Vertical cavity surface emitting laser and preparation method thereof

Abstract

The invention discloses a vertical cavity surface emitting laser and a preparation method thereof, and the method comprises the steps: sequentially forming a first epitaxial layer, a sacrificial layer, a second epitaxial layer and a first DBR reflection layer on a first substrate, and the second epitaxial layer at least comprises an active layer; performing graphical processing on the first DBR reflecting layer, the second epitaxial layer and the sacrificial layer; etching the graphical sacrificial layer by adopting an electrochemical etching method so as to integrally strip the graphical second epitaxial layer and the graphical first DBR reflecting layer from the first epitaxial layer; bonding the stripped patterned first DBR reflecting layer and the stripped patterned second epitaxial layer with a second substrate; and forming a patterned second DBR reflecting layer on one side, far away from the patterned first DBR reflecting layer, of the patterned second epitaxial layer to obtain the VCSEL. By arranging the sacrificial layer to cooperate with electrochemical etching, the smoothness of the surface of the stripped epitaxial layer can be improved, so that the luminous efficiency and stability of the VCSEL are improved.

Description

Technical Field

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

[0002] Vertical-Cavity Surface-Emitting Laser (VCSEL) is a new type of semiconductor laser, usually including a bottom DBR (distributed Bragg reflector), an active layer and a top DBR. The DBR forms a resonant cavity on both sides of the active layer. The higher the reflectivity of the DBR, the more times the laser is reflected in the resonant cavity, and the stronger the intensity of the laser. Therefore, the reflectivity of the DBR has an important influence on the performance of the VCSEL.

[0003] The existing method for preparing VCSEL generally includes: forming an epitaxial layer and a first DBR layer on a first substrate; using laser lift-off (LLO) technology to peel the epitaxial layer and the first DBR layer from the substrate; bonding the peeled first DBR layer and epitaxial layer to a second substrate; forming a second DBR layer on the side of the epitaxial layer away from the first DBR layer. At this time, the first DBR layer and the second DBR layer are respectively located on the upper and lower sides of the active layer, reflecting the laser back into the resonant cavity, thereby achieving laser amplification and oscillation.

[0004] However, during the laser lift-off process, the thermal shock caused by laser irradiation can easily lead to cracking of the film layer (such as AlGaN film) in the epitaxial structure, and the thermal decomposition of AlGaN will produce hard aluminum residues, resulting in increased surface roughness, thereby increasing the scattering loss of the VCSEL.

[0005] Therefore, how to prepare a high-reflectivity DBR structure while ensuring the performance of the VCSEL device, thereby improving the luminous efficiency and stability of the VCSEL, is a technical problem that urgently needs to be solved. Summary of the invention

[0006] In view of the above problems, the present invention is proposed to provide a vertical cavity surface emitting laser and a preparation method thereof that overcome the above problems or at least partially solve the above problems. By adopting a sacrificial layer in combination with an electrochemical etching method to peel off part of the epitaxial layer, the smoothness of the surface of the peeled epitaxial layer is improved, which is conducive to forming a high-reflectivity DBR structure, thereby improving the luminous efficiency and stability of the VCSEL.

[0007] In a first aspect, a method for preparing a vertical cavity surface emitting laser is provided, the method comprising:

[0008] Forming a first epitaxial layer, a sacrificial layer, a second epitaxial layer and a first DBR reflective layer in sequence on a first substrate, wherein the second epitaxial layer at least includes an active layer;

[0009] Performing patterning on the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form at least one patterned structure on a side of the first epitaxial layer away from the first substrate, the patterned structure comprising a patterned sacrificial layer, a patterned second epitaxial layer and a patterned first DBR reflective layer;

[0010] Using an electrochemical etching method to etch away the patterned sacrificial layer in the patterned structure, so as to peel off the patterned second epitaxial layer and the patterned first DBR reflective layer as a whole from the first epitaxial layer;

[0011] Bonding the peeled-off patterned first DBR reflective layer and the patterned second epitaxial layer to a second substrate, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the second substrate;

[0012] A patterned second DBR reflective layer is formed on a side of the patterned second epitaxial layer away from the patterned first DBR reflective layer to obtain the vertical cavity surface emitting laser.

