Vertical-cavity surface-emitting laser and its fabrication method
By placing a p-type electrode on the contact layer of the active layer in a vertical cavity surface-emitting laser and setting a heat dissipation electrode on it, the problems of free carrier absorption and self-heating are solved, resulting in better heat dissipation and optical performance.
Patent Information
- Application Number
- CN202210392525.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-04-14
- Publication Date
- 2026-03-06
- Estimated Expiration
- 2042-04-14
AI Technical Summary
Traditional vertical-cavity surface-emitting lasers (VCSELs) suffer from free carrier absorption and self-heating in high-power applications, leading to increased optical power loss and heat generation, which affects device performance.
A p-type electrode is placed on the contact layer above the active layer, and a heat dissipation electrode is placed on the p-type electrode, extending from the first step to the second step to increase the heat dissipation area. At the same time, an air ring is formed between the contact layer and the upper grating layer to achieve opto-isolation.
It effectively reduces free carrier absorption and self-heating, improves heat dissipation performance, maintains the optical performance of the laser without increasing the device size, and has an ingenious design and simple process.
Smart Images
Figure CN114825030B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lasers, and particularly relates to a vertical cavity surface-emitting laser and its fabrication method. Background Technology
[0002] Currently, high-power vertical-cavity surface-emitting lasers (VCSELs) for applications such as mobile phone facial recognition, laser printing, and LiDAR are a key research focus for surface-emitting optoelectronic devices. They offer advantages such as high electro-optical conversion efficiency, small divergence angle, minimal wavelength temperature drift, and ease of wafer-level screening and inspection. Compared to side-emitting lasers, VCSELs offer higher chip yields. VCSELs typically use GaAs as a substrate and a lattice-matched active region as the emitting area, with a lasing wavelength of approximately 600–1300 nm. Post-fabrication processes are relatively simple. However, traditional p-type metal electrodes require current injection from the p-type doped Bragg reflector (DBR) surface into the quantum well active region. This process generates significant free carrier absorption and self-heating in thicker p-type materials. For high-power lasers, minimizing power loss and heat generation requires improved design of the p-type metal electrodes. Summary of the Invention
[0003] The purpose of this invention is to provide a vertical cavity surface-emitting laser and its fabrication method, which can effectively reduce free carrier absorption and self-heating, and has good heat dissipation.
[0004] To achieve the above objectives, the present invention provides a vertical cavity surface-emitting laser, comprising a substrate, a lower grating layer, an active layer, a contact layer, and an upper grating layer arranged sequentially from bottom to top. The upper grating layer protrudes from the middle of the contact layer, and a first step is formed between the outer peripheral wall of the upper grating layer and the contact layer. The contact layer and the active layer protrude from the middle of the lower grating layer, and a second step is formed between the outer peripheral walls of the contact layer and the active layer and the lower grating layer. A p-type electrode is provided on the contact layer, and a heat dissipation electrode is also provided on the p-type electrode. The heat dissipation electrode extends from the first step to the second step.
[0005] Preferably, a gap is provided between the inner peripheral wall of the heat dissipation electrode above the contact layer and the outer peripheral wall of the upper grating layer to form an air ring.
[0006] Preferably, a first protective layer is provided on the first step portion except for the area where the p-type electrode is located, and a second protective layer is provided on the second step portion. The heat dissipation electrode covers at least a portion of the second protective layer or the heat dissipation electrode covers at least a portion of the first protective layer and at least a portion of the second protective layer.
[0007] This invention also provides a method for fabricating a vertical-cavity surface-emitting laser, characterized by the following steps: growing a lower grating layer, an active layer, a contact layer, and an upper grating layer sequentially from bottom to top on a substrate; etching a first edge of the upper grating layer until the contact layer is exposed, such that the upper grating layer protrudes from the middle of the contact layer and a first step is formed between the outer peripheral wall of the upper grating layer and the contact layer; growing a p-type electrode on the contact layer, the p-type electrode being located outside the upper grating layer; etching downwards from a second edge of the contact layer until the lower grating layer is exposed, such that the contact layer and the active layer protrude from the middle of the lower grating layer and a second step is formed between the outer peripheral wall of the contact layer and the active layer and the lower grating layer, the second edge being located outside the p-type electrode; growing a heat dissipation electrode on the p-type electrode, the heat dissipation electrode extending from the first step to the second step.
