A GaN-based HEMT device epitaxial structure and a preparation method thereof

Abstract

The application provides a GaN-based HEMT device epitaxial structure and a preparation method thereof. The GaN-based HEMT device epitaxial structure comprises, from bottom to top, a substrate, a composite high-resistance layer, a channel layer, a barrier layer and a cap layer; the composite high-resistance layer comprises, from bottom to top, a GaN nucleation layer, a first multilayer structure, an Mg layer and a second multilayer structure; the first multilayer structure comprises alternately stacked In-doped AlN layers and C-doped GaN layers; and the second multilayer structure comprises, from bottom to top, an Mg diffusion barrier layer, a stress release layer and a C-doped GaN high-resistance layer. By arranging an independent Mg layer in the composite high-resistance layer, a composite high-resistance layer system with double deep energy level compensation of 'Mg non-activation + C doping' is formed, so that the leakage current of the device can be significantly reduced, and the linearity and long-term reliability of the device can be improved under the premise of ensuring the high resistivity of the composite high-resistance layer.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing technology, specifically relating to a GaN-based HEMT device epitaxial structure and its fabrication method. Background Technology

[0002] Gallium nitride-based high electron mobility transistors (GaN-based HEMT devices) have broad application prospects in fields such as radio frequency communication, power electronics, and microwave power amplification due to their advantages such as wide bandgap, high breakdown electric field, and high carrier mobility. The epitaxial structure of a conventional GaN-based HEMT device typically includes, from bottom to top, a substrate, a buffer layer, a channel layer, a barrier layer, and a capping layer. The buffer layer functions to bridge the lattice and thermal mismatch between the substrate and the channel layer, and to provide high resistance characteristics to effectively isolate the leakage current path between the substrate and the channel layer, thereby reducing parasitic effects and leakage current, and improving the device's operating stability and breakdown characteristics.

[0003] In existing technologies, to achieve high-resistivity buffer layers, carbon (C) is typically incorporated into the buffer layer. By controlling the C doping concentration, the buffer layer can exhibit a weak p-type characteristic, meeting device requirements. However, research has found that relying solely on high-concentration C doping (doping concentration > 2 × 10⁻⁶) is insufficient. 18 cm -3 The technical solutions for achieving high resistance in the buffer layer have many drawbacks: 1) Excessive C doping will introduce a large number of lattice distortions and point defects into the GaN crystal, significantly degrading the crystal quality and increasing the defect density of the epitaxial layer; 2) Excessive C doping is prone to precipitation under the drive of internal stress in the GaN lattice, forming C element aggregation regions or C source stacking layers, which leads to an abnormal increase in leakage current and a sharp rise in local junction temperature under high voltage operation. Furthermore, the increase in junction temperature will accelerate the proliferation and expansion of defects, causing the linear characteristics of the device to deteriorate and electrical nonlinear changes to occur, which seriously restricts the reliability and long-term stability of the device.

[0004] Therefore, how to reduce the leakage current of GaN-based HEMT devices and improve their stability and reliability is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a GaN-based HEMT device epitaxial structure and its fabrication method. The present invention establishes an independent Mg layer within the composite high-resistivity layer of the GaN-based HEMT device epitaxial structure, and constructs a first multilayer stacked structure and a second multilayer stacked structure above and below it, respectively, forming a composite high-resistivity layer system with dual deep-level compensation of "Mg inactivation + C doping". Specifically, by utilizing the downward diffusion characteristic of Mg, the first multilayer stacked structure at the bottom of the Mg layer achieves a low-doping effect of C, which helps to achieve higher resistivity performance. Furthermore, the diffused Mg in the first multilayer stacked structure does not possess activation conditions. The first multilayer stacked structure provides C doping elements; after C doping replaces nitrogen sites, it forms deep-level acceptors located above the valence band, effectively capturing free electrons and compensating for background n-type carriers. Therefore, the unactivated Mg-related deep levels and C-related deep levels can synergistically constitute a dual deep-level compensation system, capturing background n-type carriers and resulting in a higher degree of carrier compensation and a significant reduction in free carrier concentration. Simultaneously, the combination of C deep levels and unactivated Mg-related deep levels pushes the Fermi level further into the valence band, achieving a deeper Fermi level pinning effect. Therefore, this invention can significantly reduce the leakage current of the device and improve its linearity and long-term reliability while maintaining the high resistivity of the composite high-resistivity layer.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a GaN-based HEMT device epitaxial structure, the GaN-based HEMT device epitaxial structure comprising, from bottom to top, a substrate, a composite high-resistivity layer, a channel layer, a barrier layer and a capping layer.

[0007] The composite high-resistivity layer comprises, from bottom to top, a GaN nucleation layer, a first multilayer stacked structure, a Mg layer, and a second multilayer stacked structure; the first multilayer stacked structure comprises alternating layers of C-doped AlN and C-doped GaN, and the second multilayer stacked structure comprises, from bottom to top, a Mg diffusion barrier layer, a stress relief layer, and a C-doped GaN high-resistivity layer.

