CN117477347A - Vertical cavity surface emitting laser and manufacturing method thereof - Google Patents

Abstract

The invention discloses a vertical cavity surface emitting laser and a manufacturing method thereof, comprising the following steps: a substrate; at least one light emitting cell array disposed on the substrate, the light emitting cell array including a plurality of light emitting cells, the light emitting cells including a first reflective layer, an active layer, and a second reflective layer; grooves arranged between adjacent light emitting units and at two ends of the light emitting unit array; the first electrode comprises a first metal layer, a second metal layer and a third metal layer, the first metal layer is arranged on the light-emitting unit, the second metal layer is positioned in the groove, the second metal layer is connected with the first metal layer, and the third metal layer is arranged on the second metal layer and connected with the second metal layer; and a second electrode disposed at a side of the first reflective layer opposite to the light emitting unit. The vertical cavity surface emitting laser and the manufacturing method thereof can improve the light emitting uniformity of the vertical cavity surface emitting laser.

Description

Vertical cavity surface emitting laser and manufacturing method thereof

Technical Field

The invention relates to the technical field of lasers, in particular to a vertical cavity surface emitting laser and a manufacturing method thereof.

Background

The vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser, VCSEL) is a novel laser with light emitted from the vertical surface, has a plurality of advantages compared with the traditional edge emitting laser, has the advantages of small volume, round output light spots, single longitudinal mode output, small threshold current, low price, easy integration into a large-area array and the like, and is widely applied to the fields of optical communication, optical interconnection, optical storage and the like.

In some applications of LiDAR (Light Detection and Ranging, liDAR), the light source is one-dimensional, and the light emitting units are arranged in an array that is linearly arranged in one dimension. However, since the metal of the long side is long, the resistance cannot be completely ignored, so that in the arrangement of the long strips, the luminance of the light emitting unit near the bonding pad is large, and the luminance of the light emitting unit far from the bonding pad is small. And the time of the pulse signal is extremely short and is only a few nanoseconds, so that the skin effect causes that energy cannot be effectively transmitted to the light-emitting unit far away from the bonding pad, and the brightness of the light-emitting unit far away from the bonding pad is small. These factors all lead to non-uniformity of the light spot, which severely restricts the use of the device.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the present invention provides a vertical cavity surface emitting laser and a method for manufacturing the same, in which a plurality of layers of metals are disposed on a second reflective layer, so that the thickness of a metal electrode is increased, the resistance of the metal electrode is reduced, and the problem of non-uniform light emission of the vertical cavity surface emitting laser is solved.

In order to achieve the above object, the present invention provides a vertical cavity surface emitting laser comprising:

a substrate;

at least one light emitting cell array disposed on the substrate, the light emitting cell array including a plurality of light emitting cells, the light emitting cells including a first reflective layer, an active layer, and a second reflective layer;

grooves arranged between adjacent light emitting units and at two ends of the light emitting unit array, wherein the grooves expose the first reflecting layer;

the first electrode comprises a first metal layer, a second metal layer and a third metal layer, the first metal layer is arranged on the light-emitting unit, the second metal layer is positioned in the groove, the second metal layer is connected with the first metal layer, and the third metal layer is arranged on the second metal layer and connected with the second metal layer; and

and a second electrode disposed on a side of the first reflective layer opposite to the light emitting unit.

Further, a first insulating layer is further arranged in the groove, covers the bottom and the side wall of the groove, and extends to the second reflecting layer.

Further, the second metal layer covers the first insulating layer and the first metal layer, and the second metal layer is electrically connected with the first metal layer.

Further, a second insulating layer is disposed on the second metal layer, and the second insulating layer is provided with an opening exposing the second metal layer on the trench.

Further, the third metal layer covers the second insulating layer, and the second metal layer is connected through the opening on the second insulating layer.

Further, the thickness of the third metal layer is 0.5-5 μm.

Further, the first electrode comprises a fourth metal layer and a fifth metal layer, the fourth metal layer is located on the third metal layer, and the fifth metal layer is located on the fourth metal layer.

Further, an aspect ratio of each of the light emitting cell arrays is at least 3:1.

Further, the active layer comprises a quantum well composite structure which is arranged in a laminated mode, and the quantum well composite structure is formed by stacking gallium arsenide and aluminum gallium arsenide or indium gallium arsenide and aluminum gallium arsenide materials.

Furthermore, the invention also provides a manufacturing method of the vertical cavity surface emitting laser, which comprises the following steps of,

providing a substrate;

forming at least one light emitting unit array on the substrate, wherein the light emitting unit array comprises a first reflecting layer, an active layer and a second reflecting layer;

etching the second reflective layer and the active layer to form grooves, wherein the grooves are formed between adjacent light emitting units and at two ends of the light emitting unit array;

forming a first electrode on the light emitting unit, wherein the first electrode comprises a first metal layer, a second metal layer and a third metal layer, the first metal layer is arranged on the light emitting unit, the second metal layer is positioned in the groove, the second metal layer is connected with the first metal layer, and the third metal layer is arranged on the second metal layer and connected with the second metal layer;

the first reflective layer forms a second electrode with respect to one side of the light emitting unit.