[0008] Preferably, the step of growing a p-type electrode on the contact layer, wherein the p-type electrode is located outside the upper grating layer, includes: growing a first protective layer on the first step portion, and etching a window in the first protective layer at the location corresponding to the p-type electrode until the contact layer is exposed to form a p-type electrode growth region; and growing a p-type electrode on the p-type electrode growth region on the contact layer.
[0009] Preferably, the step of growing a heat dissipation electrode on the p-type electrode, wherein the heat dissipation electrode extends from the first step portion to the second step portion includes: growing a second protective layer on the second step portion and the p-type electrode; etching a window in the second protective layer at the location corresponding to the p-type electrode until the p-type electrode is exposed; growing a heat dissipation electrode on the p-type electrode, the first protective layer, and the second protective layer, wherein the heat dissipation electrode is located on the inner peripheral wall above the contact layer and connected to the first protective layer, and the heat dissipation electrode extends from the first step portion to the second step portion.
[0010] Preferably, after the step of growing a heat dissipation electrode on the p-type electrode, the first step portion, and the second step portion, wherein the heat dissipation electrode is located on the inner peripheral wall above the contact layer and connected to the first protective layer, and the heat dissipation electrode extends from the first step portion to the second step portion, the method further includes: etching the heat dissipation electrode connected to the first protective layer so that a gap is provided between the heat dissipation electrode and the outer peripheral wall of the first protective layer to form an air ring.
[0011] Preferably, an oxide layer is further provided between the contact layer and the active layer. The etching proceeds downward from the second edge of the contact layer until the lower grating layer is exposed, so that the contact layer and the active layer protrude from the middle of the lower grating layer and a second step is formed between the outer peripheral wall of the contact layer and the active layer and the lower grating layer. The second edge is located outside the p-type electrode. After the step, the method further includes: performing wet oxidation on the oxide layer; controlling the wet oxidation time so that the edge region of the oxide layer is oxidized while the middle region is not oxidized.
[0012] Preferably, the upper grating layer is an undoped intrinsic Bragg reflector layer.
[0013] Preferably, the substrate is an n-type substrate, and an n-type electrode is grown below the n-type substrate.
[0014] Compared with existing technologies, the vertical-cavity surface-emitting laser (VCSEL) places the p-type electrode on the contact layer above the active layer, rather than above the upper grating layer. This results in a closer distance between the p-type electrode and the active layer, effectively reducing free carrier absorption and self-heating. Furthermore, the addition of a heat dissipation electrode on the p-type electrode, extending from the first step to the second step, further increases the heat dissipation area. This design not only improves the heat dissipation performance of the VCSEL but also avoids increasing its volume and altering its optical performance. The design is ingenious, simple to manufacture, and easy to implement. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure of a vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0016] Figure 2 This is a schematic diagram of a wafer structure in which a lower grating layer, an isolation layer, an active layer, an oxide layer, a contact layer, an etch barrier layer, and an upper grating layer are grown on a substrate 1 in the method for fabricating a vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0017] Figure 3 The method for fabricating a vertical-cavity surface-emitting laser in an embodiment of the present invention... Figure 2 A schematic diagram of the structure formed by etching the middle wafer to create the first step.
[0018] Figure 4 This is a schematic diagram of the structure after the first protective layer is grown on the first step in the fabrication method of the vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0019] Figure 5 This is a schematic diagram of the structure of the p-type electrode growth region formed on the first protective layer in the method for fabricating a vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0020] Figure 6 This is a schematic diagram of the structure of growing a p-type electrode in the p-type electrode growth region in the vertical cavity surface-emitting laser fabrication method of this invention.