[0008] This invention forms a composite high-resistivity layer system with dual deep-level compensation by setting an independent Mg layer in the composite high-resistivity layer of the epitaxial structure of a GaN-based HEMT device, and constructing a first multilayer stacked structure and a second multilayer stacked structure above and below it, respectively. Specifically, by utilizing the downward diffusion characteristic of Mg, the first multilayer stacked structure at the bottom of the Mg layer achieves a low-doping effect of C, which helps to achieve higher resistance performance, and the diffused Mg in the first multilayer stacked structure does not have the activation conditions; the first multilayer stacked structure provides C doping elements, and after C doping elements replace nitrogen sites, they can form deep-level acceptors located above the top of the valence band, which can effectively capture free electrons and compensate for background n-type carriers; therefore, the unactivated Mg-related deep level and the C-related deep level can synergistically constitute a dual deep-level compensation system, and the background n-type carriers are captured by it, resulting in a higher degree of carrier compensation and a significant reduction in the concentration of free carriers; at the same time, the combination of the C deep level and the unactivated Mg-related deep level pushes the Fermi level further into the valence band, realizing a deeper Fermi level pinning effect. Therefore, this invention can significantly reduce the leakage current of the device and improve its linearity and long-term reliability while ensuring the high resistivity of the composite high-resistivity layer.

[0009] Due to the diffusion compensation effect of Mg, this invention can achieve high resistance characteristics at a relatively low C doping concentration, effectively avoiding the crystal quality degradation and C precipitation accumulation problems caused by high C doping concentration, and improving the crystal quality of the epitaxial layer. On the other hand, the Mg diffusion barrier layer in the second multilayer stacked structure effectively inhibits the upward diffusion of Mg elements into the channel layer, avoiding the adverse effects of Mg on the channel characteristics. The stress relief layer effectively alleviates the stress accumulation inside the multilayer stacked structure, further ensuring the overall stability of the epitaxial structure.

[0010] This invention can significantly reduce the leakage current of the device and improve its linearity and long-term reliability while ensuring the high resistivity of the composite high-resistivity layer.

[0011] Preferably, the thickness of the Mg layer is 2-3 nm, for example, it can be 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm or 3 nm.

[0012] In this invention, under the Mg layer of the above-mentioned suitable thickness, the downward diffusion effect of Mg can be used to achieve a shallow doping effect, which is beneficial to make the composite high-resistivity layer close to the weak P-type and the intrinsic withstand voltage effect is higher.

[0013] Preferably, the thickness of the GaN nucleation layer is 15-30nm, for example, it can be 15nm, 18nm, 20nm, 22nm, 25nm, 28nm or 30nm.

[0014] Preferably, the GaN nucleation layer is doped with C element, and the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×10 17 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0015] Preferably, in the C-doped AlN layer, the C doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×10 17 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0016] Preferably, in the C-doped GaN layer, the C doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×10 17 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0017] Preferably, the first multilayer stacked structure includes a first C-doped AlN layer, a first C-doped GaN layer, a second C-doped AlN layer, a second C-doped GaN layer, and a third C-doped AlN layer arranged sequentially from bottom to top.

[0018] Preferably, the thickness of the first C-doped AlN layer is 10-25 nm, for example, it can be 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 24 nm or 25 nm.

[0019] Preferably, the thickness of the second C-doped AlN layer is 5-8 nm, for example, it can be 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm or 8 nm.

[0020] Preferably, the thickness of the third C-doped AlN layer is 3-5 nm, for example, it can be 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm.

[0021] Preferably, the thickness of the first C-doped GaN layer is 5-8 nm, for example, it can be 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm or 8 nm.

[0022] Preferably, the thickness of the second C-doped GaN layer is 3-5 nm, for example, it can be 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm.

[0023] Preferably, the Mg diffusion barrier layer comprises a fourth C-doped AlN layer, a third C-doped GaN layer, and a fifth C-doped AlN layer arranged sequentially from bottom to top.

[0024] By setting the Mg diffusion barrier layer of the above-mentioned stacked structure, the present invention can block the upward diffusion of Mg and avoid contaminating the channel layer.

[0025] Preferably, the stress relief layer comprises a fourth C-doped GaN layer.

[0026] Preferably, the thickness of the C-doped GaN high-resistivity layer is 300-500 nm, for example, it can be 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm or 500 nm.

[0027] Preferably, in the C-doped GaN high-resistivity layer, the C element doping concentration is 1×10⁻⁶. 18 cm -3 -1.5×10 18 cm -3 For example, it could be 1×10 18 cm -3 1.1×10 18 cm -3 1.2×10 18 cm -3 1.35×10 17 cm -3 Or 1.5×1018 cm -3 wait.

[0028] Preferably, the thickness of the fourth C-doped AlN layer is 3-5 nm, for example, it can be 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm.

