A multi-junction vertical cavity surface emitting laser

Abstract

The application provides a multi-junction vertical cavity surface emitting laser, which is characterized in that: a tunneling junction is arranged between two adjacent groups of multi-quantum well layers in a resonant cavity layer; the multi-quantum well layers are arranged at an antinode position of a standing wave, and the electric field intensity at the antinode position is used to obtain the maximum laser gain effect; at least part of the tunneling junction is arranged at a node position of the standing wave, and the tunneling junction comprises an N-type layer and a P-type layer which are stacked in a first direction; the tunneling junction is configured by arranging at least part of the P-type layer at the node position to reduce the light absorption of the P-type layer; the interface between the N-type layer and the P-type layer is offset from the node position; further, the interface between the N-type layer and the P-type layer is offset from the node position along the side of the substrate. In this way, the P-type layer can be arranged more at the adjacent position of the node, thereby reducing the light absorption of the P-type layer and improving the electro-optical conversion efficiency of the whole optical device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light emitting diodes, and in particular to a multi-junction vertical cavity surface emitting laser. BACKGROUND

[0002] A vertical cavity surface emitting laser (VCSEL) is a semiconductor microcavity laser. Compared with a conventional edge-emitting laser, a VCSEL has the advantages of low threshold current, small volume, circularly symmetric beam for easy fiber coupling, high beam quality, single longitudinal mode, and surface emission for easy integration. In recent years, VCSELs have been rapidly developed and widely used in three-dimensional sensing, optical communication, laser radar, and unmanned driving.

[0003] Currently, the VCSEL chips mainly used are single-junction VCSELs. The single-hole light output power of a single-junction VCSEL is generally 5-10 mW. For large three-dimensional sensing application scenarios, such as the field of laser radar-based unmanned driving, a single-junction VCSEL cannot meet the requirements, and a laser with greater power and higher efficiency is needed. To achieve greater light output power, it is usually considered to increase the light-emitting area of the chip. However, this approach increases the size of the light-emitting surface and the cost of materials, not only increasing the difficulty of optical design, but also making it difficult to miniaturize the terminal product.

[0004] By using a tunnel junction technology, multiple semiconductor laser epitaxial layers can be directly connected in series during material epitaxy. In this way, multiple lasers can be integrated in a smaller space, effectively increasing the optical power density. Similarly, a vertical cavity surface emitting laser (VCSEL) can also connect multiple quantum wells in the resonant cavity through a tunnel junction to increase the optical power. Therefore, as a new round of development of VCSELs, multi-junction VCSEL technology has become a research hotspot. A multi-junction VCSEL contains multiple cascaded active regions, which can improve the internal quantum efficiency of the device and reduce the carrier density, thereby obtaining higher gain. Multi-junction VCSELs have many obvious advantages. For example, higher efficiency can reduce the overall thermal load; higher power density greatly reduces the size of the chip and package, thereby simplifying the optical design and system architecture.

[0005] However, infrared VCSELs are usually grown on a GaAs substrate, and the most widely used laser wavelength is 940 nm. To achieve a design wavelength of 940 nm, the MQW needs to use InGaAs quantum wells. The InGaAs quantum well is relatively mismatched with the GaAs substrate lattice, and the growth of multiple quantum well layers will cause stress accumulation, eventually forming dislocations to release stress, affecting the performance and reliability of the device. In particular for a multi-junction VCSEL, the active region is connected by multiple groups of multiple quantum well layers through a tunnel junction. The increase in the number of multiple quantum well layers will increase the stress accumulation, making it difficult to avoid the formation of dislocations.

[0006] Meanwhile, the Moss-Burstein effect caused by the high doping of the tunnel junctions will result in light absorption, especially the free carrier absorption of the P-type layer is higher than that of the N-type layer. However, the cascade VCSEL has multiple sets of tunnel junctions in the resonant cavity, so the light absorption of the tunnel junctions will inevitably affect the photoelectric efficiency of the cascade VCSEL.

