A vertical cavity surface emitting laser and a method of manufacturing the same

Abstract

The application discloses a vertical cavity surface emitting laser and a manufacturing method thereof. The laser comprises a substrate, a first reflecting layer formed on the substrate, a plurality of light emitting units formed on the first reflecting layer and arranged linearly, a first ohmic metal layer formed on the light emitting units, a first groove arranged around the light emitting units, at least one second groove arranged between each adjacent light emitting unit, a first electrode covering the sidewalls and bottom walls of the first groove and the second groove and communicating the first ohmic metal layer, the first groove and the second groove, and a second electrode connected with the substrate. The vertical cavity surface emitting laser and the manufacturing method thereof can improve uneven distribution of light intensity and current.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and specifically relates to a vertical cavity surface-emitting laser and its manufacturing method. Background Technology

[0002] LiDAR demands increasingly higher performance from linear vertical cavity surface-emitting laser arrays. In addition to improving the performance of individual light-emitting units, the number of light-emitting units in a single channel and the density requirements between channels are also increasing. These demands lead to a continuous increase in the number of light-emitting units and channels per unit area, which compresses the scope of photomask design and layout, thereby reducing the width of the connecting metal between light-emitting units.

[0003] Under high-density design conditions, the narrow width of the connecting metal results in a large voltage drop, leading to uneven distribution of light intensity and current in the laser array. To improve this uneven distribution, electrodes of varying widths can be used to reduce the voltage drop generated by the connecting metal. However, while electrodes of unequal width at the front and back reduce the voltage difference, the wider metal also increases the area occupied by a single channel, thus reducing the number of channels per unit area. Alternatively, different oxide aperture sizes can be used to improve the uniformity of current distribution, but different oxide aperture sizes will lead to inconsistent optical characteristics, resulting in differences in the optical characteristics of the laser array at the front and back ends. Summary of the Invention

[0004] The purpose of this invention is to provide a vertical cavity surface-emitting laser and its manufacturing method. The vertical cavity surface-emitting laser reduces the resistance between the light-emitting units by setting a groove between adjacent light-emitting units and filling the groove with a first electrode, thereby avoiding uneven distribution of light intensity and current due to large voltage drop.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] The present invention provides a laser comprising:

[0007] Substrate;

[0008] A first reflective layer is formed on the substrate;

[0009] Multiple light-emitting units are formed on the first reflective layer and are arranged linearly;

[0010] A first ohmic metal layer is formed on the light-emitting unit;

[0011] A first groove is disposed around the light-emitting unit;

[0012] At least one second trench is provided between each adjacent light-emitting unit; and

[0013] A first electrode covers the sidewalls and bottom wall of the first trench and the second trench, and communicates with the first ohmic metal layer, the first trench, and the second trench; and

[0014] The second electrode is connected to the substrate.

[0015] Optionally, the depth of the first trench and / or the second trench remains at the first reflective layer or the substrate.

[0016] Optionally, the first trench and the second trench are connected, and the second trench is arranged along the center line connecting two adjacent light-emitting units.

[0017] Optionally, the first trench and the second trench are connected, and a plurality of the second trenches are arranged parallel to the center line connecting the two light-emitting units.

[0018] Optionally, a plurality of the second grooves are arranged perpendicular to the center line connecting the two light-emitting units.

[0019] Optionally, multiple stepped structures are formed between the sidewalls and bottom walls of the first trench and / or the second trench.

[0020] Optionally, the first trench and / or the second trench includes a first recess and a second recess, the second recess being located on the bottom wall of the first recess, and the etching depth of the second recess being greater than the etching depth of the first recess.

[0021] Optionally, the light-emitting unit includes an active layer, a second reflective layer, and a current-limiting layer, wherein the active layer is located on the first reflective layer, the second reflective layer is located on the active layer, and the current-limiting layer is disposed within the second reflective layer.

[0022] Optionally, the depth of the first recess may remain within the first reflective layer, the active layer, or the second reflective layer.

[0023] Optionally, the first electrode is higher than the light-emitting unit.

[0024] Optionally, the first electrode includes a first metal layer and a second metal layer, wherein the second metal layer is disposed on the first metal layer.

[0025] Optionally, the roughened area of ​​the second trench is the difference between the cross-sectional area of ​​the first electrode after the second trench is provided and the cross-sectional area of ​​the first electrode when the second trench is not provided.

[0026] Optionally, the effect of roughening can be evaluated using roughness ratio, where roughness ratio = roughened area / cross-sectional area of ​​the first electrode when no roughening structure is provided.

