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

Abstract

The application discloses a vertical cavity surface emitting laser and a preparation method thereof, and the vertical cavity surface emitting laser comprises a substrate, an epitaxial basic structure located on one side of the substrate, and a cavity surface catastrophe threshold increasing layer located on a light emitting cavity surface of the epitaxial basic structure away from the substrate.

Description

TECHNICAL FIELD

[0001] The embodiment of the application relates to the technical field of lasers, in particular to a vertical cavity surface emitting laser and a preparation method thereof. BACKGROUND

[0002] A vertical cavity surface emitting laser (VCSEL) is developed on the basis of a gallium arsenide semiconductor material, is different from other light sources such as a light emitting diode (LED) and a laser diode (LD), has the advantages of small size, circular output light spot, single longitudinal mode output, small threshold current, low price, easy to be integrated into a large-area array and the like, and becomes an ideal light source of a next-generation laser radar.

[0003] At present, in order to realize higher power density output of the VCSEL, the industry gradually adopts a multi-junction structure design, that is, a plurality of active regions are connected in series through a tunnel junction to realize a fold increase of light output power. Up to now, the development of a VCSEL structure with eight or more junctions has been realized. Through the multi-junction structure design, the power density of the VCSEL has reached a similar technical level of an edge emitter device; however, this also makes the VCSEL face the same challenge as the edge emitter device, that is, under the action of high light power density, the temperature of the laser cavity surface rapidly rises and then induces bandgap contraction at the cavity surface, aggravates photon absorption, promotes the burning of the cavity surface, and causes catastrophic optical damage (COD). SUMMARY

[0004] The embodiment of the application provides a vertical cavity surface emitting laser and a preparation method thereof, so as to improve the catastrophic threshold of the vertical cavity surface emitting laser cavity surface and realize higher power density output of the device.

[0005] According to an aspect of the application, a vertical cavity surface emitting laser is provided, comprising:

[0006] a substrate;

[0007] an epitaxial basic structure located on one side of the substrate; the epitaxial basic structure comprises a plurality of active regions, and the plurality of active regions are arranged in a stacked manner along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction;

[0008] a cavity surface catastrophic threshold growth layer located on a light-emitting cavity surface of the epitaxial basic structure away from the substrate; the material of the cavity surface catastrophic threshold growth layer has a bandgap energy greater than the energy of laser light emitted by the light-emitting cavity surface, and the cavity surface catastrophic threshold growth layer is used to improve the catastrophic threshold of the cavity surface of the vertical cavity surface emitting laser.

[0009] Optionally, the lattice constant of the material of the cavity facet catastrophe threshold increasing layer is less than the lattice constant of the material of the substrate; the cavity facet catastrophe threshold increasing layer is further configured to generate tensile stress to compensate for partial compressive stress in the vertical cavity surface emitting laser.

[0010] Optionally, the wavelength range of the laser emitted by the light emitting cavity facet includes 808nm-1100nm.

[0011] The material of the cavity facet catastrophe threshold increasing layer includes GaAs 1-x P x ; wherein the component X of P is adjusted based on the wavelength of the laser.

[0012] Optionally, the component X of P is greater than 0 and less than or equal to 0.45.

[0013] Optionally, the thickness of the cavity facet catastrophe threshold increasing layer is less than or equal to 20nm.

[0014] Optionally, the epitaxial basic structure further includes:

[0015] a first Bragg reflection layer and a second Bragg reflection layer; a plurality of the active regions are located between the first Bragg reflection layer and the second Bragg reflection layer; wherein the first Bragg reflection layer is located between the active region adjacent to the substrate and the substrate;

[0016] a current diffusion layer; the current diffusion layer is located on the side of the second Bragg reflection layer away from the substrate;

[0017] The cavity facet catastrophe threshold increasing layer is located on the side of the current diffusion layer away from the substrate.

[0018] Optionally, the active region includes:

[0019] an active layer, and an upper spacer layer and a lower spacer layer located on opposite sides of the active layer; the lower spacer layer is closer to the substrate relative to the upper spacer layer;

[0020] wherein the type of the doped ions of the upper spacer layer and the type of the doped ions of the lower spacer layer are opposite.

[0021] Optionally, the epitaxial basic structure further includes a current limiting layer, which is located in the second Bragg reflection layer, or is located in the upper spacer layer adjacent to the second Bragg reflection layer.

