Algan epitaxial structure, preparation method thereof and semiconductor device

Abstract

The application discloses an AlGaN epitaxial structure, a preparation method thereof and a semiconductor device. The AlGaN epitaxial structure comprises a substrate, a GaN epitaxial composite layer located on the substrate, the GaN epitaxial composite layer comprising GaN epitaxial process layers and SiN x insertion layers, at least a part of the GaN epitaxial composite layer being the alternately-stacked GaN epitaxial process layers and SiN x insertion layers; an AlGaN epitaxial composite layer located on the GaN epitaxial composite layer, the AlGaN epitaxial composite layer comprising AlGaN epitaxial process layers and MgN y insertion layers, at least a part of the AlGaN epitaxial composite layer being the alternately-stacked AlGaN epitaxial process layers and MgN y insertion layers; and an AlGaN epitaxial layer located on the AlGaN epitaxial composite layer. The above structure can realize crystal matching of the GaN epitaxial composite layer and the AlGaN epitaxial composite layer, provide a high-quality and low-stress growth template for the AlGaN epitaxial layer, and obtain a high-crystal-quality AlGaN epitaxial layer with low surface defects.

Description

Technical Field

[0001] This invention relates to the field of semiconductor epitaxial technology, and in particular to an AlGaN epitaxial structure, its fabrication method, and a semiconductor device thereof. Background Technology

[0002] AlGaN, as a wide bandgap semiconductor material, can achieve a continuously adjustable bandgap width between 3.4 eV and 6.2 eV. It is widely used in structures such as carrier blocking layers, ultraviolet light-emitting layers, and high electron gas heterojunctions, and has important application value in many fields.

[0003] Due to the lack of homogeneous substrates, AlGaN materials are usually grown using heterogeneous substrates. Because of the large difference in lattice constant and thermal expansion coefficient between AlGaN and the substrate, a large number of dislocations will be generated during the epitaxial growth process. At the same time, warping of the epitaxial film and even cracks will occur. This will directly lead to leakage current and other device failures. Summary of the Invention

[0004] The purpose of this invention is to provide an AlGaN epitaxial structure, its preparation method, and a semiconductor device, which can be used to provide a high-quality, low-stress growth template for AlGaN epitaxial layers to obtain high-crystal-quality AlGaN epitaxial layers with low surface defects.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] An AlGaN epitaxial structure, comprising:

[0007] Substrate;

[0008] A GaN epitaxial composite layer is located on the substrate, the GaN epitaxial composite layer comprising a GaN epitaxial layer and a SiN layer. x The insertion layer, wherein at least a portion of the GaN epitaxial composite layer is composed of alternating layers of GaN epitaxial process layers and SiN. x Insertion layer;

[0009] An AlGaN epitaxial composite layer is located on the GaN epitaxial composite layer, the AlGaN epitaxial composite layer comprising an AlGaN epitaxial process layer and MgN. y The insertion layer, wherein at least a portion of the AlGaN epitaxial composite layer is composed of alternating layers of AlGaN epitaxial process layers and MgN. y Insertion layer;

[0010] An AlGaN epitaxial layer is located on the AlGaN epitaxial composite layer.

[0011] In one specific embodiment, the thickness of the GaN epitaxial composite layer is 1-2 μm, the thickness of a single layer of the alternately stacked GaN epitaxial process layers is 10-100 nm, and the thickness of the alternately stacked SiN layers is... x The thickness of the inserted layer is 1-2 nm.

[0012] The thickness of the AlGaN epitaxial composite layer is 5-200 nm, the thickness of a single layer of the alternately stacked AlGaN epitaxial process layer is 1-10 nm, and the thickness of the alternately stacked MgN... y The thickness of the inserted layer is 0.5-1 nm.

[0013] The thickness of the AlGaN epitaxial layer is 20-2000 nm.

[0014] In one specific embodiment, in the GaN epitaxial composite layer, the total thickness of the alternately stacked GaN epitaxial process layers does not exceed one-half of the thickness of the GaN epitaxial composite layer;

[0015] In the AlGaN epitaxial composite layer, the total thickness of the alternately stacked AlGaN epitaxial process layers does not exceed one-half the thickness of the AlGaN epitaxial composite layer.

[0016] In one specific embodiment, the thickness of the non-alternating GaN epitaxial process layers in the GaN epitaxial composite layer is 0.5-1 μm;

[0017] In the AlGaN epitaxial composite layer, the thickness of the non-alternating AlGaN epitaxial process layers is 2.5-100 nm.

[0018] In one specific embodiment, the GaN epitaxial composite layer consists of alternating layers of GaN epitaxial process material and SiN. x The insertion layer is located above or below the non-alternating stacked GaN epitaxial process layers, or between two non-alternating stacked GaN epitaxial process layers;

[0019] In the AlGaN epitaxial composite layer, AlGaN epitaxial layers and MgN are alternately stacked. y The insertion layer is located above or below the non-alternating stacked AlGaN epitaxial process layers, or between two non-alternating stacked AlGaN epitaxial process layers.

[0020] In one specific embodiment, the surface roughness of the AlGaN epitaxial layer is 0.1-10 nm.