[0013] In some implementations, the patterned first DBR reflective layer and the patterned second DBR reflective layer include a plurality of first reflective layers and a plurality of second reflective layers that are alternately arranged in sequence, and the first reflective layer and the second reflective layer are HfO2 layers and SiO2 layers, respectively.

[0014] In some implementations, bonding the stripped patterned first DBR reflective layer and the patterned second epitaxial layer to a second substrate includes:

[0015] Using an organic substrate to pick up the peeled patterned first DBR reflective layer and the patterned second epitaxial layer, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the organic substrate;

[0016] The side of the organic substrate away from the patterned first DBR reflective layer and the patterned second epitaxial layer is bonded to the second substrate.

[0017] In some implementations, the electrochemical etching method is used to etch away the patterned sacrificial layer in the patterned structure, including:

[0018] Welding an electrical contact material at the edge of the first epitaxial layer, and electrically connecting the first epitaxial layer to the positive electrode of the power supply through the electrical contact material, and electrically connecting the negative electrode of the power supply to the cathode material;

[0019] The first substrate formed with the first epitaxial layer and the patterned structure is placed in an electrolyte, and the patterned sacrificial layer in the patterned structure is electrochemically etched using the first epitaxial layer as an anode and the cathode material as a cathode.

[0020] In some implementations, the electrical contact material is indium and the cathode material is platinum.

[0021] In some implementations, the patterning of the first DBR reflective layer, the second epitaxial layer, and the sacrificial layer includes:

[0022] forming a patterned photoresist layer on the first DBR reflective layer;

[0023] Etching the first DBR reflective layer, the second epitaxial layer and the sacrificial layer at the opening position of the photoresist layer to transfer the pattern on the photoresist layer to the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form the patterned first DBR reflective layer, the patterned second epitaxial layer and the patterned sacrificial layer;

[0024] The patterned photoresist layer is removed.

[0025] In some implementations, the sacrificial layer is an N-type doped AlGaN layer or an N-type doped GaN layer.

[0026] In some implementations, the first substrate and the second substrate are both sapphire substrates, the first epitaxial layer includes a nucleation layer, a buffer layer, and a current spreading layer stacked sequentially on the first substrate, and the active layer includes a plurality of quantum well layers and a plurality of quantum barrier layers alternately arranged;

[0027] The material of the nucleation layer includes AlN, and the material of the buffer layer includes Al a Ga (1-a) N, the material of the current spreading layer includes Al b Ga (1-b) N, the material of the quantum well layer includes Al k1 Ga (1-k1) N, the material of the quantum barrier layer includes Al k2 Ga (1-k2) N, a>0.5, b>0.5, k1>0.5, k2>0.5.

[0028] In some implementations, the second epitaxial layer further includes a first resonant cavity adjustment layer and a second resonant cavity adjustment layer, the first resonant cavity adjustment layer is located between the active layer and the sacrificial layer, and the second resonant cavity adjustment layer is located on a side of the active layer away from the sacrificial layer;

[0029] The first resonant cavity adjustment layer is an AlcGa(1-c)N layer, and the second resonant cavity adjustment layer is an AldGa(1-d)N layer, where c>0.5 and d>0.5.

