Method of manufacturing graphite base and light emitting diode
By designing non-circular openings and inner wall protrusions on the graphite substrate, the problem of wavelength yield loss caused by the large contact area between the substrate and the graphite substrate was solved, thus improving the wavelength yield of the epitaxial wafer.
Patent Information
- Application Number
- CN202211429463.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-15
- Publication Date
- 2026-01-20
- Estimated Expiration
- 2042-11-15
AI Technical Summary
In the prior art, the circular opening of the graphite substrate results in a large contact area between the substrate and the inner wall of the graphite substrate, leading to a significant loss in the wavelength yield of the epitaxial structure and affecting the overall wavelength yield.
The design employs a non-circular opening, such as an elliptical, polygonal, or rectangular opening, and provides protrusions on the inner wall of the opening to reduce the contact area between the substrate and the graphite base, replacing surface contact with point contact or partial side contact.
This effectively reduces the contact area between the substrate and the graphite base, improves the wavelength yield of the epitaxial wafer, and mitigates the problem of wavelength being affected by heat in the epitaxial structure.
Smart Images
Figure CN116005256B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of epitaxial growth technology, and in particular to a method for fabricating a graphite substrate and a light-emitting diode. Background Technology
[0002] The graphite substrate is part of a metal-organic chemical vapor deposition (MOCVD) apparatus, and it is typically located within the reaction chamber of the MOCVD apparatus. The graphite substrate is usually cylindrical, with multiple openings evenly distributed along its circumference on one end face. The other end face of the graphite substrate is connected to the drive structure of the MOCVD apparatus.
[0003] Before fabricating a light-emitting diode (LED), a substrate needs to be placed inside the opening of a graphite substrate. Because the reaction chamber rotates at high speed during growth, the edge region of the substrate will come into contact with the inner wall of the opening. Due to the high temperature of the graphite substrate, and the direct contact between the epitaxial structure grown on the substrate and the inner wall of the graphite substrate, the wavelength of the region where the epitaxial structure is in direct contact with the inner wall of the graphite substrate will be shorter than the wavelength of the non-contact region. This results in a significant loss in the wavelength yield of the fabricated epitaxial wafer, affecting the overall wavelength yield of the wafer. Summary of the Invention
[0004] This disclosure provides a method for fabricating a graphite substrate and a light-emitting diode (LED), which can improve the wavelength yield of epitaxial wafers grown in the graphite substrate. The technical solution is as follows:
[0005] This disclosure provides a graphite base with an opening on its surface, the opening being non-circular.
[0006] In one implementation of this disclosure, the opening is elliptical.
[0007] In another implementation of the present disclosure, the major axis of the opening is 120mm to 150mm, and the minor axis of the opening is 80mm to 100mm.
[0008] In another implementation provided in this disclosure, the opening is a polygon.
[0009] In another implementation of the present disclosure, the opening is rectangular, the length of the opening is 110mm to 130mm, and the width of the opening is 110mm to 130mm.
[0010] In another implementation of the present disclosure, the inner wall of the opening has a protrusion that protrudes toward the center of the opening.
[0011] In another implementation of the present disclosure, the protrusion is located on the inner wall of the opening on the side away from the geometric center of the graphite base.
[0012] In another implementation of the present disclosure, the protrusion is conical, with the tip of the protrusion facing the center of the opening.
[0013] In another implementation of the embodiments of this disclosure, the number of protrusions is 2 to 15.
[0014] This disclosure provides a method for fabricating a light-emitting diode (LED). The method is implemented using a graphite substrate as described above, and includes: placing a substrate in an opening of the graphite substrate; and growing an epitaxial layer on the substrate to obtain the LED.