[0021] A method for preparing an AlGaN epitaxial structure, comprising:

[0022] Step S1: Provide a substrate;

[0023] Step S2: Grow a GaN epitaxial composite layer on the substrate, the GaN epitaxial composite layer comprising a GaN epitaxial layer and a SiN layer. x The insertion layer, wherein at least a portion of the GaN epitaxial composite layer is an alternating layer of GaN epitaxial material and SiN. x Insertion layer;

[0024] Step S3: Grow an AlGaN epitaxial composite layer on the GaN epitaxial composite layer, the AlGaN epitaxial composite layer comprising an AlGaN epitaxial process layer and MgN. y The insertion layer, wherein at least a portion of the AlGaN epitaxial composite layer comprises alternating AlGaN epitaxial layers and MgN. y Insertion layer;

[0025] Step S4: Grow an AlGaN epitaxial layer on the AlGaN epitaxial composite layer.

[0026] In one specific embodiment, step S2 includes:

[0027] First, a non-alternating GaN epitaxial layer is grown on the substrate. Then, an alternating GaN epitaxial layer and SiN are grown on the non-alternating GaN epitaxial layer. x Insert layer; or,

[0028] First, alternating layers of GaN epitaxial process and SiN are grown on the substrate. x Insertion layer, then on alternating layers of GaN epitaxial process and SiN x The GaN epitaxial layer is grown on the insertion layer in a non-alternating stack; or,

[0029] First, a non-alternating GaN epitaxial layer is grown on the substrate. Then, an alternating GaN epitaxial layer and SiN are grown on the non-alternating GaN epitaxial layer. x Insertion layer, finally on alternating GaN epitaxial layers and SiN x The GaN epitaxial process layer is grown on the insertion layer in a non-alternating stack.

[0030] In one specific embodiment, step S3 includes:

[0031] First, a non-alternating AlGaN epitaxial layer is grown on the substrate. Then, an alternating layer of AlGaN epitaxial layers and MgN is grown on the non-alternating AlGaN epitaxial layer. y Insert layer; or,

[0032] First, alternating AlGaN epitaxial layers and MgN are grown on the substrate.y Insertion layer, then on alternating layers of AlGaN epitaxial process and MgN y The AlGaN epitaxial layer is grown on the insertion layer in a non-alternating stack; or,

[0033] First, a non-alternating AlGaN epitaxial layer is grown on the substrate. Then, an alternating layer of AlGaN epitaxial layers and MgN is grown on the non-alternating AlGaN epitaxial layer. y Insertion layer, finally on alternating AlGaN epitaxial layers and MgN y The AlGaN epitaxial process layer is grown on the insertion layer in a non-alternating stack.

[0034] A semiconductor device comprising the AlGaN epitaxial structure described in any of the preceding claims.

[0035] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0036] By setting up a GaN epitaxial process layer and a SiN x GaN epitaxial composite layer with insertion layer and containing AlGaN epitaxial process layer and MgN y The AlGaN epitaxial composite layer with an insertion layer utilizes the difference in atomic radii (Mg > Si) to introduce SiN into the GaN epitaxial composite layer. x Insertion layers can adjust the lattice constant of GaN epitaxial composite layers to be closer to that of AlGaN, introducing MgN into the AlGaN epitaxial composite layer. y The insertion layer can adjust the lattice constant of the AlGaN epitaxial composite layer to be closer to that of GaN, thereby achieving crystal matching between the GaN and AlGaN epitaxial composite layers. This provides a high-quality, low-stress growth template for the AlGaN epitaxial layer, ultimately resulting in a high-crystal-quality AlGaN epitaxial layer with low surface defects.

[0037] Furthermore, in this invention, the formed SiN x Insertion layer and MgN y The insertion layer process can avoid the impact of changes in material conductivity caused by adjusting the lattice constant in conventional GaN and AlGaN doping processes, thus broadening the application fields of AlGaN epitaxial layers. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of an AlGaN epitaxial structure according to an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the AlGaN epitaxial structure according to another embodiment of the present invention.

[0040] Figure 3This is a schematic diagram of the AlGaN epitaxial structure according to another embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the AlGaN epitaxial structure according to another embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the AlGaN epitaxial structure according to another embodiment of the present invention.

[0043] Figure 6 This is a schematic flowchart of the method for preparing the AlGaN epitaxial structure according to an embodiment of the present invention.

[0044] Figure 7 This is an optical microscope image of the AlGaN epitaxial structure of Embodiment 1 of the present invention.

[0045] Figure 8 This is an optical microscope image of the AlGaN epitaxial structure of Comparative Example 1 of this invention.

[0046] In the figure: 10, substrate; 20, GaN epitaxial composite layer; 21, non-alternating GaN epitaxial process layer; 22, GaN epitaxial process layer; 23, SiN. x 30. Insertion layer; 31. AlGaN epitaxial composite layer; 32. Non-alternating stacked AlGaN epitaxial process layer; 33. AlGaN epitaxial process layer; 34. SiN x Insertion layer; 40. AlGaN epitaxial layer. Detailed Implementation

[0047] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0048] The terms used to express position and direction in this invention are illustrated with reference to the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.

