Vertical cavity surface emitting laser and preparation method thereof

Abstract

The invention relates to a vertical cavity surface emitting laser and a preparation method thereof. The vertical cavity surface emitting laser comprises a substrate, an epitaxial layer arranged on the substrate and a conductive part electrically connected with the epitaxial layer, the epitaxial layer comprises a bottom reflector structure, an active layer structure and a top reflector structure; the conductive part comprises a first sub-conductive part and a second sub-conductive part; the first sub-conductive part and the second sub-conductive part are electrically contacted with the bottom reflector structure and the top reflector structure respectively; wherein the second sub conductive part comprises a conductive lower part and a conductive upper part, the conductive lower part is arranged on the top reflecting mirror structure, the conductive upper part is arranged on the conductive lower part, and the oxidation resistance of the conductive upper part is better than that of the conductive lower part; and the conductive upper part at least partially covers the surface of the conductive lower part and is not in contact with the top reflecting mirror structure. The electrode material drilling phenomenon can be improved, and the device reliability is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of semiconductor lasers, and particularly to vertical cavity surface emitting lasers and their manufacturing methods. Background Art

[0002] A vertical cavity surface emitting laser (VCSEL) is a new type of semiconductor laser, which is characterized by small size, low threshold current, easy two-dimensional integration, etc., and is widely used in fields such as optical communication and optical interconnection. However, the design of the electrode is one of the key factors affecting the performance of VCSELs. Traditional electrode designs usually adopt a multi-layer metal structure, and the topmost gold electrode is widely used due to its good electrical conductivity and stability.

[0003] In the existing electrode designs, in order to ensure good conformality and electrical conductivity of the electrode, electrode alloys are usually stacked in a way of layer-by-layer wrapping, and the outermost layer of metal usually uses a metal with excellent oxidation resistance, corrosion resistance and bonding ability (such as gold). However, since the preparation of the electrode usually adopts the negative photoresist lift-off process, the appearance morphology of the electrode usually presents a trapezoid, and its edge is not very smooth, and there will be a tailing phenomenon, which will cause the outermost layer of metal to possibly directly contact the heavily doped ohmic contact layer. During the high-temperature operation of the device, the outermost layer of metal is likely to diffuse into the semiconductor material (such as III-V compounds such as GaAs), that is, the gold under-drilling phenomenon. Especially in the heavily doped region, because the doping concentration is high, it will accelerate the diffusion. The diffusion of the outermost layer of metal atoms into the semiconductor will form deep-level defects, and these defects will become non-radiative recombination centers, affecting the carrier lifetime and the light-emitting efficiency of the device. Secondly, since the edge of the outermost layer of metal directly contacts the heavily doped ohmic contact layer, it will cause a work function mismatch between the semiconductor material at the contact part and the outermost layer of metal, and an alloying reaction may occur at high temperature, resulting in interface instability, and even forming voids, damaging the device structure. In short, this metal under-drilling phenomenon will affect the light-emitting efficiency and service life of the device. Therefore, how to avoid the outermost layer of metal under-drilling phenomenon in the electrode and improve the performance and reliability of the electrode is an important problem faced by the current electrode design technology.

[0004] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main object of the present invention is to provide a vertical cavity surface emitting laser and its manufacturing method, aiming to solve the above technical problems in the prior art.

[0006] Based on this, it is necessary to provide a vertical cavity surface emitting laser and its manufacturing method for the above technical problems.

[0007] In a first aspect, the present application provides a vertical cavity surface emitting laser, comprising a substrate, an epitaxial layer disposed on the substrate, and a conductive portion electrically connected to the epitaxial layer; the epitaxial layer includes a bottom mirror structure, an active layer structure, and a top mirror structure; the conductive portion includes a first sub-conductive portion and a second sub-conductive portion; the first sub-conductive portion and the second sub-conductive portion are in electrical contact with the bottom mirror structure and the top mirror structure respectively; Wherein, the second sub-conductive portion includes a lower conductive part and an upper conductive part, the lower conductive part is disposed on the top mirror structure, the upper conductive part is disposed on the lower conductive part, and the oxidation resistance of the upper conductive part is better than that of the lower conductive part; At least a part of the upper conductive part covers the surface of the lower conductive part and does not contact the top mirror structure.