[0027] The present invention also provides a method for manufacturing a vertical-cavity surface-emitting laser, comprising at least:

[0028] Provide a substrate;

[0029] A first reflective layer is formed on the substrate;

[0030] Multiple light-emitting units are formed on the first reflective layer;

[0031] A first ohmic metal layer is formed on the light-emitting unit;

[0032] A first groove is formed on the outer side of each of the light-emitting units;

[0033] At least one second trench is formed between each adjacent light-emitting unit;

[0034] A first electrode is formed on the sidewall and bottom wall of the first trench and the second trench, and the first electrode connects the first ohmic metal layer, the first trench, and the second trench; and

[0035] A second electrode is formed that is connected to the substrate.

[0036] As described above, the vertical-cavity surface-emitting laser and its manufacturing method provided by the present invention form a roughened structure by creating trenches between adjacent light-emitting units. Filling the trenches with a metal layer increases the ramp area of ​​the metal layer, resulting in a larger electroplating area. This increases the conductive area of ​​the metal layer at the same electroplating thickness, thereby reducing the voltage drop between adjacent light-emitting units. By creating multiple second trenches and a stepped structure within the first and / or second trenches, the conductive area of ​​the metal layer can be further increased. The vertical-cavity surface-emitting laser and its manufacturing method provided by the present invention can reduce the voltage drop between adjacent light-emitting units by increasing the conductive area of ​​the metal layer between them, thereby improving the problem of uneven light intensity and current distribution.

[0037] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a diagram of the mounting structure of a vertical cavity surface-emitting laser.

[0040] Figure 2 A schematic diagram of the structure in which the first ohmic metal layer is formed in the A-A' direction.

[0041] Figure 3 for Figure 2 Top view.

[0042] Figure 4 A schematic diagram of the structure in which the first insulating layer is formed in the A-A' direction.

[0043] Figure 5 A schematic diagram of a light-emitting unit formed in the A-A' direction.

[0044] Figure 6 for Figure 5 Top view.

[0045] Figure 7 A schematic diagram of the structure forming the second groove in the B-B' direction.

[0046] Figure 8 This is a schematic diagram of a trench structure with a stepped structure.

[0047] Figure 9 A schematic diagram of the structure in which the second insulating layer is formed in the A-A' direction.

[0048] Figure 10 A schematic diagram of the structure in which the first electrode is formed in the A-A' direction.

[0049] Figure 11 for Figure 10 Top view.

[0050] Figure 12 This is a schematic diagram of the structure in which the second electrode is formed along the A-A' direction.

[0051] Figure 13 The area of ​​the roughened structure when the thickness of the first electrode in the B-B' direction is less than the trench depth.

[0052] Figure 14 The area of ​​the roughened structure when the thickness of the first electrode in the B-B' direction is equal to the trench depth.

[0053] Figure 15 The area of ​​the roughened structure when the thickness of the first electrode in the B-B' direction is greater than the trench depth.

[0054] Figure 16 This is a schematic diagram of a structure in another embodiment where a first ohmic metal layer is formed in the A-A' direction.

[0055] Figure 17 for Figure 16 Top view.

[0056] Figure 18 This is a schematic diagram of a structure in another embodiment where a first insulating layer is formed in the A-A' direction.

[0057] Figure 19 This is a schematic diagram of a light-emitting unit formed in the A-A' direction in another embodiment.

[0058] Figure 20 for Figure 19 Top view.

[0059] Figure 21 This is a schematic diagram of a structure in another embodiment where a second trench is formed in the B-B' direction.

[0060] Figure 22 This is a schematic diagram of a structure in which a second insulating layer is formed in the A-A' direction, as shown in another embodiment.

[0061] Figure 23 This is a schematic diagram of a structure in another embodiment where the first electrode is formed along the A-A' direction.

[0062] Figure 24 for Figure 23 Top view.

[0063] Figure 25 This is a schematic diagram of a structure in which a second electrode is formed in the A-A' direction, as shown in another embodiment.

[0064] Figure 26 This is a schematic diagram of a structure in which a first ohmic metal layer is formed in the A-A' direction in another embodiment.

[0065] Figure 27 for Figure 26 Top view.

[0066] Figure 28 This is a schematic diagram of the structure in which the first insulating layer is formed in the A-A' direction in another embodiment.

[0067] Figure 29 This is a schematic diagram of a light-emitting unit formed in the A-A' direction in another embodiment.

[0068] Figure 30 for Figure 29 Top view.

[0069] Figure 31 This is a schematic diagram of a structure in which a second trench is formed in the B-B' direction in another embodiment.

[0070] Figure 32 This is a schematic diagram of a structure in which a second insulating layer is formed in the A-A' direction in another embodiment.

[0071] Figure 33 This is a schematic diagram of a structure in which the first electrode is formed in the A-A' direction in another embodiment.