[0007] Therefore, the present inventors specially designed a multi-junction vertical cavity surface emitting laser, and the present case was generated. SUMMARY

[0008] The present application aims to provide a multi-junction vertical cavity surface emitting laser to solve the problems of lattice mismatch and light absorption of the tunnel junctions of the cascade VCSEL.

[0009] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0010] A multi-junction vertical cavity surface emitting laser, comprising:

[0011] a substrate and an N-type DBR reflection layer, a resonant cavity layer and a P-type DBR reflection layer stacked in sequence along the surface of the substrate;

[0012] The resonant cavity layer forms a standing wave by resonance, which includes a plurality of sets of multiple quantum well layers; and a tunnel junction is further provided between adjacent two sets of multiple quantum well layers; wherein the tunnel junction includes an N-type layer and a P-type layer stacked in sequence along a first direction, and at least part of the tunnel junction is arranged at a node position of the standing wave, so that the tunnel junction reduces the light absorption of the P-type layer by arranging at least part of the P-type layer at the node position.

[0013] Preferably, the multiple quantum well layers are arranged at an anti-node position of the standing wave, so as to obtain the maximum laser gain by the electric field intensity at the anti-node position.

[0014] Preferably, along the first direction, the interface between the N-type layer and the P-type layer has a deviation distance from the node position.

[0015] Preferably, the interface between the N-type layer and the P-type layer deviates from the node position along the side of the substrate.

[0016] Preferably, the value of the deviation distance is not greater than the thickness value of the P-type layer.

[0017] Preferably, an oxidation layer is provided on the side of each multiple quantum well layer facing the P-type DBR reflection layer.

[0018] Preferably, the substrate includes a GaAs substrate.

[0019] Preferably, each set of multiple quantum well layers contains a plurality of quantum well layers and a plurality of quantum barrier layers.

[0020] Preferably, the multiple quantum well layer comprises an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure.

[0021] Preferably, an ohmic contact layer is arranged on the side surface of the P-type DBR reflection layer away from the substrate.

[0022] According to the technical solution described above, the multiple-junction vertical cavity surface emitting laser provided by the application has the following advantages: a tunnel junction is arranged between two adjacent multiple quantum well layers in the resonant cavity layer; the multiple quantum well layer is arranged at the antinode position of the standing wave, and the electric field strength at the antinode position is used to obtain the maximum laser gain effect; at least part of the tunnel junction is arranged at the node position of the standing wave, and the tunnel junction comprises an N-type layer and a P-type layer which are stacked in the first direction; and the P-type layer is arranged at the node position to reduce the light absorption of the P-type layer.

[0023] Secondly, the interface between the N-type layer and the P-type layer is offset from the node position by a distance, and further, the interface between the N-type layer and the P-type layer is offset from the node position along the side of the substrate. In this way, the P-type layer can be arranged more at the position adjacent to the node, thereby reducing the light absorption of the P-type layer and improving the electro-optical conversion efficiency of the entire vertical cavity surface emitting laser.

[0024] Finally, in a preferred embodiment of the application, the distance of the offset is not greater than the thickness of the P-type layer, so that the P-type layer can be arranged on both sides of the node position to the maximum extent, thereby reducing the light absorption of the P-type layer to the limit and further improving the electro-optical conversion efficiency of the entire vertical cavity surface emitting laser. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort based on the provided drawings.

