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

Abstract

The embodiment of the invention 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; the bottom reflector structure and the top reflector structure define a resonant cavity structure used for generating standing waves. The resonant cavity structure comprises 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 located at wave troughs of standing waves and are used for limiting a light emitting region of the multi-junction VCSEL device; and the light field regulation and control layers are arranged adjacent to the photoelectric limiting layer, the light field regulation and control layers are configured to divide the light field in the resonant cavity structure into at least three 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 in particular to a multi-junction VCSEL device, a VCSEL chip, a laser radar system and a light source thereof. Background Art

[0002] With the continuous development of semiconductor technology, Vertical-Cavity Surface-Emitting Laser (VCSEL) is widely used in optical communication, optical interconnection, optical sensing and other fields due to its easy integration characteristics. The main application scenario in the field of optical sensing is laser radar. High-power VCSEL devices are the main technical direction for future applications in laser radar. High-power VCSELs usually require cascading multiple active layers to achieve. However, the limiting factor of the oxide layer in the multi-junction VCSEL device with multiple active layers cascaded is relatively high, resulting in a larger emission angle of the multi-junction VCSEL device, which limits the use scenarios of multi-junction VCSEL devices. Summary of the invention

[0003] Based on this, it is necessary to provide a multi-junction VCSEL device, a VCSEL chip, a laser radar system and a light source thereof to address the problem of a 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, comprising:

[0005] substrate;

[0006] A bottom reflector structure and a top reflector structure stacked on the substrate; the bottom reflector structure and the top reflector structure define a resonant cavity structure for generating a standing wave;

[0007] The resonant cavity structure comprises a plurality of active regions and a plurality of photoelectric limiting layers, each of the photoelectric limiting layers is respectively located on a side of the corresponding active region away from the substrate, and the photoelectric limiting layer is located at a trough of the standing wave, and the photoelectric limiting layer is used to limit the light emitting area of ​​the multi-junction VCSEL device;

[0008] A plurality of light field regulation layers are provided adjacent to the photoelectric confinement layer, and the light field regulation layers are configured to divide the light field in the resonant cavity structure into at least three sections, and the intensity of each section of the light field is different.

[0009] In one embodiment, the light field regulation layer includes a photonic crystal structure or a periodically stacked first DBR structure.

[0010] In one of the embodiments, the bottom reflector structure and the top reflector structure respectively include a periodically stacked second DBR structure;

[0011] The refractive index of the high refractive index film layer in the first DBR structure is higher than the refractive index of the high refractive index film layer in the second DBR structure.

[0012] In one embodiment, the active region includes at least one multi-quantum well structure, and the refractive index of the photoelectric confinement layer is lower than the refractive index of the multi-quantum well structure closest to the light field regulation layer in the active region, and is lower than the refractive index of the low-refractive index film layer in the first DBR structure.

[0013] In one embodiment, when the light field regulation layer includes a periodically stacked first DBR structure, the periodically stacked first 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.

[0014] In one of the embodiments, the light field regulating layer is provided on at least one of a side of the photoelectric confinement layer close to the substrate and a side of the photoelectric confinement layer far from the substrate.

[0015] In one of the embodiments, when the light field regulation layer is located on a side of the photoelectric confinement layer away from the substrate, a tunnel junction layer is further disposed between the light field regulation layer and the photoelectric confinement layer.

[0016] In one of the embodiments, when one of the light field regulation layers is provided on both sides of the photoelectric limiting layer, one of the light field regulation layers located on a side of the photoelectric limiting layer close to the substrate and a side of the photoelectric limiting layer away from the substrate includes a photonic crystal structure, and the other light field regulation layer includes a periodically stacked first DBR structure.

[0017] In one embodiment, the resonant cavity structure includes three active regions and three photoelectric confinement layers; the three active regions include 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 confinement layers include a first photoelectric confinement layer, a second photoelectric confinement layer and a third photoelectric confinement layer;

[0018] 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.

[0019] 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 via a tunnel junction layer.

[0020] In one embodiment, the multi-junction VCSEL device includes two light field regulation layers, wherein the first light field regulation layer is disposed between the first active region and the first optoelectronic confinement layer, and the second light field regulation layer is disposed between the second active region and the second optoelectronic confinement layer.

[0021] In one embodiment, 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.

[0022] In one embodiment, 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, wherein the oxidized region is arranged outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection.

[0023] In one embodiment, 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.

[0024] In one embodiment, the material of the N-type structure layer and the P-type structure layer is 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.

