Gallium oxide epitaxial structure and preparation method thereof, and solar blind ultraviolet detector

Abstract

Embodiments of the present application relate to a gallium oxide epitaxial structure, a preparation method thereof, and a solar blind ultraviolet detector. The gallium oxide epitaxial structure comprises a substrate, a buffer layer and a gallium oxide layer which are sequentially stacked. In a direction away from the substrate, the buffer layer comprises a first buffer layer, a second buffer layer and a third buffer layer which are sequentially stacked. The first buffer layer comprises a plurality of first cycle units, each of which comprises an AlN layer and an AlGaO layer which are sequentially stacked, and 0 < x < 1. The second buffer layer comprises a plurality of second cycle units, each of which comprises an AlGaO layer and an AlGaO layer which are sequentially stacked, and 0 < y < x. The third buffer layer comprises a plurality of third cycle units, each of which comprises an AlGaO layer and an AlGaO layer which are sequentially stacked, and 0 < z < y. In this way, a gallium oxide thin film with low cost, large-scale application and high quality can be obtained, and the performance and reliability of the device can be significantly improved. x Ga 1‑x O x Ga 1‑x O y Ga 1‑y O y Ga 1‑y O z Ga 1‑z O

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a gallium oxide epitaxial structure and its preparation method, and a solar-blind ultraviolet detector. Background Technology

[0002] Gallium oxide (Ga2O3) possesses advantages such as an ultra-wide bandgap (4.8 eV~4.9 eV), high breakdown field strength (8 MV / cm), and a high Barica figure of merit, demonstrating significant advantages in power electronic devices and ultraviolet optoelectronic devices. Based on this, on the one hand, gallium oxide materials exhibit high voltage withstand capability and low power consumption, making them widely used in high-temperature, high-frequency, and high-power power electronic devices. On the other hand, gallium oxide-based solar-blind ultraviolet detection technology offers advantages such as strong anti-interference capability, high sensitivity, and low background noise, showing broad and important application prospects in environmental monitoring, solar-blind imaging, flame detection, missile early warning and secure communications, and biomedical applications.

[0003] Currently, the main problem restricting the development of gallium oxide devices is the low crystal quality of existing gallium oxide epitaxial growth materials, especially in heteroepitaxial growth, where gallium oxide suffers from severe lattice and thermal mismatches with the substrate. For example, the lattice mismatch of ε-Ga₂O₃ grown directly on silicon (111) is approximately 24%, and the thermal mismatch is approximately 209%. Therefore, achieving low-cost, large-scale, and high-quality heteroepitaxial gallium oxide films is crucial for the industrial application of gallium oxide. Summary of the Invention

[0004] In view of this, the present application provides a gallium oxide epitaxial structure and its preparation method, as well as a solar-blind ultraviolet detector, to solve at least one problem existing in the background art.

[0005] In a first aspect, embodiments of this application provide a gallium oxide epitaxial structure, comprising: a substrate, a buffer layer, and a gallium oxide layer sequentially stacked; Along the direction away from the substrate, the buffer layer includes a first buffer layer, a second buffer layer and a third buffer layer stacked sequentially. The first buffer layer includes multiple first loop units, each of which includes a stacked AlN layer and an Al layer. x Ga 1-x Layer O, where 0 < x < 1; the starting layer of the first buffer layer is the AlN layer, and the ending layer of the first buffer layer is the Al layer. x Ga 1-x O layer; The second buffer layer includes a plurality of second loop units, each of which includes the stacked A1. x Ga 1-xO layer and Al y Ga 1-y Layer O, where 0 < y < x; the starting layer of the second buffer layer is the Al. x Ga 1-x Layer O, the termination layer of the second buffer layer is the Al. y Ga 1-y O layer; The third buffer layer includes multiple third loop units, each of which includes stacked A1 units. y Ga 1-y O layer and Al z Ga 1-z Layer O, and 0 < z < y; the starting layer of the third buffer layer is the Al. y Ga 1-y Layer O, the termination layer of the third buffer layer is the Al layer. z Ga 1-z O layer.

[0006] In conjunction with the first aspect of this application, in an alternative embodiment, the Al x Ga 1-x In layer O, 0.85 ≤ x ≤ 0.95; the Al y Ga 1-y In layer O, 0.75 ≤ y ≤ 0.85; the Al z Ga 1-z In layer O, 0.55≤z≤0.75.

[0007] In conjunction with the first aspect of this application, in an alternative embodiment, the Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer; the Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer; the Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer.

[0008] In conjunction with the first aspect of this application, in an optional embodiment, the Al component in the AlN layer and the Al x Ga 1-x The difference in the Al components in the O layer is d1, where Al x Ga 1-x The Al component in the O layer and the Al y Ga 1-y The difference in the Al components in the O layer is d2, where Aly Ga 1-y The Al component in the O layer and the Al z Ga 1-z The difference in Al composition in the O layer is d3; d1, d2 and d3 are all in the range of 0.1 to 0.2.

[0009] In conjunction with the first aspect of this application, in an alternative embodiment, the AlN layer, the Al x Ga 1-x O layer, the Al y Ga 1-y O layer and the Al z Ga 1-z The thickness of the O layer is in the range of 5nm to 15nm.

