CN111181001B

CN111181001B - Vertical cavity surface emitting laser and manufacturing method and application thereof

Info

Publication number: CN111181001B
Application number: CN202010143691.6A
Authority: CN
Inventors: 张�成; 梁栋; 刘嵩; 赵励
Original assignee: Vertilite Co Ltd
Current assignee: Vertilite Co Ltd
Priority date: 2020-03-04
Filing date: 2020-03-04
Publication date: 2021-06-29
Anticipated expiration: 2040-03-04
Also published as: CN111181001A

Abstract

The invention provides a vertical cavity surface emitting laser and a manufacturing method and application thereof, comprising a substrate; a first reflective layer formed on a first surface of the substrate; at least two light emitting units formed on the first reflective layer, each of the light emitting units including at least two light emitting sub-units; an insulating layer formed between the at least two light emitting cells; at least two second electrodes formed on the at least two light emitting units, wherein the light emitting sub-units in each light emitting unit are connected through the second electrodes; a first electrode formed on a second surface of the substrate; wherein each of the light emitting sub-units includes a light emitting hole, and the second electrode surrounds the light emitting hole. The vertical cavity surface emitting laser provided by the invention has high application frequency.

Description

Vertical cavity surface emitting laser and manufacturing method and application thereof

Technical Field

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

Background

Vertical Cavity Surface Emitting Lasers (VCSELs) are developed on the basis of gallium arsenide semiconductor materials, are different from other light sources such as LEDs (light Emitting diodes) and LDs (Laser diodes), have the advantages of small volume, circular output light spots, single longitudinal mode output, small threshold current, low price, easy integration into large-area arrays and the like, and are widely applied to the fields of optical communication, optical interconnection, optical storage and the like.

In the field of optical fiber communication, the VCSEL market is currently developed unprecedentedly, and high-price LD is replaced in north america for the construction of gigabit ethernet data communication networks, resulting in an explosive increase in the demand for high-speed VCSEL transceiver modules. VCSELs also have good application prospects in other aspects. In optical printing, the electronization of optical scanning technology such as polygon mirrors in laser printers is an unsolved problem for many years, and has been improved with the development of technology.

The traditional VCSEL adopts a common cathode mode, so that a driving system cannot select an N-MOS driver with smaller volume and higher speed, and the factors seriously restrict the high-frequency and high-speed 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 manufacturing method and application thereof, so as to reduce the area of a light emitting unit, and simultaneously, select an N-MOS driver with smaller volume and faster speed, thereby increasing the application frequency of the device.

To achieve the above and other objects, the present invention provides a vertical cavity surface emitting laser including,

a substrate;

a first reflective layer formed on a first surface of the substrate;

at least two light emitting units formed on the first reflective layer, each of the light emitting units including at least two light emitting sub-units;

an insulating layer formed between the at least two light emitting cells;

at least two second electrodes formed on the at least two light emitting units, wherein the light emitting sub-units in each light emitting unit are connected through the second electrodes;

a first electrode formed on a second surface of the substrate;

wherein each of the light emitting sub-units includes a light emitting hole, and the second electrode surrounds the light emitting hole.

Further, each of the light emitting sub-units includes an active layer formed on the first reflective layer and a second reflective layer formed on the active layer.

Further, a first groove is formed between the plurality of light emitting cells, and the first groove is exposed to the first reflective layer.

Further, a portion of the insulating layer is formed within the first trench.

Furthermore, a second groove is formed in each light-emitting subunit, penetrates through the second reflecting layer and the active layer and is exposed to the first reflecting layer.

Further, a portion of the second electrode is formed in the second trench and extends to the plurality of light emitting sub-units on two sides along the second trench.

Further, part of the second electrode covers the insulating layer and is connected with the second reflecting layer.

Further, the first electrode and the second electrode are located on opposite sides of the substrate.

Further, the present invention provides a method for manufacturing a vertical cavity surface emitting laser, comprising,

providing a substrate;

forming a first reflective layer on a first surface of the substrate;

forming at least two light emitting units on the first reflective layer, each light emitting unit including at least two light emitting sub-units;

forming an insulating layer between the at least two light emitting units;

forming at least two second electrodes on the at least two light-emitting units, wherein the light-emitting subunits in each light-emitting unit are connected through the second electrodes;

forming a first electrode on a second surface of the substrate;

Further, the present invention provides a light emitting device, comprising,

a substrate;

a light emitting element disposed on the substrate, the light emitting element including at least one vertical cavity surface emitting laser, wherein the at least one vertical cavity surface emitting laser includes,

a substrate;

a first reflective layer formed on a first surface of the substrate;

an insulating layer formed between the at least two light emitting cells;

a first electrode formed on a second surface of the substrate;

In summary, the present invention provides a vertical cavity surface emitting laser and a method for manufacturing the same, in which a first electrode is in contact with a first reflective layer to form a common electrode, i.e. to form a common anode, and a plurality of second electrodes are formed on a plurality of light emitting units to form a cathode-separated structure, so that the chip area of the light emitting units can be reduced, and the vertical cavity surface emitting laser can select an N-MOS driver with a smaller volume and a faster speed, thereby improving the application efficiency of the device.

Drawings

FIG. 1: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 2: the steps S1-S2 are schematic structural diagrams.

FIG. 3: fig. 2 is a top view.

FIGS. 4 to 6: the structure of step S3.

FIG. 7: the structure of step S4.

FIG. 8: the steps S5-S6 are schematic structural diagrams.

FIG. 9: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 10: the steps S11-S12 are schematic structural diagrams.

FIGS. 11 to 13: the structure of step S13.

FIG. 14: the structure of step S14.

FIG. 15: the steps S15-S16 are schematic structural diagrams.

FIG. 16: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 17: the structure of step S21.

FIG. 18: the structure of step S22.

FIGS. 19 to 21: the structure of step S23.

FIG. 22: the structure of step S24.

FIG. 23: the steps S25-S26 are schematic structural diagrams.

FIG. 24: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 25: the structure of step S31.

FIGS. 26-28: the structure of step S32.

FIGS. 29 to 30: the structure of step S33.

FIGS. 31-33: the structure of steps S34-35.

FIG. 34: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 35: the steps S41-S42 are schematic structural diagrams.

FIGS. 36-37: the steps S43-S44 are schematic structural diagrams.

FIGS. 38-39: the structure of step S45.

FIGS. 40-41: the steps S46-S47 are schematic structural diagrams.

FIG. 42: another structure of the vertical cavity surface emitting laser.

FIG. 43: fig. 42 is a bottom view.

FIG. 44: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 45: the structure of step S51.

FIG. 46: the structure of step S52.

FIGS. 47-49: the structure of step S53.

FIG. 50: the structure of step S54.

FIG. 51: the steps S55-S56 are schematic structural diagrams.

FIG. 52: a flowchart of a method for fabricating a vertical cavity surface emitting laser is provided in this embodiment.

FIG. 53: the structure of step S61.

FIG. 54: the structure of step S62.

FIGS. 55-57: the structure of step S63.

FIG. 58: the steps S64-S66 are schematic structural diagrams.

FIG. 59: a schematic diagram of the light emitting device in this embodiment.

FIG. 60: the schematic diagram of the three-dimensional sensing device in this embodiment is shown.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

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

s1: providing a substrate;

s2: forming a first reflective layer on the substrate;

s3: forming at least two light-emitting units on the first reflecting layer, wherein each light-emitting unit comprises at least two light-emitting subunits, and each light-emitting subunit comprises a light-emitting hole;

s4: forming an insulating layer between the at least two light emitting units;

s5: forming at least one first electrode, the first electrode contacting the first reflective layer, forming a common anode;

s6: and forming at least two second electrodes on the at least two light-emitting units, wherein at least two light-emitting sub-units in each light-emitting unit are connected through the second electrodes, and the second electrodes surround the periphery of the light-emitting holes.

As shown in fig. 2, in steps S1-S3, a substrate 101 is provided, 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 the present embodiment, the substrate 101 may be any semi-insulating material suitable for forming a vertical cavity surface emitting laser, and the substrate 101 is, for example, a semi-insulating GaAs substrate which is a GaAs substrate not doped with impurities and has a very high resistance. The semi-insulating GaAs substrate has a resistivity of 10⁷Omega cm or more. In some embodiments, a conductive substrate or an insulating substrate may also be used instead of the semi-insulating substrate. In this case, the laser array may be formed on a GaAs substrate, separated from the GaAs substrate, and then attached to a substrate having high thermal conductivity, such as an insulating AlN substrate or a conductive Cu substrate.

As shown in fig. 2, in the present embodiment, the first reflective layer 102 may be formed by stacking two materials having different refractive indexes, including AlGaAs and GaAs, or AlGaAs with a high aluminum composition and AlGaAs with a low aluminum composition, for example, the first reflective layer 102 may be a P-type mirror, and the first reflective layer 102 may be a P-type bragg mirror. The active layer 103 includes a quantum well composite structure formed by stacking GaAs and AlGaAs, or InGaAs and AlGaAs materials, and the active layer 103 converts electric energy into optical energy. The second reflective layer 104 may include a stack of two materials having different refractive indexes, i.e., AlGaAs and GaAs, or AlGaAs of a high aluminum composition and AlGaAs of a low aluminum composition, the second reflective layer 104 may be an N-type mirror, and the second reflective layer 104 may be an N-type bragg mirror. The first reflective layer 102 and the second reflective layer 104 are used for reflection enhancement of light generated by the active layer 103 and then emitted from the surface of the second reflective layer 104.

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.

In some embodiments, the sum of the thicknesses of the first reflective layer 102, the active layer 103, and the second reflective layer 104 is between 8-10 microns.

In some embodiments, the first reflective layer 102 or the second reflective layer 104 comprises a series of alternating layers of materials of different refractive indices, wherein the effective optical thickness of each alternating layer (the layer thickness times the layer refractive index) is an odd integer multiple of the operating wavelength of the quarter-wavelength VCSEL, i.e., the effective optical thickness of each alternating layer is a quarter of an odd integer multiple of the operating wavelength of the VCSEL. 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, and the like. Suitable semiconducting 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, in some embodiments, the first reflective layer 102 and the second reflective layer 104 may be formed of other materials.

In some embodiments, the active layer 103 may include one or more nitride 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. 2-3, a plurality of first metal electrodes 105a are further formed on the second reflective layer 104, and the first metal electrodes 105a can be used as a reference for photolithography calibration in subsequent processes, so as to prepare a vertical cavity surface emitting laser with high precision, and the first metal electrodes 105a can also be used as metal contact pads for subsequent second electrodes. The material of the first metal electrode 105a may include one or a combination of Au metal, Ag metal, Pt metal, Ge metal, Ti metal, and Ni metal, and may be specifically selected according to the requirement. In some embodiments, the surface of the second reflective layer 104 contacting the first metal electrode 105a has a higher concentration of dopant to form an ohmic contact layer, such that the contact resistance of the ohmic contact between the first metal electrode 105a and the second reflective layer 104 is reduced, wherein the ohmic contact layer may be an N-type doped ohmic contact layer.

As shown in fig. 3, in the present embodiment, the shape of the first metal electrode 105a may be, for example, a circular ring shape, and in some embodiments, the shape of the first metal electrode 105a may also be an elliptical ring shape, a rectangular ring shape, or a hexagonal ring shape, and the shape of the first metal electrode 105a may be selected as needed. In this embodiment, the inner diameter of the first metal electrode 105a is, for example, 5 to 97um, and the outer diameter of the first metal electrode 105a is, for example, 7 to 99um, and in some embodiments, the inner diameter and the outer diameter of the first metal electrode 105a are not limited and can be selected according to the requirement.

As shown in fig. 4-6, after forming the first metal electrode 105a, a patterned photoresist layer 106 is first formed on the second reflective layer 104, the patterned photoresist layer 106 covers the first metal electrode 105a, and the patterned photoresist layer 106 exposes a portion of the second reflective layer 104, and then the second reflective layer 104 is etched downward according to the patterned photoresist layer 106 to form a plurality of trenches. The direction of the arrows in fig. 4 indicates the etching direction.

As shown in fig. 5, in the present embodiment, the etching process is performed to etch from the second reflective layer 104 to the surface of the first reflective layer 102, so as to form a first trench 107a, a second trench 107b and a third trench 107 c.

As shown in fig. 5A, in the present embodiment, a first platform-shaped structure 109a, a second platform-shaped structure 109b, a third platform-shaped structure 110a and a fourth platform-shaped structure 110b are sequentially arranged from left to right in fig. 5A. Wherein the third trench 107c surrounds the first mesa structure 109a, and the second trench 107b surrounds the second mesa structure 109b, and similarly, the third trench 107c surrounds the fourth mesa structure 110b, and the second trench 107b surrounds the third mesa structure 110a, that is, the second trench 107b and the third trench 107c are ring-shaped structures, and the widths of the second trench 107b and the third trench 107c are the same. The second trench 107b on the right side of the second mesa structure 109b and the second trench on the left side of the third trench 110a form the first trench 107a, for example, the two second trenches 107b in this embodiment form the first trench 107a tangentially, although in some embodiments the first trench 107a may also be formed when the two second trenches 107b are separated and intersect. For example, when the two second trenches 107b are separated, another mesa structure is formed between the two second trenches 107b, and the mesa structure can be left or etched away. When the two second trenches 107b intersect, the width of the first trench 107a is smaller than the sum of the widths of the second trench 107b and the third trench 107c, and the minimum width of the first trench 107a is equal to the width of the second trench 107b or the third trench 107 c.