[0015] The beneficial effects of the technical solutions provided in this disclosure include at least the following:
[0016] This disclosure provides a graphite substrate with an opening on its surface, which is non-circular. Compared to related technologies where the opening is set to a circular shape to match the substrate, setting the opening to a non-circular shape significantly reduces the ratio of the contact area between the substrate and the inner wall of the opening to the outline of the inner wall of the opening. This reduces the contact area between the substrate and the graphite substrate, thereby mitigating the problem of wavelength being affected by heat in the epitaxial structure and improving the wavelength yield of the epitaxial wafer. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a structural schematic diagram of a graphite base provided by related technologies;
[0019] Figure 2 This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure;
[0020] Figure 3 This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure;
[0021] Figure 4 This is a schematic diagram of the opening structure of a graphite base provided in an embodiment of this disclosure;
[0022] Figure 5 This is a schematic diagram of the opening structure of a graphite base provided in an embodiment of this disclosure;
[0023] Figure 6 This is a schematic diagram of the opening structure of a graphite base provided in an embodiment of this disclosure;
[0024] Figure 7 This is a schematic diagram of the opening structure of a graphite base provided in an embodiment of this disclosure;
[0025] Figure 8 This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure;
[0026] Figure 9 This is a flowchart of a method for fabricating a light-emitting diode provided in an embodiment of this disclosure;
[0027] Figure 10 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure.
[0028] The markings in the diagram are explained as follows:
[0029] 10. Opening;
[0030] 20. Rounded corners;
[0031] 30. Protrusion;
[0032] 41. Substrate; 42. GaN buffer layer; 43. Undoped GaN layer; 44. n-type GaN layer; 45. Light-emitting layer; 46. AlGaN electron blocking layer; 47. p-type GaN layer; 48. p-type contact layer. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.
[0034] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.
[0035] The manufacturing process of GaN-based light-emitting diodes (LEDs) in related technologies mainly consists of two parts: epitaxial growth and chip fabrication. In the epitaxial growth step, a sapphire substrate is typically used as the substrate for the epitaxial growth of GaN material. The cleaned sapphire substrate is placed into the corresponding opening in the graphite base of the MOCVD equipment and rotated at an appropriate angle. Subsequently, epitaxial growth occurs in the high-temperature, high-pressure environment of the MOCVD reaction chamber, with the participation of various precursor reactants, ultimately growing an epitaxial structure on the substrate.
[0036] During the growth of the epitaxial structure, the graphite substrate inside the MOCVD reaction chamber rotates at high speed. Under the action of centrifugal force, the sapphire substrate on which the epitaxial layer is grown is thrown toward the edge of the opening.
[0037] Figure 1 This is a structural schematic diagram of a graphite base provided by related technologies. For example... Figure 1 As shown in the related technology, the opening 10 of the graphite substrate is often circular in shape to match the sapphire substrate 41. After the sapphire substrate 41 is thrown to contact the inner wall of the opening 10 under centrifugal force, the sapphire substrate 41 usually contacts at least 1 / 2 of the inner wall of the opening 10. However, the graphite substrate has a high temperature, and the wavelength of the region where the epitaxial structure grown on the sapphire substrate is in direct contact with the inner wall of the graphite substrate will be shorter than the wavelength of the non-contact region. This results in a significant loss in the wavelength yield of the prepared epitaxial wafer, affecting the overall wavelength yield of the wafer.
[0038] Therefore, this disclosure provides a graphite base. Figure 2 This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure. Figure 2As shown, the surface of the graphite base has an opening 10, which is non-circular.
[0039] This embodiment of the disclosure provides a graphite substrate with an opening 10 on its surface, the opening 10 being non-circular. Compared to related technologies where the opening 10 is set to a circular shape matching the substrate 41, setting the opening to a non-circular shape ensures that the portion of the inner wall of the opening 10 that contacts the substrate 41 does not exceed 1 / 3 of the inner wall's outline. This effectively reduces the contact area between the substrate 41 and the graphite substrate, thereby mitigating the problem of wavelength being affected by heat in the epitaxial structure and improving the wavelength yield of the epitaxial wafer.
[0040] In some implementations disclosed herein, such as Figure 2 As shown, the opening 10 is elliptical in shape. By setting the shape of the opening 10 to elliptical, the outer contour of the circular substrate does not fit the inner wall of the elliptical opening 10. Thus, when the substrate is thrown to the edge of the opening 10 by centrifugal force, only a portion of the substrate's outer contour is in direct contact with the inner wall of the opening 10. See also... Figure 2 The original contact method, in which the entire side was tightly attached, was changed to a contact method that only involves two sides. This significantly reduces the contact area between the substrate and the graphite base, weakens the problem of wavelength being affected by heat in the epitaxial structure, and improves the wavelength yield of the epitaxial wafer.