[0010] In conjunction with the first aspect of this application, in an optional embodiment, the thickness of the buffer layer is 500 nm to 800 nm.

[0011] In conjunction with the first aspect of this application, in an optional embodiment, the number of the first loop units is 5 to 10; the number of the second loop units is 5 to 10; and the number of the third loop units is 10 to 20.

[0012] Secondly, embodiments of this application provide a method for preparing a gallium oxide epitaxial structure, including: Provide substrate; A buffer layer is formed on the substrate, the buffer layer comprising a first buffer layer, a second buffer layer, and a third buffer layer sequentially stacked along a direction away from the substrate; wherein... The first buffer layer includes multiple first loop units, each of which includes a stacked AlN layer and an Al layer. x Ga 1-x Layer O, where 0 < x < 1; the starting layer of the first buffer layer is the AlN layer, and the ending layer of the first buffer layer is the Al layer. x Ga 1-x O layer; The second buffer layer includes a plurality of second loop units, each of which includes the stacked A1. x Ga 1-x O layer and Al y Ga 1-y Layer O, where 0 < y < x; the starting layer of the second buffer layer is the Al. x Ga 1-x Layer O, the termination layer of the second buffer layer is the Al. y Ga 1-y O layer; The third buffer layer includes multiple third loop units, each of which includes stacked A1 units. y Ga 1-y O layer and Al z Ga 1-z Layer O, and 0 < z < y; the starting layer of the third buffer layer is the Al. y Ga 1-y Layer O, the termination layer of the third buffer layer is the Al layer. z Ga 1-z O layer; A gallium oxide layer is formed on the buffer layer.

[0013] In conjunction with a second aspect of this application, in an optional embodiment, the step of forming a buffer layer on the substrate satisfies at least one of the following features: (1) The Al x Ga 1-x In layer O, 0.85 ≤ x ≤ 0.95; the Al y Ga 1-y In layer O, 0.75 ≤ y ≤ 0.85; the Al z Ga 1-z In layer O, 0.55 ≤ z ≤ 0.75; (2) The Al component in the AlN layer and the Al x Ga 1-x The difference in the Al components in the O layer is d1, where Al x Ga 1- x The Al component in the O layer and the Al y Ga 1-y The difference in the Al components in the O layer is d2, where Al y Ga 1-y The Al component in the O layer and the Al z Ga 1-z The difference in Al composition in the O layer is d3; d1, d2, and d3 are all in the range of 0.1 to 0.2. (3) The AlN layer, the Al x Ga 1-x O layer, the Al y Ga 1-y O layer and the Al z Ga 1-z The thickness of the O layer is in the range of 5nm to 15nm; (4) The thickness of the buffer layer is 500nm~800nm; (5) The number of the first loop unit is 5 to 10; the number of the second loop unit is 5 to 10; and the number of the third loop unit is 10 to 20.

[0014] Thirdly, embodiments of this application provide a solar-blind ultraviolet detector, including a gallium oxide epitaxial structure as described in any one of the first aspects of this application or a gallium oxide epitaxial structure prepared by a method for preparing a gallium oxide epitaxial structure as described in any one of the second aspects of this application.

[0015] Compared with the prior art, this application has the following beneficial effects: In the gallium oxide epitaxial structure provided in the embodiments of this application, a first buffer layer, a second buffer layer, and a third buffer layer with decreasing average Al composition are sequentially disposed between the substrate and the gallium oxide layer. The first buffer layer uses AlN / Al x Ga 1-x O-cycle, this layer can alleviate the stress caused by large lattice mismatch between the substrate and the gallium oxide layer; the second buffer layer, made of Al x Ga 1-x O / Al y Ga 1-y The O-cycle, based on the change in average Al composition, introduces a stress field change that can induce slip deflection of residual penetrating dislocations, promote dislocation bending annihilation, and achieve secondary dislocation filtering; the third buffer layer uses Al y Ga 1-y O / Al z Ga 1-z The O cycle further reduces the average Al composition, which can further filter out residual through dislocations and provide a low mismatch growth substrate for the gallium oxide layer, so that the gallium oxide layer has both low dislocation density and high crystal quality.

[0016] In summary, the gallium oxide epitaxial structure provided in this application releases the lattice mismatch stress between the substrate and the gallium oxide layer layer by layer by setting a buffer layer, while simultaneously inducing the bending annihilation of penetrating dislocations, thereby simultaneously achieving stress release and dislocation density reduction. In this way, a low-cost, scalable, and high-quality gallium oxide thin film can be obtained, thereby significantly improving the performance and reliability of the device.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1This is a cross-sectional schematic diagram of the gallium oxide epitaxial structure provided in the embodiments of this application; Figure 2 An atomic force microscope image of a gallium oxide epitaxial structure provided in an embodiment of this application; Figure 3 Atomic force microscopy images of gallium oxide epitaxial structures provided for related technologies; Figure 4 This is a schematic flowchart illustrating the method for preparing gallium oxide epitaxial structures according to embodiments of this application. Detailed Implementation

[0019] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the disclosure of the present application to those skilled in the art.

[0020] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, to avoid confusion with this application, some technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0021] In the accompanying drawings, for clarity, the dimensions of the structures and their relative dimensions may be exaggerated. The same reference numerals denote the same structural features throughout.

