Multi-junction VCSEL device, VCSEL chip, laser radar system and light source thereof

Abstract

The embodiment of the utility model relates to a multi-junction VCSEL device, a VCSEL chip, a laser radar system and a light source of the laser radar system. The multi-junction VCSEL device comprises a substrate; the bottom reflecting mirror structure and the top reflecting mirror structure are stacked on the substrate; a plurality of active regions and a plurality of photoelectric limiting layers, each photoelectric limiting layer is located at one side, far away from the substrate, of the corresponding active region, and the photoelectric limiting layers are used for limiting a light emitting region of the multi-junction VCSEL device; the extension cavity is formed in the side, close to the active area, of the bottom reflector structure or the top reflector structure, and the light field intensity in the extension cavity is larger than the light field intensity of the adjacent active area; the at least one light field regulation and control layer is arranged close to the photoelectric limiting layer or arranged on one side, close to the active area, of the extension cavity, the light field regulation and control layer is configured to divide a light field between the bottom reflector structure and the top reflector structure into multiple sections, and the intensity of each section of the light field is different.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and particularly to a multi-junction VCSEL device, a VCSEL chip, a lidar system and a light source thereof. Background Art

[0002] With the continuous development of semiconductor technology, due to its easy integration characteristics, vertical-cavity surface-emitting lasers (VCSELs) are widely used in the fields of optical communication, optical interconnection and optical sensing. The main application scenario in the field of optical sensing is lidar. High-power VCSEL devices are the main technical direction for future lidar applications. High-power VCSELs usually require cascading multiple active layers to achieve. However, the confinement factor of the oxide layer in the current multi-junction VCSEL devices with cascaded multiple active layers is relatively high, resulting in a large divergence angle of the multi-junction VCSEL device, which limits the usage scenarios of the multi-junction VCSEL device. Summary of the Utility Model

[0003] Based on this, it is necessary to provide a multi-junction VCSEL device, a VCSEL chip, a lidar system and a light source thereof for the problem of the large divergence angle of the multi-junction VCSEL device in the prior art.

[0004] In a first aspect, the present application provides a multi-junction VCSEL device, including:

[0005] A substrate;

[0006] A bottom mirror structure and a top mirror structure stacked on the substrate;

[0007] Multiple active regions and multiple optical confinement layers, each of the optical confinement layers is located on the side of the corresponding active region away from the substrate, and the optical confinement layer is used to define the light-emitting region of the multi-junction VCSEL device;

[0008] An extended cavity, disposed on the side of the bottom mirror structure or the top mirror structure close to the active region, and the light field intensity in the extended cavity is greater than the light field intensity of the adjacent active region;

[0009] At least one light field regulation layer, disposed adjacent to the optical confinement layer or on the side of the extended cavity close to the active region, and the light field regulation layer is configured to divide the light field between the bottom mirror structure and the top mirror structure into multiple segments, and the intensity of each segment of the light field is different.

[0010] In one embodiment, the extended cavity includes an antireflection layer and a light storage layer. The antireflection layer is disposed adjacent to the light storage layer. The antireflection layer is used to increase the light field intensity of the light storage layer, and the light storage layer is used to store light field energy.

[0011] In one embodiment, the thickness of the light storage layer is an odd multiple of half of the lasing wavelength.

[0012] In one embodiment, the light field modulation layer includes a photonic crystal structure, a single-layer structure, or a periodically stacked DBR structure.

[0013] In one embodiment, when the light field modulation layer includes a periodically stacked DBR structure, the periodically stacked DBR structure is composed of Al x Ga （1-x） As / Al y Ga （1-y） As alternately, and the number of stacking periods is between 3 pairs and 10 pairs, 0≤x<y≤1.

[0014] In one embodiment, at least one of the side of the optoelectronic confinement layer close to the substrate and the side away from the substrate is provided with the light field modulation layer.

[0015] In one embodiment, when the light field modulation layer is located on the side of the optoelectronic confinement layer away from the substrate, a tunnel junction layer is further provided between the light field modulation layer and the optoelectronic confinement layer.

[0016] In one embodiment, when the light field modulation layers on both sides of the optoelectronic confinement layer are both periodically stacked DBR structures, the number of stacking periods of the DBR structures in the light field modulation layers on both sides is different.

[0017] In one embodiment, the optoelectronic confinement layer includes any one of an air-column type optoelectronic confinement layer, an oxidation confinement type optoelectronic confinement layer, an ion implantation type optoelectronic confinement layer, and a tunnel junction type optoelectronic confinement layer.

[0018] In one embodiment, the oxidation confinement type optoelectronic 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 disposed outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection.

[0019] In one embodiment, the tunnel junction type optoelectronic confinement layer includes at least one high-doped N-type structure layer and at least one high-doped P-type structure layer.

[0020] In one embodiment, the materials of the N-type structure layer and the P-type structure layer are selected as Al x Ga1-x As, 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.

[0021] In one embodiment, at least one multi-quantum well structure is provided in each active region, and there are multiple multi-quantum well structures between the bottom mirror structure and the nearest optical field control layer.

[0022] In one embodiment, there are three multi-quantum well structures between the bottom mirror structure and the nearest optical field control layer.

[0023] In one embodiment, the active regions are connected by a tunnel junction layer.

[0024] In one embodiment, the multi-junction VCSEL device includes three active regions and three optical confinement layers; the three active regions include a first active region, a second active region, and a third active region arranged in sequence along the direction away from the substrate, and the two optical confinement layers include a first optical confinement layer, a second optical confinement layer, and a third optical confinement layer;

[0025] The first optical confinement layer is located between the first active region and the second active region, the second optical confinement layer is located between the second active region and the third active region, and the third optical confinement layer is located on the side of the third active region close to the top mirror structure.

