A vertical cavity surface emitting laser epitaxial structure

Abstract

The application discloses a vertical cavity surface emitting laser epitaxial structure. The epitaxial structure comprises, from bottom to top, a substrate, a buffer layer, a first high-refractive-index-difference AlGaAs DBR layer, a first low-refractive-index-difference AlGaAs DBR layer, a lower AlGaAsP transition layer, a lower AlGaInP DBR layer, a lower AlGaInP barrier layer, a GaInP / AlGaInP multi-quantum-well barrier layer, an upper AlGaInP barrier layer, an upper AlGaInP DBR layer, an upper AlGaAsP transition layer, a second low-refractive-index-difference AlGaAs DBR layer, a second high-refractive-index-difference AlGaAs DBR layer and a GaAs cap layer. The application simultaneously utilizes AlGaAsP transition layers, reduces dislocation defects introduced at an active region interface and realizes high-efficiency and stable working of a 650 nm VSCEL by combining DBR, segmented doping and P-DBR component gradual change.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to an epitaxial structure for a vertical cavity surface-emitting laser. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Plastic optical fiber, with its low cost, large core radius, and ease of assembly and operation, is replacing silica optical fiber in short-range optical fiber communication, becoming the "last mile" of fiber optic communication. Plastic optical fiber exhibits a minimum loss window around 650nm wavelength. Compared to conventional edge-emitting semiconductor lasers, vertical-cavity surface-emitting lasers (VCSELs) have optical resonators perpendicular to the semiconductor chip substrate, enabling laser emission from the chip surface. The uniform circular beam significantly reduces the complexity of the optical field and lowers subsequent application costs. VCSELs offer advantages such as low threshold current, stable single-wavelength operation, easy two-dimensional integration, no cavity threshold damage, circular symmetrical spot size, and high fiber coupling efficiency. Therefore, 650nm VCSELs have strong application prospects.

[0004] Currently, most commercially available VSCEL devices are concentrated in the 808-1550nm band. The application research of 650nm VSCEL is more difficult. The reasons are as follows: (1) Due to the absorption loss in the 650nm band, the Al composition in AlGaAs DBR is limited to the range of 0.5-1.0, resulting in a large thermal resistance. In particular, due to the large effective hole mass of P-type DBR, the homo-heterojunction forms a high series resistance at a large potential barrier. (2) The light-emitting region of 650nm VSCEL is mainly composed of AlGaInP material. Due to the difference in lattice constant and thermal expansion coefficient of AlGaAs / AlGaInP, the surface segregation of In atoms in the crystal growth direction will cause the concentration of In atoms on the crystal surface to be greater than that on the lower surface and inside the crystal, which will increase the surface roughness and cause the growth mode to change from two-dimensional to three-dimensional island growth mode. The growth interface is prone to island growth, high dislocation, and high defect level, which seriously affects the photoelectric characteristics of the laser. In particular, the roughening of the surface morphology of the FP resonator leads to increased light absorption and reduced efficiency. Summary of the Invention

[0005] This invention provides an epitaxial structure for a vertical-cavity surface-emitting laser (VSCEL), which effectively overcomes many defects of 650nm VSCELs through the design of the VSCEL structure and composition, thus promoting the practical application of 650nm VSCELs. To achieve the above objective, this invention discloses the following technical solution.

[0006] An epitaxial structure for a vertical-cavity surface-emitting laser (VCSEL) comprises, from bottom to top: a substrate 1, a buffer layer 2, a first high refractive index difference AlGaAs DBR layer 3, a first low refractive index difference AlGaAs DBR layer 4, a lower AlGaAsP transition layer 5, a lower AlGaInP DBR layer 6, a lower AlGaInP barrier layer 7, a GaInP / AlGaInP multiple quantum well barrier layer 8, an upper AlGaInP barrier layer 9, an upper AlGaInP DBR layer 10, an upper AlGaAsP transition layer 11, a second low refractive index difference AlGaAs DBR layer 12, a second high refractive index difference AlGaAs DBR layer 13, and a GaAs cap layer 14. Wherein:

[0007] The first high refractive index difference AlGaAs DBR layer 3 consists of alternating Al layers from bottom to top. x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 The As layer has x1 ≤ 1 and x2 ≤ 0.3. The greater the refractive index difference of the DBR layer 3, the easier it is to obtain a high-reflectivity DBR.

[0008] The first low refractive index difference AlGaAs DBR layer 4 consists of alternating Al layers from bottom to top. x3 Ga 1-x3 As layer, Al x4 Ga 1-x4 An As layer, wherein 0.9 ≤ x3 ≤ 1 and 0.5 ≤ x4 ≤ 0.7. This DBR layer of the present invention can effectively reduce 650nm light absorption loss.

[0009] The composition of the lower AlGaAsP transition layer 5 is Al x7 Ga 1-x7 As y3 P 1-y3 Wherein, 0.5≤x7≤0.7 and 0.85≤y3≤0.99. This lower AlGaAsP transition layer 5 of the present invention can achieve the switching from an As atmosphere in AlGaAs to a P atmosphere in AlGaInP, avoiding disordered phases at the interface, reducing the defect density in the active region, and improving reliability.

[0010] The lower AlGaInP DBR layer 6 consists of alternating layers of Al from bottom to top. x5 Ga 1-x5 ) y1 In 1-y1 P layer and (Al) x6 Ga 1-x6 ) y2 In 1-y2Layer P has 5-15 pairs of values. Specifically, 0.9 ≤ x5 ≤ 1, 0.4 ≤ y1 ≤ 0.6, 0 ≤ x6 ≤ 0.3, and 0.4 ≤ y2 ≤ 0.6. Optionally, the (Al) x5 Ga 1-x5 ) y1 In 1-y1 P layer, (Al) x6 Ga 1-x6 ) y2 In 1-y2 The thickness of P is λ / 4n, where n is the 650nm wavelength optical refractive index of the corresponding material layer, and λ is the wavelength of the corresponding material layer. This invention effectively avoids the problem of As / P complex formation at the active region interface when directly growing the AlGaInP active region after AlGaAs DBR, thus avoiding any impact on the reliability of the laser device.

[0011] In the lower AlGaInP DBR layer 6, the Al composition is gradually grown by utilizing the changes in TMAl and TMGa flow rates. Different Al compositions are grown by the gradient layer, which has a thickness of 10-30 nm, thus reducing the difference in barrier height between different materials.

[0012] The material of the lower AlGaInP barrier layer 7 is (Al x8 Ga 1-x8 ) y4 In 1-y4 P, where 0.4 ≤ x8 ≤ 0.7 and 0.4 ≤ y4 ≤ 0.6. Optionally, the thickness of the lower AlGaInP barrier layer 7 is less than λ / 4, where λ is the quantum well emission wavelength. This invention utilizes the lower AlGaInP barrier layer 7 combined with multiple quantum well barriers to form a resonant cavity.