[0008] In one embodiment, the lower conductive part includes a first surface and a second surface disposed opposite to each other, and a side surface connecting the first surface and the second surface, and the first surface is in contact with the top mirror structure; The upper conductive part is disposed on the second surface, or The upper conductive part is disposed on the second surface and a part of the side surface.

[0009] In one embodiment, when the upper conductive part is disposed on the second surface, the projection of the upper conductive part on the lower conductive part is located within the lower conductive part.

[0010] In one embodiment, the lower conductive part includes a metal layer for forming an ohmic contact with the top mirror structure; and / or A metal layer for work function matching; and / or A metal layer for improving adhesion performance; and / or A metal layer for preventing the diffusion of the upper conductive part.

[0011] In one embodiment, the metal layer is selected from at least one of titanium, platinum, chromium, and nickel.

[0012] In one embodiment, when the upper conductive part is disposed on the second surface and a part of the side surface of the lower conductive part, the upper conductive part disposed on the side surface is spaced apart from the top mirror structure by a preset distance.

[0013] In one embodiment, the material of the upper conductive part is gold.

[0014] In one embodiment, the vertical cavity surface emitting laser further includes: A conductive passivation layer disposed on the surface of the lower conductive part not covered by the upper conductive part.

[0015] In one embodiment, the conductive passivation layer is selected from any one of silicon oxide, silicon nitride, or aluminum oxide.

[0016] Second, the present application also provides a method for manufacturing a vertical cavity surface emitting laser for manufacturing the aforementioned vertical cavity surface emitting laser. The method includes performing an epitaxial layer growth step and a conductive part manufacturing step on a substrate; wherein, the conductive part manufacturing step includes: Sequentially fabricating a lower conductive part and an upper conductive part on the epitaxial layer; wherein, at least a part of the upper conductive part covers the surface of the lower conductive part and does not contact the top mirror structure.

[0017] The present invention has at least the following beneficial effects: For the vertical cavity surface emitting laser provided by the present invention, since the outer upper conductive part with better antioxidant performance is separated from the top mirror structure, the problem that metal atoms in the upper conductive part diffuse into the semiconductor material of the top mirror structure is avoided, the probability of non-radiative recombination centers that may be generated by deep level defects is reduced, and the carrier lifetime and the light emitting efficiency of the device are improved. In addition, since the edge of the outermost upper conductive part does not directly contact the top mirror structure, it will not cause the work function mismatch between the semiconductor material at the contact part and the upper conductive part, which may lead to an alloying reaction at high temperature, resulting in interface instability or even the formation of voids. The light emitting efficiency and service life of the device are effectively improved.

[0018] Third, the present application provides a VCSEL chip including at least one laser array; the laser array includes a plurality of vertical cavity surface emitting lasers as described above; the laser array is a regularly arranged array, or a randomly arranged array, or an array having a plurality of addressable sub-arrays.

[0019] Fourth, the present application provides a light source for a lidar system, including at least one vertical cavity surface emitting laser as described above or at least one VCSEL chip as described above.

[0020] Fifth, the present application provides a lidar system, including a transmitting component and a receiving component, and the transmitting component uses the light source for the lidar system as described above. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a conductive part in an embodiment of the present application; Figures 2a - 2c is Figure 1 a partial enlarged schematic diagram of the conductive part in Figure 3Schematic structural diagram of a vertical cavity surface emitting laser in an embodiment of the present application; Figure 4 Flowchart of a method for manufacturing a vertical cavity surface emitting laser in an embodiment of the present application.

[0022] The implementation, functional features, and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0023] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] It can be understood that the terms "first", "second", etc. used in the present application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present application, the first client may be referred to as the second client, and similarly, the second client may be referred to as the first client.