[0025] In a second aspect, the present application provides a VCSEL chip, wherein the VCSEL chip comprises an anode, a cathode and a multi-junction VCSEL device as described above;

[0026] 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

[0027] 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;

[0028] The positive electrode and the negative electrode are located on the side opposite to the light emitting side of the VCSEL chip.

[0029] In a third aspect, the present application provides a VCSEL chip comprising at least one laser array; the laser array comprises 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.

[0030] In a fourth aspect, the present application provides a light source for a lidar system, comprising at least one multi-junction VCSEL device as described above or at least one VCSEL chip as described above.

[0031] In a fifth aspect, the present application provides a laser radar, including a transmitting component and a receiving component, wherein the transmitting component adopts the above-mentioned light source for the laser radar system.

[0032] The above-mentioned multi-junction VCSEL device, VCSEL chip, laser radar system and light source thereof can divide the light field in the resonant cavity structure into at least three sections by inserting multiple light field control layers in the resonant cavity structure of the multi-junction VCSEL device. By setting the structure and / or composition of the light field control layer, the light field intensity of each section of the light field can be flexibly adjusted. Since the photoelectric confinement layer is located at the trough of the standing wave, the electric field intensity at the photoelectric confinement layer can be made lower. Moreover, due to the segmented effect of the light field control layer on the light field, the light field intensity at the light field control layer is also weak, so it is also possible to limit the light field intensity of the adjacent photoelectric confinement layer. Based on the positive correlation between the confinement factor of the film layer and the electric field intensity and the light field intensity where it is located, the above-mentioned setting method effectively reduces the confinement factor of the photoelectric confinement layer, thereby achieving the suppression of high-order modes and achieving the effect of low divergence angle. Therefore, the present application provides a multi-junction VCSEL device with a small confinement factor of the photoelectric confinement layer and a large confinement factor of the active region, thereby improving the performance of the multi-junction VCSEL device in terms of divergence angle and threshold current. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 This is one of the structural schematic diagrams of a multi-junction VCSEL device according to an embodiment;

[0035] Figure 2 This is a second structural schematic diagram of a multi-junction VCSEL device according to an embodiment;

[0036] Figure 3The third structural schematic diagram of a multi-junction VCSEL device according to an embodiment;

[0037] Figure 4 Graph showing the refractive index and light field intensity of a multi-junction VCSEL device according to an embodiment.

[0038] Component number description:

[0039] Substrate: 100; bottom reflector structure: 200; top reflector structure: 300; active area: 400; multi-quantum well structure: 401; first active area: 410; second active area: 420; third active area: 430; photoelectric confinement layer: 500; first photoelectric confinement layer: 510; second photoelectric confinement layer: 520; third photoelectric confinement layer: 530; light field regulation layer: 600; first light field regulation layer: 610; second light field regulation layer: 620; tunnel junction layer: 700. DETAILED DESCRIPTION

[0040] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided 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, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, 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 parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, doping type or portion discussed below may be represented as a 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.

[0043] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0044] When used herein, the singular forms "a", "an" and " / the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, 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 relevant listed items.

[0045] An embodiment of the present application provides a multi-junction VCSEL device, which refers to a vertical cavity surface emitting laser (VCSEL) having a multi-layer PN junction stacked structure. Figure 1 FIG. 1 is a schematic diagram of a multi-junction VCSEL device according to an embodiment of the present invention. Figure 1 The multi-junction VCSEL device includes a substrate 100 and a bottom reflector structure 200, a resonant cavity structure and a top reflector structure 300 sequentially arranged on the substrate 100. The resonant cavity structure is defined by the bottom reflector structure 200 and the top reflector structure 300, that is, the area between the bottom reflector structure 200 and the top reflector structure 300 is the resonant cavity. The resonant cavity is used to generate standing waves. Standing waves are waves formed by two coherent waves propagating in opposite directions on the same straight line and superimposed on each other. Specifically, when the two waves are in the same phase, their amplitudes are added to form an antinode (i.e., a crest). When the two waves are in opposite phases, their amplitudes are subtracted to form a node (i.e., a trough). Therefore, the positions of the crest and trough of the standing wave are fixed.

[0046] Among them, the material of the substrate 100 includes but is not limited to GaAs, InP, Si, etc. The bottom reflector structure 200 and the top reflector structure 300 may include a film layer with a periodic change in refractive index to achieve efficient reflection or transmission of light within a specific wavelength range. The film layer with a periodic change in refractive index can be composed of semiconductor materials, dielectric materials, metal-dielectric mixed materials, etc. For example, the bottom reflector structure 200 can be an N-type semiconductor layer, and the top reflector structure 300 can be a P-type semiconductor layer. For another example, the bottom reflector structure 200 can be a P-type semiconductor layer, and the top reflector structure 300 can be an N-type semiconductor layer. Optionally, the material of the N-type semiconductor layer and the P-type semiconductor layer can be but is not limited to GaAs, AlGaAs, etc., which is not limited here. As long as the definition of the resonant cavity can be achieved, it belongs to the protection scope of this embodiment. Specifically, the resonant cavity structure includes multiple active regions 400, multiple photoelectric confinement layers 500, and multiple light field regulation layers 600.