[0013] The GaInP / AlGaInP multiple quantum well barrier 8 has alternating Ga elements from bottom to top. x10 In 1-x10 P layer, (Al) x9 Ga 1-x9 ) y5 In 1-y5 The P-layer has the following properties: 0.4 ≤ x10 ≤ 0.5, 0.1 ≤ x9 ≤ 0.5, and 0.4 ≤ y5 ≤ 0.6. Optionally, the total thickness of the GaInP / AlGaInP multiple quantum well barrier 8 is less than λ / 4, where λ is the wavelength of the multiple quantum well barrier 8. The GaInP / AlGaInP multiple quantum well barrier 8 of the present invention has a lasing wavelength of 650 nm, which can form a resonant cavity with the lower AlGaInP barrier layer 7 to achieve barrier layer strain compensation, reduce stress accumulation in the active region, improve threshold gain, and reduce the generation of defects such as dislocations.

[0014] The upper AlGaInP DBR layer 10 is the same as the lower AlGaInP DBR layer 6. The upper AlGaAsP transition layer 11 is the same as the lower AlGaAsP transition layer 5. The second low refractive index difference AlGaAs DBR layer 12 is the same as the first low refractive index difference AlGaAs DBR layer 4. The second high refractive index difference AlGaAs DBR layer 13 is the same as the first high refractive index difference AlGaAs DBR layer 3.

[0015] Furthermore, the buffer layer 2 is doped with Si atoms. Preferably, the doping concentration is 2E18-7E18 atoms / cm³. 3 The thickness of the GaAs buffer layer 2 is 0.1-0.5 μm.

[0016] Furthermore, the first high refractive index difference AlGaAs DBR layer 3 is doped with Si atoms. Preferably, the doping concentration is 1E18-7E18 atoms / cm³. 3 Al x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 The number of As layers ranges from 3 to 15 pairs. High doping levels help reduce the barrier height difference and decrease resistance.

[0017] Furthermore, the first low refractive index difference AlGaAs DBR layer 4 is doped with Si atoms. Preferably, the doping concentration is 1E18-7E18 atoms / cm³. 3 The number of pairs is 20-35. High doping helps to reduce the barrier height difference and decrease resistance.

[0018] Furthermore, the lower AlGaAsP transition layer 5 is doped with Si atoms. Preferably, the doping concentration is 1E18-7E18 atoms / cm³. 3 .

[0019] Furthermore, the lower AlGaInP DBR layer 6 is doped with Si atoms. Preferably, the doping concentration is 2E17-1E18 / cm³. 3 The number of pairs is 5-15. The lower AlGaInP DBR layer 6 is close to the active region, and the use of low doping helps to reduce absorption loss and avoids the increase in threshold current and decrease in slope efficiency caused by dopant diffusion.

[0020] Furthermore, the thickness of the lower AlGaInP barrier layer 7 is 50-150 nm.

[0021] Furthermore, the GaInP / AlGaInP multi-quantum-well barrier layer 8 has a well width thickness of 3-7 nm. Preferably, the thickness of the multi-quantum-well barrier layer 8 is 4-8 nm.

[0022] Furthermore, the thickness of the upper AlGaInP barrier layer 9 is 50-150 nm.

[0023] Furthermore, the upper AlGaInP DBR layer 10 is doped with Mg atoms. Preferably, the doping concentration is 2E17-1E18 / cm³. 3 The number of pairs is 5-15. The upper AlGaInP DBR layer 10 is close to the active region, and the use of low doping is beneficial to reduce absorption loss and avoid the increase in threshold current and decrease in slope efficiency caused by dopant diffusion.

[0024] Furthermore, the upper AlGaAsP transition layer 11 is doped with Mg atoms. Preferably, the doping concentration is 7E17-5E18 / cm³. 3 .

[0025] Furthermore, the second low refractive index difference AlGaAs DBR layer 12 is doped with C atoms. Preferably, the doping concentration is 7E17-5E18 atoms / cm³. 3 The number of pairs is 15-30.

[0026] Furthermore, the second high refractive index difference AlGaAs DBR layer 13 is doped with C atoms. Preferably, the doping concentration is 7E17-5E18 atoms / cm³. 3 The number of pairs is 3-10.

[0027] Furthermore, the cap layer 14 is doped with Zn atoms. Preferably, the doping concentration is 3E19-7E19 atoms / cm³. 3 Optionally, the thickness of the cap layer 14 is 0.1-0.5 μm.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) This invention utilizes Al x15 Ga 1-x15 As、Al x16 Ga 1-x16 As-based low refractive index difference DBR, Al x17 Ga 1-x17 As、Al x18 Ga 1-x18 High refractive index difference DBR composed of As is used to reduce abrupt changes in the potential barrier and lower the series resistance of P-DBR.

[0030] (2) This invention combines high refractive index difference DBR, low refractive index difference DBR, and AlGaInP DBR. That is, the high refractive index difference material is used at the far end to reduce thermal resistance, the low refractive index difference AlGaAs / AlGaAs DBR is used in the middle section, which can effectively reduce the absorption loss of 650nm light, and the AlGaInP / AlGaInP DBR is used at the near end to effectively reduce the island dislocations formed with the AlGaInP active region, so as to achieve efficient and stable operation of 650nm vertical cavity surface emission laser.

[0031] (3) The present invention uses AlGaAsP as a transition layer, which can effectively suppress the surface roughness and increase the number of defects caused by In segregation at the AlGaAs and AlGaInP interface.

[0032] (4) The high doping of the lower AlGaInP DBR layer in this invention helps to reduce the barrier height, reduce the series resistance, and improve the carrier mobility. The low doping of the upper AlGaInP DBR layer reduces absorption loss and improves conversion efficiency. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a schematic diagram of the epitaxial structure of the vertical cavity surface-emitting laser prepared in Embodiment 1 of the present invention.

[0035] Figure 2 This is a light spot diagram of the epitaxial structure of the vertical cavity surface-emitting laser prepared in Embodiment 1 of the present invention.

[0036] Figure 3 This is a pattern of the epitaxial structure of a conventional side-emitting laser.

[0037] Figure 4 This is a PIV curve of the vertical cavity surface-emitting laser epitaxial structure prepared in Embodiment 1 of the present invention.

[0038] Figure 5 This is a PIV curve diagram of an existing conventional side-emitting laser epitaxial structure.

[0039] The numbers represent: 1-GaAs substrate, 2-GaAs buffer layer, 3-first high refractive index difference AlGaAs DBR layer, 4-first low refractive index difference AlGaAs DBR layer, 5-lower AlGaAsP transition layer, 6-lower AlGaInP DBR layer, 7-lower AlGaInP barrier layer, 8-GaInP / AlGaInP multiple quantum well barrier layer, 9-upper AlGaInP barrier layer, 10-upper AlGaInP DBR layer, 11-upper AlGaAsP transition layer, 12-second low refractive index difference AlGaAs DBR layer, 13-second high refractive index difference AlGaAs DBR layer, 14-GaAs cap layer. Detailed Implementation

[0040] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves. They do not limit the structure and are merely for the purpose of facilitating the description of this invention and simplifying the description. They do not indicate or imply that the device or component referred to needs to have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods or product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0043] In the following examples, the purity of AsH3 and PH3 was ≥99.9999%. The purity of other raw materials was 99.99995%.

[0044] Example 1

[0045] An epitaxial structure of a vertical-cavity surface-emitting laser (VSCEL) (reference) Figure 1 The preparation method of ) includes the following steps:

[0046] S1. Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 740℃ for baking, and introduce AsH3 to perform surface heat treatment on the GaAs substrate.