[0049] Reference Figure 1-5 The present invention provides an AlGaN epitaxial structure comprising a substrate 10, a GaN epitaxial composite layer 20, an AlGaN epitaxial composite layer 30 and an AlGaN epitaxial layer 40 stacked sequentially.

[0050] The substrate 10 may be a sapphire substrate, or it may be formed of zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN) or the like.

[0051] The GaN epitaxial composite layer 20 is located on the substrate 10, and the GaN epitaxial composite layer 20 includes a GaN epitaxial process layer and a SiN layer. x Insertion layer 23, 0≤x≤1, at least a portion of the GaN epitaxial composite layer 20 consists of alternating layers of GaN epitaxial process layer 22 and SiN. x Insertion layer 23. Specifically, the GaN epitaxial composite layer 20 may include a non-alternating stacked portion and an alternating stacked portion, which are stacked one on top of the other. The non-alternating stacked portion may include a non-alternating stacked GaN epitaxial process layer 21 (non-overlapping GaN epitaxial process layer 21), which can be obtained by a single epitaxial growth. The alternating stacked portion includes an alternating stacked GaN epitaxial process layer 22 and SiN. x Insertion layer 23, alternating GaN epitaxial layers 22 and SiN x Insertion layer 23 can be achieved by alternating epitaxial growth of GaN epitaxial layer 22 and SiN. x It is obtained by inserting layer 23.

[0052] The AlGaN epitaxial composite layer 30 is located on the GaN epitaxial composite layer 20, and the AlGaN epitaxial composite layer 30 includes an AlGaN epitaxial process layer and MgN. y Insertion layer 33, 0≤y≤1, at least a portion of the AlGaN epitaxial composite layer 30 consists of alternating layers of AlGaN epitaxial process layer 32 and MgN. y Insertion layer 33. Specifically, the AlGaN epitaxial composite layer 30 may include a non-alternating stacked portion and an alternating stacked portion, which are stacked one on top of the other. The non-alternating stacked portion may include a non-alternating stacked AlGaN epitaxial process layer 31 (non-overlapping AlGaN epitaxial process layer 31), which can be obtained by a single epitaxial growth. The alternating stacked portion includes an alternating stacked AlGaN epitaxial process layer 32 and MgN. y Insertion layer 33, alternating AlGaN epitaxial layer 32 and MgN y Insertion layer 33 can be achieved by alternating epitaxial growth of AlGaN epitaxial layer 32 and MgN. y It is obtained by inserting layer 33.

[0053] AlGaN epitaxial layer 40 is located on the AlGaN epitaxial composite layer 30.

[0054] Therefore, by setting up a GaN epitaxial process layer 22 and a SiN layer... x The GaN epitaxial composite layer 20 with insertion layer 23 and the layer containing AlGaN epitaxial process layer 32 and MgN y The AlGaN epitaxial composite layer 30 of the insertion layer 33 utilizes the difference in atomic radii (Mg > Si) to introduce SiN into the GaN epitaxial composite layer 20. x Insertion layer 23 can adjust the lattice constant of GaN epitaxial composite layer 20 to be closer to AlGaN, and introduce MgN into AlGaN epitaxial composite layer 30. y The insertion layer 33 can adjust the lattice constant of the AlGaN epitaxial composite layer 30 to be closer to GaN, which can achieve crystal matching between the GaN epitaxial composite layer 20 and the AlGaN epitaxial composite layer 30, providing a high-quality, low-stress growth template for the AlGaN epitaxial layer 40, and ultimately obtaining a high-crystal-quality AlGaN epitaxial layer 40 with low surface defects.

[0055] Furthermore, altering the lattice constants of the GaN epitaxial composite layer 20 and the AlGaN epitaxial composite layer 30 through doping processes will change the conductivity of the epitaxial composite layer. However, as the growth template for the AlGaN epitaxial layer 40, it is not desirable to change its conductivity. In this invention, the formed SiN... x Insertion layer 23 and MgN y The insertion layer 33 process can avoid the impact of changes in material conductivity caused by adjusting the lattice constant in conventional GaN and AlGaN doping processes, thus broadening the application fields of AlGaN epitaxial layer 40.

[0056] In one specific embodiment, the thickness of the GaN epitaxial composite layer 20 is 1-2 μm, for example, 1.3 μm, 1.5 μm, or 1.8 μm, and the thickness of a single layer of the alternately stacked GaN epitaxial process layer 22 is 10-100 nm, for example, 30 nm, 50 nm, or 80 nm, and the thickness of the alternately stacked SiN... x The thickness of the insertion layer 23 is 1-2 nm, for example, 1.3 nm, 1.5 nm, or 1.8 nm. SiN x Setting the thickness of the single layer of the insertion layer 23 to 1-2 nm is more conducive to adjusting the lattice constant of the GaN epitaxial composite layer 20 to be closer to AlGaN.