[0030] The technical solution provided in the embodiments of the present invention has at least the following technical effects or advantages:

[0031] A vertical cavity surface emitting laser and a preparation method thereof provided by an embodiment of the present invention, wherein a sacrificial layer is formed during the growth of an epitaxial layer to divide the epitaxial layer into two parts for growth, and then the first DBR reflective layer, the second epitaxial layer including the active layer and the sacrificial layer are patterned to form at least one patterned structure on the side of the first epitaxial layer away from the first substrate. At this time, since the sacrificial layer is patterned, part of the sacrificial layer will be exposed, which is convenient for subsequent electrochemical etching to etch away the sacrificial layer, so as to peel off the patterned second epitaxial layer and the patterned first DBR reflective layer as a whole from the first epitaxial layer; then, the patterned first DBR reflective layer and the patterned second epitaxial layer after peeling are bonded to the second substrate, and the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the second substrate, and at this time, the first DBR reflective layer is located at the bottom of the active layer, which can be used as the bottom DBR layer. Finally, a patterned second DBR reflective layer is formed on the side of the patterned second epitaxial layer away from the patterned first DBR reflective layer as the top DBR layer, and the desired vertical cavity surface emitting laser can be prepared. The present invention adopts a sacrificial layer combined with an electrochemical etching method. Compared with a conventional laser lift-off method, the electrochemical etching method has higher precision and controllability, can reduce thermal shock and mechanical damage to the epitaxial layer, and make the surface of the second epitaxial layer after lift-off smoother. Furthermore, by precisely controlling the electrochemical etching process, it is possible to reduce cracking of each film layer in the second epitaxial layer and generation of aluminum residues, thereby reducing the scattering loss of the VCSEL, improving the reliability and stability of the device, and at the same time reducing the preparation cost of the VCSEL and improving production efficiency.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 is a flow chart of a method for preparing a vertical cavity surface emitting laser provided by an embodiment of the present invention;

[0035] Figure 2 is a schematic diagram of an epitaxial structure provided by an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of the structure after executing step S110;

[0037] Figure 4 is a schematic diagram of the structure after executing step S121;

[0038] Figure 5 is a schematic diagram of the structure after executing step S122;

[0039] Figure 6 yes Figure 5 a top view of the structure shown;

[0040] Figure 7 is a schematic diagram of the structure of an electrochemical etching provided by an embodiment of the present invention;

[0041] Figure 8 is a structural diagram when executing step S141;

[0042] Fig. 9 is a schematic diagram of the structure after executing step S142;

[0043] Fig.10 is a schematic diagram of the structure after executing step S150;

[0044] Fig.11 It is a schematic diagram of the relationship between the emission intensity and the pump power density of the VCSEL prepared by the preparation method provided by the present invention;

[0045] Fig.12 It is a schematic diagram of the emission spectrum of the VCSEL prepared by the preparation method provided by the present invention at different excitation levels. DETAILED DESCRIPTION

[0046] In order to better understand the above-mentioned technical scheme, the above-mentioned technical scheme will be described in detail below in combination with the accompanying drawings and specific implementation methods of the specification. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical scheme of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0047] Figure 1 is a flow chart of a method for preparing a vertical cavity surface emitting laser provided by an embodiment of the present invention, such as Figure 1As shown, the preparation method comprises:

[0048] Step S110: forming a first epitaxial layer, a sacrificial layer, a second epitaxial layer and a first DBR reflective layer in sequence on a first substrate, wherein the second epitaxial layer at least includes an active layer.

[0049] In some implementations, the first substrate is a sapphire substrate, the first epitaxial layer includes a nucleation layer, a buffer layer, and a current spreading layer stacked in sequence on the first substrate, and the active layer includes a plurality of quantum well layers and a plurality of quantum barrier layers alternately arranged. The material of the nucleation layer includes AlN, and the material of the buffer layer includes Al a Ga (1-a) N, the current spreading layer material includes Al b Ga (1-b) N, the materials of the quantum well layer include Al k1 Ga (1-k1) N, the materials of quantum barrier layer include Al k2 Ga (1-k2) N, a>0.5, b>0.5, k1>0.5, k2>0.5.

