Vertical cavity surface emitting laser and preparation method thereof

Abstract

The embodiments of the present application relate to a vertical cavity surface emitting laser and a method for preparing the same, wherein the vertical cavity surface emitting laser comprises a substrate, a first conductive type reflective layer, an active layer, and a second conductive type reflective layer stacked in sequence; the active layer comprises at least three quantum well layers, an oxide layer, and a tunneling junction layer; the tunneling junction layer comprises a second conductive type doped layer and a first conductive type doped layer; the material of the first conductive type doped layer comprises a III-V group polynary compound, and among the multiple 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 polynary compound, and among the multiple second conductive type doped layers, at least two of the second conductive type doped layers have different compositions of group III elements; and among the multiple oxide layers, at least two of the oxide layers have different oxidation depths. Thus, the divergence angle of the device is effectively 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 become an extremely attractive low-cost light source due to its advantages such as low power consumption, surface emission, and high modulation bandwidth. As the requirements for VCSEL power and divergence angle continue to increase in the field, the epitaxial design of the device has shifted from single junction to multi-junction. The active layer of a multi-junction VCSEL is composed of multiple connected quantum well layers. Each quantum well layer can generate photons, and the photons can be further amplified by adjacent quantum well layers to increase the output power of the laser. The number of oxide layers in a multi-junction VCSEL is large. The oxide layers can control the current and light field distribution. By regulating the oxidation depth of multiple oxide layers, the divergence angle that meets the requirements can be obtained.

[0003] During the fabrication process, the oxide layer is typically formed by oxidizing the AlGaAs confinement layer using a wet oxygen process. Currently, the divergence angle is often controlled by varying the thickness of each confinement layer or the Al content within it to obtain oxide layers with varying oxidation depths. However, varying the confinement layer thickness inevitably alters the light field distribution in the active layer, affecting the laser output mode. Furthermore, excessively high Al content in the confinement layer can easily cause the oxide layer to cleave, impacting device reliability.

[0004] Therefore, how to control 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, wherein the oxide layer and the tunnel junction layer between two adjacent quantum well layers are stacked in sequence in a direction away from the substrate;

[0008] The tunnel junction layer includes 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 doped layer includes a Group III-V multinary 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 includes a Group III-V multinary 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;

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

[0011] In conjunction with the first aspect of the present application, in an optional embodiment, 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 conductive type doped layers, at least two of the first conductive type doped layers have different x.

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

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

[0014] In combination with the first aspect of the present application, in an optional embodiment, the active layer further 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] Epitaxially growing an active layer on the first conductive type reflective layer; wherein the active layer includes at least three quantum well layers stacked along the epitaxial growth direction, and a confinement layer and a tunneling junction layer located between two adjacent quantum well layers, the confinement layer and the tunneling junction layer between two adjacent quantum well layers being sequentially stacked along the epitaxial growth direction; the tunneling junction layer includes a second conductive type doped layer and a first conductive type doped layer being sequentially stacked in a direction away from the substrate;

[0019] The material of the first conductive type doped layer includes a Group III-V multinary 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 includes a Group III-V multinary 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;

[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 corresponding oxide layers; wherein, among the plurality of oxide layers, at least two oxide layers have different oxidation depths.

[0022] In conjunction with the second aspect of the present application, in an optional embodiment, 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 conductive type doped layers, at least two of the first conductive type doped layers have different x.

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

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

[0025] In combination with the second aspect of the present application, in an optional embodiment, 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 preparation method provided in the embodiments of the present application control the energy band structure of the first conductive type doped layer in the tunneling junction layer by controlling the composition of the Group III elements in the first conductive type doped layer, and / or control the energy band structure of the second conductive type doped layer in the tunneling junction by controlling the composition of the Group III elements in the second conductive type doped layer, 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. By utilizing the inhibitory effect of free electrons on oxidation, the oxidation depth of the oxide layer is controlled, 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 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 view of a vertical cavity surface emitting laser provided in an embodiment of the present application;

[0030] Figure 2 Schematic diagram of the structure of the oxide layer and 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 flow chart of a method for preparing a vertical cavity surface emitting laser according to 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 herein will be described in more detail below with reference to the accompanying drawings. Although 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. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0036] In the following description, numerous specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures 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 being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. Although the terms first, second, third, etc. may 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 merely 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. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present application.