[0022] When structures are referred to as being "on," "adjacent to," "connected to," or "coupled to" other structures, they may be directly on, adjacent to, connected to, or coupled to other structures, or there may be intervening structures. Conversely, when a structure is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other structures, there are no intervening structures. Although the terms first, second, third, etc., may be used to describe structures or parts, these terms are only used to distinguish one structure or part from another. Therefore, without departing from the teachings of this application, the first structure or part discussed below may be referred to as the second structure or part. And the discussion of the second structure or part does not imply that the first structure or part necessarily exists in this application.

[0023] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship of one element or feature shown in the figure to other elements or features. In addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “under” the other element or feature will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated feature but do not exclude the presence or addition of one or more other features. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0025] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solution of this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0026] This application provides a gallium oxide epitaxial structure. Please refer to... Figure 1 The gallium oxide epitaxial structure includes a substrate 10, a buffer layer 20, and a gallium oxide layer 30 stacked sequentially.

[0027] Along the direction away from the substrate 10, the buffer layer 20 includes a first buffer layer 21, a second buffer layer 22, and a third buffer layer 23 stacked sequentially. The first buffer layer 21 includes a plurality of first circulation units A1, each of which includes a stacked AlN layer (aluminum nitride layer) and an Al... x Ga 1-x O layer (aluminum gallium oxide layer with aluminum composition x); the starting layer of the first buffer layer 21 is an AlN layer, and the ending layer of the first buffer layer 21 is an Al x Ga 1-x Layer O, where 0 < x < 1. The second buffer layer 22 includes multiple second loop units A2, each of which includes stacked Al. x Ga 1-x O layer and Al yGa 1-y The O layer (an aluminum gallium oxide layer with an aluminum composition of y), where 0 < y < x; the starting layer of the second buffer layer 22 is Al. x Ga 1-x Layer O, the termination layer of the second buffer layer 22 is Al. y Ga 1-y Layer O. The third buffer layer 23 includes multiple third loop units A3, each of which includes stacked A1. y Ga 1-y O layer and Al z Ga 1-z The O layer (an aluminum gallium oxide layer with an aluminum composition of z), where 0 < z < y; the starting layer of the third buffer layer 23 is Al. y Ga 1-y Layer O, the third buffer layer 23 terminates at layer Al. z Ga 1-z O layer.

[0028] It is understood that in the gallium oxide epitaxial structure provided in this application embodiment, a first buffer layer 21, a second buffer layer 22, and a third buffer layer 23 with decreasing average Al composition (aluminum composition) are sequentially disposed between the substrate 10 and the gallium oxide layer 30. The first buffer layer 21 is made of AlN / Al. x Ga 1-x O-cycle, this layer can alleviate the stress caused by large lattice mismatch between substrate 10 and gallium oxide layer 30; the second buffer layer 22, made of Al x Ga 1-x O / Al y Ga 1-y The O-cycle, based on the change in average Al composition, introduces a stress field change, which can induce the slip deflection of residual penetrating dislocations, promote dislocation bending annihilation, and achieve secondary dislocation filtering; the third buffer layer 23 uses Al y Ga 1-y O / Al z Ga 1-z The O cycle further reduces the average Al composition, which can further filter out residual through dislocations and provide a low mismatch growth substrate for the gallium oxide layer 30, so that the gallium oxide layer 30 has both low dislocation density and high crystal quality.

[0029] In summary, the gallium oxide epitaxial structure provided in this application releases the lattice mismatch stress between the substrate 10 and the gallium oxide layer 30 layer by layer by setting a buffer layer 20, while inducing the bending annihilation of penetrating dislocations, thereby simultaneously achieving stress release and dislocation density reduction. In this way, a low-cost, scalable, high-quality gallium oxide thin film can be obtained, thereby significantly improving the performance and reliability of the device.

[0030] In some embodiments, the substrate 10 may be a silicon (Si) substrate, a sapphire substrate, a silicon carbide (SiC) substrate, an alumina / aluminum nitride composite substrate (Al2O3 / AlN composite substrate), a silicon / aluminum nitride composite substrate (Si / AlN composite substrate), a silicon carbide / aluminum nitride composite substrate (SiC / AlN composite substrate), etc. For example, the substrate 10 is a silicon substrate.

[0031] In some embodiments, an AlN seed layer 101 (AlN crystal seed layer) is further included between the substrate 10 and the buffer layer 20. The AlN seed layer 101 can passivate surface defects and dangling bonds of the substrate 10, allowing the AlN layer in the buffer layer 20 to grow in a lattice template based on the AlN seed layer 101, thereby significantly reducing interface mismatch dislocations. For example, the thickness of the aluminum nitride seed layer 101 can be 5 nm to 50 nm.

[0032] In some embodiments, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The Al components x, y, and z in the O layer satisfy the following conditions: 0.85 ≤ x ≤ 0.95; 0.75 ≤ y ≤ 0.85; 0.55 ≤ z ≤ 0.75. For example, x can be 0.85, 0.87, 0.89, 0.91, 0.93, 0.95, etc.; y can be 0.75, 0.77, 0.79, 0.81, 0.83, 0.85, etc.; and z can be 0.55, 0.60, 0.65, 0.70, 0.75, etc.