[0050] The nucleation layer is an AlN layer, and there is a small lattice mismatch and thermal expansion coefficient mismatch between AlN and the subsequent epitaxial layer (such as AlGaN), which helps to reduce stress accumulation during epitaxial growth and reduce defect density, thereby improving the crystal quality and structural integrity of the epitaxial layer. During the epitaxial growth process, the buffer layer can regulate and relieve stress caused by lattice mismatch, ensure the flatness of the epitaxial structure and reduce defects. The current expansion layer is used to enhance the lateral expansion of the current inside the chip, so that the current can be more evenly distributed throughout the active area, thereby improving the light extraction efficiency and electrical performance of the device.

[0051] In some implementations, the second epitaxial layer further includes a first resonant cavity adjustment layer and a second resonant cavity adjustment layer, the first resonant cavity adjustment layer is located between the active layer and the sacrificial layer, and the second resonant cavity adjustment layer is located on a side of the active layer away from the sacrificial layer. c Ga (1-c) N layer, the second resonant cavity adjustment layer is Al d Ga (1-d) N layers, c>0.5, d>0.5. The first resonant cavity adjustment layer and the second resonant cavity adjustment layer together with the active layer constitute a resonant cavity, and the first resonant cavity adjustment layer and the second resonant cavity adjustment layer can play a role in adjusting the cavity length of the resonant cavity.

[0052] It should be noted that the VCSEL in the above implementation is an AlGaN-based deep ultraviolet VCSEL, and the Al content in each AlGaN is greater than 0.5 to prevent each AlGaN layer from absorbing light.

[0053] In some implementations, the first DBR reflective layer includes a plurality of first reflective layers and a plurality of second reflective layers that are alternately arranged in sequence, and the first reflective layer and the second reflective layer are HfO 2 Layer and SiO 2 Layer. HfO 2 and SiO 2 They are all chemically stable materials that are not prone to chemical reactions with other substances, thus ensuring the long-term stability and reliability of the DBR structure. 2 and SiO 2 There is usually good etch selectivity between HfO, which helps to accurately remove or pattern specific layers in subsequent process steps without damaging other structural layers. 2 and SiO 2 The thin film deposition technology is relatively mature and can be prepared by a variety of methods such as sputtering and chemical vapor deposition, and the process control is relatively simple.

[0054] In some implementations, the sacrificial layer is an N-type doped AlGaN layer or an N-type doped GaN layer. Since there are more free electrons in the N-type doped AlGaN and GaN layers, these electrons can participate in the anodic oxidation reaction during the electrochemical etching process, thereby accelerating the etching process. In addition, the n-type AlGaN and GaN layers have good conductivity, which is conducive to the transfer of current and the etching reaction. At the same time, the AlGaN or GaN layer can better match other epitaxial layers, reduce lattice mismatch and stress, and ensure the crystal quality of the second epitaxial layer grown thereon.

[0055] In some implementations, a metal organic chemical vapor deposition (MOCVD) method may be used to form the first epitaxial layer, the sacrificial layer, and the second epitaxial layer on the first substrate.

[0056] Figure 2 is a schematic diagram of an epitaxial structure provided by an embodiment of the present invention, such as Figure 2 As shown, the epitaxial structure includes a first epitaxial layer 20, a sacrificial layer 30, and a second epitaxial layer 40 stacked in sequence on a first substrate 10. The first epitaxial layer 20 includes a nucleation layer 21, a buffer layer 22, and a current spreading layer 23 stacked in sequence, and the second epitaxial layer 40 includes a first resonant cavity adjustment layer 41, an active layer 42, and a second resonant cavity adjustment layer 43 stacked in sequence.