[0039] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. In addition to the orientations shown in the figures, spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the drawings is flipped, then the elements or features described as "under the other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in 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 limit the present application. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", 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 fully 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. However, 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 the vertical cavity surface emitting laser provided in the embodiment of the present application. Figure 1 and Figure 2 As shown, the vertical cavity surface emitting laser includes: 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 doped layer 3301 includes a Group III-V multinary compound, and among the plurality of first conductive type doped layers 3301 , at least two of the first conductive type doped layers 3301 have different compositions of Group III elements; and / or the material of the second conductive type doped layer 3302 includes a Group III-V multinary compound, and among the plurality of second conductive type doped layers 3302 , at least two of the second conductive type doped 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 Group III element composition of the first conductive type doped layer 3301 in the tunnel junction layer 330, the energy band structure of the first conductive type doped layer 3301 is controlled, and by controlling the Group III element composition of the second conductive type doped layer 3302 in the tunnel junction, the energy band structure of the second conductive type doped layer 3302 is controlled, thereby affecting the potential barrier of the tunnel junction layer 330, 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 an N-type, for example, and the second conductivity type is specifically a P-type, for example.

[0049] The oxide layer 350 is formed by oxidation of the restriction layer. The material of the restriction layer is usually a III-V group multinary compound with a high Al content, such as Al z Ga 1-z As (0.9 < z ≤ 1). In actual fabrication, a wet oxidation process is typically used to cause some AlGaAs to react with the oxidant, H2O vapor, to form Al2O3. The entire oxidation process consists of two steps: the reaction of H2O vapor molecules with Al and the inward diffusion of H2O vapor molecules.

[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 gradually diffuse inward, gradually oxidizing the confinement layer from the periphery to the center. Under certain reaction time, oxidation temperature, and H2O vapor flow rate control, the final oxide layer 350 prepared includes an unoxidized portion located at the center, namely, an oxidation hole, through which electrons can pass. The oxide layer 350 also includes an oxidized portion located at the periphery, where electrons are blocked. Therefore, by regulating the oxidation depth of multiple oxide layers 350, oxide layers 350 with different oxide hole diameters can be obtained. The oxide holes are used to limit the laser transverse mode and provide vertical optical confinement to adjust the divergence angle.

[0055] It is not difficult to understand that Al z Ga 1-z The higher the Al content in As, the faster the oxidation rate. Given a constant reaction time, the deeper the oxidation depth of oxide layer 350. The thicker the confinement layer, the larger its contact surface with H2O vapor, the faster the oxidation rate. Given a constant reaction time, the deeper the oxidation depth of oxide layer 350. Conversely, the lower the Al content or the thinner the confinement layer, the slower the oxidation rate and the shallower the oxidation depth. Since multiple confinement layers in active layer 300 are oxidized simultaneously during device fabrication, the oxidation rate can be controlled by regulating the Al content and thickness of these confinement layers, achieving different oxidation depths within a given timeframe. However, an excessively high Al content can make the resulting oxide layer 350 extremely susceptible to cleavage, impacting device reliability. Changing the thickness of confinement layer 320 can alter the light field distribution in active layer 300, affecting the laser output mode.

[0056] Please refer to Figure 1 In a VCSEL, a tunneling junction layer 330 connects adjacent quantum well layers 310 and is used to provide carrier injection between different quantum well layers 310. The tunneling junction is generally 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 2Between two adjacent quantum well layers 310, there is an oxide layer 350, a second conductivity type doped layer 3302 (P-type doped layer), and a first conductivity type doped layer 3301 (N-type doped layer), stacked sequentially in a direction away from the substrate 100. Free electrons in the N-type doped layer diffuse into the confinement layer through the P-type doped layer. 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, thereby changing the oxidation rate. Furthermore, the free electrons in the confinement layer may form a charge shield on the surface of the confinement layer, hindering contact between the oxidant and the confinement layer, thereby hindering the oxidation process. Therefore, this embodiment utilizes the effect of free electron concentration on the redox reaction to control the free electron concentration in multiple confinement layers, thereby obtaining oxide layers with different oxidation depths without affecting device reliability and laser mode.

