A vertical structure LED and its manufacturing method

Abstract

The present invention relates to the field of semiconductor technology, and specifically discloses a vertical structure LED and a preparation method thereof. Among them, the vertical structure LED includes a light-emitting body and a conductive body arranged up and down; the light-emitting body includes a first insulating layer, an N-GaN layer, an MQWs layer, an EBL layer, a P-GaN layer, a reflective metal layer, a protective metal layer and a second insulating layer which are connected layer by layer from top to bottom; one side of the bottom surface of the light-emitting body has a first groove penetrating through to the N-GaN layer, and the first groove is filled with an N electrode layer based on the inner surface covering the second insulating layer, and the second insulating layer has a second groove at the other side of the bottom surface of the light-emitting body; the conductive body includes a conductive substrate and a P electrode layer; the conductive substrate partially covers the second insulating layer through a metal bonding layer and is connected to the N electrode layer, and the P electrode layer is arranged in the second groove and connected to the protective metal layer; this vertical structure LED can be flip-chip bonded and packaged, and can improve the reliability, stability and light-emitting efficiency of the LED device.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular, to a vertical structure LED and a preparation method thereof. Background Art

[0002] The structure of an LED mainly includes a horizontal structure and a vertical structure. Compared with the horizontal structure, the vertical structure has the advantages of fast heat dissipation, uniform current diffusion, high luminous efficiency, large light-emitting area, etc.

[0003] However, the existing vertical structure LEDs generally have an upper N electrode, and the N electrode will cover a part of the light-emitting surface, causing light blocking, thereby reducing the light-emitting area and affecting the luminous efficiency. In addition, the existing vertical structure LEDs generally need to be connected by gold wires during the packaging process, and it is easy to cause system instability due to the breakage of the gold wires, resulting in insufficient reliability.

[0004] In view of the above problems, there is currently no effective technical solution. Summary of the Invention

[0005] The purpose of the present application is to provide a vertical structure LED to improve the luminous efficiency and reliability of the vertical structure LED.

[0006] In a first aspect, the present application provides a vertical structure LED, which includes a light-emitting body and a conductive body arranged up and down;

[0007] The light-emitting body includes a first insulating layer, an N-GaN layer, an MQWs layer, an EBL layer, a P-GaN layer, a reflective metal layer, a protective metal layer, and a second insulating layer connected layer by layer from top to bottom;

[0008] On one side of the bottom surface of the light-emitting body, there is a first groove penetrating to the N-GaN layer. The first groove is filled with an N electrode layer based on the inner surface covering the second insulating layer, and there is a second groove at the other side of the bottom surface of the light-emitting body where the second insulating layer is located;

[0009] The conductive body includes a conductive substrate and a P electrode layer;

[0010] The conductive substrate partially covers the second insulating layer through a metal bonding layer and is connected to the N electrode layer, and the P electrode layer is arranged in the second groove and connected to the protective metal layer.

[0011] The vertical - structure LED of the present application can be flip - chip bonded and packaged based on a conductive substrate and a P - electrode layer, which can effectively reduce the problem of gold - wire breakage, thereby improving the reliability and stability of the LED device. Moreover, the N - electrode layer is led out based on a conductive substrate partially covered by a second insulating layer, which can effectively reduce the light - blocking effect of the N - electrode and the light - absorption effect of the silicon substrate, effectively improving the light - emitting efficiency of the vertical LED structure and further increasing the light - output power.

[0012] For the described vertical - structure LED, the bottom surface of the P - electrode layer is flush with the bottom surface of the conductive substrate.

[0013] The vertical - structure LED of the present application is suitable for flip - chip bonding. The bottom surface of the P - electrode layer is designed to be flush with the bottom surface of the conductive substrate, which can ensure the stability and balance during the bonding and packaging of the vertical - structure LED of the present application, so as to ensure that the light - emitting surface of the vertical - structure LED is parallel to the bonding surface and emits light outward in a direction perpendicular to the bonding surface.

[0014] For the described vertical - structure LED, the depth of the first groove in the N - GaN layer is 1 / 4 - 1 / 2 of the thickness of the N - GaN layer.

[0015] In this example, designing the depth of the first groove in the N - GaN layer to be 1 / 4 - 1 / 2 of the thickness of the N - GaN layer can expand the ohmic - contact area between the N - electrode layer and the N - GaN layer and effectively avoid the light - blocking of the N - electrode layer.

[0016] For the described vertical - structure LED, the width of the conductive substrate is less than 1 / 2 of the width of the second insulating layer on the protective metal layer.