[0025] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. The meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. The meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0026] As described in the background art, in the existing electrode metal design, in order to ensure good coating and conductivity of the electrode metal, the electrode alloy is usually stacked in a layer-by-layer wrapping manner, and the outermost layer of metal usually uses a metal with excellent oxidation resistance, corrosion resistance and bonding ability (such as gold). However, since the negative photoresist lift-off process is usually used in the preparation of the electrode metal, the appearance of the electrode metal usually presents a trapezoid, and its edge is not very smooth, and there will be a trailing phenomenon, which will cause the metal to possibly come into direct contact with the heavily doped ohmic contact layer. During the high-temperature operation of the device, the metal is likely to diffuse into the semiconductor material (such as III-V compounds such as GaAs) (i.e., the metal under-drilling phenomenon), especially in the heavily doped region, because the high doping concentration will accelerate the diffusion. The diffusion of metal atoms into the semiconductor will form deep-level defects, which will become non-radiative recombination centers, affecting the carrier lifetime and the light-emitting efficiency of the device. Secondly, since the edge of the outermost layer of metal is in direct contact with the heavily doped ohmic contact layer, it will cause a work function mismatch between the semiconductor material in the contact part and the outermost layer of metal. An alloying reaction may occur at high temperature, resulting in interface instability and even the formation of voids, damaging the device structure. In short, this metal under-drilling phenomenon will affect the light-emitting efficiency and service life of the device. Therefore, how to avoid the metal under-drilling phenomenon of the outer layer of metal in the electrode metal and improve the performance and reliability of the electrode is an important problem faced by the current electrode design technology.

[0027] Based on this, the present application provides a vertical cavity surface emitting laser, aiming to solve the aforementioned metal under-drilling phenomenon. Specifically, referring to Figures 1 - 3 , the vertical cavity surface emitting laser of the present application includes a substrate 10 and an epitaxial layer (not shown in the figure) provided on the substrate 10 and a conductive part (not shown in the figure) electrically connected to the epitaxial layer; the epitaxial layer includes a bottom mirror structure 110, an active layer structure 120 and a top mirror structure 130; the conductive part includes a first sub-conductive part 170 and a second sub-conductive part (not shown in the figure); the first sub-conductive part 170 and the second sub-conductive part are respectively in electrical contact with the bottom mirror structure 110 and the top mirror structure 130; Wherein, the second sub-conductive part includes a conductive lower part 142 and a conductive upper part 144, the conductive lower part is provided on the top mirror structure 130, the conductive upper part 144 is provided on the conductive lower part 142, and the oxidation resistance of the conductive upper part 144 is better than that of the conductive lower part 142; The conductive upper part 144 at least partially covers the surface of the conductive lower part 142 and does not contact the top mirror structure 130.

[0028] Figure 1In this case, the capping layer is part of the top mirror structure 130, mainly a heavily doped layer, which is used to form an ohmic contact with the conductive part. In this specific embodiment, the lower conductive part 142 and the upper conductive part 144 of the second sub-conductive part are fabricated by a negative photoresist lift-off process; among them, the lower conductive part 142 is formed prior to the upper conductive part 144, and the upper conductive part 144 is then formed on the lower conductive part 142. Moreover, the projected area of the formed lower conductive part 142 on the capping layer is larger than the projected area of the upper conductive part 144. Correspondingly, the projection of the upper conductive part 144 on the lower conductive part 142 is located within the lower conductive part 142, such that the finally formed upper conductive part 144 does not directly contact the top mirror structure 130, but at least partially covers the surface of the lower conductive part 142.

[0029] In one embodiment, reference may continue to be made to Figures 1 - 3 . The lower conductive part 142 may include a first surface (not shown in the figure) and a second surface (not shown in the figure) arranged oppositely, and a side surface (not shown in the figure) connecting the first surface and the second surface. The first surface contacts the top mirror structure 130; specifically, it can be understood that the lower surface of the lower conductive part 142 contacts the surface of the capping layer. The upper conductive part 144 may be disposed on the second surface, that is, the upper surface of the lower conductive part 142. Among them, when the upper conductive part 144 is disposed on the second surface, its overall cross-sectional area is not greater than the cross-sectional area of the lower conductive part 142, that is, the projection of the upper conductive part 144 on the lower conductive part 142 is located within the lower conductive part 142 (such as Figure 2b 1442 in); further, at this time, the surface area of the surface where the upper conductive part 144 contacts the lower conductive part 142 may, for example, take values between 0.5 μm 2 -0.9 μm 2 , including the endpoints, and the surface area of the second surface of the lower conductive part 142 may, for example, take values between 1 μm 2 -1.5 μm 2 , including the endpoints; exemplarily, the surface area of the surface where the upper conductive part 144 contacts the lower conductive part 142 may, for example, be 0.5 μm 2 , and the surface area of the second surface of the lower conductive part 142 may, for example, be 1 μm 2 ; it can be understood that those skilled in the art can make selections and adjustments according to this basic logic, and the present application does not make further limitations in this regard.

