Source resistance R S The effective gate voltage between the gate and the source decreases, which affects the saturation region transconductance g. m . Leakage resistance R D The source-drain voltage V 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 disposed at one end of the channel layer of a conventional GaN-based HEMT device, and a 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, making it have 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 4As shown, this embodiment exemplarily shows the structure of another high linearity RF GaN-based HEMT device, which is different from the embodiment in that: this embodiment divides the nucleation layer 2 into two layers, a low-temperature AlN nucleation layer 12 and a pulse 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 this embodiment, a sapphire substrate 1 is selected with a thickness of 300 μm; a gallium nitride buffer layer 3 is 1.5 μm thick, a gallium nitride channel layer 4 is 200 nm thick, a barrier layer 5 is made of indium aluminum nitride, an indium component of 0.17, and a thickness of 15 nm, and a first passivation layer 10 and a second passivation layer 11 are made of Al 2 O 3 , thickness is 150nm.

[0080] The MOCVD method is adopted, and a two-step growth method is used to sequentially grow a low-temperature AlN nucleation layer 12 and a pulse high-temperature AlN nucleation layer 22 on the substrate 1 toward the channel layer 4, and the thickness of each is 50-150 nm. The difference from Example 1 is that the low-temperature AlN nucleation layer 12 is adopted on the sapphire substrate 1 to obtain a GaN epitaxial layer with high crystal quality, and the growth temperature is 500-650° C. The pulse high-temperature AlN nucleation layer 22 can reduce the interface free energy between gallium nitride and the substrate on the one hand, so as to realize a high-quality GaN epitaxial layer, and on the other hand, it can effectively overcome the leakage problem, and the growth temperature is 1000-1100° C.;

[0081] An AlGaN transition layer 13 with a thickness of 200 to 1000 nm is grown on the pulse high temperature nucleation layer 22 by MOCVD. The difference from Example 1 is that 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] An insertion layer 14 is grown on the channel layer 4 by MOCVD, and the thickness thereof may be in the range of 0.5 nm to 2 nm. The difference from Example 1 is that the insertion layer 14 can increase the channel electron density and electron mobility, and improve the effect of the heterogeneous interface.

[0083] A cap layer 15 is grown on the barrier layer 5 by MOCVD, and the thickness may be in the range of 50nm-200nm. The difference from Example 1 is that if the surface of the heterojunction is directly the surface of the AlGaN barrier layer, the easy oxidation of Al may cause the characteristics of the heterojunction to degrade over time. The introduction of the cap layer 15 can improve the properties of the heterojunction surface and the overall material.

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

[0085] In summary, the present invention mainly forms a Schottky diode structure through an N+ type buried layer between the two-dimensional electron gas under the gate electrode and the source electrode, so that the device maintains a relatively stable transconductance within a larger current range, improves the linearity of the GaN-based HEMT, and reduces signal distortion.

[0086] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All 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), 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 arranged 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 arranged 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 arranged 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 arranged 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 arranged 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, characterized in that: The N+ type buried layer (9) is made of GaN, the doping type is N type, and the doping concentration is 1×10 18 -1×10 21 cm -3 , thickness is 10-200nm.

4. The high linearity RF GaN-based HEMT device according to claim 1, characterized in that: 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 has a thickness of 50nm-500nm.

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

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) is composed 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 a 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 the barrier layer (5) and a portion of the channel layer (4); depositing the source electrode (8) and performing annealing treatment to form an ohmic contact between the source electrode and the N+ type buried layer (9); Step 8: depositing a gate electrode (7); Step 9: etching between the gate electrode (7) and the source electrode (8) to form a groove, completely etching away the barrier layer (5), and etching the groove 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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