[0072] Figure 34 for Figure 33 Top view.

[0073] Figure 35 This is a schematic diagram of a structure in which a second electrode is formed in the A-A' direction in another embodiment. Detailed Implementation

[0074] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] Please see Figure 1 As shown, in some embodiments, the vertical-cavity surface-emitting laser 10 has a wide range of applications in manufacturing. For example, the vertical-cavity surface-emitting laser 10 can be used as a laser emitter in radar, a laser in a distance sensor, or a laser for optical communication. In this application, the vertical-cavity surface-emitting laser 10 includes a substrate and a plurality of light-emitting units on the substrate, and the plurality of light-emitting units are arranged linearly on the substrate, for example. When the vertical-cavity surface-emitting laser 10 is operating, it is soldered onto a circuit board 20. The circuit board 20 is provided with a driving circuit for driving the light-emitting units on the vertical-cavity surface-emitting laser 10 to emit light. The pads 21 connecting the vertical-cavity surface-emitting laser 10 are located at one end of the circuit board 20. Due to increasingly higher requirements for laser performance and size, the distance between adjacent light-emitting units is becoming smaller, resulting in a smaller width of the metal layer between adjacent light-emitting units, thus causing uneven distribution of light intensity and current. The vertical-cavity surface-emitting laser 10 provided by this invention can improve the uneven light emission caused by the increasingly smaller distance between light-emitting units.

[0076] Please see Figure 12 , Figure 25 or Figure 35 As shown, in one embodiment of the present invention, the vertical cavity surface emission laser 10 includes a substrate 101 / 201 / 301 and a plurality of light-emitting units 100 / 200 / 300 disposed on the substrate 101 / 201 / 301.

[0077] Please see Figure 2As shown, in one embodiment of the present invention, a substrate 101 is first provided, then a first reflective layer 102 is formed on the substrate 101, an active layer 103 is formed on the first reflective layer 102, and a second reflective layer 104 is formed on the active layer 103. In this embodiment, the substrate 101 can be any semi-insulating material suitable for forming a vertical-cavity surface-emitting laser 10. The substrate 101 is, for example, a semi-insulating gallium arsenide (GaAs) substrate, which is an undoped gallium arsenide substrate and has very high resistance. The resistivity of the semi-insulating gallium arsenide substrate is, for example, 107 Ω·cm or higher. In some embodiments, a conductive substrate or an insulating substrate can also be used instead of a semi-insulating substrate. In this case, the laser can be formed on the gallium arsenide substrate, separated from the gallium arsenide substrate, and then attached to a substrate with high thermal conductivity, such as an insulating aluminum nitride (AlN) substrate or a conductive copper substrate.

[0078] Please see Figure 2 As shown, in one embodiment of the present invention, the first reflective layer 102 may be composed of, for example, aluminum gallium arsenide (AlGaAs) and gallium arsenide, or a combination of aluminum gallium arsenide with high aluminum content and aluminum gallium arsenide with low aluminum content, stacked together. The first reflective layer 102 may be an N-type mirror, specifically an N-type Bragg mirror. The active layer 103 includes a stacked quantum well composite structure composed of gallium arsenide and aluminum gallium arsenide, or indium gallium arsenide (InGaAs) and aluminum gallium arsenide, stacked together. The active layer 103 can convert electrical energy into light energy. The second reflective layer 104 may be composed of a combination of aluminum gallium arsenide and gallium arsenide, or a combination of aluminum gallium arsenide with high aluminum content and aluminum gallium arsenide with low aluminum content, stacked together. The second reflective layer 104 may be a P-type mirror, specifically a P-type Bragg mirror. The first reflective layer 102 and the second reflective layer 104 are used to reflect and enhance the light generated by the active layer 103, and then emit it from the surface of the second reflective layer 104.

[0079] Please see Figure 2 As shown, in one embodiment of the present invention, the first reflective layer 102, the active layer 103 and the second reflective layer 104 can be formed, for example, by chemical vapor deposition.

[0080] Please see Figure 2 As shown, in one embodiment of the present invention, the total thickness of the first reflective layer 102, the active layer 103, and the second reflective layer 104 is, for example, 8 to 10 micrometers.