The invention provides a vertical cavity surface emitting laser and a manufacturing method thereof, wherein the thickness of a metal electrode can be thickened by repeating an insulating layer and a metal layer on a second reflecting layer, the resistance of the electrode is reduced, and the phenomenon of uneven light emission of a light emitting unit far away from a bonding pad is solved. By thinning the substrate, the electrode is arranged on one side of the substrate opposite to the light-emitting unit and can be used as a common cathode, so that the electrode manufacturing flow is simplified. The invention can also arrange the transparent substrate on one side electrode of the light-emitting unit, remove the original substrate, support the back surface, needn't remove the transparent substrate again, bond the frequency is 1 time, also arrange the first electrode and second electrode on the same surface at the same time, thus avoid the wire bonding, save the process and easy to combine with other optical elements. Therefore, the vertical cavity surface emitting laser and the manufacturing method thereof provided by the invention simplify the preparation process, and adopt a plurality of layers of metal electrodes, thereby improving the light emitting uniformity of the vertical cavity surface emitting laser.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a flow chart of a method for manufacturing a vertical cavity surface emitting laser according to an embodiment.

Fig. 2 is a top view of a vertical cavity surface emitting laser according to an embodiment.

Fig. 3-4 are cross-sectional views of a vertical cavity surface emitting laser along A-A according to one embodiment of steps S11-S12.

Fig. 5 is a top view of a vertical cavity surface emitting laser according to an embodiment of steps S11 to S12.

Fig. 6 illustrates the formation of a passivation layer over the first metal layer and the epitaxial layer in the A-A direction.

Fig. 7 illustrates the formation of a passivation layer on the first metal layer and the epitaxial layer in the B-B direction.

FIG. 8 is a schematic diagram of a patterned photoresist along the A-A direction.

FIG. 9 is a schematic diagram of a patterned photoresist in the B-B direction.

Fig. 10 is a schematic view of a mesa structure formed in the A-A direction.

Fig. 11 is a schematic view of a mesa structure along the B-B direction.

FIG. 12 is a schematic view of the structure of the current confinement layer along the A-A direction.

FIG. 13 is a schematic view of the structure of the current confinement layer along B-B.

Fig. 14 is a schematic structural diagram of step S14 along A-A direction.

Fig. 15 is a schematic structural diagram of step S14 along the B-B direction.

Fig. 16 is a schematic structural diagram of step S15 along A-A direction.

FIG. 17 is a schematic view showing the structure of step S15 along the B-B direction

Fig. 18 and 20 are schematic structural diagrams of step S16 along A-A direction.

Fig. 19 and 21 are schematic structural diagrams of step S16 along the B-B direction.

Fig. 22 is a schematic structural diagram of step S17 along A-A direction.

Fig. 23 is a schematic diagram showing the structure of step S176 along the B-B direction.

Fig. 24 to 25 are cross-sectional views of another embodiment of a light emitting array along A-A and B-B directions.

Fig. 26 is a top view of a vertical cavity surface emitting laser according to an embodiment.

Fig. 27 is a top view of a vertical cavity surface emitting laser according to another embodiment.

Fig. 28 to 31 are schematic structural views of fig. 27 taken along the C-C section.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.

It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

In the present invention, it should be noted that, as terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., appear, the indicated orientation or positional relationship is based on that shown in the drawings, only for convenience of description and simplification of the description, and does not indicate or imply that the indicated apparatus or element must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, as used herein, are used for descriptive and distinguishing purposes only and are not to be construed as indicating or implying a relative importance.

As shown in fig. 1, the present embodiment proposes a method for manufacturing a vertical cavity surface emitting laser, including,

s11, providing a substrate.

S12, forming an epitaxial structure on the first surface of the substrate, wherein the epitaxial structure sequentially comprises a first reflecting layer, an active layer and a second reflecting layer, and a first metal layer is arranged on the second reflecting layer.

S13, forming a plurality of grooves in the epitaxial structure to divide the epitaxial structure into a plurality of light emitting units.

S14, forming a first insulating layer among the plurality of light emitting units.

S15, forming a plurality of second metal layers, wherein the second metal layers are connected with the first metal layers.

S16, forming a third metal layer on the second metal layer, wherein a second insulating layer is arranged between the third metal layer and the second metal layer, and the third metal layer is connected with the second metal layer through an opening on the second insulating layer.

S17, forming a second electrode on one side of the substrate opposite to the light-emitting unit.

As shown in fig. 2, in the present embodiment, a schematic top view structure of the vertical cavity surface emitting laser is proposed. The vertical cavity surface emitting laser comprises a plurality of light emitting arrays, wherein the light emitting arrays comprise a plurality of light emitting units which are linearly arranged. The plurality of light emitting units may be linearly arranged in a single column or may be linearly arranged in a plurality of columns. By designating the length of a single-column light-emitting array as a and the width of the light-emitting array as b, the aspect ratio of the light-emitting array, i.e., a/b, is, for example, at least 3:1, specifically, for example, 3:1 to 15:1, and preferably, for example, 5:1.

