Vertical cavity surface emitting laser structure and preparation method thereof

Abstract

The invention relates to the technical field of lasers, and discloses a vertical cavity surface emitting laser structure and a preparation method thereof. The preparation method comprises the steps that an epitaxial structure comprising a first reflector layer, a first limiting layer, an active layer, a second limiting layer and a second reflector layer is formed on the surface of one side of a substrate layer, and the epitaxial structure is provided with a light emitting area; an oxidation groove extending into the first reflector layer from the second reflector layer is formed in the light emitting area; forming an oxidation layer with an oxidation hole in the second reflector layer of the light emitting area; ion implantation is carried out on the epitaxial structure to form an ion implantation region and a current implantation region, the current implantation region surrounded by the ion implantation region is located in the light emitting region, and the projection of the current implantation region on the substrate layer covers the projection of the oxidation hole. On the premise that the oxide layer with the oxidation hole is formed, the ion injection region surrounding the current injection region and the oxidation hole is accurately and efficiently controlled to be formed in an ion injection mode, and the reliability, the bandwidth performance and the transmission rate of the laser structure can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and particularly to a vertical-cavity surface-emitting laser structure and a preparation method thereof. Background Art

[0002] With the rise of cloud computing, 5G technology, and the Internet of Things, the demand for high speed and high bandwidth in the communication field is increasing continuously. At the same time, the requirements for high-performance optical communication products in data centers are also increasing continuously to support larger data storage, stronger processing, and faster transmission capabilities. Based on this, vertical-cavity surface-emitting lasers (VCSELs) stand out among many semiconductor optical communication products with their advantages of high reliability, easy coupling, low power consumption, low cost, and easy integration into large-area arrays, and are widely used in the optical communication and consumer electronics industries.

[0003] Currently, in order to pursue higher transmission rates, current VCSEL products usually adopt the method of reducing the oxidation aperture to achieve it. However, because the oxidation rate is not linear during the wet oxidation process and there are differences in the uniformity of the oxidation process, it is difficult to precisely control the doping oxidation effect, especially when it is desired to form oxidation holes with a smaller target aperture, which is even more difficult. Therefore, there will be a certain percentage of yield loss during the mass production of VCSEL products that need to form smaller target oxidation apertures through the wet oxidation process. At the same time, if the aperture of the oxidation hole is too small, it will also limit the light output efficiency, and the current density in the active region of the laser will be much higher than that of a laser with a conventional oxidation aperture, and the junction temperature in the laser will increase several times, ultimately shortening the service life of the device and seriously affecting the product reliability. Summary of the Invention

[0004] In view of this, the present invention provides a vertical-cavity surface-emitting laser structure and a preparation method thereof to solve the problems of poor reliability and low transmission rate of existing vertical-cavity surface-emitting lasers.

[0005] In a first aspect, the present invention provides a preparation method of a vertical-cavity surface-emitting laser structure, including:

[0006] Form an epitaxial structure on one side surface of a substrate layer. The epitaxial structure includes a first mirror layer, a first confinement layer, an active layer, a second confinement layer, and a second mirror layer stacked in sequence; the epitaxial structure has a light-emitting region;

[0007] Form an oxidation trench on the side of the light-emitting region facing away from the substrate layer. The oxidation trench extends from the second mirror layer into the first mirror layer;

[0008] Form an oxidation layer in the second mirror layer of the light-emitting region. The oxidation layer has oxidation holes;

[0009] Ion implantation is performed on the side of the epitaxial structure away from the substrate layer to form an ion implantation region and a current injection region in the epitaxial structure. The current injection region is located within the light-emitting region, the ion implantation region surrounds the current injection region, and the projection region of the current injection region on the substrate layer covers the projection region of the oxidation hole on the substrate layer.

[0010] Beneficial effects: In the manufacturing method of the vertical cavity surface emitting laser structure of the present invention, after forming an oxide layer with a conventional relatively large oxidation hole by a compatible conventional process, an ion implantation process is used to form an ion implantation region in the epitaxial structure outside the projection region of the oxidation hole, ensuring the reliability of the oxidation hole and the oxide layer. The central region surrounded by the ion implantation region forms a current injection region for laser emission. The ion implantation region is a high-resistance region relative to the current injection region, which can effectively confine the lateral current, reduce the lateral expansion of the current, increase the effective injected current. At the same time, ion implantation can improve the doping characteristics of the epitaxial structure, thereby reducing the parasitic parameters of the laser structure itself and effectively improving the bandwidth performance of the laser structure. On the premise of forming an oxide layer with a large oxidation hole, the ion implantation region surrounding the current injection region and the oxidation hole is accurately and efficiently controlled by ion implantation, effectively improving the reliability of the laser structure, and at the same time greatly improving the bandwidth performance and transmission rate of the laser structure.

[0011] In an optional embodiment, the shapes of the oxide layer and the current injection region are both olive-shaped structures.