[0026] In one embodiment, the first active region includes three multi-quantum well structures, the second active region includes two multi-quantum wells, and the third active region includes two multi-quantum well structures; and adjacent multi-quantum well structures in each active region are connected by a tunnel junction layer.

[0027] In a second aspect, the present application provides a VCSEL chip, and the VCSEL chip includes a positive electrode, a negative electrode, and the multi-junction VCSEL device as described above;

[0028] Wherein, the positive electrode and the negative electrode are respectively electrically connected to the bottom mirror structure and the top mirror structure of the multi-junction VCSEL device; or

[0029] The positive electrode and the negative electrode are respectively electrically connected to the top mirror structure and the bottom mirror structure of the multi-junction VCSEL device;

[0030] The positive electrode and the negative electrode are located on opposite sides of the light-emitting side of the VCSEL chip.

[0031] In a third aspect, the present application provides a VCSEL chip, including at least one laser array; the laser array includes a plurality of multi-junction VCSEL devices 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.

[0032] In a fourth aspect, the present application provides a light source for a lidar system, including at least one multi-junction VCSEL device as described above or at least one VCSEL chip as described above.

[0033] In a fifth aspect, the present application provides a lidar, including a transmitting component and a receiving component, and the transmitting component uses the light source for the lidar system as described above.

[0034] For the above multi-junction VCSEL device, VCSEL chip, lidar system and its light source, by inserting at least one optical field regulation layer into the multi-junction VCSEL device, the optical field between the bottom mirror structure and the top mirror structure can be divided into multiple segments. Due to the segmenting effect of the optical field regulation layer on the optical field, the optical field intensity at the optical field regulation layer is also weak, so it can also limit the optical field intensity of the optical confinement layer adjacent to the optical field regulation layer. Based on the positive correlation between the confinement factor of the film layer and the electric field intensity and optical field intensity at its location, the above setting method effectively reduces the confinement factor of the optical confinement layer, thereby achieving the suppression of high-order modes and achieving the effect of a low divergence angle. Moreover, by increasing the extended cavity to increase the optical field intensity inside the multi-junction VCSEL device, the refractive index difference between the inside and outside of the light-emitting hole of the multi-junction VCSEL device can be reduced, thereby suppressing high-order modes and further reducing the divergence angle. Therefore, the present application provides a multi-junction VCSEL device with a smaller confinement factor of the optical confinement layer and a larger confinement factor of the active region, thereby improving the performance of the multi-junction VCSEL device in terms of divergence angle and threshold current. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is one of the schematic structural diagrams of a multi-junction VCSEL device in an embodiment;

[0037] Figure 2 It is the second of the schematic structural diagrams of a multi-junction VCSEL device in an embodiment;

[0038] Figure 3 The third structural schematic diagram of a multi-junction VCSEL device according to an embodiment;

[0039] Figure 4 The refractive index and optical field intensity diagrams of a multi-junction VCSEL device according to an embodiment.

[0040] Element number description:

[0041] Substrate: 100; Bottom mirror structure: 200; Top mirror structure: 300; Active region: 400; Multi-quantum well structure: 401; First active region: 410; Second active region: 420; Third active region: 430; Optical confinement layer: 500; First optical confinement layer: 510; Second optical confinement layer: 520; Third optical confinement layer: 530; Optical field regulation layer: 600; First optical field regulation layer: 610; Second optical field regulation layer: 620; Third optical field regulation layer: 630; Tunnel junction layer: 700; Extended cavity: 800. Specific implementation manners

[0042] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, 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 "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types, and / or portions, these elements, components, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type, or portion from another element, component, region, layer, doping type, or portion. Thus, without departing from the teachings of the present invention, the first element, component, region, layer, doping type, or portion discussed below may be referred to as the second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types. For example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0045] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientation shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, an element or feature described as "under" or "beneath" or "underneath" another element or feature will be oriented "on" the other element or feature. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. In addition, the device may also include additional orientations (such as rotating 90 degrees or other orientations), and the spatial descriptors used herein are to be interpreted accordingly.

[0046] As used herein, the singular forms "a", "an", and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / comprising" or "has / including" etc. specify the presence of the stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the related listed items.

[0047] An embodiment of the present application provides a multi-junction VCSEL device. A multi-junction VCSEL device refers to a vertical cavity surface emitting laser (VCSEL) with a stacked structure of multiple PN junctions. Figure 1 is one of the schematic structural diagrams of a multi-junction VCSEL device in an embodiment. Refer to Figure 1 , the multi-junction VCSEL device includes a substrate 100, a bottom mirror structure 200, and a top mirror structure 300 sequentially disposed on the substrate 100. A standing wave is generated between the bottom mirror structure 200 and the top mirror structure 300. A standing wave is a wave formed by the superposition of two coherent waves propagating in opposite directions along the same straight line. Specifically, when the phases of the two waves are the same, their amplitudes are added to form a wave belly (i.e., a wave crest). When the phases of the two waves are opposite, their amplitudes are subtracted to form a wave node (i.e., a wave trough). Therefore, the positions of the wave crests and wave troughs of the standing wave are fixed.

[0048] Among them, the material of the substrate 100 includes but is not limited to GaAs, InP, Si, etc. The bottom mirror structure 200 and the top mirror structure 300 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 200 may be an N-type semiconductor layer, and the top mirror structure 300 may be a P-type semiconductor layer. Another example is that the bottom mirror structure 200 may be a P-type semiconductor layer, and the top mirror structure 300 may be an N-type semiconductor layer. Optionally, the materials of the N-type semiconductor layer and the P-type semiconductor layer may be but are not limited to GaAs, AlGaAs, etc., and are not limited herein as long as they can define the resonant cavity, and all belong to the protection scope of this embodiment. A plurality of active regions 400, a plurality of optical confinement layers 500, at least one optical field control layer 600, and an extended cavity 800 are provided between the bottom mirror structure 200 and the top mirror structure 300.