[0057] For example, the nucleation layer 221 is a 700 nm AlN layer, and the buffer layer is a 200 nm Al 0.8 Ga 0.2 N layer, current spreading layer is 500nm Al 0.6 Ga 0.4N layer, the sacrificial layer is a 20nm N-type GaN layer, and the first resonant cavity adjustment layer is a 190nm Al 0.5 Ga 0.5 N layer, the second resonant cavity adjustment layer is 65nm Al 0.5 Ga 0.5 N layer, the active layer includes 5 cycles of 2nm Al 0.55 Ga 0.45 N quantum well layer and 9nm Al 0.45 Ga 0.55 N quantum barrier layers. The first DBR reflective layer includes 15.5 pairs of HfO 2 / SiO 2 layer.

[0058] Figure 3 is a schematic diagram of the structure after executing step S110, such as Figure 3 As shown, at this time, a first epitaxial layer 20 , a sacrificial layer 30 , a second epitaxial layer 40 and a first DBR reflective layer 50 are sequentially stacked on the first substrate 10 .

[0059] Step S120, patterning the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form at least one patterned structure on the side of the first epitaxial layer away from the first substrate, the patterned structure comprising a patterned sacrificial layer, a patterned second epitaxial layer and a patterned first DBR reflective layer.

[0060] In some implementations, step S120 includes:

[0061] Step S121, forming a patterned photoresist layer on the first DBR reflective layer.

[0062] Exemplarily, a desired patterned photoresist layer may be formed on the first DBR reflective layer by coating, exposing, developing, etc. This is a conventional technique and will not be described in detail herein.

[0063] Figure 4 is a schematic diagram of the structure after executing step S121, such as Figure 4 As shown, a patterned photoresist layer 51 is formed on the first DBR reflective layer 50 at this time.

[0064] Step S122, etching away the first DBR reflective layer, the second epitaxial layer and the sacrificial layer at the opening position of the photoresist layer to transfer the pattern on the patterned photoresist to the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form a patterned first DBR reflective layer, a patterned second epitaxial layer and a patterned sacrificial layer.

[0065] like Figure 4As shown, the first DBR reflective layer, the second epitaxial layer and the sacrificial layer at the opening position of the photoresist layer, that is, the orthographic projection on the first substrate 10 is located at Figure 4 The portion of the first DBR reflective layer, the second epitaxial layer and the sacrificial layer located in the opening area a. Figure 5 is a schematic diagram of the structure after executing step S122, such as Figure 5 As shown, at this time, parts of the first DBR reflective layer, the second epitaxial layer and the sacrificial layer located in the opening region a are etched to form a patterned first DBR reflective layer 50a, a patterned second epitaxial layer 40a and a patterned sacrificial layer 30a.

[0066] In some implementations, a buffered oxide etchant (BOE) solution may be used to wet-etch the first DBR reflective layer at the opening of the photoresist layer, and an inductively coupled plasma (ICP) solution may be used to dry-etch the second epitaxial layer and the sacrificial layer at the opening of the photoresist layer.

[0067] Step S123, removing the patterned photoresist layer.

[0068] Figure 6 yes Figure 5 A top view of the structure shown in FIG. Figure 6 As shown, at this time, at least one patterned structure A is formed on the side of the first epitaxial layer 20 away from the first substrate 10, and each patterned structure A includes the following Figure 5 The patterned first DBR reflective layer 50a, the patterned second epitaxial layer 40a and the patterned sacrificial layer 30a are shown.

[0069] In some implementations, the patterned first DBR reflective layer includes a plurality of first reflective layers and a plurality of second reflective layers that are staggered, and the first reflective layers and the second reflective layers are HfO 2 Layer and SiO 2 layer.

[0070] Step S130: using an electrochemical etching method to etch away the patterned sacrificial layer in the patterned structure, so as to peel off the patterned second epitaxial layer and the patterned first DBR reflective layer as a whole from the first epitaxial layer.

[0071] In some implementations, step S130 includes:

[0072] Electrical contact material is welded to the edge of the first epitaxial layer, and the first epitaxial layer is electrically connected to the positive electrode of the power supply through the electrical contact material, and the negative electrode of the power supply is electrically connected to the cathode material; the first substrate formed with the first epitaxial layer and the patterned structure is placed in an electrolyte, and the first epitaxial layer is used as an anode and the cathode material is used as a cathode to electrochemically etch the patterned sacrificial layer in the patterned structure.