As shown in fig. 3 to 22, in the present embodiment, a process of manufacturing a vertical cavity surface emitting laser in A-A and B-B directions is proposed.

As shown in fig. 3 to 4, fig. 3 to 4 are cross-sectional views of a vertical cavity surface emitting laser along A-A according to an embodiment of steps S11 to S12. First, a substrate 101 is provided, and then an epitaxial structure 2 is formed on a first surface 101a of the substrate 101, the epitaxial structure 2 including a first reflective layer 102, an active layer 103, and a second reflective layer 104, the first reflective layer 102 being disposed on the substrate 101, the active layer 103 being disposed on the first reflective layer 102, the second reflective layer 104 being disposed on the active layer 103. In this embodiment, the substrate 101 may be any material suitable for forming a vertical cavity surface emitting laser, such as a gallium arsenide (GaAs) substrate. The substrate 101 may be an N-doped semiconductor substrate or a P-doped semiconductor substrate, and the doping may reduce the contact resistance of ohmic contact between the electrode formed later and the semiconductor substrate, and in this embodiment, the substrate 101 is an N-doped semiconductor substrate, for example.

As shown in fig. 3, in this embodiment, the first reflective layer 102 may include materials with two different refractive indexes, such as aluminum gallium arsenide (AlGaAs) and gallium arsenide (GaAs), or aluminum gallium arsenide (AlGaAs) with a high aluminum component and aluminum gallium arsenide (AlGaAs) with a low aluminum component, and the first reflective layer 102 may be an N-type mirror, and the first reflective layer 102 may be an N-type bragg mirror (N-Distributed Bragg Reflection, N-DBR). The active layer 103 includes a quantum well composite structure in which gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) are stacked, or indium gallium arsenide (InGaAs) and aluminum gallium arsenide (AlGaAs) materials are stacked, and the active layer 103 is configured to convert electric energy into optical energy. The second reflective layer 104 may be, for example, formed of aluminum gallium arsenide (AlGaAs) and gallium arsenide (GaAs), or a stack of two materials of different refractive indices, aluminum gallium arsenide (AlGaAs) of high aluminum composition and aluminum gallium arsenide (AlGaAs) of low aluminum composition, the second reflective layer 104 may be a P-type mirror, and the second reflective layer 104 may be a P-type bragg mirror (P-DBR). The first and second reflective layers 102 and 104 are used to reflect light generated from the active layer 103, and then emit from the surface of the second reflective layer 104.

As shown in fig. 3 to 5, fig. 5 is a top view of a vertical cavity surface emitting laser according to an embodiment in steps S11 to S12. In some embodiments, the first reflective layer 102, the active layer 103, and the second reflective layer 104 may be formed, for example, by a chemical vapor deposition method.

As shown in fig. 3-5, in some embodiments, the thicknesses of the first reflective layer 102, the active layer 103, and the second reflective layer 104 add up to 8-10 microns.

As shown in fig. 3-5, in some embodiments, the first reflective layer 102 or the second reflective layer 104 comprises a series of alternating layers of different refractive index materials, wherein the effective light thickness of each alternating layer (the layer thickness multiplied by the layer refractive index) is an odd integer multiple of the operating wavelength of the quarter-vcl, i.e., the effective light thickness of each alternating layer is an odd integer multiple of the operating wavelength of the vcl. However, in some embodiments, the first reflective layer 102 and the second reflective layer 104 can be formed of other materials.

As shown in fig. 3-5, in some embodiments, the active layer 103 may include one or more semiconductor layers including one or more quantum well layers or one or more quantum dot layers sandwiched between respective pairs of barrier layers.

As shown in fig. 4 to 7, wherein fig. 6 is a view of forming a passivation layer on the first metal layer and the epitaxial layer in the A-A direction. Fig. 7 illustrates the formation of a passivation layer on the first metal layer and the epitaxial layer in the B-B direction. A first metal layer 105a is further formed on the second reflecting layer 104, where the first metal layer 105a can be used as a reference for photolithography calibration in a subsequent process, so as to prepare a vertical cavity surface emitting laser with higher precision, and the first metal layer 105a can also be used as a metal contact pad of a subsequent metal electrode. The first metal layer 105a is, for example, P-type ohmic metal, and the material of the first metal layer 105a may include one or a combination of Au metal, ag metal, pt metal, ti metal and Ni metal, which may be specifically selected according to needs. In some embodiments, the surface of the second reflective layer 104 contacting the first metal layer 105a has a higher concentration of doping to form an ohmic contact layer, so as to reduce the contact resistance of ohmic contact between the first metal layer 105a and the second reflective layer 104, wherein the ohmic contact layer may be a P-type doped ohmic contact layer.

As shown in fig. 5, in the present embodiment, the shape of the first metal layer 105a may be, for example, a circular ring, and in some embodiments, the shape of the first metal layer 105a may also be an elliptical ring, a rectangular ring, a hexagonal ring, and the shape of the first metal layer 105a may be selected as required. In this embodiment, the inner diameter of the first metal layer 105a is, for example, 5 to 97um, and the outer diameter of the first metal layer 105a is, for example, 7 to 99um, and in some embodiments, the inner diameter and the outer diameter of the first metal layer 105a are not limited and may be selected as needed.