[0029] Preferably, in the fourth C-doped AlN layer, the C doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×10 17 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0030] Preferably, the thickness of the fifth C-doped AlN layer is 8-15 nm, for example, it can be 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm or 15 nm.

[0031] Preferably, in the fifth C-doped AlN layer, the C doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×10 17 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0032] Preferably, the thickness of the third C-doped GaN layer is 3-5 nm, for example, it can be 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm.

[0033] Preferably, in the third C-doped GaN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 For example, it could be 1×10 17 cm -3 3×1017 cm -3 5×10 17 cm -3 7×10 17 cm -3 9×10 17 cm -3 Or 5×10 16 cm -3 wait.

[0034] Preferably, the thickness of the fourth C-doped GaN layer is 20-50 nm, for example, it can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0035] Preferably, in the fourth C-doped GaN layer, the C doping concentration is 1.5 × 10⁻⁶. 18 cm -3 -2.5×10 18 cm -3 For example, it could be 1.5 × 10 18 cm -3 1.75×10 18 cm -3 2×10 18 cm -3 2.25×10 17 cm -3 Or 2.5×10 18 cm -3 wait.

[0036] Preferably, the substrate includes any one of a sapphire substrate, a silicon carbide substrate, or a silicon substrate.

[0037] Preferably, the thickness of the channel layer is 200-500nm, for example, it can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, etc.

[0038] Preferably, the channel layer comprises a GaN channel layer.

[0039] Preferably, the thickness of the barrier layer is 10-60nm, for example, it can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm or 60nm, etc.

[0040] Preferably, the barrier layer comprises an AlGaN barrier layer.

[0041] Preferably, the capping layer comprises a p-doped GaN capping layer or a silicon nitride capping layer. The thickness of the p-doped GaN capping layer can be, for example, 30-150 nm, such as 30 nm, 50 nm, 100 nm, or 150 nm, and the thickness of the silicon nitride capping layer can be, for example, 5-10 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm.

[0042] In a second aspect, the present invention provides a method for fabricating a GaN-based HEMT device epitaxial structure as described in the first aspect, the method comprising the following steps: Provide substrate.

[0043] A composite high-resistivity layer, a channel layer, a barrier layer, and a capping layer are sequentially deposited on the substrate to obtain the epitaxial structure of the GaN-based HEMT device.

[0044] The composite high-resistivity layer comprises, from bottom to top, a GaN nucleation layer, a first multilayer stacked structure, a Mg layer, and a second multilayer stacked structure; the first multilayer stacked structure comprises alternating layers of In-doped AlN and C-doped GaN, and the second multilayer stacked structure comprises, from bottom to top, a Mg diffusion barrier layer, a stress relief layer, and a C-doped GaN high-resistivity layer.

[0045] In the preparation method of this invention, the Mg layer is grown in a low-temperature, non-hydrogen atmosphere. At least a portion of the Mg element diffuses downwards into the first multilayer stacked structure below it. Since the entire composite high-resistivity layer is grown in a H2-rich and low-pressure environment and subsequently covered by the channel layer, the Mg diffused into the first multilayer stacked structure does not possess the electrical activation conditions and exists as an unactivated deep-level trap state. Thus, the unactivated Mg-related deep levels and the deep-level acceptors (~0.9 eV) formed by C doping in the first multilayer stacked structure together constitute a dual deep-level compensation system. The total trap concentration is the sum of the two, resulting in more thorough carrier compensation and a significantly higher resistivity than structures using only single C doping or single Mg doping. Furthermore, the Mg diffusion barrier layer in the second multilayer stacked structure effectively prevents Mg from diffusing upwards, ensuring that the channel layer quality is not affected.

[0046] Preferably, the deposition methods for the composite high-resistivity layer, channel layer, barrier layer, and capping layer all include MOCVD. It should be noted that MOCVD refers to metal-organic chemical vapor deposition.

[0047] Preferably, the process parameters for depositing the Mg layer include: The Mg source includes organic Mg source, and the deposition temperature is 750-850℃, such as 750℃, 760℃, 780℃, 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃, etc. The deposition atmosphere is a non-hydrogen atmosphere.

[0048] Preferably, the process parameters for depositing the stress relief layer include: The deposition temperature is 750-850℃, for example, 750℃, 760℃, 780℃, 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃, etc. The deposition atmosphere is a hydrogen-rich atmosphere, the deposition rate is 2-3nm / min, for example, 2nm / min, 2.2nm / min, 2.4nm / min, 2.6nm / min, 2.8nm / min or 3nm / min, etc., and the deposition pressure is 150-200Torr, for example, 150Torr, 155Torr, 160Torr, 165Torr, 170Torr, 175Torr, 180Torr, 185Torr, 190Torr, 195Torr or 200Torr, etc.