[0057] Group III-V multinary 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 multinary compound materials, changes in the Group III element composition can lead to changes in the material's properties, such as electron mobility, bandgap, and photoelectric conversion efficiency. Specifically, if the composition of a particular Group III element increases, that Group III atom will replace other Group III atoms and bind to Group V atoms. Different Group III atoms have different electronegativities, resulting in different polarities in the covalent bonds formed between Group III and Group V elements, and thus different binding effects on valence electrons. The strength of valence electron binding 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. Consequently, changes in the position of the conduction and valence bands of the N-type and / or P-type doped layers in the tunneling junction affect the potential barrier between the N-type and P-type doped layers. Free electrons in the N-type doped layer may require more or less energy to cross the potential barrier to the P-type doped layer, which in turn affects the free electrons' entry into the confinement layer.

[0058] The material of the first conductive type doped layer 3301 is a Group III-V multinary 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 doped layer 3301 includes In x Ga 1-x P; where 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 As the x in P gradually increases, that is, the In component gradually increases, In atoms gradually replace Ga atoms and bind to P atoms, gradually reducing the binding of valence electrons. As a result, the valence band gradually shifts downward, that is, toward lower energy. During this process, the conduction band also shifts downward along with the valence band. In the tunnel junction, a space charge region, namely a potential barrier region, is formed between the P-type doped layer and the N-type doped layer. Free electrons in the N-type doped layer must cross the potential barrier to diffuse to the P-type doped layer. As the conduction band and valence band of the N-type doped layer shift downward, the potential barrier height shifts from h1 to h2, that is, the potential barrier gradually increases, hindering the diffusion of free electrons in the N-type doped layer to the P-type doped layer, thereby preventing free electrons from entering the confinement layer, reducing the impact 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 oxide layers 350 with different oxidation depths.

[0060] This embodiment specifically uses InGaP as the material of the first conductivity type doped layer 3301. It is understood that in practical applications, any suitable III-V multi-component compound can be selected, and the energy band structure of the first conductivity type doped layer 3301 can be adjusted by regulating the composition of the III group elements therein.

[0061] In some other embodiments, the material of the first conductive type doped layer 3301 may include Al m Ga 1-m AsSb; where 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, meaning the Al content gradually increases. Al atoms gradually replace Ga atoms and bind to As and Sb atoms, gradually strengthening the binding of valence electrons. As a result, the valence band gradually shifts upward, that is, toward higher energy. During this process, the conduction band also shifts upward along with the valence band. During this process, the barrier height shifts from h2 to h1, meaning the barrier gradually decreases. Free electrons in the N-type doped layer gain less energy and diffuse into the P-type doped layer. This accelerates the diffusion of free electrons, increases the free electron concentration in the confinement layer, enhances the influence of free electrons on the oxidation process, and reduces the oxidation rate. Therefore, by having multiple N-type doped layers with different Al content, the oxidation rate can be controlled, resulting in oxide layers 350 with different oxidation depths.

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

[0063] The material of the second conductive type doped layer 3302 is a Group III-V multinary 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 doped layer 3302 includes Al y Ga 1-y As; where 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, Al atoms gradually replace Ga atoms and combine with As atoms, and the binding of valence electrons gradually increases. As a result, the valence band gradually moves upward, that is, moves toward a higher energy direction. In this process, the conduction band will move upward along with the valence band. In this process, the barrier height moves from h3 to h4, that is, the barrier gradually increases. 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 confinement layer, reducing the impact 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.

