Vcsel structure for optimizing oxidation uniformity and preparation method thereof
By growing the tensile stressed AlxGa1-xAsyP1-y epitaxial layer under the oxide layer of the Vcsel structure, the problem of inconsistent oxidation pore shape and mesa structure geometry caused by compressive stress during oxidation is solved, and the oxidation uniformity and beam restriction effect are optimized.
Patent Information
- Application Number
- CN202510341589.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-06-10
AI Technical Summary
During the oxidation process, the shape of the oxidation pores is inconsistent with the geometry of the mesa structure due to compressive stress, which affects the beam limiting effect.
A tensile stressed AlxGa1-xAsyP1-y epitaxial layer is grown below the oxide layer to offset the compressive stress caused by the N-type DBR reflective layer and the MQW layer, and improve the consistency of Al component and surface density in all directions of the AlGaAs crystal of the oxide layer.
Effectively reduce the compressive stress on the oxide layer, ensure that the shape of the oxidation pore is consistent with the geometric shape of the mesa structure, and optimize the oxidation uniformity of the Vcsel structure.
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Figure CN120127501A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductor lasers, and particularly relates to a Vcsel structure for optimizing oxidation uniformity and a preparation method thereof. Background Art
[0002] Vertical cavity surface emitting laser (VCSEL) is a surface emitting laser. Compared with traditional edge emitting lasers, it has the advantages of low threshold current, high integration, circularly symmetrical spot, and small size. Currently, VCSEL is widely used in laser radar, short-distance communication, facial recognition and other fields.
[0003] The existing mainstream Vcsel is composed of an N-type DBR layer doped with N-type elements, a resonant cavity layer, a P-type DBR layer doped with P-type elements, and an ohmic contact layer. The resonant cavity layer includes a lower limiting layer, an MQW layer, an upper limiting layer, and an oxide layer from bottom to top. In practical applications, Vcsel often needs to control the shape of the oxidation hole to be consistent with the geometric shape of the table structure, so that it will have better application efficiency in subsequent applications, so the light beam needs to be limited. There are three existing methods for limiting the light beam: the first is the air column method, which will make the aperture of the limiting hole larger, and the electrode manufacturing process is more difficult and cannot be quantified; the second is the ion implantation method, which only has the function of current limitation and cannot limit the light beam; the third is the oxidation aperture method, which grows a layer of Al in the epitaxial layer. x GaAs oxide layer, Al content needs to be greater than 97%, thickness is 15-30nm, Al x The position of the GaAs oxide layer needs to be located at the node of the periodic resonance wave in the resonant cavity. AlGaAs with a high Al content is easily oxidized by water vapor to form AlO x , has good electrical insulation properties, and AlO x The refractive index is low, which plays the role of a refractive index waveguide and can effectively limit the light beam. Moreover, this method has a high repetition rate and is easy for large-scale mass production. It is the current mainstream Vcsel production method.
[0004] The oxide layer is located above the N-type DBR layer and the MQW layer. The DBR of Vcesl is composed of AlGaAs with different Al components. The lattice matching of the AlGaAs epitaxial layer and the substrate is inconsistent and is in a compressive stress state. When MQW uses a large compressive stress material, the entire epitaxial layer will accumulate a large amount of compressive stress. Al is grown on the basis of the large compressive stress. x The GaAs oxide layer will cause the Al composition and surface density in all directions of the AlGaAs crystal to be different, resulting in different oxidation rates, which will lead to a large difference in the shape of the oxide hole and the geometric shape of the mesa structure. The shape of the oxide hole after oxidation of the existing Vcsel structure is as follows: Figure 1shown. Summary of the invention
[0005] The purpose of the present invention is to provide a Vcsel structure with optimized oxidation uniformity and a preparation method thereof, so as to improve the phenomenon that the oxidation rate of the oxide layer of the vertical cavity surface emitting laser is inconsistent in various directions, resulting in the inconsistency between the shape of the oxidation hole and the geometric shape of the mesa structure.