[0049] Preferably, the process parameters for depositing the C-doped GaN high-resistivity layer include: The deposition temperature is 1025-1100℃, for example, it can be 1025℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃ or 1100℃, etc. The deposition atmosphere is a hydrogen-rich atmosphere, and the deposition pressure is 150-200 Torr, for example, it can be 150 Torr, 155 Torr, 160 Torr, 165 Torr, 170 Torr, 175 Torr, 180 Torr, 185 Torr, 190 Torr, 195 Torr or 200 Torr, etc.

[0050] Preferably, the preparation method includes the following steps: (1) Provide a substrate.

[0051] A GaN nucleation layer with a thickness of 15-30 nm was deposited on the substrate using MOCVD. The GaN nucleation layer was doped with carbon (C) at a concentration ≤ 1 × 10⁻⁶. 18 cm -3 .

[0052] (2) Using the MOCVD method, a first C-doped AlN layer with a thickness of 10-25 nm, a first C-doped GaN layer with a thickness of 5-8 nm, a second C-doped AlN layer with a thickness of 5-8 nm, a second C-doped GaN layer with a thickness of 3-5 nm and a third C-doped AlN layer with a thickness of 3-5 nm are sequentially deposited on the GaN nucleation layer to form a first multilayer stacked structure.

[0053] The deposition atmosphere of the first multilayer stacked structure is a hydrogen-rich atmosphere, with a deposition pressure of 50-100 Torr (e.g., 50 Torr, 55 Torr, 60 Torr, 65 Torr, 70 Torr, 75 Torr, 80 Torr, 85 Torr, 90 Torr, 95 Torr, or 100 Torr, etc.), and a deposition temperature of 1000-1050℃, e.g., 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, or 1050℃, etc.; the hydrogen-rich atmosphere comprises a volumetric flow rate ratio of (5-15):(75-85). ):(5-15) inert gas (e.g., nitrogen, etc.), hydrogen and ammonia (wherein, the inert gas selection range "5-15" can be 5, 10 or 15, etc., the hydrogen selection range "75-85" can be 75, 80 or 85, etc., and the ammonia selection range "5-15" can be 5, 10 or 15, etc.); TMI is also introduced into the first C-doped AlN layer, the second C-doped AlN layer and the third C-doped AlN layer during the deposition process (the purpose is to take advantage of the rapid decomposition and escape characteristics of TMI at high temperature to rapidly desorb and carry away the pre-reaction byproducts from the reaction chamber).

[0054] (3) A Mg layer with a thickness of 2-3 nm is deposited on the third C-doped AlN layer using MOCVD; the process parameters of the MOCVD method include: The Mg source includes organic Mg source, the deposition temperature is 750-850℃, and the deposition atmosphere is a non-hydrogen atmosphere.

[0055] Wherein, the organic Mg source is magnesium pyrocene; the non-hydrogen atmosphere includes an inert gas and ammonia, and the volume flow ratio of the inert gas and ammonia is (70-90):(10-30) (wherein, the inert gas can be, for example, nitrogen, etc., and the selection range of the inert gas "70-90" can be, for example, 70, 80 or 90, etc., and the selection range of the ammonia "10-30" can be, for example, 10, 20 or 30, etc.).

[0056] (4) Using the MOCVD method, a fourth C-doped AlN layer with a thickness of 3-5 nm, a third C-doped GaN layer with a thickness of 3-5 nm, and a fifth C-doped AlN layer with a thickness of 8-15 nm are sequentially deposited on the Mg layer to form a Mg diffusion barrier layer.

[0057] The deposition atmosphere of the Mg diffusion barrier layer is a hydrogen-rich atmosphere, with a deposition pressure of 50-100 Torr (e.g., 50 Torr, 60 Torr, 70 Torr, 80 Torr, 90 Torr, or 100 Torr, etc.) and a deposition temperature of 1000-1050℃ (e.g., 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, or 1050℃, etc.); the hydrogen-rich atmosphere contains a volumetric flow rate of (5... -15):(75-85):(5-15) inert gas (e.g., nitrogen, etc.), hydrogen and ammonia (wherein, the selection range of inert gas "5-15" can be 5, 10 or 15, etc., the selection range of hydrogen "75-85" can be 75, 80 or 85, etc., the selection range of ammonia "5-15" can be 5, 10 or 15, etc.); TMIn is also introduced during the deposition process of the fourth C-doped AlN layer and the fifth C-doped AlN layer.

[0058] (5) Using the MOCVD method, a fourth C-doped GaN layer with a thickness of 20-50 nm and a C-doped GaN high-resistivity layer with a thickness of 300-500 nm are sequentially deposited on the fifth C-doped AlN layer.

[0059] The process parameters for depositing the four-C doped GaN layer include: a deposition temperature of 750-850℃, a hydrogen-rich deposition atmosphere, a deposition rate of 2-3 nm / min, and a deposition pressure of 150-200 Torr.