[0081] Please see Figure 2As shown, in one embodiment of the present invention, the first reflective layer 102 or the second reflective layer 104 comprises a series of alternating layers of materials with different refractive indices, wherein the effective optical thickness of each alternating layer (the layer thickness multiplied by the layer refractive index) is an odd integer multiple of one-quarter of the operating wavelength of the vertical-cavity surface-emitting laser 10, that is, the effective optical thickness of each alternating layer is one-quarter of an odd integer multiple of the operating wavelength of the vertical-cavity surface-emitting laser 10. Suitable dielectric materials for forming the alternating layers of the first reflective layer 102 or the second reflective layer 104 include tantalum oxide, titanium oxide, aluminum oxide, titanium nitride, silicon nitride, etc. Suitable semiconductor materials for forming the alternating layers of the first reflective layer 102 or the second reflective layer 104 include gallium nitride, aluminum nitride, and aluminum gallium nitride. However, this is not the only limitation; in some embodiments, the first reflective layer 102 and the second reflective layer 104 may also be formed of other materials.

[0082] Please see Figure 2 As shown, in some embodiments, the active layer 103 may include one or more nitride semiconductor layers, the semiconductor layers including one or more quantum well layers or one or more quantum dot layers sandwiched between corresponding pairs of blocking layers.

[0083] Please see Figure 2 As shown, in one embodiment of the present invention, a plurality of first ohmic metal layers 105 are also formed on the second reflective layer 104. The first ohmic metal layers 105 can serve as photolithography calibration references for subsequent processes, thereby fabricating a high-precision vertical-cavity surface-emitting laser 10. Simultaneously, the first ohmic metal layers 105 can also serve as metal contact pads for subsequent first electrodes. The material of the first ohmic metal layers 105 may include one or a combination of Au, Ag, Pt, Ge, Ti, and Ni metals, which can be selected as needed. In some embodiments, the surface of the second reflective layer 104 contacting the first ohmic metal layers 105 has a high doping concentration to form an ohmic contact layer, thereby reducing the contact resistance of the ohmic contact between the first ohmic metal layers 105 and the second reflective layer 104. The ohmic contact layer may be a P-type doped ohmic contact layer.

[0084] Please see Figure 2 as well as Figure 3 As shown, in one embodiment of the present invention, the shape of the first ohmic metal layer 105 may be, for example, an annular shape. In other embodiments, the shape of the first ohmic metal layer 105 may also be an elliptical annular shape, a rectangular annular shape, or a hexagonal annular shape. The shape of the first ohmic metal layer 105 can be selected as needed. In this embodiment, the inner diameter of the first ohmic metal layer 105 is, for example, 5–97 μm, and the outer diameter of the first ohmic metal layer 105 is, for example, 7–99 μm. In other embodiments, the inner and outer diameters of the first ohmic metal layer 105 may not be limited and can be selected as needed.

[0085] Please see Figure 4 As shown, in one embodiment of the present invention, after forming the first ohmic metal layer 105, a first insulating layer 106 is formed on the second reflective layer 104 and the first ohmic metal layer 105. The material of the first insulating layer 106 is, for example, silicon nitride, silicon oxide, or other insulating materials, and the first insulating layer 106 covers the first ohmic metal layer 105. The thickness of the first insulating layer 106 is, for example, 100–400 nm.

[0086] Please see Figures 5 to 7 As shown, after forming the first insulating layer 106, first trenches 108 are etched between adjacent first ohmic metal layers 105 to form light-emitting units 100, and second trenches 109 are etched between adjacent first trenches 108 to roughen the area between adjacent light-emitting units 100. In this embodiment, the first trenches 108 and the second trenches 109 can be etched simultaneously. Specifically, a patterned photoresist layer (not shown in the figure) can be formed on the first insulating layer 106, and the patterned photoresist layer covers the first ohmic metal layer 105, exposing part of the second reflective layer 104. Then, the second reflective layer 104 is etched downwards according to the patterned photoresist layer to form multiple first trenches 108 and second trenches 109. During etching, the first insulating layer 106 above the first trenches 108 and the second trenches 109 is also etched away simultaneously.

[0087] Please see Figures 5 to 7 As shown, in one embodiment of the present invention, the first trench 108 and the second trench 109 are connected, and the first trench 108 is disposed around the first ohmic metal layer 105. The width of the first trench 108 is, for example, 3 to 5 μm. The portion surrounded by the first trench 108 forms a terrace-shaped structure, which is used to form the light-emitting unit 100. The second trench 109 is disposed between adjacent first trenches 108 and is connected to the adjacent first trenches 108. The second trench 109 is disposed along the center line connecting the two terrace-shaped structures, and the number of second trenches 109 is, for example, one. The width W of the second trench 109 is, for example, 3 to 5 μm. The width of the second trench 109 is the maximum width achievable according to the manufacturing process.

[0088] Please see Figures 5 to 7As shown, the depths of the first trench 108 and the second trench 109 of the present invention are not limited. In some embodiments, the second reflective layer 104 and the active layer 103 are etched to expose the first reflective layer 102. In other embodiments, the second reflective layer 104, the active layer 103, and the first reflective layer 102 may also be etched to expose the substrate 101. In other embodiments, the second reflective layer 104, the active layer 103, the first reflective layer 102, and a portion of the substrate 101 may also be etched to extend the first trench 108 and the second trench 109 into the substrate 101.