[0065] In this embodiment, AlGaAs is used as the material of the second conductive type doped layer 3302. It is understood that in practical applications, any suitable III-V multi-component compound can be selected, and the energy band structure of the second conductive type doped layer 3302 can be adjusted by regulating the composition of the III group elements therein.

[0066] In some other embodiments, the material of the second conductive type doped 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 In atoms gradually replace Ga atoms and combine with As atoms, and the binding of valence electrons gradually decreases. As a result, the valence band gradually moves downward, that is, moves toward a lower energy direction. In this process, the conduction band will move downward along with the valence band. In this process, the barrier height moves from h4 to h3, that is, the barrier gradually decreases, promoting the diffusion of free electrons in the N-type doped layer to the P-type doped layer, which in turn is conducive to the free electrons entering the confinement layer, enhancing the influence of free electrons on the oxidation process, and reducing the oxidation rate. Therefore, 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 is understood that when the material of the second conductivity type doped layer 3302 is a Group III-V multinary compound, the material of the first conductivity type doped layer 3301 can be any suitable semiconductor material, and the material of the first conductivity type doped layer 3301 is lattice-matched with the material of the second conductivity type doped layer 3302. In this embodiment, the material of the second conductivity type doped layer 3302 can be AlGaAs, and the material of the first conductivity type doped layer 3301 can be GaAs.

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

[0069] Setting up a tunnel junction between adjacent quantum well layers 310 in a VCSEL as a connection can achieve carrier redistribution through quantum tunneling, thereby improving the device's luminous efficiency. To better produce the tunneling effect, the N-type and P-type doped layers in the tunnel junction are usually heavily doped. The N-type doped layer can also be referred to as an "N-type heavily doped layer" or "N++ layer," and the P-type doped layer can also be referred to as a "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; the doping concentration of P-type doping ions in the P-type doping layer may range from 1E19 to 1E20.

[0071] Optionally, at least two of the multiple first conductivity type doped layers 3301 have different doping concentrations of the first conductivity type dopant ions. The more N-type dopant ions in an N-type doped layer, the more free electrons therein are, and consequently, the more free electrons diffuse into the confinement layer, which has a greater impact on the oxidation rate. Similarly, the same applies vice versa. Thus, by controlling the concentrations of the first conductivity type dopant ions in the multiple first conductivity type doped layers 3301, the corresponding confinement layers can have different concentrations of free electrons, further controlling the oxidation depth.

[0072] Optionally, refer to Figure 1 The active layer 300 also includes multiple spacer layers 340, each disposed between the oxide layer 350 and the tunneling junction layer 330 between two adjacent quantum well layers 310. At least two of the multiple spacer layers 340 have different thicknesses. After free electrons escape from the tunneling junction layer 330, they must traverse the spacer layers 340 to reach the confinement layer. During this process, the free electrons have a limited diffusion distance due to their lifetime. By controlling the thickness of the multiple spacer layers 340, different concentrations of free electrons can be achieved in the corresponding confinement layer, further controlling the oxidation depth.

[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 is 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, ensuring normal operation of the device.

[0074] However, if the thickness of the spacer layer 340 is too large, the free electrons that escape from the tunneling junction layer 330 will be blocked by the spacer layer 340. This means that the oxidation rate of the confinement layer 320 will not be affected by the free electrons. Consequently, it will be impossible to obtain multiple oxide layers 350 with different oxidation depths, and the divergence angle of the device will not be adjustable. Therefore, the thickness of the spacer layer 340 can be less than or equal to 200 nm.

[0075] In this 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 understood that to reduce the contact resistance between the contact layer 500 and the metal electrode, the contact layer 500 can be a highly doped p-type material layer, that is, the contact layer 500 can be called a "P+ layer." The concentration of the P-type dopant 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 includes 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 the two adjacent quantum well layers are sequentially stacked along the epitaxial growth direction; the tunnel junction layer includes 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 doped layer includes a Group III-V multinary 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 includes a Group III-V multinary 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: performing synchronous oxidation on the multiple confinement layers to correspondingly form multiple oxide layers; wherein, among the multiple oxide layers, at least two 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. By utilizing the inhibitory effect of free electrons on oxidation, the oxidation rate of the confinement layer is controlled, and multiple oxide layers with different oxidation depths are obtained. As a result, the divergence angle of the device is effectively regulated without affecting the light field distribution and device reliability.

