VCSEL (Vertical Cavity Surface Emitting Laser), preparation process and laser equipment

Abstract

The invention discloses a VCSEL laser, which comprises at least one light emitting array, and each light emitting array comprises at least one light emitting unit. Each light-emitting unit sequentially comprises a first electrode, a first Bragg reflector, an active region, a second Bragg reflector and a second electrode from bottom to top, a tunnel junction is arranged between the first Bragg reflector and the second Bragg reflector, and the second Bragg reflector is an N-type doped DBR. An N-type doped distributed Bragg reflector (N-DBR) is adopted as a second Bragg reflector, and the electro-optical conversion efficiency of the device is remarkably improved through optimization of carrier transport characteristics. Compared with the problem that the ohmic contact resistance is too high due to the fact that a traditional P-type DBR is limited by low hole mobility, the high electron mobility of an N-type material can effectively reduce the series resistance of a reflector area, and therefore Joule heat is greatly reduced.

Description

Technical Field

[0001] The present application relates to the field of semiconductor chips, and more specifically, to a VCSEL laser, a preparation process, and a laser device. Background Art

[0002] A vertical-cavity surface-emitting laser (VCSEL) is a semiconductor device that emits laser light perpendicular to the semiconductor substrate. Its core structure consists of two sets of distributed Bragg reflectors (DBRs) sandwiched between a quantum well active region. Compared to traditional edge-emitting lasers (EELs), this device, with its superior beam quality (nearly circularly symmetrical spot), small divergence angle (<30°), low power consumption, and ability to be integrated in two dimensions, has found widespread application in cutting-edge fields such as 3D sensing (facial recognition / lidar), high-speed optical communications (data center optical modules), and biomedical imaging.

[0003] Traditional VCSELs utilize an N-type doped DBR as the lower reflector and a P-type doped DBR as the upper reflector, with a P-type metal electrode deposited on the P-DBR surface. However, because the hole mobility of the P-type semiconductor material is significantly lower than the electron mobility of the N-type material, the P-DBR region exhibits inherent defects: high ohmic resistance causes additional heat loss, strong light absorption reduces the optical field confinement capability, and the heat accumulation effect couples with optical mode broadening, ultimately increasing the device's divergence angle, degrading beam quality, and reducing long-term reliability. These physical limitations have become key bottlenecks hindering breakthroughs in traditional VCSEL performance. Summary of the Invention

[0004] One advantage of the present application is that it provides a vertical cavity surface emitting laser, in which an N-type doped distributed Bragg reflector (N-DBR) is used as the second Bragg reflector, and the electro-optical conversion efficiency of the device is significantly improved by optimizing the carrier transport characteristics. Compared with the traditional P-type DBR, which is limited by the problem of excessively high ohmic contact resistance caused by low hole mobility, the high electron mobility of the N-type material can effectively reduce the series resistance of the reflector area, thereby significantly reducing the generation of Joule heat. The improvement of its thermodynamic properties not only alleviates the thermal lens effect of the quantum well in the active area, but also extends the life of the device under high temperature working conditions by suppressing thermally induced wavelength drift and mode instability, providing key reliability guarantees for high-density optoelectronic integration.

[0005] Another advantage of this application is that it provides a vertical cavity surface emitting laser. In this structure, since the free carrier absorption coefficient of N-type semiconductors in the near-infrared band is about one order of magnitude lower than that of P-type materials, the parasitic light absorption loss of the traditional P-DBR layer of about 15% to 20% can be compressed to less than 5%. The low-loss characteristic directly enhances the light field confinement capability within the resonant cavity, making the lateral optical mode closer to the fundamental mode Gaussian distribution, thereby sharpening the beam divergence angle from the 25°-35° of the traditional structure to the range of 15°-20°. At the same time, the reduced optical loss is converted into higher optical power output efficiency, and a 20% to 30% increase in optical power can be achieved at the same driving current. It has important engineering value in application scenarios such as long-distance detection laser radar (LiDAR) and high-precision biological imaging.