[0047] S2, the temperature is slowly reduced to 680℃ at a rate not exceeding 30℃ / min, and TMGa and AsH3 are continuously introduced to grow a GaAs buffer layer 2 on the GaAs substrate 1. The doping source of the GaAs buffer layer 2 is Si2H6, and the doping concentration is 5E18 atoms / cm³. 3 The GaAs buffer layer has a thickness of 0.3 μm. The purpose of the GaAs buffer layer 2 is to prevent defects from propagating from the substrate into the confinement layer, provide a fresh growth interface, and improve the material growth quality.

[0048] S3, the temperature is slowly increased to 730℃, with a heating rate not exceeding 50℃ / min, and TMAl, TMGa, and AsH3 are continuously introduced to grow the first high refractive index difference AlGaAs DBR layer 3 on the GaAs buffer layer 2. The first high refractive index difference AlGaAs DBR layer 3 consists of alternating layers of Al with a thickness of 42.7 nm distributed from bottom to top. x1 Ga 1-x1 As layer, 50.8nm Al x2 Ga 1-x2 In the As layer, x1 = 0.98, x2 = 0.05, and Al... x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 The doping source for the As layer is Si₂H₆, and the doping concentration is 3E¹⁸ atoms / cm². 3 There are 5 pairs. The high refractive index of the first high refractive index difference AlGaAs DBR layer 3 is used to improve reflectivity.

[0049] S4, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a first low refractive index difference AlGaAs DBR layer 4 on the first high refractive index difference AlGaAs DBR layer 3. The first low refractive index difference AlGaAs DBR layer 4 consists of alternating layers of Al with a thickness of 42.7 nm distributed from bottom to top. x3 Ga 1-x3 As, 42.7nm Al x4 Ga 1-x4 The composition is As, with x3 = 0.98 and x4 = 0.5. The doping source for the first low refractive index difference AlGaAs DBR layer 4 is Si2H6, and the doping concentration is 3E18 atoms / cm³. 3 The number of pairs is 30. Using a first low refractive index difference AlGaAs DBR layer 4 with an Al composition greater than 0.5 can effectively reduce the absorption loss of 650nm light.

[0050] S5, the temperature is gradually reduced to 640℃ at a cooling rate not exceeding 50℃ / min. TMAl, TMGa, AsH3, and PH3 are continuously introduced to grow a lower AlGaAsP transition layer 5 with a thickness of 23.7 nm on the first low refractive index difference AlGaAs DBR layer 4. The composition of the lower AlGaAsP transition layer 5 is Al... x7 Ga 1-x7 As y3 P 1-y3 The values ​​are x7 = 0.5 and y3 = 0.9. The doping source for the lower AlGaAsP transition layer 5 is Si2H6, with a doping concentration of 3E18 atoms / cm³. 3 The AlGaAsP transition layer 5 is used to achieve As / P composition switching, avoiding the formation of AsP complexes at the active region interface, which would affect surface roughness and device reliability.

[0051] S6, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP DBR layer 6 on the lower AlGaAsP transition layer 5. The lower AlGaInP DBR layer 6 consists of alternating layers of Al(Al) with a thickness of 47.9 nm distributed from bottom to top. x5 Ga 1-x5 ) y1 In 1-y1 P-layer, 54.6nm (Al) x6 Ga1-x6) y2 In 1-y2 In the P-layer, x5 = 0.95, y1 = 0.5, x6 = 0.1, and y2 = 0.5. The doping source for the lower AlGaInP DBR layer 6 is Si2H6, with a doping concentration of 4E17 atoms / cm³. 3 The number of pairs is 7. The AlGaInP DBR layer 6 described above can effectively reduce Al... x4 Ga 1-x4 As DBR and active region (Al) x8 Ga 1-x8 ) y4 In 1-y4 The interface dislocations formed during the bonding of the P-barrier layer improve the reliability of the laser.

[0052] S7, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP barrier layer 7 with a thickness of 77.5 nm on the lower AlGaInP DBR layer 6. The composition of the lower AlGaInP barrier layer 7 is (Al... x8 Ga 1-x8 ) y4 In 1-y4P, where x8 = 0.45, y4 = 0.5, and the lower AlGaInP barrier layer 7 is unintentionally doped. This lower AlGaInP barrier layer 7 provides a resonant cavity for the active region light, enabling photolasing.

[0053] S8, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a 5nm thick GaInP / AlGaInP multiple quantum well barrier layer 8 on the lower AlGaInP barrier layer 7. The GaInP / AlGaInP multiple quantum well barrier layer 8 consists of alternating Ga atoms from bottom to top. x10 In 1-x10 P layer, (Al) x9 Ga 1-x9 ) y5 In 1-y5 The P-layer has x10 = 0.46, x9 = 0.2, and y4 = 0.5. The GaInP / AlGaInP multi-quantum-well barrier layer 8 has a well width of 4 nm and an emission wavelength of 650 nm, and is unintentionally doped. This GaInP / AlGaInP multi-quantum-well barrier layer 8 enables 650 nm photoluminescence while simultaneously suppressing carrier overflow and confining the light field.

[0054] S9, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP barrier layer 9 with a thickness of 77.5 nm on the GaInP / AlGaInP multi-quantum-well barrier layer 8. The composition of the upper AlGaInP barrier layer 9 is (Al... x11 Ga 1-x11 ) y6 In 1-y6 P, where x11 = 0.45 and y6 = 0.5, is unintentionally doped. This AlGaInP barrier layer 9 provides a resonant cavity for the active region light, enabling photolasing.

[0055] S10, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP DBR layer 10 on the upper AlGaInP barrier layer 9. The upper AlGaInP DBR layer 10 consists of alternating layers of Al₂O₃ with a thickness of 47.9 nm, distributed from bottom to top. x12 Ga 1-x12 ) y7 In 1-y7 P-layer, 54.6nm (Al) x13 Ga 1-x13 ) y8 In 1-y8 The P-layer. The doping source of the upper AlGaInP DBR layer 10 is Cp2Mg, and the doping concentration is 4E17 atoms / cm³. 3The number of pairs is 7. This AlGaInP DBR layer 10 achieves a reduction in DBR Al x15 Ga 1-x15 As and the active region (Al) x11 Ga 1-x11 ) y6 In 1-y6 The purpose of forming island-like dislocations in the P-barrier layer is to effectively improve the reliability of VSCEL.

[0056] S11, the temperature is gradually increased to 730℃, and TMAl, TMGa, AsH3, and PH3 are continuously introduced to grow an upper AlGaAsP transition layer 11 with a thickness of 23.7 nm on the upper AlGaInP DBR layer 10. The upper AlGaAsP transition layer 11 is composed of Al x14 Ga 1-x14 As y9 P 1-y9 x14 = 0.5, y9 = 0.9. The doping source for the upper AlGaAsP transition layer 11 is Cp2Mg, and the doping concentration is 1E18 atoms / cm³. 3 The DBR (AlGaAsP) transition layer 11 was implemented through the aforementioned AlGaAsP transition layer 11. x13 Ga 1-x13 ) y8 In 1-y8 P and DBRAl x15 Ga 1-x15 As / P component switching in As avoids the need for As / P component switching in the active region (Al) x11 Ga 1-x11 ) y6 In 1-y6 P-barrier layer and DBRAl x15 Ga 1-x15 The problem of AsP complexes forming at the As interface affecting surface roughness and device reliability.