As shown in fig. 5, in the present embodiment, the width of the first trench 107a may be, for example, greater than the width of the second trench 107b, and the width of the second trench 107b may be, for example, equal to the width of the third trench 107 c. The width of first slot 107a is at 3 ~ 10um, and the width of second slot 107b is at 1 ~ 5um, and the width of third slot 107c is at 1 ~ 5um, forms the mesa structure between first slot 107a and the second slot 107b, forms the mesa structure between second slot 107b and the third slot 107c, the mesa structure is used for forming the luminescence subunit. The width of the mesa structure is 10-100 um, and the depths of the first trench 107a, the second trench 107b and the third trench 107c are the same, i.e. the sum of the thicknesses of the second reflective layer 104 and the active layer 103 is included.

In some embodiments, a portion of the first reflective layer 102 may also be removed by etching, but the first reflective layer 102 cannot be completely removed, i.e., the depth of the first trench 107a is less than the sum of the thicknesses of the first reflective layer 102, the active layer 103 and the second reflective layer 104.

In some embodiments, the plurality of trenches may be formed, for example, by wet etching or dry etching.

As shown in fig. 6, in the present embodiment, after forming a plurality of trenches, it is also necessary to form a current confinement layer 108 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 108 in the second reflective layer 104. In the present embodiment, a plurality of current confinement layers 108 are formed in the second reflective layer 104 by oxidizing the sidewalls of the first trench 107a, the second trench 107b, and the third trench 107 c.

As shown in fig. 5 to 6, in the present embodiment, the first mesa structure 109a is defined as a first light emitting subunit, and the second mesa structure 109b is defined as a second light emitting subunit. The first mesa structure 109a and the second mesa structure 109b have the same structure, and the first mesa structure 109a is taken as an example for explanation in this embodiment. The first mesa structure 109a includes an active layer 103, a second reflective layer 104 and a first metal electrode 105a from bottom to top, a current confinement layer 108 is formed in the second reflective layer 104, and the current confinement layer 108 contacts with a sidewall of the first mesa structure 109a and extends into the first mesa structure 109 a. The current confinement layer 108 in the first mesa structure 109a is a ring-shaped structure, and a light-emitting hole is defined by the current confinement layer 108.

As shown in fig. 6, in the first mesa structure 109a, the current confinement layer 108 located in the second reflective layer 104 extends to the inner diameter of the first metal electrode 105a, or the first metal electrode 105a is located at the outer periphery of the light emitting hole, so that the later formed second electrode does not block the light emitting hole.

As shown in fig. 5 to 6, 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 sub-unit and the second light emitting sub-unit have the same structure, thereby defining the first light emitting sub-unit and the second light emitting sub-unit as the first light emitting unit 109. In the present embodiment, the third mesa structure 110a is defined as a third light emitting sub-unit, the fourth mesa structure 110b is defined as a fourth light emitting sub-unit, and the third mesa structure 110a has the same structure as the fourth mesa structure 110b, thereby defining a combination of the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 110. The first light emitting unit 109 and the second light emitting unit 110 are separated by a first groove 107 a.

As shown in FIG. 6, in the present embodiment, the outer diameter of the first metal electrode 105a on the first mesa structure 109a has a certain distance from the second trench 107b or the third trench 107c, for example, the distance between the left side of the first metal electrode 105a and the side wall of the third trench 107c is D1, the distance D1 may range from 1 um to 5um, the distance between the right side of the first metal electrode 105a and the side wall of the second trench 107b is D2, and the distance D2 may range from 1 um to 5 um.

As shown in fig. 6, 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, and the oxidation confinement type current confinement structure is adopted in the present embodiment.

As shown in fig. 5 to 6, in the present embodiment, the first groove 107a is defined to be located outside the first light emitting unit 109 or the second light emitting unit 110. Similarly, the insulating layer formed in the first trench 107a is also located outside the first light emitting unit 109 or the second light emitting unit 110.

As shown in fig. 5 to 7, in step S4, after the current confinement layer 108 is formed, the insulating layer 111 is formed within the trench. In the present embodiment, a part of the insulating layer 111 is located in the first trench 107a, a part of the insulating layer 111 is located in the second trench 107b, and a part of the insulating layer 111 is located in the third trench 107 c. In the embodiment, the insulating layer 111 in the first trench 107a is taken as an example for explanation, a portion of the insulating layer 111 is located on the bottom and the sidewall of the first trench 107a, and the insulating layer 111 extends to the second reflective layer 104 along the sidewall of the first trench 107a and contacts the first metal electrode 105 a. Thereby insulating the first light emitting unit 109 from the second light emitting unit 110. Similarly, the first light-emitting subunit and the second light-emitting subunit are insulated and separated by the insulating layer 111, and the third light-emitting subunit and the fourth light-emitting subunit are insulated and separated by the insulating layer 111.

As shown in fig. 7, in the present embodiment, a part of the insulating layer 111 is located on the second reflective layer 104 and is in contact with the first metal electrode 105a, a part of the insulating layer 111 is located on the sidewalls of the second reflective layer 104 and the active layer 103, and a part of the insulating layer 111 is located on the first reflective layer 102. Note that the insulating layer 111 on the first reflective layer 102 cannot be defined as being located in the active layer 103 or the second reflective layer 104 or the first reflective layer 102, and for example, the current confinement layer 108 may be defined as being located in the second reflective layer 104.

As shown in fig. 7, the material of the insulating layer 111 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 111 may be 100 nm to 300nm, and the insulating layer 111 may protect the current confinement layer 108 and may also effectively isolate the adjacent mesa structures. In the present embodiment, the insulating layer 111 can be formed by, for example, chemical vapor deposition.

As shown in fig. 8, after the insulating layer 111 is formed, a metal layer is formed on the mesa structure to form the first electrode 112 and the second electrode 105 in steps S5-S6.

As shown in fig. 8, in the present embodiment, the first electrode 112 is located on the mesa structure at two ends, that is, the first electrode 112 is located at two sides of the first light emitting unit 109 and the second light emitting unit 110 respectively. In the embodiment, the first electrode 112 on the left side is taken as an example for description, the first electrode 112 is located on the mesa structure, a portion of the first electrode 112 is located on the second reflective layer 104 and covers the light emitting hole formed by the current limiting layer 108, and a portion of the first electrode 112 extends to the first reflective layer 102 along the sidewall of the mesa structure and contacts the first reflective layer 102. And the first electrode 112 completely covers the sidewalls of the mesa structure. The first electrodes 112 at both ends are in contact with the first reflective layer 102, so that the first electrodes 112 at both ends and the first reflective layer 102 form a common anode. The invention is not limited thereto, and in some embodiments, the first electrode 112 may be formed on one of two sides of the first light emitting unit 109 and the second light emitting unit 110, or may be formed between the first light emitting unit 109 and the second light emitting unit 110. When the first electrode 112 is formed on one of the two sides of the first light emitting unit 109 and the second light emitting unit 110, the first electrode 112 is formed as described above. When the first electrode 112 is formed between the first light emitting unit 109 and the second light emitting unit 110, the insulating layer at the bottom of the first trench 107a needs to be removed first, and then the first electrode 112 contacting the first reflective layer 102 is formed at the bottom of the first trench 107 a; or removing the insulating layer at the bottom of the first trench 107a, forming a mesa structure at the bottom of the first trench 107a, and forming a first electrode 112 covering the mesa structure and contacting the first reflective layer 102 in the first trench 107a, wherein the height of the first electrode 112 relative to the first reflective layer 102 is less than or equal to the height of the second electrode 105 relative to the first reflective layer 102. In some embodiments, the surface of the first reflective layer 102 contacting the first electrode 112 has a higher concentration of doping to form an ohmic contact layer, which may be a P-type doped ohmic contact layer, so as to reduce the contact resistance of the ohmic contact between the first electrode 112 and the first reflective layer 102.

As shown in fig. 8, the first electrodes 112 at both ends may be connected to form a ring-shaped electrode, or the first electrodes 112 at both ends may be separated from each other, and the first electrodes 112 at both ends are connected to the first reflective layer 102 to form a common anode.

As shown in fig. 8, in the present embodiment, when forming the second electrode 105, it is necessary to form the second metal electrode 105b first, and form the second electrode 105 by the first metal electrode 105a and the second metal electrode 105 b. In this embodiment, taking the second electrode 105 in the second light emitting unit 110 as an example, a part of the second metal electrode 105b is located on the second light emitting unit 110, that is, a part of the second metal electrode 105b is located on the insulating layer 111 and the first metal electrode 105a so as to be connected to the first metal electrode 105a, and a part of the second metal electrode 105b is also located in the second trench 107b and extends toward the first metal electrode 105a on both sides, that is, a part of the second metal electrode 105b grows upward from the second trench 107b, covers the insulating layer 111 on the second reflective layer 104 and is connected to the first metal electrodes 105a of the third light emitting subunit and the fourth light emitting subunit, so as to form the second electrode 105. In the present embodiment, the light emitting sub-units in the second light emitting unit 110 are connected through the second electrode 105. The first light emitting unit 109 and the second light emitting unit 110 have the same structure, and the first light emitting unit 109 is not illustrated in this embodiment, and the second metal electrode 105b is not formed between the first light emitting unit 109 and the second light emitting unit 110, so that the first light emitting unit 109 and the second light emitting unit 110 are insulated. It should be noted that the second metal electrode 105b located in the second trench 107b cannot be defined as located in the second reflective layer 104 or the active layer 103. In the present embodiment, the second electrode 105 is formed by the first metal electrode 105a and the second metal electrode 105b, and the second electrode 105 is formed at the outer circumference of the light emitting hole, i.e., the second electrode 105 does not block the light emitting hole.

As shown in fig. 8, in the present embodiment, the first light emitting unit 109 is isolated from the second light emitting unit 110 by the first groove 107a, and the two light emitting sub-units within each light emitting unit are isolated by the second groove 107 b. When the first light emitting unit 109 includes three light emitting sub-units, the second trench 107b and the third trench 107c are used to isolate the three light emitting sub-units.

As shown in fig. 8, in the present embodiment, the height of the first electrode 112 is equal to the height of the second electrode 105, and in some embodiments, the height of the first electrode 112 may be lower than the height of the second electrode 105.

As shown in fig. 8, in the present embodiment, the material of the first electrode 112 may include one or a combination of Au metal, Ag metal, Pt metal, Ge metal, Ti metal, and Ni metal, and the material of the second electrode 105 may include one or a combination of Au metal, Ag metal, Pt metal, Ge metal, Ti metal, and Ni metal.

As shown in fig. 8, in this embodiment, the vcsel can reduce the area of the light-emitting unit by forming the common anode, and can also address independently, with a short interconnection length. The vertical cavity surface emitting laser can also select an N-MOS driver with smaller volume and higher speed, and can also improve the application frequency of the device.

In some embodiments, as shown in fig. 9, another method for fabricating a vertical cavity surface emitting laser can be further provided, including,

s11: providing a substrate;

s12: forming a first reflective layer on the substrate;

s13: forming at least two light emitting units on the first reflective layer, each light emitting unit including at least two light emitting sub-units, a first groove formed between the at least two light emitting units, the first groove exposing the substrate, each light emitting sub-unit including a light emitting hole;

s14: forming an insulating layer in the first trench;

s15: forming at least one first electrode on the at least two light-emitting units, wherein the first electrode is connected with the at least two light-emitting units, the light-emitting sub-units in each light-emitting unit are connected through the first electrode to form a common anode, and the first electrode surrounds the periphery of the light-emitting hole;

s16: forming at least two second electrodes contacting the first reflective layer.

As shown in fig. 10, in steps S11-S13, a substrate 201 is provided, a first reflective layer 202 is formed on the substrate 201, an active layer 203 is formed on the first reflective layer 202, and a second reflective layer 204 is formed on the active layer 203. In this embodiment, the substrate 201 may be any semi-insulating material suitable for forming a vertical cavity surface emitting laser, the first reflective layer 202 may be an N-type bragg mirror, the active layer 203 includes a stacked quantum well composite structure composed of GaAs and AlGaAs, or a stacked arrangement of InGaAs and AlGaAs materials, the active layer 203 is used to convert electrical energy into optical energy, and the second reflective layer 204 may be a P-type bragg mirror.

As shown in fig. 10, a plurality of first metal electrodes 205a are further formed on the second reflective layer 204, and the first metal electrodes 205a can be used as a reference for photolithography calibration in a subsequent process, so as to prepare a vertical cavity surface emitting laser with high precision, and the first metal electrodes 205a can also be used as metal contact pads for a subsequent second electrode. The shape of the first metal electrode 205a can be seen in fig. 3.