[0017] For the described vertical - structure LED, the P - electrode layer completely covers the second groove.

[0018] For the described vertical - structure LED, the metal - bonding layer is prepared from any two or more of nickel, gold, tin, and titanium.

[0019] For the described vertical - structure LED, the reflective metal layer is prepared from silver or aluminum.

[0020] For the described vertical - structure LED, the protective metal layer is prepared from titanium, TiW, or nickel.

[0021] For the described vertical - structure LED, both the N - electrode layer and the P - electrode layer are prepared from any two or more of titanium, chromium, silver, and gold.

[0022] In a second aspect, the present application also provides a method for manufacturing a vertical - structure LED. The method includes the steps:

[0023] S1. Set a substrate, and sequentially prepare a buffer layer, an N-GaN layer, an MQWs layer, an EBL layer, a P-GaN layer, a reflective metal layer, and a protective metal layer on the substrate to obtain a light-emitting body;

[0024] S2. Set a first groove on the light-emitting body that penetrates through to the N-GaN layer;

[0025] S3. Deposit a second insulating layer on the protective metal layer and the inner surface of the first groove, and prepare an N electrode layer in the first groove;

[0026] S4. Deposit a metal bonding layer on the light-emitting body and bond a conductive substrate;

[0027] S5. Selectively strip the metal bonding layer and the conductive substrate so that part of the second insulating layer is exposed, and remove part of the exposed second insulating layer to form a second groove;

[0028] S6. Prepare a P electrode layer on the second groove that is connected to the protective metal layer;

[0029] S7. Remove the substrate and the buffer layer to expose the N-GaN layer, and grow a first insulating layer on the N-GaN layer.

[0030] The method for preparing a vertical structure LED of the present application can conveniently and orderly fabricate the vertical structure LED provided in the first aspect.

[0031] As can be seen from the above, the present application provides a vertical structure LED and a preparation method thereof. Among them, the vertical structure LED can be flip-chip bonded and packaged based on a conductive substrate and a P electrode layer, which can effectively reduce the problem of gold wire breakage, thereby improving the reliability and stability of the LED device. Moreover, the N electrode layer is led out based on a conductive substrate that partially covers the second insulating layer, which can effectively reduce the light blocking of the N electrode and the light absorption of the silicon substrate, effectively improving the light emission efficiency of the vertical LED structure, and further improving the light output power. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of a vertical structure LED provided by an embodiment of the present application.

[0033] Figure 2 It is a flowchart of a method for preparing a vertical structure LED provided by an embodiment of the present application.

[0034] Figure 3 It is a schematic diagram of the process of preparing a vertical structure LED by the method for preparing a vertical structure LED provided by an embodiment of the present application.

[0035] Reference numerals: 1, first insulating layer; 2, N-GaN layer; 3, MQWs layer; 4, EBL layer; 5, P-GaN layer; 6, reflective metal layer; 7, protective metal layer; 8, second insulating layer; 9, N electrode layer; 10, P electrode layer; 11, metal bonding layer; 12, conductive substrate; 13, substrate; 14, buffer layer. Detailed implementation manners

[0036] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection, an electrical connection or a communication with each other; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0040] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0041] In a first aspect, please refer to Figure 1 , some embodiments of the present application provide a vertical structure LED, characterized in that the vertical structure LED includes a light-emitting body and a conductive body arranged up and down;

[0042] The light-emitting body includes a first insulating layer 1, an N-GaN layer 2, an MQWs layer 3, an EBL layer 4, a P-GaN layer 5, a reflective metal layer 6, a protective metal layer 7 and a second insulating layer 8 that are sequentially connected layer by layer from top to bottom;

[0043] On one side of the bottom surface of the light-emitting body, there is a first groove that penetrates to the N-GaN layer 2. The first groove is filled with an N electrode layer 9 based on the inner surface covering the second insulating layer 8. The second insulating layer 8 has a second groove at the other side of the bottom surface of the light-emitting body;

[0044] The conductive body includes a conductive substrate 12 and a P electrode layer 10;

[0045] The conductive substrate 12 partially covers the second insulating layer 8 through a metal bonding layer 11 and is connected to the N electrode layer 9. The P electrode layer 10 is arranged in the second groove and is connected to the protective metal layer 7.