As shown in fig. 6 to 9, fig. 8 is a schematic diagram of a patterned photoresist along A-A direction, and fig. 9 is a schematic diagram of a patterned photoresist along B-B direction. In step S13, after the first metal layer 105a is formed, a passivation layer 106 may be further deposited on the epitaxial layer 2 and the first metal layer 105a, so as to further protect the epitaxial layer 2 and the first metal layer 105a5. Then, a patterned photoresist layer 1071 is formed on the passivation layer 106, the patterned photoresist layer 1071 covers the first metal layer 105a, and a portion of the passivation layer 106 is exposed by the patterned photoresist layer 109, and then the second reflective layer 104 is etched downward according to the patterned photoresist layer 1071 to form a plurality of trenches. A plurality of light emitting units may be formed on one substrate 101, and the plurality of light emitting units are linearly arranged in one dimension to form a light emitting array. The arrow direction in fig. 8 and 9 indicates the etching direction.

As shown in fig. 10-11, wherein fig. 10 is a schematic view of a mesa structure formed in the A-A direction. Fig. 11 is a schematic view showing a mesa structure formed along the B-B direction. In this embodiment, etching is performed downward from the passivation layer 106 by an etching process to form a plurality of trenches 107. The trench 107 is etched to the first reflective layer 102, and the trench 107 exposes the first reflective layer 102, i.e., the trench 107 etches the passivation layer 106, the second reflective layer 104, and the active layer 103 sequentially from top to bottom, thus dividing the active region into a plurality of portions. The trench 107 etches the passivation layer 106, the second reflective layer 104, and the active layer 103 sequentially from top to bottom, i.e., the trench 107 is exposed to the surface of the first reflective layer 102, or the trench 107 etches a portion of the first reflective layer 102. The trench 107 is used to isolate the light emitting cells from the light emitting cells, and from the ends of the light emitting cells and the light emitting array.

As shown in fig. 10, a plurality of mesa structures, for example, a first mesa structure 109a, a second mesa structure 109b, a third mesa structure 110a, and a fourth mesa structure 110b, are formed on the substrate 101 through the trench 107. The first mesa structure 109a, the second mesa structure 109b, the third mesa structure 110a and the fourth mesa structure 110b are used to form a light emitting cell, respectively.

As shown in fig. 2, 10 and 11, in the present embodiment, mesa structures are formed at both ends of the substrate 101, wherein the mesa structure at one end includes a fourth mesa structure 110b and a fifth mesa structure 116, a support structure 115 is disposed between the two mesa structures, and the support structure 115 and the mesa structure pass through the trench 107 to separate adjacent light emitting cells and ensure uniformity of the post electrode height. In other embodiments, adjacent mesa structures may also be isolated directly by trench 107 without support structure 115.

As shown in fig. 10 and 11, in some embodiments, the plurality of trenches may be formed, for example, by dry etching.

As shown in fig. 12 and 13, in the present embodiment, after forming the plurality of trenches, it is also necessary to form the current confinement layer 108 in the mesa structure to form the light emitting hole. Fig. 12 is a schematic view of a current confinement layer structure along A-A, and fig. 13 is a schematic view of a current confinement layer structure along B-B. In this embodiment, the sidewalls of the trench 107 are oxidized by high-temperature oxidation to form a plurality of current confinement layers 108 in the second reflective layer 104. In the present embodiment, the plurality of current confinement layers 108 are formed in the second reflective layer 104 by oxidizing the sidewalls of the trench 107.

As shown in fig. 12 and 13, in some embodiments, the current confinement layer 108 includes one of an air pillar type current confinement structure, an ion implantation type current confinement structure, a buried heterojunction type current confinement structure, and an oxidation confinement type current confinement structure, which is employed in the present embodiment.

As shown in fig. 14 to 15, fig. 14 is a schematic structural diagram of step S14 along A-A direction. Fig. 15 is a schematic structural diagram of step S14 along the B-B direction. In this embodiment, after the current confinement layer 108 is formed, the first insulating layer 111 is formed in the trench. In this embodiment, the first insulating layer 111 is formed on the passivation layer 106 at the bottom and on the sidewalls of the trench, and after the first insulating layer is formed, the first insulating layer 111 and the passivation layer 106 on the first metal layer 105a are removed by etching, exposing the first metal layer 105a. I.e. part of the first insulating layer 111 is located within the trench 107 and on the passivation layer 106 in areas of the mesa structure other than on the first metal layer 105a. In this embodiment, the first insulating layer 111 in the trench 107 is taken as an example, and part of the first insulating layer 111 is located on the bottom and the sidewall in the trench 107, and the first insulating layer 111 extends onto the second reflective layer 104 along the sidewall of the trench 107 and contacts the passivation layer 106. Similarly, the first insulating layer 111 within the trench 107 extends from the sidewall of the trench 107 onto the second reflective layer 104 and contacts the passivation layer 106a, thereby achieving insulating isolation of the light emitting cell. In this embodiment, a portion of the first insulating layer 111 also covers the passivation layer 106 on the support structure 115.