[0049] The number of active regions 400 may be, for example, 2, 3, 4, etc. Figure 1Three active regions 400 in a multi-junction VCSEL device are shown, namely a first active region 410, a second active region 420, and a third active region 430. The active regions 400 are used to generate stimulated emission photons, and the emitted photons are continuously reflected in a resonant cavity defined by a bottom mirror structure 200 and a top mirror structure 300, and are continuously enhanced during the reflection process, so as to finally emit laser light at a specific wavelength and with sufficient energy. The multiple active regions 400 in the multi-junction VCSEL device can emit light simultaneously, so that the light fields can be effectively superimposed between the multiple active regions 400, thereby optimizing the overall distribution of the light field.

[0050]

[0051] Furthermore, the above formula (1) is the calculation formula for the confinement factor of the target film layer. Among them, is the confinement factor of the target film layer, is the thickness of the target film layer in the z-axis direction, is the thickness of the entire light field in the z-axis direction, is the refractive index of the target film layer in the z-axis direction, is the refractive index of the entire light field in the z-axis direction, is the light field intensity in the z-axis direction. The z-axis direction is the light emission direction. It can be understood that on the premise that the thickness, refractive index, and light field intensity of the entire light field are basically unchanged, the integration result of the denominator in the calculation formula (1) is basically unchanged.

[0052] When the target film layer is the active region 400, since multiple active regions 400 are provided in the multi-junction VCSEL device, the thickness of the active region 400 in the z-axis direction is relatively large, so that the integration result of the numerator in the confinement factor calculation formula (1) will increase accordingly, so that the confinement factor of the active region 400 is relatively large, which further helps photons to obtain gain more fully, enabling the multi-junction VCSEL device to emit laser light at a lower injection current.

[0053] The number of the optoelectronic confinement layers 500 is not greater than the number of the active regions 400, and can be, for example, 2, 3, 4, etc. Figure 1Shows three optical confinement layers 500 in a multi-junction VCSEL device, namely the first optical confinement layer 510, the second optical confinement layer 520, and the third optical confinement layer 530. The optical confinement layer 500 is used to define the light-emitting region of the multi-junction VCSEL device. Specifically, the optical confinement layer 500 is located on the side of the corresponding active region 400 away from the substrate 100 to restrict the flow of current, so that the current only flows within the light-emitting region defined by the optical confinement layer 500, thereby reducing unnecessary energy consumption, further reducing the threshold current, and increasing the current density. Moreover, the optical confinement layer 500 can also confine the optical field within the light-emitting region defined by the optical confinement layer 500, reducing light scattering and diffraction, thereby optimizing the divergence angle of the VCSEL and improving the beam quality. Continuing to refer to the calculation formula (1), when the target film layer is the optical confinement layer 500, since the optical confinement layer 500 is arranged at the trough of the standing wave, the electric field at the optical confinement layer 500 is small, and the electric field strength is positively correlated with the optical field strength. Therefore, the integration result of the numerator in the calculation formula (1) of the confinement factor will decrease accordingly. Since the integration result of the denominator remains basically unchanged, the confinement factor of the optical confinement layer 500 is small, which helps to reduce the divergence angle of the multi-junction VCSEL device.

[0054] The extended cavity 800 is arranged on the side of the bottom mirror structure or the top mirror structure close to the active region, that is, at least one of the bottom mirror structure and the top mirror structure is adjacent to the extended cavity 800. Among them, the optical field intensity in the extended cavity 800 is greater than the optical field intensity of the adjacent active region, so that the refractive index difference between the inside and outside of the light-emitting hole of the multi-junction VCSEL device can be reduced, the generation of high-order modes can be suppressed, and the divergence angle of the multi-junction VCSEL device can be reduced.

[0055] The optical field regulation layer 600 is arranged adjacent to the optical confinement layer 500, or on the side of the extended cavity 800 close to the active region 400. The optical field regulation layer 600 is configured to divide the optical field between the bottom mirror structure and the top mirror structure into multiple segments, and the intensity of each segment of the optical field is different. Figure 1Three optical field regulation layers 600 in a multi-junction VCSEL device are shown, where two optical field regulation layers 600 are disposed between adjacent active regions, and one optical field regulation layer 600 is disposed on the side of the extended cavity 800 close to the active region 400, so that the optical field in the resonant cavity structure can be divided into four segments. It can be understood that the closer the distance between the optical confinement layer 500 and the optical field regulation layer 600, the greater the degree of reduction in the diffusion of current on the surface of the active region 400 after passing through the optical confinement layer 500. Therefore, in this embodiment, by arranging the optical field regulation layer 600 between the optical confinement layer 500 and the active region 400, the confinement factor of the optical confinement layer 500 can be effectively regulated on the premise of better reducing current diffusion. Moreover, by setting the structure and / or composition of the optical field regulation layer 600, the optical field intensity of each segment of the optical field can be flexibly adjusted. Based on different optical field distributions, different scenario applications can be realized, thereby improving the applicability of the multi-junction VCSEL device to different scenarios.