[0021] Figure 7 This is a schematic diagram of the structure in which the second step is formed by etching in the fabrication method of the vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0022] Figure 8This is a schematic diagram of the structure after oxidation of the oxide layer in the fabrication method of the vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0023] Figure 9 This is a schematic diagram of the structure after forming the second protective layer and etching away the second protective layer on the p-type electrode in the fabrication method of the vertical cavity surface-emitting laser according to an embodiment of the present invention.
[0024] Figure 10 This is a schematic diagram of the structure after growing the heat dissipation electrode and the n-type electrode in the vertical cavity surface-emitting laser fabrication method of this invention.
[0025] Figure 11 This is a band structure diagram of a vertical cavity surface-emitting laser according to an embodiment of the present invention. Detailed Implementation
[0026] To illustrate the technical content, structural features, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.
[0027] like Figure 1 As shown, an embodiment of the present invention discloses a vertical cavity surface-emitting laser, comprising a substrate 1, a lower grating layer 2, an active layer 4, a contact layer 6, and an upper grating layer 7 arranged sequentially from bottom to top. The upper grating layer 7 protrudes from the middle of the contact layer 6, and a first step portion 14 is formed between the outer peripheral wall of the upper grating layer 7 and the contact layer 6. The contact layer 6 and the active layer 4 protrude from the middle of the lower grating layer 2, and a second step portion 15 is formed between the outer peripheral walls of the contact layer 6 and the active layer 4 and the lower grating layer 2. A p-type electrode 9 is provided on the contact layer 6, and a heat dissipation electrode 10 is also provided on the p-type electrode 9. The heat dissipation electrode 10 extends from the first step portion 14 to the second step portion 15.
[0028] Specifically, the substrate 1 is an n-type substrate made of gallium arsenide (GaAs) with a thickness of 100 micrometers and a diameter determined by the wafer size. Below the substrate 1, a planar n-type electrode 13 is disposed, with a thickness of 2–10 μm. The lower grating layer 2 is an n-type doped Bragg grating layer, consisting of alternating layers of gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) layers (GaAs / AlGaAs), with a thickness of 3–15 μm. An isolation layer 3 is provided between the active layer 4 and the lower grating layer 2. The isolation layer 3 separates the active layer 4 from the lower grating layer 2 and is composed of several gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) layers, with a thickness of 50 nm–1 μm and a radius of 10–50 micrometers. The active layer 4 can be a narrowband system. The material is InGaAs, etc., with a thickness of 30nm to 50nm. The contact layer 6 is made of heavily doped p-type doped GaAs with a thickness of 200 to 300nm. An oxide layer 5 is provided between the active layer 4 and the contact layer 6. The oxide layer has a thickness of 10 to 50nm. The edge region 51 of the oxide layer 5 is oxidized, while the central region 52 of the oxide layer 5 is not oxidized. The upper grating layer 7 is an undoped intrinsic Bragg reflector layer with a thickness of 2 to 5µm and a diameter of 3 to 30µm. The p-type electrode 9 is annular and surrounds the upper grating layer 7. The p-type electrode 9 is made of titanium-platinum-gold (Ti-Pt-Au) alloy with a width of 2 to 6µm and a thickness of 10 to 500nm. The heat dissipation electrode 10 is made of gold. The thickness of the heat dissipation electrode 10 on the contact layer 6 is 2 to 5µm, and the thickness on the lower grating layer 2 is 2 to 8µm.
[0029] In this embodiment of the invention, the vertical-cavity surface-emitting laser (VCSEL) places the p-type electrode 9 on the contact layer 6 above the active layer 4, rather than above the upper grating layer 7. This makes the distance between the p-type electrode 9 and the active layer 4 closer, effectively reducing free carrier absorption and self-heating. In addition, since a heat dissipation electrode 10 is also provided on the p-type electrode 9 and extends from the first step portion 14 to the second step portion 15, the heat dissipation area of the heat dissipation electrode 10 is further increased. This design can improve the heat dissipation performance of the VCSEL on the one hand, and on the other hand, the heat dissipation electrode 10 with a stepped structure does not increase the volume of the VCSEL and does not change the optical performance of the VCSEL. The design is ingenious, and the process is simple and easy to implement.