[0046] Specifically, the conductor of the vertical structure LED in the embodiments of the present application is used for bonding connection. Among them, the conductor substrate is connected to the N electrode layer 9 through the metal bonding layer 11 and can be used as the N electrode of the LED. The P electrode layer 10 can be used as the P electrode. The conductive substrate 12 and the P electrode layer 10 are respectively located on both sides of the bottom of the vertical structure LED in the embodiments of the present application. Therefore, the vertical structure LED in the embodiments of the present application can be packaged based on flip-chip bonding, that is, the conductive substrate 12 and the P electrode layer 10 are welded on a specific pad or circuit to complete the bonding package. During the packaging process, there is no need to use gold wires for bonding additionally, which can effectively reduce the problem of gold wire breakage, thereby improving the reliability and stability of the LED device.

[0047] More specifically, the existing conductive substrate 12 is generally prepared from a silicon-based material. The silicon substrate that completely covers the bottom in the vertical structure LED will absorb light, thereby causing a decrease in the light output power. However, the vertical structure LED in the embodiments of the present application is provided with the conductive substrate 12 in a partially covered form, effectively reducing the occupied area of the conductive substrate 12, thereby reducing the absorption of visible light by the conductive substrate 12, and further improving the light output power of the vertical structure LED in the embodiments of the present application. Moreover, the conductive substrate 12 has a certain deformation range, which can effectively release the packaging stress and improve the stability of the packaging structure prepared based on the vertical structure in the embodiments of the present application.

[0048] More specifically, the N electrode layer 9 is prepared by filling the first groove that penetrates to the N-GaN layer 2 in the light-emitting body. It forms an ohmic contact with the light-emitting body through the second insulating layer 8 and is connected to the conductive substrate 12 through the metal bonding layer 11, so that the part of the N electrode layer 9 that does not form a coverage of the light-emitting surface will not block the light-emitting surface, effectively expanding the light-emitting area of the vertical structure LED, and further improving the light-emitting efficiency.

[0049] More specifically, in this embodiment, the top surface of the light-emitting body has an exposed first insulating layer 1, and the part of the bottom surface except for the conductive substrate 12 and the P electrode layer 10 also has an exposed second insulating layer 8, which can effectively protect the surface of the vertical structure LED and improve the reliability of the vertical structure LED.

[0050] The vertical structure LED in the embodiments of the present application can be flip-chip bonded and packaged based on the conductive substrate 12 and the P electrode layer 10, which can effectively reduce the problem of gold wire breakage, thereby improving the reliability and stability of the LED device. Moreover, the N electrode layer 9 is led out based on the conductive substrate 12 that partially covers the second insulating layer 8, which can effectively reduce the light blocking of the N electrode and the light absorption of the silicon substrate, effectively improving the light-emitting efficiency of the vertical LED structure, and further improving the light output power.

[0051] In some preferred embodiments, the bottom surface of the P electrode layer 10 is flush with the bottom surface of the conductive substrate 12.

[0052] Specifically, based on the foregoing, it can be known that the vertical structure LED of the embodiment of the present application is applicable to flip-chip bonding. The bottom surface of the P electrode layer 10 is designed to be flush with the bottom surface of the conductive substrate 12, which can ensure the stability and balance during the bonding and packaging of the vertical structure LED of the embodiment of the present application, so as to ensure that the light-emitting surface of the vertical structure LED is parallel to the bonding surface and emits light outward in a direction perpendicular to the bonding surface.

[0053] More specifically, in the embodiment of the present application, the vertical structure LED preferably prepares the conductive substrate 12 first and then prepares the P electrode layer 10; wherein, the thickness of the P electrode layer 10 is preferably the sum of the thicknesses of the second insulating layer 8, the metal bonding layer 11, and the conductive substrate 12 on the protective metal layer 7. By controlling the thickness during deposition, the P electrode layer 10 with a bottom surface flush with the bottom surface of the conductive substrate 12 can be quickly prepared.

[0054] In some preferred embodiments, the depth of the first groove in the N-GaN layer 2 is 1 / 4 - 1 / 2 of the thickness of the N-GaN layer 2.

[0055] Specifically, the depth of the first groove determines the forming depth of the N electrode layer 9. Designing the depth of the first groove in the N-GaN layer 2 to be 1 / 4 - 1 / 2 of the thickness of the N-GaN layer 2 can expand the ohmic contact area between the N electrode layer 9 and the N-GaN layer 2 and effectively avoid light shielding by the N electrode layer 9.

[0056] In some preferred embodiments, the width of the conductive substrate 12 is less than 1 / 2 of the width of the second insulating layer 8 on the protective metal layer 7.

