Vertical cavity surface emitting laser and preparation method thereof

Abstract

The embodiment of the invention relates to a vertical cavity surface emitting laser and a preparation method thereof. The vertical cavity surface emitting laser comprises a substrate, a first conductive type reflecting layer, an active layer and a second conductive type reflecting layer which are stacked in sequence, the active layer comprises at least three quantum well layers, an oxide layer and a tunnel junction layer; the tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer; the first conduction type doping layers are made of materials including III-V family polybasic compounds, and in the multiple first conduction type doping layers, the components of III family elements of at least two first conduction type doping layers are different; and / or, the material of the second conductive type doped layers comprises a group III-V multi-component compound, and in the plurality of second conductive type doped layers, the group III elements of at least two second conductive type doped layers have different components; and in the plurality of oxide layers, the oxidation depths of at least two oxide layers are different. Therefore, the divergence angle of the device is effectively regulated and controlled.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a vertical cavity surface emitting laser and a preparation method thereof. Background Art

[0002] Vertical Cavity Surface Emitting Laser (VCSEL) has the advantages of low power consumption, surface emission and high modulation bandwidth, and has become an extremely attractive low-cost light source. As the requirements for VCSEL power and divergence angle in the field continue to increase, the epitaxial design of the device has shifted from single junction to multi-junction. The active layer of the multi-junction VCSEL is composed of multiple connected quantum well layers, each of which can generate photons, and the photons can be further amplified by adjacent quantum well layers to increase the output power of the laser. There are a large number of oxide layers in the multi-junction VCSEL, and the oxide layer can control the current and light field distribution. By adjusting the oxidation depth of multiple oxide layers, a divergence angle that meets the requirements can be obtained.

[0003] In the preparation process, the oxide layer is usually formed by oxidizing the confinement layer made of AlGaAs using a wet oxygen process. At present, the purpose of controlling the divergence angle is often achieved by changing the thickness of each confinement layer or changing the Al component in each confinement layer to obtain oxide layers with different oxidation depths. However, changing the thickness of the confinement layer will inevitably change the light field distribution in the active layer and affect the output mode of the laser. In addition, if the Al component in the confinement layer is too high, the oxide layer formed after oxidation will be easily split, affecting the reliability of the device.

[0004] Therefore, how to adjust the divergence angle of the device without affecting the light field distribution and device reliability has become an urgent problem to be solved in this field. Summary of the invention

[0005] In view of this, embodiments of the present application provide a vertical cavity surface emitting laser and a method for manufacturing the same in order to solve at least one problem existing in the background technology.

[0006] In a first aspect, an embodiment of the present application provides a vertical cavity surface emitting laser, comprising a substrate, a first conductive type reflective layer, an active layer, and a second conductive type reflective layer stacked in sequence; wherein:

[0007] The active layer includes at least three quantum well layers stacked along the thickness direction of the substrate, and an oxide layer and a tunnel junction layer located between two adjacent quantum well layers, and the oxide layer and the tunnel junction layer between two adjacent quantum well layers are stacked in sequence along a direction away from the substrate;

[0008] The tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer sequentially stacked in a direction away from the substrate;

[0009] The material of the first conductive type doping layer includes a III-V group compound, and among the plurality of the first conductive type doping layers, at least two of the first conductive type doping layers have different compositions of the III group elements; and / or, the material of the second conductive type doping layer includes a III-V group compound, and among the plurality of the second conductive type doping layers, at least two of the second conductive type doping layers have different compositions of the III group elements;

[0010] Among the multiple oxide layers, at least two oxide layers have different oxidation depths.

[0011] In combination with the first aspect of the present application, in an optional implementation manner, the material of the first conductive type doped layer includes In x Ga 1-x P, wherein 0<x<1; among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different x.

[0012] In combination with the first aspect of the present application, in an optional implementation manner, the material of the second conductive type doped layer includes Al y Ga 1-y As, wherein 0<y<1; among the plurality of the second conductivity type doped layers, at least two of the second conductivity type doped layers have different y.

[0013] In combination with the first aspect of the present application, in an optional implementation, among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different doping concentrations of first conductivity type doped ions.

[0014] In combination with the first aspect of the present application, in an optional embodiment, the active layer also includes a plurality of spacer layers, each of which is respectively arranged between the oxide layer and the tunnel junction layer between two adjacent quantum well layers; among the plurality of spacer layers, at least two of the spacer layers have different thicknesses.

[0015] In a second aspect, an embodiment of the present application provides a method for preparing a vertical cavity surface emitting laser, the method comprising:

[0016] providing a substrate;

[0017] epitaxially growing a first conductive type reflective layer on the substrate;

[0018] An active layer is epitaxially grown on the first conductive type reflective layer; wherein the active layer comprises at least three quantum well layers stacked along the epitaxial growth direction and a confinement layer and a tunnel junction layer located between two adjacent quantum well layers, the confinement layer and the tunnel junction layer between two adjacent quantum well layers are sequentially stacked along the epitaxial growth direction; the tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer sequentially stacked in a direction away from the substrate;

[0019] The material of the first conductive type doping layer includes a III-V group compound, and among the plurality of the first conductive type doping layers, at least two of the first conductive type doping layers have different compositions of the III group elements; and / or, the material of the second conductive type doping layer includes a III-V group compound, and among the plurality of the second conductive type doping layers, at least two of the second conductive type doping layers have different compositions of the III group elements;

[0020] epitaxially growing a second conductive type reflective layer on the active layer;

[0021] The plurality of restriction layers are oxidized synchronously to form a plurality of oxide layers accordingly; wherein at least two of the plurality of oxide layers have different oxidation depths.

[0022] In conjunction with the second aspect of the present application, in an optional implementation manner, the material of the first conductive type doped layer includes In x Ga 1-x P, wherein 0<x<1; among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different x.

[0023] In conjunction with the second aspect of the present application, in an optional implementation manner, the material of the second conductive type doped layer includes Al y Ga 1-y As, wherein 0<y<1; among the plurality of the second conductivity type doped layers, at least two of the second conductivity type doped layers have different y.

[0024] In combination with the second aspect of the present application, in an optional implementation, among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different doping concentrations of first conductivity type doped ions.

[0025] In combination with the second aspect of the present application, in an optional implementation, the active layer further includes a plurality of spacer layers, each of which is respectively arranged between the spacer layer and the tunnel junction layer between two adjacent quantum well layers.