[0060] The process parameters for depositing the C-doped GaN high-resistivity layer include: a deposition temperature of 1025-1100℃, a hydrogen-rich deposition atmosphere, and a deposition pressure of 150-200 Torr; the hydrogen-rich atmosphere includes an inert gas (e.g., nitrogen), hydrogen, and ammonia in a volumetric flow rate ratio of (20-30):(45-55):(20-30) (wherein, the inert gas selection range "20-30" can be, for example, 20, 25, or 30, the hydrogen selection range "45-55" can be, for example, 45, 50, or 55, and the ammonia selection range "20-30" can be, for example, 20, 25, or 30).

[0061] (6) Using the MOCVD method, a GaN channel layer with a thickness of 300-500 nm, an AlGaN barrier layer with a thickness of 10-60 nm and a capping layer are sequentially deposited on the C-doped GaN high-resistivity layer. The capping layer includes a P-doped GaN capping layer or a silicon nitride capping layer to obtain the epitaxial structure of the GaN-based HEMT device.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0063] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention forms a composite high-resistivity layer system with "Mg inactivation + C doping" dual deep-level compensation by setting an independent Mg layer in the composite high-resistivity layer of the epitaxial structure of GaN-based HEMT devices, and constructing a first multilayer stacked structure and a second multilayer stacked structure above and below it, respectively. Specifically, by utilizing the downward diffusion characteristics of Mg, the first multilayer stacked structure at the bottom of the Mg layer achieves the low-doping effect of Mg, which helps to achieve higher resistance performance, and the Mg diffused in the first multilayer stacked structure does not have the activation conditions; the first multilayer stacked structure provides C doping elements, and after C doping elements replace nitrogen sites, they can form deep-level acceptors located above the top of the valence band, which can effectively capture free electrons and compensate background n-type carriers; therefore, the unactivated Mg-related deep level and the C-related deep level can work together to form a dual deep-level compensation system, and the background n-type carriers are captured by it, resulting in a higher degree of carrier compensation and a significant reduction in the concentration of free carriers; at the same time, the combination of the C deep level and the unactivated Mg-related deep level pushes the Fermi level further into the valence band, realizing a deeper Fermi level pinning effect. Therefore, this invention can significantly reduce the leakage current of the device and improve its linearity and long-term reliability while ensuring the high resistivity of the composite high-resistivity layer.

[0064] (2) Due to the diffusion compensation effect of Mg, the present invention can obtain high resistance characteristics at a lower C doping concentration, effectively avoiding the crystal quality deterioration and C precipitation accumulation problems caused by high concentration C doping, and improving the crystal quality of the epitaxial layer; on the other hand, the Mg diffusion barrier layer in the second multilayer stacked structure effectively inhibits the upward diffusion of Mg elements into the channel layer, avoiding the adverse effects of Mg on the channel characteristics, while the stress relief layer effectively alleviates the stress accumulation inside the multilayer stacked structure, further ensuring the overall stability of the epitaxial structure.

[0065] (3) The present invention can significantly reduce the leakage current of the device and improve the linearity and long-term reliability of the device while ensuring the high resistivity of the composite high-resistivity layer. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the epitaxial structure of the GaN-based HEMT device provided in Embodiment 1 of the present invention.

[0067] Wherein, 1-sapphire substrate; 2-composite high-resistivity layer; 21-GaN nucleation layer; 22-first multilayer stacked structure; 221-first C-doped AlN layer; 222-first C-doped GaN layer; 223-second C-doped AlN layer; 224-second C-doped GaN layer; 225-third C-doped AlN layer; 23-Mg layer; 24-second multilayer stacked structure; 241-fourth C-doped AlN layer; 242-third C-doped GaN layer; 243-fifth C-doped AlN layer; 244-fourth C-doped GaN layer; 245-C-doped GaN high-resistivity layer; 3-GaN channel layer; 4-AlGaN barrier layer; 5-silicon nitride capping layer. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0069] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0070] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0071] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0072] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0073] Example 1 This embodiment provides an epitaxial structure for a GaN-based HEMT device, the schematic diagram of which is shown below. Figure 1As shown, the epitaxial structure of the GaN-based HEMT device includes, from bottom to top, a sapphire substrate 1, a composite high-resistivity layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, and a silicon nitride capping layer 5.

[0074] The composite high-resistivity layer 2 includes, from bottom to top, a GaN nucleation layer 21, a first multilayer stacked structure 22, a Mg layer 23, and a second multilayer stacked structure 24; the first multilayer stacked structure 22 includes, from bottom to top, a first C-doped AlN layer 221, a first C-doped GaN layer 222, a second C-doped AlN layer 223, a second C-doped GaN layer 224, and a third C-doped AlN layer 225; the second multilayer stacked structure 24 includes, from bottom to top, a fourth C-doped AlN layer 241, a third C-doped GaN layer 242, a fifth C-doped AlN layer 243, a fourth C-doped GaN layer 244, and a C-doped GaN high-resistivity layer 245.