[0033] It is understandable that Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The Al composition in the O layer is limited to the above-mentioned range, which can further optimize the stress field regulation effect inside each membrane layer in the buffer layer 20 and improve the dislocation filtering capability of the buffer layer 20.

[0034] Specifically, in the first buffer layer 21, Al x Ga 1-x The Al composition of the O layer and the AlN layer is close, resulting in a high degree of lattice matching between them. This further reduces the lattice mismatch between the first buffer layer 21 and the substrate 10, weakening the stress accumulation at the interface. Simultaneously, the first buffer layer 21 effectively blocks the upward propagation and extension of interface defects in the substrate 10, preventing defects from diffusing into the remaining buffer layers and the gallium oxide layer 30 above, thereby improving the crystal quality of the gallium oxide epitaxial structure. In the second buffer layer 22, Al... y Ga1-y The Al content in the O layer is lower than that in Al. x Ga 1-x In the O layer, the average Al composition of the second buffer layer 22 is lower than that of the first buffer layer 21. This change in average Al composition allows for a transition in the average lattice constant. This further alleviates the stress caused by lattice mismatch and effectively suppresses the generation and multiplication of through dislocations. The average Al composition of the third buffer layer 23 is further reduced, which improves the lattice matching between the third buffer layer 23 and the gallium oxide layer 30, thereby further improving the crystal quality of the gallium oxide layer 30.

[0035] In one specific embodiment, x is 0.9, y is 0.8, and z is 0.6. Based on this, Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer; Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer; Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer.

[0036] Understandably, according to Vegard's law, Al can be calculated. x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The free-state lattice constant *a* of the O-layer (hereinafter referred to as "AlGaO3 layer") is determined. Furthermore, based on the free-state lattice constant *a* of each AlGaO3 layer, the strain value *ε* of each AlGaO3 layer can be calculated. When |ε| ≥ 1%, in addition to high-density interfacial mismatch dislocations, the AlGaO3 layer will also exhibit severe surface roughening. Taking Al… z Ga 1-z Taking the Al composition variation of the O layer as an example, when z is 0.6, its strain value ε = -0.98%; when z decreases to 0.59, its strain value ε = -1.01%; and when z further decreases to 0.5, its strain value ε = -1.24%.

[0037] Based on this, the embodiments of this application further define x as 0.9, y as 0.8, and z as 0.6, which can reduce the interface mismatch dislocations between each aluminum gallium oxide layer, while ensuring that each aluminum gallium oxide layer maintains atomic-level surface flatness, thereby improving the crystal quality of the gallium oxide layer 30.

[0038] In some embodiments, the Al component in the AlN layer and Al xGa 1-x The difference in Al composition in the O layer is d1, Al x Ga 1- x Al components in the O layer and Al y Ga 1-y The difference in Al composition in the O layer is d2, Al y Ga 1-y Al components and Al in the O layer z Ga 1-z The difference in Al composition within the O layer is d3; d1, d2, and d3 are all within the range of 0.1 to 0.2. Specifically, d1, d2, and d3 can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, etc. Below, we will discuss the AlN layer and Al... x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The O layers are collectively referred to as "buffer sublayers".

[0039] Understandably, limiting d1, d2, and d3 to the range of 0.1 to 0.2 can prevent excessively large differences in Al composition between adjacent buffer sublayers, which could cause abrupt changes in interlayer lattice constants and thermal expansion coefficients, leading to a rapid accumulation of lattice mismatch stress and resulting in cracks, dislocations, and surface roughening. Simultaneously, it can also prevent excessively small differences in Al composition between adjacent buffer sublayers, which would lead to unclear boundaries between the buffer sublayers, weak Al composition modulation, and an inability to adequately control strain or prevent dislocations.

[0040] In some embodiments, the AlN layer, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The thickness of the O layer is in the range of 5nm to 15nm.

[0041] It is understood that limiting the thickness of each buffer sublayer within the aforementioned range ensures that, within the corresponding Al composition range, the geometric thickness of each buffer sublayer is strictly below its critical thickness, thereby forcing the entire buffer layer 20 to maintain a completely coherent elastic strain state. Specifically, when the thickness of the buffer sublayer is less than its critical thickness, the strain energy generated by lattice mismatch can be completely accommodated by elastic deformation without triggering strain relaxation. However, when the thickness of the buffer sublayer is greater than its critical thickness, the accumulated strain energy will exceed the elastic limit of the material, forcing the system to release excess energy through plastic deformation such as interfacial mismatch dislocations, surface roughening, or three-dimensional island growth, thereby introducing high-density dislocation lines and associated defects inside the buffer layer 20 and at the heterojunction interface. Therefore, this embodiment of the application strictly controls the thickness of each buffer sublayer to be below its critical thickness to avoid the generation of defects induced by strain relaxation as much as possible, thereby improving the crystal quality of the gallium oxide layer 30.

[0042] In one specific embodiment, Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer, Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer, Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer; AlN layer, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The thickness of the O layer is 10 nm.

[0043] In some embodiments, the thickness of the buffer layer 20 is 500nm to 800nm. For example, the thickness of the buffer layer 20 is 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, or 800nm.