[0057] The thickness of the AlGaN epitaxial composite layer 30 is 5-200 nm, for example, 50 nm, 100 nm, or 150 nm. The thickness of a single layer of the alternately stacked AlGaN epitaxial process layer 32 is 1-10 nm, for example, 3 nm, 5 nm, or 8 nm. The thickness of the alternately stacked MgN... yThe thickness of the insertion layer 33 is 0.5-1 nm, for example, 0.6 nm, 0.8 nm, or 0.9 nm. The AlGaN epitaxial composite layer 30 with a thickness of 5-200 nm, combined with the GaN epitaxial composite layer 20 with a thickness of 1-2 μm, can effectively alleviate the lattice mismatch between the substrate 10 and the AlGaN epitaxial layer 40, improving the quality of the crystal grown on the substrate 10. MgN... y Setting the thickness of the single layer of the insertion layer 33 to 0.5-1 nm is more conducive to adjusting the lattice constant of the AlGaN epitaxial composite layer 30 to be closer to GaN, thereby achieving crystal matching between the GaN epitaxial composite layer 20 and the AlGaN epitaxial composite layer 30.

[0058] The thickness of the AlGaN epitaxial layer 40 is 20-2000nm, for example, 100nm, 300nm, 500nm, 1000nm, 1300nm, 1500nm or 1800nm.

[0059] In one specific embodiment, in the GaN epitaxial composite layer 20, the total thickness of the alternately stacked GaN epitaxial process layers 22 does not exceed half the thickness of the GaN epitaxial composite layer 20. The thickness of the non-alternatingly stacked GaN epitaxial process layers 22 is preferably 0.5-1 μm, for example, 0.6 μm, 0.8 μm, or 0.9 μm. In the AlGaN epitaxial composite layer 30, the total thickness of the alternately stacked AlGaN epitaxial process layers 32 does not exceed half the thickness of the AlGaN epitaxial composite layer 30. The thickness of the non-alternatingly stacked AlGaN epitaxial process layers 31 is preferably 2.5-100 nm, for example, 10 nm, 30 nm, 50 nm, or 80 nm.

[0060] In one specific implementation, such as Figure 1-3 As shown, in the GaN epitaxial composite layer 20, the GaN epitaxial process layer 22 and SiN are alternately stacked. x The insertion layer 23 is located above or below the non-alternating stacked GaN epitaxial process layers 21, or between two non-alternating stacked GaN epitaxial process layers 21.

[0061] like Figure 1 , 4 As shown in Figure 5, in the AlGaN epitaxial composite layer 30, AlGaN epitaxial process layers 32 and MgN are alternately stacked. y The insertion layer 33 is located above or below the non-alternating stacked AlGaN epitaxial process layers 31, or between two non-alternating stacked AlGaN epitaxial process layers 31.

[0062] By changing the alternating stacked GaN epitaxial process layer 22 and SiN xThe position of the insertion layer 23, or by changing the alternating stacked AlGaN epitaxial process layers 32 and MgN... y The position of the insertion layer 33 can adjust the surface roughness of the AlGaN epitaxial layer 40. The surface roughness of the AlGaN epitaxial layer 40 can be adjusted within the range of 0.1-10nm, thereby separating the surface roughening process from the crystal quality process control, and thus expanding the epitaxial growth process window for surface roughening of the epitaxial layer to meet different epitaxial technology requirements.

[0063] In the GaN epitaxial composite layer 20, the total thickness of the alternately stacked GaN epitaxial process layers 22 does not exceed half the thickness of the GaN epitaxial composite layer 20. Similarly, in the AlGaN epitaxial composite layer 30, the total thickness of the alternately stacked AlGaN epitaxial process layers 32 does not exceed half the thickness of the AlGaN epitaxial composite layer 30. The maximum thickness is limited here based on actual production processes. This is because if the thickness of the epitaxial process layers exceeds half, the SiN… x Insertion layer 23 and MgN y The insertion layer 33 cannot play a role in lattice adjustment of the GaN epitaxial process layer and the AlGaN epitaxial process layer. On the other hand, when the thickness of the epitaxial process layer exceeds one-half, the surface roughness of the AlGaN epitaxial layer 40 is not significantly affected by the insertion position of the overlapping layer in the non-overlapping layer, and it is impossible to achieve the process of changing the surface roughness simply by the insertion position.

[0064] The present invention also provides a semiconductor device comprising the AlGaN epitaxial structure described in any of the above embodiments, wherein the semiconductor device is, for example, an LED device, a HEMT device, etc.

[0065] like Figure 6 As shown, the present invention also provides a method for preparing an AlGaN epitaxial structure, comprising the following steps: steps S1-S4, wherein the preparation of the AlGaN epitaxial structure can be completed using an MOCVD epitaxial growth device.

[0066] Step S1: Provide substrate 10.

[0067] The substrate 10 may be a sapphire substrate, or it may be formed of zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN) or the like.

[0068] Step S2: Grow a GaN epitaxial composite layer 20 on the substrate 10. The GaN epitaxial composite layer 20 includes a GaN epitaxial process layer and a SiN layer. x Insertion layer 23, at least a portion of the GaN epitaxial composite layer 20 is composed of alternating GaN epitaxial process layers 22 and SiN. xInsertion layer 23.

[0069] Specifically, under temperature conditions of 1095-1125℃ and pressure conditions of 150-350 torr, a GaN epitaxial composite layer 20 with a thickness of 1-2 μm is grown on the substrate 10, which may include steps S201 and S202.