[0056] In the embodiments of the application, by inserting at least one optical field regulation layer 600 in the multi-junction VCSEL device, the optical field between the bottom mirror structure 200 and the top mirror structure 300 can be divided into multiple segments. Due to the segmenting effect of the optical field regulation layer 600 on the optical field, the optical field intensity at the optical field regulation layer 600 is also weak, so the optical field intensity of the optical confinement layer 500 adjacent to the optical field regulation layer 600 can also be restricted. Based on the positive correlation between the confinement factor of the film layer and the electric field intensity and optical field intensity at its location, the above setting method effectively reduces the confinement factor of the optical confinement layer 500, thereby achieving the suppression of high-order modes and achieving the effect of a low divergence angle. Moreover, by increasing the extended cavity 800 to increase the optical field intensity inside the multi-junction VCSEL device, the refractive index difference between the inside and outside of the light-emitting aperture of the multi-junction VCSEL device can be reduced, thereby suppressing high-order modes and further reducing the divergence angle. Therefore, the application provides a multi-junction VCSEL device with a smaller confinement factor of the optical confinement layer 500 and a larger confinement factor of the active region 400, thereby improving the performance of the multi-junction VCSEL device in terms of divergence angle and threshold current.

[0057] In one embodiment, the extended cavity 800 includes an antireflection layer and a light storage layer. The antireflection layer is disposed adjacent to the light storage layer. The antireflection layer is used to increase the light field intensity of the light storage layer, and the light storage layer is used to store light field energy. Specifically, the antireflection layer may include a first antireflection interface at the interface from a low refractive index to a high refractive index, and a second antireflection interface at the interface from a high refractive index to a low refractive index. That is, the first antireflection interface and the second antireflection interface are respectively disposed on both sides of the light storage layer. The antireflection layer can be formed by periodically stacking multiple layers of materials with a thickness of a quarter wavelength and different refractive indices, for example, by periodically stacking AlGaAs with different Al components. The antireflection layer can extract light from the active region 400 and store it in the light storage layer, thereby accommodating photons to increase the light field intensity, so that there is a strong light field and electric field in the light storage layer. The thickness of the light storage layer is an odd multiple of half of the lasing wavelength, such as 5.5 times half of the lasing wavelength, 10.5 times half of the lasing wavelength, etc. It can be understood that as long as the extended cavity 800 can enhance the light field intensity and electric field intensity, its structure and phase can be flexibly set and are not limited here.

[0058] In one embodiment, the light field control layer 600 includes a photonic crystal structure, or a single-layer structure, or a periodically stacked DBR structure. Specifically, the periodically stacked DBR (Distributed Bragg Reflector) structure realizes efficient reflection or transmission of light within a specific wavelength range through the periodic stacking of multiple layers of materials with different refractive indices. Among them, the optical thickness of each layer in the periodically stacked DBR structure is 1 / 4 of the lasing wavelength. The material of the periodically stacked DBR structure includes any one of semiconductor materials and metals. Exemplarily, the DBR structure of semiconductor materials is, for example, composed of alternately stacked GaAs and AlGaAs with different refractive indices, or composed of alternately stacked InGaAs and GaAsP with different refractive indices, or composed of alternately stacked InGaAs and AlGaAs with different refractive indices. The DBR structure of metals is, for example, composed of alternately stacked silver and aluminum with different refractive indices. Due to the periodic change of the dielectric constant of the photonic crystal itself, a photonic bandgap can be formed, and thus, by controlling the position and width of the bandgap, the reflection or transmission of light within a specific wavelength range can be realized. In some embodiments, the light field control layer 600 can also be composed of dielectric materials, metal-dielectric hybrid materials, etc., and is not limited here.

[0059] In one embodiment, when the light field control layer 600 includes a periodically stacked DBR structure, the periodically stacked DBR structure is composed of Al x Ga （1-x） As / Al y Ga （1-y）Alternately constituted, 0 ≤ x < y ≤ 1. Specifically, by adjusting the proportion of aluminum and gallium in the AlGaAs material system, the refractive index and bandgap of the periodically stacked DBR structure can be precisely controlled, thereby achieving the reflection or transmission of light of a specific wavelength. Further, the number of stacking periods is between 3 pairs and 10 pairs, where a pair includes two adjacent film layers with different refractive indices. For example, if the number of stacking periods of the light field modulation layer 600 is 3 pairs, then the DBR structure of one light field modulation layer 600 includes Al x Ga （1-x） As layer, Al y Ga （1-y） As layer, Al x Ga （1-x） As layer, Al y Ga （1-y） As layer, Al x Ga （1-x） As layer and Al y Ga （1-y） As layer. It can be understood that the more the number of stacking periods of the DBR structure of the light field modulation layer 600, the lower the confinement factor of the optical confinement layer 500, but at the same time, the problem of current diffusion will be aggravated, thus having a greater impact on the light emission efficiency of the active region 400 after the optical confinement layer 500. Therefore, in this embodiment, each light field modulation layer 600 is respectively provided with 3 to 10 pairs of stacking periods, which can have a lower confinement factor of the optical confinement layer 500 on the premise that the current diffusion problem is controllable. It should be noted that the number of stacking periods of the DBR structure of each light field modulation layer 600 can be the same or different, and can be specifically set according to the requirements of the light field, which is not limited here.