[0044] Understandably, if the overall thickness of the buffer layer 20 is too large, while it facilitates sufficient stress release and dislocation bending filtering, it will increase the overall thermal resistance of the device, making it difficult to effectively dissipate the heat generated by the device. More seriously, heat accumulation will raise the internal temperature of the material, inducing a doubling of defects such as dislocations, severely degrading the reliability and lifespan of the device. If the overall thickness of the buffer layer 20 is too small, it will lead to insufficient stress release, making it difficult to effectively improve the surface morphology and internal crystal quality of the material. Therefore, limiting the thickness of the buffer layer 20 to 500nm~800nm ​​can both fully release stress and effectively block dislocations without significantly affecting the thermal diffusion performance.

[0045] In some embodiments, the number of first loop units A1 is 5 to 10, specifically, 5, 6, 7, 8, 9, or 10; the number of second loop units A2 is 5 to 10, specifically, 5, 6, 7, 8, 9, or 10; and the number of third loop units A3 is 10 to 20, specifically, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

[0046] It is understandable that by limiting the number of the above-mentioned cycle units, the overall thickness of the buffer layer 20 can be effectively controlled. At the same time, it can avoid the situation where too many cycles lead to interface stress overload and the generation of new dislocations, or that too few cycles lead to insufficient interface barrier and difficulty in driving through dislocations to bend and annihilate effectively.

[0047] Furthermore, the number of third cycle units A3 is greater than the number of first cycle units A1 and second cycle units A2. This increases the thickness of the third buffer layer 23, thereby improving the lattice matching degree between the third buffer layer 23 and the gallium oxide layer 30, and thus improving the crystal quality of the gallium oxide layer 30.

[0048] For example, Al x Ga 1-x O layer is Al 0.9 Ga 0.1 In layer O, the first loop unit A1 has 8 units; Al y Ga 1-y O layer is Al 0.8 Ga 0.2 In layer O, the second loop unit A2 has 8 units; Al z Ga 1-z O layer is Al 0.6 Ga 0.4 In layer O, the number of third loop units A3 is 15.

[0049] In some embodiments, the starting layer of the second buffer layer 22 and the ending layer of the first buffer layer 21 are two independent, sequentially stacked Al layers. x Ga 1-x Layer O; the starting layer of the third buffer layer 23 and the ending layer of the second buffer layer 22 are also two independent, sequentially stacked Al layers. y Ga 1-y O layer. The interfaces of two adjacent buffer layers 20 are connected by homogeneous materials, which can ensure a high degree of consistency in lattice matching between the two layers, effectively alleviate the interface lattice mismatch stress, reduce the probability of interface mismatch dislocation generation, and thus improve the crystal quality of gallium oxide layer 30.

[0050] In some other embodiments, the starting layer of the second buffer layer 22 and the ending layer of the first buffer layer 21 can be the same Al. x Ga 1-x O layer, and the starting layer of the third buffer layer 23 and the ending layer of the second buffer layer 22 are the same Al. y Ga 1-y O layer.

[0051] In summary, the gallium oxide layer 30 in the gallium oxide epitaxial structure provided in this application embodiment exhibits excellent crystal quality, and its related morphology characterization is as follows: Figure 2 As shown. Compared to the gallium oxide epitaxial structure provided by related technologies (please refer to [reference needed] for details) Figure 3 The gallium oxide epitaxial structure provided in this application has a smooth and dense surface morphology and a lower surface roughness (2.25 nm). Figure 3 The surface roughness of the gallium oxide epitaxial structure shown is 4.12 nm. It can be seen that the gallium oxide layer 30 in the gallium oxide epitaxial structure provided in this application embodiment has a lower surface roughness and a lower dislocation density.

[0052] Based on this, this application also provides a method for preparing a gallium oxide epitaxial structure. Figure 4 This is a schematic flowchart illustrating the method for fabricating gallium oxide epitaxial structures provided in this application embodiment. Please refer to... Figure 4 Methods for preparing gallium oxide epitaxial structures include: Step S01, providing a substrate; Step S02: A buffer layer is formed on the substrate. The buffer layer includes a first buffer layer, a second buffer layer, and a third buffer layer stacked sequentially in a direction away from the substrate. The first buffer layer includes multiple first circulation units, each of which includes a stacked AlN layer and an Al layer. x Ga 1-x Layer O, where 0 < x < 1; the starting layer of the first buffer layer is the AlN layer, and the ending layer of the first buffer layer is Al. x Ga 1-xO layer; the second buffer layer includes multiple second loop units, each of which includes stacked A1 layers. x Ga 1-x O layer and Al y Ga 1-y Layer O, where 0 < y < x; the starting layer of the second buffer layer is Al. x Ga 1-x The O layer, the termination layer of the second buffer layer is Al. y Ga 1-y O layer; the third buffer layer includes multiple third loop units, each of which includes stacked A1 layers. y Ga 1-y O layer and Al z Ga 1-z Layer O, where 0 < z < y; the starting layer of the third buffer layer is Al. y Ga 1-y The O layer, the third buffer layer terminates at Al. z Ga 1-z O layer; Step S03: Form a gallium oxide layer on the buffer layer.

[0053] Below, in conjunction with Figure 1 The preparation method of gallium oxide epitaxial structure provided in the embodiments of this application will be described in detail.