As shown in fig. 13 to 15, the material of the first insulating layer 111 may be silicon nitride or silicon oxide or other insulating materials, and the thickness of the first insulating layer 111 may be 100-300 nm, where the first insulating layer 111 may protect the current confinement layer 108 and may effectively isolate adjacent mesa structures. In this embodiment, the first insulating layer 111 may be formed, for example, by chemical vapor deposition.

As shown in fig. 14 to 17, fig. 16 is a schematic structural view of step S15 along A-A direction, and fig. 17 is a schematic structural view of step S15 along B-B direction. First, the second metal layer 105b is formed in the first trench 107a, the second trench 107b, and the third trench 107c, so as to realize that the second metal layer 105b is connected to the first metal layer 105a.

As shown in fig. 16 to 17, in the present embodiment, the second metal layer 105b is formed on the first insulating layer 111, that is, a part of the second metal layer 105b is located on the first insulating layer 111 in the trench 107, a part of the second metal layer 105b is located on the first insulating layer 111 on the second reflective layer 104, and a part of the second metal layer 105b is also located on the passivation layer 106 and the first metal layer 105a and is electrically connected to the first metal layer 105a. The sidewalls of the second metal layer 105b are aligned with the sidewalls of the first metal layer 105a, i.e. the second metal layer 105b does not cover or block the light emitting holes, i.e. is located at the outer periphery of the light emitting holes. In this embodiment, a portion of the second metal layer 105b also covers the first insulating layer 111 on the support structure 115.

As shown in fig. 16, in the present embodiment, the first mesa structure 109a is defined as a first light emitting unit, and the second mesa structure 109b is defined as a second light emitting unit. The first mesa structure 109a has the same structure as the second mesa structure 109b, and the first mesa structure 109a is taken as an example for explanation in this embodiment. The first mesa structure 109a includes, from bottom to top, the first reflective layer 102, the active layer 103, the second reflective layer 104, the first metal layer 105a, the passivation layer 106, and the second metal layer 105b, and a current confinement layer 108 is formed in the second reflective layer 104, that is, the current confinement layer 108 extends from a sidewall of the second reflective layer 104 into the second reflective layer 104. And the current confinement layer 108 in the first mesa structure 109a has a ring structure, and the light emitting hole is defined by the current confinement layer 108. Wherein, the first end of the current confinement layer 108 contacts with the sidewall of the second reflective layer 104, and the other end is located in the second reflective layer 104 and extends into the inner diameter of the first metal layer 105a, that is, the first metal layer 105a is located at the periphery of the light emitting hole, so that the electrode formed later does not block the light emitting hole.

As shown in fig. 16, in the present embodiment, the first mesa structure 109a and the second mesa structure 109b have the same structure, and thus the first light emitting unit and the second light emitting unit have the same structure. In the present embodiment, the third mesa structure 110a is defined as a third light emitting unit, the fourth mesa structure 110b is defined as a fourth light emitting unit, and the third mesa structure 110a and the fourth mesa structure 110b have the same structure, thereby defining the first light emitting unit, the second light emitting unit, the third light emitting unit, and the fourth light emitting unit as a part of the light emitting array.

As shown in fig. 16, in the present embodiment, a trench 107 is formed between a first mesa structure 109a and a second mesa structure 109b, and a second metal layer 105b is formed in the trench 107, and the second metal layer 105b connects the first mesa structure 109a and the first metal layer 105b on the second mesa structure 109b, thereby connecting the first mesa structure 109a and the second mesa structure 109b, that is, the first mesa structure 109a and the second mesa structure 109b are connected to the first metal layer 105a through the second metal layer 105b, that is, the first light emitting unit and the second light emitting unit. Similarly, the third light emitting unit is connected to the second light emitting unit, and the fourth light emitting unit is connected to the third light emitting unit. In actual production, in a single light emitting array, a plurality of light emitting cells are provided, the plurality of light emitting cells are identical in structure, and the plurality of light emitting cells are connected in series through the second metal layer 105b in the trench 107.

As shown in fig. 13 and 17, in the present embodiment, the fourth mesa structure 110b and the fifth mesa structure 116 are identical in structure to the first mesa structure 109a, and the current confinement layer 108 is formed in the same manner and structure, which will not be described here. A second metal layer 105b is formed in the trench 107, and the second metal layer 105b connects the fourth mesa structure 110b and the first metal layer 105a on the fifth mesa structure 116 to form two light emitting cells including a fourth light emitting cell and a fifth light emitting cell. And the second metal layer 105b covers the two trenches 107 and is connected, so the two light emitting cells are connected with the first metal layer 105a through the second metal layer 105b.