[0060] In one embodiment, at least one of the side of the optoelectronic confinement layer 500 close to the substrate 100 and the side away from the substrate 100 is provided with a light field modulation layer 600. That is to say, the light field modulation layer 600 can be provided on one side of the optoelectronic confinement layer 500, or one light field modulation layer 600 can be provided on each of the two sides of the optoelectronic confinement layer 500 respectively. Exemplarily, when one light field modulation layer 600 is provided on each of the two sides of the optoelectronic confinement layer 500, one of the light field modulation layers 600 located on the side of the optoelectronic confinement layer 500 close to the substrate 100 and the side away from the substrate 100 includes a photonic crystal structure, and the other light field modulation layer 600 includes a periodically stacked DBR structure. Another exemplarily, when one light field modulation layer 600 is provided on each of the two sides of the optoelectronic confinement layer 500, the light field modulation layers 600 on both sides are both periodically stacked DBR structures or both photonic crystal structures. That is to say, the specific type of each light field modulation layer 600 can be set as needed, without being limited to the same structure of the two light field modulation layers 600 adjacent to the same optoelectronic confinement layer 500, both being periodically stacked DBR structures or both photonic crystal structures. By respectively selecting the specific type of each light field modulation layer 600, it is easier to achieve the required reflection coefficient, and thus more flexibly achieve the required multi-segment light field.

[0061] Figure 2 Schematic diagram II of the structure of a multi-junction VCSEL device according to an embodiment, refer to Figure 2 In one embodiment, when the light field modulation layer 600 is located on the side of the optoelectronic confinement layer 500 away from the substrate 100, a tunnel junction layer 700 is further provided between the light field modulation layer 600 and the optoelectronic confinement layer 500. The tunnel junction layer 700 can limit the flow position of the current as a current path, enabling the current to flow more in the central region near the central axis of the multi-junction VCSEL device, reducing the diffusion of the current from the central region to the outside, which is beneficial to the laser emitting from the center of the multi-junction VCSEL device. Moreover, the tunnel junction layer 700 can also reduce the non-radiative recombination of carriers at the tunnel junction layer 700, ensuring that more current is used to generate useful photons, thereby increasing the probability of radiative recombination and improving the light field quality.

[0062] Moreover, by providing a tunnel junction layer 700 between the optical field modulation layer 600 and the optoelectronic confinement layer 500, the change rate of the optical field intensity at the optoelectronic confinement layer 500 and the optical field modulation layer 600 can be slowed down, so that the optical field intensity at the optoelectronic confinement layer 500 and the optical field modulation layer 600 can be continuously maintained at a relatively low level. It can be understood that if the process causes a certain shift in the position of the optoelectronic confinement layer 500 in the optical field, it may cause the optoelectronic confinement layer 500 not to be located at the trough of the standing wave. Based on the positive correlation between the confinement factor and the optical field intensity, when the shift causes the optical intensity at the optoelectronic confinement layer 500 to increase, the confinement factor of the optoelectronic confinement layer 500 will increase, thus affecting the performance of the multi-junction VCSEL device. In one embodiment, when the optical field modulation layers 600 on both sides of the optoelectronic confinement layer 500 are both periodically stacked DBR structures, the stacking periods of the DBR structures in the optical field modulation layers 600 on both sides are different. Specifically, the periodically stacked DBR structure includes a first DBR functional layer and a second DBR functional layer that are alternately stacked and have different refractive indices. The refractive indices of the first DBR functional layers of the two optical field modulation layers 600 adjacent to the same optoelectronic confinement layer 500 are the same, and when the refractive indices of the second DBR functional layers of each optical field modulation layer 600 are the same, the stacking periods of the DBR structures of the two optical field modulation layers 600 adjacent to the same optoelectronic confinement layer 500 are different.

[0063] Furthermore, the components of the elements affecting the refractive index in the first DBR functional layers of the two optical field modulation layers 600 adjacent to the same optoelectronic confinement layer 500 can be made the same, so that the refractive indices of the first DBR functional layers of each optical field modulation layer 600 are the same. Similarly, the components of the elements affecting the refractive index in the second DBR functional layers of each optical field modulation layer 600 can be made the same, so that the refractive indices of the second DBR functional layers of each optical field modulation layer 600 are the same. Taking the first DBR functional layer as Al x Ga （1-x） As and the second DBR functional layer as Al y Ga （1-y） As as an example, where 0 ≤ x < y ≤ 1. The x value of the first DBR functional layer in one optical field modulation layer 600 can be made the same as the x value of the first DBR functional layer in the other optical field modulation layer 600, and the y value of the second DBR functional layer in one optical field modulation layer 600 can be made the same as the y value of the second DBR functional layer in the other optical field modulation layer 600. Exemplarily, the two optical field modulation layers 600 can both be composed of Al 0.25 Ga 0.75 As / Al 0.5 Ga 0.5 As stacked alternately.

[0064] The stacking periods of the DBR structures of the two optical field modulation layers 600 adjacent to the same optoelectronic confinement layer 500 are different. It can be that the stacking period of the DBR structure of the optical field modulation layer 600 closer to the substrate 100 is greater than that of the DBR structure of the optical field modulation layer 600 farther from the substrate 100, or it can be that the stacking period of the DBR structure of the optical field modulation layer 600 farther from the substrate 100 is greater than that of the DBR structure of the optical field modulation layer 600 closer to the substrate 100, and no limitation is made here. It can be understood that the larger the stacking period of the DBR structure of the optical field modulation layer 600, the more interfaces the photons will be reflected at, that is, the reflection coefficient of the optical field modulation layer 600 will be changed. Therefore, the different stacking periods of the DBR structures of the two optical field modulation layers 600 adjacent to the same optoelectronic confinement layer 500 mean that the reflection coefficients of the two optical field modulation layers 600 are different, so that the photons generated in the active region 400 are emitted from one of the optical field modulation layers 600 after obtaining the required gain, so as to realize the flexible control of the optical field intensity.

[0065] In one embodiment, the optoelectronic confinement layer 500 includes any one of an air column type optoelectronic confinement layer 500, an oxidation confinement type optoelectronic confinement layer 500, an ion implantation type optoelectronic confinement layer 500, and a tunnel junction type optoelectronic confinement layer 500. Among them, the air column type optoelectronic confinement layer 500 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 in the central region. The ion implantation type optoelectronic confinement layer 500 changes its electrical properties by implanting ions into the semiconductor material to form a high-resistance region, and the high-resistance region can limit the flow of current, thereby indirectly limiting the light generation region.