[0057] Specifically, the conductive substrate 12 is used as the PAD terminal connecting the N electrode layer 9, and it is necessary to weaken the light absorption effect as much as possible. Therefore, in this embodiment, the width of the conductive substrate 12 is designed to be less than 1 / 2 of the width of the second insulating layer 8 on the protective metal layer 7.

[0058] More specifically, the conductive substrate 12 used as the PAD segment also needs to have a stable supporting effect. Therefore, the width of the conductive substrate 12 is further preferably designed to be 1 / 3 - 1 / 2 of the width of the second insulating layer 8 on the protective metal layer 7.

[0059] In some preferred embodiments, the P electrode layer 10 completely covers the second groove.

[0060] Specifically, the P electrode layer 10 completely covering the second groove makes the protective metal layer 7 have no exposed part, thereby further improving the reliability of the vertical structure LED of the embodiment of the present application.

[0061] In some preferred embodiments, the metal bonding layer 11 is prepared from any two or more of nickel, gold, tin, and titanium.

[0062] Specifically, the metal bonding layer 11 is used to connect the N electrode layer 9 and the conductive substrate 12. Prepared from any two of the above metal materials, it can effectively enhance conductivity, improve the utilization rate of current, ensure that the conductive substrate 12 can be used as a bonding end, and can effectively enhance the mechanical strength of the layer and reduce material costs. Its preparation materials can be used in combination according to the required scenarios.

[0063] In some preferred embodiments, the reflective metal layer 6 is prepared from silver or aluminum.

[0064] In some preferred embodiments, the protective metal layer 7 is prepared from titanium, TiW, or nickel.

[0065] In some preferred embodiments, both the N electrode layer 9 and the P electrode layer 10 are prepared from any two or more of titanium, chromium, silver, and gold.

[0066] In some preferred embodiments, the conductive substrate 12 is a Si substrate with a thickness of 250 - 1000 nanometers, and the metal bonding layer 11 has a thickness of 0.5 - 5 micrometers.

[0067] In some preferred embodiments, the reflective metal layer 6 has a thickness of 0.1 - 2 micrometers and the protective metal layer 7 has a thickness of 0.1 - 2 micrometers.

[0068] In some preferred embodiments, the materials of both the first insulating layer 1 and the second insulating layer 8 are SiO 2 , and both have a thickness of 0.1 - 2 micrometers.

[0069] It should be noted that Figure 1 and Figure 3 are only used to express the matching relationship between each layer, rather than the thickness relationship between each layer.

[0070] In a second aspect, please refer to Figure 2 and Figure 3 , some embodiments of the present application also provide a method for manufacturing a vertical - structure LED. The method includes the steps:

[0071] S1. Set the substrate 13, and sequentially prepare a buffer layer 14, an N - GaN layer 2, an MQWs layer 3, an EBL layer 4, a P - GaN layer 5, a reflective metal layer 6, and a protective metal layer 7 on the substrate to obtain a light - emitting body;

[0072] S2. Set a first groove on the light - emitting body that penetrates through to the N - GaN layer 2;

[0073] S3. Deposit a second insulating layer 8 on the protective metal layer 7 and the inner surface of the first groove, and fabricate an N electrode layer 9 in the first groove;

[0074] S4. Deposit a metal bonding layer 11 on the light-emitting body and bond a conductive substrate 12;

[0075] S5. Selectively strip the metal bonding layer 11 and the conductive substrate 12 to expose a part of the second insulating layer 8, and remove a part of the exposed second insulating layer 8 to form a second groove;

[0076] S6. Fabricate a P electrode layer 10 connected to the protective metal layer 7 on the second groove;

[0077] S7. Remove the substrate 13 and the buffer layer 14 to expose the N-GaN layer 2, and grow a first insulating layer 1 on the N-GaN layer 2.

[0078] Specifically, step S2 can form the first groove by means of etching or drilling, and the first groove completely penetrates through the MQWs layer 3, the EBL layer 4, the P-GaN layer 5, the reflective metal layer 6, and the protective metal layer 7.

[0079] More specifically, step S3 can be directly depositing the second insulating layer 8 covering the protective metal layer 7 and the inner surface of the first groove, or depositing an insulating layer covering the protective metal layer 7 and filling the first groove first, and then removing a part of the insulating layer in the first groove to form the second insulating layer 8. The N electrode layer 9 formed on this basis forms an ohmic contact with the N-GaN layer 2 through the second insulating layer 8.