[0047] 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 region 400 is used to generate stimulated radiated photons, and the emitted photons are continuously reflected in the resonant cavity defined by the bottom reflector structure 200 and the top reflector structure 300, and are continuously enhanced during the reflection process, thereby finally emitting laser light at a specific wavelength and having sufficient energy. Multiple active regions 400 in a multi-junction VCSEL device can emit light simultaneously, so that the light field can be effectively superimposed between the multiple active regions 400, thereby optimizing the overall distribution of the light field.

[0048]

[0049] Furthermore, the above formula (1) is a calculation formula for the limiting factor of the target film layer. is the limiting 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 refers to the light emission direction. It can be understood that, under the premise that the thickness, refractive index and light field intensity of the entire light field remain basically unchanged, the integral result of the denominator in the calculation formula (1) remains basically unchanged.

[0050] 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 integral result of the numerator in the calculation formula (1) of the limitation factor will increase accordingly, thereby making the limitation factor of the active region 400 larger, which in turn helps the photons to obtain gain more fully, so that the multi-junction VCSEL device can achieve laser emission at a lower injection current.

[0051] The number of the photoelectric limiting layers 500 is not greater than the number of the active regions 400, for example, it may be 2, 3, 4, etc. Figure 1Three photoelectric confinement layers 500 in a multi-junction VCSEL device are shown, namely, a first photoelectric confinement layer 510, a second photoelectric confinement layer 520, and a third photoelectric confinement layer 530. The photoelectric confinement layer 500 is used to limit the light-emitting area of ​​the multi-junction VCSEL device. Specifically, the photoelectric confinement layer 500 is located on the side of the corresponding active area 400 away from the substrate 100 to limit the flow of current so that the current only flows in the light-emitting area defined by the photoelectric confinement layer 500, thereby reducing unnecessary energy consumption, thereby reducing the threshold current, and increasing the current density. Moreover, the photoelectric confinement layer 500 can also confine the light field in the light-emitting area defined by the photoelectric confinement layer 500, reducing the scattering and diffraction of light, thereby optimizing the divergence angle of the VCSEL and improving the beam quality. Continuing to refer to calculation formula (1), when the target film layer is the photoelectric confinement layer 500, since the photoelectric confinement layer 500 is set at the trough of the standing wave, the electric field at the photoelectric confinement layer 500 is small, and the electric field strength is positively correlated with the light field strength. Therefore, the integral result of the numerator in the calculation formula (1) of the limitation factor will decrease accordingly. Since the integral result of the denominator remains basically unchanged, the limitation factor of the optoelectronic limitation layer 500 is small, which helps to reduce the divergence angle of the multi-junction VCSEL device.

[0052] The number of light field control layers 600 is not greater than the number of optoelectronic confinement layers 500, for example, it can be 2, 3, 4, etc. The light field control layers 600 are used to divide the light field in the resonant cavity structure into at least three sections, and the intensity of each section of the light field is different. Figure 1 Two light field control layers 600 in a multi-junction VCSEL device are shown, which are a first light field control layer 610 and a second light field control layer 620. The two light field control layers 600 can divide the light field in the resonant cavity structure into three sections. Among them, the light field control layer 600 is arranged adjacent to the photoelectric confinement layer 500. It can be understood that the closer the distance between the photoelectric confinement layer 500 and the light field control layer 600 is, the greater the diffusion of the current on the surface of the active area 400 after passing through the photoelectric confinement layer 500 can be reduced. Therefore, in this embodiment, the light field control layer 600 is arranged between the photoelectric confinement layer 500 and the active area 400, which can effectively control the confinement factor of the photoelectric confinement layer 500 under the premise of better reducing the current diffusion. By setting the structure and / or composition of the light field control layer 600, the light field intensity of each section of the light field can be flexibly adjusted. Based on different light field distributions, different scene applications can be realized, thereby improving the applicability of the multi-junction VCSEL device to different scenes.