[0030] In another embodiment, the upper conductive part 144 may be disposed on both the second surface and a part of the side surface of the lower conductive part 142 (such as Figure 2c 1442 in). In this embodiment, the upper conductive part 144 disposed on the side surface is spaced from the top mirror structure 130 by a preset distance. By this preset distance, the top mirror structure 130 is separated, thereby avoiding the phenomenon of metal atom downward drilling.

[0031] Further, considering that when the conductive upper part 144 is provided on a partial side surface of the conductive lower part 142, a part of the conductive lower part 142 is exposed to the environment, some oxide films will be generated, increasing the resistance, and at the same time, the reliability may also be affected by the environment. Therefore, as Figure 2b and 2c shown, the present application also provides a conductive passivation layer 1444 on the part not covered by the conductive upper part 144, and this layer is mainly used to cooperate with the conductive upper part 144 to protect the underlying conductive lower part 142. In fact, if the conductive passivation layer 1444 is not added here, it will also increase the difficulty of subsequent deposition processes because there are steps ( Figure 2b ) or gaps ( Figure 2c ). Further, the conductive passivation layer 1444 in this specific embodiment may be a dielectric material, such as silicon oxide, silicon nitride or aluminum oxide, and its thickness is coordinated with the thickness of the conductive upper part 144 to achieve a regular outer composite conductive structure.

[0032] In one embodiment, reference may be made to Figures 2a - 2c . The conductive lower part 142 may include a metal layer for making an ohmic contact with the top mirror structure 130; and / or a metal layer for work function matching; and / or a metal layer for improving the adhesion property; and / or a metal layer for preventing the diffusion of the conductive upper part. Specifically, Figures 2a - 2c the metal layer for making an ohmic contact and for improving the adhesion property in may be 1422, the metal layer for work function matching may be 1424, and the metal layer for preventing the diffusion of the conductive upper part 144 may be 1426, or it may also be stacked continuously in units of this (1422 - 1426), or only several single layers may be stacked on 1426; it can be understood that the stacking logarithm of the metal layers here can be selected and adjusted with reference to the prior art, and the present application will not elaborate further here.

[0033] Further, the metal layers 1422, 1424, 1426 may be selected from at least one of titanium, platinum, chromium, and nickel. The present application does not make specific restrictions on this, and those skilled in the art can freely adjust according to the respective metal characteristics of titanium, platinum, chromium, and nickel. For example, they may be stacked in the stacking order of chromium, titanium, nickel, platinum, nickel, where chromium is used as the ohmic contact and work function matching layer, titanium has good adhesion and can be used as the adhesion layer, and the stacking of platinum and nickel can achieve a stronger blocking effect. In other embodiments, a titanium layer or a stack of titanium and platinum may also be used as the diffusion barrier layer.

[0034] In other embodiments, other pure metals or alloys with appropriate thicknesses can also be added. For example, the alloy can include a copper-aluminum alloy, which can be disposed between chromium and titanium. Adding a copper-aluminum alloy between chromium and titanium as a flexible extension layer not only retains the flexibility required for the flexible extension layer but also reduces the thermal expansion of the flexible extension layer, avoiding the occurrence of metal intersolubility at the electrode edges and improving the stability and durability of the electrode. Further, the proportion of copper in the copper-aluminum alloy can be between two percent and five percent, such as two percent, three percent, four percent, five percent, and so on.

[0035] In one of the embodiments, the material of the conductive upper part 144 is selected as gold. Gold is commonly used in the electrode process of chips due to its stable, corrosion-resistant, oxidation-resistant, easy bonding, and easy extension characteristics. It is usually used in the outermost layer in the metal manufacturing process for protection, and gold is also mainly used in the pad manufacturing process. For example, Figure 3 the 150 in [reference] is the pad of the entire chip, and it can also be made of gold.

[0036] In this specific embodiment, reference can be made to Figure 3 , the bottom mirror structure 110 and the top mirror structure 130 define the resonant cavity structure of the vertical cavity surface emitting laser of the present application. That is, the region between the bottom mirror structure 110 and the top mirror structure 130 is the resonant cavity. The resonant cavity is used to generate a standing wave, which is a wave formed by the superposition of two coherent waves propagating in opposite directions on the same straight line. Specifically, when the phases of the two waves are the same, their amplitudes are added to form a wave crest (i.e., a peak). When the phases of the two waves are opposite, their amplitudes are subtracted to form a node (i.e., a trough). Therefore, the positions of the wave crests and wave troughs of the standing wave are fixed.