[0026] The vertical cavity surface emitting laser and the preparation method thereof provided in the embodiments of the present application control the energy band structure of the first conductive type doped layer by controlling the Group III element composition of the first conductive type doped layer in the tunneling junction layer, and / or control the energy band structure of the second conductive type doped layer by controlling the Group III element composition of the second conductive type doped layer in the tunneling junction, and then control the potential barrier of the tunneling junction layer, thereby affecting the degree of diffusion of free electrons in the first conductive type doped layer to the oxide layer, and utilizing the inhibitory effect of free electrons on oxidation to achieve control of the oxidation depth of the oxide layer, thereby effectively regulating the divergence angle of the device without affecting the light field distribution and device reliability.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0029] Figure 1 A schematic cross-sectional structure diagram of a vertical cavity surface emitting laser provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the structure of an oxide layer and a tunnel junction layer located between two adjacent quantum well layers;

[0031] Figure 3 Schematic diagram of the energy band change of the N-type doped layer in the tunneling junction layer;

[0032] Figure 4 Schematic diagram of the energy band change of the P-type doped layer in the tunneling junction layer;

[0033] Figure 5 A schematic diagram of a process for preparing a vertical cavity surface emitting laser provided in an embodiment of the present application;

[0034] Figures 6 to 10 A schematic diagram of the cross-sectional structure of a vertical cavity surface emitting laser during the preparation process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The exemplary embodiments disclosed in the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope disclosed in the present application to those skilled in the art.

[0036] In the following description, a large number of specific details are given to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features known in the art are not described; that is, all features of the actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0037] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0038] When an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. Although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below may be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0039] Spatially relative terms such as "under", "below", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. In addition to the orientation shown in the figure, the spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0040] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0041] In order to thoroughly understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below, but in addition to these detailed descriptions, the present application may also have other implementation methods.

[0042] Figure 1 This is a schematic diagram of the cross-sectional structure of a vertical cavity surface emitting laser provided in an embodiment of the present application. Figure 1 and Figure 2 As shown, the vertical cavity surface emitting laser comprises: a substrate 100, a first conductive type reflective layer 200, an active layer 300 and a second conductive type reflective layer 400 stacked in sequence; wherein,

[0043] The active layer 300 includes at least three quantum well layers 310 stacked along the thickness direction of the substrate 100 and an oxide layer 350 and a tunnel junction layer 330 located between two adjacent quantum well layers 310. The oxide layer 350 and the tunnel junction layer 330 between two adjacent quantum well layers 310 are stacked in sequence in a direction away from the substrate 100.

[0044] The tunnel junction layer 330 includes a second conductive type doped layer 3302 and a first conductive type doped layer 3301 sequentially stacked in a direction away from the substrate 100;

[0045] The material of the first conductive type doping layer 3301 includes a group III-V multi-component compound, and among the plurality of first conductive type doping layers 3301, at least two of the first conductive type doping layers 3301 have different compositions of group III elements; and / or, the material of the second conductive type doping layer 3302 includes a group III-V multi-component compound, and among the plurality of second conductive type doping layers 3302, at least two of the second conductive type doping layers 3302 have different compositions of group III elements;

[0046] Among the multiple oxide layers 350 , at least two oxide layers 350 have different oxidation depths.

[0047] It can be understood that by controlling the III group element composition of the first conductive type doped layer 3301 in the tunnel junction layer 330 to control the energy band structure of the first conductive type doped layer 3301, and by controlling the III group element composition of the second conductive type doped layer 3302 in the tunnel junction to control the energy band structure of the second conductive type doped layer 3302, the potential barrier of the tunnel junction layer 330 is affected, thereby affecting the degree of diffusion of free electrons in the first conductive type doped layer 3301 to the oxide layer 350, and utilizing the inhibitory effect of free electrons on oxidation to achieve control of the oxidation depth of the oxide layer 350, thereby effectively regulating the divergence angle of the device without affecting the light field distribution and device reliability.

[0048] In this embodiment, the first conductivity type is specifically, for example, N type, and the second conductivity type is specifically, for example, P type.

[0049] The oxide layer 350 is formed by oxidation of the restriction layer. The material of the restriction layer is generally a III-V group multi-compound with a high Al component, such as Al z Ga 1-z As (0.9<z≤1). In the actual preparation process, a wet oxidation process is usually used to make part of AlGaAs react with the oxidant H2O vapor to form Al2O3. The entire oxidation process includes two processes: the process of H2O vapor molecules reacting with Al and the process of H2O vapor molecules diffusing inward.

[0050] Specifically, in the initial stage of oxidation, H2O vapor reacts with the portion of the AlGaAs confinement layer exposed outside the active layer 300, and the reaction equation is:

[0051] 2AlAs+4H2O=2AlO(OH)+2AsH3 (1)

[0052] As the oxidation reaction proceeds, AlGaAs is further oxidized, and the reaction equation is:

[0053] 2AlAs+6H2O=Al2O3+As2O3+6H2 (2)

[0054] Thus, the oxide Al2O3 is formed. As the oxidation reaction continues, the H2O vapor molecules will gradually diffuse inward, gradually oxidizing the limiting layer from the periphery to the center. Under a certain reaction time, oxidation temperature and H2O vapor flow control, the finally prepared oxide layer 350 includes an unoxidized portion located at the center, i.e., an oxidation hole, through which electrons can pass, and the oxide layer 350 also includes an oxidized portion located at the periphery, through which electrons are blocked. Thus, by regulating the oxidation depth of multiple oxide layers 350, oxide layers 350 with different oxidation hole diameters can be obtained, and the oxidation holes can be used to limit the laser transverse mode and provide vertical optical confinement to achieve the purpose of adjusting the divergence angle.

[0055] It is not difficult to understand that Al z Ga 1-z The higher the Al component in As, the faster the oxidation rate, and the deeper the oxidation depth of the oxide layer 350 is when the reaction time is constant; the thicker the confinement layer, the larger its contact surface with H2O vapor, the faster the oxidation rate, and the deeper the oxidation depth of the oxide layer 350 is when the reaction time is constant; conversely, the lower the Al component or the thinner the confinement layer, the slower the oxidation rate and the shallower the oxidation depth. Since multiple confinement layers in the active layer 300 are oxidized synchronously in the actual preparation of the device, the oxidation rate can be controlled by adjusting the Al component and thickness of multiple confinement layers to obtain different oxidation depths within a certain period of time. However, if the Al component is too high, the oxide layer 350 formed after oxidation will be easily split, affecting the reliability of the device; changes in the thickness of the confinement layer 320 will change the light field distribution in the active layer 300 and affect the output mode of the laser.