[0073] Exemplarily, when performing electrochemical etching, the working voltage provided by the power supply is 20V, the etching time is 30 minutes, and the electrolyte is nitric acid with a concentration of 1 mol / L.

[0074] In some implementations, the electrical contact material is indium and the cathode material is platinum.

[0075] Figure 7 is a schematic diagram of the structure of an electrochemical etching provided by an embodiment of the present invention, such as Figure 7 As shown, at this time, the first epitaxial layer 20 is used as an anode, and the cathode material 60 (platinum) is used as a cathode to electrochemically etch the patterned sacrificial layer in the patterned structure.

[0076] Step S140: bonding the peeled patterned first DBR reflective layer and the patterned second epitaxial layer to the second substrate, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the second substrate.

[0077] In some implementations, step S140 includes:

[0078] Step S141 : using an organic substrate to pick up the peeled patterned first DBR reflective layer and the patterned second epitaxial layer, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the organic substrate.

[0079] Exemplarily, the organic substrate may be polyimide, and the polyimide may be used to pick up the patterned first DBR reflective layer and the patterned second epitaxial layer after peeling.

[0080] Figure 8 is a schematic diagram of the structure when executing step S141, such as Figure 8 As shown, Figure 8 S1 in the figure represents the whole of the patterned first DBR reflective layer and the patterned second epitaxial layer after stripping. At this time, the organic substrate 70 strips the patterned first DBR reflective layer and the patterned second epitaxial layer (i.e. Figure 8 The S1 portion in the figure is picked up by adhesion to separate the patterned first DBR reflective layer and the patterned second epitaxial layer from the first epitaxial layer 20.

[0081] Step S142 , bonding the side of the organic substrate away from the patterned first DBR reflective layer and the patterned second epitaxial layer to a second substrate.

[0082] Fig. 9 is a schematic diagram of the structure after executing step S142, such as Fig. 9 As shown, at this time, the organic substrate 70 is bonded to the second substrate 80, and the first DBR reflective layer and the second epitaxial layer (ie, Fig. 9The S1 portion in the figure) is located on a surface of the organic substrate 70 away from the second substrate 80.

[0083] Step S150 , forming a patterned second DBR reflective layer on a side of the patterned second epitaxial layer away from the patterned first DBR reflective layer to obtain a vertical cavity surface emitting laser.

[0084] In some implementations, the patterned second DBR reflective layer includes a plurality of first reflective layers and a plurality of second reflective layers that are alternately arranged in sequence, wherein the first reflective layer and the second reflective layer are HfO 2 Layer and SiO 2 layer.

[0085] In some implementations, step S150 includes:

[0086] A second reflective layer is formed on a side of the patterned second epitaxial layer away from the patterned first DBR reflective layer; a patterned photoresist layer is formed on the second reflective layer, wherein the pattern on the patterned photoresist layer is the same as the pattern on the patterned second epitaxial layer; a wet etching process is used to remove the second reflective layer at the opening position of the patterned photoresist so as to transfer the pattern on the photoresist layer to the second epitaxial layer to form a patterned second reflective layer; and the patterned photoresist layer is removed.

[0087] Exemplarily, a desired patterned photoresist layer may be formed on the first DBR reflective layer by coating, exposing, developing, etc. This is a conventional technique and will not be described in detail herein.

[0088] In some implementations, step S150 may further include:

[0089] After forming the patterned second reflective layer, the second substrate is removed to obtain a vertical cavity surface emitting laser.

[0090] Fig.10 is a schematic diagram of the structure after executing step S150, such as Fig.10 As shown, at this time, a patterned second DBR reflective layer 90 is formed on a side of the patterned second epitaxial layer away from the patterned first DBR reflective layer.