[0057] S12, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second low refractive index difference AlGaAs DBR layer 12 on the upper AlGaAsP transition layer 11. The second low refractive index difference AlGaAs DBR layer 12 consists of alternating Al atoms from bottom to top. x15 Ga 1-x15 As layer, Al x16 Ga 1-x16 In layer As, x15 = 0.98 and x16 = 0.5. Al x15 Ga 1-x15 The As layer thickness is 42.7 nm, and the Al layer thickness is... x16 Ga 1-x16 The As layer has a thickness of 46.8 nm, wherein the Al15 Ga 1-x15 As layer changes to Al x16 Ga 1-x16 In the As layer, the Al composition of the gradient layer between the two layers gradually changes from 0.98 to 0.5, and the thickness of this gradient layer is 21.4 nm. x16 Ga 1-x16 As layer gradually transitions to Al. x15 Ga 1-x15 In the As layer, the Al composition in the gradient layer between the two layers gradually changes from 0.5 to 0.98, and the thickness of this gradient layer is 23.4 nm. The doping source of the second low refractive index difference AlGaAs DBR layer 12 is C, and the doping concentration is 2E18 atoms / cm³. 3 There are 26 pairs. The Al... x15 Ga 1-x15 As layer and Al x16 Ga 1-x16 The presence of an Al content greater than 0.5 in the As layer helps reduce losses caused by the absorption of 650nm light into the quantum well.

[0058] S13, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second high refractive index difference AlGaAs DBR layer 13 on the second low refractive index difference AlGaAs DBR layer 12. The second high refractive index difference AlGaAs DBR layer 13 consists of alternating Al atoms from bottom to top. x17 Ga 1-x17 As layer, Al x18 Ga 1-x18 In the As layer, x17 = 0.98 and x18 = 0.05. The second high refractive index difference AlGaAs DBR layer has a C doping source of 13 and a doping concentration of 2E18 atoms / cm³. 3 The number of pairs is 5.5. The Al... x17 Ga 1-x17 The As layer thickness is 42.7 nm, and the Al layer thickness is 42.7 nm. x18 Ga 1-x18 The As layer has a thickness of 50.8 nm and a logarithmic number of 5.5 pairs, of which Al x17 Ga 1-x17 After the As layer has grown, Al x18 Ga 1-x18 Before the As layer grows, first in the Al x17 Ga 1-x17 An Al composition-gradient layer is grown on an As layer, with the Al composition gradient from 0.98 to 0.05, and a thickness of 21.4 nm. x18 Ga 1-x18 After the As layer grows, Al x17 Ga 1- x17Before As layer growth, it was also mentioned in Al x17 Ga 1-x17 An Al composition-gradient layer is grown on the As layer, with the Al composition gradually changing from 0.05 to 0.98, and a thickness of 25.4 nm. x17 Ga 1-x17 As layer, Al x18 Ga 1-x18 When the As layer switches, an Al composition gradient layer is grown between the two layers, and the last Al layer... x17 Ga 1-x17 The As layer is made of AlAs material, and its purpose is to provide a high Al composition region for the wet oxidation process to form the insulating layer. Furthermore, an Al gradient is achieved by adjusting the TMAl flow rate. This second high refractive index difference AlGaAs DBR layer 13 achieves a reflectivity greater than 99.9% at 650 nm on the P-side. Reflectivity is improved by utilizing a high refractive index DBR.

[0059] S14: Stop the flow of TMAl and TMGa, and using the stop growth method, reduce the temperature to 530℃ at a rate not exceeding 50℃ / min. Maintain the temperature at 530℃, and continue to flow TMGa and AsH3 to grow a GaAs cap layer 14 on the second high refractive index difference AlGaAs DBR layer 13. The GaAs cap layer 14 has a thickness of 0.2μm, uses DEZn as the doping source, and has a doping concentration of 4E19 atoms / cm³. 3 After completion, the vertical-cavity surface-emitting laser (VSCEL) epitaxial structure is obtained.

[0060] Example 2

[0061] A method for fabricating an epitaxial structure of a vertical-cavity surface-emitting laser (VSCEL) includes the following steps:

[0062] S1. Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 740℃ for baking, and introduce AsH3 to perform surface heat treatment on the GaAs substrate.

[0063] S2, the temperature is slowly reduced to 680℃ at a rate not exceeding 30℃ / min, and TMGa and AsH3 are continuously introduced to grow a GaAs buffer layer 2 on the GaAs substrate 1. The doping source of the GaAs buffer layer 2 is Si2H6, and the doping concentration is 7E18 atoms / cm³. 3 The GaAs buffer layer has a thickness of 0.1 μm. The purpose of the GaAs buffer layer 2 is to prevent defects from propagating from the substrate into the confinement layer, provide a fresh growth interface, and improve the material growth quality.

[0064] S3, the temperature is slowly increased to 730℃, with a heating rate not exceeding 50℃ / min, and TMAl, TMGa, and AsH3 are continuously introduced to grow the first high refractive index difference AlGaAs DBR layer 3 on the GaAs buffer layer 2. The first high refractive index difference AlGaAs DBR layer 3 consists of alternating layers of Al with a thickness of 50.7 nm distributed from bottom to top. x1 Ga 1-x1 As layer, 42.1nm Al x2 Ga 1-x2 In layer As, x1 = 0.9, x2 = 0, and Al x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 The doping source for the As layer is Si₂H₆, and the doping concentration is 7E¹⁸ atoms / cm². 3 There are 15 pairs. The high refractive index of the first high refractive index difference AlGaAs DBR layer 3 is used to improve reflectivity.

[0065] S4, maintaining the temperature at 730℃, and continuing to introduce TMAl, TMGa, and AsH3 to grow a first low refractive index difference AlGaAs DBR layer 4 on the first high refractive index difference AlGaAs DBR layer 3. The first low refractive index difference AlGaAs DBR layer 4 consists of alternating layers of Al with a thickness of 50.7 nm distributed from bottom to top. x3 Ga 1-x3 As, 46.1nm Al x4 Ga 1-x4 The composition is As, with x3 = 0.9 and x4 = 0.5. The doping source for the first low refractive index difference AlGaAs DBR layer 4 is Si2H6, and the doping concentration is 1E18 atoms / cm³. 3 The number of pairs is 35. Using a first low refractive index difference AlGaAs DBR layer 4 with an Al composition greater than 0.5 can effectively reduce the absorption loss of 650nm light.

[0066] S5, the temperature is gradually reduced to 640℃ at a cooling rate not exceeding 50℃ / min, and TMAl, TMGa, AsH3, and PH3 are continuously introduced to grow a lower AlGaAsP transition layer 5 with a thickness of 25.6 nm on the first low refractive index difference AlGaAs DBR layer 4. The composition of the lower AlGaAsP transition layer 5 is Al x7 Ga 1-x7 As y3 P 1-y3 The values ​​are x7 = 0.7 and y3 = 0.99. The doping source for the lower AlGaAsP transition layer 5 is Si2H6, with a doping concentration of 1E18 atoms / cm³. 3The AlGaAsP transition layer 5 is used to achieve As / P composition switching, avoiding the formation of AsP complexes at the active region interface, which would affect surface roughness and device reliability.