[0075] The Mg layer 23 has a thickness of 2.5 nm; the GaN nucleation layer 21 has a thickness of 20 nm; and the GaN nucleation layer 21 is doped with C element at a concentration of 1 × 10⁻⁶. 18 cm -3 The thickness of the first C-doped AlN layer 221 is 20 nm, the thickness of the second C-doped AlN layer 223 is 6 nm, the thickness of the third C-doped AlN layer 225 is 4 nm, the thickness of the first C-doped GaN layer 222 is 6 nm, and the thickness of the second C-doped GaN layer 224 is 4 nm; the C doping concentration in the first C-doped AlN layer 221, the second C-doped AlN layer 223, and the third C-doped AlN layer 225 is 1 × 10⁻⁶. 18 cm -3 In both the first C-doped GaN layer 222 and the second C-doped GaN layer 224, the C doping concentration is 1 × 10⁻⁶. 18 cm -3 The fourth C-doped AlN layer 241 has a thickness of 4 nm and a C doping concentration of 1 × 10⁻⁶. 18 cm -3 The fifth C-doped AlN layer 243 has a thickness of 12 nm and a C doping concentration of 1 × 10⁻⁶. 18 cm -3 The thickness of the third C-doped GaN layer 242 is 4 nm, and the C doping concentration is 1 × 10⁻⁶. 18 cm -3 The fourth C-doped GaN layer 244 has a thickness of 35 nm and a C doping concentration of 2 × 10⁻⁶. 18 cm -3The thickness of the C-doped GaN high-resistivity layer 245 is 400 nm, and the C doping concentration is 1 × 10⁻⁶. 18 cm -3 The thickness of the GaN channel layer 3 is 350 nm; the thickness of the AlGaN barrier layer 4 is 35 nm; and the thickness of the silicon nitride capping layer 5 is 10 nm.

[0076] This embodiment also provides a method for fabricating the above-mentioned GaN-based HEMT device epitaxial structure, the method comprising the following steps: (1) Provide a sapphire substrate.

[0077] A 20 nm thick GaN nucleation layer was deposited on the sapphire substrate using MOCVD. The GaN nucleation layer was doped with carbon (C) at a concentration of 1 × 10⁻⁶. 18 cm -3 .

[0078] (2) Using the MOCVD method, a first C-doped AlN layer with a thickness of 20 nm, a first C-doped GaN layer with a thickness of 6 nm, a second C-doped AlN layer with a thickness of 6 nm, a second C-doped GaN layer with a thickness of 4 nm and a third C-doped AlN layer with a thickness of 4 nm are sequentially deposited on the GaN nucleation layer to form a first multilayer stacked structure.

[0079] The deposition atmosphere of the first multilayer stacked structure is a hydrogen-rich atmosphere with a deposition pressure of 75 Torr and a deposition temperature of 1025℃. The hydrogen-rich atmosphere includes nitrogen, hydrogen and ammonia in a volume flow ratio of 10:80:10. TMIn is also introduced into the first C-doped AlN layer, the second C-doped AlN layer and the third C-doped AlN layer during the deposition process.

[0080] (3) A Mg layer with a thickness of 2.5 nm is deposited on the third C-doped AlN layer using MOCVD; the process parameters of the MOCVD method include: The Mg source is magnesia-diocene, the deposition temperature is 825℃, and the deposition atmosphere is a non-hydrogen atmosphere; wherein, the non-hydrogen atmosphere includes nitrogen and ammonia in a volume flow ratio of 80:20.

[0081] (4) Using the MOCVD method, a fourth C-doped AlN layer with a thickness of 4 nm, a third C-doped GaN layer with a thickness of 4 nm, and a fifth C-doped AlN layer with a thickness of 10 nm are sequentially deposited on the Mg layer to form a Mg diffusion barrier layer.

[0082] The deposition atmosphere of the Mg diffusion barrier layer is a hydrogen-rich atmosphere, the deposition pressure is 75 Torr, and the deposition temperature is 1025℃. The hydrogen-rich atmosphere includes nitrogen, hydrogen, and ammonia in a volume flow ratio of 10:80:10. TMIn is also introduced into the fourth C-doped AlN layer and the fifth C-doped AlN layer during the deposition process.

[0083] (5) Using the MOCVD method, a fourth C-doped GaN layer with a thickness of 35 nm and a C-doped GaN high-resistivity layer with a thickness of 400 nm are sequentially deposited on the fifth C-doped AlN layer.

[0084] The process parameters for depositing the four-C doped GaN layer include: a deposition temperature of 800℃, a hydrogen-rich deposition atmosphere, a deposition rate of 2.5 nm / min, and a deposition pressure of 175 Torr; the hydrogen-rich atmosphere includes nitrogen, hydrogen, and ammonia in a volumetric flow rate ratio of 25:50:25.

[0085] The process parameters for depositing the C-doped GaN high-resistivity layer include: a deposition temperature of 1075°C, a hydrogen-rich deposition atmosphere, and a deposition pressure of 175 Torr; the hydrogen-rich atmosphere includes nitrogen, hydrogen, and ammonia in a volumetric flow rate ratio of 25:50:25.