As shown in fig. 11, in step S13, after the first metal electrode 205a is formed, a patterned photoresist layer 206 is first formed on the second reflective layer 104, the patterned photoresist layer 206 covers the first metal electrode 205a, and the patterned photoresist layer 206 exposes a portion of the second reflective layer 204, and then the second reflective layer 204 is etched downward according to the patterned photoresist layer 206 to form a plurality of trenches. The direction of the arrows in fig. 11 indicates the etching direction.

As shown in fig. 12, in the present embodiment, an etching process is performed to etch from the second reflective layer 204 downward to form a first trench 207a, a second trench 207b and a third trench 207c, wherein the depth of the first trench 207a is greater than the depth of the second trench 207b and the third trench 207 c. The depth of the first trench 207a includes the sum of the thicknesses of the second reflective layer 204, the active layer 203 and the first reflective layer 202, i.e., the first trench 207a exposes the substrate 201, so that the first trench 207a divides the first reflective layer 202 into a plurality of portions. The depth of the second trench 207b and the third trench 207c includes the sum of the thicknesses of the second reflective layer 204 and the active layer 203, so the second trench 207b and the third trench 207c divide the second reflective layer 204 and the active layer 203 into a plurality of portions. The first trench 207a is used to separate the light emitting cells, and the second and

third trenches

207b and 207c are used to separate the light emitting sub-cells. The width of the first groove 207a may be, for example, greater than the width of the second groove 207b, and the width of the second groove 207b may be, for example, equal to the width of the third groove 207 c. The width of the first trench 207a is, for example, 3-10 um, the width of the second trench 207b is, for example, 1-5 um, the width of the third trench 207c is, for example, 1-5 um, a mesa structure is formed between the first trench 207a and the second trench 207b, and a mesa structure is formed between the second trench 207b and the third trench 207c, and the mesa structure is used for forming a light emitting subunit. The width of the table-shaped structure is 10-100 um.

As shown in fig. 13, in the present embodiment, after forming a plurality of trenches, it is also necessary to form a current confinement layer 208 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 208 in the second reflective layer 204. In the present embodiment, a plurality of current confinement layers 208 are formed in the second reflective layer 204 by oxidizing the sidewalls of the first trench 207a, the second trench 207b, and the third trench 207 c.

As shown in fig. 13, in the present embodiment, the first mesa structure 209a is defined as a first light emitting sub-unit, and the second mesa structure 209b is defined as a second light emitting sub-unit. The first mesa 209a and the second mesa 209b have the same structure, and the first mesa 209a is taken as an example for explanation in this embodiment. The first mesa structure 209a includes an active layer 203, a second reflective layer 204 and a first metal electrode 205a from bottom to top, a current confinement layer 208 is formed in the second reflective layer 204, the current confinement layer 208 is in contact with a sidewall of the first mesa structure 209a and extends into the first mesa structure 209a, i.e., the current confinement layer 208 extends from the sidewall of the second reflective layer 204 into the second reflective layer 204. The current confinement layer 208 in the first mesa structure 209a is a ring-shaped structure, and a light-emitting hole is defined by the current confinement layer 208.

As shown in fig. 13, in the first mesa structure 209a of the present embodiment, a first end of the current confinement layer 208 is in contact with a sidewall of the second reflective layer 204, a second end is located in the second reflective layer 204 and is flush with an inner diameter of the first metal electrode 205a, or the second end extends into the inner diameter of the first metal electrode 205a, that is, the first metal electrode 205a is located at an outer periphery of the light emitting hole, so that the light emitting hole is not blocked by the later formed first electrode.

As shown in fig. 13, in the present embodiment, the first mesa structure 209a and the second mesa structure 209b have the same structure, and thus the first light emitting sub-unit and the second light emitting sub-unit have the same structure, thereby defining the first light emitting sub-unit and the second light emitting sub-unit as the first light emitting unit 209. In the present embodiment, the third mesa structure 210a is defined as a third light emitting sub-unit, the fourth mesa structure 210b is defined as a fourth light emitting sub-unit, and the third mesa structure 210a and the fourth mesa structure 210b have the same structure, thereby defining the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 210. The first light emitting unit 209 and the second light emitting unit 210 are separated by a first groove 207 a.

As shown in fig. 13, in the present embodiment, the outer diameter of the first metal electrode 205a on the first mesa structure 109a has a certain distance from the second trench 207b or the third trench 207c, for example, the distance between the left side of the first metal electrode 205a and the side wall of the third trench 207c is D1, the distance D1 may range from 1 um to 5um, the distance between the right side of the first metal electrode 205a and the side wall of the second trench 207b is D2, and the distance D2 may range from 1 um to 5 um.

As shown in fig. 13, in some embodiments, the current confinement layer 208 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 13 to 14, in the present embodiment, the first trench 207a is defined to be located outside the first light emitting cell 209 or the second light emitting cell 210, and similarly, the insulating layer 211 formed in the first trench 207a is also located outside the first light emitting cell 209 or the second light emitting cell 210.

As shown in fig. 13 to 14, in step S4, after the current confinement layer 208 is formed, an insulating layer 211 is formed within the trench. In the present embodiment, a part of the insulating layer 211 is located in the first trench 207a, a part of the insulating layer 211 is located in the second trench 207b, and a part of the insulating layer 211 is located in the third trench 207 c. In the embodiment, the insulating layer 211 in the first trench 207a is taken as an example for illustration, a portion of the insulating layer 211 is located on the bottom and the sidewall of the first trench 207a, and the insulating layer 211 extends to the second reflective layer 204 along the sidewall of the first trench 207a and contacts the first metal electrode 205 a. Thereby insulating the first light emitting cell 209 from the second light emitting cell 210. Similarly, the first light-emitting subunit and the second light-emitting subunit are insulated and separated by the insulating layer 211, and the third light-emitting subunit and the fourth light-emitting subunit are insulated and separated by the insulating layer 211.

As shown in fig. 14, in the present embodiment, a part of the insulating layer 211 is located on the second reflective layer 204 and is in contact with the first metal electrode 205a, a part of the insulating layer 211 is located on the sidewalls of the second reflective layer 204 and the active layer 103, and a part of the insulating layer 211 is located on the substrate 101. Note that the insulating layer 211 on the substrate 201 cannot be defined as being located in the active layer 103 or the second reflective layer 204 or the first reflective layer 202. For example, the current confinement layer 208 may be defined as being located within the second reflective layer 204, with the insulating layer 211 being located outside the second reflective layer 204.

As shown in fig. 14, the material of the insulating layer 211 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 211 may be 100 nm to 300nm, and the insulating layer 211 may protect the current confinement layer 208 and may also effectively isolate the adjacent mesa structures. In the present embodiment, the insulating layer 211 may be formed by, for example, chemical vapor deposition.

As shown in fig. 15, in steps S15-S16, after the insulating layer 211 is formed, a metal layer is formed on the mesa structure to form a plurality of first electrodes 205 and second electrodes 212.

As shown in fig. 15, in the present embodiment, when forming the first electrode 205, it is necessary to form the second metal electrode 205b first, and form the first electrode 205 by the first metal electrode 205a and the second metal electrode 205 b. In this embodiment, taking the first electrode 205 in the second light emitting unit 210 as an example, a part of the second metal electrode 205b is located on the second light emitting unit 210, that is, a part of the second metal electrode 205b is located on the insulating layer 211 and the first metal electrode 205a, so as to be connected to the first metal electrode 205a, and a part of the second metal electrode 205b is further located in the second trench 207b and extends toward the first metal electrode 205a on both sides, that is, a part of the second metal electrode 205b grows upward from the second trench 207b, covers the insulating layer 211 located on the second reflective layer 204, and is connected to the first metal electrodes 205a of the third light emitting subunit and the fourth light emitting subunit, so as to form the first electrode 205. In the present embodiment, two light emitting sub-units within the second light emitting unit 210 are connected through the first electrode 205.

As shown in fig. 15, in the present embodiment, a second metal electrode 205b is further formed in the first trench 207a, the second metal electrode 205b is located on the insulating layer 211 in the first trench 207a and extends toward the first light emitting unit 209 and the second light emitting unit 210, that is, a portion of the second metal electrode 205b covers the insulating layer 211 on the second reflective layer 204, so as to contact the first metal electrodes 205a of the first light emitting unit 209 and the second light emitting unit 210, and the second metal electrode 205b is located on the first metal electrode 205 a. In the present embodiment, the second metal electrode 205b and the first metal electrode 205a located in the first trench 207a form the second electrode 205, the first light emitting unit 209 and the second light emitting unit 210 are connected through the second electrode 205, and all the second electrodes 205 are connected through the second electrode 205, thereby forming a common anode. It should be noted that the second metal electrode 205b located in the first trench 207a cannot be defined as located in the second reflective layer 204 or in the active layer 203 or the first reflective layer 202. In the present embodiment, the first electrode 205 is formed by the first metal electrode 205a and the second metal electrode 205b, and the first electrode 205 is formed at the periphery of the light emitting hole, i.e., the first electrode 205 does not block the light emitting hole.

As shown in fig. 15, in the present embodiment, the plurality of second electrodes 212 are located on the mesa structures at two ends, that is, the plurality of second electrodes 212 are respectively located at two sides of the first light emitting unit 209 and the second light emitting unit 210. In the embodiment, the right second electrode 212 is taken as an example for description, the second electrode 212 is located on the mesa structure, a portion of the second electrode 212 is located on the second reflective layer 204 and covers the light emitting hole formed by the current limiting layer 208, and a portion of the second electrode 212 extends to the first reflective layer 202 along the sidewall of the mesa structure and contacts the first reflective layer 202. And the second electrode 212 completely covers the sidewalls of the mesa structure. The second electrodes 212 at both ends are in contact with the first reflective layer 202, and since the first trench 207a divides the first reflective layer 202 into two parts, and the first trench 207a is filled with the insulating layer 211, and the substrate 201 is a semi-insulating substrate, a plurality of independent second electrodes 212, that is, a plurality of independent cathodes, are implemented. In the present embodiment, a plurality means at least two, for example, two, three, four or more.

As shown in fig. 15, in this embodiment, the vcsel can reduce the area of the light-emitting unit by forming the common anode, and can also address independently, with a short interconnection length. The vertical cavity surface emitting laser can also select an N-MOS driver with smaller volume and higher speed, and can also improve the application frequency of the device.

In some embodiments, as shown in fig. 16, another method for fabricating a vertical cavity surface emitting laser can be further provided, including,

s21: providing a substrate;

s22: forming a first reflective layer on a first surface of the substrate;

s23: forming at least two light emitting units on the first reflective layer, each light emitting unit including at least two light emitting sub-units, each light emitting sub-unit including a light emitting hole;

s24: forming an insulating layer between the light emitting units;

s25: forming at least two second electrodes on the at least two light-emitting units, wherein the light-emitting sub-units of each light-emitting unit are connected through the second electrodes, and the second electrodes surround the peripheries of the light-emitting holes;

s26: a first electrode is formed on the second surface of the substrate.

As shown in fig. 17, in step S21, a substrate 301 is first provided, where the substrate 301 includes a first surface 301a and a second surface 301b, and the first surface 301a is disposed opposite to the second surface 301b, in this embodiment, the substrate 301 may be a P-type doped semiconductor substrate, and the doping can reduce the contact resistance of the ohmic contact between the subsequently formed electrode and the semiconductor substrate.

As shown in fig. 18, in steps S22-S23, a substrate 301 is first provided, a first reflective layer 302 is then formed on the first surface 301a of the substrate 301, an active layer 303 is formed on the first reflective layer 302, and a second reflective layer 304 is formed on the active layer 303. In this embodiment, the first reflective layer 302 may be a P-type bragg mirror. The active layer 303 includes a quantum well composite structure stacked and composed of GaAs and AlGaAs, or a stacked arrangement of InGaAs and AlGaAs materials, the active layer 303 is used to convert electrical energy into optical energy, and the second reflective layer 304 may be an N-type bragg mirror.

As shown in fig. 18, a plurality of first metal electrodes 305a are further formed on the second reflective layer 304, and the first metal electrodes 305a can be used as a reference for photolithography calibration in subsequent processes, so as to prepare a vertical cavity surface emitting laser with higher precision, and the first metal electrodes 305a can also be used as metal contact pads for subsequent second electrodes. The shape of the first metal electrode 305a is shown in fig. 3. In some embodiments, the surface of the second reflective layer 304 contacting the first metal electrode 305a has a higher concentration of dopant to form an ohmic contact layer, such that the contact resistance of the ohmic contact between the first metal electrode 305a and the second reflective layer 304 is reduced, wherein the ohmic contact layer may be an N-type doped ohmic contact layer.

As shown in fig. 19-21, after forming the first metal electrode 305a, a patterned photoresist layer 306 is first formed on the second reflective layer 304, the patterned photoresist layer 306 covers the first metal electrode 305a, and the patterned photoresist layer 306 exposes a portion of the second reflective layer 304, and then the second reflective layer 304 is etched downward according to the patterned photoresist layer 306 to form a plurality of trenches. The direction of the arrows in fig. 19 indicates the etching direction.

As shown in fig. 20, in the present embodiment, the first trench 307a, the second trench 307b and the third trench 307c are formed by etching from the second reflective layer 304 down to the surface of the first reflective layer 302 through an etching process. The structure of the first trench 307a, the second trench 307b and the third trench 307c can be seen in fig. 5A, the first trench 307a is used to separate the light emitting cells, and the second trench 307b and the third trench 307c are used to separate the light emitting sub-cells.