[0022] Optionally, the epitaxial basic structure further includes a plurality of current limiting layers, which are one-to-one corresponding to the active regions; the plurality of current limiting layers are respectively located in the upper spacer layers of the corresponding active regions.

[0023] According to another aspect of the present application, there is provided a method for manufacturing a vertical cavity surface emitting laser, for forming the vertical cavity surface emitting laser according to any of the embodiments of the present application, comprising:

[0024] providing a substrate;

[0025] forming an epitaxial base structure on one side of the substrate; the epitaxial base structure comprises a plurality of active regions, and the plurality of active regions are arranged in a stacked manner along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction;

[0026] forming a cavity surface catastrophe threshold growth layer on a light-emitting cavity surface of the epitaxial base structure away from the substrate in a vacuum in-situ environment after epitaxial growth; wherein the band gap energy of the material of the cavity surface catastrophe threshold growth layer is greater than the energy of the laser emitted by the light-emitting cavity surface, and the cavity surface catastrophe threshold growth layer is used to increase the catastrophe threshold of the cavity surface of the vertical cavity surface emitting laser.

[0027] The technical scheme provided by the embodiment of the present application is based on the fact that the epitaxial growth direction of the VCSEL is consistent with the light-emitting direction of the device, and after the epitaxial base structure is grown, a large-band-gap COD-resistant structure, i.e., a cavity surface catastrophe threshold growth layer, higher than the device lasing wavelength, can be directly formed on the side of the epitaxial base structure away from the substrate in a vacuum in-situ environment. The band gap energy of the material of the cavity surface catastrophe threshold growth layer is greater than the energy of the laser emitted by the light-emitting cavity surface, so that the defect energy level formed on the surface of the cavity surface catastrophe threshold growth layer is significantly higher than the device lasing wavelength, forming transparent transmission of the output light and reducing the absorption of light, thereby increasing the cavity surface catastrophe threshold of the vertical cavity surface emitting laser and ensuring that the device has a higher power density output.

[0028] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 is a structure schematic diagram of a vertical cavity surface emitting laser provided by an embodiment of the present application;

[0031] Figure 2is a corresponding relation coordinate graph of lattice constants, band gap widths and wavelengths of different semiconductor materials provided by the embodiment of the present application;

[0032] Figure 3 is another structure schematic diagram of a vertical cavity surface emitting laser provided by the embodiment of the present application;

[0033] Figure 4 is a flow chart of a preparation method of a vertical cavity surface emitting laser provided by the embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the person of ordinary skill in the art without making creative efforts should belong to the protection scope of the present application.

[0035] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] As the background, in order to realize higher power density output of VCSEL, the industry gradually adopts multi-junction structure design, that is, through the tunnel junction to connect multiple active regions in series, to realize the light power multiplied, so far has realized the development of eight or more VCSEL structure. For the traditional multi-junction VCSEL device, after the growth of the epitaxial basic structure is completed, due to the interruption of physical material, there are unbound dangling bonds on the surface of the epitaxial basic structure, which will produce intrinsic defects, that is, surface states, which will oxidize with air or adsorb other impurities to further increase the surface state density. These state densities will introduce additional energy levels in the forbidden band, forming carrier trapping centers, which will absorb the higher light radiation inside the resonant cavity, causing the temperature at this point to exceed the melting point of III-V materials, and then the cavity surface will melt; and the temperature of the laser cavity surface rises rapidly and then induces the band gap shrinkage at the cavity surface, which promotes photon absorption and exacerbates the cavity surface burning, causing catastrophic optical mirror damage, which greatly affects the service life of the device.

[0037] In view of this, the embodiment of the present application provides a vertical cavity surface emitting laser, Figure 1 is a structural schematic diagram of a vertical cavity surface emitting laser provided by the embodiment of the present application, referring to Figure 1 , the vertical cavity surface emitting laser comprises:

[0038] a substrate 10;

[0039] an epitaxial basic structure 20 located on one side of the substrate 10; the epitaxial basic structure 20 comprises a plurality of active regions 24, and the plurality of active regions 24 are stacked along an epitaxial growth direction X; two adjacent active regions 24 are connected by a tunnel junction 23;

[0040] a cavity catastrophe threshold growth layer 30 located on the light-emitting cavity surface away from the substrate 10 of the epitaxial basic structure 20; the band gap energy of the material of the cavity catastrophe threshold growth layer 30 is greater than the energy of the laser emitted by the light-emitting cavity surface, and the cavity catastrophe threshold growth layer 30 is used to increase the catastrophe threshold of the cavity surface of the vertical cavity surface emitting laser.