[0089] Please see Figures 5 to 7 As shown, the depth and shape of the first groove 108 and the second groove 109 of the present invention are not limited. In some embodiments, the radial cross-section of the first groove 108 and the second groove 109 may be rectangular, polygonal, or other regular shapes. In this embodiment, the radial cross-section of the first groove 108 and the second groove 109 is, for example, rectangular.

[0090] Please see Figure 8 As shown, in some embodiments of the present invention, to increase the contact area between the first electrode 113 and the trench, the trench can be etched multiple times, forming multiple stepped structures between the bottom and sidewalls of the first trench 108 and the second trench 109. For example, a first etching can be performed on the second reflective layer 104 to form a first recess 114 with the morphology of the first trench 108 and the second trench 109, and the depth H1 of the first etching can, for example, stop at the first reflective layer 102, the active layer 103, or the second reflective layer 104. Then, a second etching is performed on the bottom wall of the first recess 114, and the depth H2 of the second etching is greater than the depth H1 of the first etching, so that a second recess 115 can be formed at the bottom of the first recess 114, and a stepped structure can be formed between the second recess 115 and the first recess 114. By analogy, multiple stepped structures can be formed in the first trench 108. This invention does not limit the number of stepped structures or the height of each stepped structure formed. The stepped structures can be formed according to the actual dimensions of the first trench 108 and the second trench 109 and the etching process. In a specific embodiment of this invention, for example, the second reflective layer 104, the active layer 103, and the first reflective layer 102 are etched to the surface of the substrate 101 to form a first recess 114. Then, the middle position of the bottom wall of the first recess 114 is etched, and part of the substrate 101 of the bottom wall of the first recess 114 is etched away to form a second recess 115. A stepped structure is formed between the second recess 115 and the first recess 114.

[0091] Please see Figure 5As shown, in one embodiment of the present invention, after forming the first trench 108 and the second trench 109, a current-limiting layer 107 needs to be formed within the mesa-shaped structure to form a light-emitting hole. In this embodiment, the sidewalls of the trenches are oxidized using a high-temperature oxidation method with high aluminum doping to form at least one current-limiting layer 107 within the second reflective layer 104. In this embodiment, at least one current-limiting layer 107 is formed within the second reflective layer 104 by oxidizing the sidewalls of the first trench 108.

[0092] Please see Figure 5 As shown, in one embodiment of the present invention, each mesa-shaped structure is a light-emitting unit 100. Each mesa-shaped structure includes, from bottom to top, at least an active layer 103, a second reflective layer 104, and a first ohmic metal layer 105. A current-limiting layer 107 is formed within the second reflective layer 104. The current-limiting layer 107 contacts the sidewall of the mesa-shaped structure and extends into the mesa-shaped structure. The current-limiting layer 107 within the mesa-shaped structure is an annular structure, and a light-emitting aperture is defined by the current-limiting layer 107.

[0093] Please see Figure 5 As shown, in this embodiment, in the mesa structure, the current limiting layer 107 located in the second reflective layer 104 extends to the inner diameter of the first ohmic metal layer 105, or the first ohmic metal layer 105 is located on the outer periphery of the light-emitting hole, so that the first electrode formed later does not block the light-emitting hole.

[0094] Please see Figure 5 As shown, in this embodiment, the outer diameter of the first ohmic metal layer 105 on the mesa structure is a certain distance from the edge of the mesa structure, for example, D1, and the range of D1 is, for example, 1 to 5 μm. Furthermore, the etched first insulating layer 106 only covers the surface of the mesa structure.

[0095] Please see Figure 5 As shown, in some embodiments, the current limiting layer 107 includes one of an air column type current limiting structure, an ion implantation type current limiting structure, a buried heterojunction type current limiting structure, and an oxidation limiting type current limiting structure. In this embodiment, an oxidation limiting type current limiting structure is used.

[0096] Please see Figure 5 , Figures 9 to 10As shown, in some embodiments, after forming the current limiting layer 107, a second insulating layer 110 is formed in the trench. The second insulating layer 110 covers the first trench 108, the second trench 109, and the first insulating layer 106, and openings may be provided on the first insulating layer 106 and the second insulating layer 110 above the first ohmic metal layer 105 to expose the first ohmic metal layer 105. The first insulating layer 106 and the second insulating layer 110 can insulatingly separate adjacent light-emitting units 100. The material of the second insulating layer 110 is, for example, silicon nitride or silicon oxide or other insulating materials, and the thickness of the second insulating layer 110 can be 100-200 nm. The second insulating layer 110 can protect the current limiting layer 107 and can also effectively isolate adjacent mesa structures. In this embodiment, the second insulating layer 110 can be formed, for example, by chemical vapor deposition.