[0054] In step S01, please refer to Figure 1 The substrate 10 can be a silicon (Si) substrate, a sapphire substrate, a silicon carbide (SiC) substrate, an alumina / aluminum nitride composite substrate (Al2O3 / AlN composite substrate), a silicon / aluminum nitride composite substrate (Si / AlN composite substrate), a silicon carbide / aluminum nitride composite substrate (SiC / AlN composite substrate), etc. For example, the substrate 10 is a silicon substrate.

[0055] In some embodiments, after providing the substrate 10, the method for fabricating the gallium oxide epitaxial structure may further include: forming an AlN seed layer 101 on the substrate 10. The thickness of the AlN seed layer 101 may be 5 nm to 50 nm; further, the thickness of the AlN seed layer 101 may be 10 nm to 15 nm.

[0056] Specifically, the AlN seed layer 101 can be formed on the substrate 10 by magnetron sputtering of AlN material using a physical vapor deposition (PVD) device. The magnetron sputtering process parameters are as follows: sputtering temperature is 200℃~800℃, sputtering power is 20W~200W; the sputtering atmosphere includes argon, nitrogen and oxygen, wherein the argon flow rate is 0sccm~200sccm, the nitrogen flow rate is 0sccm~200sccm, and the oxygen flow rate is 0sccm~1sccm; the sputtering time is 10s~100s.

[0057] In step S02, please refer to Figure 1 AlN layer in the buffer layer, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The O layer can be grown layer by layer using metal-organic chemical vapor deposition (MOCVD) technology.

[0058] The growth process parameters for the AlN layer are as follows: growth temperature is 1000℃~1300℃; reaction pressure is 50mbar~100mbar; the reaction gases include ammonia (NH3) and trimethylaluminum (TMAl), wherein the flow rate of NH3 is 0.5slm~2slm and the flow rate of TMAl is 50sccm~300sccm.

[0059] Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The growth process parameters for the O layer are as follows: growth temperature is 1000℃~1300℃; reaction pressure is 50mbar~100mbar; the reaction gases include trimethylaluminum (TMAl), trimethylgallium (TMGa) and oxygen, wherein the flow rate of TMAl is 50sccm~300sccm, the flow rate of TMGa is 50sccm~500sccm, and the flow rate of oxygen is 5L~10L.

[0060] In some embodiments, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The aluminum components (Al components) x, y, and z in the O layer satisfy the following conditions: 0.85≤x≤0.95; 0.75≤y≤0.85; 0.55≤z≤0.75.

[0061] In one specific embodiment, x is 0.9, y is 0.8, and z is 0.6. Based on this, Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer; Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer; Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer.

[0062] In this embodiment, the growth temperature for each aluminum gallium oxide layer is 1000℃, the reaction pressure is 60 mbar, and the oxygen flow rate is 10 L. The flow rate ratio of trimethylaluminum (TMAl) to trimethylgallium (TMG) is selectively controlled according to the Al composition of each aluminum gallium oxide layer: a higher flow rate ratio results in a higher Al composition. Specifically, the growth of Al... 0.6 Ga 0.4 When the O layer is formed, the flow rate of TMGa is 60 sccm, and the flow rate of TMAl is 60 sccm; Al growth 0.8 Ga 0.2 When the O layer is formed, the flow rate of TMGa is 45 sccm, and the flow rate of TMAl is 80 sccm; Al growth 0.9 Ga 0.1 When the O layer is used, the flow rate of TMGa is 40 sccm and the flow rate of TMAl is 90 sccm.

[0063] In some embodiments, the Al component in the AlN layer and Al x Ga 1-x The difference in Al composition in the O layer is d1, Al x Ga 1- x Al components in the O layer and Al y Ga 1-y The difference in Al composition in the O layer is d2, Al y Ga 1-y Al components and Al in the O layer z Ga 1-z The difference in Al composition in the O layer is d3; d1, d2 and d3 are all in the range of 0.1 to 0.2.

[0064] In some embodiments, the AlN layer, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-zThe thickness of the O layer is in the range of 5nm to 15nm.

[0065] In one specific embodiment, Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer, Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer, Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer; AlN layer, Al x Ga 1-x O layer, Al y Ga 1-y O layer and Al z Ga 1-z The thickness of the O layer is 10 nm.

[0066] In some embodiments, the thickness of the buffer layer 20 is 500nm to 800nm. For example, the thickness of the buffer layer 20 is 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, or 800nm.

[0067] In some embodiments, the number of first loop units A1 is 5 to 10, specifically, 5, 6, 7, 8, 9, or 10; the number of second loop units A2 is 5 to 10, specifically, 5, 6, 7, 8, 9, or 10; and the number of third loop units A3 is 10 to 20, specifically, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

[0068] In step S03, please refer to Figure 1 The specific steps for forming the gallium oxide layer 30 may include: using high-purity oxygen (O2) as the oxygen source, trimethylgallium (TMGa) or triethylgallium (TEGa) as the gallium source, high-purity hydrogen (H2) as the annealing atmosphere, and high-purity argon (Ar) as the carrier gas, and employing metal-organic chemical vapor deposition (MOCVD) technology to grow the gallium oxide layer 30 on the buffer layer 20. The thickness of the gallium oxide layer 30 can be 500 nm to 1000 nm. Here, high purity refers to a gas purity ≥ 99.999%.