[0053] In the embodiment of the application, by inserting multiple light field control layers 600 in the resonant cavity structure of the multi-junction VCSEL device, the light field in the resonant cavity structure can be divided into at least three sections. By setting the structure and / or composition of the light field control layer 600, the light field intensity of each section of the light field can be flexibly adjusted. Since the photoelectric confinement layer 500 is located at the trough of the standing wave, the electric field intensity at the photoelectric confinement layer 500 can be made lower. Moreover, due to the segmentation effect of the light field control layer 600 on the light field, the light field intensity at the light field control layer 600 is also weak, so it is also possible to limit the light field intensity of the photoelectric confinement layer 500 located between the two light field control layers 600. Based on the positive correlation between the confinement factor of the film layer and the electric field intensity and light field intensity where it is located, the above-mentioned setting method effectively reduces the confinement factor of the photoelectric confinement layer 500, thereby suppressing the high-order mode and achieving the effect of low divergence angle. Therefore, the present application provides a multi-junction VCSEL device with a smaller confinement factor of the optoelectronic 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.

[0054] In one embodiment, the light field control layer 600 includes a photonic crystal structure or a periodically stacked first DBR structure. Specifically, the periodically stacked DBR (Distributed Bragg Reflector) structure achieves efficient reflection or transmission of light within a specific wavelength range by periodically stacking multiple layers of materials with different refractive indices. Among them, the optical thickness of each layer in the periodically stacked first DBR structure is 1 / 4 of the lasing wavelength. The material of the periodically stacked first DBR structure includes any one of semiconductor materials and metals. Exemplarily, the first DBR structure of semiconductor material is composed of alternating stacks of GaAs and AlGaAs with different refractive indices, or alternating stacks of InGaAs and GaAsP with different refractive indices, or alternating stacks of InGaAs and AlGaAs with different refractive indices. The first DBR structure of metal is composed of, for example, alternating stacks of silver and aluminum with different refractive indices. Photonic crystals can form photonic energy gaps because of their own periodic dielectric constant changes, so that reflection or transmission of light within a specific wavelength range can be achieved by controlling the position and width of the energy gap. In some embodiments, the light field control layer 600 may also be made of dielectric materials, metal-dielectric mixed materials, etc., which is not limited here.

[0055] In one embodiment, the bottom reflector structure 200 includes a periodically stacked second DBR structure, that is, it includes multiple reflectors with an optical thickness of one quarter of the laser wavelength, and the multiple reflectors are arranged alternately according to high and low refractive indices. The top reflector structure 300 also includes a periodically stacked second DBR structure, that is, multiple reflectors with an optical thickness of one quarter of the laser wavelength, and the multiple reflectors are arranged alternately according to high and low refractive indices. It can be understood that the components, stacking period number, etc. of the second DBR structure of the bottom reflector structure 200 and the second DBR structure of the top reflector structure 300 can be the same or different, and this embodiment does not limit it. Among them, the material of the top reflector structure 300 and the bottom reflector structure 200 can be a dielectric material with electrical insulation, for example, it can include silicon nitride, silicon oxide, aluminum oxide or titanium oxide. The material of the top reflector structure 300 and the bottom reflector structure 200 can also be a semiconductor material, for example, it can include GaAs and AlGaAs.

[0056] Furthermore, the refractive index of the high refractive index film layer in the first DBR structure is higher than the refractive index of the high refractive index film layer in the second DBR structure. It can be understood that, under the premise that the refractive indexes of the low refractive index film layers in the first DBR structure and the second DBR structure are the same or similar, increasing the refractive index of the high refractive index film layer in the first DBR structure can make the refractive index difference inside the first DBR structure greater than the refractive index difference inside the second DBR structure, so that the first DBR structure has a higher reflection coefficient to realize the light field segmentation function of the light field regulation layer.

[0057] Figure 2 FIG. 2 is a second structural diagram of a multi-junction VCSEL device according to an embodiment of the present invention. Figure 2 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 consisting of a plurality of multi-quantum well structures 401 stacked in layers. The composite structure may be, but is not limited to, composed of GaAs and AlGaAs, InGaAs and GaAsP, or InGaAs and AlGaAs materials stacked in layers. The multi-quantum well structure 401 is used to convert electrical energy into light energy, thereby generating laser light.

[0058] It can be understood that the multi-quantum well structure 401 is where the laser gain amplification is generated, and the center position of the multi-quantum well structure 401 can be aligned with the position where the light field is the strongest, so as to achieve a greater amplification effect. Further, in the case where a segmented light field includes multiple multi-quantum well structures 401, the confinement factors of the multi-quantum well structures 401 in the same segment of the light 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 luminescence is similar. It can be understood that similar luminescence contributions mean that the injection of current in 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 extending its service life. Moreover, when the contribution of each multi-quantum well structure 401 to luminescence 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 luminescence efficiency of the multi-junction VCSEL device.