As shown in FIG. 20, in the present embodiment, the width of the first trench 307a is 3-10 um, the width of the second trench 307b is 1-5 um, the width of the third trench 307c is 1-5 um, a mesa structure is formed between the first trench 307a and the second trench 307b, and a mesa structure is formed between the second trench 307b and the third trench 307c, the mesa structure is used for forming a light emitting sub-unit, and the width of the mesa structure is 10-100 um.

As shown in fig. 20, the first trench 307a, the second trench 307b, and the third trench 307c have the same depth, i.e., include the sum of the thicknesses of the second reflective layer 304 and the active layer 103, thereby dividing the second reflective layer 304 into a plurality of portions. The width of the first trench 307a may be, for example, greater than the width of the second trench 307b, and the width of the second trench 307b may be, for example, equal to the width of the third trench 307 c.

In some embodiments, a portion of the first reflective layer 302 may also be removed by etching, but the first reflective layer 302 cannot be completely removed, i.e., the depth of the first trench 307a is less than the sum of the thicknesses of the first reflective layer 302, the active layer 303, and the second reflective layer 304.

As shown in fig. 21, in the present embodiment, after forming a plurality of trenches, it is also necessary to form a current confinement layer 308 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewalls of the trench are oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 308 in the second reflective layer 304. In the present embodiment, a plurality of current confinement layers 308 are formed in the second reflective layer 304 by oxidizing the sidewalls of the first trench 307a, the second trench 307b, and the third trench 307 c.

As shown in fig. 21, in the present embodiment, the first mesa structure 309a is defined as a first light emitting sub-unit, and the second mesa structure 309b is defined as a second light emitting sub-unit. The first mesa structure 309a and the second mesa structure 309b have the same structure, and the first mesa structure 309a is taken as an example for explanation in this embodiment. The first mesa structure 309a includes the active layer 103, the second reflective layer 304 and the first metal electrode 305a from bottom to top, a current confinement layer 308 is formed in the second reflective layer 304, the current confinement layer 308 is in contact with a sidewall of the first mesa structure 309a and extends into the first mesa structure 309a, i.e., the current confinement layer 308 extends from the sidewall of the second reflective layer 304 into the second reflective layer 304. The current confinement layer 308 in the first mesa-shaped structure 309a is a ring-shaped structure, and a light-emitting hole is defined by the current confinement layer 308.

As shown in fig. 21, in the first mesa structure 309a of the present embodiment, the first end of the current confinement layer 308 is in contact with the sidewall of the second reflective layer 304, the second end is located in the second reflective layer 304, and the second end is flush with the inner diameter of the first metal electrode 305a, or the second end extends into the inner diameter of the first metal electrode 305a, that is, the first metal electrode 305a is located at the periphery of the light emitting hole, so that the first electrode formed later does not block the light emitting hole.

As shown in fig. 21 to 22, in the present embodiment, the first mesa structure 309a and the second mesa structure 309b have the same structure, and thus the first light-emitting sub-unit and the second light-emitting sub-unit have the same structure, thereby defining the first light-emitting sub-unit and the second light-emitting sub-unit as the first light-emitting unit 309. In the present embodiment, the third mesa structure 310a is defined as a third light emitting sub-unit, the fourth mesa structure 310b is defined as a fourth light emitting sub-unit, and the third mesa structure 310a has the same structure as the fourth mesa structure 110b, thereby defining the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 310. The first light emitting unit 309 and the second light emitting unit 310 are separated by a first trench 307 a.

As shown in fig. 21, in the present embodiment, the outer diameter of the first metal electrode 305a on the first mesa structure 309a has a certain distance from the second trench 307b or the third trench 307c, for example, the distance between the left side of the first metal electrode 305a and the side wall of the third trench 307c is D1, the distance D1 may range from 1 um to 5um, the distance between the right side of the first metal electrode 305a and the side wall of the second trench 307b is D2, and the distance D2 may range from 1 um to 5 um.

As shown in fig. 21, in some embodiments, the current confinement layer 308 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 20 to 21, in the present embodiment, the first trench 307a is defined to be located outside the first light emitting cell 309 or the second light emitting cell 310, and similarly, the insulating layer formed in the first trench 307a is also located outside the first light emitting cell 309 or the second light emitting cell 310.

As shown in fig. 22, in step S24, after the current confinement layer 308 is formed, an insulating layer 311 is formed within the trench. In the present embodiment, a portion of the insulating layer 311 is located in the first trench 307a, the insulating layer 311 is located in the second trench 307b, and a portion of the insulating layer 311 is located in the third trench 307 c. In the present embodiment, the insulating layer 311 in the first trench 307a is taken as an example for illustration, a portion of the insulating layer 311 is located on the bottom and the sidewall of the first trench 307a, and the insulating layer 311 extends to the second reflective layer 304 along the sidewall of the first trench 307a and contacts the first metal electrode 305 a. Thereby insulating the first light emitting unit 309 from the second light emitting unit 310. Similarly, the first light emitting subunit and the second light emitting subunit are insulated and separated by the insulating layer 311, and the third light emitting subunit and the fourth light emitting subunit are insulated and separated by the insulating layer 311.

As shown in fig. 22, in the present embodiment, a partial insulating layer 311 is located on the second reflective layer 304 and is in contact with the first metal electrode 105a, a partial insulating layer 311 is located on the sidewalls of the second reflective layer 304 and the active layer 303, and a partial insulating layer 311 is located on the first reflective layer 302. Note that the insulating layer 311 on the first reflective layer 302 cannot be defined as being located in the active layer 303, the second reflective layer 304, or the first reflective layer 102. The current confinement layer 308 may be defined, for example, to be within the second reflective layer 304.

As shown in fig. 22, the material of the insulating layer 311 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 311 may be 100 nm to 300nm, and the insulating layer 311 may protect the current confinement layer 308 and may also effectively isolate the adjacent mesa structures. In the present embodiment, the insulating layer 311 can be formed by, for example, chemical vapor deposition.

As shown in fig. 23, in steps S25-S26, after the insulating layer 311 is formed, a metal layer is formed on the mesa structure to form a plurality of second electrodes 305, and a first electrode 312 is formed on the second surface 301b of the substrate 301.

As shown in fig. 20 and 23, in the present embodiment, when forming the second electrode 305, it is necessary to form the second metal electrode 305b first, and form the second electrode 305 from the first metal electrode 305a and the second metal electrode 305 b. In this embodiment, taking the second electrode 305 in the second light emitting unit 310 as an example, a part of the second metal electrode 305b is located on the second light emitting unit 310, that is, a part of the second metal electrode 305b is located on the insulating layer 311 and the first metal electrode 305a so as to be connected to the first metal electrode 305a, and a part of the second metal electrode 305b is also located in the second trench 307b and extends toward the first metal electrode 305a on both sides, that is, a part of the second metal electrode 305b grows upward from the second trench 307b, covers the insulating layer 311 on the second reflective layer 304 and is connected to the first metal electrodes 305a of the third light emitting subunit and the fourth light emitting subunit, so as to form the second electrode 305. In the present embodiment, the light emitting sub-units in the second light emitting unit 310 are connected through the second electrode 305. The first light emitting unit 309 and the second light emitting unit 310 have the same structure, and the first light emitting unit 309 is not described in this embodiment. The second metal electrode 305b is not formed between the first light emitting cell 309 and the second light emitting cell 310, and thus the first light emitting cell 309 and the second light emitting cell 310 are insulated. It should be noted that the second metal electrode 305b located in the second trench 307b cannot be defined as located in the second reflective layer 304 or the active layer 303. In the present embodiment, the second electrode 305 is formed by the first metal electrode 305a and the second metal electrode 305b, and the second electrode 305 is formed at the periphery of the light emitting hole, i.e., the second electrode 305 does not block the light emitting hole.

As shown in fig. 23, in the present embodiment, the first electrode 312 is formed on the second surface 301b of the substrate 301, and the first electrode 312 forms a common anode with the first reflective layer 302 through the substrate 301.

As shown in fig. 23, in this embodiment, the first electrode forms a common anode through the substrate and the first reflective layer, and forms a plurality of mutually separated cathodes, so that the area of the light emitting unit can be reduced, and simultaneously, the light emitting unit can be independently addressed, and the interconnection length is short. The vertical cavity surface emitting laser can also select an N-MOS driver with smaller volume and higher speed, and can also improve the application frequency of the device.

In some embodiments, as shown in fig. 24, another method for fabricating a vertical cavity surface emitting laser can be further provided, including,

s31: providing an epitaxial structure, wherein the epitaxial structure comprises a first reflecting layer, an active layer and a second reflecting layer;

s32: forming a plurality of first trenches in the epitaxial structure, wherein the first trenches penetrate through the epitaxial structure to divide the epitaxial structure into a plurality of light emitting units;

s33: forming an insulating layer in the first trenches;

s34: forming a plurality of first electrodes in the first grooves, wherein the first electrodes are connected with the light-emitting units, and the light-emitting sub-units in each light-emitting unit are connected through the first electrodes to form a common anode;

s34: and forming a plurality of second electrodes on the back surface of the first reflecting layer, wherein each second electrode is positioned between two adjacent first electrodes.

As shown in fig. 25, in step S1, a substrate 401 is provided, a first reflective layer 402 is formed on the substrate 401, an active layer 403 is formed on the first reflective layer 402, and a second reflective layer 404 is formed on the active layer 403. The first reflective layer 401, the active layer 402, and the second reflective layer 403 form an epitaxial structure. In this embodiment, the substrate 401 may be any semi-insulating material or N-doped semiconductor substrate suitable for forming a vertical cavity surface emitting laser. The first reflective layer 402 may be an N-type bragg mirror, the active layer 403 includes a quantum well composite structure stacked and composed of GaAs and AlGaAs or InGaAs and AlGaAs materials, and the active layer 403 is used for converting electrical energy into optical energy. The second reflective layer 404 may be a P-type bragg mirror.

As shown in fig. 25, a plurality of first metal electrodes 405a are further formed on the second reflective layer 404, and the first metal electrodes 405a can be used as a reference for photolithography calibration in a subsequent process, so as to prepare a vertical cavity surface emitting laser with high precision, and the first metal electrodes 45a can also be used as metal contact pads of subsequent first electrodes. The shape of the first metal electrode 405a is shown in fig. 3.

As shown in fig. 26, in step S32, after the first metal electrode 405a is formed, a patterned photoresist layer 406 is first formed on the second reflective layer 404, the patterned photoresist layer 406 covers the first metal electrode 405a, and the patterned photoresist layer 406 exposes a portion of the second reflective layer 404, and then the second reflective layer 404 is etched down according to the patterned photoresist layer 406 to form a plurality of trenches. The direction of the arrows in fig. 26 indicates the etching direction.

As shown in fig. 27, in the present embodiment, etching is performed downward from the second reflective layer 404 through an etching process to form a plurality of first trenches 407a and a plurality of second trenches 407 b. The first trench 407a penetrates the epitaxial structure, and the first trench 407a exposes the substrate 401, i.e., the first trench 407a sequentially etches the second reflective layer 404, the active layer 403, and the first reflective layer 402 from top to bottom, thereby dividing the first reflective layer 402 into a plurality of portions. The second trench 407b is etched from top to bottom sequentially to form the second reflective layer 404 and the active layer 403, i.e., the second trench 407b is exposed to the surface of the first reflective layer 402. The structure of the first trench 407a and the second trench 407b can be seen in fig. 5A. The mesa structure between the two first trenches 407a is used to form a light emitting cell, which is divided into a plurality of light emitting sub-cells by the second trenches 407 b.

As shown in FIG. 27, in the present embodiment, the width of the first trench 407a is greater than the width of the second trench 407b, the width of the first trench 407a is between 3 to 10um, and the width of the second trench 407b is between 1 to 5 um.

As shown in fig. 28, in step S33, after forming the plurality of trenches, it is also necessary to form a current confinement layer 408 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 408 in the second reflective layer 404. In the present embodiment, the sidewalls of the first trench 407a and the second trench 407b are oxidized to form a plurality of current confinement layers 408 in the second reflective layer 404.

As shown in fig. 28, in some embodiments, the current confinement layer 408 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 27 to 28, a plurality of mesa structures, such as a first mesa structure 409a, a second mesa structure 409b, a third mesa structure 410a and a fourth mesa structure 410b, are formed by the first trench 407a and the second trench 407 b. The first mesa structure 409a, the second mesa structure 409b, the third mesa structure 410a and the fourth mesa structure 410b are respectively used for forming a light emitting sub-unit, the first mesa structure 409a and the second mesa structure 409b are used for forming a first light emitting unit 409, and the third mesa structure 410a and the fourth mesa structure 410b are used for forming a second light emitting unit 410. The first light emitting unit 409 and the second light emitting unit 410 are described in the following.