[0030] In this embodiment of the invention, a gap is provided between the inner peripheral wall of the heat dissipation electrode 10 above the contact layer 6 and the outer peripheral wall of the upper grating layer 7 to form an air ring 16. The air ring 16 is arranged around the upper grating layer 7, and the width of the air ring 16 is 1 to 2 micrometers, so that the heat dissipation electrode 10 and the undoped upper grating layer 7 are completely photoelectrically isolated, which can further reduce light absorption and loss.
[0031] In this embodiment of the invention, a first protective layer 11 is provided on the first step portion 14 except for the area where the p-type electrode 9 is located. The material of the first protective layer 11 is silicon nitride and the thickness is 200-500 nm. A second protective layer 12 is provided on the second step portion 15. The material of the second protective layer 12 is silicon nitride and the thickness is 50-300 nm. The heat dissipation electrode 10 covers the second protective layer 12.
[0032] It should be noted that the heat dissipation electrode 10 can completely cover the second protective layer 12 or only cover a part of the second protective layer 12. For example, the second peripheral wall of the heat dissipation electrode 10 located on the lower grating layer 2 facing the outer side of the vertical cavity surface laser is not aligned with the outer peripheral wall of the lower grating layer 2, and is located on the inner side of the outer peripheral wall of the lower grating layer 2. Similarly, the heat dissipation electrode 10 can completely cover the first protective layer 11 or only cover a part of the first protective layer 11, as long as the heat dissipation electrode 10 on the first step portion 14 is connected to the heat dissipation electrode 10 on the second step portion 15. The purpose of setting the heat dissipation electrode 10 is to increase the area of the electrode, thereby increasing the heat dissipation area. The specific structure can be set according to actual needs.
[0033] This invention also discloses a method for fabricating a vertical-cavity surface-emitting laser, such as... Figures 1 to 10 As shown, it includes the following steps:
[0034] S1. A lower grating layer 2, an active layer 4, a contact layer 6, and an upper grating layer 7 are grown sequentially from bottom to top on a substrate 1 to form a wafer, wherein the upper grating layer 7 is an undoped intrinsic Bragg reflector layer.
[0035] S2. Etch the first edge of the upper grating layer 7 until the contact layer 6 is exposed so that the upper grating layer 7 protrudes from the middle of the contact layer 6 and a first step portion 14 is formed between the outer peripheral wall of the upper grating layer 7 and the contact layer 6; specifically, dry etching and wet etching can be combined to precisely etch to the contact layer 6.
[0036] S3. A p-type electrode 9 is grown on the contact layer 6, the p-type electrode 9 being located outside the upper grating layer 7. Specifically, a ring-shaped p-type electrode 9 can be formed by sputtering metal to create an ohmic contact.
[0037] S4. Etch downwards from the second edge of the contact layer 6 until the lower grating layer 2 is exposed, so that the contact layer 6 and the active layer 4 protrude from the middle of the lower grating layer 2 and a second step portion 15 is formed between the outer peripheral wall of the contact layer 6 and the active layer 4 and the lower grating layer 2. The second edge is located outside the p-type electrode 9. Specifically, dry or wet etching can be used to etch down to the lower grating layer 2. It can be precisely etched down to the upper surface of the lower grating layer 2 or down to the interior of the lower grating layer.
[0038] S5. A heat dissipation electrode 10 is grown on the p-type electrode 9, the heat dissipation electrode 10 extending from a first step portion 14 to a second step portion 15. Specifically, metal is sputtered onto the first step portion 14 and the second step portion 15 to form a relatively thick heat dissipation electrode 10.