[0067] S6, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP DBR layer 6 on the lower AlGaAsP transition layer 5. The lower AlGaInP DBR layer 6 consists of alternating layers of Al(Al) with a thickness of 53.9 nm distributed from bottom to top. x5 Ga 1-x5 ) y1 In 1-y1 P layer, 47.4nm (Al) x6 Ga1-x6) y2 In 1-y2 In the P-layer, x5 = 0.9, y1 = 0.5, x6 = 0, and y2 = 0.5. The doping source for the lower AlGaInP DBR layer 6 is Si2H6, with a doping concentration of 2E17 atoms / cm³. 3 The number of pairs is 5. The lower AlGaInP DBR layer 6 can effectively reduce the DBR Al x4 Ga 1-x4 As and the active region (Al) x8 Ga 1-x8 ) y4 In 1-y4 The interface dislocations formed during the bonding of the P-barrier layer improve the reliability of the laser.

[0068] S7, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP barrier layer 7 with a thickness of 51.3 nm on the lower AlGaInP DBR layer 6. The composition of the lower AlGaInP barrier layer 7 is (Al... x8 Ga 1-x8 ) y4 In 1-y4 P, where x8 = 0.7, y4 = 0.5, and the lower AlGaInP barrier layer 7 is unintentionally doped. This lower AlGaInP barrier layer 7 provides a resonant cavity for the active region light, enabling photolasing.

[0069] S8, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a GaInP / AlGaInP multiple quantum well barrier layer 8 on the lower AlGaInP barrier layer 7. The GaInP / AlGaInP multiple quantum well barrier layer 8 consists of alternating Ga atoms from bottom to top. x10 In 1-x10 P layer, (Al) x9 Ga 1-x9) y5 In 1-y5 The P-layer has x10 = 0.43, x9 = 0.7, and y4 = 0.5. The GaInP / AlGaInP multi-quantum-well barrier layer 8 has a well width of 3 nm, a barrier layer thickness of 8 nm, and emits light at a wavelength of 650 nm. It is unintentionally doped. This GaInP / AlGaInP multi-quantum-well barrier layer 8 enables 650 nm photoluminescence while simultaneously suppressing carrier overflow and confining the light field.

[0070] S9, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP barrier layer 9 with a thickness of 51.3 nm on the GaInP / AlGaInP multi-quantum-well barrier layer 8. The composition of the upper AlGaInP barrier layer 9 is (Al... x11 Ga 1-x11 ) y6 In 1-y6 P, where x11 = 0.7 and y6 = 0.5, is unintentionally doped. The AlGaInP barrier layer 9 on top provides a resonant cavity for the active region light, enabling photolasing.

[0071] S10, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP DBR layer 10 on the upper AlGaInP barrier layer 9. The upper AlGaInP DBR layer 10 consists of alternating layers of Al₂O₃ with a thickness of 53.9 nm, distributed from bottom to top. x12 Ga 1-x12 ) y7 In 1-y7 P layer, 47.4nm (Al) x13 Ga 1-x13 ) y8 In 1-y8 The P-layer. The doping source of the upper AlGaInP DBR layer 10 is Cp2Mg, and the doping concentration is 2E17 atoms / cm. 3 The number of pairs is 5. This AlGaInP DBR layer 10 achieves a reduction in DBR Al x15 Ga 1-x15 As and AlGaInP active region (Al x11 Ga 1-x11 ) y6 In 1-y6 The purpose of forming island-like dislocations in the P-barrier layer is to effectively improve the reliability of VSCEL.

[0072] S11, gradually reduce the temperature to 730℃, and continue to introduce TMAl, TMGa, and AsH. 3、PH3 was used to grow an upper AlGaAsP transition layer 11 with a thickness of 25.6 nm on the upper AlGaInP DBR layer 10. The upper AlGaAsP transition layer 11 was composed of Al x14 Ga 1-x14 As y9 P 1-y9 The x14 = 0.7 and y9 = 0.99. The doping source for the upper AlGaAsP transition layer 11 is Cp2Mg, and the doping concentration is 1E18 atoms / cm³. 3 The DBR (AlGaAsP) transition layer 11 was implemented through the aforementioned AlGaAsP transition layer 11. x13 Ga 1-x13 ) y8 In 1-y8 P and DBRAl x15 Ga 1-x15 As / P component switching in As avoids the situation in the active region (Al) x11 Ga 1-x11 ) y6 In 1-y6 P-barrier layer and DBRAl x15 Ga 1-x15 The formation of AsP complexes at the As interface can affect surface roughness and device reliability.

[0073] S12, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second low refractive index difference AlGaAs DBR layer 12 on the upper AlGaAsP transition layer 11. The second low refractive index difference AlGaAs DBR layer 12 consists of alternating Al atoms from bottom to top. x15 Ga 1-x15 As layer, Al x16 Ga 1-x16 In layer As, x15 = 0.9, x16 = 0.5. Al x15 Ga 1-x15 The As layer thickness is 50.7 nm, and the Al layer thickness is... x16 Ga 1-x16 The As layer has a thickness of 46.1 nm, wherein the Al x15 Ga 1-x15 As gradually transitions to Al x16 Ga 1-x16 In the case of the As layer, the Al composition of the gradient layer between the two layers gradually changes from 0.9 to 0.5, and the thickness of the gradient layer is 25.3 nm. x16 Ga 1-x16 As layer gradually transitions to Al. x15 Ga 1-x15When the Al composition of the gradient layer between the two layers gradually changes from 0.5 to 0.98, the thickness of the gradient layer is 23.1 nm. The doping source of the second low refractive index difference AlGaAs DBR layer 12 is C, and the doping concentration is 2E18 atoms / cm³. 3 The number of pairs is 30. The Al... x15 Ga 1-x15 As layer and Al x16 Ga 1-x16 Having an Al content greater than 0.5 in the As layer helps reduce losses caused by absorption of 650nm light into the quantum well.

[0074] S13, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second high refractive index difference AlGaAs DBR layer 13 on the second low refractive index difference AlGaAs DBR layer 12. The second high refractive index difference AlGaAs DBR layer 13 consists of alternating Al atoms from bottom to top. x17 Ga 1-x17 As layer, Al x18 Ga 1-x18 In the As layer, x17 = 0.9 and x18 = 0. The second high refractive index difference AlGaAs DBR layer has a C doping source of 13 and a doping concentration of 7E18 atoms / cm³. 3 There are 10 pairs. Al x17 Ga 1-x17 The As layer is 50.7 nm thick, and the Al layer is... x18 Ga 1-x18 The As layer is 42.7 nm thick, of which Al x17 Ga 1-x17 After the As layer has grown, Al x18 Ga 1-x18 Before the As layer grows, in the Al x17 Ga 1-x17 An Al composition gradient layer is disposed on the As layer, wherein the Al composition of the gradient layer gradually changes from 0.9 to 0.05, and the thickness of the gradient layer is 25.4 nm. The Al... x18 Ga 1-x18 After the As layer grows, Al x17 Ga 1-x17 Before the As layer grows, it is also in the Al x18 Ga 1-x18 An Al composition gradient layer is grown on the As layer, in which the Al composition gradually changes from 0.05 to 0.9. The thickness of the gradient layer is 21.4 nm. x17 Ga 1-x17 As layer, Al x18 Ga 1-x18When the As layer switches, an Al composition gradient layer is grown between the two layers, and the last Al layer... x17 Ga 1-x17 The As layer is made of AlAs material, and its purpose is to provide a high Al composition region for the wet oxidation process to form the insulating layer. Furthermore, an Al gradient is achieved by adjusting the TMAl flow rate. This second high refractive index difference AlGaAs DBR layer 13 achieves a reflectivity greater than 99.9% at 650 nm on the P-side. Reflectivity is improved by utilizing a high refractive index DBR.