[0041] Specifically, the substrate 10 is the basis for constructing the epitaxial basic structure 20, and the substrate 10 can be an N-type doped semiconductor substrate 10 or a P-type doped semiconductor substrate 10. In this embodiment, the substrate 10 is an N-type doped semiconductor substrate 10. The material of the substrate 10 can be any material suitable for forming a laser, such as gallium arsenide (GaAs). The epitaxial basic structure 20 is located on one side of the substrate 10, and the semi-epitaxial basic structure 20 comprises a plurality of active regions 24 stacked along an epitaxial growth direction, and two adjacent active regions 24 are connected by a tunnel junction 23. The multiple active regions 24 are connected in series through the tunnel junction 23, so as to realize the light power multiplied of the vertical cavity surface emitting laser. Among them, Figure 1Three active regions 24 are shown as an example.

[0042] Each active region 24 can include an active layer 243 and an upper space layer 242 and a lower space layer 241 located on opposite sides of the active layer 243; the lower space layer 241 is closer to the substrate 10 relative to the upper space layer 242. The type of doped ions of the upper space layer 242 and the type of doped ions of the lower space layer 241 are opposite. The type of doped ions of the lower space layer 241 is the same as the type of doped ions of the substrate 10. The active layer 243 is the core of the device, which can adopt a quantum well structure, for converting electrical energy into optical energy. The space layer is used to confine the optical field, which can confine both photons and electrons in the quantum well light-emitting region, to obtain high quantum efficiency.

[0043] The epitaxial growth direction X of the VCSEL-based is consistent with the light-emitting direction of the device. After the epitaxial basic structure 20 is grown, a large-bandgap COD-resistant structure, i.e., a cavity catastrophe threshold increasing layer 30, higher than the device lasing wavelength, can be formed on the side of the epitaxial basic structure away from the substrate 10 in a vacuum in-situ environment. The bandgap energy of the material of the cavity catastrophe threshold increasing layer 30 is greater than the energy of the laser emitted by the light-emitting cavity, so that the defect level formed on the surface of the cavity catastrophe threshold increasing layer 30 is significantly higher than the device lasing wavelength, reducing the absorption of light, forming a transparent transmission of the output light, thereby improving the cavity catastrophe threshold of the vertical cavity surface emitting laser, and ensuring that the device has a higher power density output. The structure adopts an in-situ epitaxial method and does not introduce other process flows, and can realize the preparation of the cavity catastrophe threshold increasing layer 30 of tens of thousands of chips in one-time processing of the entire wafer, thus having the advantages of simple structure, short process processing time, and low cost.

[0044] The vertical cavity surface emitting laser provided by the embodiment of the present application comprises: a substrate; an epitaxial basic structure located on one side of the substrate; the epitaxial basic structure comprises a plurality of active regions, and the plurality of active regions are arranged in layers along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction; a cavity catastrophe threshold increasing layer is located on a light-emitting cavity of the epitaxial basic structure away from the substrate; the bandgap energy of the material of the cavity catastrophe threshold increasing layer is greater than the energy of the laser emitted by the light-emitting cavity, and the cavity catastrophe threshold increasing layer is used to improve the catastrophe threshold of the cavity of the vertical cavity surface emitting laser. By introducing the wide-bandgap COD-resistant structure, a transparent window of the output light is formed, the absorption of light is reduced, the COD resistance level of the device is greatly improved, and a higher power density output of the device is realized. In addition, the structure adopts an in-situ epitaxial method and does not introduce other process flows, and can realize the preparation of the COD-resistant structure of tens of thousands of chips in one-time processing of the entire wafer, thus having the advantages of simple structure, short process processing time, and low cost.

[0045] In one embodiment of the present application, reference is made toFigure 1 The epitaxial basic structure 20 further comprises:

[0046] a first Bragg reflection layer 21 and a second Bragg reflection layer 22; a plurality of active regions 24 are located between the first Bragg reflection layer 21 and the second Bragg reflection layer 22; wherein the first Bragg reflection layer 21 is located between the active regions 24 adjacent to the substrate 10 and the substrate 10;

[0047] a current diffusion layer 26; the current diffusion layer 26 is located on a side of the second Bragg reflection layer 22 away from the substrate 10;

[0048] a cavity facet catastrophe threshold growth layer 30 is located on a side of the current diffusion layer 26 away from the substrate 10.