[0039] Specifically, the substrate 1 is an n-type substrate made of gallium arsenide (GaAs) with a thickness of 100 micrometers, the diameter of which is determined by the wafer size. The lower grating layer 2 is an n-type doped Bragg grating layer, consisting of alternating layers of gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) layers (GaAs / AlGaAs), with a thickness of 3–15 μm. An isolation layer 3 is provided between the active layer 4 and the lower grating layer 2. The isolation layer 3 is used to separate the active layer 4 from the lower grating layer 2, and is composed of several gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) layers, with a thickness of 50 nm–1 μm. The active layer 4 can be made of narrowband InGaAs or similar materials, with a thickness of 30nm to 50nm. The contact layer 6 is made of heavily doped p-type GaAs, with a thickness of 200 to 300nm. The upper grating layer 7 is an undoped intrinsic Bragg reflector layer with a thickness of 2 to 5µm. The p-type electrode 9 is annular and surrounds the upper grating layer 7. The p-type electrode 9 is made of titanium-platinum-gold (Ti-Pt-Au) alloy, with a width of 2 to 6µm and a thickness of 10 to 500nm. The heat dissipation electrode 10 is made of gold, with a thickness of 2 to 5µm on the contact layer 6 and 2 to 8µm on the lower grating layer 2.
[0040] In this embodiment, the p-type electrode 9 is grown on the contact layer 6 on the active layer 4, rather than on top of the upper grating layer 7. This results in a closer distance between the p-type electrode 9 and the active layer 4, effectively reducing free carrier absorption and self-heating. Furthermore, since a heat dissipation electrode 10 is also grown on the p-type electrode 9 and extends from the first step portion 14 to the second step portion 15, the heat dissipation area of the heat dissipation electrode 10 is further increased. This design improves the heat dissipation performance of the vertical cavity surface-emitting laser (VCSEL). On the other hand, the stepped structure of the heat dissipation electrode 10 does not increase the volume of the VCSEL and does not change its optical performance. The design is ingenious, simple to manufacture, and easy to implement.
[0041] In this embodiment of the invention, step S3, which involves growing a p-type electrode 9 on the contact layer 6, wherein the p-type electrode 9 is located outside the upper grating layer 7, includes:
[0042] S31. A first protective layer 11 is grown on the first step portion 14, and a window is etched at the position of the p-type electrode 9 corresponding to the first protective layer 11 until the contact layer 6 is exposed to form the p-type electrode growth region 91. Figure 5 As shown;
[0043] S32. A p-type electrode 9 is grown on the p-type electrode growth region 91 on the contact layer 6. This can be achieved by sputtering metal onto the surface of the contact layer 6, followed by coating with photoresist, pre-baking, photolithography exposure, etching of the sputtered metal, and removal of the photoresist, to form a specific annular titanium-platinum (Ti-Pt-Au) alloy p-type electrode 9. Figure 6 As shown.
[0044] In this embodiment of the invention, step S5, growing a heat dissipation electrode 10 on the p-type electrode 9, wherein the heat dissipation electrode 10 extends from the first step portion 14 to the second step portion 15, includes:
[0045] S51. A second protective layer 12 is grown on the second step portion 15 and the p-type electrode 9;
[0046] S52. Etch and open a window at the position of the p-type electrode 9 corresponding to the second protective layer 12 until the p-type electrode 9 is exposed;
[0047] S53. A heat dissipation electrode 10 is grown on the p-type electrode 9, the first protective layer 11 and the second protective layer 12. The heat dissipation electrode 10 is located on the inner peripheral wall above the contact layer 6 and is connected to the first protective layer 11. The heat dissipation electrode 10 extends from the first step portion 14 to the second step portion 15.