[0086] In this embodiment, the first conductivity type is specifically N-type, the second conductivity type is specifically P-type, the first conductivity type dopant ions are specifically N-type dopant ions, and the second conductivity type dopant ions are specifically P-type dopant 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 this embodiment, the first conductive type reflective layer 200 can be specifically 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 multiple first material layers 210, wherein the multiple 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. 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] Therefore, the optical thickness of the first conductive type reflective layer 200 is the number of 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 ranges from 130 nm to 150 nm. It will be understood that this embodiment is merely an example and can be adaptively adjusted according to the needs of the device during actual manufacturing.

[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 dopant 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 is considered a pair of first material layers 210. In this embodiment, the number of pairs of first material layers 210 ranges from 30 to 40. It is understood that this embodiment is merely an example and can be adaptively adjusted according to device requirements during actual fabrication.

[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 stacked in sequence 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 stacked in sequence along a direction away from the substrate 100. Therefore, by controlling the III group element composition of the first conductive type doped layer 3301 in the tunneling junction layer 330, the band structure of the first conductive type doped layer 3301 is controlled; by controlling the III group element composition of the second conductive type doped layer 3302 in the tunneling junction layer 330, the band structure of the second conductive type doped layer 3302 is controlled, 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. By utilizing the inhibitory effect of free electrons on oxidation, the oxidation rate of the confinement layer 320 is controlled, and multiple oxide layers with different oxidation depths are obtained. Therefore, the divergence angle of the device is effectively regulated 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 will be appreciated that in a four-junction VCSEL, the fourth quantum well layer 314 is the last junction and has no adjacent quantum well layer, so there is no need to form a tunneling junction layer.

[0097] The quantum well layer 310 is formed by alternating layers of quantum wells (QWs) and quantum barriers (QBs), thereby controlling the wavelength of the device. In this embodiment, the quantum wells can be made of InGaAs or AlGaAs; the quantum barriers can be made of AlGaAs and / or GaAsP; and the wavelength range is 890-895 nm.

[0098] The material of the confinement layer 320 can be a III-V group multinary compound with a high Al content, 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 tunneling junction layer 330 includes a second conductive type doped layer 3302 and a first conductive type doped layer 3301 stacked in sequence along the epitaxial direction. Typically, a tunneling junction is formed by stacked P-type doped layers and N-type doped layers. In other words, in this embodiment, the gap between two adjacent quantum well layers 310 includes an oxide layer 350, a P-type doped layer, and an N-type doped layer stacked in sequence along a direction away from the substrate 100. Free electrons in the N-type doped layer diffuse into the confinement layer 320 through the P-type doped layer. The injection of free electrons changes 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, thereby changing the oxidation rate. Furthermore, the free electrons in the confinement layer 320 may form a charge shield on the surface of the confinement layer 320, hindering 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 doped layer 3301 is a Group III-V multinary 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 doped layer 3301 includes In x Ga 1-x P; where 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-xAs the x in P gradually increases, that is, the In component gradually increases, In atoms gradually replace Ga atoms and combine with P atoms, and the binding of valence electrons gradually decreases. As a result, the valence band gradually shifts downward, that is, toward lower energy. During this process, the conduction band will shift downward along with the valence band. In the tunnel junction, a space charge region, namely a potential barrier region, is formed between the P-type doped layer and the N-type doped layer. Free electrons in the N-type doped layer need to cross the potential barrier to diffuse to the P-type doped layer. As the conduction band and valence band of the N-type doped layer shift downward, the potential barrier height shifts from h1 to h2, that is, the potential 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 confinement layer 320, reducing the impact 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 oxide layers with different oxidation depths.

[0102] This embodiment specifically uses InGaP as the material of the first conductivity type doped layer 3301. It is understood that in practical applications, any suitable III-V multi-component compound can be selected, and the energy band structure of the first conductivity type doped layer 3301 can be adjusted by regulating the composition of the III group elements therein.