[0006] In order to achieve at least one of the above advantages or other advantages and purposes, according to one aspect of the present application, a vertical cavity surface emitting laser is provided, comprising at least one light emitting array, each of the light emitting arrays comprising at least one light emitting unit;

[0007] Each of the light-emitting units includes, from bottom to top, a first electrode, a first Bragg reflector, an active region, an electrical confinement layer, a second Bragg reflector, and a second electrode, wherein

[0008] A tunnel junction is provided between the first Bragg reflector and the second Bragg reflector, and the second Bragg reflector is an N-type doped DBR.

[0009] In the VCSEL laser according to the present application, the first Bragg reflector is an N-type doped DBR.

[0010] In the VCSEL laser according to the present application, the tunnel junction is located between the active region and the second Bragg reflector.

[0011] In the VCSEL laser according to the present application, the tunneling junction is located between the first Bragg reflector and the active region.

[0012] In the VCSEL laser according to the present application, the light-emitting unit further includes an electrical confinement layer, and the electrical confinement layer is located above the active region or below the active region.

[0013] In the VCSEL laser according to the present application, the active region is provided with at least one PN junction.

[0014] In the VCSEL laser according to the present application, the number of the electrical confinement layer is one or more.

[0015] In the VCSEL laser according to the present application, the electrical confinement layer is formed by oxidizing the active region or the second Bragg reflector, or the electrical confinement layer is formed by ion implantation onto the active region or the second Bragg reflector.

[0016] In the VCSEL laser according to the present application, the light-emitting hole is a circular light-emitting hole or a polygonal light-emitting hole.

[0017] In the VCSEL laser according to the present application, the light-emitting hole is a hexagonal light-emitting hole.

[0018] In the VCSEL laser according to the present application, the first electrode is an N-type metal electrode, and the second electrode is an N-type metal electrode.

[0019] Another aspect of the present application provides a process for preparing a VCSEL laser, comprising:

[0020] Forming an epitaxial layer structure by an epitaxial growth process, the epitaxial layer structure comprising: a substrate layer, a first Bragg reflector, an active region, a tunnel junction, and a second Bragg reflector, wherein the second Bragg reflector is an N-type doped DBR;

[0021] Etching the epitaxial structure to form etched trenches, and oxidizing the active area or the second Bragg reflector through the etched trenches to form an electrical confinement layer; or, implanting ions into the active area or the second Bragg reflector through an ion implantation process to form the electrical confinement layer;

[0022] depositing the metal layer on the second Bragg reflector to form a second electrode;

[0023] The substrate layer is ground and thinned, and then a metal layer is deposited on the bottom of the substrate layer to form a first electrode.

[0024] According to another aspect of the present application, the present application also discloses an electronic device, comprising

[0025] A laser projection device for projecting laser light, wherein the laser projection device comprises any of the VCSEL lasers described above;

[0026] a laser receiving device for receiving laser signals; and

[0027] A processor is communicatively connected to the laser projection device and the laser receiving device.

[0028] Further objectives and advantages of the present application will be fully reflected through understanding of the following description and drawings.

[0029] These and other objects, features and advantages of the present application are fully reflected in the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure shows a schematic structural diagram of a front-emitting VCSEL laser according to an embodiment of the present application.

[0031] Figure 2 The figure shows a schematic diagram of the epitaxial structure of a front-emitting VCSEL laser according to an embodiment of the present application.

[0032] Figure 3 The figure shows a schematic structural diagram of a back-emitting VCSEL laser according to an embodiment of the present application.

[0033] Figure 4 The figure shows a schematic diagram of the epitaxial structure of a back-emitting VCSEL laser according to an embodiment of the present application.

[0034] Figure 5 The figure shows a process diagram of a front-emitting VCSEL laser according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following description is intended to disclose the present application so that those skilled in the art can implement the present application. The embodiments described below are for illustrative purposes only, and those skilled in the art may conceive of other obvious variations. The basic principles of the present application defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present application.