[0075] S14: Stop the flow of TMAl and TMGa, and using the stop growth method, reduce the temperature to 530℃ at a rate not exceeding 50℃ / min. Maintain the temperature at 530℃, and continue to flow TMGa and AsH3 to grow a GaAs cap layer 14 on the second high refractive index difference AlGaAs DBR layer 13. The GaAs cap layer 14 has a thickness of 0.1μm, uses DEZn as the doping source, and has a doping concentration of 7E19 atoms / cm³. 3 After completion, the vertical-cavity surface-emitting laser (VSCEL) epitaxial structure is obtained.

[0076] Example 3

[0077] A method for fabricating an epitaxial structure of a vertical-cavity surface-emitting laser (VSCEL) includes the following steps:

[0078] S1. Place the GaAs substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 740℃ for baking, and introduce AsH3 to perform surface heat treatment on the GaAs substrate.

[0079] S2, the temperature is slowly reduced to 680℃ at a rate not exceeding 30℃ / min, and TMGa and AsH3 are continuously introduced to grow a GaAs buffer layer 2 on the GaAs substrate 1. The doping source of the GaAs buffer layer 2 is Si2H6, and the doping concentration is 2E18 atoms / cm³. 3 The GaAs buffer layer has a thickness of 0.5 μm. The purpose of the GaAs buffer layer 2 is to prevent defects from propagating from the substrate into the confinement layer, provide a fresh growth interface, and improve the material growth quality.

[0080] S3, the temperature is slowly increased to 730℃, with a heating rate not exceeding 50℃ / min, and TMAl, TMGa, and AsH3 are continuously introduced to grow the first high refractive index difference AlGaAs DBR layer 3 on the GaAs buffer layer 2. The first high refractive index difference AlGaAs DBR layer 3 consists of alternating layers of Al with a thickness of 51.9 nm distributed from bottom to top. x1 Ga 1-x1 As layer, 44.3nm Al x2 Ga1-x2 In layer As, x1 = 1, x2 = 0.3, and Al x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 The doping source for the As layer is Si₂H₆, and the doping concentration is 1E¹⁸ atoms / cm². 3 There are 3 pairs. The high refractive index of the first high refractive index difference AlGaAs DBR layer 3 is used to improve reflectivity.

[0081] S4, maintaining the temperature at 730℃, and continuing to introduce TMAl, TMGa, and AsH3 to grow a first low refractive index difference AlGaAs DBR layer 4 on the first high refractive index difference AlGaAs DBR layer 3. The first low refractive index difference AlGaAs DBR layer 4 consists of alternating layers of Al with a thickness of 51.9 nm distributed from bottom to top. x3 Ga 1-x3 As, 48.6nm Al x4 Ga 1-x4 The AlGaAs DBR layer is composed of As, with x3 = 1 and x4 = 0.7. The doping source for the first low refractive index difference AlGaAs DBR layer 4 is Si2H6, with a doping concentration of 1E18 atoms / cm³. 3 The number of pairs is 20. Using a first low refractive index difference AlGaAs DBR layer 4 with an Al composition greater than 0.5 can effectively reduce the absorption loss of 650nm light.

[0082] S5, the temperature is gradually reduced to 640℃ at a cooling rate not exceeding 50℃ / min. TMAl, TMGa, AsH3, and PH3 are continuously introduced to grow a lower AlGaAsP transition layer 5 with a thickness of 19.4 nm on the first low refractive index difference AlGaAs DBR layer 4. The composition of the lower AlGaAsP transition layer 5 is Al... x7 Ga 1-x7 As y3 P 1-y3 The values ​​are x7 = 0.5 and y3 = 0.85. The doping source for the lower AlGaAsP transition layer 5 is Si2H6, with a doping concentration of 1E18 atoms / cm³. 3 The AlGaAsP transition layer 5 is used to achieve As / P composition switching, avoiding the formation of AsP complexes at the active region interface, which would affect surface roughness and device reliability.

[0083] S6, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP DBR layer 6 on the lower AlGaAsP transition layer 5. The lower AlGaInP DBR layer 6 consists of alternating layers of Al(Al) with a thickness of 55.3 nm distributed from bottom to top.x5 Ga 1-x5 ) y1 In 1-y1 P layer, 48.8nm (Al) x6 Ga1-x6) y2 In 1-y2 In the P-layer, x5 = 1, y1 = 0.5, x6 = 0.3, and y2 = 0.5. The doping source for the lower AlGaInP DBR layer 6 is Si2H6, with a doping concentration of 1E18 atoms / cm³. 3 The number of pairs is 15. The lower AlGaInP DBR layer 6 can effectively reduce the DBR Al x4 Ga 1-x4 As and the active region (Al) x8 Ga 1-x8 ) y4 In 1-y4 The interface dislocations formed during the bonding of the P-barrier layer improve the reliability of the laser.

[0084] S7, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a lower AlGaInP barrier layer 7 with a thickness of 49.5 nm on the lower AlGaInP DBR layer 6. The composition of the lower AlGaInP barrier layer 7 is (Al... x8 Ga 1-x8 ) y4 In 1-y4 P, where x8 = 0.4, y4 = 0.5, and the lower AlGaInP barrier layer 7 is unintentionally doped. This lower AlGaInP barrier layer 7 provides a resonant cavity for the active region light, enabling photolasing.

[0085] S8, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow a GaInP / AlGaInP multiple quantum well barrier layer 8 on the lower AlGaInP barrier layer 7. The GaInP / AlGaInP multiple quantum well barrier layer 8 consists of alternating Ga atoms from bottom to top. x10 In 1-x10 P layer, (Al) x9 Ga 1-x9 ) y5 In 1-y5 The P-layer has x10 = 0.46, x9 = 0.4, and y4 = 0.5. The GaInP / AlGaInP multi-quantum-well barrier layer 8 has a well width of 5 nm, a barrier layer thickness of 6 nm, and emits light at a wavelength of 650 nm. It is unintentionally doped. This GaInP / AlGaInP multi-quantum-well barrier layer 8 enables 650 nm photoluminescence while simultaneously suppressing carrier overflow and confining the light field.

[0086] S9, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP barrier layer 9 with a thickness of 49.5 nm on the GaInP / AlGaInP multi-quantum-well barrier layer 8. The composition of the upper AlGaInP barrier layer 9 is (Al... x11 Ga 1-x11 ) y6 In 1-y6 P, where x11 = 0.4 and y6 = 0.5, is unintentionally doped. This AlGaInP barrier layer 9 provides a resonant cavity for the active region light, enabling photolasing.