[0041] Optionally, such as Figure 2 As shown, the major axis a of opening 10 is 120mm to 150mm, and the minor axis b of opening 10 is 80mm to 100mm.
[0042] By setting the major and minor axes of the opening 10 within the aforementioned range, the size of the opening 10 is prevented from being too small, which would cause the substrate to be stuck in it; and the size of the opening 10 is also prevented from being too large, which would occupy too much space and reduce the total number of openings 10 on the graphite base.
[0043] For example, the major axis of the opening 10 is 130 mm and the minor axis of the opening 10 is 90 mm.
[0044] In some other implementations, the opening 10 is polygonal in shape.
[0045] Figure 3 This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure. Figure 3 As shown, the opening 10 is rectangular. By setting the shape of the opening 10 to rectangular, the outer contour of the circular substrate does not fit the inner wall of the rectangular opening 10. Thus, when the substrate is thrown to the edge of the opening 10 by centrifugal force, only a portion of the substrate's outer contour is in direct contact with the inner wall of the opening 10. See also... Figure 2The original contact method, in which the entire side was tightly attached, was changed to a contact method that only involves two sides. This significantly reduces the contact area between the substrate and the graphite base, weakens the problem of wavelength being affected by heat in the epitaxial structure, and improves the wavelength yield of the epitaxial wafer.
[0046] Optionally, the length c of the opening 10 is 110mm to 130mm, and the width d of the opening 10 is 110mm to 130mm.
[0047] By setting the length and width of the opening 10 within the above range, the design of the opening 10 is avoided from being too small, which would cause the substrate to get stuck in it; and the design of the opening 10 is also avoided from being too large, which would take up too much space, thus reducing the total number of openings 10 on the graphite base.
[0048] For example, the length of the opening 10 is 120 mm and the width of the opening 10 is 120 mm. That is, the opening 10 is square. Compared with a rectangle, the square opening 10 occupies less space after accommodating the substrate, which is beneficial for setting more openings 10 on the graphite base.
[0049] Figure 4 This is a schematic diagram of the opening structure of a graphite base provided in an embodiment of this disclosure. For example... Figure 4 As shown, at least part of the opening 10 has a rounded corner 20 between adjacent two sides.
[0050] In this embodiment of the disclosure, the opening 10 is rectangular in shape, and each of the four sides has a rounded corner 20 between any two adjacent sides, that is, the four corners of the opening 10 are all rounded corners 20.
[0051] By setting the corners of the polygons to rounded corners 20, the multiple openings 10 can be more densely distributed on the graphite substrate, allowing for more openings 10 to be set on the graphite substrate and improving the fabrication success rate of light-emitting diodes. Furthermore, setting the corners of the openings 10 to rounded corners 20 reduces the risk of damage, thus improving the reliability of the openings 10.
[0052] It should be noted that the opening 10 can be a rectangle, or it can be a triangle, pentagon, hexagon, or other shapes. In other polygons, rounded corners 20 can also be provided between two adjacent sides. This disclosure does not impose any restrictions.
[0053] Optionally, the inner wall of the opening 10 has a protrusion 30 that protrudes towards the center of the opening 10. By providing the protrusion 30 on the inner wall of the opening 10, the contact method between the substrate and the inner wall of the opening 10 is changed from surface contact and side contact to point contact, thereby significantly reducing the contact area between the substrate and the graphite substrate, mitigating the problem of wavelength being affected by heat in the epitaxial structure, and improving the wavelength yield of the epitaxial wafer.
[0054] In some implementations, the protrusion 30 can be set in a regular closed shape, which can be a polygon, an ellipse, a circle, or other shapes.