[0103] In some other embodiments, the material of the first conductive type doped layer 3301 may include Al m Ga 1-m AsSb; where 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 along 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 obtain less energy to diffuse to the P-type doped layer, thereby accelerating the diffusion of free electrons, increasing the free electron concentration in the confinement layer 320, 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 oxide layers with different oxidation depths.

[0104] The material of the second conductive type doped layer 3302 is a Group III-V multinary 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 doped layer 3302 includes Al y Ga 1-y As; where 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, Al atoms gradually replace Ga atoms and combine with As 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 along 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 confinement 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, AlGaAs is used as the material of the second conductive type doped layer 3302. It is understood that in practical applications, any suitable III-V multi-component compound can be selected, and the energy band structure of the second conductive type doped layer 3302 can be adjusted by regulating the composition of the III group elements therein.

[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 In atoms gradually replace Ga atoms and combine with As atoms, and the binding of valence electrons gradually decreases. As a result, the valence band gradually moves downward, that is, moves toward a lower energy direction. In this process, the conduction band will move downward along with the valence band. In this process, the barrier height moves from h4 to h3, that is, the barrier gradually decreases, promoting the diffusion of free electrons in the N-type doped layer to the P-type doped layer, which is conducive to the free electrons entering the confinement layer 320, enhancing the influence of free electrons on the oxidation process, and reducing the oxidation rate. Therefore, by making the multiple second conductive type doped layers 3302 have different In components, the oxidation rate can be controlled to obtain oxide layers with different oxidation depths.

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

[0109] A tunneling junction layer 330 is provided between adjacent quantum well layers 310 of a VCSEL to serve as a connection. This allows for carrier redistribution through quantum tunneling, improving the device's luminous efficiency. To enhance the tunneling effect, the N-type and P-type doped layers in the tunneling junction are typically heavily doped. The N-type doped layer is also referred to as an "N-type heavily doped layer" or "N++ layer," and the P-type doped layer is also referred to as a "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; the doping concentration of P-type doping ions in the P-type doping layer may range from 1E19 to 1E20.

[0111] Optionally, at least two of the multiple first conductivity type doped layers 3301 have different doping concentrations of the first conductivity type dopant ions. The more N-type dopant ions in an N-type doped layer, the more free electrons therein are. Consequently, more free electrons diffuse into the confinement layer 320, which has a greater impact on the oxidation rate. Similarly, the same applies vice versa. Thus, by controlling the concentrations of the first conductivity type dopant ions in the multiple first conductivity type doped layers 3301, different concentrations of free electrons can be achieved in the corresponding confinement layer 320, further controlling the oxidation depth.

[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 positioned between the first confinement layer 321 and the first tunneling junction layer 331, a second spacer layer 342 positioned between the second confinement layer 322 and the second tunneling junction layer 332, and a third spacer layer 343 positioned between the third confinement layer 323 and the third tunneling junction layer 333.

[0113] 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 320. During 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, 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 is 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, ensuring normal operation of the device.

[0115] However, if the thickness of the spacer layer 340 is too large, the free electrons that escape from the tunneling junction layer 330 will be blocked by the spacer layer 340. This means that the oxidation rate of the confinement layer 320 will not be affected by the free electrons in the N-type doped layer. Consequently, it will be impossible to obtain multiple oxide layers 350 with different oxidation depths, and the divergence angle of the device will not be adjustable. Therefore, the thickness of the spacer layer 340 can be less than or equal to 200 nm.

[0116] Next, please refer to Figure 8 , executing step S4: 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 is understood that the second conductive type reflective layer 400 is formed by stacking multiple second material layers 410. The multiple second material layers 410 have two refractive indices, high and low. The second material layers 410 with different refractive indices are alternately stacked, and the optical thickness of the second material layers 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 dopant 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 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 high-refractive-index second material layer 410 and a low-refractive-index second material layer 410 are considered a pair of second material layers 410. Optionally, the number of pairs of the second material layers 410 is smaller than the number of pairs of the first material layer 210. This allows the optical thickness of the second conductive type reflective layer 400 to be 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 number of pairs of the second material layers 410 of the second conductive type reflective layer 400 ranges from 15 to 20. It will be appreciated that this embodiment is merely an example and can be adjusted adaptively according to the needs of the device during actual manufacturing.