[0059] In one embodiment, the refractive index of the optoelectronic confinement layer is lower than the refractive index of the multi-quantum well structure closest to the optical field regulation layer in the active region, and is lower than the refractive index of the low-refractive index film layer in the first DBR structure.

[0060] In one embodiment, there are multiple multi-quantum well structures 401 between the bottom reflector structure 200 and the nearest light field regulation layer 600. Since there are multiple multi-quantum well structures 401 between the bottom reflector structure 200 and the nearest light field regulation layer 600, it is equivalent to increasing the thickness of the active area 400 in the Z-axis direction, so that the confinement factor in the active area 400 divided by the light field regulation layer 600 does not change much, ensuring that the confinement factor in the active area 400 is reduced less. In one embodiment, there are three multi-quantum well structures 401 between the bottom reflector structure 200 and the nearest first light field regulation layer 610.

[0061] 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 multi-quantum well structures 401. The tunnel junction layer 700, as a current path, can limit the flow position of the current, so that the current flows more in the central area near the central axis of the multi-junction VCSEL device, reducing the diffusion of the current from the central area to the outside, thereby facilitating the laser to be emitted from the center of the multi-junction VCSEL device. In addition, 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 quality of the light field.

[0062] In one embodiment, the resonant cavity structure includes three active regions 400 and three photoelectric confinement layers 500. The three active regions 400 include a first active region 410, a second active region 420 and a third active region 430 sequentially arranged in a direction away from the substrate 100, and the three photoelectric confinement layers 500 include a first photoelectric confinement layer 510, a second photoelectric confinement layer 520 and a third photoelectric confinement layer 530. The first photoelectric confinement layer 510 is located between the first active region 410 and the second active region 420, the second photoelectric confinement layer 520 is located between the second active region 420 and the third active region 430, and the third photoelectric confinement layer 530 is located on one side of the third active region 430 close to the top reflector 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. The adjacent multi-quantum well structures 401 in each active region 400 are connected via a tunnel junction layer 700. Furthermore, the multi-junction VCSEL device includes two light field regulation layers 600, wherein the first light field regulation layer 610 is disposed between the first active region 410 and the first photoelectric confinement layer 510, and the second light field regulation layer 620 is disposed between the second active region 420 and the second photoelectric confinement layer 520.

[0063] In one embodiment, when the light field control layer 600 includes a periodically stacked first DBR structure, the periodically stacked first DBR structure is composed of Al x Ga （1-x） As / Al y Ga （1-y） As is alternately composed. Specifically, by adjusting the proportion of aluminum and gallium in the AlGaAs material system, the refractive index and band gap of the periodically stacked first DBR structure can be precisely controlled, thereby realizing the reflection or transmission of light of a specific wavelength. Furthermore, the number of stacking periods is between 3 pairs and 10 pairs, and 0≤x<y≤1. Among them, a pair includes two adjacent film layers with different refractive indices. For example, if the number of stacking periods of the light field control layer 600 is 3 pairs, then the first DBR structure of a light field control layer 600 includes Al stacked in sequence. 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 stacking periods of the first DBR structure of the light field control layer 600, the lower the limitation factor of the photoelectric limiting layer 500 can be, but it will also aggravate the problem of current diffusion, thereby increasing the impact on the luminous efficiency of the active area 400 after the photoelectric limiting layer 500. Therefore, in this embodiment, each light field control layer 600 is configured to include 3 to 10 pairs of stacking periods, which can have a lower limitation factor of the photoelectric limiting layer 500 under the premise that the current diffusion problem is controllable. It should be noted that the stacking period numbers of the first DBR structure of each light field control layer 600 can be the same or different, and can be specifically set according to the requirements for the light field, which is not limited here.

[0064] In one embodiment, at least one of the side of the photoelectric confinement layer 500 close to the substrate 100 and the side away from the substrate 100 is provided with a light field control layer 600. That is, the light field control layer 600 may be provided on one side of the photoelectric confinement layer 500, or a light field control layer 600 may be provided on both sides of the photoelectric confinement layer 500. In an exemplary embodiment, when a light field control layer 600 is provided on both sides of the photoelectric confinement layer 500, one of the light field control layers 600 located on the side of the photoelectric 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 control layer 600 includes a periodically stacked first DBR structure. In another exemplary embodiment, when a light field control layer 600 is provided on both sides of the photoelectric confinement layer 500, the light field control layers 600 on both sides are periodically stacked first DBR structures or photonic crystal structures. That is, the specific type of each light field control layer 600 can be set as needed, and is not limited to the two light field control layers 600 adjacent to the same photoelectric confinement layer 500 having the same structure, both being periodically stacked first DBR structures or both being photonic crystal structures. By selecting the specific type of each light field control layer 600, it is easier to achieve the required reflection coefficient, thereby more flexibly achieving the required multi-segment light field.