[0066] In one embodiment, the oxidation confinement type optoelectronic confinement layer 500 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 optoelectronic confinement layer 500 can be understood as an opening, and the opening is used to define the light-emitting region of the multi-junction VCSEL device. When current enters, the current can only flow to the active region 400 through the opening in the optoelectronic confinement layer 500, so as to realize 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. Furthermore, the opening sizes of different optoelectronic confinement layers 500 can be the same or different. In the case where the openings of multiple optoelectronic confinement layers 500 are different, the light-emitting region defined by the optoelectronic confinement layer 500 with the smallest opening is used as the light-emitting region of the multi-junction VCSEL device.

[0067] In one embodiment, the tunnel junction type optoelectronic confinement layer 500 includes at least one highly doped N-type structural layer and at least one highly doped P-type structural layer. Specifically, a potential barrier is formed between the highly doped N-type structural layer and the highly doped P-type structural layer, and electrons are allowed to pass through the potential barrier by tunneling effect, thereby realizing the lateral confinement of current. In one embodiment, the materials of the N-type structural layer and the P-type structural layer are selected as Al x Ga 1-x As, and the doping concentration of the N-type structural layer and the P-type structural layer is greater than 1e 18 cm -3 , where 0 ≤ x ≤ 1.

[0068] Figure 3 FIG. 3 is a schematic diagram of the structure of a multi-junction VCSEL device according to an embodiment. Referring to Figure 3 , in one embodiment, at least one multi-quantum well structure 401 is provided in each active region 400. That is, the active region 400 may include only one multi-quantum well structure 401, or may include a composite structure formed by a plurality of multi-quantum well structures 401 arranged in layers. The composite structure may be formed by laminating materials such as GaAs and AlGaAs, InGaAs and GaAsP, or InGaAs and AlGaAs, but is not limited thereto. The multi-quantum well structure 401 is used to convert electrical energy into light energy, thereby generating laser light.

[0069] It can be understood that the multi-quantum well structure 401 is the place where laser gain amplification occurs. The central position of the multi-quantum well structure 401 can be aligned with the position where the optical field is the strongest to achieve a greater amplification effect. Further, in the case where a segmented optical field includes a plurality of multi-quantum well structures 401, the confinement factors of the multi-quantum well structures 401 in the same segment of the optical field are within the same preset range. That is, the confinement factors of each multi-quantum well structure 401 are maintained at the same level, so that the contribution of each multi-quantum well structure 401 to light emission is similar. It can be understood that similar light emission contributions mean that the injection of current into each multi-quantum well structure 401 is more uniform, which helps to reduce the threshold current of the multi-junction VCSEL device, thereby reducing the power consumption of the multi-junction VCSEL device and prolonging its service life. Moreover, when the contribution of each multi-quantum well structure 401 to light emission is similar, the distribution of carriers in each multi-quantum well structure 401 will be more uniform, which helps to reduce the recombination loss of carriers, thereby improving the overall light emission efficiency of the multi-junction VCSEL device.

[0070] In addition, taking the tunnel junction layer 700 disposed adjacent to the first optical confinement layer 510 as an example, since the side of the multiple quantum well structure 401 away from the substrate 100 in the first active region 410 is heavily P-doped near the first optical confinement layer 510. And in the tunnel junction layer 700 disposed adjacent to the first optical confinement layer 510, its side near the first optical confinement layer 510 is also heavily P-doped. Therefore, if the tunnel junction layer 700 is disposed on the side of the first optical confinement layer 510 close to the substrate 100, it will cause the two P-type heavily doped regions to be too close, and the P-type heavily doped region has certain light absorption characteristics. The two P-type heavily doped regions with a relatively short distance will further enhance the light absorption, resulting in a decline in the performance of the multi-junction VCSEL device. In the embodiment of the application, the tunnel junction layer 700 is disposed on the side of the first optical confinement layer 510 away from the substrate 100, which can effectively improve the above light absorption problem.

[0071] In one embodiment, there are multiple multiple quantum well structures 401 between the bottom mirror structure 200 and the nearest optical field modulation layer 600. Since there are multiple multiple quantum well structures 401 between the bottom mirror structure 200 and the nearest optical field modulation layer 600, it is equivalent to increasing the thickness of the active region 400 in the Z-axis direction, such that the confinement factor in the active region 400 divided by the optical field modulation layer 600 basically does not change much, ensuring that the reduction of the confinement factor in the active region 400 is small. In one embodiment, there are three multiple quantum well structures 401 between the optical field modulation layer 600 and the nearest optical field modulation layer 600.

[0072] In one embodiment, each active region 400 is connected by a tunnel junction layer 700. That is, the tunnel junction layer 700 is located between two adjacent multiple quantum well structures 401. The tunnel junction layer 700, as the current path, can limit the flow position of the current, enabling the current to flow more in the central region near the central axis of the multi-junction VCSEL device, reducing the diffusion of the current from the central region to the outside, which is thus conducive to the laser emitting from the center of the multi-junction VCSEL device. Moreover, the tunnel junction layer 700 can also reduce the non-radiative recombination of carriers at the tunnel junction layer 700, ensuring that more current is used to generate useful photons, thereby increasing the probability of radiative recombination and improving the optical field quality.