[0006] To achieve the above object, the present invention provides the following technical solutions: A Vcsel structure for optimizing oxidation uniformity, comprising a substrate, a buffer layer, an N-type DBR reflective layer, a resonant cavity layer, a P-type DBR reflective layer and an ohmic contact layer stacked in sequence from bottom to top; The resonant cavity layer includes a lower confinement layer, an MQW layer, an upper confinement layer, and an oxide layer stacked in sequence from bottom to top. A first epitaxial layer is grown below the oxide layer. The first epitaxial layer is Al x Ga 1-x As y P 1-y Epitaxial layer, wherein 0≤x≤0.8, 0.1≤y≤0.3.
[0007] Optionally, a second epitaxial layer is grown on the oxide layer, and the structure and material composition of the second epitaxial layer are the same as those of the first epitaxial layer.
[0008] Optionally, the thickness of the first epitaxial layer and the second epitaxial layer are both 20-30 mm.
[0009] Optionally, the oxide layer is Al x Ga 1-x As oxide layer, wherein 0.97≤x≤1, and the thickness of the oxide layer is 15-30nm.
[0010] Optionally, the N-type DBR reflective layer and the P-type DBR reflective layer are both formed by alternating growth of multiple groups of AlGaAs layers with high Al content and AlGaAs layers with low Al content, the Al content of the high Al content AlGaAs layer is in the range of 80%-95%, the Al content of the low Al content AlGaAs layer is in the range of 2%-50%, and the optical thickness of the high Al content AlGaAs layer and the low Al content AlGaAs layer are both one-quarter of the Vcsel emission laser wavelength; wherein the number of alternating pairs of the high Al content AlGaAs layer and the low Al content AlGaAs layer of the N-type DBR reflective layer is between 30-40 pairs, and the doping element is the N-type doping element Si; the number of alternating pairs of the high Al content AlGaAs layer and the low Al content AlGaAs layer of the P-type DBR reflective layer is between 15-25 pairs, and the doping element is the P-type doping element C.
[0011] Optionally, the MQW layer consists of 3 groups of In x Ga 1-x As layer and Al y Ga 1-y As layers are alternately grown, where 0≤x≤0.15, 0.1≤y≤0.4, In x Ga 1-x The thickness of the As layer is 6 nm, and the Al y Ga 1-y The thickness of the As layer is 8 nm, and the MQW layer is not intentionally doped.
[0012] Optionally, the lower confinement layer and the upper confinement layer are both made of AlGaAs material, and the Al content ranges from 20% to 40%; the thickness of the lower confinement layer and the upper confinement layer are both 90-120nm, the doping element of the lower confinement layer is Si, and the doping element of the upper confinement layer is C.
[0013] The present invention also provides a method for preparing a Vcsel structure with optimized oxidation uniformity, comprising: growing a buffer layer on the substrate; Growing an N-type DBR reflective layer on the buffer layer; Growing a lower confinement layer on the N-type DBR reflective layer; growing a MQW layer on the lower confinement layer; growing an upper confinement layer on the MQW layer; A first epitaxial layer is grown on the upper confinement layer, wherein the first epitaxial layer is Al with tensile stress. x Ga 1-x As y P 1-y Epitaxial layer, wherein 0≤x≤0.8, 0.1≤y≤0.3; growing an oxide layer on the first epitaxial layer; Growing a P-type DBR reflective layer on the oxide layer; An ohmic contact layer is grown on the P-type DBR reflective layer.
[0014] Optionally, a second epitaxial layer is grown between the oxide layer and the P-type DBR reflective layer, and the structure and material composition of the second epitaxial layer are the same as those of the first epitaxial layer.
[0015] Optionally, after the ohmic contact layer is grown, the Vcsel structure is placed in an oxidation furnace for wet oxidation, the temperature of the oxidation furnace is 420° C., the water temperature is 95° C., the nitrogen flow rate is 1.5 L / min, and the oxidation time is 30 min.
[0016] After adopting the above scheme, the beneficial effects of the present invention are: The present invention grows a first epitaxial layer below the original oxide layer, and the first epitaxial layer is Al with tensile stress.x Ga 1-x As y P 1-y Epitaxial layer, wherein 0≤x≤0.8, 0.1≤y≤0.3, the tensile stress of the first epitaxial layer can effectively offset the compressive stress caused by the N-type DBR reflective layer and the MQW layer, thereby effectively reducing the compressive stress on the oxide layer, and effectively improving the consistency of the Al component and surface density of the AlGaAs crystal in all directions of the oxide layer, so that the oxidation rate in all directions is consistent, ensuring that the shape of the oxidation hole is consistent with the geometric shape of the mesa structure, so as to optimize the oxidation uniformity of the Vcsel structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic diagram of the shape of the oxidation holes of the existing Vcsel structure after oxidation; Figure 2 This is a schematic diagram of the shape of the oxidation holes of the Vcsel structure after oxidation of the present invention; Figure 3 It is a structural schematic diagram of the red light Vcsel structure of the present invention; Figure 4 It is a process flow chart of the preparation method of the present invention.