[0097] Please see Figures 9 to 10 As shown, after forming the second insulating layer 110, a first electrode 113 is formed in the first trench 108, the second trench 109, and on a portion of the mesa structure, such that the first electrode 113 covers the bottom and sidewalls of the first trench 108 and the second trench 109, and connects the first trench 108, the second trench 109, and the first ohmic metal layer 105. To ensure the quality of the first electrode 113, the first electrode 113 may include multiple metal layers. In this embodiment, the first electrode 113 may, for example, include a first metal layer 111 and a second metal layer 112. First, metal is filled in the first trench 108, the second trench 109, and between the first ohmic metal layer 105 and the first trench 108 to form the first metal layer 111. The first metal layer 111 covers the bottom and sidewalls of the trench and connects the first ohmic metal layer 105, the first trench 108, and the second trench 109. Because the trench width is too large, a depression is easily formed in the middle of the trench during filling. Therefore, after filling the first metal layer 111, the second metal layer 112 is filled into the depression to fill the first trench 108 and / or the second trench 109. In this application, the first electrode 113 covers the sidewalls and bottom walls of the first trench 108 and the second trench 109, the insulating layer between the first ohmic metal layer 105 and the first trench 108, and the insulating layer between the first trench 108 and the second trench 109, to increase the climbing area of ​​the first electrode. In a specific embodiment, the height of the first electrode 113 is higher than that of the light-emitting unit 100, which can further increase the cross-sectional area of ​​the first electrode 113 to reduce the series resistance between the light-emitting units 100. In this embodiment, the material of the first electrode 113 can be one or a combination of metals such as Au metal, Ag metal, and Cu metal.

[0098] Please see Figures 12 to 15As shown, when the depth of the first electrode 113 in this invention is different, the roughening area 116 of each second trench 109 is different. The roughening area 116 of each second trench 109 is the increased cross-sectional area of ​​the first electrode 113 after the second trench 109 is provided, relative to when the second trench 109 is not provided. Figures 13 to 15 As shown, in one embodiment of the present invention, the cross-section of the second groove 109 is rectangular, and the depth of the second groove 109 is H, and the width is W. Figure 13 As shown, when the thickness h of the first electrode 113 is less than the depth H of the second trench 109, the roughened area 116 is equal to πh. 2 / 2+(Hh)h / 2. When the thickness h of the first electrode 113 is equal to the depth H of the second trench 109, the roughened area 116 is equal to πH. 2 / 2. When the thickness h of the first electrode 113 is greater than the depth H of the second trench 109, the roughened area 116 is equal to HW. If the manufacturing conditions allow, the roughness ratio can be used to evaluate the roughening effect, and the roughness ratio = roughened area / cross-sectional area of ​​the first electrode without a roughened structure. A higher roughness ratio indicates a better roughening effect.

[0099] Please see Figure 12 As shown, in one embodiment of the present invention, after forming the first electrode 113, the substrate 101 can be thinned. The thickness of the thinned substrate 101 is, for example, 2 to 10 μm, specifically, 5 μm. A second electrode 117 is formed on the side of the thinned substrate 101 opposite to the light-emitting unit 100. The material of the second electrode 117 may include one or a combination of Au, Ag, Pt, Ge, Ti, and Ni metals, which can be selected as needed. Since the substrate 101 is made of semiconductor material, multiple light-emitting units 100 can be connected through the second electrode 117, which serves as a common cathode. In other embodiments, the first reflective layer 102 can be electrically connected at both ends of the vertical cavity surface-emitting laser 10 and on the same side as the light-emitting unit 100.

[0100] Please see Figures 16 to 25 As shown, in another embodiment of the present invention, the second trench 209 differs from that in the previous embodiment. For details on the first trench 208 and the second trench 209, please refer to [link / reference needed]. Figures 19 to 21 As shown.

[0101] For details, please refer to Figures 16 to 18As shown, in this embodiment, a first reflective layer 202, an active layer 203, and a second reflective layer 204 are sequentially formed on a substrate 201. A first ohmic metal layer 205 is formed on the second reflective layer 204, and a first insulating layer 206 is formed on the first ohmic metal layer 205 and the second reflective layer 204. The formation process and materials described above are the same as those used for forming the first reflective layer 102, the active layer 103, the second reflective layer 104, the first ohmic metal layer 105, and the first insulating layer 106.