[0056] Please refer to Figure 1 In VCSEL, the tunneling junction layer 330 connects adjacent quantum well layers 310 to provide carrier injection between different quantum well layers 310. The tunneling junction is usually composed of stacked P-type doped layers and N-type doped layers. In this embodiment, the P-type doped layer is the second conductive type doped layer 3302, and the N-type doped layer is the first conductive type doped layer 3301. Please refer to Figure 2, between two adjacent quantum well layers 310, an oxide layer 350, a second conductive type doped layer 3302 (P-type doped layer) and a first conductive type doped layer 3301 (N-type doped layer) are sequentially stacked in a direction away from the substrate 100, wherein the free electrons in the N-type doped layer diffuse into the confinement layer through the P-type doped layer, and the injection of free electrons changes the charge distribution and energy band structure of the confinement layer, affecting the chemical reaction kinetics between the confinement layer and the oxidant to change the oxidation rate, and the free electrons in the confinement layer may form a charge shield on the surface of the confinement layer, hindering the contact between the oxidant and the confinement layer, thereby hindering the oxidation process. Therefore, this embodiment uses the effect that the free electron concentration affects the redox reaction, controls the free electron concentration in multiple confinement layers, and obtains oxide layers with different oxidation depths without affecting the device reliability and the laser mode.

[0057] Group III-V multi-component compound semiconductors are compound semiconductor materials composed of two or more group III elements and one or more group V elements. In group III-V multi-component compounds, changes in the composition of group III elements will lead to changes in the properties of the material, such as electron mobility, bandgap width, and photoelectric conversion efficiency. Specifically, if the composition of a certain group III element increases, this group III atom will replace other group III atoms to combine with group V atoms, and different group III atoms have different electronegativity, so that the polarity of the covalent bond formed by group III elements and group V elements is different, and the binding effect on valence electrons is different. The degree to which the valence electrons are bound is reflected by the energy difference between the lowest energy level of the conduction band and the lowest energy level of the valence band, which can be specifically reflected by the distance between the conduction band and the valence band. As a result, the position of the conduction band and the valence band of the N-type doped layer and / or the P-type doped layer in the tunneling junction layer changes, which will affect the potential barrier between the N-type doped layer and the P-type doped layer. The free electrons in the N-type doped layer may need more or less energy to cross the potential barrier to the P-type doped layer, which in turn affects the free electrons entering the confinement layer.

[0058] The material of the first conductive type doping layer 3301 is a group III-V multi-component compound, wherein the group III elements include at least two of Al, Ga, and In, and the group V elements include at least one of N, P, As, and Sb.

[0059] Optionally, the material of the first conductive type doping layer 3301 includes In x Ga 1-x P; wherein x is the In component, 0<x<1; among the multiple first conductivity type doped layers 3301, at least two first conductivity type doped layers 3301 have different x. It can be understood that since the electronegativity of In atoms is less than that of Ga atoms, the polarity of the formed In-P bond is lower than that of the Ga-P bond, and the binding of valence electrons is also lower. Therefore, please refer to Figure 3 , with In x Ga1-x The x in P gradually increases, that is, the In component gradually increases, and the In atoms gradually replace the Ga atoms and combine with the P atoms, and the binding of the valence electrons gradually decreases, so that the valence band gradually moves downward, that is, moves in the direction of lower energy. In this process, the conduction band will move downward with the valence band. In the tunnel junction, a space charge region, that is, a barrier region, is formed between the P-type doped layer and the N-type doped layer. The free electrons in the N-type doped layer need to cross the barrier to diffuse to the P-type doped layer. As the conduction band and valence band of the N-type doped layer move downward, the barrier height moves from h1 to h2, that is, the barrier gradually increases, hindering the free electrons in the N-type doped layer from diffusing to the P-type doped layer, and then hindering the free electrons from entering the restriction layer, reducing the influence of the free electrons on the oxidation process, and increasing the oxidation rate. Therefore, by making the multiple first conductive type doped layers 3301 have different In components, the oxidation rate can be controlled to obtain an oxide layer 350 with different oxidation depths.

[0060] In this embodiment, the material of the first conductive type doped layer 3301 is InGaP. It is understandable that in practical applications, any suitable III-V group multi-component compound can be selected to adjust the energy band structure of the first conductive type doped layer 3301 by adjusting the composition of the III group element.

[0061] In some other embodiments, the material of the first conductive type doping layer 3301 may include Al m Ga 1-m AsSb; wherein m is the Al component, 0<m<1; among the multiple first conductivity type doped layers 3301, at least two first conductivity type doped layers 3301 have different m. It can be understood that since the electronegativity of Al atoms is greater than that of Ga atoms, the polarity of the formed Al-As bond and Al-Sb bond is higher than that of the Ga-As bond and Ga-Sb bond, and the binding of valence electrons is stronger. Therefore, please refer to Figure 3 , with Al m Ga 1-m In AsSb, m gradually increases, that is, the Al component gradually increases, and Al atoms gradually replace Ga atoms to combine with As atoms and Sb atoms, and the binding of valence electrons gradually increases, thereby gradually moving the valence band upward, that is, moving toward a higher energy direction. In this process, the conduction band will move upward with the valence band. In this process, the barrier height moves from h2 to h1, that is, the barrier gradually decreases, and the free electrons in the N-type doped layer can diffuse to the P-type doped layer with less energy, thereby accelerating the diffusion of free electrons, increasing the free electron concentration in the confinement layer, enhancing the influence of free electrons on the oxidation process, and reducing the oxidation rate. Therefore, by making multiple N-type doped layers have different Al components, the oxidation rate can be controlled to obtain an oxide layer 350 with different oxidation depths.

[0062] It can be understood that when the material of the first conductive type doping layer 3301 is a III-V group polynary compound, the material of the second conductive type doping layer 3302 can be any suitable semiconductor material, and the material of the second conductive type doping layer 3302 is lattice matched with the material of the first conductive type doping layer 3301. In this embodiment, the material of the first conductive type doping layer 3301 can be InGaP, and the material of the second conductive type doping layer 3302 can be GaAs.

[0063] The material of the second conductive type doping layer 3302 is a group III-V multi-component compound, wherein the group III elements include at least two of Al, Ga, and In, and the group V elements include at least one of N, P, As, and Sb.