[0037] In one of the embodiments, the bottom mirror structure 110 can include a periodically stacked DBR structure, that is, it includes multiple mirrors with an optical thickness of a quarter of the lasing wavelength, and the multiple mirrors are alternately arranged according to high and low refractive indices. The top mirror structure 130 also includes a periodically stacked DBR structure, that is, multiple mirrors with an optical thickness of a quarter of the lasing wavelength, and the multiple mirrors are alternately arranged according to high and low refractive indices. It can be understood that the components, stacking periods, etc. of the DBR structure of the bottom mirror structure 110 and the DBR structure of the top mirror structure 130 can be the same or different, and this embodiment does not make any limitations. Among them, the materials of the top mirror structure 130 and the bottom mirror structure 110 can be dielectric materials with electrical insulation properties, such as silicon nitride, silicon oxide, aluminum oxide, or titanium oxide, etc. The materials of the top mirror structure 130 and the bottom mirror structure 110 can also be semiconductor materials, such as GaAs and AlGaAs.

[0038] Among them, the material of the substrate 10 includes but is not limited to GaAs, InP, Si, etc. The bottom mirror structure 110 and the top mirror structure 130 may include film layers with periodically varying refractive indices to achieve efficient reflection or transmission of light within a specific wavelength range. The film layers with periodically varying refractive indices can be composed of semiconductor materials, dielectric materials, metal-dielectric hybrid materials, etc. For example, the bottom mirror structure 110 can be an N-type semiconductor layer, and the top mirror structure 130 can be a P-type semiconductor layer. Another example is that the bottom mirror structure 110 can be a P-type semiconductor layer, and the top mirror structure 130 can be an N-type semiconductor layer. Optionally, the materials of the N-type semiconductor layer and the P-type semiconductor layer can be but are not limited to GaAs, AlGaAs, etc., which are not limited here as long as they can define the resonant cavity and fall within the protection scope of this embodiment. Specifically, the resonant cavity structure may further include a photoelectric confinement layer 132, and the photoelectric confinement layer 132 is formed in the top mirror structure 130.

[0039] The active layer structure 120 can include 1 active region, or 2 active regions, or 3 active regions, or 4 active regions. One or more multiple quantum well structures can be disposed in each active region. The multiple quantum well structure is used to generate stimulated emission photons, and the emitted photons are continuously reflected in the resonant cavity defined by the bottom mirror structure 110 and the top mirror structure 130 and continuously enhanced during the reflection process, and finally emit laser light at a specific wavelength and with sufficient energy.

[0040] The multiple quantum well structure is the place where laser gain amplification occurs. The central position of the multiple quantum well structure can be aligned with the position where the light field is the strongest to achieve a greater amplification effect. Further, in the case of including multiple multiple quantum well structures, the confinement factors of the multiple quantum well structures in the same light field are within the same preset range, that is, the confinement factors of each multiple quantum well structure are maintained at the same level, so that the contribution of each multiple quantum well structure to light emission is similar. It can be understood that similar light emission contributions mean that the current injection in each multiple quantum well structure is more uniform, which helps to reduce the threshold current of the device, thereby reducing the power consumption of the device and prolonging its service life. Moreover, when the contribution of each multiple quantum well structure to light emission is similar, the distribution of carriers in each multiple quantum well structure will be more uniform, which helps to reduce the recombination loss of carriers, thereby improving the overall light emission efficiency of the device.

[0041] Generally, the number of the optical confinement layers 132 is not greater than that of the active layer structures 120, and for example, it can be 2, 3, 4, etc. The optical confinement layers 132 are used to define the light-emitting region of the vertical cavity surface emitting laser. Specifically, the optical confinement layers 132 are located on the side of the corresponding active layer structures 120 away from the substrate 10 to restrict the flow of current, so that the current only flows within the light-emitting region defined by the optical confinement layers 132, thereby reducing unnecessary energy consumption, further reducing the threshold current, and increasing the current density. Moreover, the optical confinement layers 132 can also confine the optical field within the light-emitting region defined by the optical confinement layers 132, reducing light scattering and diffraction, thereby optimizing the divergence angle of the device and improving the beam quality. Generally, the optical confinement layers 132 are arranged at the position where the optical field intensity is the lowest, that is, at the trough of the standing wave, so that it has a small confinement factor, which helps to reduce the divergence angle of the device.

