Fabrication method and high-speed vertical-cavity surface-emitting laser

Abstract

This invention provides a method for fabricating a high-speed vertical-cavity surface-emitting laser (VCSEL) and the high-speed VCSEL itself, relating to the technical field of lasers. The method includes: providing an epitaxial structure, including a substrate, a lower Bragg mirror, and an active region, wherein the top surface of the active region has a first region, and a current spreading layer is formed on the first region; the substrate includes a second region not covered by the lower Bragg mirror; forming a first dielectric film on the epitaxial structure; etching the first dielectric film above the current spreading layer to obtain a first window; etching the first dielectric film above the second region to obtain a second window; forming a first electrode within the first window; forming a second electrode within the second window; and disposing an upper dielectric Bragg mirror above the first electrode, wherein a plurality of downwardly extending photonic crystal air holes are formed on its top surface; and the depth of the photonic crystal air holes gradually increases along the direction from the center of the upper dielectric Bragg mirror toward its circumferential outwards.

Description

Technical Field

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

[0002] Vertical-cavity surface-emitting lasers (VCSELs), as important semiconductor lasers, are widely used in 3D sensing, lidar, laser illumination, and optical communication due to their advantages such as low threshold current, high modulation rate, and ease of 2D integration. In optical communication, to meet the demands of high-speed data transmission, VCSELs require high modulation rates, and oxide-confined VCSELs can effectively improve the modulation rate by reducing the oxide aperture. However, to achieve mode stability, the oxide aperture is usually designed with an asymmetric shape. When forming small asymmetric oxide apertures, regardless of whether a large substrate off-center angle or controlled surface topography is used, the resulting oxide aperture will exhibit singularities at specific locations due to process or crystal material characteristics. The morphology of the oxide aperture at these singularities will change abruptly rather than following a smooth curve. Due to current congestion, more current will concentrate at the singularities of the oxide aperture, leading to excessively high current density and a sharp temperature rise, which severely impacts the reliability of the device. Summary of the Invention

[0003] The purpose of this invention is to provide a method for fabricating a high-speed vertical-cavity surface-emitting laser 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 fabricating a high-speed vertical-cavity surface-emitting laser, comprising:

[0005] Step S10. Provide an epitaxial structure, the epitaxial structure including a substrate, a lower Bragg mirror and an active region arranged sequentially from bottom to top, the top surface of the active region having a first region, on which a current spreading layer is formed; the substrate includes a second region not covered by the lower Bragg mirror;

[0006] Step S20. A first dielectric film is formed on the entire top surface of the epitaxial structure, and both the current spreading layer and the second region are covered by the first dielectric film; the first dielectric film above the current spreading layer is etched to obtain a first window, which is annular; the first dielectric film above the second region is etched to obtain a second window;

[0007] Step S30. Form a first electrode within the first window; form a second electrode within the second window;

[0008] Step S40. An upper dielectric Bragg reflector is disposed above the first electrode, wherein the projection of the edge of the upper dielectric Bragg reflector onto 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.

[0009] 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 along the direction from the center of the upper dielectric Bragg reflector toward its circumferential outward.

[0010] Furthermore, the upper dielectric Bragg reflector has an unprocessed hole region at its center, and the diameter D of the unprocessed hole region ranges from 3µm to 10µm.

[0011] Furthermore, the shape of the inner ring edge of the first window is the same as the projection shape of the unprocessed hole region on the first dielectric film;

[0012] The area of ​​the inner ring edge of the first window is greater than or equal to the area of ​​the projection of the unprocessed hole region onto the first dielectric film; and / or,

[0013] The shape of the unprocessed hole area is equivalent to a circle, an ellipse, a rhombus, a double rhombus, or a double circle.

[0014] Furthermore, in the top surface of the upper dielectric Bragg reflector, the duty cycle of the photonic crystal air hole ranges from 0.3 to 0.7; and / or,

[0015] The depth h of the air hole in the photonic crystal ranges from 50 nm to 500 nm; and / or,

[0016] The lattice constant of the air hole in the photonic crystal ranges from 1µm to 10µm.

[0017] Furthermore, it also includes the steps performed between steps S10 and S20:

[0018] S11. Ion implantation, wherein the ion implantation region includes a first region and a region in the current spreading layer that is a distance L from the center of the current spreading layer.