[0070] Step S201: Grow a non-alternating GaN epitaxial layer 21 with a thickness of 0.5-1 μm.

[0071] Step S202: Periodically and alternately grow a GaN epitaxial layer 22 with a thickness of 10-100 nm and a SiN layer with a thickness of 1-2 nm. x The total thickness of the GaN epitaxial process layer 22 during the insertion layer 23 cycle is preferably no more than half the thickness of the GaN epitaxial composite layer 20.

[0072] Step S202 can be performed after, before, or between two steps S201, thereby alternating the stacked GaN epitaxial layers 22 and SiN... x The insertion layer 23 is located above or below the non-alternating stacked GaN epitaxial process layers 21, or between two non-alternating stacked GaN epitaxial process layers 21, thereby adjusting the surface roughness of the AlGaN epitaxial layer 40.

[0073] Specifically, step S2 may include:

[0074] First, a non-alternating GaN epitaxial layer 21 is grown on the substrate 10. Then, an alternating GaN epitaxial layer 22 and SiN are grown on the non-alternating GaN epitaxial layer 21. x Insertion layer 23.

[0075] Alternatively, alternating layers of GaN epitaxial process layer 22 and SiN can be grown on the substrate 10 first. x Insertion layer 23, followed by alternating GaN epitaxial layers 22 and SiN x The GaN epitaxial layer 21, which is not alternately stacked, is grown on the insertion layer 23.

[0076] Alternatively, a non-alternating GaN epitaxial layer 21 may be grown on the substrate 10 first, and then an alternating GaN epitaxial layer 22 and SiN may be grown on the non-alternating GaN epitaxial layer 21. x Insertion layer 23, and finally, alternating GaN epitaxial layers 22 and SiN. x The GaN epitaxial layer 21, which is not alternately stacked, is grown on the insertion layer 23.

[0077] Step S3: Grow an AlGaN epitaxial composite layer 30 on the GaN epitaxial composite layer 20, wherein the AlGaN epitaxial composite layer 30 includes an AlGaN epitaxial process layer and MgN. y Insertion layer 33, at least a portion of the AlGaN epitaxial composite layer 30 is composed of alternating AlGaN epitaxial process layers 32 and MgN. y Insertion layer 33.

[0078] Specifically, under temperature conditions of 1065-1095℃ and pressure conditions of 50-150 torr, an AlGaN epitaxial composite layer 30 with a thickness of 5-200 nm is grown on the GaN epitaxial composite layer 20, which may include steps S301 and S302.

[0079] Step S301: Grow a non-alternating AlGaN epitaxial layer 31 with a thickness of 2.5-100nm.

[0080] Step S302: Periodically and alternately grow AlGaN epitaxial layer 32 with a thickness of 1-10 nm and MgN with a thickness of 0.5-1 nm. y The total thickness of the AlGaN epitaxial process layer 32 during the insertion layer 33 cycle is preferably no more than half the thickness of the AlGaN epitaxial composite layer 30.

[0081] Step S302 can be performed after, before, or between two steps S301, thereby alternatingly stacking the AlGaN epitaxial layers 32 and MgN. y The insertion layer 33 is located above or below the non-alternating AlGaN epitaxial process layer 31, or between two non-alternating AlGaN epitaxial process layers 31, thereby adjusting the surface roughness of the AlGaN epitaxial layer 40.

[0082] Specifically, step S3 may include:

[0083] First, a non-alternating AlGaN epitaxial layer 31 is grown on the substrate 10. Then, an alternating AlGaN epitaxial layer 32 and MgN are grown on the non-alternating AlGaN epitaxial layer 31. y Insertion layer 33.

[0084] Alternatively, alternating AlGaN epitaxial layers 32 and MgN can be grown on the substrate 10 first. y Insertion layer 33, followed by alternating AlGaN epitaxial layers 32 and MgN y A non-alternating AlGaN epitaxial layer 31 is grown on the insertion layer 33.

[0085] Alternatively, a non-alternating AlGaN epitaxial layer 31 may be grown on the substrate 10 first, and then an alternating AlGaN epitaxial layer 32 and MgN may be grown on the non-alternating AlGaN epitaxial layer 31. y Insertion layer 33, and finally, alternating AlGaN epitaxial layer 32 and MgN. y A non-alternating AlGaN epitaxial layer 31 is grown on the insertion layer 33.

[0086] Step S4: Grow an AlGaN epitaxial layer 40 on the AlGaN epitaxial composite layer 30.

[0087] Specifically, under temperature conditions of 1085-1115℃ and pressure conditions of 50-150 torr, an AlGaN epitaxial layer 40 with a thickness of 20-2000 nm is grown on the AlGaN epitaxial composite layer 30.

[0088] Example 1:

[0089] The preparation of AlGaN epitaxial structures using MOCVD epitaxial growth equipment includes:

[0090] Step S11: Provide a sapphire substrate 10.