[0086] (6) Using the MOCVD method, a GaN channel layer with a thickness of 400 nm, an AlGaN barrier layer with a thickness of 35 nm, and a silicon nitride capping layer are sequentially deposited on the C-doped GaN high-resistivity layer to obtain the epitaxial structure of the GaN-based HEMT device.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that no Mg layer is set, that is, step (3) is not performed.

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Performance testing The electrical performance of the GaN-based HEMT device epitaxial structures provided in the above embodiments and comparative examples was tested using the Hall effect test method, including sheet resistance (Rs) and mobility (Mob).

[0090] The test results are shown in Table 1.

[0091] Table 1 analyze: As can be seen from the comparison between Example 1 and Comparative Example 1, the Rs and Mob of the epitaxial structure provided by the present invention are optimized compared with the conventional structure. This is because the high concentration of C doping seriously degrades the crystal quality of the epitaxial structure. Not only can it not effectively suppress leakage current, but it may also introduce more leakage channels due to the decrease in crystal quality, ultimately damaging the performance and long-term reliability of the device.

[0092] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An epitaxial structure for a GaN-based HEMT device, characterized in that, The epitaxial structure of the GaN-based HEMT device includes, from bottom to top, a substrate, a composite high-resistivity layer, a channel layer, a barrier layer, and a capping layer. The composite high-resistivity layer comprises, from bottom to top, a GaN nucleation layer, a first multilayer stacked structure, a Mg layer, and a second multilayer stacked structure; the first multilayer stacked structure comprises alternating layers of C-doped AlN and C-doped GaN, and the second multilayer stacked structure comprises, from bottom to top, a Mg diffusion barrier layer, a stress relief layer, and a C-doped GaN high-resistivity layer.

2. The GaN-based HEMT device epitaxial structure according to claim 1, characterized in that, The thickness of the Mg layer is 2-3 nm.

3. The GaN-based HEMT device epitaxial structure according to claim 1, characterized in that, The thickness of the GaN nucleation layer is 15-30 nm; And / or, the GaN nucleation layer is doped with C element, and the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, in the C-doped AlN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, in the C-doped GaN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, the first multilayer stacked structure includes a first C-doped AlN layer, a first C-doped GaN layer, a second C-doped AlN layer, a second C-doped GaN layer and a third C-doped AlN layer arranged sequentially from bottom to top.

4. The GaN-based HEMT device epitaxial structure according to claim 3, characterized in that, The thickness of the first C-doped AlN layer is 10-25 nm; And / or, the thickness of the second C-doped AlN layer is 5-8 nm; And / or, the thickness of the third C-doped AlN layer is 3-5 nm; And / or, the thickness of the first C-doped GaN layer is 5-8 nm; And / or, the thickness of the second C-doped GaN layer is 3-5 nm.

5. The GaN-based HEMT device epitaxial structure according to claim 1, characterized in that, The Mg diffusion barrier layer includes a fourth C-doped AlN layer, a third C-doped GaN layer, and a fifth C-doped AlN layer arranged sequentially from bottom to top. And / or, the stress relief layer includes a fourth C-doped GaN layer; And / or, the thickness of the C-doped GaN high-resistivity layer is 300-500 nm; And / or, in the C-doped GaN high-resistivity layer, the C element doping concentration is 1.0 × 10⁻⁶. 18 cm -3 -1.5×10 18 cm -3 .

6. The GaN-based HEMT device epitaxial structure according to claim 5, characterized in that, The thickness of the fourth C-doped AlN layer is 3-5 nm; And / or, in the fourth C-doped AlN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, the thickness of the fifth C-doped AlN layer is 8-15 nm; And / or, in the fifth C-doped AlN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, the thickness of the third C-doped GaN layer is 3-5 nm; And / or, in the third C-doped GaN layer, the C element doping concentration is ≤1×10⁻⁶. 18 cm -3 ; And / or, the thickness of the fourth C-doped GaN layer is 20-50 nm; And / or, in the fourth C-doped GaN layer, the C doping concentration is 1.5 × 10⁻⁶. 18 cm -3 -2.5×10 18 cm -3 .

7. The GaN-based HEMT device epitaxial structure according to claim 1, characterized in that, The substrate includes any one of a sapphire substrate, a silicon carbide substrate, or a silicon substrate; And / or, the thickness of the channel layer is 200-500 nm; And / or, the channel layer includes a GaN channel layer; And / or, the thickness of the barrier layer is 10-60 nm; And / or, the barrier layer includes an AlGaN barrier layer; And / or, the capping layer includes a P-doped GaN capping layer or a silicon nitride capping layer.