As shown in fig. 29 to 30, in step S33, after the current confinement layer 408 is formed, an insulating layer 411 is formed within the trench. In this embodiment, a part of the insulating layer 411 is located in the first trench 407a, and a part of the insulating layer 411 is located in the second trench 407 b. In the embodiment, the insulating layer 411 in the middle of the first trench 407a is taken as an example for illustration, a portion of the insulating layer 411 is located on the bottom and the sidewall of the first trench 407a, and the insulating layer 411 extends to the second reflective layer 404 along the sidewall of the first trench 407a and contacts the first metal electrode 405 a. Similarly, the insulating layer 411 in the second trench 407b extends from the sidewall of the second trench 407b to the second reflective layer 404 and contacts the first metal electrode 405a, thereby realizing the insulating separation of the light emitting sub-units.

As shown in fig. 29, in the present embodiment, a part of the insulating layer 411 is located on the second reflective layer 404 and is in contact with the first metal electrode 405a, a part of the insulating layer 411 is located on the sidewalls of the second reflective layer 404 and the active layer 403, and a part of the insulating layer 411 is located on the substrate 401. Note that the insulating layer 411 on the substrate 401 cannot be defined as being located in the active layer 403 or the second reflective layer 404 or the first reflective layer 402. The current confinement layer 408 may be defined, for example, to be located within the second reflective layer 404.

As shown in fig. 29, the material of the insulating layer 411 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 411 may be 100-300nm, and the insulating layer 411 may protect the current confinement layer 408 and may effectively isolate the adjacent mesa structures. In this embodiment, the insulating layer 411 can be formed by, for example, chemical vapor deposition.

As shown in fig. 30, in step S34, a second metal electrode 405b is first formed in the first trench 407a and the second trench 407b to connect the second metal electrode 405b to the first metal electrode 405a, so as to form the first electrode 405.

As shown in fig. 30, in the present embodiment, the second metal electrode 405b is formed on the insulating layer 411, that is, a portion of the second metal electrode 405b is located on the insulating layer 411 in the first trench 407a, a portion of the second metal electrode 405b is located on the insulating layer 411 in the second trench 407b, a portion of the second metal electrode 405b is located on the insulating layer 411 on the second reflective layer 404, and a portion of the second metal electrode 405b is also located on the first metal electrode 405a and forms the first electrode 405 together with the first metal electrode 405 a. The second metal electrode 405b is aligned with the first metal electrode 405a, i.e. the second metal electrode 405b does not cover or block the light emitting hole, i.e. is located at the periphery of the light emitting hole.

As shown in fig. 30, in the present embodiment, the first mesa structure 409a is defined as a first light emitting sub-unit, and the second mesa structure 409b is defined as a second light emitting sub-unit. The first mesa structure 409a and the second mesa structure 409b have the same structure, and the first mesa structure 409a is taken as an example for explanation in this embodiment. The first mesa structure 409a includes, from bottom to top, an active layer 403, a second reflective layer 404, a first metal electrode 405a and a second metal electrode 405b, a current confinement layer 408 is formed in the second reflective layer 404, the current confinement layer 408 is in contact with a sidewall of the first mesa structure 409a and extends into the first mesa structure 409a, that is, the current confinement layer 408 extends from the sidewall of the second reflective layer 404 into the second reflective layer 404. The current confinement layer 408 in the first mesa structure 409a is a ring-shaped structure, and a light-emitting hole is defined by the current confinement layer 408.

As shown in fig. 30, in the first mesa structure 409a, a first end of the current confinement layer 408 contacts with a sidewall of the second reflective layer 404, a second end is located in the second reflective layer 404 and is flush with an inner diameter of the first metal electrode 405a, or the second end extends into the inner diameter of the first metal electrode 405a, that is, the first metal electrode 405a is located at an outer periphery of the light emitting hole, so that the light emitting hole is not blocked by the later formed first electrode.

As shown in fig. 30, in the present embodiment, the first mesa structure 409a and the second mesa structure 409b have the same structure, and thus the first light emitting sub-unit and the second light emitting sub-unit have the same structure, thereby defining the first light emitting sub-unit and the second light emitting sub-unit as the first light emitting unit 409. In the present embodiment, the third mesa structure 410a is defined as a third light emitting sub-unit, the fourth mesa structure 410b is defined as a fourth light emitting sub-unit, and the third mesa structure 410a and the fourth mesa structure 410b have the same structure, thereby defining the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 410.

As shown in fig. 30, in the present embodiment, a first trench 407a is formed between the first light emitting unit 409 and the second light emitting unit 410, a second metal electrode 405b is formed in the first trench 407a, and the second metal electrode 405b is connected to the first light emitting unit 409 and the first metal electrode 405b on the second light emitting unit 410, so as to connect the first light emitting unit 409 and the second light emitting unit 410, that is, the first light emitting unit 409 and the second light emitting unit 410 are connected to the first metal electrode 405a through the second metal electrode 405 b.

As shown in fig. 30, in the present embodiment, a second trench 407b is formed between the first mesa structure 409a and the second mesa structure 409b, a second metal electrode 405b is formed in the second trench 407b, and the second metal electrode 405b is connected to the first metal electrodes 405b on the first mesa structure 409a and the second mesa structure 409b, so as to connect the first mesa structure 409a and the second mesa structure 409b, that is, the first mesa structure 409a and the second mesa structure 409b are connected to the first metal electrode 405a through the second metal electrode 405b, that is, the first light emitting subunit is connected to the second light emitting subunit. In the same way, the second light emitting unit 410 has the same structure as the first light emitting unit 409, and the second light emitting unit 410 is not illustrated in this embodiment.

As shown in fig. 31, in the present embodiment, after the second metal electrode 405b is formed on the front surface of the epitaxial structure, that is, after the second metal electrode 405b is formed on the insulating layer 411, an adhesive material 413 is formed on the second metal electrode 405b, a length of the adhesive material 413 is less than or equal to a length of the second metal electrode 405b to prevent the light emitting hole from being blocked, then a transparent substrate 414 is formed on the adhesive material 12, and the substrate 401 is removed. By removing the substrate 401, the back surface of the first reflective layer 402 is exposed.

As shown in fig. 32, in the present embodiment, after the back surface of the first reflective layer 402 is exposed, by forming the insulating layer 411 on the back surface of the first reflective layer 402, the insulating layer 411 completely covers the back surface of the first reflective layer 402.

As shown in fig. 33, in steps S34 to S35, the first electrode 405 and the second electrode 412 are formed on the back surface of the first reflective layer 402 when the first electrode 405 and the second electrode 412 are formed.

As shown in fig. 33, in the present embodiment, when forming the first electrode 405, the bottom insulating layer 411 of the first trench 407a is removed first, and then the second metal electrode 405b is formed on the insulating layer 411 on the back surface of the first reflective layer 402, and the second metal electrode 405b is connected to the second metal electrode 405b in the first trench 407 a. The second metal electrode 405b on the insulating layer 411 positioned at the back of the first reflective layer 402 is far away from the vertical projection region of the first light emitting unit 409. In this embodiment, the second metal electrode 405b on the insulating layer 411 on the back of the first reflective layer 402 is connected to the second metal electrode 405b on the second reflective layer 404 through the second metal electrode 405b of the first trench 407a, then connected to the first metal electrode 405a, and then connected to the second metal electrode 405b in the second trench 407b through the first metal electrode 405a, and since the first light emitting unit 409 and the second light emitting unit 410 are connected through the first electrode 405, that is, connected through the first metal electrode 405a and the second metal electrode 405b, the first electrode 405 and the second reflective layer 404 are connected, and a common anode is formed. In the present embodiment, a portion of the second metal electrode 405b is located on the insulating layer 411 of the vertical projection region of the first light emitting unit 409 and the second light emitting unit 410.

As shown in fig. 33, in the present embodiment, when forming the second electrode 412, a portion of the insulating layer 411 on the back surface of the first reflective layer 402 in the vertical projection region of the first light emitting unit 409 and the second light emitting unit 410 is removed, and then the second electrode 412 is formed on the back surface of the first reflective layer 402 without the insulating layer 411, that is, the second electrode 412 is in contact with the first reflective layer 402. The second electrode 412 is located between the insulating layers 411, and two ends of the second electrode 412 are spaced from the second metal electrode 405b, or the second electrode 412 is located between the first electrodes 405, and two ends of the second electrode 412 are spaced from the first electrodes 405.

As shown in fig. 33, in the present embodiment, the material of the first electrode 405 may be Au, Pd, Ge and their alloys, for example. The material of the second electrode 412 may be, for example, Au, Pd, Ge, and alloys thereof. In some embodiments, the first electrode 405 or the second electrode 412 can be formed, for example, by evaporation or sputtering.

As shown in fig. 33, in the present embodiment, the vcsel has a front light emitting structure, and the front transparent substrate is bonded and then the back substrate is directly removed for a back process, without removing the transparent substrate again, the bonding frequency is 1 time, and the first electrode and the second electrode are disposed on the same surface, thereby avoiding wire bonding, saving process steps, and facilitating combination with other optical elements.

In some embodiments, as shown in fig. 34, another method for fabricating a vertical cavity surface emitting laser can be further provided, including,

s41: providing a substrate;

s42: forming an epitaxial structure on the substrate, wherein the epitaxial structure comprises a first reflecting layer, an active layer and a second reflecting layer;

s43: forming a plurality of first trenches on the epitaxial structure, wherein the plurality of first trenches penetrate through the epitaxial structure;

s44: forming a plurality of second grooves among the plurality of first grooves, penetrating the second reflecting layer and the active layer to divide the epitaxial structure into a plurality of light-emitting sub-units;

s45: forming an insulating layer in the plurality of first trenches and the second trenches;

s46: forming a first electrode on a back surface of the first reflective layer;

s47: and forming a plurality of second electrodes in the plurality of first grooves and the plurality of second grooves.

As shown in fig. 35, in step S41, a substrate 501 is provided first, then a first reflective layer 502 is formed on the substrate 501, an active layer 503 is formed on the first reflective layer 502, and a second reflective layer 504 is formed on the active layer 503. The first reflective layer 501, the active layer 502, and the second reflective layer 503 form an epitaxial structure. In this embodiment, the substrate 501 may be any semi-insulating material or P-type doped semiconductor substrate suitable for forming a vertical cavity surface emitting laser, the first reflective layer 502 may be a P-type bragg reflector, the active layer 503 includes a stacked quantum well composite structure composed of GaAs and AlGaAs or InGaAs and AlGaAs materials, the active layer 503 is used for converting electrical energy into optical energy, and the second reflective layer 504 may be an N-type bragg reflector

As shown in fig. 35, a plurality of first metal electrodes 505a are further formed on the second reflective layer 504, and the first metal electrodes 505a can be used as a reference for photolithography calibration in subsequent processes, so as to prepare a vertical cavity surface emitting laser with higher precision, and at the same time, the first metal electrodes 505a can also be used as metal contact pads for subsequent second electrodes. The shape of the first metal electrode 505a is shown in fig. 3.

As shown in fig. 36, in step S42, after the first metal electrode 505a is formed, a patterned photoresist layer 506 is first formed on the second reflective layer 504, the patterned photoresist layer 506 covers the first metal electrode 505a, and the patterned photoresist layer 506 exposes a portion of the second reflective layer 504, and then the second reflective layer 504 is etched downward according to the patterned photoresist layer 506 to form a plurality of trenches. The direction of the arrow in fig. 36 indicates the etching direction.

As shown in fig. 37, in the present embodiment, etching is performed downward from the second reflective layer 504 by an etching process to form a plurality of first trenches 507a and a plurality of second trenches 507 b. The first trench 507a penetrates through the epitaxial structure, and the first trench 507a exposes the substrate 501, that is, the first trench 507a is etched from top to bottom in sequence to form the second reflective layer 504, the active layer 503 and the first reflective layer 502. The second trench 507b is formed by sequentially etching the second reflective layer 504 and the active layer 503 from top to bottom, i.e., the second trench 507b exposes the surface of the first reflective layer 502, thereby dividing the second reflective layer 504 into a plurality of portions. In this embodiment, the width of the first trench 507a is greater than the width of the second trench 507b, the width of the first trench 507a is 3-10 um, and the width of the second trench 507b is 1-5 um. The structure of the first trench 507a and the second trench 507b can be seen in fig. 5A.

As shown in fig. 38, in step S43, after forming the plurality of trenches, it is also necessary to form a current confinement layer 508 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 508 in the second reflective layer 504. In the present embodiment, the sidewalls of the first trench 507a and the second trench 507b are oxidized to form a plurality of current confinement layers 508 in the second reflective layer 504.

As shown in fig. 38, in some embodiments, the current confinement layer 508 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 38, a first mesa structure 509a, a second mesa structure 509b, a third mesa structure 510a and a fourth mesa structure 510b are formed by the first trench 507a and the second trench 507 b. The first mesa structure 509a, the second mesa structure 509b, the third mesa structure 510a and the fourth mesa structure 510b are used to form a light emitting sub-unit, the first mesa structure 509a and the second mesa structure 509b are used to form a first light emitting unit 509, and the third mesa structure 510a and the fourth mesa structure 510b are used to form a second light emitting unit 510. The first light emitting unit 509 and the second light emitting unit 510 will be described later.