[0018] Description of labels: 1. Buffer layer; 2. N-type DBR reflective layer; 3. Lower limiting layer; 4. MQW layer; 5. Upper limiting layer; 6. First epitaxial layer; 7. Oxide layer; 8. Second epitaxial layer; 9. P-type DBR reflective layer; 10. Ohmic contact layer. DETAILED DESCRIPTION
[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0020] Please refer to Figure 3 The present invention provides a Vcsel structure for optimizing oxidation uniformity, comprising a substrate, a buffer layer 1, an N-type DBR reflective layer 2, a resonant cavity layer, a P-type DBR reflective layer 9 and an ohmic contact layer 10 stacked in sequence from bottom to top.
[0021] The resonant cavity layer comprises a lower limiting layer 3, an MQW layer 4, an upper limiting layer 5, and an oxide layer 7 which are stacked in sequence from bottom to top, wherein the oxide layer 7 is an AlGaAs oxide layer 7, and the oxide layer 7 functions to limit current injection and light beam; AlGaAs with a high Al content is easily oxidized by water vapor to generate AlO x, having good electrical insulation properties, and the refractive index of AlO x is relatively low, acting as a refractive index waveguide, which can effectively confine the light beam; since the oxide layer 7 introduces oxygen elements and there are uncertain elements, the oxide layer 7 needs to be placed at the node position of the resonant cavity to ensure the minimization of light attenuation. However, the oxide layer 7 is located above the N-type DBR reflective layer 2 and the MQW layer 4, and the lattice matching between the N-type DBR reflective layer 2 and the substrate is inconsistent, in a compressive stress state. Moreover, if the MQW layer 4 uses a material with a large compressive stress, a large amount of compressive stress will accumulate in the entire epitaxial layer. Growing the oxide layer 7 on the basis of a large compressive stress will cause differences in the Al composition and surface density in all directions of the AlGaAs crystal of the oxide layer 7, resulting in different oxidation rates, and causing a large difference between the shape of the oxidation holes and the geometric shape of the mesa structure.
[0022] In view of this, the present invention grows a first epitaxial layer 6 below the oxide layer 7. The first epitaxial layer 6 is a tensile stress Al x Ga 1-x As y P 1-y epitaxial layer, where 0 ≤ x ≤ 0.8, 0.1 ≤ y ≤ 0.3. The tensile stress of the first epitaxial layer 6 can effectively offset the compressive stress brought by the N-type DBR reflective layer 2 and the MQW layer 4, can effectively reduce the compressive stress received by the AlGaAs oxide layer 7, improve the consistency of the Al composition and surface density in all directions, make the oxidation rates in all directions consistent, ensure that the shape of the oxidation holes is consistent with the geometric shape of the mesa structure, so as to optimize the oxidation uniformity of the Vcsel structure. The shape of the oxidation holes after oxidation of the Vcsel structure of the present invention is as Figure 2 shown, and the shape of the oxidation holes is almost consistent with the geometric shape of the mesa structure.
[0023] Optionally, the thickness of the tensile stress Al x Ga 1-x As y P 1-y epitaxial layer is 20 - 30 mm.
[0024] Optionally, a tensile stress Al x Ga 1-x As y P 1-y epitaxial layer can be grown above the oxide layer 7 as the second epitaxial layer 8. The structure, material composition and thickness of the second epitaxial layer 8 are the same as those of the first epitaxial layer 6. The two-layer tensile stress epitaxial layer structure can more effectively offset the compressive stress brought by the N-type DBR reflective layer 2 and the MQW layer 4, and has a better optimization effect on the oxidation uniformity of the Vcsel structure.
[0025] Specifically, the growth material of the oxide layer 7 is Al x Ga1-x As is Al x Ga 1-x An As oxide layer, where 0.97 ≤ x ≤ 1, and the thickness of the oxide layer 7 is 15 - 30 nm.