[0042] The optical confinement layer 132 can include any one of an air column type optical confinement layer, an oxidation confinement type optical confinement layer, an ion implantation type optical confinement layer, and a tunnel junction type optical confinement layer. Among them, the air column type optical confinement layer realizes the confinement of current and light through air columns. The air columns are hollow structures formed by dry etching technology, and their refractive index is lower than that of the surrounding semiconductor materials, so as to effectively confine the light within the central region. The ion implantation type optical confinement layer changes its electrical properties by implanting ions into the semiconductor material to form a high-resistance region, and the high-resistance region can restrict the flow of current, thereby indirectly restricting the light generation region.

[0043] In one embodiment, the oxidation confinement type optical confinement layer includes an unoxidized region made of AlGaAs material with a high Al component and an oxidized region made of alumina material. The oxidized region is arranged outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection. Among them, the semiconductor layer of the unoxidized region in the optical confinement layer 132 can be understood as an opening, and the opening is used to define the light-emitting area of the vertical cavity surface emitting laser. When the current enters, the current can only flow to the active layer structure 120 through the opening in the optical confinement layer 132, thereby realizing the confinement of the current injection path and the optical mode field. Further, through a selective oxidation process, the AlGaAs layer with a high aluminum component can be converted into alumina to form the peripheral unoxidized region.

[0044] In one embodiment, the tunnel junction type optical confinement layer includes at least one highly doped N-type structure layer and at least one highly doped P-type structure layer. Specifically, a potential barrier is formed between the highly doped N-type structure layer and the highly doped P-type structure layer, and electrons are allowed to pass through the potential barrier through the tunnel effect, thereby realizing the lateral confinement of current. In one embodiment, the materials of the N-type structure layer and the P-type structure layer are selected as Al x Ga 1-xAs, the doping concentration of the N-type structure layer and the P-type structure layer is greater than 1e 18 cm -3 , where 0 ≤ x ≤ 1.

[0045] In a second aspect, as Figure 4 shown, the present application also provides a method for manufacturing a vertical cavity surface emitting laser for manufacturing the vertical cavity surface emitting laser described in any of the foregoing embodiments. The method includes performing an epitaxial layer growth step and a conductive part manufacturing step on a substrate; wherein, the conductive part manufacturing step includes: successively manufacturing a lower conductor and an upper conductor on the epitaxial layer; wherein, at least a part of the upper conductor covers the surface of the lower conductor and does not contact the top mirror structure.

[0046] Specifically, as Figure 3 shown, the complete manufacturing method in this specific embodiment may generally include steps such as epitaxial growth, MESA trench etching, wet oxidation, deep trench etching, deep trench ion implantation, and conductive part manufacturing; wherein, epitaxial growth, MESA trench etching, wet oxidation, and deep trench etching and deep trench ion implantation can all be understood with reference to the existing processes of vertical cavity surface emitting lasers, and there is no special improvement in these steps in this embodiment. The key improvement of the present application lies in the conductive part manufacturing step.

[0047] Furthermore, the manufacturing of the conductive part here mainly refers to the manufacturing of the conductive part on the side close to the top mirror structure 130, more specifically, the manufacturing of the upper conductor 1442 and the lower conductor 142. Exemplarily, taking Figure 2b the lower conductor 142 and the upper conductor 1442 shown in as an example for manufacturing description, the lower conductor 142 (including 1422, 1424, 1426, etc.) can be manufactured first by a negative resist lift-off process, and then a conductive passivation layer 1444 is manufactured on the lower conductor 142. Subsequently, the conductive passivation layer 1444 at the position of the upper conductor 144 is etched away, leaving a corresponding groove, and then the upper conductor 1442 is evaporated or sputtered in the groove, thereby completing the manufacturing of the entire conductive part. This manufacturing method omits the manufacturing of some intermediate passivation layers, also called insulating layers. Similarly, the manufacturing timing of the insulating layer in this manufacturing method can be understood with reference to the existing processes of vertical cavity surface emitting lasers, and the present application will not elaborate further on this.