8. A method for fabricating a GaN-based HEMT device epitaxial structure as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: Provide substrate; A composite high-resistivity layer, a channel layer, a barrier layer, and a capping layer are sequentially deposited on the substrate to obtain the epitaxial structure of the GaN-based HEMT device. The composite high-resistivity layer comprises, from bottom to top, a GaN nucleation layer, a first multilayer stacked structure, a Mg layer, and a second multilayer stacked structure; the first multilayer stacked structure comprises alternating layers of C-doped AlN and C-doped GaN, and the second multilayer stacked structure comprises, from bottom to top, a Mg diffusion barrier layer, a stress relief layer, and a C-doped GaN high-resistivity layer.

9. The preparation method according to claim 8, characterized in that, The deposition methods for the composite high-resistivity layer, channel layer, barrier layer, and capping layer all include MOCVD. And / or, the process parameters for depositing the Mg layer include: The Mg source includes organic Mg source, the deposition temperature is 750-850℃, and the deposition atmosphere is a non-hydrogen atmosphere; And / or, the process parameters for depositing the stress-relieving layer include: The deposition temperature was 750-850℃, the deposition atmosphere was hydrogen-rich, the deposition rate was 2-3 nm / min, and the deposition pressure was 150-200 Torr. And / or, the process parameters for depositing the C-doped GaN high-resistivity layer include: The deposition temperature was 1025-1100℃, the deposition atmosphere was hydrogen-rich, and the deposition pressure was 150-200 Torr.

10. The preparation method according to claim 8, characterized in that, The preparation method includes the following steps: (1) Provide a substrate; A GaN nucleation layer with a thickness of 15-30 nm was deposited on the substrate using MOCVD. The GaN nucleation layer was doped with carbon (C) at a concentration ≤ 1 × 10⁻⁶. 18 cm -3 ; (2) Using the MOCVD method, a first C-doped AlN layer with a thickness of 10-25 nm, a first C-doped GaN layer with a thickness of 5-8 nm, a second C-doped AlN layer with a thickness of 5-8 nm, a second C-doped GaN layer with a thickness of 3-5 nm and a third C-doped AlN layer with a thickness of 3-5 nm are sequentially deposited on the GaN nucleation layer to form a first multilayer stacked structure; The deposition atmosphere of the first multilayer stacked structure is a hydrogen-rich atmosphere, the deposition pressure is 50-100 Torr, and the deposition temperature is 1000-1050℃; the hydrogen-rich atmosphere includes inert gas, hydrogen, and ammonia in a volume flow ratio of (5-15):(75-85):(5-15); TMIn is also introduced into the first C-doped AlN layer, the second C-doped AlN layer, and the third C-doped AlN layer during the deposition process; (3) A Mg layer with a thickness of 2-3 nm is deposited on the third C-doped AlN layer using MOCVD; the process parameters of the MOCVD method include: The Mg source includes organic Mg source, the deposition temperature is 750-850℃, and the deposition atmosphere is a non-hydrogen atmosphere; Wherein, the organic Mg source is magnesium pyrocene; the non-hydrogen atmosphere includes an inert gas and ammonia, and the volume flow ratio of the inert gas and ammonia is (70-90):(10-30); (4) Using MOCVD, a fourth C-doped AlN layer with a thickness of 3-5 nm, a third C-doped GaN layer with a thickness of 3-5 nm, and a fifth C-doped AlN layer with a thickness of 8-15 nm are sequentially deposited on the Mg layer to form a Mg diffusion barrier layer. The deposition atmosphere of the Mg diffusion barrier layer is a hydrogen-rich atmosphere, the deposition pressure is 50-100 Torr, and the deposition temperature is 1000-1050℃; the hydrogen-rich atmosphere includes an inert gas, hydrogen, and ammonia with a volume flow ratio of (5-15):(75-85):(5-15); TMIn is also introduced into the fourth C-doped AlN layer and the fifth C-doped AlN layer during the deposition process; (5) Using MOCVD, a fourth C-doped GaN layer with a thickness of 20-50 nm and a C-doped GaN high-resistivity layer with a thickness of 300-500 nm are sequentially deposited on the fifth C-doped AlN layer. The process parameters for depositing the four-C doped GaN layer include: a deposition temperature of 750-850℃, a hydrogen-rich atmosphere, a deposition rate of 2-3 nm / min, and a deposition pressure of 150-200 Torr. The process parameters for depositing the C-doped GaN high-resistivity layer include: a deposition temperature of 1025-1100℃, a hydrogen-rich deposition atmosphere, and a deposition pressure of 150-200 Torr; the hydrogen-rich atmosphere includes an inert gas, hydrogen, and ammonia in a volumetric flow rate ratio of (20-30):(45-55):(20-30). (6) Using the MOCVD method, a GaN channel layer with a thickness of 300-500 nm, an AlGaN barrier layer with a thickness of 10-60 nm and a capping layer are sequentially deposited on the C-doped GaN high-resistivity layer. The capping layer includes a P-doped GaN capping layer or a silicon nitride capping layer to obtain the epitaxial structure of the GaN-based HEMT device.

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