[0064] Optionally, the material of the second conductive type doping layer 3302 includes Al y Ga 1-y As; wherein y is the Al component, 0<y<1; among the plurality of second conductive type doped layers 3302, at least two second conductive type doped layers 3302 have different y. It can be understood that since the electronegativity of Al atoms is greater than that of Ga atoms, the polarity of the formed Al-As bond is higher than that of the Ga-As bond, and the binding of valence electrons is stronger. Therefore, please refer to Figure 4 , with Al y Ga 1-y The y in As gradually increases, that is, the Al component gradually increases, and Al atoms gradually replace Ga atoms and combine with As atoms, and the binding of valence electrons gradually increases, so that the valence band gradually moves upward, that is, moves in the direction of higher energy. In this process, the conduction band will move upward with the valence band. In this process, the barrier height moves from h3 to h4, that is, the barrier gradually increases, and the free electrons in the N-type doped layer need to obtain more energy to diffuse to the P-type doped layer, thereby hindering the diffusion of free electrons, reducing the concentration of free electrons in the restriction layer, reducing the influence of free electrons on the oxidation process, and increasing the oxidation rate. Therefore, by making multiple second conductive type doped layers 3302 have different Al components, the oxidation rate can be controlled to obtain an oxide layer 350 with different oxidation depths.

[0065] In this embodiment, the material of the second conductive type doped layer 3302 is AlGaAs. It is understandable that in practical applications, any suitable III-V group multi-component compound can be selected to adjust the energy band structure of the second conductive type doped layer 3302 by adjusting the composition of the III group element.

[0066] In some other embodiments, the material of the second conductive type doping layer 3302 may include In n Ga 1-nAs; wherein n is the In component, 0<n<1; among the plurality of second conductivity type doped layers 3302, at least two second conductivity type doped layers 3302 have different n. It can be understood that since the electronegativity of In atoms is less than that of Ga atoms, the polarity of the formed In-As bond is lower than that of the Ga-As bond, and the binding of valence electrons is also lower. Therefore, please refer to Figure 4 , with In n Ga 1-n The n in As gradually increases, that is, the In component gradually increases, and the In atoms gradually replace the Ga atoms to combine with the As atoms, and the binding of the valence electrons gradually decreases, so that the valence band gradually moves downward, that is, moves to a lower energy direction. In this process, the conduction band will move downward with the valence band. In this process, the barrier height moves from h4 to h3, that is, the barrier gradually decreases, which promotes the diffusion of free electrons in the N-type doped layer to the P-type doped layer, and then facilitates the free electrons to enter the restriction layer, enhancing the influence of free electrons on the oxidation process and reducing the oxidation rate. Thus, by making the multiple second conductive type doped layers 3302 have different In components, the oxidation rate can be controlled to obtain an oxide layer 350 with different oxidation depths.

[0067] It can be understood that when the material of the second conductive type doping layer 3302 is a III-V group polyvalent compound, the material of the first conductive type doping layer 3301 can be any suitable semiconductor material, and the material of the first conductive type doping layer 3301 is lattice matched with the material of the second conductive type doping layer 3302. In this embodiment, the material of the second conductive type doping layer 3302 can be AlGaAs, and the material of the first conductive type doping layer 3301 can be GaAs.

[0068] In this embodiment, the second conductive type doping ions are specifically, for example, P-type doping ions, which may include C; the first conductive type doping ions are specifically, for example, N-type doping ions, which may include Te and / or Se.

[0069] A tunnel junction is set between adjacent quantum well layers 310 of the VCSEL as a connection, and carrier redistribution can be achieved through quantum tunneling to improve the luminous efficiency of the device. In order to better produce the tunneling effect, the N-type doped layer and the P-type doped layer in the tunnel junction are usually heavily doped, that is, the N-type doped layer can also be called "N-type heavily doped layer" or "N++ layer", and the P-type doped layer can also be called "P-type heavily doped layer" or "P++ layer".

[0070] The doping concentration of N-type doping ions in the N-type doping layer may range from 4E18 to 5E19; and the doping concentration of P-type doping ions in the P-type doping layer may range from 1E19 to 1E20.

[0071] Optionally, among the multiple first conductive type doped layers 3301, at least two first conductive type doped layers 3301 have different doping concentrations of first conductive type doped ions. If there are more N-type doped ions in the N-type doped layer, there are more free electrons therein, and then more free electrons diffused into the confinement layer, which has a greater impact on the oxidation rate, and vice versa. Thus, by controlling the concentration of the first conductive type doped ions in the multiple first conductive type doped layers 3301, the corresponding confinement layers can have different concentrations of free electrons, and the oxidation depth can be further controlled.

[0072] Optionally, refer to Figure 1 The active layer 300 further includes a plurality of spacer layers 340, each of which is disposed between the oxide layer 350 and the tunneling junction layer 330 between two adjacent quantum well layers 310; at least two of the plurality of spacer layers 340 have different thicknesses. After the free electrons jump out of the tunneling junction layer 330, they still need to cross the spacer layer 340 to reach the confinement layer. In this process, the free electrons have a limited diffusion distance due to the limitation of their lifespan. By controlling the thickness of the plurality of spacer layers 340, the corresponding confinement layer can have different concentrations of free electrons, and the oxidation depth can be further controlled.

[0073] The thickness L of the spacer layer 340 satisfies nL=m*λ / 2, where n is the refractive index, m is an integer, and λ is the wavelength. It can be understood that the thickness of the spacer layer 340 is an integer multiple of half the wavelength, thereby ensuring effective reflection and resonant amplification of light and ensuring normal operation of the device.

[0074] However, if the thickness of the spacer layer 340 is too large, the free electrons jumping out of the tunneling junction layer 330 are blocked by the spacer layer 340, that is, the oxidation rate of the confinement layer 320 will not be affected by the free electrons, and multiple oxide layers 350 with different oxidation depths cannot be obtained, and then the divergence angle of the device cannot be adjusted. Therefore, the thickness of the spacer layer 340 can be less than or equal to 200nm.

[0075] In the present embodiment, the first conductive type reflective layer 200 is formed by stacking a plurality of first material layers 210 ; and the second conductive type reflective layer 400 is formed by stacking a plurality of second material layers 410 .

[0076] Please refer to Figure 1 The device further includes a contact layer 500 located on the second conductive type reflective layer 400 .

[0077] In this embodiment, the material of the contact layer 500 may include GaAs.

[0078] It is understandable that in order to reduce the contact resistance between the contact layer 500 and the metal electrode, the contact layer 500 may be a highly doped p-type material layer, that is, the contact layer 500 may be called a “P+ layer.” The concentration of the P-type doping ions in the contact layer 500 is greater than 4E19.