[0048] It should be understood that although Figure 3The steps in the flowchart are shown in sequence according to the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise clearly stated in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 3 At least a part of the steps in

[0049] In summary, for the vertical cavity surface emitting laser and its manufacturing method provided in this application, since the outer conductive upper part with better antioxidant performance is separated from the top mirror structure, the problem that metal atoms in the conductive upper part diffuse into the semiconductor material of the top mirror structure is avoided, the probability of non-radiative recombination centers that may be generated by deep-level defects is reduced, and the carrier lifetime and the light emitting efficiency of the device are improved. In addition, since the edge of the outermost conductive upper part does not directly contact the top mirror structure, it will not cause the work function mismatch between the semiconductor material in the contact part and the conductive upper part, thus possibly causing an alloying reaction at high temperature, resulting in interface instability and even the formation of voids. The light emitting efficiency and service life of the device are effectively improved.

[0050] The embodiment of this application also provides a VCSEL chip, and the VCSEL chip includes at least one laser array. The laser array includes a plurality of vertical cavity surface emitting lasers as described above. The laser array is a regularly arranged array, or a randomly arranged array, or an array with multiple addressable sub-arrays. Based on the foregoing vertical cavity surface emitting lasers, the VCSEL chip in this embodiment has a good performance in terms of reliability.

[0051] The embodiment of this application also provides a light source for a lidar system, including at least one vertical cavity surface emitting laser as described above or at least one VCSEL chip as described above.

[0052] The embodiment of this application also provides a lidar system, including a transmitting component and a receiving component, and the transmitting component uses the light source for a lidar system as described above.

[0053] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0054] The above-described embodiments merely represent several implementation manners of the embodiments of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the embodiments of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the embodiments of the present application. Therefore, the protection scope of the patent of the embodiments of the present application shall be subject to the appended claims.

Claims

1. A vertical cavity surface emitting laser, characterized in that, It includes a substrate, an epitaxial layer provided on the substrate, and a conductive part electrically connected to the epitaxial layer; the epitaxial layer includes a bottom mirror structure, an active layer structure, and a top mirror structure; the conductive part includes a first sub-conductive part and a second sub-conductive part; the first sub-conductive part and the second sub-conductive part are in electrical contact with the bottom mirror structure and the top mirror structure respectively; Wherein, the second sub-conductive part includes a lower conductive part and an upper conductive part, the lower conductive part is provided on the top mirror structure, the upper conductive part is provided on the lower conductive part, and the oxidation resistance of the upper conductive part is better than that of the lower conductive part; At least part of the upper conductive part covers the surface of the lower conductive part and does not contact the top mirror structure.

2. The vertical cavity surface emitting laser according to claim 1, characterized in that, The lower conductive part includes a first surface and a second surface arranged oppositely, and a side surface connecting the first surface and the second surface, and the first surface contacts the top mirror structure; The upper conductive part is provided on the second surface, or The upper conductive part is provided on the second surface and part of the side surface.

3. The vertical cavity surface emitting laser according to claim 2, wherein When the upper conductive part is provided on the second surface, the projection of the upper conductive part on the lower conductive part is located within the lower conductive part.

4. The vertical cavity surface emitting laser according to claim 2, characterized in that, The lower conductive part includes a metal layer for forming an ohmic contact with the top mirror structure; and / or A metal layer for work function matching; and / or A metal layer for improving adhesion performance; and / or A metal layer for preventing the diffusion of the upper conductive part.

5. The vertical cavity surface emitting laser according to claim 4, characterized in that, The metal layer is selected from at least one of titanium, platinum, chromium, and nickel.

6. The vertical cavity surface emitting laser according to claim 2, wherein When the upper conductive part is provided on the second surface and part of the side surface of the lower conductive part, the upper conductive part provided on the side surface is spaced from the top mirror structure by a preset distance.

7. The vertical cavity surface emitting laser according to claim 1, characterized in that, The material of the upper conductive part is gold.

8. The vertical cavity surface emitting laser according to any one of claims 1-7, characterized in that, It further includes: A conductive passivation layer provided on the surface of the lower conductive part not covered by the upper conductive part.

9. The vertical cavity surface emitting laser according to claim 8, wherein The conductive passivation layer is selected from any one of silicon oxide, silicon nitride, or aluminum oxide.

10. A method for fabricating a vertical cavity surface emitting laser for fabricating the vertical cavity surface emitting laser according to any one of claims 1-9, characterized in that, The method includes performing an epitaxial layer growth step and a conductive part manufacturing step on a substrate; wherein, the conductive part manufacturing step includes: Sequentially manufacturing a lower conductive part and an upper conductive part on the epitaxial layer; wherein, at least part of the upper conductive part covers the surface of the lower conductive part and does not contact the top mirror structure.

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