[0026] It should be noted that the resonant cavity layer also includes a small part of the N-type DBR reflective layer 2 and the P-type DBR reflective layer 9, and the thickness is extremely small and can be ignored.
[0027] Optionally, the substrate is specifically a GaAs substrate.
[0028] Optionally, the buffer layer 1 grown on the GaAs substrate is a GaAs buffer layer with a thickness of 500 nm, and the doping element is an N-type doping element Si, which has the function of connecting the substrate and the subsequent grown epitaxial layer and reducing the defects of the epitaxial layer.
[0029] Specifically, in the N-type DBR reflective layer 2 and the P-type DBR reflective layer 9, DBR (distributed Bragg reflective) is a mirror structure that can form a stable oscillating standing wave together with the resonant cavity layer to achieve the output of laser. DBR contains an adjustable multi-layer structure composed of two optical materials. In the present invention, both the N-type DBR reflective layer 2 and the P-type DBR reflective layer 9 are formed by alternately growing AlGaAs layers with a high Al content and AlGaAs layers with a low Al content. The Al content range of the AlGaAs layer with a high Al content is 80% - 95%, and the Al content range of the AlGaAs layer with a low Al content is 2% - 50%; among them, the optical thicknesses of both the AlGaAs layer with a high Al content and the AlGaAs layer with a low Al content are one-fourth of the Vcsel emission laser wavelength.
[0030] Optionally, the number of alternations of the AlGaAs layer with a high Al content and the AlGaAs layer with a low Al content in the N-type DBR reflective layer 2 is between 30 - 40 pairs, and the doping element is an N-type doping element Si; the number of alternations of the AlGaAs layer with a high Al content and the AlGaAs layer with a low Al content in the P-type DBR reflective layer 9 is between 15 - 25 pairs, and the doping element is a P-type doping element C.
[0031] Specifically, both the lower confinement layer 3 and the upper confinement layer 5 are composed of AlGaAs material, and the Al content range of AlGaAs is 20% - 40%. Both the lower confinement layer 3 and the upper confinement layer 5 have the function of confining carriers.
[0032] Optionally, the thicknesses of both the lower confinement layer 3 and the upper confinement layer 5 are 90 - 120 nm. The doping element of the lower confinement layer 3 is Si, and the doping element of the upper confinement layer 5 is C.
[0033] Specifically, the MQW layer 4, i.e., the Multiple Quantum Wells layer, is composed of multiple groups of In x Ga 1- x As layers and Al y Ga 1-y As layers grown alternately. Among them, 0 ≤ x ≤ 0.15, 0.1 ≤ y ≤ 0.4. The MQW layer 4 has multiple functions such as light emission and wavelength control, improving light emission efficiency, optimizing device performance, and enhancing reliability.
[0034] Optionally, the thickness of the In x Ga 1-x As layer is 6 nm, and the thickness of the Al y Ga 1-y As layer is 8 nm. The MQW layer 4 is unintentionally doped.
[0035] Optionally, the ohmic contact layer 10 is a highly doped GaAs ohmic contact layer 10 with a thickness of 20 nm and a doping concentration reaching 1E 20 cm -3 or above, and the doping element is C; the ohmic contact layer 10 has functions such as current injection and transmission, and reducing contact resistance.
[0036] The present invention also provides a preparation method for an optimized Vcsel structure with uniform oxidation. Specifically, the metal organic chemical vapor deposition (MOCVD) method is adopted to grow a buffer layer 1, an N-type DBR reflection layer 2, a resonant cavity layer, a P-type DBR reflection layer 9, and an ohmic contact layer 10 on the substrate from bottom to top. Among them, the resonant cavity layer includes a lower confinement layer 3, an MQW layer 4, an upper confinement layer 5, and an oxidation layer 7 grown in sequence from bottom to top. A first epitaxial layer 6 with tensile stress is grown below the oxidation layer 7, or a first epitaxial layer 6 with tensile stress and a second epitaxial layer 8 are grown on both sides of the oxidation layer 7 respectively.
[0037] Please refer to Figure 3-4 , and the preparation method specifically includes the following steps: S1. Grow a buffer layer 1 on the substrate.