[0069] The growth process parameters for gallium oxide layer 30 are as follows: growth temperature is 750℃~950℃; reaction pressure is 50mbar~100mbar; gallium source flow rate is 50sccm~500sccm; oxygen source flow rate is 5L / min~10L / min.

[0070] In some specific embodiments, the step of forming the gallium oxide layer 30 further includes: forming a gallium oxide nucleation layer on the buffer layer 20 at a first growth rate, the first growth rate being between 0.6 μm / h and 1.2 μm / h; then, depositing a gallium oxide host layer on the gallium oxide nucleation layer at a second growth rate higher than the initial growth rate, the second growth rate being greater than 1.5 μm / h. The gallium oxide nucleation layer and the gallium oxide host layer constitute the gallium oxide layer 30.

[0071] Understandably, a lower initial growth rate provides sufficient surface migration capability for Ga and O atoms, allowing them to fully relax and effectively release the interfacial mismatch stress caused by the lattice mismatch between the gallium oxide layer 30 and the buffer layer 20, thereby suppressing the proliferation and slippage of mismatched dislocations. This low-speed growth process not only significantly reduces dislocation defects and internal stress within the gallium oxide nucleation layer but also effectively reduces the introduction of unintentional doping impurities, thus lowering the background carrier concentration. Based on this, using a higher second growth rate for thick film deposition effectively suppresses the diffusion of deep-level impurities such as C and Si in the film layer, while significantly improving the deposition efficiency of the gallium oxide layer 30 per unit time. Thus, a synergistic optimization of gallium oxide growth rate and crystal quality can be achieved.

[0072] Based on this, this application also provides a solar-blind ultraviolet detector, which includes the gallium oxide epitaxial structure described in any of the above embodiments or the gallium oxide epitaxial structure prepared by the preparation method of the gallium oxide epitaxial structure described in any of the above embodiments.

[0073] In some embodiments, the solar-blind ultraviolet detector includes a metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetector. The MSM solar-blind ultraviolet photodetector can be fabricated by depositing electrodes (e.g., Ti / Au / Ti / Au composite metal interdigitated electrodes) onto a gallium oxide layer.

[0074] The crystal quality of gallium oxide epitaxial structures directly determines the photoelectric response performance of photodetectors. Specifically, gallium oxide layers with fewer crystal defects and higher surface flatness can effectively reduce carrier recombination losses, improve the migration and collection efficiency of photogenerated carriers, and ultimately optimize the photoelectric detection performance of the device. Therefore, by conducting electrical performance tests on the fabricated devices, the crystal quality of the gallium oxide layer can be further verified.

[0075] Electrical performance testing: The electrical performance of the MSM solar-blind ultraviolet photodetector provided in this application and the MSM solar-blind ultraviolet photodetector based on the existing gallium oxide epitaxial structure (comparative sample) were tested using a 254nm ultraviolet light source. The current measured under the illumination of the light source is the photocurrent, and the current measured under the absence of the light source is the dark current. This application uniformly selects the current value at 5V as the photocurrent evaluation index. Under the same test conditions, the higher the photocurrent value, the better the photoelectric response performance of the device.

[0076] Test results: With a fixed test voltage of 5V, the device was continuously irradiated with a 254nm ultraviolet light source. The photocurrent of the device was recorded at 5s and 15s irradiation time. After 5s irradiation, the photocurrent of the device provided in this application was 50nA, while the photocurrent of the comparison sample was only 20nA. After extending the irradiation time to 15s, the photocurrent of the device provided in this application reached 330nA, while the photocurrent of the comparison sample was only 140nA.

[0077] The comparative results show that the MSM solar-blind ultraviolet detector provided in this application exhibits a significant improvement in photocurrent and stronger photoelectric response capability. It is evident that the gallium oxide layer crystal in the embodiments of this application possesses excellent quality, providing a reliable material basis for the construction of high-performance photodetectors.

[0078] It should be noted that the gallium oxide epitaxial structure embodiments and the gallium oxide epitaxial structure preparation method embodiments provided in this application belong to the same concept; the technical features in the technical solutions described in each embodiment can be arbitrarily combined without conflict.

[0079] It should be understood that the above embodiments are exemplary and not intended to encompass all possible implementations. Various modifications and changes can be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of this application that may not be explicitly described. Therefore, the above embodiments only illustrate several implementations of this application and do not limit the scope of protection of this patent application.