[0049] Specifically, the first Bragg reflection layer 21 and the second Bragg reflection layer 22 each comprise a series of alternating layers of different refractive index materials. By alternately growing materials with a certain refractive index difference, the reflectivity of light can reach more than 99%. The first Bragg reflection layer 21 and the second Bragg reflection layer 22 are used to reflect and enhance the light generated by the active layer 243 in the middle, and then the light is emitted from the surface of the second Bragg reflection layer 22 to form a laser. For example, the first Bragg reflection layer 21 and the second Bragg reflection layer 22 are each composed of two different refractive index material layers including an aluminum gallium arsenide material layer and a gallium arsenide material layer, or two different refractive index material layers including an aluminum gallium arsenide material layer with a high aluminum component and an aluminum gallium arsenide material layer with a low aluminum component. In some embodiments, the first Bragg reflection layer 21 and the second Bragg reflection layer 22 can also be formed by other materials.

[0050] If the first Bragg reflection layer 21 is an N-type Bragg reflector, the second Bragg reflection layer 22 is a P-type Bragg reflector. If the first Bragg reflection layer 21 is a P-type Bragg reflector, the second Bragg reflection layer 22 is an N-type Bragg reflector. The doping type of the first Bragg reflection layer 21 is the same as the doping type of the substrate 10. The elements doped in the P-type Bragg reflector include carbon, and the elements doped in the N-type Bragg reflector include at least one of tellurium, silicon, and germanium. The effective optical thickness of each alternating layer (the product of the thickness of the layer and the refractive index of the layer) is an odd integer multiple of one quarter of the operating wavelength of the vertical cavity surface emitting laser, i.e., the effective optical thickness of each alternating layer is one quarter of an odd integer multiple of the operating wavelength of the vertical cavity surface emitting laser.

[0051] The current diffusion layer 26 is located on the side of the second Bragg reflection layer 22 away from the substrate 10, and the diffusion direction of the current in the current diffusion layer 26 is parallel to the substrate 10. The injection current is uniformly dispersed at various positions of the device by high doping. The main function of the current diffusion layer 26 is to provide the ability of lateral conduction. The current diffusion layer 26 is exposed during the laser device manufacturing process and is connected with the electrode. The lateral conduction ability of the current diffusion layer 26 is crucial, which not only affects the performance index of the laser device, but also affects the light emission uniformity, heat generation, reliability, etc. of the laser array. If the conduction ability of the current diffusion layer 26 is poor, not only the light emission efficiency of the laser device will be reduced, but also the light emission uniformity of the laser array will be deteriorated. Therefore, it is necessary to ensure the conduction ability of the current diffusion layer 26. The conduction ability of the current diffusion layer 26 can be improved by increasing the thickness of the layer or increasing the doping concentration of the current diffusion layer 26.

[0052] The material of the current diffusion layer 26 includes GaAs, for example. After the growth of the current diffusion layer 26 is completed, there are dangling bonds on the surface of the current diffusion layer 26 due to the interruption of the physical material, which generates intrinsic defects, i.e. surface states. The surface states will be oxidized with air or adsorb other impurities to further increase the state density, which will introduce additional energy levels in the forbidden band, forming carrier trapping centers. After the carrier trapping centers absorb the higher light radiation in the resonant cavity, the temperature at the carrier trapping centers exceeds the melting point of the III-V group material, and then the cavity surface melts. In addition, the rapid increase of the temperature of the laser cavity surface induces the band gap shrinkage at the cavity surface, which promotes the photon absorption and aggravates the cavity surface burning, causing catastrophic optical mirror damage, which greatly affects the service life of the device. In the embodiment of the present application, the cavity surface catastrophic threshold growth layer 30 with a large band gap higher than the device lasing wavelength is grown on the surface of the current diffusion layer 26 away from the substrate 10. The defect energy level formed on the surface of the material of the cavity surface catastrophic threshold growth layer 30 is significantly higher than the device lasing wavelength, which forms transparent power transmission of the output light and reduces the absorption of the light, thereby greatly improving the COD resistance of the device.