[0091] Based on the same inventive concept, the embodiment of the present invention further provides a vertical cavity surface emitting laser, which is prepared by the preparation method described in the above embodiment. The specific structure of the vertical cavity surface emitting laser can be seen in Fig.10 .

[0092] The embodiment of the present invention also performs an optical pump test on the prepared VCSEL. Fig.11 is a schematic diagram of the relationship between the emission intensity and pump power density of a VCSEL prepared by the preparation method provided by the present invention, Fig.11In the figure, the horizontal axis represents the pump power density in MW / cm 2 , the vertical axis represents the emission intensity, Fig.11 It can be seen that the threshold pump power density of the VCSEL prepared by the present invention is 7.4 MW / cm 2 , that is, when the pump power density reaches or exceeds 7.4MW / cm 2 When Fig.12 is a schematic diagram of the emission spectrum of a VCSEL prepared by the preparation method provided by the present invention at different excitation levels, Fig.12 In the figure, the horizontal axis represents the laser wavelength in nm, and the vertical axis represents the luminous intensity. Fig.12 The corresponding lasing wavelength and luminous intensity under different pump power densities are shown. The lasing wavelength corresponding to the VCSEL prepared by the present invention is 294nm, that is, the present invention can prepare deep ultraviolet VCSEL.

[0093] The technical solution provided in the embodiments of the present invention has at least the following technical effects or advantages:

[0094] A vertical cavity surface emitting laser and a preparation method thereof provided by an embodiment of the present invention, wherein a sacrificial layer is formed during the growth of an epitaxial layer to divide the epitaxial layer into two parts for growth, and then the first DBR reflective layer, the second epitaxial layer including the active layer and the sacrificial layer are patterned to form at least one patterned structure on the side of the first epitaxial layer away from the first substrate. At this time, since the sacrificial layer is patterned, part of the sacrificial layer will be exposed, which is convenient for subsequent electrochemical etching to etch away the sacrificial layer, so as to peel off the patterned second epitaxial layer and the patterned first DBR reflective layer as a whole from the first epitaxial layer; then, the patterned first DBR reflective layer and the patterned second epitaxial layer after peeling are bonded to the second substrate, and the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the second substrate, and at this time, the first DBR reflective layer is located at the bottom of the active layer, which can be used as the bottom DBR layer. Finally, a patterned second DBR reflective layer is formed on the side of the patterned second epitaxial layer away from the patterned first DBR reflective layer as the top DBR layer, and the desired vertical cavity surface emitting laser can be prepared. The present invention adopts a sacrificial layer combined with an electrochemical etching method. Compared with a conventional laser lift-off method, the electrochemical etching method has higher precision and controllability, can reduce thermal shock and mechanical damage to the epitaxial layer, and make the surface of the second epitaxial layer after lift-off smoother. Furthermore, by precisely controlling the electrochemical etching process, it is possible to reduce cracking of each film layer in the second epitaxial layer and generation of aluminum residues, thereby reducing the scattering loss of the VCSEL, improving the reliability and stability of the device, and at the same time reducing the preparation cost of the VCSEL and improving production efficiency.

[0095] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0096] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly recited in each claim. More specifically, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0097] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims.

Claims

1. A method for preparing a vertical cavity surface emitting laser, characterized in that: The preparation method comprises: Forming a first epitaxial layer, a sacrificial layer, a second epitaxial layer and a first DBR reflective layer in sequence on a first substrate, wherein the second epitaxial layer at least includes an active layer; Performing patterning on the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form at least one patterned structure on a side of the first epitaxial layer away from the first substrate, the patterned structure comprising a patterned sacrificial layer, a patterned second epitaxial layer and a patterned first DBR reflective layer; Using an electrochemical etching method to etch away the patterned sacrificial layer in the patterned structure, so as to peel off the patterned second epitaxial layer and the patterned first DBR reflective layer as a whole from the first epitaxial layer; Bonding the peeled-off patterned first DBR reflective layer and the patterned second epitaxial layer to a second substrate, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the second substrate; A patterned second DBR reflective layer is formed on a side of the patterned second epitaxial layer away from the patterned first DBR reflective layer to obtain the vertical cavity surface emitting laser.