[0048] In this embodiment of the invention, step S5, which involves growing a heat dissipation electrode 10 on the p-type electrode 9, the first step portion 14, and the second step portion 15, wherein the inner peripheral wall of the heat dissipation electrode 10 located above the contact layer 6 is connected to the first protective layer 11 and the heat dissipation electrode 10 extends from the first step portion 14 to the second step portion 15, further includes the following:
[0049] S51. The heat dissipation electrode 10 connected to the first protective layer 11 is etched to create a gap between the heat dissipation electrode 10 and the outer peripheral wall of the first protective layer 11 to form an air ring 16. Specifically, as shown in the figure... Figure 1 As shown, a potassium iodide (KI) solution is used to etch the heat dissipation electrode 10 at its connection with the sidewall of the upper grating layer 7 to form an air ring 16. The width of the air ring 16 is 1 to 2 micrometers, which enables complete photoelectric isolation between the heat dissipation electrode 10 and the undoped upper grating layer 7, thereby further reducing light absorption and loss.
[0050] In this embodiment of the invention, an oxide layer 5 is further provided between the contact layer 6 and the active layer 4. The material of the oxide layer 5 is AlGaAs with an aluminum content of 98%. After step S4, "etching downwards from the second edge of the contact layer 6 until the lower grating layer 2 is exposed so that the contact layer 6 and the active layer 4 protrude from the middle of the lower grating layer 2 and a second step portion 15 is formed between the outer peripheral wall of the contact layer 6 and the active layer 4 and the lower grating layer 2, and the second edge is located outside the p-type electrode 9", the following is also included:
[0051] S61. Perform wet oxidation on oxide layer 5;
[0052] S62. Control the wet oxidation time so that the edge region 51 of the oxide layer 5 is oxidized while the central region 52 is not oxidized. Specifically, after the oxide layer 5 is exposed to the oxidation environment, aluminum will automatically oxidize to Al2O3, and the oxidation area will gradually extend from the outer edge to the center. By controlling the oxidation time, the oxidation depth can be controlled, thereby effectively controlling the size of the oxidation area and the light-emitting aperture (the unoxidized area).
[0053] In this embodiment of the invention, the substrate 1 is an n-type substrate 1, and an n-type electrode 13 is grown below the n-type substrate 1. The n-type electrode 13 has a planar structure and a thickness of 2-10 μm. The preparation method of the n-type electrode is as follows: after step S5 "growing a heat dissipation electrode 10 on the p-type electrode 9, the heat dissipation electrode 10 extending from the first step portion 14 to the second step portion 15", the method further includes step S7: thinning the substrate 1, and then performing metal evaporation on the lower surface of the thinned substrate 1 to form the n-type electrode 13. In some other embodiments, the n-type electrode 13 may also adopt the same structure as the p-type electrode, and a heat dissipation electrode may be grown on the n-type electrode to further increase the heat dissipation performance of the laser.
[0054] It should be noted that, in the embodiments of the present invention, as... Figures 1 to 10 As shown, an etching barrier layer 8 is provided between the upper grating layer 7 and the contact layer 6 to protect the bottom of the upper grating layer 7 from being etched.
[0055] Figure 11 This is a band structure diagram of a vertical-cavity surface-emitting laser (VCSEL) manufactured using the manufacturing method of this invention. A represents the conduction band, and B represents the valence band. Figure 11 As can be seen, the metal electrode region (p-type electrode 9 and heat dissipation electrode 10) provides hole carriers, but they are blocked by the high barrier of the oxide hole (edge region 51 of oxide layer 5) directly below the metal electrode region. This forces the holes to move laterally and enter the active region through the unoxidized middle region 52 of oxide layer 5, forming an effective hole injection. This makes the path of current injection from the electrode to the active region shorter, reduces the differential resistance of the laser, and reduces heat generation.
[0056] The above-disclosed examples are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention shall still fall within the scope of the present invention.
Claims
1. A vertical cavity surface emitting laser, characterized by, The application relates to a light-emitting diode (LED) and a preparation method thereof.