[0055] Figure 5 This is a schematic diagram of the opening 10 of a graphite base provided in an embodiment of this disclosure. Figure 5 As shown, protrusions 30 are provided on the sides of the rectangle, with one protrusion 30 on each side. This changes the contact method between the substrate and the inner wall of the opening 10 from side contact to point contact, thereby significantly reducing the contact area between the substrate and the graphite substrate, mitigating the problem of wavelength being affected by heat in the epitaxial structure, and improving the wavelength yield of the epitaxial wafer.
[0056] Figure 6 This is a schematic diagram of the opening 10 of a graphite base provided in an embodiment of this disclosure. Figure 6 As shown, protrusions 30 are disposed on the inner wall of the circular opening 10, and the inner wall of the circular opening 10 has multiple protrusions 30 spaced apart. This changes the contact method between the substrate and the inner wall of the opening 10 from surface contact to point contact, thereby significantly reducing the contact area between the substrate and the graphite substrate, mitigating the problem of wavelength being affected by heat in the epitaxial structure, and improving the wavelength yield of the epitaxial wafer.
[0057] In some implementations, the protrusion 30 can be set in an irregular closed shape, which can be a shape formed by connecting curves.
[0058] Figure 7 This is a schematic diagram of the opening 10 of a graphite base provided in an embodiment of this disclosure. Figure 7 As shown, the protrusions 30 are arranged on the pattern formed by connecting curves, and the inner wall of the opening 10 has multiple protrusions 30 spaced apart. This adjusts the contact method between the substrate and the inner wall of the opening 10 to point contact, which can significantly reduce the contact area between the substrate and the graphite base and mitigate the problem of wavelength being affected by heat in the epitaxial structure.
[0059] For example, such as Figure 7 As shown, the protrusion 30 on the curve-connected pattern can be conical, with the tip of the protrusion 30 pointing towards the center of the opening 10. This makes the outline of the opening 10 wavy. This irregular pattern reduces the contact area between the substrate and the opening 10, effectively mitigating the problem of wavelength being affected by heat in the epitaxial structure.
[0060] It should be noted that in some other implementations, the shape of the protrusion 30 can be an arc, a polygon, or other shapes, and this disclosure does not impose any restrictions.
[0061] Figure 8This is a schematic diagram of the structure of a graphite base provided in an embodiment of this disclosure. Figure 8 As shown, protrusion 30 is located on the inner wall of opening 10 on the side away from the geometric center of the graphite base.
[0062] Because the graphite substrate rotates at high speed during operation, the substrate is typically thrown to the side of the opening 10 away from the geometric center of the graphite substrate under centrifugal force. Therefore, by simply placing the protrusion 30 on the inner wall of the opening 10 away from the geometric center of the graphite substrate, the contact between the substrate and the inner wall of the opening 10 can be adjusted to point contact, significantly reducing the contact area between the substrate and the graphite substrate and mitigating the problem of wavelength interference caused by heat in the epitaxial structure. Furthermore, since the protrusion 30 is only placed in a portion of the inner wall of the opening 10, the processing difficulty of the opening 10 can be reduced, facilitating its fabrication.
[0063] Optionally, the number of protrusions can be 2 to 15. For example, such as... Figure 6 As shown, six protrusions are provided inside the opening. The number of protrusions is controlled within the above range to avoid the problem of having too few protrusions, which would fail to reduce the contact area between the substrate and the graphite base.
[0064] Figure 9 This is a flowchart illustrating a method for fabricating a light-emitting diode (LED) according to an embodiment of this disclosure. Figure 9 As shown, the method for fabricating this light-emitting diode includes:
[0065] S11: Provide a graphite base.
[0066] The graphite base has an opening on its surface, and the portion of the inner wall of the opening that is in contact with the substrate does not exceed 1 / 3 of the inner wall of the opening.
[0067] Optionally, such as Figure 2 As shown, the opening is elliptical in shape.
[0068] In this way, when the substrate is thrown to the edge of the opening by centrifugal force, only a portion of the substrate's outer contour is in direct contact with the inner wall of the opening. The original contact method, in which part of the side surfaces were in close contact, has been changed to a contact method that only involves two sides, significantly reducing the contact area between the substrate and the graphite substrate.