As shown in fig. 38, in step S33, after the current confinement layer 508 is formed, an insulating layer 511 is formed in the trench. In the present embodiment, a part of the insulating layer 511 is located in the first trench 507a, and a part of the insulating layer 511 is located in the second trench 507 b. In the present embodiment, the insulating layer 511 in the middle of the first trench 507a is taken as an example for illustration, a portion of the insulating layer 511 is located on the bottom and the sidewall of the first trench 507a, and the insulating layer 511 extends to the second reflective layer 504 along the sidewall of the first trench 507a and contacts the first metal electrode 505 a. Similarly, the insulating layer 511 located in the second trench 507b extends from the sidewall of the second trench 507b to the second reflective layer 504, and contacts the first metal electrode 505a, thereby realizing the insulating separation of the light emitting sub-units.

As shown in fig. 38, in the present embodiment, a partial insulating layer 511 is located on the second reflective layer 504 and is in contact with the first metal electrode 505a, the partial insulating layer 511 is located on the sidewalls of the second reflective layer 504 and the active layer 503, and the partial insulating layer 511 is located on the substrate 501. Note that the insulating layer 511 on the substrate 501 cannot be defined as being located in the active layer 503 or the second reflective layer 504 or the first reflective layer 502. The current confinement layer 508 may be defined, for example, to be located within the second reflective layer 504.

As shown in fig. 38, the material of the insulating layer 511 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 511 may be 100 nm to 300nm, and the insulating layer 511 may protect the current confinement layer 508 and may also effectively isolate the adjacent mesa structures. In the present embodiment, the insulating layer 511 can be formed by, for example, chemical vapor deposition.

As shown in fig. 38, after the insulating layer 511 is formed, the first mesa structure 509a may be defined as a first light emitting sub-unit, and the second mesa structure 509b may be defined as a second light emitting sub-unit, the first light emitting sub-unit and the second light emitting sub-unit being separated by the insulating layer 511 in the second trench 507 b. Similarly, the third mesa structure 510a is defined as a third light emitting sub-unit, the fourth mesa structure 510b is defined as a fourth light emitting sub-unit, and the third light emitting sub-unit and the fourth light emitting sub-unit are separated by the insulating layer 511 in the second trench 507 b. In the present embodiment, the first light emitting subunit and the second light emitting subunit are defined as a first light emitting unit 509, the third light emitting subunit and the fourth light emitting subunit are defined as a second light emitting unit 510, and the first light emitting unit 509 and the second light emitting unit 510 are isolated by a mesa structure in between.

As shown in fig. 39, in step S44, a second metal electrode 505b is first formed in the first trench 507a and the second trench 507b to connect the second metal electrode 505b with the first metal electrode 505a, so as to form the second electrode 505.

As shown in fig. 39, in the present embodiment, the second metal electrode 505b is formed on the insulating layer 511, that is, a portion of the second metal electrode 505b is located on the insulating layer 511 in the first trench 507a, a portion of the second metal electrode 505b is located on the insulating layer 511 in the second trench 507b, a portion of the second metal electrode 505b is located on the insulating layer 511 on the second reflective layer 504, and a portion of the second metal electrode 505b is also located on the first metal electrode 505a and forms the second electrode 505 with the first metal electrode 505 a. The second metal electrode 505b is aligned with the first metal electrode 505a, i.e. the second metal electrode 505b does not cover or block the light emitting hole, i.e. is located at the periphery of the light emitting hole.

As shown in fig. 38 to 39, in the present embodiment, the first emission unit 510 includes two light emitting sub-units therein, the two light emitting sub-units are connected by the second metal electrode 505b, and the two light emitting sub-units have the same structure. The present embodiment is described by taking one of the light emitting sub-units as an example. In this embodiment, each of the light emitting sub-units includes, from bottom to top, an active layer 503, a second reflective layer 504, a first metal electrode 505a and a second metal electrode 505b, a current confinement layer 508 is formed in the second reflective layer 504, the current confinement layer 508 is in contact with a sidewall of the light emitting sub-unit (the first mesa structure 509a) and extends into the light emitting sub-unit, that is, the current confinement layer 508 extends from the sidewall of the second reflective layer 504 into the second reflective layer 504. The current confinement layer 508 within the light-emitting subcell is a ring structure and a light-emitting aperture is defined by the current confinement layer 508.

As shown in fig. 38-39, in the present embodiment, in the light emitting subunit (i.e. the first mesa structure 509a), the first end of the current confinement layer 508 contacts the sidewall of the second reflective layer 504, the second end is located in the second reflective layer 504 and is flush with the inner diameter of the first metal electrode 505a, or the second end extends into the inner diameter of the first metal electrode 505a, i.e. the first metal electrode 505a is located at the outer periphery of the light emitting hole, so that the later formed second electrode does not block the light emitting hole.

As shown in fig. 38 to 39, in the present embodiment, a second trench 507b is formed between the first mesa structure 509a and the second mesa structure 509b, a second metal electrode 505b is formed in the second trench 507b, and the second metal electrode 505b is connected to the first metal electrodes 505b on the first mesa structure 509a and the second mesa structure 509b, so as to connect the first mesa structure 509a and the second mesa structure 509b, that is, the first mesa structure 509a and the second mesa structure 509b are connected to the first metal electrode 505a through the second metal electrode 505b, that is, the first light emitting subunit is connected to the second light emitting subunit. Similarly, the second light emitting unit 510 has the same structure as the first light emitting unit 509, and the second light emitting unit 510 is not illustrated in this embodiment.

As shown in fig. 39, in the present embodiment, a mesa structure is formed between the first light emitting unit 509 and the second light emitting unit 510, and an insulating layer 511 is formed on the mesa structure, and the insulating layer 511 is connected to the insulating layer in the second trench 507b, so that the first light emitting unit 509 and the second light emitting unit 510 are insulated from each other, and thus the second electrode 505 in the first light emitting unit 509 and the second electrode 505 in the second light emitting unit 510 are separated and independent from each other.

As shown in fig. 40, in the present embodiment, after forming the second metal electrode 505b on the front surface of the epitaxial structure, that is, after forming the second metal electrode 505b on the insulating layer 511, an adhesive material 513 is formed on the second metal electrode 505b, a length of the adhesive material 513 is less than or equal to a length of the second metal electrode 505b to prevent the light emitting hole from being blocked, then a transparent substrate 514 is formed on the adhesive material 513, and the substrate 501 is removed. By removing the substrate 501, the back surface of the first reflective layer 502 is exposed.

As shown in fig. 40, in the present embodiment, after the back surface of the first reflective layer 502 is exposed, an insulating layer 511 is then formed on the back surface of the first reflective layer 502, and the insulating layer 511 completely covers the back surface of the first reflective layer 502.

As shown in fig. 41, in the present embodiment, when forming the second electrode 505, the bottom insulating layer 511 of the first trench 407a is first removed, and then the second metal electrode 505b is formed on the insulating layer 511 on the back surface of the first reflective layer 502, and the second metal electrode 505b is connected to the second metal electrode 505b in the first trench 507 a. The second metal electrode 505b on the insulating layer 511 positioned at the rear surface of the first reflective layer 502 is far away from the vertical projection region of the first light emitting unit 509. In the present embodiment, the second metal electrode 505b on the insulating layer 511 located on the back surface of the first reflective layer 502 is connected to the second metal electrode 505b on the second reflective layer 504 through the second metal electrode 505b of the first trench 507a, then connected to the first metal electrode 505a, and then connected to the second metal electrode 505b in the second trench 507b through the first metal electrode 505a, thereby achieving connection of two light emitting sub-units within the first light emitting unit 509, but due to the existence of the intermediate mesa structure, the first light emitting unit 509 and the second light emitting unit 510 are separated, thereby forming a plurality of mutually independent second electrodes 505. In the present embodiment, the second metal electrode 505b on the insulating layer 511 positioned at the rear surface of the first reflective layer 502 is not within the vertical projection region of the first light emitting unit 509.

As shown in fig. 41, in the present embodiment, the first electrode 512 is located on the vertical projection area of the first light emitting unit 509 and the second light emitting unit 510, and the first electrode 512 is in contact with the first reflective layer 502, and the first electrode 512 and the first reflective layer 502 form a common anode. The first electrode 512 is located between the insulating layers 511, and two ends of the first electrode 512 are spaced from the second metal electrode 505b, or the first electrode 512 is located between the second electrodes 505, and two ends of the first electrode 512 are spaced from the second electrode 505.

As shown in fig. 41, in the present embodiment, the material of the first electrode 512 can be Au, Pd, Ge and their alloys. The material of the second electrode 505 may be, for example, Au, Pd, Ge, and alloys thereof. In some embodiments, the first electrode 512 or the second electrode 505 can be formed, for example, by evaporation or sputtering.

As shown in fig. 42-43, fig. 43 is shown as a bottom view of fig. 42, and fig. 43 is primarily shown as the positional relationship of the first electrode 512 and the second electrode 505.

As shown in fig. 42, fig. 42 is different from fig. 41 in that a through hole is formed between the first light emitting unit 509 and the second light emitting unit 510, and the through hole penetrates through the epitaxial structure to isolate the first light emitting unit 509 from the second light emitting unit 510. The first light emitting unit 509 and the second light emitting unit 510 are symmetrical about the through hole, so the vertical cavity surface emitting laser is described in this embodiment by taking the first light emitting unit 509 as an example.

As shown in fig. 42-43, in the present embodiment, the first light emitting unit 509 includes two light emitting sub-units, and the two light emitting sub-units are connected through the first metal electrode 505a and the second metal electrode 505 b. The second electrode 505 in the first light emitting unit 509 and the second electrode 505 in the second light emitting unit 510 are separated from each other, and thus a plurality of second electrodes 505, or a plurality of cathodes, are formed.

As shown in fig. 42 to 43, in the present embodiment, the first electrode 512 in the first light emitting unit 509 and the first electrode 512 in the second light emitting unit 510 are connected while forming a common anode by being in contact with the first reflective layer 502.

As shown in fig. 41 to 42, in the present embodiment, the vcsel has a front light emitting structure, and the front transparent substrate is bonded and then the back substrate is directly removed for a back process, without removing the transparent substrate again, the number of bonding times is 1, and the first electrode and the second electrode are disposed on the same surface, thereby avoiding wire bonding, saving the process steps, and being easily combined with other optical elements.

As shown in fig. 44, in some embodiments, another method for manufacturing a vertical cavity surface emitting laser may be provided, which may be used to form a back side emitting structure. In this embodiment, a laser emitting light upward is referred to as a front emission structure, and a laser emitting light downward is referred to as a back emission structure.

As shown in fig. 44, the method of manufacturing the vertical cavity surface emitting laser includes,

s51: providing a substrate;

s52: forming a first reflective layer on a second surface of the substrate;

s53: forming a plurality of light emitting units on the first reflective layer, each light emitting unit including a plurality of light emitting sub-units, first grooves formed between the plurality of light emitting units, the first grooves exposing the substrate, each light emitting sub-unit including a light emitting hole;

s54: forming an insulating layer in the first trench;

s55: forming a plurality of first electrodes on the plurality of light emitting units, wherein the first electrodes are connected with the plurality of light emitting units, the light emitting sub-units in each light emitting unit are connected through the first electrodes to form a common anode, and the first electrodes cover the light emitting holes;

s56: and forming a plurality of second electrodes on two sides of the light-emitting unit, wherein the second electrodes are in contact with the first reflecting layer.

As shown in fig. 45, in step S51, a substrate 601 is first provided, where the substrate 601 includes a first surface 601a and a second surface 601 b. The first surface 601a is disposed opposite to the second surface 601b, and the first surface 601a is defined as a front surface of the substrate 601 and the second surface 601b is defined as a back surface of the substrate 601. In this embodiment, the substrate 601 may be any semi-insulating material suitable for forming a vertical cavity surface emitting laser, the first reflective layer 602 may be an N-type bragg mirror, the active layer 603 includes a stacked quantum well composite structure composed of GaAs and AlGaAs, or a stacked arrangement of InGaAs and AlGaAs materials, the active layer 603 is configured to convert electrical energy into optical energy, and the second reflective layer 604 may be a P-type bragg mirror. The first reflective layer 602 is formed on the second surface 601b of the substrate 601.

As shown in fig. 46, a plurality of first metal electrodes 605a are further formed on the second reflective layer 604, and the first metal electrodes 605a can be used as a reference for photolithography calibration in subsequent processes, so as to prepare a vertical cavity surface emitting laser with high precision, and the first metal electrodes 605a can also be used as metal contact pads of subsequent first electrodes.

As shown in fig. 47, after forming the first metal electrode 605a, a patterned photoresist layer 606 is first formed on the second reflective layer 604, the patterned photoresist layer 606 covers the first metal electrode 605a, and the patterned photoresist layer 606 exposes a portion of the second reflective layer 604, and then the second reflective layer 604 is etched downward according to the patterned photoresist layer 606 to form a plurality of trenches. The direction of the arrow in fig. 47 indicates the etching direction.