As shown in fig. 18 to 21, fig. 18 and 20 are schematic structural views of step S16 along A-A direction, and fig. 19 and 21 are schematic structural views of step S16 along B-B direction. In this embodiment, in step S16, the second insulating layer 112 is formed on the second metal layer 105b, part of the second insulating layer 112 is located on the second metal layer 105b, and part of the second insulating layer 112 is located on the passivation layer 106 and the first insulating layer 111, i.e. covers the light emitting hole and the side surface of the second metal layer 105b. And no second insulating layer 112 is disposed on the second metal layer 105b above the trench 107, i.e. when the second insulating layer 112 is formed, the second insulating layer 112 covers the entire surface layer of the substrate 101, and then an etching process is added to etch away the second insulating layer 112 on the second metal layer 105b above the trench 107, so as to expose a portion of the second metal layer 105b, so that the subsequent metal layer is connected to the second metal layer 105b. In the present embodiment, the total optical thickness of the second insulating layer 112, the first insulating layer 111 and the passivation layer 106 satisfies an integer multiple of half wavelength, that is, the thickness of the second insulating layer 112 multiplied by the refractive index of the second insulating layer 112, plus the thickness of the first insulating layer 111 multiplied by the refractive index of the first insulating layer 111, plus the thickness of the passivation layer 106 multiplied by the sum of the refractive indexes thereof satisfies an integer multiple of half wavelength.

As shown in fig. 19, in the present embodiment, when part of the second insulating layer 112 is etched and removed, the second insulating layer 112 on the second metal layer 105b above the support structure 115, and the second insulating layers 112 on the second metal layers 105b at both ends of the fourth mesa structure 110b and the fifth mesa structure 116 are removed at the same time, that is, the second insulating layers 112 are not disposed on the support structure 115 and the second metal layers 105b at both ends of the mesa structure, so that the subsequent metal layers are connected to the second metal layers 105b.

As shown in fig. 18 to 19, the material of the second insulating layer 112 may be silicon nitride or silicon oxide or other insulating materials, and the thickness of the second insulating layer 112 is, for example, 100-300 nm, and the second insulating layer 112 may protect the second metal layer 105b and may effectively isolate the adjacent mesa structures. In this embodiment, the second insulating layer 112 is formed, for example, by chemical vapor deposition.

As shown in fig. 20 to 21, in step S16, first, a third metal layer 105c is formed on the second insulating layer 112 and the second metal layer 105b, and the third metal layer 105c is connected to the second metal layer 105b. And the third metal layer 105c, the second metal layer 105b, and the first metal layer 105a are electrically connected to form the first electrode 105. In different embodiments, the first electrode 105 may further include a fourth metal layer, a fifth metal layer, and the like, where the fourth metal layer is disposed on the third metal layer 105c, and the fifth metal layer is disposed on the fourth metal layer, that is, the insulating layer and the metal layer are continuously fabricated on the third metal layer 105c, and the insulating layer is provided with openings to ensure electrical connection between the metal layers to form the first electrode, so as to increase the thickness of the first electrode 105. The plurality of first electrodes 105 connect the plurality of light emitting cells to form a common anode. In the present invention, the boundary shape of the top view of the third metal layer 105c is not limited, and may be, for example, an arc shape, a polygon shape, or the like, and specifically, for example, a circular shape, a rectangular shape, a triangular shape, or the like is preferable so as not to block the light emitting hole. In the present embodiment, the third metal layer 105c is provided in an arc shape to match the outer diameter of the light emitting hole, and the thickness of the third metal layer 105c is, for example, 0.5 to 5 μm, specifically, for example, 4 μm. The material of the third metal layer 105c may include Au metal, cu metal, or the like, and specifically, a metal or a combination of metals having a small specific resistance may be selected as needed. The third metal layer 105c is connected with the second metal layer 105b, so that the thickness of the metal electrode is increased, the light spot non-uniformity caused by overlong long sides of the linear light emitting units is reduced, and the light spot uniformity is improved. The invention does not limit the number of metal layers on the light-emitting unit, and in actual production, a plurality of metal layers can be arranged according to the needs, so that the light-emitting holes are not blocked by the metal layers. The metal layers are separated by insulating layers, and openings are arranged on the insulating layers at the same time so as to connect the metal layers to form the first electrode.

As shown in fig. 22 and 23, fig. 22 is a schematic structural view of step S17 along A-A. Fig. 23 is a schematic diagram showing the structure of step S176 along the B-B direction. In an embodiment of the present invention, the substrate 101 may be thinned, and the thickness of the thinned substrate 101 is, for example, 2 to 150 μm, specifically, for example, 100 μm. The second electrode 114 is formed at a side of the thinned substrate 101 opposite to the light emitting unit. The material of the second electrode 114 may include one or a combination of Au metal, ag metal, pt metal, ti metal and Ni metal, and may be specifically selected according to needs. Since the substrate 101 is made of a semiconductor material, a plurality of light emitting cells may be connected through the second electrode 114, and the second electrode 114 serves as a common cathode.