Claims

1. A gallium oxide epitaxial structure, characterized in that, The gallium oxide epitaxial structure includes a substrate, an AlN seed layer, a buffer layer, and a gallium oxide layer stacked sequentially. Along the direction away from the substrate, the buffer layer includes a first buffer layer, a second buffer layer and a third buffer layer stacked sequentially. The first buffer layer includes multiple first loop units, each of which includes a stacked AlN layer and an Al layer. x Ga 1-x Layer O, where 0 < x < 1; the starting layer of the first buffer layer is the AlN layer, and the ending layer of the first buffer layer is the Al layer. x Ga 1-x O layer; the AlN layer, which serves as the starting layer, is directionally grown using the AlN seed layer as a lattice template; The second buffer layer includes a plurality of second loop units, each of which includes the stacked A1. x Ga 1-x O layer and Al y Ga 1-y Layer O, where 0 < y < x; the starting layer of the second buffer layer is the Al. x Ga 1-x Layer O, the termination layer of the second buffer layer is the Al. y Ga 1-y O layer; The third buffer layer includes multiple third loop units, each of which includes stacked A1 units. y Ga 1-y O layer and Al z Ga 1-z Layer O, and 0 < z < y; the starting layer of the third buffer layer is the Al. y Ga 1-y Layer O, the termination layer of the third buffer layer is the Al layer. z Ga 1-z O layer; The Al component in the AlN layer and the Al x Ga 1-x The difference in the Al components in the O layer is d1, where Al x Ga 1-x The Al component in the O layer and the Al y Ga 1-y The difference in the Al components in the O layer is d2, where Al y Ga 1-y The Al component in the O layer and the Al z Ga 1-z The difference in Al composition in the O layer is d3; d1, d2 and d3 are all in the range of 0.1 to 0.

2.

2. The gallium oxide epitaxial structure according to claim 1, characterized in that, The Al x Ga 1-x In layer O, 0.85 ≤ x ≤ 0.95; the Al y Ga 1-y In layer O, 0.75 ≤ y ≤ 0.85; the Al z Ga 1-z In layer O, 0.55≤z≤0.

75.

3. The gallium oxide epitaxial structure according to claim 2, characterized in that, The Al x Ga 1-x O layer is Al 0.9 Ga 0.1 O layer; the Al y Ga 1-y O layer is Al 0.8 Ga 0.2 O layer; the Al z Ga 1-z O layer is Al 0.6 Ga 0.4 O layer.

4. The gallium oxide epitaxial structure according to claim 2, characterized in that, The AlN layer, the Al x Ga 1-x O layer, the Al y Ga 1-y O layer and the Al z Ga 1-z The thickness of the O layer is in the range of 5nm to 15nm.

5. The gallium oxide epitaxial structure according to claim 1, characterized in that, The thickness of the buffer layer is 500nm~800nm.

6. The gallium oxide epitaxial structure according to claim 1, characterized in that, The number of the first loop unit is 5 to 10; the number of the second loop unit is 5 to 10; and the number of the third loop unit is 10 to 20.

7. A method for preparing a gallium oxide epitaxial structure, characterized in that, The method includes: Provide substrate; An AlN seed layer and a buffer layer are sequentially formed on the substrate. The buffer layer comprises a first buffer layer, a second buffer layer, and a third buffer layer sequentially stacked along a direction away from the substrate. The first buffer layer includes multiple first loop units, each of which includes a stacked AlN layer and an Al layer. x Ga 1-x Layer O, where 0 < x < 1; the starting layer of the first buffer layer is the AlN layer, and the ending layer of the first buffer layer is the Al layer. x Ga 1-x O layer; the AlN layer, which serves as the starting layer, is directionally grown using the AlN seed layer as a lattice template; The second buffer layer includes a plurality of second loop units, each of which includes the stacked A1. x Ga 1-x O layer and Al y Ga 1-y Layer O, where 0 < y < x; the starting layer of the second buffer layer is the Al. x Ga 1-x Layer O, the termination layer of the second buffer layer is the Al. y Ga 1-y O layer; The third buffer layer includes multiple third loop units, each of which includes stacked A1 units. y Ga 1-y O layer and Al z Ga 1-z Layer O, and 0 < z < y; the starting layer of the third buffer layer is the Al. y Ga 1-y Layer O, the termination layer of the third buffer layer is the Al layer. z Ga 1-z O layer; The Al component in the AlN layer and the Al x Ga 1-x The difference in the Al components in the O layer is d1, where Al x Ga 1-x The Al component in the O layer and the Al y Ga 1-y The difference in the Al components in the O layer is d2, where Al y Ga 1-y The Al component in the O layer and the Al z Ga 1-z The difference in Al composition in the O layer is d3; d1, d2, and d3 are all in the range of 0.1 to 0.

2. A gallium oxide layer is formed on the buffer layer.

8. The method for preparing a gallium oxide epitaxial structure according to claim 7, characterized in that, The step of forming a buffer layer on the substrate satisfies at least one of the following characteristics: (1) The Al x Ga 1-x In layer O, 0.85 ≤ x ≤ 0.95; the Al y Ga 1-y In layer O, 0.75 ≤ y ≤ 0.85; the Al z Ga 1-z In layer O, 0.55 ≤ z ≤ 0.75; (2) The AlN layer, the Al x Ga 1-x O layer, the Al y Ga 1-y O layer and the Al z Ga 1-z The thickness of the O layer is in the range of 5nm to 15nm; (3) The thickness of the buffer layer is 500nm~800nm; (4) The number of the first loop unit is 5 to 10; the number of the second loop unit is 5 to 10; and the number of the third loop unit is 10 to 20.

9. A solar-blind ultraviolet detector, characterized in that, The solar-blind ultraviolet detector includes a gallium oxide epitaxial structure as described in any one of claims 1 to 6, or a gallium oxide epitaxial structure prepared by a method including the gallium oxide epitaxial structure as described in claim 7 or 8.

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