As shown in fig. 48, in the present embodiment, the first trench 607a, the second trench 607b and the third trench 607c are formed by etching from the second reflective layer 604. The structure of the first trench 607a, the second trench 607b and the third trench 607c can be seen in fig. 5A, the first trench 607a is used for separating the light emitting cells, and the second trench 607b and the third trench 607c are used for separating the light emitting sub-cells. As shown in fig. 48, in the present embodiment, the width of the first trench 607a may be greater than the width of the second trench 607b, and the width of the second trench 607b may be equal to the width of the third trench 607 c. The width 3 ~ 10um of first slot 607a, the width 1 ~ 5um of second slot 607b, the width 1 ~ 5um of third slot 607c form the mesa structure between first slot 607a and the second slot 607b, the mesa structure that forms between second slot 607b and the third slot 607c, the mesa structure is used for forming the luminescence subunit. The width of the table-shaped structure is 10-100 um.

As shown in fig. 48, in the present embodiment, the depth of the first trench 607a is greater than the depth of the second trench 607b or the third trench 607c, and the first trench 607a etches a portion of the first reflective layer 602, the active layer 603, and the second active layer 604 from bottom to top, so that the first trench 607a divides the first reflective layer 602 into a plurality of portions. The second trench 607b and the third trench 607c have the same depth, i.e., the second reflective layer 604 and the active layer 603 are partially etched from bottom to top.

As shown in fig. 49, in the present embodiment, after forming a plurality of trenches, it is also necessary to form a current confinement layer 608 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 608 in the second reflective layer 604. In the present embodiment, a plurality of current confinement layers 608 are formed in the second reflective layer 604 by oxidizing the sidewalls of the first trench 607a, the second trench 607b, and the third trench 607 c.

As shown in fig. 49, in the present embodiment, the first mesa structure 609a is defined as a first light emitting sub-unit, and the second mesa structure 609b is defined as a second light emitting sub-unit. The first mesa structure 609a and the second mesa structure 609b have the same structure, and the first mesa structure 609a is taken as an example for explanation in this embodiment. The first mesa structure 609a includes an active layer 603, a second reflective layer 604 and a first metal electrode 605a from bottom to top, a current confinement layer 608 is formed in the second reflective layer 604, and the current confinement layer 608 contacts with a sidewall of the first mesa structure 609a and extends into the first mesa structure 609 a. The current confinement layer 608 in the first mesa-shaped structure 609a is a ring-shaped structure, and a light-emitting hole is defined by the current confinement layer 608.

As shown in fig. 49, in the present embodiment, the first mesa structure 609a has the same structure as the second mesa structure 609b, and thus the first light emitting sub-unit has the same structure as the second light emitting sub-unit, thereby defining the first light emitting sub-unit and the second light emitting sub-unit as the first light emitting unit 609. In the present embodiment, the third mesa structure 610a is defined as a third light emitting sub-unit, the fourth mesa structure 610b is defined as a fourth light emitting sub-unit, and the third mesa structure 610a has the same structure as the fourth mesa structure 610b, thereby defining a combination of the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 610. The first light emitting cell 609 and the second light emitting cell 610 are separated by a first trench 607 a.

As shown in fig. 49, in the present embodiment, the outer diameter of the first metal electrode 605a on the first mesa structure 609a has a certain distance from the second trench 607b or the third trench 607c, for example, the distance between the left side of the first metal electrode 605a and the side wall of the third trench 607c is D1, the distance D1 may range from 1 um to 5um, the distance between the right side of the first metal electrode 605a and the side wall of the second trench 607b is D2, and the distance D2 may range from 1 um to 5 um.

As shown in fig. 49, in some embodiments, the current confinement layer 608 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 48 to 49, in the present embodiment, the first groove 607a is defined to be located outside the first light emitting cell 609 or the second light emitting cell 610. Similarly, the insulating layer formed in the first trench 607a is also located outside the first light emitting cell 609 or the second light emitting cell 610.

As shown in fig. 50, in step S54, after the current confinement layer 608 is formed, an insulating layer 611 is formed within the trench. In the present embodiment, a part of the insulating layer 611 is located in the first trench 607a, a part of the insulating layer 611 is located in the second trench 607b, and a part of the insulating layer 611 is located in the third trench 607 c. In the embodiment, the insulating layer 611 in the first trench 607a is taken as an example for illustration, a portion of the insulating layer 611 is located on the bottom and the sidewall of the first trench 607a, and the insulating layer 611 extends to the second reflective layer 604 along the sidewall of the first trench 607a and contacts the first metal electrode 605 a. Thereby insulating the first light emitting unit 609 from the second light emitting unit 610. Similarly, the first light-emitting subunit and the second light-emitting subunit are insulated and separated by an insulating layer 611, and the third light-emitting subunit and the fourth light-emitting subunit are insulated and separated by an insulating layer 611.

As shown in fig. 50, in the present embodiment, a partial insulating layer 611 is located on the second reflective layer 604 and is in contact with the first metal electrode 605a, the partial insulating layer 611 is located on the sidewalls of the second reflective layer 604 and the active layer 603, and the partial insulating layer 611 is located on the substrate 601. Note that the insulating layer 611 located on the substrate 101 cannot be defined as being located in the active layer 603 or the second reflective layer 604 or the first reflective layer 602. The current confinement layer 608 can be defined, for example, to be within the second reflective layer 604.

As shown in fig. 50, the material of the insulating layer 611 may be silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 111 may be 100 nm to 300nm, and the insulating layer 611 may protect the current confinement layer 608 and may also effectively isolate the adjacent mesa structures. In the present embodiment, the insulating layer 611 may be formed, for example, by chemical vapor deposition.

As shown in fig. 51, in steps S5-S6, after the insulating layer 611 is formed, a metal layer is formed on the mesa structure to form a plurality of first electrodes 605 and second electrodes 612.

As shown in fig. 51, in this embodiment, when forming the first electrode 605, it is necessary to form the second metal electrode 605b first, and form the first electrode 605 by the first metal electrode 605a and the second metal electrode 605 b. In the present embodiment, the second metal electrode 605b is formed in the first trench 607a and the second trench 607b, and the second metal electrode 605b is further formed on the second reflective layer 604, i.e. on the insulating layer 609 and the first metal electrode 605a, and further between the first metal electrodes 605 a. Therefore, the second metal electrode 605b and the first metal electrode 605a form the first electrode 605, the first light emitting unit 609 and the second light emitting unit 610 are connected through the second metal electrode 605b, and the first light emitting unit 609 and the second light emitting unit 610 are also connected through the first electrode 605. The reflectivity of the second reflective layer 604 is greater than that of the first reflective layer 602, so that light formed by the active layer 603 exits through the substrate 601, thereby forming a back emission structure.

As shown in fig. 51, in the present embodiment, the first electrode 605 is formed by contacting the second reflective layer 604, and thus forms a common anode, i.e., the first light emitting unit 609 and the second light emitting unit 610 share one electrode.

As shown in fig. 51, in the present embodiment, the plurality of second electrodes 612 are disposed on the mesa structures at two ends, that is, the plurality of second electrodes 612 are disposed at two sides of the first light emitting unit 609 and the second light emitting unit 610, respectively. In the embodiment, taking the right second electrode 612 as an example, the second electrode 612 is located on the mesa structure, a portion of the second electrode 612 is located on the second reflective layer 604 and covers the light emitting hole formed by the current limiting layer 608, a portion of the second electrode 612 extends along the sidewall of the mesa structure to the first reflective layer 602 and contacts the first reflective layer 602, and the second electrode 612 completely covers the sidewall of the mesa structure. The second electrodes 612 at both ends are in contact with the first reflective layer 602, and since the first trench 607a divides the first reflective layer 602 into two parts, which are insulated from each other, the second electrodes 612 at both ends are insulated from each other independently, so that a plurality of second electrodes 612, which can be said to form a plurality of cathodes, are formed.

As shown in fig. 51, in this embodiment, when the vcsel is used, the first electrode 605 and the second reflective layer 604 form a common anode, the second electrodes 612 respectively control the light emitting units, the second electrodes 612 are insulated and separated from each other to form cathodes, a current is applied to the first electrode 605 and the second electrode 612, the current passes through the second reflective layer 604 and enters the active layer 603, the current cannot pass through the current confinement layer 608 due to the presence of the active current confinement layer 608, and therefore only stimulated emission can be generated in the light emitting hole, a waveguide structure is formed, and laser oscillation is formed in the resonant cavity formed by the second reflective layer 604 and the first reflective layer 602, and the reflectivity of the second reflective layer 604 is greater than that of the first reflective layer 602, so that light formed by the active layer 603 exits through the substrate 601, and thus a back emission structure is formed.

As shown in fig. 51, in this embodiment, the vcsel can reduce the area of the light-emitting unit by forming the common anode, and can also address independently, with a short interconnection length. The vertical cavity surface emitting laser can also select an N-MOS driver with smaller volume and higher speed, and can also improve the application frequency of the device. Meanwhile, the anode and the cathode are arranged on the same side of the substrate, and the chip can be reversely mounted without routing.

As shown in fig. 52, in some embodiments, another fabrication method of a vertical cavity surface emitting laser may be provided, by which a back surface emitting structure may be formed, the fabrication method including,

s61: providing a substrate;

s62: forming a first reflective layer on a second surface of the substrate;

s63: forming a plurality of light emitting units on the first reflective layer, each light emitting unit comprising a plurality of light emitting sub-units, each light emitting sub-unit comprising a light emitting hole;

s64: forming an insulating layer between the plurality of light emitting units;

s65: forming a plurality of first electrodes on two sides of the plurality of light emitting units, wherein the plurality of first electrodes are in contact with the first reflecting layer to form a common anode;

s66: and forming a plurality of second electrodes on the plurality of light-emitting units, wherein the light-emitting subunits in each light-emitting unit are connected through the second electrodes, and the plurality of second electrodes cover the light-emitting holes.

As shown in fig. 53, in step S61, a substrate 701 is first provided, where the substrate 701 includes a first surface 701a and a second surface 701 b. The first surface 701a and the second surface 701b are disposed opposite to each other, and the first surface 701a is defined as a front surface of the substrate 701, and the second surface 701b is defined as a back surface of the substrate 701. In this embodiment, the substrate 701 may be any semi-insulating material suitable for forming a vertical cavity surface emitting laser, the first reflective layer 702 may be a P-type bragg mirror, the active layer 703 includes a stacked quantum well composite structure and is formed by stacking GaAs and AlGaAs or InGaAs and AlGaAs materials, the active layer 703 is used for converting electrical energy into optical energy, and the second reflective layer 704 may be an N-type bragg mirror. A first reflective layer 702 is formed on the second surface 701b of the substrate 701.

As shown in fig. 54, a plurality of first metal electrodes 705a are further formed on the second reflective layer 704, and the first metal electrodes 705a 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 at the same time, the first metal electrodes 705a can also be used as metal contact pads for a subsequent second electrode. The shape of the first metal electrode 705a is shown in FIG. 3.

As shown in fig. 55, after forming the first metal electrode 705a, a patterned photoresist layer 706 is formed on the second reflective layer 704, the patterned photoresist layer 706 covers the first metal electrode 705a, and the patterned photoresist layer 706 exposes a portion of the second reflective layer 704, and then the second reflective layer 704 is etched downward according to the patterned photoresist layer 706 to form a plurality of trenches. The direction of the arrow in fig. 55 indicates the etching direction.

As shown in fig. 55 to 56, in the present embodiment, the first trench 707a, the second trench 707b, and the third trench 707c are formed by etching from the second reflective layer 704 downward to the surface of the first reflective layer 702 through an etching process. The structure of the first trench 707a, the second trench 707b and the third trench 707c can be seen in fig. 5A, the first trench 707a is used to separate the light emitting cells, and the second trench 707b and the third trench 707c are used to separate the light emitting sub-cells.

As shown in fig. 56, in the present embodiment, the width of the first groove 707a may be, for example, larger than the width of the second groove 607b, and the width of the second groove 707b may be, for example, equal to the width of the third groove 707 c. The width of first slot 707a is 3 ~ 10um, the width of second slot 707b is 1 ~ 5um, the width of third slot 707c is 1 ~ 5um, forms the platform type structure between first slot 707a and the second slot 707b, the platform type structure that forms between second slot 707b and the third slot 707c, the platform type structure is used for forming luminous subunit, the width of platform type structure is at 10 ~ 100 um.

As shown in fig. 56, in the present embodiment, the first trench 707a, the second trench 707b and the third trench 707c have the same depth, and the first trench 707a etches the active layer 703 and the second active layer 704 from bottom to top, so that the first trench 707a, the second trench 707b and the third trench 707c divide the second reflective layer 704 into a plurality of portions.

As shown in fig. 57, in the present embodiment, after forming a plurality of trenches, it is also necessary to form a current confinement layer 708 in the mesa structure to form a light emitting hole. In the present embodiment, the sidewall of the trench is oxidized by high temperature oxidation of highly doped aluminum to form a plurality of current confinement layers 708 in the second reflective layer 704. In the present embodiment, a plurality of current confinement layers 708 are formed within the second reflective layer 704 by oxidizing the sidewalls of the first trench 707a, the second trench 707b, and the third trench 707 c.