[0065] Figure 3 FIG. 3 is a schematic diagram of the structure of a multi-junction VCSEL device according to an embodiment of the present invention. Figure 3In one embodiment, when the light field regulation layer 600 is located on the side of the photoelectric confinement layer 500 away from the substrate 100, a tunnel junction layer 700 is further provided between the light field regulation layer 600 and the photoelectric confinement layer 500. The tunnel junction layer 700, as a path for current, can limit the flow position of the current, so that the current flows more in the central area near the central axis of the multi-junction VCSEL device, reducing the diffusion of the current from the central area to the outside, thereby facilitating the laser to be emitted 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 quality of the light field.

[0066] Moreover, by setting a tunnel junction layer 700 between the light field regulation layer 600 and the photoelectric restriction layer 500, the speed of change of the light field intensity at the photoelectric restriction layer 500 and the light field regulation layer 600 can be slowed down, so that the light field intensity at the photoelectric restriction layer 500 and the light field regulation layer 600 can be continuously located at a lower position. It can be understood that if the process causes a certain offset in the position of the photoelectric restriction layer 500 in the light field, it may cause the photoelectric restriction layer 500 to be unable to be located at the trough of the standing wave. Based on the positive correlation between the confinement factor and the light field intensity, when the offset causes the light intensity at the photoelectric restriction layer 500 to increase, the confinement factor of the photoelectric restriction layer 500 will increase, thereby affecting the performance of the multi-junction VCSEL device. In addition, taking the tunnel junction layer 700 disposed adjacent to the first photoelectric restriction layer 510 as an example, since the multi-quantum well structure 401 in the first active region 410 that is far away from the substrate 100 is close to the first photoelectric restriction layer 510, a P-type heavy doping is used. In the tunnel junction layer 700 disposed adjacent to the first photoelectric confinement layer 510, the side close to the first photoelectric confinement layer 510 is also heavily doped with P-type. Therefore, if the tunnel junction layer 700 is disposed on the side of the first photoelectric confinement layer 510 close to the substrate 100, two P-type heavily doped regions will be too close, and the P-type heavily doped region has certain light absorption characteristics. The two P-type heavily doped regions that are close will further enhance light absorption, thereby causing the performance of the multi-junction VCSEL device to decrease. In the embodiment of the application, the tunnel junction layer 700 is disposed on the side of the first photoelectric confinement layer 510 that is away from the substrate 100, which can effectively improve the above-mentioned light absorption problem.

[0067] In one of the embodiments, when the light field control layers 600 located on both sides of the optoelectronic confinement layer 500 are periodically stacked first DBR structures, the stacking period numbers of the first DBR structures in the light field control layers 600 on both sides are different. Specifically, the periodically stacked first DBR structure includes alternately stacked first DBR functional layers and second DBR functional layers with different refractive indices, and when the refractive indices of the first DBR functional layers of the two light field control layers 600 adjacent to the same optoelectronic confinement layer 500 are the same, and the refractive indices of the second DBR functional layers of the light field control layers 600 are the same, the stacking period numbers of the first DBR structures of the two light field control layers 600 adjacent to the same optoelectronic confinement layer 500 are different.

[0068] Furthermore, the components of the elements affecting the refractive index in the first DBR functional layers of the two light field control layers 600 adjacent to the same photoelectric confinement layer 500 can be made the same, so that the refractive index of the first DBR functional layers of each light field control layer 600 is the same. Similarly, the components of the elements affecting the refractive index in the second DBR functional layers of each light field control layer 600 can be made the same, so that the refractive index of the second DBR functional layers of each light field control layer 600 is the same. x Ga （1-x） As, the second DBR functional layer is Al y Ga （1-y） As is taken as an example, where 0≤x<y≤1. The x value of the first DBR functional layer in one light field control layer 600 can be the same as the x value of the first DBR functional layer in another light field control layer 600, and the y value of the second DBR functional layer in one light field control layer 600 can be the same as the y value of the second DBR functional layer in another light field control layer 600. For example, both light field control layers 600 can be made of Al 0.25 Ga 0.75 As / Al 0.5 Ga 0.5 As are stacked alternately.