[0036] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0037] Although ordinal numbers such as "first," "second," and the like will be used to describe various components, this does not limit which components are used. The terms are used solely to distinguish one component from another. For example, a first component could be referred to as a second component, and similarly, a second component could be referred to as a first component without departing from the teachings of the present invention. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0038] The terms used herein are for the purpose of describing various embodiments only and are not intended to be limiting. As used herein, the singular also includes the plural, unless the context clearly indicates otherwise. It will also be understood that the terms "include" and / or "have" when used in this specification specify the presence of stated features, numbers, steps, operations, components, elements, or combinations thereof, without excluding the presence of one or more other features, numbers, steps, operations, components, elements, or combinations thereof or the application overview.

[0039] The VCSEL laser proposed in the embodiment of the present application fundamentally solves the physical limitation problem of the traditional structure through a disruptive doping architecture and reconstruction of the carrier transport path. In the light-emitting unit, the first Bragg reflector (N-DBR) and the second Bragg reflector (N-DBR) respectively construct dual optimization channels for electron injection and photon reflection: when the first electrode injects current into the first Bragg reflector (N-DBR), electrons are injected from the first Bragg reflector (N-DBR) into the active area, while holes are quantum tunneled from the second Bragg reflector (N-DBR) through the tunnel junction. This design completely circumvents the hole migration bottleneck of the traditional P-DBR. At the same time, the electrical confinement layer (oxidation aperture or injection isolation region) and the dual N-DBR structure form a synergistic optimization effect - the precise size control of the oxidation aperture localizes the carriers in the center of the active area, and the strong confinement effect of the low-loss N-DBR on the light field prolongs the photon lifetime and significantly reduces the lasing threshold current. The carrier-photon cooperative management mechanism not only reduces device power consumption, losses, and threshold current, but also optimizes thermal resistance by suppressing hot carrier effects. Furthermore, the two-dimensional arrangement of multiple light-emitting units in the light-emitting array achieves coherent beam combining through phase-locking technology, increasing overall output power while maintaining a divergence angle of less than 20°.

[0040] The VCSEL laser according to the embodiment of the present application includes at least one light-emitting array, each of which includes at least one light-emitting unit; each of the light-emitting units includes, from bottom to top, a first electrode, a first Bragg reflector, an active region, an electrical confinement layer, a second Bragg reflector, and a second electrode, wherein a tunnel junction is provided between the first Bragg reflector and the second Bragg reflector, and the second Bragg reflector is an N-type doped DBR.

[0041] Exemplary VCSEL Chip

[0042] As the instruction manual Figure 1 and Figure 2As shown, the VCSEL laser provided in the embodiment of the present application adopts a dual N-type DBR stacked architecture. Its core light-emitting unit achieves efficient carrier transport and light field control through precise band engineering design of multi-layer heterojunction. Specifically, the VCSEL laser includes multiple light-emitting arrays 10, wherein each light-emitting array 10 includes at least one light-emitting unit 100. Each light-emitting unit 100 includes, from bottom to top, a first electrode 11, a substrate layer 12, a first Bragg reflector 13, an active region 14, a tunneling junction 15, an electrical confinement layer 16, a second Bragg reflector 17, and a second electrode 18.

[0043] The substrate layer 12 serves as the base of the light-emitting unit 100, and the first Bragg reflector 13 is stacked on the upper surface of the substrate layer 12. The substrate layer 12 is an N-type doped gallium arsenide substrate; or in other embodiments, the substrate layer 12 is a P-type doped gallium arsenide substrate. Of course, in the VCSEL laser, the substrate layer 12 includes but is not limited to a silicon substrate, a sapphire substrate, and a gallium arsenide substrate. Of course, in other embodiments, the material of the substrate layer 12 can be a doped material such as InP, GaN, or GaAs.