[0038] Optionally, the substrate is a GaAs substrate, and the buffer layer 1 is a GaAs buffer layer with a growth thickness of 500 nm and a doping element of an N-type doping element Si, which is used to connect the substrate and the subsequent grown epitaxial layer to reduce the defects of the epitaxial layer.
[0039] S2. Grow an N-type DBR reflection layer 2 on the buffer layer 1.
[0040] Specifically, the N-type DBR reflective layer 2 serves as a mirror in the Vcsel and can form a stable oscillating standing wave together with the resonant cavity layer, thereby realizing the output of laser. The N-type DBR reflective layer 2 is formed by alternately growing AlGaAs layers with a high Al content and AlGaAs layers with a low Al content. The Al content range of the AlGaAs layer with a high Al content is 80%-95%, and the Al content range of the AlGaAs layer with a low Al content is 2%-50%; among them, the optical thickness of both the AlGaAs layer with a high Al content and the AlGaAs layer with a low Al content is one-fourth of the laser emission wavelength of the Vcsel.
[0041] Optionally, the number of alternating pairs of the AlGaAs layer with a high Al content and the AlGaAs layer with a low Al content in the N-type DBR reflective layer 2 is between 30 and 40, and the doping element is the N-type doping element Si.
[0042] S3. Grow the lower confinement layer 3 on the N-type DBR reflective layer 2.
[0043] Specifically, the lower confinement layer 3 is composed of AlGaAs material, and the Al content range of the AlGaAs is 20%-40%. Its main function is to confine carriers.
[0044] Optionally, the growth thickness of the lower confinement layer 3 is 90-120nm, and the doping element is Si.
[0045] S4. Grow the MQW layer 4 on the lower confinement layer 3.
[0046] Specifically, the MQW layer 4 is composed of multiple groups of In x Ga 1-x As layers and Al y Ga 1-y As layers grown alternately. Among them, 0≤x≤0.15, 0.1≤y≤0.4. The MQW layer 4 has multiple functions such as light emission and wavelength control, improving light emission efficiency, optimizing device performance, and enhancing reliability.
[0047] Optionally, the growth thickness of the In x Ga 1-x As layer is 6nm, and the growth thickness of the Al y Ga 1-y As layer is 8nm. The MQW layer 4 is unintentionally doped.
[0048] S5. Grow the upper confinement layer 5 on the MQW layer 4.
[0049] Specifically, the upper confinement layer 5 is composed of AlGaAs material, and the Al content range of the AlGaAs is 20%-40%. Its main function is to confine carriers.
[0050] Optionally, the growth thickness of the upper confinement layer 5 is 90 - 120 nm, and the doping element is Si.
[0051] S6. Grow a first epitaxial layer 6 on the upper confinement layer 5.
[0052] Specifically, the first epitaxial layer 6 is a tensile-stress Al x Ga 1-x As y P 1-y epitaxial layer, where 0 ≤ x ≤ 0.8, 0.1 ≤ y ≤ 0.3. The tensile stress of the first epitaxial layer 6 can effectively offset the compressive stress brought by the N-type DBR reflector layer 2 and the MQW layer 4, can effectively reduce the compressive stress on the AlGaAs oxide layer 7, effectively improve the consistency of the Al component and surface density in all directions, make the oxidation rate consistent in all directions, ensure that the shape of the oxidation holes is consistent with the geometric shape of the mesa structure, so as to optimize the oxidation uniformity of the Vcsel structure.
[0053] Optionally, the growth thickness of the first epitaxial layer 6 is 20 - 30 nm, and the doping element is C.
[0054] S7. Grow an oxide layer 7 on the first epitaxial layer 6.
[0055] Specifically, the oxide layer 7 is an AlGaAs oxide layer 7. The function of the oxide layer 7 is to limit current injection and limit the light beam; since AlGaAs with a high Al component is easily oxidized by water vapor to form AlO x , it has good electrical insulation characteristics, and the refractive index of AlO x is relatively low, playing the role of a refractive index waveguide and being able to effectively limit the light beam; because the oxide layer 7 introduces oxygen elements and there are uncertain elements, the oxide layer 7 needs to be placed at the node of the resonant cavity to ensure the minimization of light attenuation.
[0056] Optionally, the growth material of the oxide layer 7 is Al x Ga 1-x As, where 0.97 ≤ x ≤ 1, and the growth thickness is 15 - 30 nm.
[0057] S8. Grow a P-type DBR reflector layer 9 on the oxide layer 7.