[0019] Furthermore, the extensional structure has a first end side and a second end side disposed opposite to each other, and the first region and the second region are disposed sequentially from the first end side toward the second end side;

[0020] It also includes the steps performed between steps S20 and S30:

[0021] Step S21. Deposit and cure a first colloidal structure on a first dielectric film within a first lateral range; wherein, the first lateral range is: the region between the first end side and the current spreading layer in the lateral direction;

[0022] Step S22. Deposit and solidify a second dielectric film within a second lateral range; wherein, the second lateral range is: the region between the first end side and the first window in the lateral direction;

[0023] In step S30, a portion of the first electrode extends toward the first end side and covers the second dielectric film.

[0024] Furthermore, the extensional structure has a first end side and a second end side disposed opposite to each other, and the first region and the second region are disposed sequentially from the first end side toward the second end side;

[0025] It also includes the steps performed between steps S20 and S30:

[0026] Step S23. A second colloidal structure is deposited and cured on a first dielectric film above the second region to obtain a second colloidal structure having a clearance groove corresponding to the position of the second window;

[0027] Step S24. A third dielectric film is deposited and cured on the top surface of the second colloidal structure, the inner wall of the clearance groove, and the inner wall of the second window to obtain a third dielectric film;

[0028] In step S30, the second electrode covers the third dielectric film.

[0029] 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 mirror; the epitaxial structure comprises a substrate, a lower Bragg mirror, and an active region arranged sequentially 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 mirror.

[0030] A first conductive structure is provided in the first region; the first conductive structure includes a ring structure.

[0031] 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 at the top of the second region, and a second electrode is provided inside the second window to contact the second region;

[0032] The upper dielectric Bragg reflector is disposed above the first dielectric film, and the projection of the edge of the upper dielectric Bragg reflector onto 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; 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 outward.

[0033] Furthermore, the upper dielectric Bragg reflector has an unprocessed hole region at its center, and the diameter D of the unprocessed hole region ranges from 3µm to 10µm.

[0034] Furthermore, the shape of the inner ring edge of the first window is the same as the projection shape of the unprocessed hole region on the first dielectric film;

[0035] The area of ​​the inner ring edge of the first window is greater than or equal to the area of ​​the projection of the unprocessed hole region onto the first dielectric film; and / or,

[0036] The shape of the unprocessed hole area is equivalent to a circle, an ellipse, a rhombus, a double rhombus, or a double circle.

[0037] Furthermore, in the top surface of the upper dielectric Bragg reflector, the duty cycle of the photonic crystal air hole ranges from 0.3 to 0.7 (photonic crystal air hole); and / or,

[0038] The depth h of the air hole in the photonic crystal ranges from 50 nm to 500 nm; and / or,

[0039] The lattice constant of the air hole in the photonic crystal ranges from 1µm to 10µm.

[0040] Furthermore, the first dielectric film includes a covering portion located outside the annular outer edge of the first window;

[0041] In the first region, the portion located below the covered portion has injected ions.

[0042] Furthermore, the high-speed vertical cavity surface-emitting laser has a first end side and a second end side arranged opposite to each other, and the first region and the second region are arranged sequentially from the first end side toward the second end side;

[0043] A first colloidal structure is disposed on a first dielectric film within a first lateral range; wherein, the first lateral range is: the region between the first end side and the current spreading layer in the lateral direction;

[0044] A second dielectric film is covered on the top surface of the first colloidal structure and on the first dielectric film between the first window and the first colloidal structure.

[0045] The first conductive structure includes a conductive layer that is connected to the annular structure, extends toward the first end side, and covers the second dielectric film, wherein the conductive layer and the annular structure form a first electrode.

[0046] Furthermore, the high-speed vertical cavity surface-emitting laser has a first end side and a second end side arranged opposite to each other, and the first region and the second region are arranged sequentially from the first end side toward the second end side;

[0047] A second colloidal structure is provided on the first dielectric film above the second region where no second window is opened, and the second colloidal structure has a clearance groove corresponding to the position of the second window;

[0048] A third medium film is provided on the top surface of the second colloidal structure, the inner wall of the clearance groove, and the inner wall of the second window;

[0049] The second electrode covers the third dielectric film.

[0050] This invention has at least the following advantages or beneficial effects:

[0051] The method for fabricating a high-speed vertical-cavity surface-emitting laser provided by the present invention includes: step S10. providing an epitaxial structure, the epitaxial structure including a substrate, a lower Bragg mirror, and an active region arranged sequentially from bottom to top, the top surface of the active region having a first region, and a current spreading layer formed on the first region; the substrate including a second region not covered by the lower Bragg mirror; step S20. forming a first dielectric film on the entire top surface of the epitaxial structure, the current spreading layer and the second region both being 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 annular; etching the first dielectric film above the second region ... The first dielectric film is etched to obtain the 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 placed above the first electrode, and 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. Multiple 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 along the direction from the center of the upper dielectric Bragg reflector toward its circumferential outward.

[0052] In the process of fabricating the high-speed vertical-cavity surface-emitting laser using the above method, the first and second windows are formed by etching. This eliminates the need to introduce oxide confinement holes to laterally confine the light and electricity, avoids the stress and singularity of oxide holes introduced by the oxidation process, thereby alleviating the current congestion effect and improving the reliability of the device. In addition, the fabricated high-speed vertical-cavity surface-emitting laser eliminates the need for the epitaxial Bragg mirror grown on top of the epitaxial structure in traditional high-speed vertical-cavity surface-emitting lasers. In existing technologies, the use of epitaxial Bragg mirrors makes it impossible to fabricate electrodes below the epitaxial Bragg mirror, thus the circuit cannot avoid the series resistance caused by the Bragg mirror. In this embodiment, unlike the above-mentioned scheme, a dielectric Bragg mirror scheme is used, which optimizes the current path. Specifically, the upper dielectric Bragg mirror is set on the first dielectric film, and the current injected by the first electrode directly enters the active region through the current extension layer, reducing the parasitic resistance of the device and improving the high-speed modulation characteristics of the device. In the upper dielectric Bragg mirror, a photonic crystal air hole is formed to achieve the optical mode confinement effect. Furthermore, the depth of the photonic crystal air hole gradually decreases from the periphery to the center, thereby forming a distribution with a gradually increasing equivalent refractive index from the outside to the inside, achieving a light field convergence effect and reducing the divergence angle of the device. Attached Figure Description

[0053] 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.

[0054] Figure 1 This is a schematic diagram showing the result of step S1 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in this embodiment of the invention.

[0055] Figure 2 This is a schematic diagram showing the result of step S2 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in this embodiment of the invention.

[0056] Figure 3 This is a schematic diagram showing the result of step S3 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in this embodiment of the invention.

[0057] Figure 4 This is a schematic diagram showing the result of step S4 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in this embodiment of the invention.

[0058] Figure 5 This is a schematic diagram showing the result of step S11 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0059] Figure 6 This is a schematic diagram showing the result of step S20 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0060] Figure 7 A schematic diagram showing the result of steps S21 and S23 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0061] Figure 8 A schematic diagram showing the result of steps S22 and S24 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0062] Figure 9 This is a schematic diagram showing the result of step S30 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0063] Figure 10 This is a schematic diagram showing the result of step S40 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0064] Figure 11 This is a schematic diagram showing the result of step S50 in the method for fabricating a high-speed vertical-cavity surface-emitting laser provided in an embodiment of the present invention.

[0065] Figure 12 This is a top view of the high-speed vertical-cavity surface-emitting laser fabrication method provided in the embodiment of the present invention after step S50 is performed (the unprocessed area is circular).

[0066] Figure 13 This is a top view of the fabrication method for a high-speed vertical-cavity surface-emitting laser provided in this embodiment of the invention after step S50 is performed (the unprocessed area is a double circle).

[0067] Icons: 1-Substrate; 2-Lower Bragg mirror; 3-Active region; 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-Allowing groove; 16-Third dielectric film; 17-First dielectric film; 18-First window; 19-Second window; 20-First electrode; 201-Annular structure; 202-Conductive layer; 21-Second electrode; 22-Upper dielectric Bragg mirror; 221-Unprocessed hole region; 23-Photonic crystal air hole. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0069] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0070] 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.

[0071] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0072] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they 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 can be slightly tilted.

[0073] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0074] The method for fabricating a high-speed vertical-cavity surface-emitting laser provided by this invention includes:

[0075] like Figure 4 As shown, step S10 provides an epitaxial structure, which includes a substrate 1, a lower Bragg mirror 2 and an active region 3 arranged sequentially from bottom to top. The top surface of the active region 3 has a first region 5, and a current spreading layer 4 is formed on the first region 5. The substrate 1 includes a second region 6 that is not covered by the lower Bragg mirror 2.

[0076] Specifically, the epitaxial structure can be prepared through steps S1-S4:

[0077] like Figures 1-4 As shown, in step S1, a Lower Bragg mirror 2 and an active region 3 are grown sequentially on substrate 1 using substrate 1 as the base. The material of substrate 1 includes, but is not limited to, GaN, GaA, InP, etc.

[0078] Step S2. Deposit a current spreading layer 4 on the upper surface of the active region 3.

[0079] Step S3. Etch the current spread layer 4 and the active region 3 to remove the current spread layer 4 and the active region 3 outside the first region 5, and the remaining first region 5 forms a P-electrode mesa.

[0080] Step S4. The epitaxial structure, to which the current extension layer 4 and a portion of the active region 3 have been removed, is etched again to remove part of the lower Bragg mirror 2 down to the substrate 1, in order to form the second region 6, which is an N-electrode mesa.

[0081] like Figure 5 As shown, the preparation method further includes a step performed between steps S10 and S20:

[0082] S11. Ion implantation, wherein the ion implantation region 7 includes the first region 5 and the region in the current spreading layer 4 that is a distance L from the center of the current spreading layer 4.

[0083] Not all of the first region 5 is ion-implanted region 7, because step S11 is performed after step S10. This means that before 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 ion-implanted region 7. Before ion implantation, a baffle can be used to cover the second region 6 and the region within a length L of the center of the current spreading layer 4. Then, ion implantation is performed, so that the first region 5 and parts of the region outside the length L of the center of the current spreading layer 4 have implanted ions. The implanted ions can be hydrogen, helium, or boron. After ion implantation, the ion-implanted region 7 becomes non-conductive, achieving lateral electrical isolation.

[0084] like Figure 6As shown, in 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, which is annular; the first dielectric film 17 above the second region 6 is etched to obtain a second window 19.

[0085] 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 and a second window 19 can be formed on the first dielectric film 17 above the current spreading layer 4 and above the second region 6 of the substrate 1, respectively, by photolithography. The first window 18 and the second window 19 can be etched simultaneously or sequentially.

[0086] The first window 18 and the second window 19 are formed by etching, eliminating the need for oxide confinement vias to laterally confine the light and electricity. This avoids the stress introduced by the oxidation process and the singularity of oxide vias, thereby mitigating the current congestion effect and improving device reliability. The first window 18 and the second window 19 are designed with smooth edges, solving the singularity problem of oxide vias, mitigating the current congestion effect, and improving reliability. Furthermore, the shape and size of the first window 18 can be defined to define the optical gain region and optical mode distribution.

[0087] like Figures 7-8 As shown, for ease of explanation of the structure, the extension structure is assumed to have a first end side 8 (left side) and a second end side 9 (right side) arranged opposite to each other. 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.

[0088] The method also includes steps performed between steps S20 and S30:

[0089] Step S21. A first colloidal structure 11 is deposited and cured on the first dielectric film 17 within the first lateral range 10; wherein, the first lateral range 10 is the region between the first end side 8 and the current spreading layer 4 in the lateral direction. Step S22. A second dielectric film 13 is deposited and cured within the second lateral range 12; wherein, the second lateral range 12 is the region between the first end side 8 and the first window 18 in the lateral direction.

[0090] By shielding at different locations, a first colloidal structure 11 and a second dielectric film 13 are deposited and obtained in two separate depositions. 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 parallel 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.

[0091] The method may also include steps performed between steps S20 and S30:

[0092] like Figure 7 As shown, in step S23, a second colloidal structure 14 is obtained by depositing and curing on the first dielectric film 17 above the second region 6. The second colloidal structure 14 has a clearance groove 15 corresponding to the position of the second window 19. Figure 8 As shown, in step S24, a third dielectric film 16 is deposited and cured on the top surface of the second colloidal structure 14, the inner wall of the clearance groove 15, and the inner wall of the second window 19.

[0093] Similarly, the material of the second colloidal structure 14 is generally a low dielectric constant material. The second electrode 21 and the substrate 1 are equivalent to the two poles of a parallel 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.

[0094] A clearance groove 15 is formed on the second colloidal structure 14 by photolithography. The clearance 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 so that the area of ​​the substrate 1 corresponding to the position of 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 encapsulate and protect the second colloidal structure 14.

[0095] 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.

[0096] The first electrode 20 fills the first window 18, and a portion of the first electrode 20 extends to the outside of the first window 18 and covers the second dielectric film 13, for use with an external power supply. Similarly, the second electrode 21 fills the second window 19, and a portion of the second electrode 21 extends to the outside of the second window 19, and the second electrode 21 covers the third dielectric film 16, for use with an external power supply.

[0097] like Figure 10 As shown, in 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 onto 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.

[0098] The fabricated high-speed vertical-cavity surface-emitting laser eliminates the epitaxial Bragg reflector grown on the epitaxial structure of traditional high-speed vertical-cavity surface-emitting lasers. In this embodiment, the upper dielectric Bragg reflector 22 is disposed on the first dielectric film 17, which reduces the parasitic resistance of the device and improves the high-speed modulation characteristics of the device.

[0099] The materials used for the upper dielectric Bragg reflector 22 include, but are not limited to, Si, SiO2, SiN, ITO, TiO, and AlO, and the fabrication methods include, but are not limited to, chemical vapor deposition, electron beam evaporation, and magnetron sputtering. The current spreading layer 4 can be grown epitaxially or fabricated by electron beam evaporation or magnetron sputtering.

[0100] like Figure 11 As shown, in 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 along the direction from the center of the upper dielectric Bragg reflector 22 toward its circumferential outward.

[0101] In the upper dielectric Bragg reflector 22, an optical mode confinement effect is achieved by forming a photonic crystal air hole 23. 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 light field convergence effect and reducing the divergence angle of the device.

[0102] like Figure 12 As shown, there is an unprocessed hole region 221 at the center of the upper dielectric Bragg reflector 22, and the diameter D of the unprocessed hole region 221 ranges from 3um to 10um. When the shape of the unprocessed hole region 221 is not circular, the diameter D is calculated by area conversion.

[0103] The laser mode can be changed by altering the diameter D of the unprocessed hole region 221. As the diameter D increases, the device output mode changes from single-mode to multi-mode.

[0104] The shape of the inner ring edge of the first window 18 is the same as the projection shape of the unprocessed hole region 221 onto 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 region 221 onto the first dielectric film 17.

[0105] The advantage of having an inner ring edge area of ​​the first window 18 that is greater than or equal to the area of ​​the unprocessed hole region 221 projected onto the first dielectric film 17 is that it increases the actual gain region, ensures that the gain region area is greater than the region providing high reflectivity, and improves the output power.

[0106] The shape of the unprocessed hole area 221 can be equivalent to a circle, an ellipse, a rhombus, a double rhombus, or a double circle.

[0107] By restricting the shape of the unetched area, control over optical modes is provided, and high-speed capabilities are also improved through the coupling between optical modes. For example, the shape of the unprocessed aperture region 221 is equivalent to a single asymmetric shape, such as an ellipse or rhombus, which can provide polarization control capabilities. If it is a double rhombus 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 can be improved by coupling the optical modes between the two parts.

[0108] It should be noted that when the shape of the unprocessed hole area 221 is a rhombus or double rhombus, which has a apex corner, in order to avoid the problem of singularity, the rhombus and double rhombus shape can be set with the apex corner rounded, that is, the apex corner is rounded.

[0109] like Figure 12 As shown, in the top surface of the upper dielectric Bragg reflector 22, the duty cycle of the photonic crystal air hole 23 is b / a. The value of b / a ranges from 0.3 to 0.7. The larger the duty cycle, the stronger the refractive index guiding effect. Here, b is the diameter of the photonic crystal air hole 23, and a is the distance between the centers of the two adjacent photonic crystal air holes 23.

[0110] The depth h of the air hole 23 in the photonic crystal ranges from 50 nm to 500 nm. It does not exceed the thickness of the upper dielectric Bragg mirror 22. The deeper the etching depth, the stronger the refractive index guiding effect.

[0111] The lattice constant of the photonic crystal air hole 23 ranges from 1µm to 10µm. The larger the lattice constant, the easier the fabrication, but the worse the modulation effect.

[0112] This scheme introduces a laser fabrication method. The laser is fabricated by growing a dielectric Bragg mirror, an active region 3, and a current spreading layer 4 on an n-type substrate 1. Then, a P-type current injection hole, i.e., a first window 18, is fabricated by photolithography deposition and lift-off on the current spreading layer 4, thereby obtaining a current injection hole with smooth edges. 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 improving the speed. Subsequently, a dielectric Bragg mirror 22 is deposited on the current spreading layer 4 above the current injection hole to provide the high reflectivity required for lasing. Periodic photonic crystal air holes 23 are etched on the dielectric Bragg mirror 22 to achieve optical lateral confinement. The etching depth of the photonic crystal air holes 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.

[0113] Beneficial effects:

[0114] 1. The current injection holes (first window 18 and second window 19) are prepared by photolithography, deposition and lift-off, which can obtain a current injection morphology with smooth edges, solve the singularity problem of oxide holes, alleviate the current crowding effect and improve reliability;

[0115] 2. By not setting an epitaxial Bragg mirror and placing the current injection hole under the upper dielectric Bragg mirror 22, the current can flow directly from the first electrode 20 into the active region 3, which solves the problem of large parasitic parameters of the epitaxial P-type Bragg mirror in traditional lasers; at the same time, the optical gain region and optical mode distribution can be defined by defining the shape and size of the current injection hole.

[0116] 3. By etching periodic photonic crystal air holes 23 on the upper dielectric Bragg mirror 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 the focusing effect on the light field;

[0117] 4. By etching periodic photonic crystal air holes 23 on the upper dielectric Bragg mirror 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 mirror 22, thereby achieving a lateral optical confinement effect. Furthermore, 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.

[0118] 5. Etching the first window 18 and the second window 19 forms an optical confinement, and fabricating a current ring directly forms a current confinement, thereby removing the oxide confinement hole and avoiding defects and stress introduced by the oxidation process.

[0119] The high-speed vertical-cavity surface-emitting laser provided by this invention can be obtained by the above-described fabrication method. For example... Figures 1-11 As shown, the laser includes: an epitaxial structure, a first dielectric film 17, and an upper dielectric Bragg reflector 22.

[0120] The epitaxial structure includes a substrate 1, a lower Bragg mirror 2, and an active region 3 arranged sequentially from bottom to top. The top surface of the active region 3 has a first region 5, which does not completely cover the entire lower Bragg mirror 2. The substrate 1 includes a second region 6 that is not covered by the lower Bragg mirror 2.

[0121] A first conductive structure is provided in the first region 5. The first conductive structure may include a current spreading layer 4 and a first electrode 20. The first conductive structure includes a ring structure 201, which forms the first electrode 20.

[0122] A first dielectric film 17 covers a first region 5, a second region 6, and a portion of a first conductive structure. A first window 18, which avoids an annular structure 201, is provided on the first dielectric film 17. 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, located at the top of the second region 6. A second electrode 21, in contact with the second region 6, is disposed within the second window 19.

[0123] In this embodiment, the first window 18 and the second window 19 are formed by etching, which eliminates the need to introduce oxide limiting holes to laterally restrict light and electricity. This avoids the stress and oxide hole singularities introduced by the oxidation process, thereby alleviating the current crowding effect and improving the reliability of the device.

[0124] 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 onto 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.

[0125] The fabricated high-speed vertical-cavity surface-emitting laser eliminates the epitaxial Bragg reflector grown on the epitaxial structure of traditional high-speed vertical-cavity surface-emitting lasers. In this embodiment, the upper dielectric Bragg reflector 22 is disposed on the first dielectric film 17, which reduces the parasitic resistance of the device and improves the high-speed modulation characteristics of the device.

[0126] The top surface of the upper dielectric Bragg reflector 22 is provided with a plurality of downwardly extending photonic crystal air holes 23; 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 its circumferential outward.

[0127] In the upper dielectric Bragg reflector 22, an optical mode confinement effect is achieved by forming a photonic crystal air hole 23. 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 light field convergence effect and reducing the divergence angle of the device.

[0128] An unprocessed aperture region 221 exists at the center of the upper dielectric Bragg reflector 22, and the diameter D of the unprocessed aperture region 221 ranges from 3µm to 10µm. By changing the diameter D of the unprocessed aperture region 221, the laser mode can be changed, thereby forming single-mode and multi-mode lasers.

[0129] The shape of the inner ring edge of the first window 18 is the same as the projection shape of the unprocessed hole region 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 region 221 on the first dielectric film 17.

[0130] The advantage of having an inner ring edge area of ​​the first window 18 that is greater than or equal to the area of ​​the unprocessed hole region 221 projected onto the first dielectric film 17 is that it increases the actual gain region, ensures that the gain region area is greater than the region providing high reflectivity, and improves the output power.

[0131] The shape of the unprocessed hole area 221 is equivalent to a circle, an ellipse, a rhombus, a double rhombus, or a double circle.

[0132] By restricting the shape of the unetched region, control over optical modes can be provided, and high-speed capabilities can also be improved by informing the coupling between optical modes. For example, the shape of the unprocessed aperture region 221 is equivalent to a single asymmetric shape, such as an ellipse or rhombus, which can provide polarization control capabilities. If it is a double rhombus or double circle, the optical mode can be divided into two parts, and the high-speed modulation capability can be improved through the coupling of optical modes between the two parts.

[0133] like Figure 12 As shown, in the top surface of the upper dielectric Bragg reflector 22, the duty cycle of the photonic crystal air hole 23 is b / a. The value of b / a ranges from 0.3 to 0.7. The larger the duty cycle, the stronger the refractive index guiding effect. Here, b is the diameter of the photonic crystal air hole 23, and a is the distance between the centers of the two adjacent photonic crystal air holes 23.

[0134] The depth h of the air hole 23 in the photonic crystal ranges from 50 nm to 500 nm. It does not exceed the thickness of the upper dielectric Bragg mirror 22. The deeper the etching depth, the stronger the refractive index guiding effect.

[0135] The lattice constant of the photonic crystal air hole 23 ranges from 1µm to 10µm. The larger the lattice constant, the easier the fabrication, but the worse the modulation effect.

[0136] The first dielectric membrane 17 includes a covering portion located outside the annular outer edge of the first window 18; in the first region 5, the portion located below the covering portion has implanted ions.

[0137] The implanted ions can be hydrogen, helium, or boron. After ion implantation, the implanted region becomes non-conductive, achieving lateral electrical isolation.

[0138] The high-speed vertical cavity surface-emitting laser has a first end side 8 and a second end side 9 arranged opposite to each other, and a first region 5 and a second region 6 are arranged sequentially from the first end side 8 toward the second end side 9.

[0139] A first colloidal structure 11 is disposed on a first dielectric film 17 within a first lateral range 10; wherein, the first lateral range 10 is: the region between the first end side 8 and the current spreading layer 4 in the lateral direction; the top surface of the first colloidal structure 11, and the portion of the first dielectric film 17 between the first window 18 and the first colloidal structure 11 are covered by a second dielectric film 13; the first conductive structure includes a conductive layer 202 connected to the annular structure 201, extending to 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.

[0140] By shielding at different locations, a first colloidal structure 11 and a second dielectric film 13 are deposited and obtained in two separate depositions, thereby reducing the parasitic parameters of the device.

[0141] A second colloidal structure 14 is provided on the first dielectric film 17 above the second region 6 where the second window 19 is not opened. The second colloidal 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 colloidal structure 14, the inner wall of the relief groove 15, and the inner wall of the second window 19. The second electrode 21 covers the third dielectric film 16.

[0142] 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 fabricating a high-speed vertical-cavity surface-emitting laser, characterized in that, include: Step S10. Provide an epitaxial structure, the epitaxial structure including a substrate (1), a lower Bragg mirror (2) and an active region (3) arranged sequentially from bottom to top, the top surface of the active region (3) having a first region (5), and a current spreading layer (4) formed on the first region (5); the substrate (1) includes a second region (6) not covered by the lower Bragg mirror (2). 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), the first window (18) is annular; the first dielectric film (17) above the second region (6) is etched to obtain a second window (19). Step S30. Form a first electrode (20) in the first window (18); form a second electrode (21) in the second window (19); 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) onto 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. 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 along the direction from the center of the upper dielectric Bragg reflector (22) toward its circumferential outward.

2. The method for fabricating a high-speed vertical-cavity surface-emitting laser according to claim 1, characterized in that, The upper medium Bragg reflector (22) has an unprocessed hole region (221) at its center, and the diameter D of the unprocessed hole region (221) ranges from 3um to 10um.

3. The method for fabricating 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 region (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 region (221) onto the first dielectric film (17); and / or, The shape of the unprocessed hole area (221) is equivalent to a circle, an ellipse, a rhombus, a double rhombus, or a double circle.

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

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

6. The method for fabricating a high-speed vertical-cavity surface-emitting laser according to any one of claims 1-4, characterized in that, The extension structure has a first end side (8) and a second end side (9) disposed opposite to each other, and the first region (5) and the second region (6) are disposed sequentially from the first end side (8) toward the second end side (9); It also includes the steps performed between steps S20 and S30: Step S21. Deposit and cure a first colloidal structure (11) on a first dielectric film (17) within a first lateral range (10); wherein, the first lateral range (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 the second lateral range (12); wherein, the second lateral range (12) is: the region between the first end side (8) and the first window (18) in the lateral direction; In 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 fabricating a high-speed vertical-cavity surface-emitting laser according to any one of claims 1-4, characterized in that, The extension structure has a first end side (8) and a second end side (9) disposed opposite to each other, and the first region (5) and the second region (6) are disposed sequentially from the first end side (8) toward the second end side (9); It also includes the steps performed between steps S20 and S30: Step S23. A second colloidal structure (14) is deposited and cured on the first dielectric film (17) above the second region (6), and the second colloidal structure (14) has a relief groove (15) corresponding to the position of the second window (19). Step S24. A third dielectric film (16) is deposited and cured on the top surface of the second colloidal structure (14), the inner wall of the relief groove (15), and the inner wall of the second window (19). In 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: The epitaxial structure includes a first dielectric film (17) and an upper dielectric Bragg mirror (22); the epitaxial structure includes a substrate (1), a lower Bragg mirror (2) and an active region (3) arranged sequentially from bottom to top, the top surface of the active region (3) having a first region (5); the substrate (1) includes a second region (6) not covered by the lower Bragg mirror (2); A first conductive structure is provided in the first region (5); the first conductive structure includes 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 at 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 disposed above the first dielectric film (17), and the projection of the edge of the upper dielectric Bragg reflector (22) onto 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); the top surface of the upper dielectric Bragg reflector (22) is provided with a plurality of downwardly extending photonic crystal air holes (23); 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 its circumferential outward.

9. The high-speed vertical-cavity surface-emitting laser according to claim 8, characterized in that, The upper medium Bragg reflector (22) has an unprocessed hole region (221) at its center, and the diameter D of the unprocessed hole region (221) ranges from 3um to 10um.

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 region (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 region (221) onto the first dielectric film (17); and / or, The shape of the unprocessed hole area (221) is equivalent to a circle, an ellipse, a rhombus, a double rhombus, 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) ranges from 0.3 to 0.7; and / or, The depth h of the air hole (23) in the photonic crystal ranges from 50 nm to 500 nm; and / or, The lattice constant of the photonic crystal air hole (23) ranges from 1um to 10um.

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), the portion located below the covered portion has injected ions.

13. The high-speed vertical-cavity surface-emitting laser according to any one of claims 8-12, characterized in that, The high-speed vertical cavity surface-emitting laser has a first end side (8) and a second end side (9) arranged opposite to each other. The first region (5) and the second region (6) are arranged sequentially from the first end side (8) toward the second end side (9). A first colloidal structure (11) is provided on a first dielectric film (17) within a first lateral range (10); wherein, the first lateral range (10) is: the region between the first end side (8) and the current spreading layer (4) in the lateral direction; A second dielectric film (13) is covered on the top surface of the first colloidal structure (11) and on the first dielectric film (17) between the first window (18) and the first colloidal structure (11). The first conductive structure includes a conductive layer (202) connected to the annular structure (201) and extending to the first end side (8) and covering the second dielectric film (13), wherein 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 8-12, characterized in that, The high-speed vertical cavity surface-emitting laser has a first end side (8) and a second end side (9) arranged opposite to each other. The first region (5) and the second region (6) are arranged sequentially from the first end side (8) toward the second end side (9). A second colloidal structure (14) is provided on the first dielectric film (17) above the second region (6) where no second window (19) is opened. The second colloidal structure (14) has a relief groove (15) corresponding to the position of the second window (19). A third medium membrane (16) is provided on the top surface of the second colloidal structure (14), the inner wall of the relief 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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