[0080] More specifically, step S5 removes a part of the metal bonding layer 11 and the conductive substrate 12 by selective stripping technology to expose the surface of a part of the second insulating layer 8, and then removes a part of the exposed second insulating layer 8 on the surface by selective stripping technology to form a second groove; the practice of removing a part of the metal bonding layer 11 and the conductive substrate 12 can effectively reduce the occupied area of the conductive substrate 12, thereby reducing the absorption of visible light by the conductive substrate 12, and further improving the light output power of the vertical structure LED of the embodiment of the present application; the practice of forming the second groove is conducive to positioning and fabricating the P electrode layer 10.

[0081] More specifically, the substrate 13 can be removed by means of mechanical grinding and etching with an etching solution, and the buffer layer can be removed by means of ICP etching.

[0082] It should be noted that since the first insulating layer 1 is located on the other side of the vertical structure LED away from the conductive substrate 12, step S7 needs to be performed after flipping the entire chip.

[0083] The method for fabricating the vertical structure LED according to the embodiment of the present application can conveniently and orderly fabricate the vertical structure LED provided in the first aspect.

[0084] The vertical structure LED fabricated by the method for fabricating a vertical structure LED according to the embodiments of the present application can be flip-chip bonded and packaged based on the conductive substrate 12 and the P electrode layer 10, which can effectively reduce the occurrence of gold wire breakage, thereby improving the reliability and stability of the LED device. Moreover, the N electrode layer 9 is led out based on the conductive substrate 12 partially covering the second insulating layer 8, which can effectively reduce the light blocking of the N electrode and the light absorption of the silicon substrate, effectively improving the light emitting efficiency of the vertical LED structure and further increasing the light output power.

[0085] In the description of the present specification, the description with reference to terms such as "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0086] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A vertical structure LED, characterized in that, the vertical structure LED includes a light-emitting body and a conductor arranged vertically; the light-emitting body includes a first insulating layer, an N-GaN layer, an MQWs layer, an EBL layer, a P-GaN layer, a reflective metal layer, a protective metal layer, and a second insulating layer that are connected layer by layer from top to bottom; one side of the bottom surface of the light-emitting body has a first groove penetrating to the N-GaN layer, and the first groove is filled with an N electrode layer based on the inner surface covering the second insulating layer, and the second insulating layer has a second groove at the other side of the bottom surface of the light-emitting body; the conductor includes a conductive substrate and a P electrode layer; the conductive substrate partially covers the second insulating layer through a metal bonding layer and is connected to the N electrode layer, and the P electrode layer is arranged in the second groove and connected to the protective metal layer; the bottom surface of the P electrode layer is flush with the bottom surface of the conductive substrate; the depth of the first groove in the N-GaN layer is 1 / 4 - 1 / 2 of the thickness of the N-GaN layer; the width of the conductive substrate is less than 1 / 2 of the width of the second insulating layer on the protective metal layer; the P electrode layer completely covers the second groove.

2. The vertical structure LED according to claim 1, characterized in that, the metal bonding layer is prepared from any two or more of nickel, gold, tin, and titanium.

3. The vertical structure LED according to claim 1, characterized in that, the reflective metal layer is prepared from silver or aluminum.

4. The vertical structure LED according to claim 1, characterized in that, the protective metal layer is prepared from titanium, TiW, or nickel.

5. The vertical structure LED according to claim 1, characterized in that, both the N electrode layer and the P electrode layer are prepared from any two or more of titanium, chromium, silver, and gold.

6. A method for manufacturing a vertical structure LED, characterized in that, for manufacturing the vertical structure LED according to any one of claims 1-5, the method includes the steps: S1. Set a substrate, and sequentially prepare a buffer layer, an N-GaN layer, an MQWs layer, an EBL layer, a P-GaN layer, a reflective metal layer, and a protective metal layer on the substrate to obtain a light-emitting body; S2. Set a first groove on the light-emitting body that penetrates to the N-GaN layer; S3. Deposit a second insulating layer on the protective metal layer and the inner surface of the first groove, and prepare an N electrode layer in the first groove; S4. Deposit a metal bonding layer on the light-emitting body and bond a conductive substrate; S5. Selectively peel the metal bonding layer and the conductive substrate to expose a part of the second insulating layer, and remove a part of the exposed second insulating layer to form a second groove; S6. Prepare a P electrode layer connected to the protective metal layer on the second groove; S7. Remove the substrate and the buffer layer to expose the N-GaN layer, and grow a first insulating layer on the N-GaN layer.

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