[0044] In this embodiment, the first Bragg reflector 13 is grown and stacked on the top surface of the substrate layer 12 by means of vapor phase epitaxy (MOCVD) technology. The first Bragg reflector 13 is an N-DBR; wherein the N-DBR is formed by alternating stacks of N-type doped AlxGa1-XAs with a high aluminum content and N-type doped AlxGa1-XAs with a low aluminum content. The materials of the N-type doped DBR include, but are not limited to, InGaAsP / InP, AlGaInAs / AlInAs, AlGaAsSb / AlAsSb, GaAs / AlGaAs, Si / MgO, and Si / Al2O3. It is worth mentioning that the material selection of the alternating layer depends on the operating wavelength of the laser emitted by the light-emitting hole, and the optical thickness of the alternating layer is equal to or approximately equal to 1 / 4 of the operating wavelength of the laser.

[0045] The second Bragg reflector 17 is located above the first Bragg reflector 13. The second Bragg reflector 17 is grown to the top surface of the active area by vapor phase epitaxy (MOCVD). The second Bragg reflector 17 is an N-DBR, wherein the N-DBR is formed by alternating stacks of N-type doped AlxGa1-XAs with a high aluminum content and N-type doped AlxGa1-XAs with a low aluminum content. The materials of the N-type doped DBR include but are not limited to: InGaAsP / InP, AlGaInAs / AlInAs, AlGaAsSb / AlAsSb, GaAs / AlGaAs, Si / MgO and Si / Al2O3. It is worth mentioning that the material selection of the alternating layer depends on the operating wavelength of the laser emitted by the light-emitting hole, and the optical thickness of the alternating layer is equal to or approximately equal to 1 / 4 of the operating wavelength of the laser.

[0046] The active region 14 is grown on the top surface of the first Bragg reflector 13 by means of metal-organic chemical vapor deposition (MOCVD) technology. The active region 14 is sandwiched between the first Bragg reflector 13 and the second Bragg reflector 17 to form a resonant cavity. After being excited, photons are reflected back and forth in the resonant cavity and repeatedly amplified to form laser oscillation, thereby forming a laser. The active region 14 includes a quantum well (of course, in other examples of the present application, the active region may include quantum dots), which may be made of AlInGaAs (e.g., AlInGaAs, GaAs, AlGaAs, and InGaAs), InGaAsP (e.g., InGaAsP, GaAs, InGaAs, GaAsP, and GaP), GaAsSb (e.g., GaAsSb, GaAs, and GaSb), InGaAsN (e.g., InGaAsN, GaAs, InGaAs, GaAsN, and GaN), or AlInGaAsP (e.g., AlInGaAsP, AlInGaAs, AlGaAs, InGaAs, InGaAsP, GaAs, InGaAs, GaAsP, and GaP). Of course, in the embodiment of the present application, the active region may also be made of other compositions for forming a quantum well layer.

[0047] The VCSEL laser according to the embodiment of the present application has at least one tunneling junction 19a; the tunneling junction 19a is located between the active region 14 and the second Bragg reflector 17. Figure 3 and Figure 4As shown, in a VCSEL laser where other lasers are emitted from the back, the tunneling junction 19b is located between the active region 14 and the first Bragg reflector 13. The tunneling junction operates based on the tunneling effect. The so-called tunneling effect means that when the carrier energy is low (less than the barrier height, i.e., E < V), due to the very small thickness of the thin film material itself (in the case of 10 nm or even thinner), the carriers still have a certain probability of passing through the thin film material. The active region of the VCSEL contains a PN junction. When current is injected, electrons and holes recombine radiatively in the active region, generating photons. If the structure includes a tunneling junction, an upper / lower N-type DBR structure can be achieved, further reducing the series resistance and absorption loss, and improving the efficiency and beam quality; in other embodiments, the number of PN junctions is multiple.

[0048] The electrical confinement layer 16 is formed below the second Bragg reflector 17 or above the active region 14. The electrical confinement layer 16 has a high resistivity to guide charges from the middle region of the VCSEL laser into the active region 14. As Figure 3 As shown, in a VCSEL laser where other lasers are emitted from the back, the electrical confinement layer 16b is located at the top of the first Bragg reflector 13 or at the bottom of the active region 14. The electrical confinement layer 16 is an annular structure, and the region surrounded by the electrical confinement layer 16 forms a light-emitting hole 161 for the laser in the active region 14 to emit. The shape of the light-emitting hole formed by the electrical confinement layer 16 is hexagonal; in other embodiments, the shape of the light-emitting hole is circular; in some other embodiments, the shape of the light-emitting hole is a polygon other than a hexagon.