[0026] Figure 1 Structure diagram of the multiple-junction vertical cavity surface emitting laser provided by the embodiment of the application;

[0027] Figure 2 Structure diagram of the N-type DBR reflection layer provided by the embodiment of the application;

[0028] Figure 3 Structure diagram of the multiple quantum well layer provided by the embodiment of the application;

[0029] Figure 4 This is a schematic diagram of the tunnel junction provided in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the structure of the P-type DBR reflective layer provided in an embodiment of the present invention;

[0031] Explanation of symbols in the diagram:

[0032] 1. Substrate;

[0033] 2. Buffer layer;

[0034] 3. N-type DBR reflective layer; 31. High refractive index film; 32. Low refractive index film;

[0035] 4. Restriction layer; 41. First restriction layer; 42. Second restriction layer; 43. Third restriction layer; 44. Fourth restriction layer; 45. Fifth restriction layer; 46. Sixth restriction layer;

[0036] 5. Multiple quantum well layers, 5a. Well layer, 5b. Barrier layer, 51. First group of multiple quantum well layers, 52. Second group of multiple quantum well layers, 53. Third group of multiple quantum well layers;

[0037] 6. Oxide layer; 61. First oxide layer; 62. Second oxide layer; 63. Third oxide layer;

[0038] 7. Tunneling junction; 7a. N-type layer; 7b. P-type layer; 71. First tunneling junction; 72. Second tunneling junction;

[0039] 8. P-type DBR reflective layer; 81. High refractive index film; 82. Low refractive index film;

[0040] 9. Ohmic contact layer. Detailed Implementation

[0041] To make the content of this invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates the invention. This invention is not limited to this specific embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0042] like Figure 1 As shown, a multi-junction vertical-cavity surface-emitting laser includes:

[0043] Substrate 1 and N-type DBR reflective layer 3, resonant cavity layer and P-type DBR reflective layer 8 stacked sequentially along the surface of substrate 1;

[0044] The resonant cavity layer forms a standing wave by resonance, which includes a plurality of groups of multiple quantum well layers 5 and a tunnel junction 7 arranged between adjacent two groups of multiple quantum well layers 5; wherein at least part of the tunnel junction 7 is arranged at a node position of the standing wave, and as shown in Figure 4 The tunnel junction 7 includes an N-type layer 7a and a P-type layer 7b stacked in sequence along a first direction, and the tunnel junction 7 reduces the light absorption of the P-type layer 7b by arranging at least part of the P-type layer 7b at the node position.

[0045] In the embodiment, the multiple quantum well layers 5 are arranged at an anti-node position of the standing wave, and the electric field strength at the anti-node position is the maximum to obtain the maximum laser gain.

[0046] In the embodiment, the resonant cavity layer arranged between the N-type DBR reflection layer 3 and the P-type DBR reflection layer 8 includes M groups of multiple quantum well layers 5, M is a positive integer greater than or equal to 2, for example, M = 2, M = 3, M = 4, M = 5, etc.; as shown in Figure 3 Each of the multiple quantum well layers 5 includes a well layer 5a and a barrier layer 5b stacked alternately.

[0047] Specifically, in the vertical cavity surface emitting laser, the substrate 1 is a GaAs substrate 1. In other embodiments of the present application, the substrate 1 can also be other semiconductor materials. When the substrate 1 is other semiconductor materials, the materials of the N-type DBR reflection layer 3, the resonant cavity layer and the P-type DBR reflection layer 8 can be selected according to the material of the substrate 1 to achieve stress balance.

[0048] Further, based on the above-mentioned embodiments of the present application, when the substrate 1 is a GaAs substrate 1, the multiple quantum well layer 5 includes an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure, that is, in an embodiment of the present application, the well layer 5a includes an InGaAs layer, and the barrier layer 5b includes an AlGaAs layer or a GaAsP. In other embodiments of the present application, the well layer 5a can include an InAlGaAs layer, and the barrier layer 5b can include an AlGaAsP barrier layer, which is not limited by the present application.

[0049] It should be noted that in the embodiments of the present application, since the tunnel junction 7 is used to connect adjacent two groups of multiple quantum well layers 5, M groups of multiple quantum well layers 5 in the resonant cavity layer are integrated in a small space, which can effectively increase the optical power density and thus improve the optical power. Therefore, when there are three groups of multiple quantum well layers 5, there are two tunnel junctions 7 for connecting the three groups of multiple quantum well layers 5; and when there are M groups of multiple quantum well layers 5, there are M-1 tunnel junctions 7 for connecting the M groups of multiple quantum well layers 5.