As shown in fig. 24 and 25, wherein fig. 24 to 25 are cross-sectional views of a light emitting array along A-A and B-B directions in another embodiment. In another embodiment of the present invention, when forming the trench 107, the substrate 101 is exposed through the epitaxial structure 2 or etched again to form the first mesa structure 109a, the second mesa structure 109b, the third mesa structure 110a, the fourth mesa structure 110b, and the fifth mesa structure 116. Wherein, a first metal layer 105a and a second metal layer 105b are formed on each mesa structure, and the first metal layer 105a and the second metal layer 105b are connected through an opening on the first insulating layer 111 to form the first electrode 105. A second electrode 114 is formed on a side of the substrate 101 opposite to the light emitting unit. In this embodiment, etching the trench 107 to the substrate 101 increases the resistance of the N-DBR, thereby increasing the equivalent resistance of the light emitting unit. Meanwhile, as the depth of the groove is increased, the filling volume of the metal can be increased when the second metal layer is formed, so that the equivalent resistance of the metal is reduced. When the vertical cavity surface emitting laser works, the partial pressure of the one-dimensional array light emitting unit device is increased, and the resistance of the metal transmission line is reduced, so that the difference of injection currents of the head light emitting unit and the tail light emitting unit of the one-dimensional linear array is reduced, and the light emitting uniformity of the light emitting units is improved.

As shown in fig. 2, in the present embodiment, the prepared vertical cavity surface emitting laser is soldered to the bonding pad 1, and the number of the light emitting units 113 in the single light emitting unit array is not limited, for example, 6 to 15, specifically, for example, 11, that is, a plurality of light emitting units constitute the light emitting array. In this embodiment, the number of columns of the light emitting arrays of the vcsels is not limited, and in the process of preparing the light emitting units 113, a plurality of light emitting arrays may be prepared at the same time, for example, 1 to 6 columns, specifically, for example, 2 columns may be set to satisfy different usage scenarios.

As shown in fig. 26, in another embodiment of the present invention, the number of columns of the vertical cavity surface emitting lasers is 1, and for example, 6 light emitting units 113 are provided, and the manufacturing method of the light emitting units is consistent with that of the present embodiment. The boundary shape of the top view of the third metal layer 105c between the light emitting cells 113 may be provided in various shapes, for example, arc, polygon, etc., as appropriate so as not to block the light emitting holes.

As shown in fig. 27, in another embodiment of the present invention, the number of columns of the provided vcsels is, for example, 2-4 columns, and is, for example, 2 columns, and two sets of circuits are disposed in the vcsels, and pads are respectively disposed at two ends of the vcsels, so that the light emitting arrays in the lasers can be controlled by a single pad, so as to implement light emission control on different light emitting arrays.

As shown in fig. 28 to 31, the preparation process of the two-column vertical cavity surface emitting lasers of the two sets of circuits along the C-C direction is shown.

As shown in fig. 28, the preparation method of the second metal layer 105b is identical to the preparation method of fig. 3 to 16 before the preparation is completed, which is not described herein. After the first insulating layer 111 is formed, a second metal layer 105b is formed, a portion of the second metal layer 105b is located on the first insulating layer 111 in the trench 107, a portion of the second metal layer 105b is located on the first insulating layer 111 on the second reflective layer 104, and a portion of the second metal layer 105b is also located on the passivation layer 106 and the first metal layer 105a and is electrically connected to the first metal layer 105a. The sidewalls of the second metal layer 105b are aligned with the sidewalls of the first metal layer 105a, i.e. the second metal layer 105b does not cover or block the light emitting holes, i.e. is located at the outer periphery of the light emitting holes. In this embodiment, the second metal layer 105b does not cover the support structure 115.

As shown in fig. 29, in the present embodiment, a second insulating layer 112 is formed on the second metal layer 105b, and the second insulating layer 112 covers the entire upper surface of the substrate 101. The material of the second insulating layer 112 may be silicon nitride or silicon oxide or other insulating materials, and the thickness of the second insulating layer 112 may be 100-300 nm, and the second insulating layer 112 may protect the second metal layer 105b. In this embodiment, the second insulating layer 112 may be formed, for example, by chemical vapor deposition.

As shown in fig. 30, in this embodiment, after the second insulating layer 112 is formed, a patterned photoresist layer (not shown) is formed on the second insulating layer 112, and the second insulating layer 112 is etched to form a plurality of openings. The etched portion of the second insulating layer 112 covers the light emitting hole and the side surface of the second metal layer 105b, and extends to the portion of the second metal layer 105b, and the portion of the second insulating layer 112 covers the supporting structure 115. I.e. on the part of the second metal layer 105b on the light emitting unit, the second insulating layer 112 is not provided for connection of the subsequent metal layer to the second metal layer 105b.