[0102] Please see Figures 19 to 21 As shown, in this embodiment, after forming the first insulating layer 206, a first trench 208 and a second trench 209 are etched. The first trench 208 and the second trench 209 are connected, and the first trench 208 is disposed around the first ohmic metal layer 205. The width of the first trench 208 is, for example, 3-5 μm. The portion surrounded by the first trench 208 forms a mesa structure, which is used to form the light-emitting unit 200. The second trench 209 is disposed between adjacent first trenches 208 and is connected to the adjacent first trenches 208. In this embodiment, the second trench 209 is disposed parallel to the center line connecting the two mesa structures. In other embodiments, the second trench 209 may be disposed at a certain angle to the center line connecting the two mesa structures, and multiple second trenches 209 are disposed parallel to each other. The width of the second trench 209 is, for example, 3-5 μm, and the distance between adjacent second trenches 209 is, for example, 2-4 μm. The present invention does not limit the number of second trenches 209. The number of second trenches 209 is at least two, and for example, three, four, or five. Specifically, it can be set according to the width of the light-emitting unit 200. In this embodiment, the shape, width, and depth of the first trench 208 and the second trench 209 can be as follows: Figure 8 The first groove 108 and the second groove 109 are also provided, and the number of second grooves 209 is, for example, 3. Since the cross-sectional area of ​​each second groove 209 is the same as that of the second groove 109, in this embodiment, the roughened area between adjacent light-emitting units 200 is 3 times the roughened area between adjacent light-emitting units 100.

[0103] Please see Figure 19 As shown, in this embodiment, after etching to form the first trench 208 and the second trench 209, a plurality of current-limiting layers 207 are formed in the second reflective layer 204 to form a light-emitting unit 200. The light-emitting unit 200 includes an active layer 203, a second reflective layer 204 and a first ohmic metal layer 205, and the current-limiting layers 207 are formed in the second reflective layer 204.

[0104] Please see Figures 22 to 25In this embodiment, after forming the light-emitting unit 200, a second insulating layer 210 is formed on the light-emitting unit 200, a first electrode 213 disposed on the second insulating layer 210 and connected to the first ohmic metal layer 205, and a second electrode 217 disposed on one side of the substrate 201. In this embodiment, the second insulating layer 210, the first electrode 213, and the second electrode 217 are configured the same as the second insulating layer 110, the first electrode 113, and the second electrode 117.

[0105] Please see Figures 26 to 35 As shown, in another embodiment of the present invention, the second trench 309 differs from that in the previous embodiment. For details on the first trench 308 and the second trench 309, please refer to [link / reference needed]. Figures 19 to 21 As shown.

[0106] For details, please refer to Figures 26 to 28 As shown, in this embodiment, a first reflective layer 302, an active layer 303, and a second reflective layer 304 are sequentially formed on a substrate 301. A first ohmic metal layer 305 is formed on the second reflective layer 304, and a first insulating layer 306 is formed on the first ohmic metal layer 305 and the second reflective layer 304. The formation process and materials described above are the same as those used for forming the first reflective layer 102, the active layer 103, the second reflective layer 104, the first ohmic metal layer 105, and the first insulating layer 106.

[0107] Please see Figures 29 to 31 As shown, in this embodiment, after forming the first insulating layer 306, a first trench 308 and a second trench 309 are etched. The first trench 308 and the second trench 309 are not connected. The first trench 308 surrounds the first ohmic metal layer 305, and the width of the first trench 308 is, for example, 3-5 μm. The portion surrounded by the first trench 308 forms a mesa-shaped structure, which is used to form the light-emitting unit 300. The second trench 309 is disposed between adjacent first trenches 308. In this embodiment, the second trench 309 is perpendicular to the center line connecting the two mesa-shaped structures. In other embodiments, the second trench 309 may be arranged at a certain angle to the center line connecting the two mesa-shaped structures, and multiple second trenches 309 are arranged in parallel. The width of the second trench 309 is, for example, 3-5 μm, and the distance between adjacent second trenches 309 is, for example, 2-4 μm. The present invention does not limit the number of second trenches 309. In this embodiment, the number of second trenches 309 is at least two, and for example, three, four, or five. Specifically, it can be set according to the distance between adjacent light-emitting units 200. In this embodiment, the shape and depth of the first trench 308 and the second trench 309 can be as follows: Figure 8 The first groove 108 and the second groove 109 are also configured in the same way.

[0108] Please see Figure 29 As shown, in this embodiment, after etching to form the first trench 308 and the second trench 309, a plurality of current-limiting layers 307 are formed in the second reflective layer 304 to form a light-emitting unit 300. The light-emitting unit 300 includes an active layer 303, a second reflective layer 304 and a first ohmic metal layer 305, and the current-limiting layers 307 are formed in the second reflective layer 304.