[0069] The different stacking period numbers of the first DBR structures of the two light field control layers 600 adjacent to the same photoelectric confinement layer 500 may be that the stacking period number of the first DBR structure of the light field control layer 600 close to the substrate 100 is greater than the stacking period number of the first DBR structure of the light field control layer 600 away from the substrate 100, or the stacking period number of the first DBR structure of the light field control layer 600 away from the substrate 100 is greater than the stacking period number of the first DBR structure of the light field control layer 600 close to the substrate 100, which is not limited here. It can be understood that the larger the stacking period number of the first DBR structure of the light field control layer 600, the more interfaces the photons will be reflected at, that is, the reflection coefficient of the light field control layer 600 will be changed. Therefore, the different stacking period numbers of the first DBR structures of the two light field control layers 600 adjacent to the same photoelectric confinement layer 500 means that the reflection coefficients of the two light field control layers 600 are different, so that the photons generated by the active region 400 are emitted from the light field control layer 600 on one side after obtaining the required gain, so as to realize flexible control of the light field intensity.

[0070] The photoelectric confinement layer 500 includes any one of an air column type photoelectric confinement layer 500, an oxidation confinement type photoelectric confinement layer 500, an ion implantation type photoelectric confinement layer 500, and a tunnel junction type photoelectric confinement layer 500. Among them, the air column type photoelectric confinement layer 500 realizes the restriction of current and light through air columns, and the air column is a hollow structure formed by dry etching technology, and its refractive index is lower than that of the surrounding semiconductor material, thereby effectively restricting the light in the central area. The ion implantation type photoelectric confinement layer 500 changes its electrical properties by injecting ions into the semiconductor material to form a high resistance area, which can restrict the flow of current, thereby indirectly restricting the light generation area.

[0071] In one embodiment, the oxidation-restricted photoelectric confinement layer 500 includes an unoxidized region of AlGaAs material with a high Al component 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. Among them, the semiconductor layer of the unoxidized region in the photoelectric 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 the current enters, the current can only flow to the active area 400 through the opening in the photoelectric confinement layer 500, thereby realizing the restriction of the current injection path and the optical mode field. Further, the AlGaAs layer with a high aluminum component can be converted into aluminum oxide through a selective oxidation process to form an unoxidized region on the periphery. Further, the opening sizes of different photoelectric confinement layers 500 can be the same or different. In the case where the openings of multiple photoelectric confinement layers 500 are different, the light-emitting region defined by the photoelectric confinement layer 500 with the smallest opening is used as the light-emitting region of the multi-junction VCSEL device.

[0072] In one embodiment, the tunnel junction type photoelectric confinement layer 500 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 by tunneling, thereby achieving lateral confinement of the current. In one embodiment, the material of the N-type structure layer and the P-type structure layer is 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.

[0073] Figure 4 The refractive index and light field intensity diagram of a multi-junction VCSEL device of an embodiment are shown in FIG. Figure 4 In this embodiment, based on the periodically stacked first DBR structure of the light field control layer 600, the refractive index at the light field control layer 600 presents a periodic change. Among them, the first light field control layer 610 and the second light field control layer 620 include a first DBR structure, and the bottom reflector structure 200 and the top reflector structure 300 include a second DBR structure. The refractive index of the high refractive index film layer in the first DBR structure is higher than the refractive index of the high refractive index film layer in the second DBR structure. The refractive index of the first photoelectric confinement layer 510 is lower than the refractive index of the multi-quantum well structure 401 closest to the first light field control layer 610 in the second active region 420, and is lower than the refractive index of the low refractive index film layer in the first DBR structure of the first light field control layer 610. The refractive index of the second photoelectric confinement layer 520 is lower than the refractive index of the multi-quantum well structure 401 closest to the second light field control layer 620 in the third active region 430, and is lower than the refractive index of the low refractive index film layer in the first DBR structure of the second light field control layer 620. Moreover, the light field intensities of the active regions 400 on both sides of the same light field regulation layer 600 are different, indicating that the light field regulation layer 600 effectively divides the light field in the resonant cavity. Specifically, the light field intensity of each active region 400 shows a gradually decreasing trend in the direction away from the substrate 100.

[0074] The embodiment of the present application also provides a VCSEL chip, which can be a flip-chip VCSEL chip, and the VCSEL chip includes a positive electrode, a negative electrode and a multi-junction VCSEL device as described above. In an exemplary embodiment, the positive electrode and the negative electrode are electrically connected to the bottom reflector structure 200 and the top reflector structure 300 of the multi-junction VCSEL device, respectively, and the positive electrode and the negative electrode are located on the side opposite to the light-emitting side of the VCSEL chip. In another exemplary embodiment, the positive electrode and the negative electrode are electrically connected to the top reflector structure 300 and the bottom reflector structure 200 of the multi-junction VCSEL device, respectively, 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 aforementioned 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 connects the chip to the substrate and the carrier through the bump, 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, which helps to improve the overall photoelectric conversion efficiency of the flip-chip VCSEL chip.