[0050] Specifically, the N-type DBR reflection layer 3 and the P-type DBR reflection layer 8 each include high-refractive thin films and low-refractive thin films, which are arranged alternately. Adjacent high-refractive thin film 31 and low-refractive thin film 32 constitute a period. It should be noted that the thickness of each film layer of the N-type DBR reflection layer 3 and the P-type DBR reflection layer 8 is 1 / 4n (n is the refractive index of the film layer material) of the reflection center wavelength; at the same time, the number of periods of the N-type DBR reflection layer 3 and the P-type DBR reflection layer 8 is not limited in the embodiment.

[0051] For example, the N-type DBR reflection layer 3 and the P-type DBR reflection layer 8 can be (Al z Ga 1-z ) x In 1-x P / Al y Ga 1-y As thin films, where 0 0.4 Ga 0.6 ) 0.5 In 0.5 P / Al 0.5 Ga 0.5 As thin films.

[0052] In order to ensure the gain of the resonant cavity, the number of periods of the N-type DBR reflection layer 3 should meet the requirement of high reflectivity. Moreover, in order to ensure that the emitted laser has a narrow linewidth, after the light is reflected by the N-type DBR reflection layer 3, a standing wave is formed in the resonant cavity. Therefore, the reflectivity of the N-type DBR reflection layer 3 needs to be set according to the preset requirement, which is not limited in the embodiment.

[0053] Further, based on the above-mentioned embodiment of the application, in order to realize carrier conversion, the P-type layer 7b and the N-type layer 7a are each a heavily doped layer, that is, the doping concentration in the P-type layer 7b and the N-type layer 7a is relatively high. In an embodiment of the application, the material of at least one heavily doped layer of the P-type layer 7b and the N-type layer 7a is one of GaAs and AlGaAs, so as to be close to the material of the DBR mirror, thereby ensuring the material growth quality. Alternatively, the doping ion of the N-type layer 7a is Si or Te; the doping ion of the P-type layer 7b is C, which is not limited in the embodiment.

[0054] Further, based on the above-mentioned embodiment of the present application, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position along the first direction. Specifically, the interface between the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0055] Further, based on the above-mentioned embodiment of the present application, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position along the first direction. Specifically, the interface between the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0056] Further, based on the above-mentioned embodiment of the present application, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position along the first direction. Specifically, the interface between the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0057] It should be noted that, on the side of the multi-quantum well layer 5 facing the P-type DBR reflection layer 8, a restriction layer is arranged between the multi-quantum well layer 5 and the oxidation layer 6.

[0058] Further, based on the above-mentioned embodiment of the present application, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position along the first direction. Specifically, the interface between the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0059] Further, based on the above-mentioned embodiment of the present application, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position along the first direction. Specifically, the interface between the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0060] In combination with the above-mentioned content, as shown in Figure 1 The present embodiment further provides a multi-junction vertical cavity surface emitting laser, when M=3, comprising:

[0061] a GaAs substrate 1;

[0062] A buffer layer 2, an N-type DBR reflective layer 3, a first confinement layer 41, a first group of multiple quantum well layers 51, a second confinement layer 42, a first oxide layer 61, a first tunnel junction 71, a third confinement layer 43, a second group of multiple quantum well layers 52, a fourth confinement layer 44, a second oxide layer 62, a second tunnel junction 72, a fifth confinement layer 45, a third group of multiple quantum well layers 53, a sixth confinement layer 46, a third oxide layer 63, a P-type DBR reflective layer 8, and an ohmic contact layer 9 are stacked sequentially along the surface of the GaAs substrate 1.

[0063] Specifically, the buffer layer 2 is a GaAs buffer layer 2.