As shown in fig. 27 and 31, in the present embodiment, after the etching of the second insulating layer 112 is completed, a third metal layer is deposited on the second metal layer 105b. Wherein the third metal layer on the fourth mesa structure 110b is defined as a first portion of the metal layer 117 and the metal layer on the fifth mesa structure 116 is defined as a second portion of the metal layer 118. That is, a part of the first partial metal layer 117 is located on the second metal layer 105b and the second insulating layer 112 at one end of the fourth mesa structure 110b, and a part of the first partial metal layer 117 is located on a part of the fourth mesa structure 110b and the supporting unit 115. The second part of the metal layer 118 is located on the fifth mesa structure 116, and is located on the second metal layers 105b on both sides of the light emitting hole, and is connected to the second metal layers 105b on the fifth mesa structure 116. In this embodiment, the upper surfaces of the first part metal layer 117 and the second part metal layer 118 are flush, and the first part metal layer 117 and the second part metal layer 118 are on the support structure 115, and are insulated by a part of the second insulating layer 112. In the present embodiment, the light emission of a row of light emitting units can be controlled from one end by connecting the first partial metal layer 117 with the first pad 3. The second partial metal layer 118 is connected to the second pad 4 and can be used to control the light emission of a row of light emitting cells from the other end. I.e. a plurality of pads are provided, enabling control of a column of light emitting arrays in a laser by a single pad.

As shown in fig. 31, in the present embodiment, the shapes of the first part metal layer 117 and the second part metal layer 118 are not limited, for example, the boundary between the top views of the first part metal layer 117 and the second part metal layer 118 may be arc-shaped, polygonal, or the like, and specifically, for example, circular, rectangular, or triangular, or the like, so that the light emitting hole is preferably not blocked. In the present embodiment, the first partial metal layer 117 and the second partial metal layer 118 are provided in an arc shape to match the outer diameter of the light emitting hole, and the thicknesses of the first partial metal layer 117 and the second partial metal layer 118 are, for example, 1 to 8 μm, specifically, 2 μm. The materials of the first partial metal layer 117 and the second partial metal layer 118 may include Au metal or Cu metal, etc., and may be specifically selected as needed. By arranging the first part metal layer 117 and the second part metal layer 118, on one hand, the thickness of the metal electrode can be increased, the uneven light spots caused by overlong long sides of the light emitting units can be reduced, and the uniformity of the light spots can be improved. On the other hand, different circuits can be arranged and connected, and the vertical cavity surface emitting laser can be controlled through the different circuits, so that the luminous efficiency is improved.

The preferred embodiments of the invention disclosed above are intended only to assist in the explanation of the invention. The preferred embodiments are not exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best understand and utilize the invention. The invention is limited only by the claims and the full scope and equivalents thereof.

Claims (10)

1. A vertical cavity surface emitting laser is characterized by comprising,

a substrate;

at least one light emitting cell array disposed on the substrate, the light emitting cell array including a plurality of light emitting cells, the light emitting cells including a first reflective layer, an active layer, and a second reflective layer;

grooves arranged between adjacent light emitting units and at two ends of the light emitting unit array, wherein the grooves expose the first reflecting layer;

the first electrode comprises a first metal layer, a second metal layer and a third metal layer, the first metal layer is arranged on the light-emitting unit, the second metal layer is positioned in the groove, the second metal layer is connected with the first metal layer, and the third metal layer is arranged on the second metal layer and connected with the second metal layer; and

and a second electrode disposed on a side of the first reflective layer opposite to the light emitting unit.

2. The vcl as defined in claim 1, wherein a first insulating layer is further disposed within the trench, the first insulating layer covering the bottom and sidewalls of the trench and extending onto the second reflective layer.

3. The vcl laser of claim 2, wherein the second metal layer covers the first insulating layer and the first metal layer, and the second metal layer is electrically connected to the first metal layer.

4. A vertical cavity surface emitting laser according to claim 3, wherein a second insulating layer is provided on said second metal layer, and said second insulating layer is provided with an opening exposing said second metal layer on said trench.

5. The vcl laser of claim 4, wherein the third metal layer covers the second insulating layer and is connected to the second metal layer through the opening in the second insulating layer.

6. The vcl laser of claim 5, wherein the third metal layer has a thickness of 0.5-5 μm.

7. The vcl laser of claim 1, wherein the first electrode includes a fourth metal layer and a fifth metal layer, the fourth metal layer being on the third metal layer, the fifth metal layer being on the fourth metal layer.

8. The vcl laser of claim 1, wherein each of the arrays of light emitting cells has an aspect ratio of at least 3:1.

9. The vcsels of claim 1, wherein the active layer comprises a stacked quantum well composite structure of gallium arsenide and aluminum gallium arsenide, or indium gallium arsenide and aluminum gallium arsenide materials in a stacked arrangement.

10. A method for manufacturing a vertical cavity surface emitting laser is characterized by comprising the steps of,

providing a substrate;

forming at least one light emitting unit array on the substrate, wherein the light emitting unit array comprises a first reflecting layer, an active layer and a second reflecting layer;

etching the second reflective layer and the active layer to form grooves, wherein the grooves are formed between adjacent light emitting units and at two ends of the light emitting unit array;

forming a first electrode on the light emitting unit, wherein the first electrode comprises a first metal layer, a second metal layer and a third metal layer, the first metal layer is arranged on the light emitting unit, the second metal layer is positioned in the groove, the second metal layer is connected with the first metal layer, and the third metal layer is arranged on the second metal layer and connected with the second metal layer;

the first reflective layer forms a second electrode with respect to one side of the light emitting unit.