[0091] Step S21: Under conditions of 1105℃ temperature and 200 orr pressure, a 1.5 μm GaN epitaxial composite layer 20 is grown on substrate 10, including the following steps:

[0092] First, on substrate 10, a GaN epitaxial layer 22 with a thickness of 50 nm and a SiN layer with a thickness of 1.5 nm are periodically and alternately grown. x Insertion layer 23, the total thickness of the GaN epitaxial process layer during the cycle is 20% of the thickness of the GaN composite layer;

[0093] Then, in the alternating GaN epitaxial layer 22 and SiN x On the insertion layer 23, a non-alternating GaN epitaxial layer 21 with a thickness of 0.6 μm is grown.

[0094] Step S31: Under conditions of 1075℃ and 100 torr pressure, an AlGaN epitaxial composite layer 30 with a thickness of 100 nm is grown on the GaN epitaxial composite layer 20, including the following steps:

[0095] First, on the GaN epitaxial composite layer 20, a 5nm thick AlGaN epitaxial layer 32 and a 0.8nm thick MgN layer are periodically and alternately grown. y Insertion layer 33, the total thickness of AlGaN epitaxial process layer 32 in the cycle is 20% of the thickness of AlGaN epitaxial composite layer 30;

[0096] Then, in the alternating AlGaN epitaxial process layer 32 and MgN y On the insertion layer 33, a non-alternating AlGaN epitaxial layer 31 with a thickness of 80 nm is grown.

[0097] Step S41: Under the conditions of 1095℃ temperature and 120 torr pressure, grow an AlGaN epitaxial layer 40 with a thickness of 1000nm on the AlGaN epitaxial composite layer 30.

[0098] Example 2:

[0099] The preparation process of Example 2 is basically the same as that of Example 1, except that step S21 is different.

[0100] Step S21:

[0101] First, a non-alternating GaN epitaxial layer 21 with a thickness of 0.6 μm is grown on the substrate 10;

[0102] Then, on the non-alternating GaN epitaxial layer 21, a GaN epitaxial layer 22 with a single layer thickness of 50 nm and a SiN layer with a single layer thickness of 1.5 nm are periodically and alternately grown. x Insertion layer 23, the total thickness of the GaN epitaxial process layer in the cycle is 20% of the thickness of the GaN composite layer.

[0103] Example 3:

[0104] The preparation process of Example 3 is basically the same as that of Example 1, except that step S21 is different.

[0105] Step S21:

[0106] First, a non-alternating GaN epitaxial layer 21 with a thickness of 0.3 μm is grown on substrate 10.

[0107] Then, on the non-alternating GaN epitaxial layer 21, a GaN epitaxial layer 22 with a single layer thickness of 50 nm and a SiN layer with a single layer thickness of 1.5 nm are periodically and alternately grown. x Insertion layer 23, the total thickness of the GaN epitaxial process layer in the cycle is 20% of the thickness of the GaN composite layer.

[0108] Finally, alternating GaN epitaxial layers 22 and SiN... x A non-alternating GaN epitaxial layer 21 with a thickness of 0.3 μm is grown on the insertion layer 23.

[0109] Example 4:

[0110] The preparation process of Example 4 is basically the same as that of Example 1, except that step S31 is different.

[0111] Step S31:

[0112] First, an AlGaN epitaxial process layer 31 with a thickness of 80 nm is grown on the GaN epitaxial composite layer 20, which is a non-alternating stacked layer.

[0113] Then, on the non-alternating AlGaN epitaxial layer 31, AlGaN epitaxial layer 32 with a single layer thickness of 5 nm and MgN with a single layer thickness of 0.8 nm are periodically and alternately grown. y Insertion layer 33, the total thickness of the AlGaN epitaxial process layer in the cycle is 20% of the thickness of the AlGaN composite layer.

[0114] Example 5:

[0115] The preparation process of Example 3 is basically the same as that of Example 1, except that step S31 is different.

[0116] Step S31:

[0117] First, a non-alternating AlGaN epitaxial layer 31 with a thickness of 40 nm is grown on the GaN epitaxial composite layer 20.

[0118] Then, on the non-alternating AlGaN epitaxial layer 31, AlGaN epitaxial layer 32 with a single layer thickness of 5 nm and MgN with a single layer thickness of 0.8 nm are periodically and alternately grown. y Insertion layer 33, the total thickness of the AlGaN epitaxial process layer in the cycle is 20% of the thickness of the AlGaN composite layer.

[0119] Finally, alternating AlGaN epitaxial layers 32 and MgN were applied. y An AlGaN epitaxial layer 31 with a thickness of 40 nm is grown on the insertion layer 33.

[0120] The bow value, surface roughness Ra, (002) and 102 half-peak width were measured for the AlGaN epitaxial structures of Examples 1 to 5, respectively. The results are shown in Table 1:

[0121] Table 1

[0122] Example bow / μm Ra / nm 002 / arsec 102 / arsec Example 1 58 0.76 242 278 Example 2 57 3.97 245 276 Example 3 58 2.12 248 277 Example 4 59 5.89 248 279 Example 5 59 3.47 247 276

[0123] As can be seen from the data in Table 1, the thickness of the alternating GaN and AlGaN layers mainly affects the surface roughness of the AlGaN epitaxial structure. As the overlapping layers approach the surface of the epitaxial structure, the roughness gradually increases, and as the overlapping layers move away from the surface of the epitaxial structure, the roughness gradually decreases. Furthermore, the bow value and the full width at half maximum (FWHM) of the (002) and 102 layers of the epitaxial structure do not change significantly with the position of the inserted layers. This allows the surface roughening process to be separated from the crystal quality process control, thereby expanding the epitaxial growth process window for surface roughening of the epitaxial layers and meeting different epitaxial technology requirements.