[0087] S10, maintaining the temperature at 640℃, continues to introduce TMAl, TMGa, TMIn, and PH3 to grow an upper AlGaInP DBR layer 10 on the upper AlGaInP barrier layer 9. The upper AlGaInP DBR layer 10 consists of alternating layers of Al (Al2O3) with a thickness of 55.3 nm distributed from bottom to top. x12 Ga 1-x12 ) y7 In 1-y7 P layer, 48.8nm (Al) x13 Ga 1-x13 ) y8 In 1-y8 The P-layer. The doping source of the upper AlGaInP DBR layer 10 is Cp2Mg, and the doping concentration is 1E18 atoms / cm. 3 The number of pairs is 15. This AlGaInP DBR layer 10 achieves a reduction in DBR Al x15 Ga 1-x15 As and AlGaInP active region (Al x11 Ga 1-x11 ) y6 In 1-y6 The purpose of forming island-like dislocations in the P-barrier layer is to effectively improve the reliability of VSCEL.

[0088] S11, the temperature is gradually reduced to 730℃, and TMAl, TMGa, AsH3, and PH3 are continuously introduced to grow an upper AlGaAsP transition layer 11 with a thickness of 19.4 nm on the upper AlGaInP DBR layer 10. The upper AlGaAsP transition layer 11 is composed of Al x14 Ga 1-x14 As y9 P 1-y9 x14 = 0.5, y9 = 0.85. The doping source for the upper AlGaAsP transition layer 11 is Cp2Mg, and the doping concentration is 1E18 atoms / cm³. 3 The DBR (AlGaAsP) transition layer 11 was implemented through the aforementioned AlGaAsP transition layer 11.x13 Ga 1-x13 ) y8 In 1-y8 P and DBRAl x15 Ga 1-x15 As / P component switching in As avoids the need for As / P component switching in the active region (Al) x11 Ga 1-x11 ) y6 In 1-y6 P-barrier layer and DBRAl x15 Ga 1-x15 The problem of AsP complexes forming at the As interface affecting surface roughness and device reliability.

[0089] S12, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second low refractive index difference AlGaAs DBR layer 12 on the upper AlGaAsP transition layer 11. The second low refractive index difference AlGaAs DBR layer 12 consists of alternating Al atoms from bottom to top. x15 Ga 1-x15 As layer, Al x16 Ga 1-x16 In layer As, x15 = 1, x16 = 0.7. Al x15 Ga 1-x15 The As layer thickness is 51.9 nm, and the Al layer thickness is... x16 Ga 1-x16 The As layer has a thickness of 48.6 nm, wherein the Al x15 Ga 1-x15 As gradually transitions to Al x16 Ga 1-x16 When the As layer is used, and the Al composition of the gradient layer between the two layers gradually changes from 1 to 0.7, the thickness of the gradient layer is 25.9 nm. x16 Ga 1-x16 As layer gradually transitions to Al. x15 Ga 1-x15 When the Al composition of the gradient layer between the two layers gradually changes from 0.7 to 1, the thickness of this gradient layer is 24.3 nm. The doping source for the second low refractive index difference AlGaAs DBR layer 12 is C, with a doping concentration of 7E17 atoms / cm³. 3 There are 15 pairs. Al x15 Ga 1-x15 As layer and Al x16 Ga 1-x16 The Al content in the As layer is greater than 0.5, which reduces the loss caused by the absorption of 650nm light in the quantum well.

[0090] S13, maintaining the temperature at 730℃, continues to introduce TMAl, TMGa, and AsH3 to grow a second high refractive index difference AlGaAs DBR layer 13 on the second low refractive index difference AlGaAs DBR layer 12. The second high refractive index difference AlGaAs DBR layer 13 consists of alternating Al atoms from bottom to top. x17 Ga 1-x17 As layer, Al x18 Ga 1-x18 In the As layer, x17 = 1 and x18 = 0.3. The second high refractive index difference AlGaAs DBR layer has a C doping source of 13 and a doping concentration of 7E17 atoms / cm³. 3 There are 3 pairs. Al x17 Ga 1-x17 The As layer thickness is 51.9 nm, and the Al layer thickness is 51.9 nm. x18 Ga 1-x18 The As layer has a thickness of 44.3 nm, wherein the Al x17 Ga 1-x17 After the As layer has grown, Al x18 Ga 1-x18 Before the As layer grows, in the Al x17 Ga 1-x17 An Al composition gradient layer is disposed on the As layer, wherein the Al composition of the gradient layer gradually changes from 1 to 0.3, and the thickness of the gradient layer is 25.9 nm; x18 Ga 1-x18 After the As layer grows, Al x17 Ga 1- x17 Before the As layer grows, it is also in the Al x18 Ga 1-x18 An Al composition-gradient layer is grown on the As layer, in which the Al composition gradually changes from 0.3 to 1, and the thickness is 22.2 nm. That is, whenever the Al... x17 Ga 1-x17 As layer, Al x18 Ga 1-x18 When the As layer switches, an Al composition gradient layer is grown between the two layers, and the last Al layer... x17 Ga 1-x17 The As layer is made of AlAs material, and its purpose is to provide a high Al composition region for the wet oxidation process to form the insulating layer. Furthermore, an Al gradient is achieved by adjusting the TMAl flow rate. This second high refractive index difference AlGaAs DBR layer 13 achieves a reflectivity greater than 99.9% at 650 nm on the P-side. Reflectivity is improved by utilizing a high refractive index DBR.

[0091] S14: Stop the flow of TMAl and TMGa, and using the stop growth method, reduce the temperature to 530℃ at a rate not exceeding 50℃ / min. Maintain the temperature at 530℃, and continue to flow TMGa and AsH3 to grow a GaAs cap layer 14 on the second high refractive index difference AlGaAs DBR layer 13. The GaAs cap layer 14 has a thickness of 0.5μm, uses DEZn as the doping source, and has a doping concentration of 3E19 atoms / cm³. 3 After completion, the vertical-cavity surface-emitting laser (VSCEL) epitaxial structure is obtained.

[0092] Performance testing

[0093] The surface-emitting vertical-cavity surface-emitting laser prepared in the above embodiments (reference) Figure 1 The epitaxial structure of this type of laser differs significantly from that of conventional edge-emitting lasers. For example, the aforementioned vertical-cavity surface-emitting laser (VCSEL) has two DBR layers (a first low-refractive-index-difference AlGaAs DBR layer 4 and a lower AlGaAsP transition layer 5, a second low-refractive-index-difference AlGaAs DBR layer 12, and a second high-refractive-index-difference AlGaAs DBR layer 13), utilizing the difference in reflectivity to achieve photolasing. The resonant cavity is formed by the lower AlGaInP barrier layer 7 and the GaInP / AlGaInP multiple quantum well barrier layer 8. Edge-emitting lasers, on the other hand, typically do not contain a DBR layer; instead, they form the resonant cavity by depositing a dissociated cavity length film. Edge-emitting lasers have a relatively large beam divergence angle, requiring improved optical coupling efficiency between the light source and the waveguide, and necessitating the use of other auxiliary devices. The vertical cavity surface-emitting laser described above emits light from a direction perpendicular to the surface of the resonant cavity, with a basically circular light spot. It can also be used in the manufacture of two-dimensional communication arrays, and is especially suitable for board-to-board network transmission or the transmission end of two-dimensional fiber bundles. This is something that traditional edge-emitting semiconductor lasers cannot do, and it has unparalleled advantages in the field of fiber optic applications.