[0058] Specifically, the function and growth material of the P-type DBR reflector layer 9 are the same as those of the N-type DBR reflector layer 2, and are both formed by alternately growing AlGaAs layers with a high Al content and AlGaAs layers with a low Al content, and the Al content and growth thickness of the AlGaAs layers with a high Al content and the AlGaAs layers with a low Al content are also the same as those of the N-type DBR reflector layer 2.
[0059] Optionally, the number of alternating pairs of the high-Al-content AlGaAs layer and the low-Al-content AlGaAs layer in the P-type DBR reflective layer 9 is between 15 and 25 pairs, and the doping element is the P-type doping element C.
[0060] S9. Grow an ohmic contact layer 10 on the P-type DBR reflective layer 9.
[0061] Specifically, the growth material of the ohmic contact layer 10 is GaAs, the growth thickness is 20 nm, the doping element is the P-type doping element C, and the doping amount reaches 1E 20 cm -3 , which is a highly doped GaAs ohmic contact layer 10. The ohmic contact layer 10 has functions such as current injection and transmission and reduction of contact resistance.
[0062] S10. Place the Vcsel structure in an oxidation furnace for wet oxidation.
[0063] Specifically, after growing the ohmic contact layer 10, place the Vcsel structure in an oxidation furnace for wet oxidation. The furnace temperature of the oxidation furnace is 420 °C, the water temperature is 95 °C, the nitrogen flow rate is 1.5 L / min, and the oxidation time is 30 min. The shape of the oxidation holes after oxidizing the Vcsel structure is as Figure 2 shown, and the shape of the oxidation holes is almost the same as the geometric shape of the mesa structure.
[0064] Optionally, a tensile-stress Al x Ga 1-x As y P 1-y epitaxial layer can be grown between the oxidation layer 7 and the P-type DBR reflective layer 9. This epitaxial layer is the second epitaxial layer 8. That is, after step S8, grow the second epitaxial layer 8 on the oxidation layer 7, and then grow the P-type DBR reflective layer 9 on the second epitaxial layer 8. The structure, material composition, and thickness of the second epitaxial layer 8 are the same as those of the first epitaxial layer 6. The two tensile-stress epitaxial layer structures can more effectively offset the compressive stress brought by the N-type DBR reflective layer 2 and the MQW layer 4, and have a better optimization effect on the oxidation uniformity of the Vcsel structure.
[0065] In summary, the present invention provides a Vcsel structure for optimizing oxidation uniformity and a preparation method thereof. In the present invention, a tensile-stress epitaxial layer is grown below the oxidation layer 7, which is the first epitaxial layer 6, or a tensile-stress epitaxial layer is grown on both sides of the oxidation layer 7, which are the first epitaxial layer 6 and the second epitaxial layer 8 from bottom to top. The first epitaxial layer 6 and the second epitaxial layer 8 are both tensile-stress Al x Ga 1-x As y P 1-yAn epitaxial layer, where 0≤x≤0.8 and 0.1≤y≤0.3. The tensile stress of the first epitaxial layer 6 and the second epitaxial layer 8 can effectively offset the compressive stress brought by the N-type DBR reflective layer 2 and the MQW layer 4, effectively reduce the compressive stress on the AlGaAs oxide layer 7, effectively improve the consistency of the Al component and surface density in all directions, make the oxidation rate in all directions consistent, ensure that the shape of the oxidation holes is consistent with the geometric shape of the mesa structure, and the shape of the oxidation holes after the oxidation of the Vcsel structure is as Figure 2 shown, and the shape of the oxidation holes is almost the same as the geometric shape of the mesa structure.
[0066] It should be noted that the thicknesses of the buffer layer 1, N-type DBR reflective layer 2, lower confinement layer 3, MQW layer 4, upper confinement layer 5, first epitaxial layer 6, oxide layer 7, second epitaxial layer 8, P-type DBR reflective layer 9, and ohmic contact layer 10 shown in the drawings of this application are only examples and do not represent their actual thicknesses. Moreover, the actual ratio between the buffer layer 1, N-type DBR reflective layer 2, lower confinement layer 3, MQW layer 4, upper confinement layer 5, first epitaxial layer 6, oxide layer 7, second epitaxial layer 8, P-type DBR reflective layer 9, and ohmic contact layer 10 is not as shown in the drawings and is only for reference.