[0053] In an embodiment of the present application, the lattice constant of the material of the cavity surface catastrophic threshold growth layer 30 is smaller than the lattice constant of the material of the substrate 10. The cavity surface catastrophic threshold growth layer 30 is also used to generate tensile stress to compensate for part of the compressive stress in the vertical cavity surface emitting laser.

[0054] It can be understood that the crystal structure in the device is mostly grown based on the substrate 10 material. Therefore, one problem to be faced is that the lattice constant of the crystal structure needs to be adapted to the lattice constant of the substrate 10 material, so as to avoid serious warping of the generated epitaxial wafer. The material of the active layer 243 in the epitaxial basic structure 20 usually includes InGaAs; and the lattice constant of InGaAs is greater than the lattice constant of the GaAs substrate 10. For a multi-junction VCSEL, after the epitaxial structure is grown, a compressive strain, or a compressive stress, is generated in the InGaAs epitaxial layer. The thicker the vertical cavity surface emitting laser, the more the compressive strain accumulated, which can cause serious warping of the epitaxial wafer, and the warping can cause process difficulties of the vertical cavity surface emitting laser and reduce the product yield. The material of the cavity catastrophe threshold growth layer 30 is selected to have a lattice constant less than that of the substrate 10 material; so that the cavity catastrophe threshold growth layer 30 can also be used to generate a tensile stress to compensate for part of the compressive stress in the vertical cavity surface emitting laser, thereby reducing the warping degree caused by excessive compressive stress.

[0055] In an embodiment of the present application, the wavelength range of the laser emitted by the light-emitting cavity includes: 808nm-1100nm;

[0056] The material of the cavity catastrophe threshold growth layer 30 includes GaAs 1-x P x ; wherein the component X of P is adjusted based on the wavelength of the laser.

[0057] It can be understood that, referring to Figure 2 , the abscissa is the lattice constant corresponding to the material, the ordinate on the left is the band gap width corresponding to the material, and the ordinate on the right is the wavelength corresponding to the material. For a VCSEL with a wavelength range of 808nm-1100nm, the material of the active layer 243 usually includes InGaAs. In order to satisfy that the band gap energy of the material of the cavity catastrophe threshold growth layer 30 is greater than the energy of the laser emitted by the light-emitting cavity, so that the defect level formed on the surface of the cavity catastrophe threshold growth layer 30 is significantly higher than the device lasing wavelength, forming transparent transmission of the output light and reducing light absorption, the material of the cavity catastrophe threshold growth layer 30 can be selected to be GaAsP or ALGaAs with a larger band gap width. However, since the lattice constant of ALGaAs is almost equal to that of GaAs, it is not enough to compensate for the compressive stress generated in the InGaAs epitaxial layer, and AL is easy to be oxidized. Therefore, the material of the cavity catastrophe threshold growth layer 30 in the embodiment of the present application is set to GaAs 1-x P x ; wherein the component X of P is adjusted based on the wavelength of the laser.

[0058] That is, a layer of ternary material GaAs 1-x Px The film layer of GaAs has two main functions, firstly... 1-x P x The direct bandgap range can be arbitrarily adjusted from 700nm to 867nm, significantly exceeding the lasing wavelength of current VCSELs (808-1100nm). For different wavelengths, VCSELs can be designed with matching material bandgap, effectively increasing the additional energy level bandgap generated by defects while ensuring low carrier transport losses. This reduces COD absorption due to proximity to the lasing wavelength, thus improving the device's COD threshold. Secondly, due to GaAs... 1-x P x A smaller lattice constant can mitigate the stress accumulation problem caused by the increased In composition thickness in multi-junction VCSLEs, improving device reliability and reducing warpage in large-size wafers. Specifically, the thickness of the cavity catastrophe threshold growth layer 30 is less than or equal to 20 nm.

[0059] In addition, from Figure 2 As can be seen from the broken line segment 1 between GaAs and GaP, if the composition X of P is large, GaAs... 1-x P x The impact of changes in the lattice constant of a material on the band gap width decreases; that is, the larger the component X of P, the greater the sacrifice in lattice constant compared to the gain in band gap. Therefore, setting the component X of P to be greater than 0 and less than or equal to 0.45 satisfies both the band gap width requirement and the material's lattice constant compatibility, avoiding an excessively small lattice constant.