[0049] In a specific embodiment, the electrical confinement layer 16 is an oxide layer formed by oxidation; the oxide layer has an oxidation opening for restricting the light-emitting aperture of the VCSEL laser. In particular, the oxide layer is formed in the bottom region of the second Bragg reflector through an oxidation process, that is, the oxide layer is formed by oxidizing a part of the material in the bottom region of the first reflector, where the degree of oxidation of the second Bragg reflector region determines the aperture of the light-emitting hole. Of course, in other embodiments, the oxide layer can also be formed at the top of the active region.

[0050] In another embodiment, the electrical confinement layer 16 is an ion implantation layer formed by ion implantation. The ions implanted into the epitaxial structure include, but are not limited to, hydrogen ions, oxygen ions, and the like. These ions may be implanted from the upper surface of the second Bragg reflector, and the depth of the implanted particles may be controlled based on the energy used during the implantation. Specifically, when deeper implantation is desired, the energy may be increased to place the implanted ions closer to the first Bragg reflector; when shallower implantation is desired, the energy may be decreased to place the implanted ions closer to the second Bragg reflector. The size of the light-emitting aperture formed by the electrical confinement layer may be controlled based on the energy and amount of the implanted ions.

[0051] Furthermore, in this embodiment, the substrate layer 12 has a top surface and a bottom surface. A first electrode 11 is provided on the bottom surface of the substrate layer 12. The first electrode 11 serves as the cathode of the light-emitting unit. The first electrode 11 is an N-type doped metal electrode layer (such as Ti / Pt / Au or Cr / Au) deposited on the bottom surface of the substrate layer 12. In this embodiment, a second electrode 18 is deposited on the second Bragg reflector 17. The second electrode 18 serves as the anode of the light-emitting unit. The second electrode 18 is an N-type doped metal electrode layer (such as Ti / Pt / Au or Cr / Au) deposited on the bottom surface of the substrate layer.

[0052] In summary, the VCSEL laser according to the embodiment of the present application is explained, which achieves a balance of performance in terms of photoelectric conversion efficiency, far-field beam divergence angle, high reliability, etc. of the VCSEL device by adopting an N-type doped second Bragg reflector.

[0053] According to another aspect of the present application, a method for preparing a VCSEL chip is also provided, which is used to prepare the VCSEL chip as described above. With reference to the drawings of the specification, the method for preparing a VCSEL chip according to an embodiment of the present application is explained. It is worth mentioning that in the embodiment of the present application, the traditional VCSEL chip preparation process is used in the preparation process of the VCSEL chip. The formation of an N-type doped second Bragg reflector in the preparation process of the traditional VCSEL chip can realize the preparation of the VCSEL chip in the embodiment of the present application. In this way, the original VCSEL chip production line and production equipment can be retained to use them for the preparation of the VCSEL chip of the present application, effectively reducing the production line transformation cost of the VCSEL chip, thereby reducing the preparation cost.

[0054] Exemplary VCSEL chip fabrication process

[0055] like Figure 5 As shown, in some embodiments of the present application, the preparation process of the VCSEL chip includes:

[0056] First, the first Bragg reflector, the active region of the multi-quantum well, the ultra-thin tunnel junction and the second Bragg reflector are epitaxially grown on the substrate in sequence to form a complete vertical resonant cavity structure, wherein the second Bragg reflector is an N-type doped DBR.

[0057] Subsequently, a ring groove is formed on the surface of the chip through photolithography and etching processes, and selective oxidation or ion implantation technology is used to precisely control the current limiting area at the bottom of the second Bragg reflector or above the active area to form an electrical limiting layer.