[0124] Comparative Example 1:

[0125] The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that steps S21 and S31 are different.

[0126] In step S21, no SiN was grown in the GaN epitaxial composite layer 20. x Insertion layer 23.

[0127] In step S31, MgN was not grown in the AlGaN epitaxial composite layer 30. y Insertion layer 33.

[0128] Comparative Example 2:

[0129] The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that step S21 is different.

[0130] In step S21, the total thickness of the GaN epitaxial process layer during the cycle is 60% of the thickness of the GaN composite layer.

[0131] Comparative Example 3:

[0132] The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that step S21 is different.

[0133] In step S21, the total thickness of the GaN epitaxial process layer during the cycle is 80% of the thickness of the GaN composite layer.

[0134] Comparative Example 4:

[0135] The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that step S31 is different.

[0136] In step S31, the total thickness of the AlGaN epitaxial process layer 32 in the cycle is 60% of the thickness of the AlGaN epitaxial composite layer 30.

[0137] Comparative Example 5

[0138] In step S31, the total thickness of the AlGaN epitaxial process layer 32 in the cycle is 80% of the thickness of the AlGaN epitaxial composite layer 30.

[0139] The bow value, surface roughness Ra, (002) and 102 half-width at half-maximum (WWHM) of the AlGaN epitaxial structures of Example 1 and Comparative Examples 1-5 were measured respectively. The results are shown in Table 2.

[0140] Table 2

[0141] Example bow / μm Ra / nm 002 / arsec 102 / arsec Example 1 58 0.76 242 278 Comparative Example 1 76 0.73 297 351 Comparative Example 2 62 0.68 249 281 Comparative Example 3 66 0.67 254 289 Comparative Example 4 68 0.77 256 291 Comparative Example 5 70 0.76 262 295

[0142] As can be seen from the table above, the bow values ​​(bending) of the AlGaN epitaxial structures obtained by photoluminescence PL testing in Comparative Example 1 and Example 1 were 58 μm and 76 μm, respectively. Figure 7 The optical microscope images of the AlGaN epitaxial structures shown indicate that the AlGaN epitaxial structure of Example 1 has a smooth epitaxial surface, and the full width at half maximum (FWHM) values ​​of XRD tests (002) and (102) are 242 arsec and 278 arsec, respectively. In contrast, Comparative Example 1 has a pit-like defect distribution, and the FWHM values ​​of XRD tests (002) and (102) are 297 arsec and 351 arsec, respectively. This indicates that the GaN and AlGaN epitaxial composite layer structure of the present invention has a lower bow value. That is, by using Example 1 of the present invention, crystal matching of the GaN epitaxial composite layer and the AlGaN epitaxial composite layer can be achieved, providing a high-quality, low-stress growth template for the AlGaN epitaxial layer, and a high-crystal-quality AlGaN epitaxial layer with low surface defects can be obtained.

[0143] In Comparative Examples 2, 3, 4, and 5, the thickness proportions of GaN and AlGaN epitaxial process layers in the cycle are all greater than half (50%). The test data shows that the bow value, (002) and (102) half-peak widths in Comparative Examples 2, 3, 4, and 5 all show an increasing trend. This indicates that in the GaN epitaxial composite layer 20, the total thickness of the alternately stacked GaN epitaxial process layers 22 does not exceed half the thickness of the GaN epitaxial composite layer 20, and in the AlGaN epitaxial composite layer 30, the total thickness of the alternately stacked AlGaN epitaxial process layers 32 does not exceed half the thickness of the AlGaN epitaxial composite layer 30. SiN... x Insertion layer 23 and MgN y The insertion layer 33 cannot play a role in lattice adjustment of the GaN epitaxial process layer and the AlGaN epitaxial process layer; in addition, according to actual production experience, when the thickness of the alternating epitaxial process layer exceeds one-half, the surface roughness is not significantly affected by the insertion position of the overlapping layer in the non-overlapping layer, and it is impossible to achieve the process of changing the surface roughness simply by the insertion position.

[0144] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. An AlGaN epitaxial structure, characterized by, The application relates to an AlGaN epitaxial structure, which comprises: a substrate; GaN epitaxial composite layer, located on the substrate, the GaN epitaxial composite layer comprising GaN epitaxial process layers and SiN x insertion layer, at least a portion of the GaN epitaxial composite layer being alternately stacked GaN epitaxial process layers and SiN x insertion layer, the total thickness of the alternately stacked GaN epitaxial process layers not exceeding one-half of the thickness of the GaN epitaxial composite layer; An AlGaN epitaxial composite layer is located on the GaN epitaxial composite layer, and the AlGaN epitaxial composite layer comprises an AlGaN epitaxial process layer and MgN y An intercalated layer, at least a portion of the AlGaN epitaxial composite layer is an alternating layer of the AlGaN epitaxial process layer and MgN y An intercalated layer, the total thickness of the alternating layer of the AlGaN epitaxial process layer is not more than one half of the thickness of the AlGaN epitaxial composite layer; an AlGaN epitaxial layer on the AlGaN epitaxial composite layer.