2. The preparation method according to claim 1, characterized in that: The patterned first DBR reflective layer and the patterned second DBR reflective layer include a plurality of first reflective layers and a plurality of second reflective layers which are alternately arranged in sequence, and the first reflective layer and the second reflective layer are respectively a HfO2 layer and a SiO2 layer.

3. The preparation method according to claim 1, characterized in that: The step of bonding the peeled-off patterned first DBR reflective layer and the patterned second epitaxial layer to a second substrate comprises: Using an organic substrate to pick up the peeled patterned first DBR reflective layer and the patterned second epitaxial layer, wherein the patterned first DBR reflective layer is located between the patterned second epitaxial layer and the organic substrate; The side of the organic substrate away from the patterned first DBR reflective layer and the patterned second epitaxial layer is bonded to the second substrate.

4. The preparation method according to claim 1, characterized in that: The electrochemical etching method is used to etch away the patterned sacrificial layer in the patterned structure, including: Welding an electrical contact material at the edge of the first epitaxial layer, and electrically connecting the first epitaxial layer to the positive electrode of the power supply through the electrical contact material, and electrically connecting the negative electrode of the power supply to the cathode material; The first substrate formed with the first epitaxial layer and the patterned structure is placed in an electrolyte, and the patterned sacrificial layer in the patterned structure is electrochemically etched using the first epitaxial layer as an anode and the cathode material as a cathode.

5. The preparation method according to claim 4, characterized in that: The electrical contact material is indium, and the cathode material is platinum.

6. The preparation method according to claim 1, characterized in that: The patterning of the first DBR reflective layer, the second epitaxial layer and the sacrificial layer comprises: forming a patterned photoresist layer on the first DBR reflective layer; Etching the first DBR reflective layer, the second epitaxial layer and the sacrificial layer at the opening position of the photoresist layer to transfer the pattern on the photoresist layer to the first DBR reflective layer, the second epitaxial layer and the sacrificial layer to form the patterned first DBR reflective layer, the patterned second epitaxial layer and the patterned sacrificial layer; The patterned photoresist layer is removed.

7. The preparation method according to claim 1, characterized in that: The sacrificial layer is an N-type doped AlGaN layer or an N-type doped GaN layer.

8. The preparation method according to claim 1, characterized in that: The first substrate and the second substrate are both sapphire substrates, the first epitaxial layer comprises a nucleation layer, a buffer layer and a current spreading layer sequentially stacked on the first substrate, and the active layer comprises a plurality of quantum well layers and a plurality of quantum barrier layers alternately arranged; The material of the nucleation layer includes AlN, and the material of the buffer layer includes Al a Ga (1-a) N, the material of the current spreading layer includes Al b Ga (1-b) N, the material of the quantum well layer includes Al k1 Ga (1-k1) N, the material of the quantum barrier layer includes Al k2 Ga (1-k2) N, a>0.5, b>0.5, k1>0.5, k2>0.

5.

9. The preparation method according to claim 8, characterized in that: The second epitaxial layer further includes a first resonant cavity adjustment layer and a second resonant cavity adjustment layer, the first resonant cavity adjustment layer is located between the active layer and the sacrificial layer, and the second resonant cavity adjustment layer is located on a side of the active layer away from the sacrificial layer; Wherein, the first resonant cavity adjustment layer is Al c Ga (1-c) N layer, the second resonant cavity adjustment layer is Al d Ga (1-d) N layers, c>0.5, d>0.

5.

10. A vertical cavity surface emitting laser, characterized in that: The preparation method is as described in any one of claims 1 to 9.

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