[0079] The present application also provides a method for preparing a vertical cavity surface emitting laser. Figure 5 As shown, the method for preparing a vertical cavity surface emitting laser includes:

[0080] S1: providing a substrate;

[0081] S2: epitaxially growing a first conductive type reflective layer on the substrate;

[0082] S3: epitaxially growing an active layer on the first conductive type reflective layer; wherein the active layer comprises at least three quantum well layers stacked along the epitaxial growth direction and a confinement layer and a tunnel junction layer located between two adjacent quantum well layers, and the confinement layer and the tunnel junction layer between two adjacent quantum well layers are sequentially stacked along the epitaxial growth direction; the tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer sequentially stacked along a direction away from the substrate; the material of the first conductive type doped layer comprises a III-V group multi-component compound, and among the plurality of first conductive type doped layers, at least two of the first conductive type doped layers have different compositions of group III elements; and / or the material of the second conductive type doped layer comprises a III-V group multi-component compound, and among the plurality of second conductive type doped layers, at least two of the second conductive type doped layers have different compositions of group III elements;

[0083] S4: epitaxially growing a second conductive type reflective layer on the active layer;

[0084] S5: synchronously oxidizing the multiple restriction layers to correspondingly form multiple oxide layers; wherein at least two oxide layers among the multiple oxide layers have different oxidation depths.

[0085] The embodiments of the present application control the energy band structure of the first conductive type doped layer by controlling the composition of the Group III elements in the tunnel junction layer, and control the energy band structure of the second conductive type doped layer by controlling the composition of the Group III elements in the tunnel junction layer, thereby affecting the potential barrier of the tunnel junction layer, thereby affecting the degree of diffusion of free electrons in the first conductive type doped layer to the confinement layer, and utilizing the inhibitory effect of free electrons on oxidation to achieve control of the oxidation rate of the confinement layer, thereby obtaining multiple oxide layers with different oxidation depths, thereby effectively regulating the divergence angle of the device without affecting the light field distribution and device reliability.

[0086] In this embodiment, the first conductivity type is specifically, for example, N-type, the second conductivity type is specifically, for example, P-type, the first conductivity type doping ions are specifically, for example, N-type doping ions, and the second conductivity type doping ions are specifically, for example, P-type doping ions.

[0087] Please refer to Figure 6 , perform step S1: provide a substrate 100.

[0088] In this embodiment, the material of the substrate 100 includes GaAs.

[0089] Continue to refer Figure 6 , perform step S2: epitaxially grow a first conductive type reflective layer 200 on the substrate 100. In the present embodiment, the first conductive type reflective layer 200 may specifically be an N-type DBR (Distributed Bragg Reflector) layer, which is used to reflect laser light and provide optical feedback perpendicular to the active layer. It can be understood that the first conductive type reflective layer 200 is formed by stacking a plurality of first material layers 210, wherein the plurality of first material layers 210 include a first material layer 210 with a high refractive index and a first material layer 210 with a low refractive index, and the first material layers 210 with different refractive indices are alternately stacked, and the optical thickness of each first material layer 210 is equal to 1 / 4 of the wavelength, thereby achieving its function.

[0090] Thus, the optical thickness of the first conductive type reflective layer 200 is the number of the first material layers 210*the thickness of the first material layer 210*the refractive index. In this embodiment, the thickness of the first material layer 210 is in the range of 130nm to 150nm. It can be understood that this embodiment is only taken as an example, and in the actual preparation process, it can be adaptively adjusted according to the needs of the device.

[0091] The material of the first conductive type reflective layer 200 may include Al a Ga 1-a As, wherein a is the Al component, 0≤a≤1.

[0092] The first conductive type doping ions of the first conductive type reflective layer 200 may include Si.

[0093] A stacked first material layer 210 with a high refractive index and a first material layer 210 with a low refractive index are regarded as a pair of first material layers 210. In this embodiment, the number of pairs of the first material layers 210 ranges from 30 to 40. It can be understood that this embodiment is only taken as an example, and in the actual preparation process, it can be adaptively adjusted according to the needs of the device.

[0094] Next, please refer to Figure 7, perform step S3: epitaxially grow an active layer 300 on the first conductive type reflective layer 200; wherein the active layer 300 includes at least three quantum well layers 310 stacked along the epitaxial growth direction and a confinement layer 320 and a tunnel junction layer 330 located between two adjacent quantum well layers 310, and the confinement layer 320 and the tunnel junction layer 330 between two adjacent quantum well layers 310 are sequentially stacked along the epitaxial growth direction; the tunnel junction layer 330 includes a second conductive type doped layer 3302 and a first conductive type doped layer 3301 sequentially stacked along a direction away from the substrate 100. Therefore, the energy band structure of the first conductive type doped layer 3301 is controlled by controlling the Group III element composition of the first conductive type doped layer 3301 in the tunneling junction layer 330, and the energy band structure of the second conductive type doped layer 3302 is controlled by controlling the Group III element composition of the second conductive type doped layer 3302 in the tunneling junction layer 330, and then the potential barrier of the tunneling junction layer 330 is controlled, thereby controlling the diffusion of free electrons in the N-type doped layer to the confinement layer 320, and utilizing the inhibitory effect of free electrons on oxidation to achieve control of the oxidation rate of the confinement layer 320, and obtain multiple oxide layers with different oxidation depths, thereby effectively regulating the divergence angle of the device without affecting the light field distribution and device reliability.

[0095] It can be understood that the multi-junction VCSEL can be any VCSEL with the number of quantum well layers 310 being greater than or equal to 3. This embodiment specifically takes a quad-junction VCSEL as an example for description, that is, the VCSEL in this embodiment has four quantum well layers 310 .

[0096] Specifically, epitaxially growing the active layer 300 on the first conductive type reflective layer 200 may include: sequentially epitaxially growing a first quantum well layer 311, a first confinement layer 321, a first tunneling junction layer 331, a second quantum well layer 312, a second confinement layer 322, a second tunneling junction layer 332, a third quantum well layer 313, a third confinement layer 323, a third tunneling junction layer 333, a fourth quantum well layer 314, and a fourth confinement layer 324 on the first conductive type reflective layer 200. It can be understood that in a 4-junction VCSEL, the fourth quantum well layer 314 is the last junction, and there is no quantum well layer adjacent to it, and no tunneling junction layer needs to be prepared.

[0097] The quantum well layer 310 is formed by alternating multiple quantum wells (Quantum Wells, QWs) and quantum barriers (Quantum Barriers, QBs) to control the wavelength of the device. In this embodiment, the material of the quantum well may include InGaAs or AlGaAs; the material of the quantum barrier may include AlGaAs and / or GaAsP; the wavelength range is 890-895nm.

[0098] The material of the confinement layer 320 may be a III-V group polyvalent compound having a high Al component, such as Al z Ga 1- z As (0.9<z≤1). In the subsequent oxidation process, AlGaAs will be oxidized to form oxide Al2O3, thereby completing the preparation of the oxide layer.