[0075] The embodiment of the present application also provides a VCSEL chip, which includes at least one laser array. The laser array includes a plurality of multi-junction VCSEL devices as described above, and the laser array is a regularly arranged array, or a randomly arranged array, or an array with multiple addressable sub-arrays. Based on the aforementioned multi-junction VCSEL device, the VCSEL chip of this embodiment can have better performance in terms of divergence angle and threshold current.

[0076] An embodiment of the present application also provides a light source for a laser radar system, comprising at least one multi-junction VCSEL device as described above or at least one VCSEL chip as described above.

[0077] An embodiment of the present application also provides a laser radar system, including a transmitting component and a receiving component, wherein the transmitting component adopts the above-mentioned light source for the laser radar system.

[0078] Embodiments of the invention are described herein with reference to cross-sectional views which are schematic diagrams of ideal embodiments (and intermediate structures) of the invention, such that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Thus, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include deviations in shapes due to, for example, manufacturing techniques. For example, an implanted region shown as a rectangle typically has rounded or curved features and / or an implant concentration gradient at its edges rather than a binary change from an implanted region to a 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 is performed. Thus, the regions shown in the figures are schematic in nature, their shapes do not represent the actual shape of the region of the device, and do not limit the scope of the invention.

[0079] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0080] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0081] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached 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; The bottom reflector structure and the top reflector structure define a resonant cavity structure for generating a standing wave; The resonant cavity structure comprises a plurality of active regions and a plurality of photoelectric limiting layers, each of the photoelectric limiting layers is respectively located on a side of the corresponding active region away from the substrate, and the photoelectric limiting layer is located at a trough of the standing wave, and the photoelectric limiting layer is used to limit the light emitting area of ​​the multi-junction VCSEL device; A plurality of light field regulation layers are provided adjacent to the photoelectric confinement layer, and the light field regulation layers are configured to divide the light field in the resonant cavity structure into at least three sections, and the intensity of each section of the light field is different.

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

3. The multi-junction VCSEL device according to claim 2, characterized in that: The bottom reflector structure and the top reflector structure respectively include a periodically stacked second DBR structure; The refractive index of the high refractive index film layer in the first DBR structure is higher than the refractive index of the high refractive index film layer in the second DBR structure.

4. The multi-junction VCSEL device according to claim 2, characterized in that: The active region includes at least one multi-quantum well structure, and the refractive index of the photoelectric confinement layer is lower than the refractive index of the multi-quantum well structure closest to the light field regulation layer in the active region, and is lower than the refractive index of the low-refractive index film layer in the first DBR structure.

5. The multi-junction VCSEL device according to claim 2, characterized in that: When the light field regulation layer includes a periodically stacked first DBR structure, the periodically stacked first 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 2, 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 6, characterized in that: When one of the light field regulation layers is provided on both sides of the photoelectric limiting layer, one of the light field regulation layers located on a side of the photoelectric limiting layer close to the substrate and a side of the photoelectric limiting layer far from the substrate comprises a photonic crystal structure, and the other light field regulation layer comprises a periodically stacked first DBR structure.

9. The multi-junction VCSEL device according to any one of claims 1 to 8, characterized in that: The resonant cavity structure includes three active regions and three photoelectric confinement layers; the three active regions include 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 confinement layers include a first photoelectric confinement layer, a second photoelectric confinement layer and a third photoelectric confinement 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.

10. The multi-junction VCSEL device according to claim 9, 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.

11. The multi-junction VCSEL device according to claim 9, characterized in that: The multi-junction VCSEL device includes two light field regulation layers, wherein the first light field regulation layer is arranged between the first active region and the first photoelectric confinement layer, and the second light field regulation layer is arranged between the second active region and the second photoelectric confinement layer.

12. 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.

13. The multi-junction VCSEL device according to claim 12, 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.

14. The multi-junction VCSEL device according to claim 12, characterized in that: The tunnel junction type photoelectric limiting layer includes at least one highly doped N-type structure layer and at least one highly doped P-type structure layer.

15. The multi-junction VCSEL device according to claim 14, 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.

16. 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 15; 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.

17. 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 15; the laser array is a regularly arranged array, or a randomly arranged array, or an array with a plurality of addressable sub-arrays.

18. 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 15 or at least one VCSEL chip according to claim 16 or 17.

19. A laser radar, characterized in that: It comprises a transmitting component and a receiving component, and the transmitting component adopts the light source for the laser radar system as described in claim 18.

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