[0094] Figure 2 and Figure 3 The images show the laser spot patterns of the vertical-cavity surface-emitting laser epitaxial structure and the conventional edge-emitting laser epitaxial structure prepared in Example 1 above. It can be seen that the laser spot of the vertical-cavity surface-emitting laser epitaxial structure is a prototype, while the laser spot of the conventional edge-emitting laser epitaxial structure is elliptical. In applications in optical fiber communication, this requires additional focusing, which increases the manufacturing difficulty.

[0095] Figure 4 and Figure 5The figures show the PIV curves of the vertical-cavity surface-emitting laser epitaxial structure prepared in Example 1 and the conventional edge-emitting laser epitaxial structure, respectively. It can be seen that the threshold current of the vertical-cavity surface-emitting laser epitaxial structure is 3 mA, and the maximum output power is 6 mW. In contrast, the threshold current of the conventional edge-emitting 650 nm epitaxial structure is 11.6 mA, and the maximum output power is greater than 7 mW. Due to the surface-emitting upper and lower DBR reflector design of the vertical-cavity surface-emitting laser epitaxial structure, the threshold current is relatively small, therefore, the vertical-cavity surface-emitting laser epitaxial structure can operate stably at 650 nm.

[0096] Finally, it should be noted that any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Although specific embodiments of this invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of this invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. An epitaxial structure for a vertical-cavity surface-emitting laser, wherein, The epitaxial structure, from bottom to top, comprises: a substrate, a buffer layer, a first high refractive index difference AlGaAs DBR layer, a first low refractive index difference AlGaAs DBR layer, a lower AlGaAsP transition layer, a lower AlGaInP DBR layer, a lower AlGaInP barrier layer, a GaInP / AlGaInP multiple quantum well barrier layer, an upper AlGaInP barrier layer, an upper AlGaInP DBR layer, an upper AlGaAsP transition layer, a second low refractive index difference AlGaAs DBR layer, a second high refractive index difference AlGaAs DBR layer, and a GaAs cap layer; wherein: The first high refractive index difference AlGaAs DBR layer consists of alternating Al layers from bottom to top. x1 Ga 1-x1 As layer, Al x2 Ga 1-x2 For layer A, 0.9 ≤ x1 ≤ 1, 0 ≤ x2 ≤ 0.3; The first low refractive index difference AlGaAs DBR layer consists of alternating Al layers from bottom to top. x3 Ga 1-x3 As layer, Al x4 Ga 1-x4 For layer As, 0.9 ≤ x3 ≤ 1, 0.5 ≤ x4 ≤ 0.7; The composition of the lower AlGaAsP transition layer is Al x7 Ga 1-x7 As y3 P 1-y3 , 0.5≤x7≤0.7, 0.85≤y3≤0.99; The lower AlGaInP DBR layer consists of alternating layers of Al from bottom to top. x5 Ga 1-x5 ) y1 In 1-y1 P layer and (Al) x6 Ga 1-x6 ) y2 In 1-y2 Layer P, 0.9≤x5≤1, 0.4≤y1≤0.6, 0≤x6≤0.3, 0.4≤y2≤0.6; The material of the lower AlGaInP barrier layer is (Al x8 Ga 1-x8 ) y4 In 1-y4 P, 0.4≤x8≤0.7, 0.4≤y4≤0.6; The GaInP / AlGaInP multiple quantum well barriers are composed of alternating Ga atoms from bottom to top. x10 In 1-x10 P layer, (Al) x9 Ga 1-x9 ) y5 In 1-y5 Layer P, 0.4≤x10≤0.5, 0.1≤x9≤0.5, 0.4≤y5≤0.6; The upper AlGaInP DBR layer is the same as the lower AlGaInP DBR layer; the upper AlGaAsP transition layer is the same as the lower AlGaAsP transition layer; the second low refractive index difference AlGaAs DBR layer is the same as the first low refractive index difference AlGaAs DBR layer; and the second high refractive index difference AlGaAs DBR layer is the same as the first high refractive index difference AlGaAs DBR layer.

2. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, In the lower AlGaInPDBR layer, (Al x5 Ga 1-x5 ) y1 In 1-y1 P layer, (Al) x6 Ga 1-x6 ) y2 In 1-y2 The thickness of the P layer is λ1 / 4n, where n is the optical refractive index of the corresponding material layer at a wavelength of 650nm, and λ1 is the wavelength of the corresponding material layer.

3. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The thickness of the lower AlGaInP barrier layer is less than λ2 / 4, where λ2 is the wavelength of the lower AlGaInP barrier layer.

4. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The total thickness of the GaInP / AlGaInP multiple quantum well barrier is less than λ3 / 4, where λ3 is the wavelength of the multiple quantum well barrier.

5. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first high refractive index difference AlGaAs DBR layer is doped with Si atoms.

6. The vertical-cavity surface-emitting laser epitaxial structure according to claim 5, characterized in that, The Si atom doping concentration is 1E18-7E18 atoms / cm³. 3 The number of pairs is 3-15.

7. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first low refractive index difference AlGaAs DBR layer is doped with Si atoms.

8. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 7, characterized in that, The Si atom doping concentration is 1E18-7E18 atoms / cm³. 3 The number of pairs is 20-35.

9. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The lower AlGaAsP transition layer is doped with Si atoms.

10. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 9, characterized in that, The Si atom doping concentration is 1E18-7E18 atoms / cm³. 3 .

11. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The lower AlGaInPDBR layer is doped with Si atoms.

12. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 11, characterized in that, The Si atom doping concentration is 2E17-1E18 / cm³. 3 The number of pairs is 5-15.

13. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The thickness of the lower AlGaInP barrier layer is 50-150 nm.

14. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The thickness of the AlGaInP barrier layer is 50-150 nm.

15. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The well width and thickness of the GaInP / AlGaInP multi-quantum-well barrier layer are 3-7 nm.

16. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 15, characterized in that, The thickness of the multiple quantum well barrier layer is 4-8 nm.

17. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The upper AlGaInPDBR layer is doped with Mg atoms.

18. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 17, characterized in that, The Mg atom doping concentration is 2E17-1E18 / cm³. 3 The number of pairs is 5-15.

19. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The upper AlGaAsP transition layer is doped with Mg atoms.

20. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 19, characterized in that, The Mg atom doping concentration is 7E17-5E18 / cm³. 3 .

21. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The second low refractive index difference AlGaAs DBR layer is doped with Mg atoms.

22. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 21, characterized in that, The Mg atom doping concentration is 7E17-5E18 atoms / cm³. 3 The number of pairs is 15-30.

23. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The second high refractive index difference AlGaAs DBR layer is doped with Mg atoms.

24. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 23, characterized in that, The Mg atom doping concentration is 7E17-5E18 atoms / cm³. 3 The number of pairs is 3-10.

25. The epitaxial structure of a vertical-cavity surface-emitting laser according to any one of claims 1-24, characterized in that, The cap layer is doped with Zn atoms.

26. The epitaxial structure of a vertical-cavity surface-emitting laser according to claim 25, characterized in that, The Zn atom doping concentration is 3E19-7E19 atoms / cm³. 3 .

27. The epitaxial structure of a vertical-cavity surface-emitting laser according to any one of claims 1-24, characterized in that, The thickness of the cap layer is 0.1-0.5 μm.

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