[0064] Specifically, such as Figure 2 As shown, the N-type DBR reflective layer 3 consists of alternating high-refractive-index thin films 31 and low-refractive-index thin films 32, specifically (Al... z Ga 1-z ) x In 1-x P / Al y Ga 1-y As a thin film, where 0 < x ≤ 1, 0 ≤ y < 1, and the values ​​of x and y can be different; and the thickness of each film layer is 1 / 4n of the reflection center wavelength (n is the refractive index of the film layer material). The number of periods of the N-type DBR reflective layer 3 should meet the requirement of high reflectivity. Moreover, in order to ensure that the emitted laser has a narrow linewidth, the light is reflected by the N-type DBR reflective layer 3 and forms a standing wave in the resonant cavity. Therefore, the reflectivity of the N-type DBR reflective layer 3 needs to be set according to preset requirements, which is not limited in this embodiment.

[0065] Specifically, in one embodiment of the present invention, the first confinement layer 41 and the second confinement layer 42 are made of AlGaInP.

[0066] Specifically, the first group of multiple quantum well layers 51 is disposed at the antinode of the first standing wave, and the maximum laser gain is obtained through the electric field intensity at the antinode. For example... Figure 3 As shown, the first group of multiple quantum well layers 51 includes alternately stacked well layers 5a and barrier layers 5b. Specifically, the first group of multiple quantum well layers 51 is an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure. That is, in one embodiment of the present invention, well layer 5a includes an InGaAs layer, and barrier layer 5b includes an AlGaAs layer or GaAsP. In other embodiments of the present invention, well layer 5a may include an InAlGaAs layer, and barrier layer 5b may include an AlGaAsP barrier layer. Meanwhile, the number of alternation periods of well layer 5a and barrier layer 5b is set according to preset requirements, and the present invention does not limit this.

[0067] Specifically, the first oxide layer 61 can be formed by oxidizing a semiconductor compound. The oxidized semiconductor compound forms the insulating region to achieve current limiting, while the unoxidized semiconductor compound forms the conductive region. This embodiment does not limit the oxide layer 6. For example, in some embodiments, the material of the conductive region of the first oxide layer 61 is aluminum gallium arsenide (AlGaAs); the material of the insulating region of the first oxide layer 61 is aluminum oxide (Al2O3) or aluminum gallium oxide.

[0068] Specifically, such as Figure 4 As shown, the first tunneling junction 71 is disposed at the node position of the first standing wave, and the first tunneling junction 71 includes an N-type layer 7a and a P-type layer 7b sequentially stacked along a first direction. The first tunneling junction 71 reduces the light absorption of the P-type layer 7b by distributing at least a portion of the P-type layer 7b at the node position. To achieve carrier conversion, both the P-type layer 7b and the N-type layer 7a are heavily doped layers, meaning the doping concentration in the P-type layer 7b and the N-type layer 7a is quite high. In one embodiment of the present invention, the material of at least one heavily doped layer in the P-type layer 7b and the N-type layer 7a is one of GaAs and AlGaAs, thereby being close to the DBR mirror material to ensure material growth quality. Optionally, the dopant ions of the N-type layer 7a are Si or Te; the dopant ions of the P-type layer 7b are C, which is not limited in this embodiment.

[0069] Furthermore, along the first direction, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the node position. Specifically, the interface between the N-type layer 7a and the P-type layer 7b is deviated from the node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0070] Specifically, in one embodiment of the present invention, the third confinement layer 43 and the fourth confinement layer 44 are made of AlGaInP.

[0071] Specifically, the second set of multiple quantum well layers 52 is disposed at the antinodes of the second standing wave, and the maximum laser gain is obtained through the electric field intensity at the antinodes. Figure 3As shown, the second group of multiple quantum well layers 51 includes alternately stacked well layers 5a and barrier layers 5b. Specifically, the second group of multiple quantum well layers 52 is an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure. That is, in one embodiment of the present invention, well layer 5a includes an InGaAs layer, and barrier layer 5b includes an AlGaAs layer or GaAsP. In other embodiments of the present invention, well layer 5a may include an InAlGaAs layer, and barrier layer 5b may include an AlGaAsP barrier layer. Meanwhile, the number of alternation periods of well layer 5a and barrier layer 5b is set according to preset requirements, and the present invention does not limit this.