[0109] Please see Figures 32 to 35 In this embodiment, after forming the light-emitting unit 300, a second insulating layer 310 is formed on the light-emitting unit 300, a first electrode 313 disposed on the second insulating layer 310 and connected to the first ohmic metal layer 305, and a second electrode 317 disposed on one side of the substrate 301. In this embodiment, the second insulating layer 310, the first electrode 313, and the second electrode 317 extend into a plurality of second trenches 309. Furthermore, in this embodiment, because the width of the second trenches 309 is not limited by the manufacturing process, the width W0 of the second trenches 309 can be much larger than the width W of the second trenches 109 and 209. This significantly increases the roughened area between adjacent light-emitting units 300, further reducing the effective resistance.

[0110] In summary, the present invention provides a vertical-cavity surface-emitting laser and its manufacturing method. A first reflective layer, an active layer, a second reflective layer, and a first ohmic metal layer are sequentially formed on a substrate. An annular first trench is etched according to the position of the first ohmic metal layer to form a mesa structure. A current-limiting layer is formed within the second reflective layer to form light-emitting units. At least one second trench is formed between adjacent light-emitting units to create a roughened structure. A first electrode (metal layer) is deposited within the first and second trenches, between the first ohmic metal layer and the first trench, and between the first and second trenches, forming a first electrode with a large ramp area to reduce the voltage drop between adjacent light-emitting units, thereby improving the light intensity and current distribution. Finally, a shared second electrode is formed to create the vertical-cavity surface-emitting laser.

[0111] In the description of this specification, the references to terms such as "this embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0112] The embodiments of the present invention disclosed above are merely illustrative of the invention. The embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, It includes at least: Substrate; A first reflective layer is formed on the substrate; Multiple light-emitting units are formed on the first reflective layer and are arranged linearly; A first ohmic metal layer is formed on the light-emitting unit; A first groove is disposed around the light-emitting unit; At least one second trench is provided between each adjacent light-emitting unit; and A first electrode covers the sidewalls and bottom wall of the first trench and the second trench, and communicates with the first ohmic metal layer, the first trench, and the second trench; and The second electrode is connected to the substrate; The first trench and / or the second trench includes a first recess and a second recess, the second recess is located on the bottom wall of the first recess, and the etching depth of the second recess is greater than the etching depth of the first recess.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The depth of the first trench and / or the second trench remains at the first reflective layer or the substrate.

3. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first groove and the second groove are connected, and the second groove is arranged along the center line connecting two adjacent light-emitting units.

4. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first groove and the second groove are connected, and a plurality of the second grooves are arranged parallel to the center line connecting the two light-emitting units.

5. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, Multiple second grooves are arranged perpendicular to the center line connecting the two light-emitting units.

6. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, Multiple stepped structures are formed between the sidewalls and bottom walls of the first trench and / or the second trench.

7. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The light-emitting unit includes an active layer, a second reflective layer, and a current-limiting layer. The active layer is located on the first reflective layer, the second reflective layer is located on the active layer, and the current-limiting layer is disposed within the second reflective layer.

8. The vertical-cavity surface-emitting laser according to claim 7, characterized in that, The depth of the first recess remains at the first reflective layer, the active layer, or the second reflective layer.

9. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The height of the first electrode is higher than that of the light-emitting unit.

10. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first electrode includes a first metal layer and a second metal layer, wherein the second metal layer is disposed on the first metal layer.

11. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The roughened area of ​​the second trench is the difference between the cross-sectional area of ​​the first electrode after the second trench is set and the cross-sectional area of ​​the first electrode when the second trench is not set.

12. The vertical-cavity surface-emitting laser according to claim 11, characterized in that, The effect of roughening is evaluated using roughness ratio, where roughness ratio = roughened area / cross-sectional area of ​​the first electrode without roughening structure.

13. A method for manufacturing a vertical-cavity surface-emitting laser, characterized in that, It includes at least: Provide a substrate; A first reflective layer is formed on the substrate; Multiple light-emitting units are formed on the first reflective layer; A first ohmic metal layer is formed on the light-emitting unit; A first groove is formed on the outer side of each of the light-emitting units; At least one second trench is formed between each adjacent light-emitting unit; A first electrode is formed on the sidewall and bottom wall of the first trench and the second trench, and the first electrode connects the first ohmic metal layer, the first trench, and the second trench; and A second electrode is formed that is connected to the substrate; The first trench and / or the second trench includes a first recess and a second recess, the second recess is located on the bottom wall of the first recess, and the etching depth of the second recess is greater than the etching depth of the first recess.

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