[0060] In one embodiment of the present invention, reference is made to... Figure 1 The epitaxial basic structure 20 also includes a current confinement layer 25, which is located in the second Bragg reflector layer 22, or in the upper space layer 242 adjacent to the second Bragg reflector layer 22. Figure 1 An example is drawn where the current limiting layer 25 is located in the second Bragg reflector layer 22.

[0061] This can be understood as follows: the sidewalls of the epitaxial basic structure 20 are oxidized by wet oxidation of highly aluminum-doped aluminum under certain temperature conditions, forming a current-confining layer 25 in the second Bragg reflector layer 22. The current-confining layer 2530 has an opening 251, which defines the light-emitting region of the laser, from which the laser emits light. The oxidized aluminum oxide has high impedance, and the opening 251 of the current-confining layer 25 remains a highly aluminum-doped aluminum gallium arsenide material. The incoming current flows through the opening 251 to the active layer 243. The opening 251 of the current-confining layer 25 can be circular or rectangular. The current-confining layer also restricts the direction of current flow, reducing power loss.

[0062] In another embodiment of the present application, referring to Figure 3 , the epitaxial basic structure 20 can include a plurality of current limiting layers 25, which are arranged one-to-one with the active regions 24; the plurality of current limiting layers 25 are respectively located in the upper space layers 242 of the corresponding active regions 24, thereby further playing a role in limiting current and reducing power loss.

[0063] The embodiment of the present application also provides a preparation method of a vertical cavity surface emitting laser, which is used for forming the vertical cavity surface emitting laser in any of the above embodiments, Figure 4 is a flowchart of the preparation method of the vertical cavity surface emitting laser provided by the embodiment of the present application, referring to Figure 4 , the preparation method of the vertical cavity surface emitting laser includes:

[0064] S110, providing a substrate.

[0065] Specifically, the substrate is the basis for constructing the epitaxial basic structure, and the substrate can be an N-type doped semiconductor substrate or a P-type doped semiconductor substrate. In the embodiment, the substrate is an N-type doped semiconductor substrate. The material of the substrate can be any material suitable for forming a laser, for example, gallium arsenide.

[0066] S120, forming an epitaxial basic structure on one side of the substrate; the epitaxial basic structure includes a plurality of active regions, and the plurality of active regions are arranged in a stacked manner along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction.

[0067] Specifically, the semi-epitaxial basic structure includes a plurality of active regions arranged in a stacked manner along an epitaxial growth direction, and two adjacent active regions are connected by a tunnel junction. The plurality of active regions are connected in series through the tunnel junction to achieve a fold increase in the light output power of the vertical cavity surface emitting laser. The active region includes an active layer and upper and lower space layers located on opposite sides of the active layer; the lower space layer is closer to the substrate relative to the upper space layer; the type of doping ions of the upper space layer is opposite to the type of doping ions of the lower space layer. The active layer is the core of the device, and by injecting carriers into the active layer, the device can provide sufficient gain. The active layer adopts a quantum well structure, that is, different band gap materials are combined to form sufficient band steps to confine carriers. The active layer is used to convert electrical energy into optical energy. The space layer is used to limit the optical field, and can confine both photons and electrons in the quantum well light emitting region to obtain high quantum efficiency.

[0068] S130, after epitaxial growth, in a vacuum in-situ environment, a cavity surface catastrophe threshold growth layer is formed on the light-emitting cavity surface of the epitaxial basic structure away from the substrate side; wherein the band gap energy of the material of the cavity surface catastrophe threshold growth layer is greater than the energy of the laser emitted by the light-emitting cavity surface, and the cavity surface catastrophe threshold growth layer is used to improve the catastrophe threshold of the vertical cavity surface emitting laser cavity surface.

[0069] Specifically, based on the consistent epitaxial growth direction and device light-emitting direction of the VCSEL, after the epitaxial basic structure is grown, a large-bandgap COD-resistant structure, i.e. a cavity surface catastrophe threshold growth layer, higher than the device lasing wavelength can be directly formed on the side of the epitaxial basic structure away from the substrate in a vacuum in-situ environment. The band gap energy of the material of the cavity surface catastrophe threshold growth layer is greater than the energy of the laser emitted by the light-emitting cavity surface, so that the defect level formed on the surface of the cavity surface catastrophe threshold growth layer is significantly higher than the device lasing wavelength, forming transparent transmission of output light, reducing light absorption, thereby improving the cavity surface catastrophe threshold of the vertical cavity surface emitting laser, and ensuring that the device has higher power density output. The structure adopts in-situ epitaxy method and does not introduce other process flow, and can realize the preparation of the cavity surface catastrophe threshold growth layer of tens of thousands of chips processed at one time for the entire wafer, thus having the advantages of simple structure, short process processing time and low cost.