[0073] In one embodiment, the multi-junction VCSEL device includes three active regions 400, three optical confinement layers 500, and three optical field control layers 600. Among them, the three active regions 400 include a first active region 410, a second active region 420, and a third active region 430 arranged in sequence along the direction away from the substrate 100. The three optical confinement layers 500 include a first optical confinement layer 510, a second optical confinement layer 520, and a third optical confinement layer 530. The three optical field control layers 600 include a first optical field control layer 610, a second optical field control layer 620, and a third optical field control layer 630. The first optical confinement layer 510 is located between the first active region 410 and the second active region 420. The second optical confinement layer 520 is located between the second active region 420 and the third active region 430. The third optical confinement layer 530 is located on the side of the third active region 430 close to the top mirror structure 300. Further, the first active region 410 includes three multi-quantum well structures 401, the second active region 420 includes two multi-quantum well structures 401, and the third active region 430 includes two multi-quantum well structures 401. Among them, adjacent multi-quantum well structures 401 within each active region 400 are connected by a tunnel junction layer 700. The first optical field control layer 610 is disposed between the extended cavity 800 and the first active region 410. The second optical field control layer 620 is disposed between the first active region 410 and the first optical confinement layer 510. The third optical field control layer 630 is disposed between the second active region 420 and the third optical confinement layer 530.

[0074] Figure 4 Refers to the refractive index and optical field intensity diagram of the multi-junction VCSEL device of an embodiment Figure 4, in this embodiment, based on the periodically stacked DBR structure of the optical field modulation layer 600, the refractive index at the optical field modulation layer 600 changes periodically, while the refractive index at the extended cavity 800 remains unchanged. Among them, the DBR structure in the optical field modulation layer 600 can be referred to as the first DBR structure, and the DBR structures in the bottom mirror structure 200 and the top mirror structure 300 can be referred to as the second DBR structure. The refractive index of the high-refractive-index film layer in the first DBR structure is higher than that of the high-refractive-index film layer in the second DBR structure. The refractive index of the first optoelectronic confinement layer 510 is lower than that of the multi-quantum well structure 401 closest to the first optical field modulation layer 610 in the second active region 420 and lower than that of the low-refractive-index film layer in the first DBR structure of the first optical field modulation layer 610. The refractive index of the second optoelectronic confinement layer 520 is lower than that of the multi-quantum well structure 401 closest to the second optical field modulation layer 620 in the third active region 430 and lower than that of the low-refractive-index film layer in the first DBR structure of the second optical field modulation layer 620. Among them, the optical field in the extended cavity 800 has a stable peak, and the optical field intensity in the extended cavity 800 is significantly stronger than that at other positions in the multi-junction VCSEL device, indicating that the extended cavity 800 can effectively enhance the optical field. Moreover, the optical field intensities of the active regions 400 on both sides of the same optical field modulation layer 600 are different. Specifically, the optical field intensity of each active region 400 gradually decreases as the distance from the substrate increases, indicating that the optical field modulation layer 600 effectively divides the optical field in the resonant cavity.

[0075] The embodiment of the present application also provides a VCSEL chip, which can be a flip-chip VCSEL chip. The VCSEL chip includes a positive electrode, a negative electrode, and the multi-junction VCSEL device as described above. Exemplarily, the positive electrode and the negative electrode are respectively electrically connected to the bottom mirror structure 200 and the top mirror structure 300 of the multi-junction VCSEL device, and the positive electrode and the negative electrode are located on the side opposite to the light-emitting side of the VCSEL chip. Another example is that the positive electrode and the negative electrode are respectively electrically connected to the top mirror structure 300 and the bottom mirror structure 200 of the multi-junction VCSEL device, and the positive electrode and the negative electrode are located on the side opposite to the light-emitting side of the VCSEL chip. Based on the foregoing multi-junction VCSEL device, the VCSEL chip of this embodiment can have better performance in terms of divergence angle and threshold current. In addition, the flip-chip VCSEL chip can be connected to the substrate and the carrier through bumps, which can reduce the need for wire bonding, thereby not only simplifying the packaging technology but also reducing the system inductance of the flip-chip VCSEL chip, helping to improve the overall optoelectronic conversion efficiency of the flip-chip VCSEL chip.

[0076] The embodiments of the present application further provide a VCSEL chip, which includes at least one laser array. The laser array includes a plurality of multi-junction VCSEL devices 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 multi-junction VCSEL devices, the VCSEL chip of this embodiment can have better performance in terms of divergence angle and threshold current.

[0077] The embodiments of the present application further provide a light source for a lidar system, including at least one multi-junction VCSEL device as described above or at least one VCSEL chip as described above.

[0078] The embodiments of the present application further provide a lidar system, including a transmitting component and a receiving component, wherein the transmitting component uses the light source for the lidar system as described above.

[0079] Embodiments of the utility model are described herein with reference to cross-sectional views that are schematic illustrations of ideal embodiments (and intermediate structures) of the utility model. It is to be expected that variations in the shapes as illustrated may result, for example, from manufacturing techniques and / or tolerances. Accordingly, embodiments of the utility model should not be construed as limited to the particular shapes of regions shown herein, but include shape deviations resulting, for example, from manufacturing techniques. For example, an implantation region shown as rectangular will typically have rounded or curved features at its edges and / or an implantation concentration gradient, rather than a binary change from the implanted region to the non-implanted region. Similarly, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions shown in the figures are substantially schematic in nature, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of the utility model.

[0080] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0081] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above 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.