[0099] Please refer to Figure 2 , the tunnel junction layer 330 includes a second conductive type doped layer 3302 and a first conductive type doped layer 3301 sequentially stacked in the epitaxial direction. Usually, the tunnel junction is composed of stacked P-type doped layers and N-type doped layers. In other words, in this embodiment, the adjacent two quantum well layers 310 include an oxide layer 350, a P-type doped layer and an N-type doped layer sequentially stacked in the direction away from the substrate 100, wherein the free electrons in the N-type doped layer will diffuse into the confinement layer 320 through the P-type doped layer, and the injection of free electrons will change the charge distribution and energy band structure of the confinement layer 320, affecting the chemical reaction kinetics between the confinement layer 320 and the oxidant to change the oxidation rate, and the free electrons in the confinement layer 320 may form a charge shield on the surface of the confinement layer 320, hindering the contact between the oxidant and the confinement layer 320, thereby hindering the oxidation process. Therefore, this embodiment utilizes the effect that the free electron concentration in the confinement layer 320 affects the redox reaction and controls the free electron concentration in multiple confinement layers 320 to obtain oxide layers 350 with different oxidation depths without affecting device reliability and laser mode.

[0100] The material of the first conductive type doping layer 3301 is a group III-V multi-component compound, wherein the group III elements include at least two of Al, Ga, and In, and the group V elements include at least one of N, P, As, and Sb.

[0101] Optionally, the material of the first conductive type doping layer 3301 includes In x Ga 1-x P; wherein x is the In component, 0<x<1; among the multiple first conductivity type doped layers 3301, at least two first conductivity type doped layers 3301 have different x. It can be understood that since the electronegativity of In atoms is less than that of Ga atoms, the polarity of the formed In-P bond is lower than that of the Ga-P bond, and the binding of valence electrons is also lower. Therefore, please refer to Figure 3 , with In x Ga 1-xThe x in P gradually increases, that is, the In component gradually increases, and the In atoms gradually replace the Ga atoms and combine with the P atoms, and the binding of the valence electrons gradually decreases, so that the valence band gradually moves downward, that is, moves in the direction of lower energy. In this process, the conduction band will move downward with the valence band. In the tunnel junction, a space charge region, that is, a barrier region, is formed between the P-type doped layer and the N-type doped layer. The free electrons in the N-type doped layer need to cross the barrier to diffuse to the P-type doped layer. As the conduction band and valence band of the N-type doped layer move downward, the barrier height moves from h1 to h2, that is, the barrier gradually increases, hindering the free electrons in the N-type doped layer from diffusing to the P-type doped layer, and then hindering the free electrons from entering the limiting layer 320, reducing the influence of free electrons on the oxidation process, and increasing the oxidation rate. Therefore, by making the multiple first conductive type doped layers 3301 have different In components, the oxidation rate can be controlled to obtain an oxidation layer with different oxidation depths.

[0102] In this embodiment, the material of the first conductive type doped layer 3301 is InGaP. It is understandable that in practical applications, any suitable III-V group multi-component compound can be selected to adjust the energy band structure of the first conductive type doped layer 3301 by adjusting the composition of the III group element.

[0103] In some other embodiments, the material of the first conductive type doping layer 3301 may include Al m Ga 1-m AsSb; wherein m is the Al component, 0<m<1; among the multiple first conductivity type doped layers 3301, at least two first conductivity type doped layers 3301 have different m. It can be understood that since the electronegativity of Al atoms is greater than that of Ga atoms, the polarity of the formed Al-As bond and Al-Sb bond is higher than that of the Ga-As bond and Ga-Sb bond, and the binding of valence electrons is stronger. Therefore, please refer to Figure 3 , with Al m Ga 1-m In AsSb, m gradually increases, that is, the Al component gradually increases, and Al atoms gradually replace Ga atoms to combine with As atoms and Sb atoms, and the binding of valence electrons gradually increases, thereby gradually moving the valence band upward, that is, moving in the direction of higher energy. In this process, the conduction band will move upward with the valence band. In this process, the barrier height moves from h2 to h1, that is, the barrier gradually decreases, and the free electrons in the N-type doped layer can diffuse to the P-type doped layer with less energy, thereby accelerating the diffusion of free electrons, increasing the free electron concentration in the restriction layer 320, enhancing the influence of free electrons on the oxidation process, and reducing the oxidation rate. Thus, by making multiple N-type doped layers have different Al components, the oxidation rate can be controlled to obtain oxide layers with different oxidation depths.

[0104] The material of the second conductive type doping layer 3302 is a group III-V multi-component compound, wherein the group III elements include at least two of Al, Ga, and In, and the group V elements include at least one of N, P, As, and Sb.

[0105] Optionally, the material of the second conductive type doping layer 3302 includes Al y Ga 1-y As; wherein y is the Al component, 0<y<1; among the plurality of second conductive type doped layers 3302, at least two second conductive type doped layers 3302 have different y. It can be understood that since the electronegativity of Al atoms is greater than that of Ga atoms, the polarity of the formed Al-As bond is higher than that of the Ga-As bond, and the binding of valence electrons is stronger. Therefore, please refer to Figure 4 , with Al y Ga 1-y The y in As gradually increases, that is, the Al component gradually increases, and Al atoms gradually replace Ga atoms and combine with As atoms, and the binding of valence electrons gradually increases, so that the valence band gradually moves upward, that is, moves in the direction of higher energy. In this process, the conduction band will move upward with the valence band. In this process, the barrier height moves from h3 to h4, that is, the barrier gradually increases, and the free electrons in the N-type doped layer need to obtain more energy to diffuse to the P-type doped layer, thereby hindering the diffusion of free electrons, reducing the free electron concentration in the restriction layer 320, reducing the influence of free electrons on the oxidation process, and increasing the oxidation rate. Therefore, by making the multiple second conductive type doped layers 3302 have different Al components, the oxidation rate can be controlled to obtain an oxide layer 350 with different oxidation depths.

[0106] In this embodiment, the material of the second conductive type doped layer 3302 is AlGaAs. It is understandable that in practical applications, any suitable III-V group multi-component compound can be selected to adjust the energy band structure of the second conductive type doped layer 3302 by adjusting the composition of the III group element.