[0072] Specifically, the second oxide layer 62 can be formed by oxidizing a semiconductor compound. The oxidized semiconductor compound forms the insulating region (not shown in the figure) to achieve current limiting, while the unoxidized semiconductor compound forms the conductive region (not shown in the figure). This embodiment does not limit the oxide layer 6. For example, in some embodiments, the material of the conductive region of the second oxide layer 62 is aluminum gallium arsenide (AlGaAs); the material of the insulating region of the second oxide layer 62 is aluminum oxide (Al2O3) or aluminum gallium oxide.

[0073] Specifically, such as Figure 4 As shown, the second tunneling junction 72 is disposed at the node position of the second standing wave, and the second tunneling junction 72 includes an N-type layer 7a and a P-type layer 7b sequentially stacked along a first direction. The second tunneling junction 72 reduces the light absorption of the P-type layer 7b by distributing at least a portion of the P-type layer 7b at the node position. To achieve carrier conversion, both the P-type layer 7b and the N-type layer 7a are heavily doped layers, meaning the doping concentration in the P-type layer 7b and the N-type layer 7a is quite high. In one embodiment of the present invention, the material of at least one heavily doped layer in the P-type layer 7b and the N-type layer 7a is one of GaAs and AlGaAs, thereby being close to the DBR mirror material to ensure material growth quality. Optionally, the dopant ions of the N-type layer 7a are Si or Te; the dopant ions of the P-type layer 7b are C, which is not limited in this embodiment.

[0074] Furthermore, along the first direction, the interface between the N-type layer 7a and the P-type layer 7b has a deviation distance from the node position. Specifically, the interface between the N-type layer 7a and the P-type layer 7b is deviated from the node position along one side of the substrate 1; and the value of the deviation distance is not greater than the thickness value of the P-type layer 7b.

[0075] Specifically, in one embodiment of the present invention, the fifth confinement layer 45 and the sixth confinement layer 46 are made of AlGaInP.

[0076] Specifically, the third set of multiple quantum well layers 53 is disposed at the antinode of the third standing wave, and the maximum laser gain is obtained through the electric field intensity at the antinode. For example... Figure 3 As shown, the third group of multiple quantum well layers 51 includes alternately stacked well layers 5a and barrier layers 5b. Specifically, the third group of multiple quantum well layers 53 is an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure. That is, in one embodiment of the present invention, well layer 5a includes an InGaAs layer, and barrier layer 5b includes an AlGaAs layer or GaAsP. In other embodiments of the present invention, well layer 5a may include an InAlGaAs layer, and barrier layer 5b may include an AlGaAsP barrier layer. Meanwhile, the number of alternation periods of well layer 5a and barrier layer 5b is set according to preset requirements, and the present invention does not limit this.

[0077] Specifically, the third oxide layer 63 can be formed by oxidizing a semiconductor compound. The oxidized semiconductor compound forms the insulating region to achieve current limiting, while the unoxidized semiconductor compound forms the conductive region. This embodiment does not limit the oxide layer 6. For example, in some embodiments, the material of the conductive region of the third oxide layer 63 is aluminum gallium arsenide (AlGaAs); the material of the insulating region of the third oxide layer 63 is aluminum oxide (Al2O3) or aluminum gallium oxide.

[0078] Specifically, such as Figure 5 As shown, the P-type DBR reflective layer 8 consists of alternating high-refractive-index thin films 81 and low-refractive-index thin films 82, specifically (Al... z Ga 1-z ) x In 1-x P / Al y Ga 1-y As a thin film, where 0 < x ≤ 1, 0 ≤ y < 1, and the values ​​of x and y can be different; and the thickness of each film layer is 1 / 4n of the reflection center wavelength (n is the refractive index of the film layer material).