[0067] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.
[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this 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 Vcsel structure for optimizing oxidation uniformity, characterized in that: It includes a substrate, a buffer layer, an N-type DBR reflection layer, a resonant cavity layer, a P-type DBR reflection layer and an ohmic contact layer which are stacked in sequence from bottom to top; The resonant cavity layer includes a lower confinement layer, an MQW layer, an upper confinement layer, and an oxide layer stacked in sequence from bottom to top. A first epitaxial layer is grown below the oxide layer. The first epitaxial layer is Al x Ga 1-x As y P 1-y Epitaxial layer, wherein 0≤x≤0.8, 0.1≤y≤0.
3.
2. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 1, characterized in that: A second epitaxial layer is grown on the oxide layer, and the structure and material composition of the second epitaxial layer are the same as those of the first epitaxial layer.
3. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 2, characterized in that: The thickness of the first epitaxial layer and the second epitaxial layer are both 20-30 mm.
4. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 1, characterized in that: The oxide layer is Al x Ga 1-x As oxide layer, wherein 0.97≤x≤1, and the thickness of the oxide layer is 15-30nm.
5. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 1, characterized in that: The N-type DBR reflective layer and the P-type DBR reflective layer are both formed by alternating growth of multiple groups of AlGaAs layers with high Al content and AlGaAs layers with low Al content, the Al content of the high Al content AlGaAs layer is in the range of 80%-95%, the Al content of the low Al content AlGaAs layer is in the range of 2%-50%, and the optical thickness of the high Al content AlGaAs layer and the low Al content AlGaAs layer is one quarter of the wavelength of the Vcsel emission laser; wherein the number of alternating pairs of the high Al content AlGaAs layer and the low Al content AlGaAs layer of the N-type DBR reflective layer is between 30 and 40 pairs, and the doping element is the N-type doping element Si; the number of alternating pairs of the high Al content AlGaAs layer and the low Al content AlGaAs layer of the P-type DBR reflective layer is between 15 and 25 pairs, and the doping element is the P-type doping element C.
6. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 1, characterized in that: The MQW layer consists of 3 groups of x Ga 1-x As layer and Al y Ga 1-y As layers are alternately grown, where 0≤x≤0.15, 0.1≤y≤0.4, In x Ga 1-x The thickness of the As layer is 6 nm, and the Al y Ga 1-y The thickness of the As layer is 8 nm, and the MQW layer is not intentionally doped.
7. A Vcsel structure for optimizing oxidation uniformity as claimed in claim 1, characterized in that: The lower confinement layer and the upper confinement layer are both made of AlGaAs material, and the Al content ranges from 20% to 40%; the thickness of the lower confinement layer and the upper confinement layer are both 90-120nm, the doping element of the lower confinement layer is Si, and the doping element of the upper confinement layer is C.
8. A method for preparing a Vcsel structure with optimized oxidation uniformity as claimed in any one of claims 1 to 7, characterized in that: include: growing a buffer layer on the substrate; Growing an N-type DBR reflective layer on the buffer layer; Growing a lower confinement layer on the N-type DBR reflective layer; growing a MQW layer on the lower confinement layer; growing an upper confinement layer on the MQW layer; A first epitaxial layer is grown on the upper confinement layer, wherein the first epitaxial layer is Al with tensile stress. x Ga 1-x As y P 1-y Epitaxial layer, wherein 0≤x≤0.8, 0.1≤y≤0.3; growing an oxide layer on the first epitaxial layer; Growing a P-type DBR reflective layer on the oxide layer; An ohmic contact layer is grown on the P-type DBR reflective layer.
9. A method for preparing a Vcsel structure with optimized oxidation uniformity as claimed in claim 8, characterized in that: A second epitaxial layer is grown between the oxide layer and the P-type DBR reflective layer, and the structure and material composition of the second epitaxial layer are the same as those of the first epitaxial layer.
10. The method for preparing a Vcsel structure with optimized oxidation uniformity according to claim 8, characterized in that: After the ohmic contact layer is grown, the Vcsel structure is placed in an oxidation furnace for wet oxidation. The temperature of the oxidation furnace is 420°C, the water temperature is 95°C, the nitrogen flow rate is 1.5L / min, and the oxidation time is 30min.