[0070] Note that the above is only the preferred embodiment of the present application and the technical principle applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A vertical cavity surface emitting laser, characterized by, The vertical cavity surface emitting laser comprises: a substrate; an epitaxial basic structure located on one side of the substrate; the epitaxial basic structure comprises a plurality of active regions, and the plurality of active regions are arranged in a stacked manner along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction; a cavity facet catastrophe threshold increasing layer located on a light-emitting cavity facet of the epitaxial basic structure away from the substrate; the material of the cavity facet catastrophe threshold increasing layer has a band gap energy greater than the energy of laser emitted by the light-emitting cavity facet, and the cavity facet catastrophe threshold increasing layer is used to increase the catastrophe threshold of the cavity facet of the vertical cavity surface emitting laser.

2. The vertical cavity surface emitting laser according to claim 1, wherein: the material of the cavity facet catastrophe threshold increasing layer has a lattice constant smaller than the lattice constant of the material of the substrate; and the cavity facet catastrophe threshold increasing layer is further used to generate tensile stress to compensate for partial compressive stress in the vertical cavity surface emitting laser.

3. The vertical cavity surface emitting laser according to claim 2, wherein: the wavelength range of the laser emitted by the light-emitting cavity facet comprises 808 nm-1100 nm; The material of the facet catastrophe threshold growth layer comprises GaAs 1-x P x ; wherein the component X of P is adjusted based on the wavelength of the laser.

4. The vertical cavity surface emitting laser of claim 3, wherein, the component X of P is greater than 0 and less than or equal to 0.

45.

5. The vertical cavity surface emitting laser of claim 2, wherein, The thickness of the cavity facet catastrophe threshold increasing layer is less than or equal to 20 nm.

6. The vertical cavity surface emitting laser of claim 1, wherein, The epitaxial basic structure further comprises: a first Bragg reflection layer and a second Bragg reflection layer; the plurality of active regions are located between the first Bragg reflection layer and the second Bragg reflection layer; wherein the first Bragg reflection layer is located between the active region adjacent to the substrate and the substrate; a current diffusion layer; the current diffusion layer is located on the side of the second Bragg reflection layer away from the substrate; the cavity facet catastrophe threshold increasing layer is located on the side of the current diffusion layer away from the substrate.

7. The vertical cavity surface emitting laser of claim 6, wherein, The active region comprises: an active layer and upper and lower spacer layers located on opposite sides of the active layer; the lower spacer layer is closer to the substrate than the upper spacer layer; wherein the type of doped ions of the upper spacer layer is opposite to the type of doped ions of the lower spacer layer.

8. The vertical cavity surface emitting laser according to claim 7, characterized in that The epitaxial basic structure further comprises a current limiting layer; the current limiting layer is located in the second Bragg reflection layer or in the upper spacer layer adjacent to the second Bragg reflection layer.

9. The vertical cavity surface emitting laser of claim 7, wherein, The epitaxial basic structure further comprises a plurality of current limiting layers; the current limiting layers correspond to the active regions one by one; and the plurality of current limiting layers are respectively located in the upper spacer layers of the corresponding active regions.

10. A method of fabricating a vertical cavity surface emitting laser, characterized by, A method for forming the vertical cavity surface emitting laser according to any one of claims 1-9 comprises: providing a substrate; forming an epitaxial basic structure on one side of the substrate; the epitaxial basic structure comprises a plurality of active regions, and the plurality of active regions are arranged in a stacked manner along an epitaxial growth direction; two adjacent active regions are connected by a tunnel junction; after epitaxial growth, forming a cavity facet catastrophe threshold increasing layer on a light-emitting cavity facet of the epitaxial basic structure away from the substrate in a vacuum in-situ environment; wherein the material of the cavity facet catastrophe threshold increasing layer has a band gap energy greater than the energy of laser emitted by the light-emitting cavity facet, and the cavity facet catastrophe threshold increasing layer is used to increase the catastrophe threshold of the cavity facet of the vertical cavity surface emitting laser.

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