2. A method of manufacturing a vertical cavity surface emitting laser, characterized by, The LED comprises a substrate, a lower grating layer, an active layer, a contact layer and an upper grating layer which are sequentially arranged from bottom to top, the upper grating layer is protruded in the middle of the contact layer and a first step part is formed between the outer wall of the upper grating layer and the contact layer, the contact layer and the active layer are protruded in the middle of the lower grating layer and a second step part is formed between the outer wall of the contact layer and the active layer and the lower grating layer, a p-type electrode is arranged on the contact layer, a heat-dissipating electrode is further arranged on the p-type electrode, the heat-dissipating electrode extends from the first step part to the second step part, the substrate is an n-type substrate, an n-type electrode is further grown below the n-type substrate, a first protective layer is arranged on the first step part except the area where the p-type electrode is arranged, a second protective layer is arranged on the second step part, the heat-dissipating electrode covers at least part of the second protective layer or the heat-dissipating electrode covers at least part of the first protective layer and at least part of the second protective layer, and a gap is arranged between the inner wall of the heat-dissipating electrode above the contact layer and the outer wall of the first protective layer to form an air ring. The application relates to a light-emitting diode (LED) and a preparation method thereof. The LED comprises a substrate, a lower grating layer, an active layer, a contact layer and an upper grating layer which are sequentially arranged from bottom to top, the substrate is an n-type substrate; The first edge of the upper grating layer is etched until the contact layer is exposed so that the upper grating layer is protruded in the middle of the contact layer and a first step part is formed between the outer wall of the upper grating layer and the contact layer; The p-type electrode is grown on the contact layer and is located outside the upper grating layer; The second edge of the contact layer is etched downward until the lower grating layer is exposed so that the contact layer and the active layer are protruded in the middle of the lower grating layer and a second step part is formed between the outer wall of the contact layer and the active layer and the lower grating layer, the second edge is located outside the p-type electrode; The heat-dissipating electrode is grown on the p-type electrode and extends from the first step part to the second step part; The substrate is thinned, and the lower surface of the thinned substrate is subjected to metal evaporation to form an n-type electrode; The step of growing the p-type electrode on the contact layer and outside the upper grating layer comprises the following steps: The first protective layer is grown on the first step part, and the first protective layer is etched and windowed at the position corresponding to the p-type electrode until the contact layer is exposed to form a p-type electrode growth area; The p-type electrode is grown on the p-type electrode growth area on the contact layer; The step of growing the heat-dissipating electrode on the p-type electrode and extending the heat-dissipating electrode from the first step part to the second step part comprises the following steps: The second protective layer is grown on the second step part and the p-type electrode; The second protective layer is etched and windowed at the position corresponding to the p-type electrode until the p-type electrode is exposed; The heat-dissipating electrode is grown on the p-type electrode, the first protective layer and the second protective layer, the heat-dissipating electrode is connected to the inner wall above the contact layer and the heat-dissipating electrode extends from the first step part to the second step part; After the step of growing the heat dissipation electrode on the p-type electrode, the first step portion and the second step portion, the heat dissipation electrode being connected with the inner peripheral wall of the first protective layer and the heat dissipation electrode being extended from the first step portion to the second step portion, the method further comprises: After the step of etching the heat dissipation electrode connected with the first protective layer to form the air ring by providing a gap between the heat dissipation electrode and the outer peripheral wall of the first protective layer, the method further comprises:
3. The method of producing a vertical cavity surface emitting laser according to claim 2, wherein After the step of providing the oxidation layer between the contact layer and the active layer, and etching the contact layer from the second edge of the contact layer downwards until the lower grating layer is exposed to make the contact layer and the active layer protrude in the middle of the lower grating layer and form the second step portion between the outer peripheral wall of the contact layer and the active layer and the lower grating layer, the second edge being located outside the p-type electrode, the method further comprises: After the step of performing the wet oxidation on the oxidation layer, the method further comprises: After the step of controlling the wet oxidation time to make the edge area of the oxidation layer be oxidized and the middle area of the oxidation layer not be oxidized, the method further comprises:
4. The method of producing a vertical cavity surface emitting laser according to claim 2, wherein After the step of providing the upper grating layer as the undoped intrinsic Bragg reflection layer, the method further comprises: After the step of providing the upper grating layer as the undoped intrinsic Bragg reflection layer, the method further comprises: