Preparation method of high-speed vertical-cavity surface-emitting laser and high-speed vertical-cavity surface-emitting laser

Abstract

The invention provides a high-speed vertical-cavity surface-emitting laser preparation method and a high-speed vertical-cavity surface-emitting laser, and relates to the technical field of lasers, and the method comprises the steps: providing an epitaxial structure which comprises a substrate, a lower Bragg reflector and an active region, the top surface of the active region is provided with a first region, and a current expansion layer is formed on the first region; the substrate comprises a second area which is not covered by the lower Bragg reflector; forming a first dielectric film on the epitaxial structure; etching the first dielectric film above the current expansion layer to obtain a first window; etching the first dielectric film above the second area to obtain a second window; forming a first electrode in the first window; forming a second electrode in the second window; an upper dielectric Bragg reflector is arranged above the first electrode, and a plurality of photonic crystal air holes extending downwards are formed in the top surface of the upper dielectric Bragg reflector; and the depths of the photonic crystal air holes are gradually increased along the direction from the center of the upper dielectric Bragg reflector to the circumferential outer side of the upper dielectric Bragg reflector.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a method for preparing a high-speed vertical cavity surface emitting laser and the high-speed vertical cavity surface emitting laser. Background Art

[0002] Vertical-cavity surface-emitting lasers (VCSELs), as an important semiconductor laser, are widely used in 3D sensing, LiDAR, laser lighting, and optical communications due to their advantages such as low threshold current, high modulation rate, and ease of 2D integration. In optical communications, to meet the demands of high-speed data transmission, VCSELs require high modulation rates. Oxide-confined VCSELs can effectively increase this rate by reducing the oxide aperture diameter. However, to achieve mode stability, the oxide aperture is typically designed with an asymmetric shape. When forming small asymmetric oxide apertures, whether using a large substrate off-angle or controlling the surface morphology, the resulting oxide apertures will exhibit singularities at specific locations due to process or crystal material characteristics. At these singularities, the oxide aperture morphology exhibits abrupt changes, rather than a smooth, curved morphology. Due to current crowding, the current concentrates more at the oxide aperture singularity, resulting in excessive current density and a sharp temperature increase at the singularity, seriously impacting device reliability. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-speed vertical cavity surface emitting laser preparation method and a high-speed vertical cavity surface emitting laser, so as to alleviate the technical problems of poor reliability and slow modulation rate of existing lasers.

[0004] In a first aspect, the present invention provides a method for preparing a high-speed vertical cavity surface emitting laser, comprising: Step S10. Providing an epitaxial structure, the epitaxial structure comprising a substrate, a lower Bragg reflector, and an active region arranged in order from bottom to top, wherein a top surface of the active region comprises a first region, a current spreading layer is formed on the first region; the substrate comprises a second region not covered by the lower Bragg reflector; Step S20: forming a first dielectric film on the entire top surface of the epitaxial structure, with the current spreading layer and the second region both covered by the first dielectric film; etching the first dielectric film above the current spreading layer to form a first window, the first window being annular; and etching the first dielectric film above the second region to form a second window; Step S30. forming a first electrode in the first window; forming a second electrode in the second window; Step S40. Disposing an upper dielectric Bragg reflector above the first electrode, wherein the projection of the edge of the upper dielectric Bragg reflector on the first dielectric film is located inside the outer ring edge of the first window and outside the inner ring edge of the first window; Step S50 . Form a plurality of downwardly extending photonic crystal air holes on the top surface of the upper dielectric Bragg reflector; and the depths of the photonic crystal air holes gradually increase from the center of the upper dielectric Bragg reflector toward the circumferential outer side thereof.

[0005] Furthermore, there is an unprocessed hole area at the center of the upper dielectric Bragg reflector, and the diameter D of the unprocessed hole area ranges from 3um to 10um.

[0006] Furthermore, the shape of the inner ring edge of the first window is the same as the projection shape of the unprocessed hole area on the first dielectric film; The area of the inner edge of the first window is greater than or equal to the area of the projection of the unprocessed hole region on the first dielectric film; and / or, The shape of the unprocessed hole area is equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

[0007] Furthermore, in the top surface of the upper dielectric Bragg reflector, the duty cycle of the photonic crystal air hole is in the range of 0.3-0.7; and / or, The depth h of the photonic crystal air hole is in the range of 50 nm to 500 nm; and / or, The lattice constant of the photonic crystal air hole has a value range of 1 μm to 10 μm.

[0008] Furthermore, the method further includes the following steps performed between steps S10 and S20: S11. Ion implantation, wherein the ion implantation area includes the first area and an area of the current spreading layer outside the area with a length L from the center of the current spreading layer.

[0009] Furthermore, the epitaxial structure has a first end side and a second end side that are oppositely arranged, and the first region and the second region are arranged in sequence from the first end side toward the second end side; Also included are the steps performed between steps S20 and S30: Step S21. Depositing and curing a first colloid structure on the first dielectric film within a first lateral range; wherein the first lateral range is: in the lateral direction, the area between the first end side and the current spreading layer; Step S22. Depositing and curing a second dielectric film in a second lateral range; wherein the second lateral range is: the area between the first end side and the first window in the lateral direction; In the step S30 , a portion of the first electrode extends toward the first end side and covers the second dielectric film.

[0010] Furthermore, the epitaxial structure has a first end side and a second end side that are oppositely arranged, and the first region and the second region are arranged in sequence from the first end side toward the second end side; Also included are the steps performed between steps S20 and S30: Step S23. Depositing and curing a second colloid structure on the first dielectric film above the second region, wherein the second colloid structure has a avoidance groove corresponding to the position of the second window; Step S24. Depositing and curing a third dielectric film on the top surface of the second colloid structure, the inner wall of the avoidance groove, and the inner wall of the second window; In the step S30 , the second electrode covers the third dielectric film.

[0011] In a second aspect, the present invention provides a high-speed vertical cavity surface emitting laser, comprising: an epitaxial structure, a first dielectric film, and an upper dielectric Bragg reflector; the epitaxial structure comprises a substrate, a lower Bragg reflector, and an active region arranged in sequence from bottom to top, wherein the top surface of the active region has a first region; the substrate includes a second region not covered by the lower Bragg reflector; A first conductive structure is provided in the first region; the first conductive structure includes a ring structure; The first dielectric film covers the first region, the second region, and a portion of the first conductive structure; a first window is provided on the first dielectric film to avoid the annular structure, the first window is annular, and the annular structure is located inside the first window; a second window is provided on the first dielectric film, the second window is located on top of the second region, and a second electrode is provided in the second window to contact the second region; The upper dielectric Bragg reflector is arranged above the first dielectric film, and the projection of the edge of the upper dielectric Bragg reflector on the first dielectric film is located on the inner side of the outer ring edge of the first window and on the outer side of the inner ring edge of the first window; the top surface of the upper dielectric Bragg reflector is provided with a plurality of downwardly extending photonic crystal air holes; and the depth of the photonic crystal air holes gradually increases along the direction from the center of the upper dielectric Bragg reflector toward its circumferential outer side.

[0012] Furthermore, there is an unprocessed hole area at the center of the upper dielectric Bragg reflector, and the diameter D of the unprocessed hole area ranges from 3um to 10um.

[0013] Furthermore, the shape of the inner ring edge of the first window is the same as the projection shape of the unprocessed hole area on the first dielectric film; The area of the inner edge of the first window is greater than or equal to the area of the projection of the unprocessed hole region on the first dielectric film; and / or, The shape of the unprocessed hole area is equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

[0014] Furthermore, in the top surface of the upper dielectric Bragg reflector, the duty ratio of the photonic crystal air hole is in the range of 0.3-0.7 photonic crystal air holes; and / or, The depth h of the photonic crystal air hole is in the range of 50 nm to 500 nm; and / or, The lattice constant of the photonic crystal air hole has a value range of 1 μm to 10 μm.

[0015] Furthermore, the first dielectric film includes a covering portion located outside the annular outer edge of the first window; A portion of the first region located below the covering portion has implanted ions.

[0016] Furthermore, the high-speed vertical cavity surface emitting laser has a first end side and a second end side that are arranged opposite to each other, and the first region and the second region are arranged in sequence from the first end side toward the second end side; A first colloid structure is provided on the first dielectric film within a first lateral range; wherein the first lateral range is: in the lateral direction, the area between the first end side and the current spreading layer; The top surface of the first colloid structure and the first dielectric film between the first window and the first colloid structure are both covered with a second dielectric film; The first conductive structure includes a conductive layer connected to the annular structure, extending toward the first end side, and covering the second dielectric film. The conductive layer and the annular structure form a first electrode.

[0017] Furthermore, the high-speed vertical cavity surface emitting laser has a first end side and a second end side that are arranged opposite to each other, and the first region and the second region are arranged in sequence from the first end side toward the second end side; A second colloid structure is provided on the first dielectric film above the second area where no second window is provided, and the second colloid structure has an avoidance groove corresponding to the position of the second window; A third dielectric film is provided on the top surface of the second colloid structure, the inner wall of the avoidance groove and the inner wall of the second window; The second electrode covers the third dielectric film.

[0018] The present invention has at least the following advantages or beneficial effects: The method for preparing a high-speed vertical cavity surface emitting laser provided by the present invention comprises: step S10. providing an epitaxial structure, the epitaxial structure comprising a substrate, a lower Bragg reflector and an active region arranged in sequence from bottom to top, the top surface of the active region comprising a first region, a current spreading layer being formed on the first region; the substrate comprising a second region not covered by the lower Bragg reflector; step S20. forming a first dielectric film on the entire top surface of the epitaxial structure, the current spreading layer and the second region being both covered by the first dielectric film; etching the first dielectric film above the current spreading layer to obtain a first window, the first window being in a ring shape; etching the first dielectric film above the second region The first dielectric film is etched to obtain a second window; step S30. A first electrode is formed in the first window; a second electrode is formed in the second window; step S40. An upper dielectric Bragg reflector is arranged above the first electrode, and the projection of the edge of the upper dielectric Bragg reflector on the first dielectric film is located on the inner side of the outer ring edge of the first window and on the outer side of the inner ring edge of the first window; step S50. A plurality of downwardly extending photonic crystal air holes are formed on the top surface of the upper dielectric Bragg reflector; and the depth of the photonic crystal air holes gradually increases from the center of the upper dielectric Bragg reflector toward its circumferential outer side.

[0019] In the process of preparing a high-speed vertical cavity surface emitting laser using the above method, the first window and the second window are formed by etching, and there is no need to introduce oxidation limiting holes to laterally limit light and electricity. The stress introduced by the oxidation process and the oxidation hole singularity are avoided, thereby alleviating the current crowding effect and improving the reliability of the device. In addition, the prepared high-speed vertical cavity surface emitting laser removes the epitaxial Bragg reflector grown above the epitaxial structure of the traditional high-speed vertical cavity surface emitting laser. In the existing technology, after adopting the epitaxial Bragg reflector solution, it is impossible to prepare the electrode under the epitaxial Bragg reflector, and the circuit cannot avoid the influence of the series resistance brought by the Bragg reflector. In this embodiment, different from the above solution, a dielectric Bragg reflector solution is adopted to achieve current path optimization. Specifically, the upper dielectric Bragg reflector is arranged on the first dielectric film, and the current injected by the first electrode directly enters the active area through the current expansion layer, thereby reducing the parasitic resistance of the device and improving the high-speed modulation characteristics of the device. In the upper dielectric Bragg reflector, the optical mode confinement effect is achieved by forming a photonic crystal air hole, and the depth of the photonic crystal air hole gradually decreases from the periphery to the center, thereby forming a distribution in which the equivalent refractive index gradually increases from the outside to the inside, thereby achieving the convergence effect of the light field and reducing the divergence angle of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser after executing step S1 in an embodiment of the present invention; Figure 2 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S2 is executed; Figure 3 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S3 is executed; Figure 4 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S4 is executed; Figure 5 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S11 is executed; Figure 6 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S20 is executed; Figure 7 A schematic diagram of the steps S21 and S23 of the method for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after execution; Figure 8 A schematic diagram illustrating the steps S22 and S24 of the method for manufacturing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after execution; Figure 9 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S30 is executed; Figure 10 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S40 is executed; Figure 11 A schematic diagram of the process for preparing a high-speed vertical cavity surface emitting laser according to an embodiment of the present invention after step S50 is executed; Figure 12 A top view after executing step S50 in the method for manufacturing a high-speed vertical cavity surface emitting laser provided by an embodiment of the present invention (the unprocessed area is a circle); Figure 13This is a top view after step S50 is executed in the method for manufacturing a high-speed vertical cavity surface emitting laser provided by an embodiment of the present invention (the unprocessed area is a double circle).

[0022] Icons: 1-substrate; 2-lower Bragg reflector; 3-active area; 4-current spreading layer; 5-first region; 6-second region; 7-ion implantation region; 8-first end side; 9-second end side; 10-first lateral range; 11-first colloidal structure; 12-second lateral range; 13-second dielectric film; 14-second colloidal structure; 15-avoidance groove; 16-third dielectric film; 17-first dielectric film; 18-first window; 19-second window; 20-first electrode; 201-ring structure; 202-conductive layer; 21-second electrode; 22-upper dielectric Bragg reflector; 221-unprocessed hole region; 23-photonic crystal air hole. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0026] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on the positions shown in the accompanying drawings, or the positions or locations in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0028] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0029] The method for preparing a high-speed vertical cavity surface emitting laser provided by the present invention comprises: like Figure 4 As shown, step S10. An epitaxial structure is provided, which includes a substrate 1, a lower Bragg reflector 2 and an active area 3 arranged in sequence from bottom to top, the top surface of the active area 3 has a first area 5, and a current spreading layer 4 is formed on the first area 5; the substrate 1 includes a second area 6 not covered by the lower Bragg reflector 2.

[0030] Specifically, the epitaxial structure can be prepared through steps S1 to S4: like Figures 1-4 As shown, step S1. Using substrate 1 as a base, a lower Bragg reflector 2 and an active area 3 are sequentially grown on substrate 1. The material of substrate 1 includes but is not limited to GaN, GaA, InP and the like.

[0031] Step S2 . Depositing a current spreading layer 4 on the upper surface of the active area 3 .

[0032] Step S3: Etching the current spreading layer 4 and the active area 3 to remove the current spreading layer 4 and the active area 3 outside the first area 5, and the remaining first area 5 forms a P-electrode mesa.

[0033] Step S4: etching the epitaxial structure from which the current spreading layer 4 and a portion of the active area 3 have been removed again, etching away a portion of the lower Bragg reflector 2 until reaching the substrate 1 to form a second region 6, which is an N-electrode mesa.

[0034] like Figure 5 As shown, the preparation method further includes the following steps between steps S10 and S20: S11. Ion implantation, wherein the ion implantation region 7 includes the first region 5 and a region of the current spreading layer 4 outside the region with a length L from the center of the current spreading layer 4.

[0035] Not all of the first region 5 is the ion-implanted region 7 because step S11 is performed after step S10. That is, before the ion implantation, the first region 5 is already covered by the current spreading layer 4. Therefore, the first region 5 covered by the current spreading layer 4 does not form the ion-implanted region 7. Before the ion implantation, a baffle can be used to cover the second region 6 and the region of the current spreading layer 4 within a length L from the center of the current spreading layer 4. Ion implantation is then performed, so that the first region 5 and the portion of the current spreading layer 4 outside the length L from the center of the current spreading layer 4 are implanted with ions. The implanted ions may be hydrogen, helium, or boron. After the ion implantation, the ion-implanted region 7 becomes non-conductive, achieving lateral electrical isolation.

[0036] like Figure 6 As shown, step S20. A first dielectric film 17 is formed on the entire top surface of the epitaxial structure, and the current spreading layer 4 and the second region 6 are both covered by the first dielectric film 17; the first dielectric film 17 above the current spreading layer 4 is etched to obtain a first window 18, and the first window 18 is ring-shaped; the first dielectric film 17 above the second region 6 is etched to obtain a second window 19.

[0037] A first dielectric film 17 is deposited and formed on the top surface of the epitaxial structure provided in step S10. A first annular window 18 is formed in the first dielectric film 17 above the current spreading layer 4, and a second window 19 is formed in the first dielectric film 17 above the second region 6 of the substrate 1 by photolithography. The first window 18 and the second window 19 can be formed by etching simultaneously or sequentially.

[0038] Etching the first and second windows 18, 19 eliminates the need for oxide-limiting holes to laterally confine light and electricity, avoiding the stress and oxide-hole singularities introduced by the oxidation process. This mitigates current crowding and improves device reliability. Smooth-edged edges in the first and second windows 18, 19 address the oxide-hole singularity issue, mitigate current crowding, and improve reliability. The shape and size of the first window 18 can also be defined to define the optical gain region and optical mode distribution.

[0039] like Figure 7-Figure 8 As shown, for the convenience of explaining the structure, the epitaxial structure is assumed to have a first end side 8 (left side) and a second end side 9 (right side) relatively arranged, and the first region 5 and the second region 6 are arranged in sequence from the first end side 8 toward the second end side 9.

[0040] The method further comprises the steps performed between steps S20 and S30: Step S21. Deposit and solidify a first colloid structure 11 on the first dielectric film 17 within a first lateral extent 10; wherein the first lateral extent 10 is the region between the first end side 8 and the current spreading layer 4 in the lateral direction. Step S22. Deposit and solidify a second dielectric film 13 within a second lateral extent 12; wherein the second lateral extent 12 is the region between the first end side 8 and the first window 18 in the lateral direction.

[0041] By blocking at different positions, the first colloidal structure 11 and the second dielectric film 13 are deposited twice in succession to obtain the first colloidal structure 11. The material of the first colloidal structure 11 is generally a low dielectric constant material. The first electrode 20 and the substrate 1 are equivalent to the two poles of a flat plate capacitor. By increasing the distance between the first electrode 20 and the substrate 1 and reducing the dielectric constant of the material between them, the capacitance can be reduced, thereby reducing the parasitic parameters of the device.

[0042] The method may further include the following steps between steps S20 and S30: like Figure 7 As shown, step S23. depositing and curing the first dielectric film 17 above the second region 6 to obtain a second colloid structure 14, the second colloid structure 14 has a avoidance groove 15 corresponding to the position of the second window 19. Figure 8 As shown, step S24 , a third dielectric film 16 is deposited and cured on the top surface of the second colloid structure 14 , the inner wall of the avoidance groove 15 and the inner wall of the second window 19 .

[0043] Similarly, the second colloidal structure 14 is generally made of a low dielectric constant material. The second electrode 21 and the substrate 1 are equivalent to the two poles of a flat plate capacitor. By increasing the distance between the second electrode 21 and the substrate 1 and reducing the dielectric constant of the material between them, the capacitance can be reduced.

[0044] A relief groove 15 is formed on the second colloidal structure 14 by photolithography. The relief groove 15 is connected to the substrate 1. After the third dielectric film 16 is deposited, a portion of the third dielectric film 16 is removed by photolithography to ensure that the area of the substrate 1 corresponding to the second window 19 is not covered by the third dielectric film 16. The function of the third dielectric film 16 is to achieve electrical isolation and to wrap and protect the second colloidal structure 14.

[0045] like Figure 9 As shown, in step S30 , a first electrode 20 is formed in the first window 18 ; and a second electrode 21 is formed in the second window 19 .

[0046] First electrode 20 fills first window 18, with a portion of first electrode 20 extending outside first window 18 and covering second dielectric film 13, for connection to an external power source. Similarly, second electrode 21 fills second window 19, with a portion of second electrode 21 extending outside second window 19 and covering third dielectric film 16, for connection to an external power source.

[0047] like Figure 10 As shown, step S40. An upper dielectric Bragg reflector 22 is disposed above the first electrode 20. The projection of the edge of the upper dielectric Bragg reflector 22 on the first dielectric film 17 is located inside the outer ring edge of the first window 18 and outside the inner ring edge of the first window 18.

[0048] The prepared high-speed vertical cavity surface emitting laser removes the epitaxial Bragg reflector grown above the epitaxial structure of the traditional high-speed vertical cavity surface emitting laser. In this embodiment, the upper dielectric Bragg reflector 22 is arranged on the first dielectric film 17, which reduces the parasitic resistance of the device and improves the high-speed modulation characteristics of the device.

[0049] The materials of the upper dielectric Bragg reflector 22 include, but are not limited to, Si, SiO2, SiN, ITO, TiO, AlO, etc., and can be prepared by, but are not limited to, chemical vapor deposition, electron beam evaporation, magnetron sputtering, etc. The current spreading layer 4 can be grown epitaxially, or prepared by electron beam evaporation, magnetron sputtering, etc.

[0050] like Figure 11 As shown, step S50. A plurality of downwardly extending photonic crystal air holes 23 are formed on the top surface of the upper dielectric Bragg reflector 22; and the depth of the photonic crystal air holes 23 gradually increases from the center of the upper dielectric Bragg reflector 22 toward the circumferential outer side thereof.

[0051] In the upper dielectric Bragg reflector 22, an optical mode confinement effect is achieved by forming a photonic crystal air hole 23, and the depth of the photonic crystal air hole 23 gradually decreases from the periphery to the center, thereby forming a distribution in which the equivalent refractive index gradually increases from the outside to the inside, achieving a convergence effect of the light field and reducing the divergence angle of the device.

[0052] like Figure 12 As shown, there is an unprocessed hole region 221 at the center of the upper dielectric Bragg reflector 22. The diameter D of the unprocessed hole region 221 ranges from 3 μm to 10 μm. When the shape of the unprocessed hole region 221 is non-circular, the diameter D is converted by area.

[0053] The mode of the laser can be changed by changing the diameter D of the unprocessed hole area 221. As the diameter D increases, the device output mode changes from single mode to multi-mode.

[0054] The shape of the inner edge of the first window 18 is the same as the projection shape of the unprocessed hole area 221 on the first dielectric film 17 . The area of the inner edge of the first window 18 is greater than or equal to the projection area of the unprocessed hole area 221 on the first dielectric film 17 .

[0055] The advantage of the inner ring edge area of the first window 18 being greater than or equal to the projection area of the unprocessed hole area 221 on the first dielectric film 17 is that the actual gain area is increased, the gain area is ensured to be larger than the high reflectivity area, and the light output power is improved.

[0056] The shape of the unprocessed hole area 221 can be equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

[0057] By limiting the shape of the unetched area, the ability to control the optical mode is provided, and the high-speed capability can be improved by coupling between optical modes. For example, the shape of the unprocessed hole area 221 is equivalent to a single asymmetric pattern, such as an ellipse or a diamond, which can provide polarization control capability. If it is a pattern such as a double diamond or a double circle, such as Figure 13 As shown, the optical mode can be divided into two parts, and the high-speed modulation capability is improved by coupling the optical modes between the two parts.

[0058] It should be noted that when the shape of the unprocessed hole area 221 is a shape with vertex angles such as a rhombus or a double rhombus, in order to avoid the singularity problem, the rhombus and the double rhombus can be set with rounded vertex angles, that is, the vertex angles are chamfered.

[0059] like Figure 12 As shown, in the top surface of the upper dielectric Bragg reflector 22, the duty ratio b / a of the photonic crystal air hole 23 is in the range of 0.3-0.7. The larger the duty ratio, the stronger the refractive index guiding effect, where b is the diameter of the photonic crystal air hole 23 and a is the distance between the centers of the two most adjacent photonic crystal air holes 23.

[0060] The depth h of the photonic crystal air hole 23 ranges from 50 nm to 500 nm and does not exceed the thickness of the upper dielectric Bragg reflector 22 . The deeper the etching depth, the stronger the refractive index guiding effect.

[0061] The lattice constant of the photonic crystal air hole 23 ranges from 1 μm to 10 μm. The larger the lattice constant, the easier it is to prepare, but the worse the modulation effect.

[0062] This proposal introduces a method for preparing a laser, which grows a lower dielectric Bragg reflector, an active region 3, and a current expansion layer 4 on an n-type substrate 1, and then photolithographically deposits and lifts off a P-type current injection hole, i.e., a first window 18, on the current expansion layer 4, to obtain a current injection hole with a smooth edge. By designing the size and shape of the current injection hole, it can be used to limit the lateral diffusion of the current and define the optical gain region, thereby affecting the optical mode and increasing the rate. Subsequently, an upper dielectric Bragg reflector 22 is deposited above the current expansion layer 4 of the current injection hole to provide the high reflectivity required for lasing, and periodic photonic crystal air holes 23 are etched on the upper dielectric Bragg reflector 22 to achieve optical lateral confinement. The etching depth of the photonic crystal air hole 23 gradually decreases from the outside to the inside, so that the equivalent refractive index gradually increases from the outside to the inside, forming a converging effect on the light field.

[0063] Beneficial effects: 1. The current injection holes (first window 18 and second window 19) are prepared by photolithography, deposition, and lift-off, which can obtain a smooth-edged current injection morphology, solve the singularity problem of the oxide hole, alleviate the current crowding effect, and improve reliability; 2. No epitaxial Bragg reflector is provided, and the current injection hole is set below the upper dielectric Bragg reflector 22, so that the current can flow directly from the first electrode 20 into the active area 3, solving the problem of large parasitic parameters of the traditional laser epitaxial P-type Bragg reflector. At the same time, the shape and size of the current injection hole can be defined to define the optical gain region and optical mode distribution. 3. By etching periodic photonic crystal air holes 23 on the upper dielectric Bragg reflector 22, and gradually decreasing the etching depth from the outside to the inside, a trapezoidal distribution of equivalent refractive index can be formed, thereby achieving a convergence effect on the light field; 4. By etching periodic photonic crystal air holes 23 on the upper dielectric Bragg reflector 22, a weak refractive index guide similar to that of an optical fiber is formed, which confines the light field to the non-etched area at the center of the upper dielectric Bragg reflector 22, achieving a lateral optical confinement effect. By designing and controlling the size and distribution of the etched air holes, a non-circular equivalent confinement area can be achieved, enabling mode selection. 5. Etching the first window 18 and the second window 19 to form optical confinement, and preparing the current loop to directly form current confinement, thereby removing the oxidation confinement hole and avoiding defects and stress introduced by the oxidation process.

[0064] The high-speed vertical cavity surface emitting laser provided by the present invention can be obtained by the above-mentioned preparation method. Figures 1-11 As shown, the laser includes: an epitaxial structure, a first dielectric film 17 and an upper dielectric Bragg reflector 22 .

[0065] The epitaxial structure includes a substrate 1, a lower Bragg reflector 2, and an active area 3 arranged in order from bottom to top. The top surface of the active area 3 has a first region 5, which does not completely cover the entire lower Bragg reflector 2. The substrate 1 includes a second region 6 not covered by the lower Bragg reflector 2.

[0066] A first conductive structure is provided in the first region 5 , and the first conductive structure may include a current spreading layer 4 and a first electrode 20 . The first conductive structure includes an annular structure 201 , and the annular structure 201 forms the first electrode 20 .

[0067] The first dielectric film 17 covers the first region 5, the second region 6, and a portion of the first conductive structure. A first window 18 is provided on the first dielectric film 17 to avoid the annular structure 201. The first window 18 is annular, and the annular structure 201 is located within the first window 18. A second window 19 is provided on the first dielectric film 17, located on top of the second region 6. A second electrode 21 is disposed within the second window 19, contacting the second region 6.

[0068] In this embodiment, the first window 18 and the second window 19 are formed by etching, and there is no need to introduce oxidation limiting holes to laterally limit light and electricity, thereby avoiding the stress introduced by the oxidation process and the oxidation hole singularity, thereby alleviating the current crowding effect and improving the reliability of the device.

[0069] The upper dielectric Bragg reflector 22 is disposed above the first dielectric film 17 , and the projection of the edge of the upper dielectric Bragg reflector 22 on the first dielectric film 17 is located inside the outer edge of the first window 18 and outside the inner edge of the first window 18 .

[0070] The prepared high-speed vertical cavity surface emitting laser removes the epitaxial Bragg reflector grown above the epitaxial structure of the traditional high-speed vertical cavity surface emitting laser. In this embodiment, the upper dielectric Bragg reflector 22 is arranged on the first dielectric film 17, which reduces the parasitic resistance of the device and improves the high-speed modulation characteristics of the device.

[0071] A plurality of downwardly extending photonic crystal air holes 23 are provided on the top surface of the upper dielectric Bragg reflector 22 . The depth of the photonic crystal air holes 23 gradually increases from the center of the upper dielectric Bragg reflector 22 toward the circumferential outer side thereof.

[0072] In the upper dielectric Bragg reflector 22, an optical mode confinement effect is achieved by forming a photonic crystal air hole 23, and the depth of the photonic crystal air hole 23 gradually decreases from the periphery to the center, thereby forming a distribution in which the equivalent refractive index gradually increases from the outside to the inside, achieving a convergence effect of the light field and reducing the divergence angle of the device.

[0073] There is an unprocessed hole region 221 in the center of the upper dielectric Bragg reflector 22. The diameter D of the unprocessed hole region 221 ranges from 3 μm to 10 μm. By changing the diameter D of the unprocessed hole region 221, the laser mode can be changed to form a single-mode or multi-mode laser.

[0074] The shape of the inner edge of the first window 18 is the same as the projection shape of the unprocessed hole area 221 on the first dielectric film 17 ; the area of the inner edge of the first window 18 is greater than or equal to the projection area of the unprocessed hole area 221 on the first dielectric film 17 .

[0075] The advantage of the inner ring edge area of the first window 18 being greater than or equal to the projection area of the unprocessed hole area 221 on the first dielectric film 17 is that the actual gain area is increased, the gain area is ensured to be larger than the high reflectivity area, and the light output power is improved.

[0076] The shape of the unprocessed hole area 221 is equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

[0077] By restricting the shape of the unetched area, optical mode control is enhanced, while high-speed capability is also improved by promoting coupling between optical modes. For example, the shape of the unprocessed hole area 221 is equivalent to a single asymmetric shape, such as an ellipse or a diamond, which can provide polarization control. A shape such as a double diamond or a double circle can split the optical mode into two parts, and through coupling between the two optical modes, high-speed modulation capability is improved.

[0078] like Figure 12 As shown, in the top surface of the upper dielectric Bragg reflector 22, the duty ratio b / a of the photonic crystal air hole 23 is in the range of 0.3-0.7. The larger the duty ratio, the stronger the refractive index guiding effect, where b is the diameter of the photonic crystal air hole 23 and a is the distance between the centers of the two most adjacent photonic crystal air holes 23.

[0079] The depth h of the photonic crystal air hole 23 ranges from 50 nm to 500 nm and does not exceed the thickness of the upper dielectric Bragg reflector 22 . The deeper the etching depth, the stronger the refractive index guiding effect.

[0080] The lattice constant of the photonic crystal air hole 23 ranges from 1 μm to 10 μm. The larger the lattice constant, the easier it is to prepare, but the worse the modulation effect.

[0081] The first dielectric film 17 includes a covering portion located outside the annular outer edge of the first window 18 ; a portion of the first region 5 located below the covering portion has implanted ions.

[0082] The implanted ions can be hydrogen, helium or boron. After ion implantation, the implanted area becomes non-conductive, achieving lateral electrical isolation.

[0083] The high-speed vertical cavity surface emitting laser has a first end side 8 and a second end side 9 that are oppositely arranged. From the first end side 8 toward the second end side 9, the first region 5 and the second region 6 are arranged in sequence.

[0084] A first colloid structure 11 is disposed on a first dielectric film 17 within a first lateral range 10. The first lateral range 10 includes the region between the first end side 8 and the current spreading layer 4 in the lateral direction. The top surface of the first colloid structure 11 and the portion of the first dielectric film 17 between the first window 18 and the first colloid structure 11 are covered with a second dielectric film 13. The first conductive structure includes a conductive layer 202 connected to the annular structure 201, extending toward the first end side 8, and covering the second dielectric film 13. The conductive layer 202 and the annular structure 201 form a first electrode 20.

[0085] By performing shielding at different positions, the first colloid structure 11 and the second dielectric film 13 are deposited twice in succession to obtain the first colloid structure 11 and the second dielectric film 13 , thereby reducing the parasitic parameters of the device.

[0086] A second colloid structure 14 is provided on the first dielectric film 17 above the second region 6 , where the second window 19 is not provided. The second colloid structure 14 has a relief groove 15 corresponding to the position of the second window 19 . A third dielectric film 16 is provided on the top surface of the second colloid structure 14 , the inner wall of the relief groove 15 , and the inner wall of the second window 19 . A second electrode 21 covers the third dielectric film 16 .

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-speed vertical cavity surface emitting laser, characterized in that: include: Step S10. Providing an epitaxial structure, the epitaxial structure comprising a substrate (1), a lower Bragg reflector (2), and an active area (3) arranged in sequence from bottom to top, the top surface of the active area (3) comprising a first area (5), a current spreading layer (4) being formed on the first area (5); the substrate (1) comprising a second area (6) not covered by the lower Bragg reflector (2); Step S20. Forming a first dielectric film (17) on the entire top surface of the epitaxial structure, wherein the current spreading layer (4) and the second region (6) are both covered by the first dielectric film (17); etching the first dielectric film (17) above the current spreading layer (4) to obtain a first window (18), wherein the first window (18) is ring-shaped; etching the first dielectric film (17) above the second region (6) to obtain a second window (19); Step S30: forming a first electrode (20) in the first window (18); forming a second electrode (21) in the second window (19); Step S40. An upper dielectric Bragg reflector (22) is provided above the first electrode (20), wherein the projection of the edge of the upper dielectric Bragg reflector (22) on the first dielectric film (17) is located inside the outer ring edge of the first window (18) and outside the inner ring edge of the first window (18); Step S50: forming a plurality of downwardly extending photonic crystal air holes (23) on the top surface of the upper dielectric Bragg reflector (22); and the depth of the photonic crystal air holes (23) gradually increases along the direction from the center of the upper dielectric Bragg reflector (22) toward the circumferential outer side thereof.

2. The method for preparing a high-speed vertical cavity surface emitting laser according to claim 1, characterized in that: An unprocessed hole region (221) exists at the center of the upper dielectric Bragg reflector (22), and a diameter D of the unprocessed hole region (221) has a value range of 3 μm to 10 μm.

3. The method for preparing a high-speed vertical cavity surface emitting laser according to claim 2, characterized in that: The shape of the inner ring edge of the first window (18) is the same as the projection shape of the unprocessed hole area (221) on the first dielectric film (17); The area of the inner ring edge of the first window (18) is greater than or equal to the area of the projection of the unprocessed hole area (221) on the first dielectric film (17); and / or, The shape of the unprocessed hole area (221) is equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

4. The method for preparing a high-speed vertical cavity surface emitting laser according to claim 1, wherein: In the top surface of the upper dielectric Bragg reflector (22), the duty cycle of the photonic crystal air hole (23) is in the range of 0.3-0.7; and / or, The depth h of the photonic crystal air hole (23) ranges from 50 nm to 500 nm; and / or, The lattice constant of the photonic crystal air hole (23) has a value range of 1 μm to 10 μm.

5. The method for preparing a high-speed vertical cavity surface emitting laser according to any one of claims 1 to 4, characterized in that: Also included are the steps performed between steps S10 and S20: S11. Ion implantation, wherein the ion implantation region (7) includes the first region (5) and a region in the current spreading layer (4) that is outside the center of the current spreading layer (4) and is at a distance of L.

6. The method for preparing a high-speed vertical cavity surface emitting laser according to any one of claims 1 to 4, characterized in that: The epitaxial structure has a first end side (8) and a second end side (9) that are arranged opposite to each other, and the first region (5) and the second region (6) are arranged in sequence from the first end side (8) toward the second end side (9); Also included are the steps performed between steps S20 and S30: Step S21. Depositing and curing a first colloid structure (11) on the first dielectric film (17) within a first lateral range (10); wherein the first lateral range (10) is: in the lateral direction, the area between the first end side (8) and the current spreading layer (4); Step S22. Depositing and curing a second dielectric film (13) within a second lateral range (12); wherein the second lateral range (12) is: in the lateral direction, the area between the first end side (8) and the first window (18); In the step S30, a portion of the first electrode (20) extends toward the first end side (8) and covers the second dielectric film (13).

7. The method for preparing a high-speed vertical cavity surface emitting laser according to any one of claims 1 to 4, characterized in that: The epitaxial structure has a first end side (8) and a second end side (9) that are arranged opposite to each other, and the first region (5) and the second region (6) are arranged in sequence from the first end side (8) toward the second end side (9); Also included are the steps performed between steps S20 and S30: Step S23. Depositing and solidifying the first dielectric film (17) above the second region (6) to obtain a second colloid structure (14), wherein the second colloid structure (14) has an avoidance groove (15) corresponding to the position of the second window (19); Step S24. Depositing and solidifying a third dielectric film (16) on the top surface of the second colloid structure (14), the inner wall of the avoidance groove (15), and the inner wall of the second window (19); In the step S30, the second electrode (21) covers the third dielectric film (16).

8. A high-speed vertical cavity surface emitting laser, characterized in that: include: An epitaxial structure, a first dielectric film (17) and an upper dielectric Bragg reflector (22); the epitaxial structure comprises a substrate (1), a lower Bragg reflector (2) and an active area (3) arranged in sequence from bottom to top, the top surface of the active area (3) having a first area (5); the substrate (1) comprises a second area (6) not covered by the lower Bragg reflector (2); A first conductive structure is provided in the first area (5); the first conductive structure comprises a ring structure (201); The first dielectric film (17) covers the first region (5), the second region (6) and part of the first conductive structure; a first window (18) is provided on the first dielectric film (17) to avoid the annular structure (201); the first window (18) is annular, and the annular structure (201) is located inside the first window (18); a second window (19) is provided on the first dielectric film (17), the second window (19) is located on the top of the second region (6), and a second electrode (21) in contact with the second region (6) is provided in the second window (19); The upper dielectric Bragg reflector (22) is arranged above the first dielectric film (17), and the projection of the edge of the upper dielectric Bragg reflector (22) on the first dielectric film (17) is located on the inner side of the outer ring edge of the first window (18) and on the outer side of the inner ring edge of the first window (18); the top surface of the upper dielectric Bragg reflector (22) is provided with a plurality of photonic crystal air holes (23) extending downward; and the depth of the photonic crystal air holes (23) gradually increases along the direction from the center of the upper dielectric Bragg reflector (22) toward the circumferential outer side thereof.

9. The high-speed vertical cavity surface emitting laser according to claim 8, characterized in that: An unprocessed hole region (221) exists at the center of the upper dielectric Bragg reflector (22), and a diameter D of the unprocessed hole region (221) has a value range of 3 μm to 10 μm.

10. The high-speed vertical cavity surface emitting laser according to claim 9, characterized in that: The shape of the inner ring edge of the first window (18) is the same as the projection shape of the unprocessed hole area (221) on the first dielectric film (17); The area of the inner ring edge of the first window (18) is greater than or equal to the area of the projection of the unprocessed hole area (221) on the first dielectric film (17); and / or, The shape of the unprocessed hole area (221) is equivalent to a circle, an ellipse, a diamond, a double diamond, or a double circle.

11. The high-speed vertical cavity surface emitting laser according to claim 8, characterized in that: In the top surface of the upper dielectric Bragg reflector (22), the duty cycle of the photonic crystal air hole (23) is in the range of 0.3-0.7 photonic crystal air hole (23); and / or, The depth h of the photonic crystal air hole (23) ranges from 50 nm to 500 nm; and / or, The lattice constant of the photonic crystal air hole (23) has a value range of 1 μm to 10 μm.

12. The high-speed vertical cavity surface emitting laser according to claim 11, characterized in that: The first dielectric film (17) includes a covering portion located outside the annular outer edge of the first window (18); In the first region (5), a portion located below the covering portion has implanted ions.

13. The high-speed vertical cavity surface emitting laser according to any one of claims 8 to 12, characterized in that: The high-speed vertical cavity surface emitting laser has a first end side (8) and a second end side (9) that are arranged opposite to each other, and the first region (5) and the second region (6) are arranged in sequence from the first end side (8) toward the second end side (9); A first colloid structure (11) is provided on a first dielectric film (17) within a first lateral range (10); wherein the first lateral range (10) is: in the lateral direction, an area between the first end side (8) and the current spreading layer (4); The top surface of the first colloid structure (11) and the first dielectric film (17) between the first window (18) and the first colloid structure (11) are both covered with a second dielectric film (13); The first conductive structure comprises a conductive layer (202) connected to the annular structure (201), extending toward the first end side (8) and covering the second dielectric film (13); the conductive layer (202) and the annular structure (201) form a first electrode (20).

14. The high-speed vertical cavity surface emitting laser according to any one of claims 8 to 12, characterized in that: The high-speed vertical cavity surface emitting laser has a first end side (8) and a second end side (9) that are arranged opposite to each other, and the first region (5) and the second region (6) are arranged in sequence from the first end side (8) toward the second end side (9); A second colloid structure (14) is provided on the first dielectric film (17) above the second region (6) where no second window (19) is provided, and the second colloid structure (14) has an avoidance groove (15) corresponding to the position of the second window (19); A third dielectric film (16) is provided on the top surface of the second colloid structure (14), the inner wall of the avoidance groove (15), and the inner wall of the second window (19); The second electrode (21) covers the third dielectric film (16).

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