[0058] During the electrode preparation stage, a low-resistance second electrode is formed on the surface of the N-type doped second Bragg reflector through a metal deposition process, where the second electrode is an N-type doped ohmic contact electrode; then the substrate is thinned and polished, and the N-type doped first electrode is deposited to achieve optimized electrical connection and thermal management.

[0059] Exemplary vehicle-mounted laser equipment

[0060] According to another aspect of the present application, a laser device is also provided, which includes: a laser projection device for projecting laser light and a laser receiving device for receiving laser signals, wherein the laser projection device includes any vertical cavity surface emitting laser as described above. A processor communicatively connected to the laser projection device and the laser receiving device. The working principle of the laser device is: using laser as a medium, emitting laser light to the target to be measured, and receiving laser light reflected by the target to be measured, based on the time difference between the emitted laser and the received laser pulse (or the phase difference between the emitted laser and the received reflected laser), the relative position and distance between the target to be measured and the laser device are obtained, thereby realizing detection, tracking and identification of the object to be measured in the target area.

[0061] It should be noted that in the apparatus and method of the present application, the components or steps in different embodiments may be decomposed and / or reassembled without departing from the principles of the present application. Such decomposition and / or reassembly should be considered as included within the concept of the present application.

[0062] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

Claims

1. A VCSEL laser, characterized in that: comprising at least one light emitting array, each of the light emitting arrays comprising at least one light emitting unit; Each of the light-emitting units includes, from bottom to top, a first electrode, a first Bragg reflector, an active region, a second Bragg reflector, and a second electrode, wherein A tunnel junction is provided between the first Bragg reflector and the second Bragg reflector, and the second Bragg reflector is an N-type doped DBR.

2. The VCSEL laser according to claim 1, wherein: The first Bragg reflector is an N-type doped DBR.

3. The VCSEL laser according to claim 1, wherein: The tunneling junction is located between the active region and the second Bragg reflector.

4. The VCSEL laser according to claim 1, wherein: The tunneling junction is located between the first Bragg reflector and the active region.

5. The VCSEL laser according to claim 1, wherein: The light emitting unit further includes an electrical confinement layer, and the electrical confinement layer is located above the active region or below the active region.

6. The VCSEL laser according to claim 1, wherein: The active region is provided with at least one PN junction.

7. The VCSEL laser according to claim 1, wherein: The number of the electrical restriction layer is one or more.

8. The VCSEL laser according to claim 1, wherein: The electrical confinement layer is formed by oxidizing the active region or the second Bragg reflector, or the electrical confinement layer is formed by ion implantation onto the active region or the second Bragg reflector.

9. The VCSEL laser according to claim 1, wherein: The light-emitting hole is a circular light-emitting hole or a polygonal light-emitting hole.

10. The VCSEL laser according to claim 9, wherein: The light-emitting hole is a hexagonal light-emitting hole.

11. The VCSEL laser according to claim 1, wherein: The first electrode is an N-type metal electrode, and the second electrode is an N-type metal electrode.

12. A process for preparing a VCSEL laser according to claims 1-11, characterized in that: include: Forming an epitaxial layer structure by an epitaxial growth process, the epitaxial layer structure comprising: a substrate layer, a first Bragg reflector, an active region, a tunnel junction, and a second Bragg reflector, wherein the second Bragg reflector is an N-type doped DBR; Etching the epitaxial structure to form etched trenches, and oxidizing the active area or the second Bragg reflector through the etched trenches to form an electrical confinement layer; or, implanting ions into the active area or the second Bragg reflector through an ion implantation process to form the electrical confinement layer; depositing the metal layer on the second Bragg reflector to form a second electrode; The substrate layer is ground and thinned, and then a metal layer is deposited on the bottom of the substrate layer to form a first electrode.

13. An electronic device, characterized in that: include: A laser projection device for projecting laser light, wherein the laser projection device comprises any one of the VCSEL lasers according to claims 1 to 9; a laser receiving device for receiving laser signals; and A processor is communicatively connected to the laser projection device and the laser receiving device.

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