[0107] In some other embodiments, the material of the second conductive type doped layer 3302 includes In n Ga 1-n As; wherein n is the In component, 0<n<1; among the plurality of second conductivity type doped layers 3302, at least two second conductivity type doped layers 3302 have different n. It can be understood that since the electronegativity of In atoms is less than that of Ga atoms, the polarity of the formed In-As bond is lower than that of the Ga-As bond, and the binding of valence electrons is also lower. Therefore, please refer to Figure 4 , with In n Ga 1-nThe n in As gradually increases, that is, the In component gradually increases, and the In atoms gradually replace the Ga atoms to combine with the As atoms, and the binding of the valence electrons gradually decreases, so that the valence band gradually moves downward, that is, moves in the direction of lower energy. In this process, the conduction band will move downward with the valence band. In this process, the barrier height moves from h4 to h3, that is, the barrier gradually decreases, which promotes the diffusion of free electrons in the N-type doped layer to the P-type doped layer, and then facilitates the free electrons to enter the restriction layer 320, thereby enhancing the influence of free electrons on the oxidation process and reducing the oxidation rate. Thus, by making the multiple second conductive type doped layers 3302 have different In components, the oxidation rate can be controlled to obtain an oxide layer with different oxidation depths.

[0108] In this embodiment, the second conductive type doping ions are specifically, for example, P-type doping ions, which may include C; the first conductive type doping ions are specifically, for example, N-type doping ions, which may include Te and / or Se.

[0109] A tunneling junction layer 330 is provided between adjacent quantum well layers 310 of the VCSEL as a connection, and carrier redistribution can be achieved through quantum tunneling to improve the luminous efficiency of the device. In order to better produce the tunneling effect, the N-type doped layer and the P-type doped layer in the tunneling junction are usually heavily doped, that is, the N-type doped layer can also be called "N-type heavily doped layer" or "N++ layer", and the P-type doped layer can also be called "P-type heavily doped layer" or "P++ layer".

[0110] The doping concentration of N-type doping ions in the N-type doping layer may range from 4E18 to 5E19; and the doping concentration of P-type doping ions in the P-type doping layer may range from 1E19 to 1E20.

[0111] Optionally, among the plurality of first conductive type doped layers 3301, at least two first conductive type doped layers 3301 have different doping concentrations of first conductive type doped ions. If there are more N-type doped ions in the N-type doped layer, there are more free electrons therein, and then more free electrons diffused into the confinement layer 320, and the influence on the oxidation rate is greater, and vice versa. Thus, by controlling the concentration of the first conductive type doped ions in the plurality of first conductive type doped layers 3301, the corresponding confinement layer 320 can have different concentrations of free electrons, and the oxidation depth can be further controlled.

[0112] Optionally, refer to Figure 7The active layer 300 further includes a plurality of spacer layers 340, each of which is disposed between the confinement layer 320 and the tunneling junction layer 330 between two adjacent quantum well layers 310; at least two of the plurality of spacer layers 340 have different thicknesses. Specifically, the spacer layers 340 include a first spacer layer 341 disposed between the first confinement layer 321 and the first tunneling junction layer 331, a second spacer layer 342 disposed between the second confinement layer 322 and the second tunneling junction layer 332, and a third spacer layer 343 disposed between the third confinement layer 323 and the third tunneling junction layer 333.

[0113] After the free electrons jump out of the tunnel junction layer 330, they still need to cross the spacer layer 340 to reach the confinement layer 320. In this process, the free electrons have a limited diffusion distance due to their lifespan. By controlling the thickness of multiple spacer layers 340, the corresponding confinement layers 320 can have different concentrations of free electrons, thereby further controlling the oxidation depth.

[0114] The thickness L of the spacer layer 340 satisfies nL=m*λ / 2, where n is the refractive index, m is an integer, and λ is the wavelength. It can be understood that the thickness L of the spacer layer is an integer multiple of half the wavelength, thereby ensuring effective reflection and resonant amplification of light and ensuring normal operation of the device.

[0115] However, if the thickness of the spacer layer 340 is too large, the free electrons jumping out of the tunneling junction layer 330 are blocked by the spacer layer 340, that is, the oxidation rate of the limiting layer 320 will not be affected by the free electrons in the N-type doped layer, and multiple oxide layers 350 with different oxidation depths cannot be obtained, and then the divergence angle of the device cannot be adjusted. Therefore, the thickness of the spacer layer 340 can be less than or equal to 200nm.

[0116] Next, please refer to Figure 8 , step S4 is performed: epitaxially growing a second conductive type reflective layer 400 on the active layer 300. In this embodiment, the second conductive type reflective layer 400 is specifically, for example, a P-type DBR layer. It can be understood that the second conductive type reflective layer 400 is formed by stacking a plurality of second material layers 410, wherein the plurality of second material layers 410 have high and low refractive indices, the second material layers 410 with different refractive indices are alternately stacked, and the optical thickness of the second material layer 410 is equal to 1 / 4 of the wavelength, thereby achieving its function.

[0117] In this embodiment, the optical thickness of the second material layer 410 may be the same as the optical thickness of the first material layer 210 , and the material of the second material layer 410 may be the same as the material of the first material layer 210 .

[0118] The second conductive type doping ions of the second conductive type reflective layer 400 may include C.

[0119] Optionally, the optical thickness of the second conductive type reflective layer 400 is less than the optical thickness of the first conductive type reflective layer 200. The light-emitting surface of the device is located on the second conductive type reflective layer 400. If the optical thickness of the second conductive type reflective layer 400 is too large, it may reflect too much light, making it difficult for the light to escape from the device. Therefore, setting the optical thickness of the second conductive type reflective layer 400 to be less than the optical thickness of the first conductive type reflective layer 200 can increase the transmittance of the second conductive type reflective layer 400 and improve the light extraction efficiency of the device.

[0120] A stacked second material layer 410 with a high refractive index and a second material layer 410 with a low refractive index are regarded as a pair of second material layers 410. Optionally, the logarithm of the second material layer 410 is smaller than the logarithm of the first material layer 210, thereby making the optical thickness of the second conductive type reflective layer 400 smaller than the optical thickness of the first conductive type reflective layer 200, thereby improving the light extraction efficiency of the device. In this embodiment, the logarithm of the second material layer 410 of the second conductive type reflective layer 400 ranges from 15 to 20. It can be understood that this embodiment is only taken as an example, and in the actual preparation process, it can be adaptively adjusted according to the needs of the device.

[0121] Please refer to Fig. 9 The preparation method further includes: forming a contact layer 500 on the second conductive type reflective layer 400 .

[0122] In this embodiment, the material of the contact layer 500 may include GaAs.

[0123] It is understandable that in order to reduce the contact resistance between the contact layer 500 and the metal electrode, the contact layer 500 may be a highly doped p-type material layer, that is, the contact layer 500 may be called a “P+ layer.” The concentration of the P-type doping ions in the contact layer 500 is greater than 4E19.