[0069] For example, the major axis of the opening is 120mm to 150mm, and the minor axis of the opening is 80mm to 100mm.
[0070] For example, the major axis of the opening is 130mm, and the minor axis of the opening is 90mm.
[0071] Optionally, such as Figure 3 As shown, the opening is rectangular in shape.
[0072] By setting the shape of the opening to a rectangle, the original contact method where the entire side was in close contact was changed to a contact method where only two sides were in contact, which greatly reduced the contact area between the substrate and the graphite base.
[0073] For example, the length of the opening is 110mm to 130mm and the width of the opening is 110mm to 130mm.
[0074] For example, the length of the opening is 120mm and the width of the opening is 120mm.
[0075] Optionally, the inner wall of the opening has a protrusion that protrudes toward the center of the opening.
[0076] For example, such as Figure 6 As shown, the protrusions are arranged on a graphic formed by connecting curves, and the inner wall of the opening has multiple protrusions distributed at intervals.
[0077] The protrusions on the curve-connected pattern can be conical, with their tips pointing towards the center of the opening. This creates a wavy outline of the opening. This irregular pattern reduces the contact area between the substrate and the opening, effectively mitigating the problem of wavelength being affected by heat in the epitaxial structure.
[0078] Alternatively, the protrusion is located on the inner wall of the opening on the side away from the geometric center of the graphite base.
[0079] By setting a protrusion only on the inner wall of the opening on the side away from the geometric center of the graphite base, the processing difficulty of the opening can be reduced, making it easier to manufacture.
[0080] S12: Place the substrate in the opening of the graphite base.
[0081] Optionally, the substrate may be a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate may be a flat substrate or a patterned substrate.
[0082] As an example, in this embodiment of the disclosure, the substrate is a sapphire substrate. Sapphire substrates are a commonly used substrate, with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a flat sapphire substrate.
[0083] In step S22, the sapphire substrate can be pretreated by placing it in the MOCVD reaction chamber and baking it for 12 to 18 minutes. As an example, in this embodiment of the present disclosure, the sapphire substrate is baked for 15 minutes.
[0084] Specifically, the baking temperature can be from 1000℃ to 1200℃, and the pressure inside the MOCVD reaction chamber during baking can be from 100mbar to 200mbar.
[0085] S13: An epitaxial layer is grown on the substrate to obtain a light-emitting diode.
[0086] In this embodiment of the disclosure, the process of growing the epitaxial layer may include the following steps:
[0087] Step 1: Grow a GaN buffer layer on the substrate.
[0088] For example, the growth temperature of the GaN buffer layer can be from 530°C to 560°C. The growth temperature affects the grown GaN film, and a GaN buffer layer of good quality can be grown within this temperature range.
[0089] As an example, in this embodiment of the disclosure, the growth temperature of the GaN buffer layer can be 550°C.
[0090] For example, the growth pressure of the GaN buffer layer can be from 200 mtorr to 500 mtorr. The growth pressure affects the grown GaN film, and a GaN buffer layer of good quality can be grown within this pressure range.
[0091] As an example, in this embodiment of the disclosure, the growth pressure of the GaN buffer layer can be 300 mtorr.
[0092] Step 2: Grow an undoped GaN layer on the GaN buffer layer.
[0093] The thickness of the undoped GaN layer can be from 0.5 μm to 3 μm.
[0094] For example, the growth temperature of the undoped GaN layer can be 1000°C to 1100°C, and the growth pressure can be controlled between 100 torr and 300 torr.
[0095] Step 3: Grow an n-type layer on the undoped GaN layer.
[0096] Optionally, the n-type layer is an n-type GaN layer, the growth temperature of the n-type GaN layer can be from 1000℃ to 1100℃, and the growth pressure of the n-type GaN layer can be from 100 torr to 300 torr.
[0097] Optionally, the thickness of the n-type GaN layer can be from 0.5 μm to 3 μm.
[0098] Step 4: Grow a light-emitting layer on the n-type layer.
[0099] The light-emitting layer may include alternating InGaN well layers and GaN barrier layers. The reaction chamber pressure is controlled at 200 torr. The reaction chamber temperature is 760°C to 780°C during InGaN well layer growth and 860°C to 890°C during GaN barrier layer growth. This process condition produces a high-quality light-emitting layer.