[0079] As can be seen from the above technical solution, the multi-junction vertical cavity surface-emitting laser provided by the present invention has a tunnel junction 7 between two adjacent multi-quantum well layers 5 in the resonant cavity layer; wherein, the multi-quantum well layer 5 is disposed at the antinode of the standing wave, and the maximum laser gain effect is obtained by the electric field intensity at the antinode; at least a portion of the tunnel junction 7 is disposed at the node of the standing wave, and it includes an N-type layer 7a and a P-type layer 7b stacked sequentially along a first direction, and the tunnel junction 7 reduces the light absorption of the P-type layer 7b by distributing at least a portion of the P-type layer 7b at the node.

[0080] Secondly, the interface of the N-type layer 7a and the P-type layer 7b has a deviation distance from the wave node position, and further, the interface of the N-type layer 7a and the P-type layer 7b deviates from the wave node position along one side of the substrate 1. In this way, the P-type layer 7b can be arranged more on the adjacent position of the wave node, so as to reduce the light absorption of the P-type layer 7b, and improve the electro-optical conversion efficiency of the whole vertical cavity surface emitting laser.

[0081] Finally, in a preferred scheme of the present application, the value of the deviation distance is not greater than the thickness value of the P-type layer 7b, so as to maximize the arrangement of the P-type layer 7b on both sides of the wave node position, so as to reduce the light absorption of the P-type layer 7b to the limit, and better improve the electro-optical conversion efficiency of the whole vertical cavity surface emitting laser.

[0082] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0083] It should also be noted that the relationship terms such as first and second, etc. used in this paper are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between the entities or operations. Moreover, the term "includes", "contains" or any other variant thereof is intended to cover non-exclusive inclusion, so that the article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such article or device. Without more limitations, the element defined by the statement "includes a" does not exclude the presence of another identical element in the article or device including the above element.

[0084] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-junction vertical-cavity surface-emitting laser, characterized in that, include: A substrate and an N-type DBR reflective layer, a resonant cavity layer, and a P-type DBR reflective layer stacked sequentially along the surface of the substrate; The resonant cavity layer forms a standing wave through resonance, which includes several sets of multiple quantum well layers and a tunneling junction disposed between two adjacent sets of multiple quantum well layers; wherein, the tunneling junction includes N-type layers and P-type layers stacked sequentially along a first direction, and at least a portion of the tunneling junction is disposed at the node position of the standing wave, so that the tunneling junction reduces the light absorption of the P-type layer by distributing at least a portion of the P-type layer at the node position; Along the first direction, the interface between the N-type layer and the P-type layer has a deviation distance from the node position.

2. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, The interface between the N-type layer and the P-type layer is offset from the position of the node along one side of the substrate.

3. The multi-junction vertical-cavity surface-emitting laser according to claim 2, characterized in that, The deviation distance is not greater than the thickness of the P-type layer.

4. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, An oxide layer is provided on the side of each of the multiple quantum well layers facing the P-type DBR reflective layer.

5. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, The substrate includes a GaAs substrate.

6. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, Each group of multiple quantum well layers contains several quantum well layers and several quantum barrier layers.

7. The multi-junction vertical-cavity surface-emitting laser according to claim 6, characterized in that, The multiple quantum well layer includes an InGaAs / AlGaAs quantum well structure or an InGaAs / GaAsP quantum well structure.

8. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, An ohmic contact layer is provided on the surface of the P-type DBR reflective layer facing away from the substrate.

9. The multi-junction vertical-cavity surface-emitting laser according to claim 1, characterized in that, The multiple quantum well layer is disposed at the antinode of the standing wave, and the maximum laser gain is obtained by the electric field intensity at the antinode.

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