[0124] Finally, please refer to Fig.10, executing step S5: synchronously oxidizing the multiple confinement layers 320 to form multiple oxide layers 350; wherein, among the multiple oxide layers 350, at least two oxide layers 350 have different oxidation depths. Thus, by controlling the III group element composition of the first conductive type doped layer 3301 in the tunneling junction layer 330, the energy band structure of the first conductive type doped layer 3301 is controlled, and by controlling the III group element composition of the second conductive type doped layer 3302 in the tunneling junction, the energy band structure of the second conductive type doped layer 3302 is controlled, and then the potential barrier of the tunneling junction layer 330 is affected, thereby affecting the degree of diffusion of free electrons in the first conductive type doped layer 3301 to the confinement layer 320, and utilizing the inhibitory effect of free electrons on oxidation to achieve control of the oxidation rate of the confinement layer 320, and obtain multiple oxide layers 350 with different oxidation depths, and effectively control the divergence angle of the device without affecting the light field distribution and device reliability.

[0125] Specifically, multiple confinement layers 320 are oxidized synchronously to form multiple oxide layers 350, including: the first confinement layer 321 is oxidized to form the first oxide layer 351; the second confinement layer 322 is oxidized to form the second oxide layer 352; the third confinement layer 323 is oxidized to form the third oxide layer 353; the fourth confinement layer 324 is oxidized to form the fourth oxide layer 354. It can be understood that in the 4-junction VCSEL shown in this embodiment, the fourth quantum well layer 314 is the last junction, there is no quantum well layer adjacent to it, and no tunneling junction layer is prepared. Therefore, the process of oxidizing the fourth confinement layer 324 to form the fourth oxide layer 354 is not affected by free electrons. It can be understood that Fig.10 The example only shows the situation where the oxidation depths of the first oxide layer 351 , the second oxide layer 352 and the third oxide layer 353 are all different. In practical applications, the oxidation depth can be adjusted according to the needs of the device, thereby adjusting the divergence angle of the device.

[0126] It should be noted that the VCSEL embodiment provided in the present application and the VCSEL preparation method embodiment belong to the same concept; the technical features in the technical solutions recorded in the embodiments can be arbitrarily combined without conflict. However, it should be further noted that the VCSEL provided in the embodiment of the present application, the combination of its various technical features can already solve the technical problem to be solved by the present application; therefore, the VCSEL provided in the embodiment of the present application may not be limited by the VCSEL preparation method provided in the embodiment of the present application, and any VCSEL prepared by the preparation method that can form the VCSEL structure provided in the embodiment of the present application is within the scope of protection of the present application.

[0127] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present application that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present application and do not limit the scope of protection of the patent of this application.

Claims

1. A vertical cavity surface emitting laser, characterized in that: It comprises a substrate, a first conductive type reflective layer, an active layer and a second conductive type reflective layer stacked in sequence; wherein, The active layer includes at least three quantum well layers stacked along the thickness direction of the substrate, and an oxide layer and a tunnel junction layer located between two adjacent quantum well layers, and the oxide layer and the tunnel junction layer between two adjacent quantum well layers are stacked in sequence along a direction away from the substrate; The tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer sequentially stacked in a direction away from the substrate; The material of the first conductive type doping layer includes a III-V group compound, and among the plurality of the first conductive type doping layers, at least two of the first conductive type doping layers have different compositions of the III group elements; and / or, the material of the second conductive type doping layer includes a III-V group compound, and among the plurality of the second conductive type doping layers, at least two of the second conductive type doping layers have different compositions of the III group elements; Among the multiple oxide layers, at least two oxide layers have different oxidation depths.

2. The vertical cavity surface emitting laser according to claim 1, characterized in that: The material of the first conductive type doping layer includes In x Ga 1-x P, wherein 0<x<1; among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different x.

3. The vertical cavity surface emitting laser according to claim 1, characterized in that: The material of the second conductive type doped layer includes Al y Ga 1-y As, wherein 0<y<1; among the plurality of the second conductivity type doped layers, at least two of the second conductivity type doped layers have different y.

4. The vertical cavity surface emitting laser according to any one of claims 1 to 3, characterized in that: Among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different doping concentrations of first conductivity type doped ions.

5. The vertical cavity surface emitting laser according to any one of claims 1 to 3, characterized in that: The active layer further comprises a plurality of spacer layers, each of which is respectively arranged between the oxide layer and the tunnel junction layer between two adjacent quantum well layers; among the plurality of spacer layers, at least two of the spacer layers have different thicknesses.

6. A method for preparing a vertical cavity surface emitting laser, characterized in that: The preparation method comprises: providing a substrate; epitaxially growing a first conductive type reflective layer on the substrate; An active layer is epitaxially grown on the first conductive type reflective layer; wherein the active layer comprises at least three quantum well layers stacked along the epitaxial growth direction and a confinement layer and a tunnel junction layer located between two adjacent quantum well layers, the confinement layer and the tunnel junction layer between two adjacent quantum well layers are sequentially stacked along the epitaxial growth direction; the tunnel junction layer comprises a second conductive type doped layer and a first conductive type doped layer sequentially stacked in a direction away from the substrate; The material of the first conductive type doping layer includes a III-V group compound, and among the plurality of the first conductive type doping layers, at least two of the first conductive type doping layers have different compositions of the III group elements; and / or, the material of the second conductive type doping layer includes a III-V group compound, and among the plurality of the second conductive type doping layers, at least two of the second conductive type doping layers have different compositions of the III group elements; epitaxially growing a second conductive type reflective layer on the active layer; The plurality of restriction layers are oxidized synchronously to form a plurality of oxide layers accordingly; wherein, among the plurality of oxide layers, at least two oxide layers have different oxidation depths.

7. The method for preparing a vertical cavity surface emitting laser according to claim 6, characterized in that: The material of the first conductive type doping layer includes In x Ga 1-x P, wherein 0<x<1; among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different x.

8. The method for preparing a vertical cavity surface emitting laser according to claim 6, characterized in that: The material of the second conductive type doped layer includes Al y Ga 1-y As, wherein 0<y<1; among the plurality of the second conductivity type doped layers, at least two of the second conductivity type doped layers have different y.

9. The method for preparing a vertical cavity surface emitting laser according to claim 6, characterized in that: Among the plurality of first conductivity type doped layers, at least two of the first conductivity type doped layers have different doping concentrations of first conductivity type doped ions.

10. The method for preparing a vertical cavity surface emitting laser according to claim 6, characterized in that: The active layer further includes a plurality of spacer layers, each of which is respectively arranged between the confinement layer and the tunnel junction layer between two adjacent quantum well layers.

Images