[0121] Please refer to Figure 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 understood that to reduce the contact resistance between the contact layer 500 and the metal electrode, the contact layer 500 can be a highly doped p-type material layer, that is, the contact layer 500 can be called a "P+ layer." The concentration of the P-type dopant ions in the contact layer 500 is greater than 4E19.

[0124] Finally, please refer to Figure 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 Group III element composition of the first conductivity type doped layer 3301 in the tunneling junction layer 330, the energy band structure of the first conductivity type doped layer 3301 is controlled. By controlling the Group III element composition of the second conductivity type doped layer 3302 in the tunneling junction, the energy band structure of the second conductivity type doped layer 3302 is controlled. This, in turn, affects the potential barrier of the tunneling junction layer 330, thereby affecting the degree of diffusion of free electrons in the first conductivity type doped layer 3301 into the confinement layer 320. Utilizing the inhibitory effect of free electrons on oxidation, the oxidation rate of the confinement layer 320 is controlled, resulting in multiple oxide layers 350 with different oxidation depths. This effectively regulates the divergence angle of the device without affecting the light field distribution and device reliability.

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

[0126] It should be noted that the embodiments of the vertical cavity surface emitting laser provided in this application and the embodiments of the method for preparing the vertical cavity surface emitting laser belong to the same concept; the technical features in the technical solutions described in the embodiments can be arbitrarily combined without conflict. However, it should be further noted that the combination of the various technical features of the vertical cavity surface emitting laser provided in the embodiments of this application can already solve the technical problems to be solved by this application; therefore, the vertical cavity surface emitting laser provided in the embodiments of this application is not limited by the method for preparing the vertical cavity surface emitting laser provided in the embodiments of this application, and any vertical cavity surface emitting laser prepared by the preparation method that can form the vertical cavity surface emitting laser structure provided in the embodiments of this application is within the scope of protection of this application.

[0127] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the claims. Various modifications and variations may be made to 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 additional embodiments of the present application that may not be explicitly described. Therefore, the above embodiments merely illustrate several implementations of the present application and do not limit the scope of protection of the patent application.

Claims

1. A vertical cavity surface emitting laser, characterized in that: The invention 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, wherein the oxide layer and the tunnel junction layer between two adjacent quantum well layers are stacked in sequence in a direction away from the substrate; The tunnel junction layer includes 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 doped layer includes a Group III-V multinary 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 includes a Group III-V multinary 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, so that among the plurality of tunnel junction layers, at least two of the tunnel junction layers have different potential barriers; 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, wherein: 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 conductive type doped layers, at least two of the first conductive type doped layers have different x.

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

5. The vertical cavity surface emitting laser according to any one of claims 1 to 3, characterized in that: The active layer further 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.

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; Epitaxially growing an active layer on the first conductive type reflective layer; wherein the active layer includes at least three quantum well layers stacked along the epitaxial growth direction, and a confinement layer and a tunneling junction layer located between two adjacent quantum well layers, the confinement layer and the tunneling junction layer between two adjacent quantum well layers being sequentially stacked along the epitaxial growth direction; the tunneling junction layer includes a second conductive type doped layer and a first conductive type doped layer being sequentially stacked in a direction away from the substrate; The material of the first conductive type doped layer includes a Group III-V multinary 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 includes a Group III-V multinary 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, so that among the plurality of tunnel junction layers, at least two of the tunnel junction layers have different potential barrier sizes; 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 corresponding oxide layers; 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, wherein: 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 conductive type doped layers, at least two of the first conductive type doped layers have different x.

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

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

10. The method for preparing a vertical cavity surface emitting laser according to claim 6, wherein: 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.

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