[0082] The above embodiments only illustrate several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patented application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A multi-junction VCSEL device, characterized in that: include: substrate; A bottom reflector structure and a top reflector structure stacked on the substrate; A plurality of active regions and a plurality of photoelectric limiting layers, each of the photoelectric limiting layers is located on a side of the corresponding active region away from the substrate, and the photoelectric limiting layer is used to limit the light emitting area of ​​the multi-junction VCSEL device; An extended cavity is provided on a side of the bottom reflector structure or the top reflector structure close to the active area, and the light field intensity in the extended cavity is greater than the light field intensity of the adjacent active area; At least one light field regulation layer is arranged adjacent to the photoelectric confinement layer or on a side of the extended cavity close to the active area, and the light field regulation layer is configured to divide the light field between the bottom reflector structure and the top reflector structure into multiple segments, and the intensity of each light field segment is different.

2. The multi-junction VCSEL device according to claim 1, characterized in that: The extended cavity comprises a transmittance-enhancing layer and a light storage layer. The transmittance-enhancing layer is arranged adjacent to the light storage layer. The transmittance-enhancing layer is used to increase the light field intensity of the light storage layer. The light storage layer is used to store light field energy.

3. The multi-junction VCSEL device according to claim 2, characterized in that: The thickness of the light storage layer is an odd multiple of half the lasing wavelength.

4. The multi-junction VCSEL device according to claim 1, characterized in that: The light field regulation layer includes a photonic crystal structure, a single layer structure, or a periodically stacked DBR structure.

5. The multi-junction VCSEL device according to claim 4, characterized in that: When the light field regulation layer includes a periodically stacked DBR structure, the periodically stacked DBR structure is composed of Al x Ga （1-x） As / Al y Ga （1-y） As are alternately constructed, and the number of stacking cycles is between 3 pairs and 10 pairs, 0≤x<y≤1.

6. The multi-junction VCSEL device according to claim 4, characterized in that: The light field regulating layer is provided on at least one of a side of the photoelectric limiting layer close to the substrate and a side of the photoelectric limiting layer far from the substrate.

7. The multi-junction VCSEL device according to claim 6, characterized in that: When the light field regulating layer is located at a side of the photoelectric limiting layer away from the substrate, a tunnel junction layer is further provided between the light field regulating layer and the photoelectric limiting layer.

8. The multi-junction VCSEL device according to claim 4, characterized in that: When the light field regulation layers located on both sides of the photoelectric confinement layer are both periodically stacked DBR structures, the stacking period numbers of the DBR structures in the light field regulation layers on both sides are different.

9. The multi-junction VCSEL device according to any one of claims 1 to 8, characterized in that: The photoelectric confinement layer includes any one of an air column type photoelectric confinement layer, an oxidation confinement type photoelectric confinement layer, an ion implantation type photoelectric confinement layer and a tunnel junction type photoelectric confinement layer.

10. The multi-junction VCSEL device according to claim 9, characterized in that: The oxidation-limited photoelectric limiting layer includes an unoxidized region of AlGaAs material with a high Al content and an oxidized region of aluminum oxide material. The oxidized region is arranged outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection.

11. The multi-junction VCSEL device according to claim 9, characterized in that: The tunnel junction type photoelectric confinement layer includes at least one highly doped N-type structure layer and at least one highly doped P-type structure layer.

12. The multi-junction VCSEL device according to claim 11, characterized in that: The material of the N-type structure layer and the P-type structure layer is selected as Al x Ga 1-x As, 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.

13. The multi-junction VCSEL device according to claim 1, characterized in that: At least one multi-quantum well structure is arranged in each active region, and a plurality of the multi-quantum well structures are arranged between the bottom reflector structure and the nearest light field regulation layer.

14. The multi-junction VCSEL device according to claim 13, characterized in that: There are three multi-quantum well structures between the bottom reflector structure and the nearest light field regulation layer.

15. The multi-junction VCSEL device according to claim 1, characterized in that: The active regions are connected via a tunnel junction layer.

16. The multi-junction VCSEL device according to any one of claims 1 to 8, characterized in that: The multi-junction VCSEL device comprises three active regions and three photoelectric limiting layers; the three active regions comprise a first active region, a second active region and a third active region sequentially arranged in a direction away from the substrate, and the two photoelectric limiting layers comprise a first photoelectric limiting layer, a second photoelectric limiting layer and a third photoelectric limiting layer; The first photoelectric limiting layer is located between the first active region and the second active region, the second photoelectric limiting layer is located between the second active region and the third active region, and the third photoelectric limiting layer is located on a side of the third active region close to the top reflector structure.

17. The multi-junction VCSEL device according to claim 16, characterized in that: The first active region includes three multi-quantum well structures, the second active region includes two multi-quantum wells, and the third active region includes two multi-quantum well structures; and adjacent multi-quantum well structures in each active region are connected via a tunnel junction layer.

18. A VCSEL chip, characterized in that: The VCSEL chip comprises a positive electrode, a negative electrode and a multi-junction VCSEL device according to any one of claims 1 to 17; Wherein, the positive electrode and the negative electrode are electrically connected to the bottom reflector structure and the top reflector structure of the multi-junction VCSEL device respectively; or The positive electrode and the negative electrode are electrically connected to the top reflector structure and the bottom reflector structure of the multi-junction VCSEL device respectively; The positive electrode and the negative electrode are located on the side opposite to the light emitting side of the VCSEL chip.

19. A VCSEL chip, characterized in that: It comprises at least one laser array; the laser array comprises a plurality of multi-junction VCSEL devices as described in any one of claims 1 to 17; the laser array is a regularly arranged array, or a randomly arranged array, or an array with a plurality of addressable sub-arrays.

20. A light source for a laser radar system, characterized in that: The method comprises at least one multi-junction VCSEL device according to any one of claims 1 to 17 or at least one VCSEL chip according to claim 18 or 19.

21. A laser radar, characterized in that: It comprises a transmitting component and a receiving component, wherein the transmitting component adopts the light source for the laser radar system as described in claim 20.

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