2. The AlGaN epitaxial structure according to claim 1, wherein: The thickness of the GaN epitaxial composite layer is 1-2 μm, the thickness of a single layer of the alternately stacked GaN epitaxial process layer is 10-100 nm, and the thickness of a single layer of the alternately stacked SiN x The thickness of a single layer of the interposed layer is 1-2 nm. The thickness of the AlGaN epitaxial composite layer is 5-200nm, the single layer thickness of the alternately stacked AlGaN epitaxial process layer is 1-10nm, the single layer thickness of the alternately stacked MgN y The single layer thickness of the intercalation layer is 0.5-1nm; the thickness of the AlGaN epitaxial layer is 20-2000 nm.

3. The AlGaN epitaxial structure according to claim 1, wherein: in the GaN epitaxial composite layer, the thickness of the non-alternating stacked GaN epitaxial process layer is 0.5-1 mu m; in the AlGaN epitaxial composite layer, the thickness of the non-alternating stacked AlGaN epitaxial process layer is 2.5-100 nm.

4. The AlGaN epitaxial structure according to claim 1, wherein: In the GaN epitaxial composite layer, the GaN epitaxial process layers and SiN x The insertion layer is located above or below the GaN epitaxial process layers which are not alternately stacked, or is located between two GaN epitaxial process layers which are not alternately stacked. In the AlGaN epitaxial composite layer, the AlGaN epitaxial process layers and MgN are alternately stacked y The insertion layer is located above or below the non-alternately stacked AlGaN epitaxial process layer, or between two non-alternately stacked AlGaN epitaxial process layers.

5. The AlGaN epitaxial structure of claim 1, wherein the surface roughness of the AlGaN epitaxial layer is 0.1-10 nm.

6. A method of producing an AlGaN epitaxial structure, the method being used to produce an AlGaN epitaxial structure as claimed in any one of claims 1 to 5, characterized by, The application further relates to a preparation method of the AlGaN epitaxial structure. The preparation method comprises: Step S2: growing a GaN epitaxial composite layer on the substrate, the GaN epitaxial composite layer comprising GaN epitaxial process layers and SiN x interposed layers, at least a portion of the GaN epitaxial composite layer being alternatingly grown GaN epitaxial process layers and SiN x interposed layers; Step S3: growing an AlGaN epitaxial composite layer on the GaN epitaxial composite layer, the AlGaN epitaxial composite layer comprising AlGaN epitaxial process layers and MgN y interposed layers, at least a portion of the AlGaN epitaxial composite layer being alternatingly grown AlGaN epitaxial process layers and MgN y interposed layers; S1, providing a substrate; 7. The method of claim 6, wherein the AlGaN epitaxial structure is prepared by a method comprising: S4, growing an AlGaN epitaxial layer on the AlGaN epitaxial composite layer. The non-alternately-stacked GaN epitaxial process layer is grown on the substrate first, and then the alternately-stacked GaN epitaxial process layer and SiN are grown on the non-alternately-stacked GaN epitaxial process layer x An interposed layer; or, GaN epitaxial process layers and SiN are grown on the substrate in an alternating layer stack x an interposed layer, and then the GaN epitaxial process layers are grown on the interposed layer in a non-alternating layer stack x an interposed layer, and then the GaN epitaxial process layers are grown on the interposed layer in a non-alternating layer stack GaN epitaxial process layers are grown on the substrate in a non-alternate stack, and then GaN epitaxial process layers and SiN x insertion layers, and finally GaN epitaxial process layers in an alternate stack are grown on the GaN epitaxial process layers and SiN x insertion layers.

8. The method of claim 6, wherein the AlGaN epitaxial structure is prepared by a method comprising: The step S2 comprises: The AlGaN epitaxial process layer is grown on the substrate in a non-alternate layer stack, and the AlGaN epitaxial process layer and MgN are grown on the non-alternate layer stack in an alternate layer stack y an intercalation layer; or, growing an AlGaN epitaxial process layer and MgN y inserting a layer, and then growing an AlGaN epitaxial process layer and MgN y growing a non-alternating layer of the AlGaN epitaxial process layer on the inserted layer; or, The AlGaN epitaxial process layer is grown on the substrate in a non-alternate layer stack, and the AlGaN epitaxial process layer and MgN in an alternate layer stack are grown on the non-alternate layer stack of the AlGaN epitaxial process layer y The AlGaN epitaxial process layer is grown on the substrate in a non-alternate layer stack, and the AlGaN epitaxial process layer and MgN in an alternate layer stack are grown on the non-alternate layer stack of the AlGaN epitaxial process layer y The AlGaN epitaxial process layer is grown on the substrate in a non-alternate layer stack, and the AlGaN epitaxial process layer and MgN in an alternate layer stack are grown on the non-alternate layer stack of the AlGaN epitaxial process layer 9. A semiconductor device, characterized by comprising: The step S3 comprises: The application further relates to an AlGaN epitaxial structure according to any one of claims 1-5.

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