[0100] Step 5: Grow an AlGaN electron blocking layer on the light-emitting layer.
[0101] The growth temperature of the AlGaN electron blocking layer can be from 800℃ to 1000℃, and the growth pressure can be from 100 Torr to 300 Torr. AlGaN electron blocking layers grown under these conditions are of good quality, which is beneficial for improving the luminous efficiency of light-emitting diodes.
[0102] Step 6: Grow a p-type layer on the AlGaN electron blocking layer.
[0103] Optionally, the p-type layer is a p-type GaN layer, the growth pressure of the p-type GaN layer can be from 200 Torr to 600 Torr, and the growth temperature of the p-type GaN layer can be from 800℃ to 1000℃.
[0104] Step 7: Grow a p-type contact layer on the p-type GaN layer.
[0105] Optionally, the growth pressure of the p-type contact layer can be from 100 Torr to 300 Torr, and the growth temperature of the p-type contact layer can be from 800°C to 1000°C.
[0106] It should be noted that, in the embodiments of this disclosure, an MOCVD device is used to realize the growth method of light-emitting diodes. High-purity H2, high-purity N2, or a mixture of high-purity H2 and high-purity N2 are used as carrier gases, high-purity NH3 as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) as gallium sources, trimethylindium (TMIn) as the indium source, silane (SiH4) as the N-type dopant, trimethylaluminum (TMAl) as the aluminum source, and magnesium pyrocene (CP2Mg) as the P-type dopant.
[0107] Figure 10 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure. For example... Figure 10 As shown, the light-emitting diode epitaxial wafer may include a substrate 41 and GaN buffer layer 42, undoped GaN layer 43, n-type GaN layer 44, light-emitting layer 45, AlGaN electron blocking layer 46, p-type GaN layer 47 and p-type contact layer 48 grown on the substrate 41.
[0108] It should be noted that, Figure 10The light-emitting diodes shown are for illustrative purposes only. In other implementations provided in this disclosure, the epitaxial tray can also be used to grow other types of light-emitting diodes or different semiconductor epitaxial wafers. This disclosure does not limit this.
[0109] The above is not intended to limit this disclosure in any way. Although this disclosure has been disclosed above through embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this disclosure. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this disclosure without departing from the content of the technical solution of this disclosure shall still fall within the scope of the technical solution of this disclosure.
Claims
1. A graphite base, characterized in that, The surface of the graphite base has an opening (10), which is non-circular. The inner wall of the opening (10) does not match the outer contour of the substrate. The length of the portion of the inner wall of the opening (10) that contacts the substrate (41) is less than or equal to 1 / 3 of the inner wall of the opening (10).
2. The graphite base according to claim 1, characterized in that, The opening (10) is elliptical.
3. The graphite base according to claim 2, characterized in that, The major axis of the opening (10) is 120mm to 150mm, and the minor axis of the opening (10) is 80mm to 100mm.
4. The graphite base according to claim 1, characterized in that, The opening (10) is polygonal.
5. The graphite base according to claim 4, characterized in that, The opening (10) is rectangular, with a length of 110mm to 130mm and a width of 110mm to 130mm.
6. The graphite base according to any one of claims 1 to 5, characterized in that, The inner wall of the opening (10) has a protrusion (30) that protrudes toward the center of the opening (10).
7. The graphite base according to claim 6, characterized in that, The protrusion (30) is located on the inner wall of the opening (10) on the side away from the geometric center of the graphite base.
8. The graphite base according to claim 6, characterized in that, The protrusion (30) is conical, with the tip of the protrusion (30) facing the center of the opening (10).
9. The graphite base according to claim 6, characterized in that, The number of protrusions (30) is 2 to 15.
10. A method for fabricating a light-emitting diode, characterized in that, The preparation method is implemented using the graphite substrate as described in any one of claims 1 to 9, comprising: A substrate is placed in the opening of the graphite base; An epitaxial layer is grown on the substrate to obtain a light-emitting diode.