As shown in fig. 57, in the present embodiment, the first mesa structure 709a is defined as a first light emitting subunit, and the second mesa structure 709b is defined as a second light emitting subunit. The first mesa structure 709a and the second mesa structure 709b have the same structure, and the first mesa structure 709a is taken as an example for the description of the present embodiment. The first mesa structure 709a includes, from bottom to top, an active layer 703, a second emission layer 704 and a first metal electrode 705a, a current confinement layer 708 is formed in the second emission layer 704, and the current confinement layer 708 is in contact with a sidewall of the first mesa structure 709a and extends into the first mesa structure 709 a. The current confinement layer 708 in the first mesa structure 709a is a ring-shaped structure, and a light emission hole is defined by the current confinement layer 708.

As shown in fig. 57, in the present embodiment, the first mesa structure 709a has the same structure as the second mesa structure 709b, and thus the first light emitting subunit and the second light emitting subunit have the same structure, thereby defining the first light emitting subunit and the second light emitting subunit as the first light emitting unit 709. In the present embodiment, a third mesa structure 710a is defined as a third light emitting sub-unit, a fourth mesa structure 710b is defined as a fourth light emitting sub-unit, and the third mesa structure 710a has the same structure as the fourth mesa structure 710b, thereby defining a combination of the third light emitting sub-unit and the fourth light emitting sub-unit as the second light emitting unit 710. The first light emitting sub-unit 709 and the second light emitting unit 710 are separated by a first groove 707 a.

As shown in fig. 57, in the present embodiment, the outer diameter of the first metal electrode 705a on the first mesa structure 709a has a certain distance from the second trench 707b or the third trench 707c, for example, the distance between the left side of the first metal electrode 705a and the side wall of the third trench 707c is D1, the distance D1 may range from 1 um to 5um, the distance between the right side of the first metal electrode 705a and the side wall of the second trench 707b is D2, and the distance D2 may range from 1 um to 5 um.

As shown in fig. 57, in some embodiments, the current confinement layer 708 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, and the oxidation confinement type current confinement structure is used in this embodiment.

As shown in fig. 56 to 57, in the present embodiment, the first groove 707a is defined to be located outside the first light emitting unit 709 or the second light emitting unit 710. Similarly, the insulating layer formed in the first trench 707a is also located outside the first light emitting unit 709 or the second light emitting unit 710.

As shown in fig. 58, in step S64, after the current confinement layer 708 is formed, an insulating layer 711 is formed in the trench. In this embodiment, a part of the insulating layer 711 is located in the first trench 707a, a part of the insulating layer 711 is located in the second trench 707b, and a part of the insulating layer 711 is located in the third trench 707 c. In this embodiment, the insulating layer 711 in the first trench 707a is taken as an example, a portion of the insulating layer 711 is located on the bottom and the sidewall of the first trench 707a, and the insulating layer 711 extends along the sidewall of the first trench 707a to the second reflective layer 704 and contacts the first metal electrode 705 a. Thereby insulating the first light emitting unit 709 from the second light emitting unit 710. Similarly, the first light emitting subunit and the second light emitting subunit are insulated and separated by the insulating layer 711, and the third light emitting subunit and the fourth light emitting subunit are insulated and separated by the insulating layer 711.

As shown in fig. 58, in the present embodiment, a part of the insulating layer 711 is located on the second reflective layer 704 and is in contact with the first metal electrode 705a, a part of the insulating layer 711 is located on the sidewalls of the second reflective layer 704 and the active layer 703, and a part of the insulating layer 711 is located on the first reflective layer 702. Note that the insulating layer 711 provided over the first reflective layer 702 cannot be defined as being provided in the active layer 703 or the second reflective layer 704. The current confined layer 708 may be defined, for example, as being located within the second reflective layer 704.

As shown in fig. 58, the insulating layer 711 may be made of silicon nitride or silicon oxide or other insulating materials, the thickness of the insulating layer 711 may be 100 nm to 300nm, the insulating layer 711 may protect the current confinement layer 708, and may effectively isolate the adjacent mesa structures. In this embodiment, the insulating layer 711 can be formed by, for example, chemical vapor deposition.

As shown in fig. 58, in steps S65 to S66, after the insulating layer 711 is formed, a metal layer is formed on the mesa structure to form a plurality of first electrodes 712 and second electrodes 705.

As shown in fig. 58, in the present embodiment, the plurality of first electrodes 712 are located on the mesa structures at two ends, that is, the plurality of first electrodes 712 are respectively located at two sides of the first light emitting unit 709 and the second light emitting unit 710. In the embodiment, the first electrode 712 on the left side is taken as an example for description, the first electrode 712 is located on the mesa structure, a portion of the first electrode 712 is located on the second reflective layer 704 and covers the light emitting hole formed by the current limiting layer 708, a portion of the first electrode 712 extends onto the first reflective layer 702 along the sidewall of the mesa structure and contacts the first reflective layer 702, and the first electrode 712 completely covers the sidewall of the mesa structure. The first electrodes 712 at both ends are in contact with the first reflective layer 702, and thus the first electrodes 712 at both ends and the first reflective layer 702 form a common anode.

As shown in fig. 58, in this embodiment, when forming the second electrode 705, it is necessary to form the second metal electrode 705b first, and form the second electrode 705 by the first metal electrode 705a and the second metal electrode 705 b. A part of the second metal electrode 705b is formed on the second reflective layer 704, a part of the second metal electrode 705b is formed in the second trench 707b, and a part of the second metal electrode 705b is formed between the first metal electrodes 705a and connected to the first metal electrodes 705a to form the second electrode 705. The two light emitting sub-units in the first light emitting unit 709 are connected through the second metal electrode 705b, and the second metal electrode 705b covers the light emitting hole, or the second electrode 705 covers the light emitting hole. The first light emitting unit 709 and the second light emitting unit 710 are insulated and separated, and thus the plurality of second electrodes 705 are formed independently of each other, that is, a plurality of independent cathodes are formed.

As shown in fig. 58, in the present embodiment, when the vertical cavity surface emitting laser is used, the first electrode 712 forms a common anode with the first reflective layer 702, the plurality of second electrodes 705 control the plurality of light emitting cells, respectively, the plurality of second electrodes 705 are insulated and spaced from each other, form a plurality of cathodes, when a current is applied to the first electrode 712 and the second electrode 705, the current flows through the first reflective layer 702 and into the active layer 703, and the current cannot pass through the current confining layer 708 due to the presence of the current confining layer 708, and therefore, only stimulated emission can be generated in the light emitting hole, a waveguide structure is formed, and laser oscillation is generated in the resonant cavity formed by the second reflecting layer 704, the first reflecting layer 702, since the second electrode 705 blocks the light emitting hole, the reflectivity of the second reflective layer 704 is greater than that of the first reflective layer 702, light formed by the active layer 703 thus exits through the substrate 701, thus forming a back-emission structure.

As shown in fig. 58, in this embodiment, the vcsel can reduce the area of the light-emitting unit by forming the common anode, and can also address independently, with a short interconnection length. The vertical cavity surface emitting laser can also select an N-MOS driver with smaller volume and higher speed, and can also improve the application frequency of the device. Meanwhile, the anode and the cathode are arranged on the same side of the substrate, and the chip can be reversely mounted without routing.

As shown in fig. 59, the present embodiment also provides a light emitting device 10, wherein the light emitting device 10 includes a substrate 11 and a light emitting element 12 disposed on the substrate 11. The light emitting element 12 includes at least one vertical cavity surface emitting laser 13 therein, and the vertical cavity surface emitting laser 13 has any of the above-described structures.

In this embodiment, the VCSEL can be used as various light sources for light emission, and an array of VCSELs can also be used as a multi-beam light source. The vertical cavity surface emitting laser in the present embodiment can be used in image forming apparatuses including laser beam printers, copiers, and facsimile machines.

The vertical cavity surface emitting laser provided by the embodiment can be used for laser radar, infrared cameras, 3D depth recognition detectors and image signal processing.

In some embodiments, the VCSEL may also be used as a light source in optical communications, such as a laser in an optical transceiver module of a fiber optic module.

As shown in fig. 60, the present embodiment further provides a three-dimensional sensing device 20, in which the three-dimensional sensing device 20 includes a housing 21, a display device 22 disposed on the housing 21, and a time-of-flight module 23 disposed in the housing 21. In this embodiment, the three-dimensional sensing device 20 may be an electronic device such as a mobile phone, a tablet computer, a smart watch, and the like.

As shown in fig. 60, in the present embodiment, the display device 22 may be, for example, a display panel or a cover plate, and the display device 22 may also include a circuit responding to a touch operation performed on the display panel. The display panel may be a liquid crystal display panel, and in some embodiments, the display panel may also be a touch display screen.

As shown in fig. 60, in the present embodiment, the three-dimensional sensing device 20 may further include a time-of-flight module 23, where the time-of-flight module 23 is disposed in the housing 21 and is used for emitting and receiving light that can pass through the display device 22, so as to obtain the distance of the target object according to the time difference or the phase difference between the emitted and received light. In the present embodiment, the time-of-flight module 23 may be, for example, a flying camera module, which obtains the distance between the target object and the three-dimensional sensing device 20 by emitting light and receiving light reflected by the target object, so as to obtain an image with depth information of the target object. Accordingly, the display device 22 may be provided with a light-transmitting region corresponding to the time-of-flight module 23, the light-transmitting region being for allowing the time-of-flight module 230 to emit or receive light.

As shown in fig. 60, the time-of-flight module 23 may include a laser 231, an image sensor 232, and a photographing control module 233, where it should be noted that at least one vertical cavity surface emitting laser or at least one vertical cavity surface emitting laser array is disposed in the laser 231. When the laser 231 is turned on, the photographing control module 233 controls the image sensor 232 to capture an optical image corresponding to the target object, the optical image being formed based on light emitted from the laser 231 reflected to the image sensor 232 through the surface of the target object. Further, the image sensor 232 may be a Metal Oxide Semiconductor (MOS) sensor, the photographing control module 233 includes an Analog Front End (FE) and a pulse generator, the pulse generator sends a corresponding timing to control the laser 231 and the image sensor 232, and the timing of the laser 231 and the image sensor 232 is synchronized, after the light emitted from the laser 231 is emitted, the light encounters target objects at different distances, the time for the light to be reflected to the image sensor 232 is different, and the photographing control module 233 of the time-of-flight module 23 can calculate the distance from the surface of the target object to the image sensor 232 through time or signal phase difference.

As shown in fig. 60, in the present embodiment, the image sensor 232 measures the time from the laser chip to the target object of each pixel point, and then reflects the light back to the image sensor 232 according to the received laser light reflected by the target object. The optical filter 234 is disposed on the image sensor 232, and the optical filter 234 is used for collecting the reflected laser light and only allowing the laser light with the corresponding wavelength to pass through.

In summary, the invention provides a vertical cavity surface emitting laser and a manufacturing method and application thereof, the chip area of a light emitting unit can be reduced by forming a common anode and split cathode laser structure, and the vertical cavity surface emitting laser can select an N-MOS driver with smaller volume and higher speed, thereby improving the application efficiency of the device.

The above description is only a preferred embodiment of the present application and a description of the applied technical principle, and it should be understood by those skilled in the art that the scope of the present invention related to the present application is not limited to the technical solution of the specific combination of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the technical solutions formed by mutually replacing the above features with (but not limited to) technical features having similar functions disclosed in the present application.

Other technical features than those described in the specification are known to those skilled in the art, and are not described herein in detail in order to highlight the innovative features of the present invention.

Claims

1. A vertical cavity surface emitting laser includes,

a substrate;

a first reflective layer formed on a first surface of the substrate;

an insulating layer formed between the at least two light emitting cells;

a first electrode formed on a second surface of the substrate;

wherein each of the light-emitting sub-units comprises a light-emitting hole, and the second electrode surrounds the periphery of the light-emitting hole;

each light-emitting photon unit comprises an active layer and a second reflecting layer, wherein the active layer is formed on the first reflecting layer, and the second reflecting layer is formed on the active layer;

and a second groove is formed in each light-emitting photon unit, penetrates through the second reflecting layer and the active layer and is exposed to the first reflecting layer.

2. A vertical cavity surface emitting laser according to claim 1, wherein a first trench is formed between said at least two light emitting cells, said first trench being exposed to said first reflective layer.

3. A vertical cavity surface emitting laser according to claim 2, wherein a portion of said insulating layer is formed in said first trench.

4. A vertical cavity surface emitting laser according to claim 1, wherein a portion of said second electrode is formed in said second trench and extends along said second trench to said at least two light emitting sub-units on both sides.

5. A vertical cavity surface emitting laser according to claim 1, wherein a portion of said second electrode covers said insulating layer and is connected to said second reflecting layer.

6. A vertical cavity surface emitting laser according to claim 1, wherein said first electrode and said second electrode are located on opposite sides of said substrate.

7. A method of manufacturing a vertical cavity surface emitting laser includes,

providing a substrate;

forming a first reflective layer on a first surface of the substrate;

forming an insulating layer between the at least two light emitting units;

forming a first electrode on a second surface of the substrate;

8. A light emitting device, comprising,

a substrate;

a first reflective layer formed on a first surface of the substrate;

an insulating layer formed between the at least two light emitting cells;

a first electrode formed on a second surface of the substrate;