[0012] Beneficial effects: The present invention sets the oxidation trench as a partial olive-ring structure, and the oxide layer is formed by doping inward from the inner wall surface of the oxidation trench, so the shape of the oxide layer is also an olive-shaped pore structure similar to the oxidation trench. Based on this, the shape of the shielding layer is set as a similar olive-shaped plate with a different size but the same shape as the oxidation trench, so that the projection shape of the current injection region formed directly below the shielding layer is also a similar olive shape. In this way, the olive-shaped low-resistance current injection region that is not ion implanted is consistent with the morphology of the oxide layer, forming a perfect current guiding layer. When current is injected, the current will be evenly guided to the oxide layer and then flow to the active region, which not only ensures the uniformity of current injection but also maximizes the efficiency of current injection, effectively solving the problems of performance defects and reliability caused by abnormal current density distribution in the laser structure, while improving the overall photoelectric conversion efficiency. The improvement of the photoelectric conversion efficiency can fully reduce the spontaneous emission of the laser structure during laser emission, thereby reducing the relative intensity noise of the laser structure during operation. According to Shannon's law, within a limited bandwidth, the relative intensity noise of the laser structure during operation can be reduced, that is, the signal-to-noise ratio and channel capacity of the laser structure are improved, and finally the bandwidth and transmission rate are effectively increased.

[0013] In an optional embodiment, the ratio range of the major axis to the minor axis of the olive-shaped structure is 6:5 to 5:4.

[0014] Beneficial effects: By limiting the ratio of the major axis to the minor axis of the olive-shaped structure between 1.2 and 1.25, the uniformity and efficiency of current injection can be maximally improved, effectively solving the problems of laser structure performance defects and reliability caused by abnormal current density distribution, and at the same time increasing the overall photoelectric conversion efficiency by about 5%-7%; thereby fully reducing the spontaneous emission of the laser structure during laser emission, reducing the relative intensity noise of the laser structure, improving the signal-to-noise ratio and channel capacity, and ultimately achieving the maximum increase in bandwidth and transmission rate.

[0015] In an alternative embodiment, ion implantation on the side of the epitaxial structure facing away from the substrate layer includes: performing multiple ion implantations on the epitaxial structure along a direction perpendicular to the surface of the side of the epitaxial structure facing away from the substrate layer.

[0016] Beneficial effects: By performing ion implantation with multiple different types of ions, the dosage and effect of ion implantation can be effectively controlled in batches. At the same time, different ions can form different dopings within the epitaxial structure, effectively improving the doping uniformity and density.

[0017] In an alternative embodiment, ion implantation on the side of the epitaxial structure facing away from the substrate layer includes:

[0018] Performing a first ion implantation on the side of the epitaxial structure facing away from the substrate layer, the doping ion of the first ion implantation is boron ion, and the total dose of boron ion is 1.6E+13 cm -2 , implanted once;

[0019] Performing a second ion implantation on the side of the epitaxial structure facing away from the substrate layer, the doping ion of the second ion implantation is helium ion, and the total dose of helium ion is 4E+13 cm -2 , implanted in three batches;

[0020] Performing a third ion implantation on the side of the epitaxial structure facing away from the substrate layer, the doping ion of the third ion implantation is hydrogen ion, and the total dose of hydrogen ion is 2E+13 cm -2 , implanted in two batches.

[0021] Beneficial effects: The present invention uses boron ions, helium ions, and hydrogen ions as dopant ions for implantation, and helium ions and hydrogen ions are implanted in batches. The present invention innovatively uses boron ions to perform ion implantation on the VCSEL laser structure, and the ion implantation process adopts the method of batch implantation, which can not only ensure the doping effect after ion implantation, but also ensure that the structure of the P-type metal contact layer will not react with the doping ions or cause damage during the ion implantation process, and can fully ensure the reliability of the laser structure.

[0022] In an alternative embodiment, after forming an epitaxial structure on one side surface of the substrate layer and before forming an oxidation trench on the side of the light-emitting region facing away from the substrate layer, the method further includes: forming a contact electrode layer on the side surface of the light-emitting region facing away from the substrate layer, the contact electrode layer having a first light-emitting hole adapted for laser emission; the projection area of the current injection region on the substrate layer covers the projection area of the first light-emitting hole on the substrate layer, the first light-emitting hole is concentric with the oxidation hole, and the projection area of the first light-emitting hole is larger than the projection area of the oxidation hole.

[0023] Beneficial effects: The contact electrode layer is arranged in a ring structure, and the hollow part in the middle forms the first light-emitting hole for laser emission. At the same time, the formed contact electrode layer can also be used as a positioning mark when forming the subsequent oxidation trench, which helps to accurately form the oxidation trench; the first light-emitting hole of the formed contact electrode layer should be concentric with the oxidation hole of the oxide layer, and the aperture of the first light-emitting hole should be larger than the aperture of the oxidation hole, so as to ensure that after subsequent processes, the output laser restricted by the oxidation hole can still be emitted from the first light-emitting hole to the greatest extent.

[0024] In an alternative embodiment, after forming an oxide layer in the second mirror layer of the light-emitting region and before performing ion implantation on the side of the epitaxial structure facing away from the substrate layer, the method further includes: forming a passivation layer on the side of the epitaxial structure facing away from the substrate layer, the passivation layer covering the surface of the epitaxial structure, the surface of the contact electrode layer, and the inner wall surface of the oxidation trench.

[0025] Beneficial effects: The passivation layer covers the side surface of the epitaxial structure facing away from the substrate layer, ensuring the protection of the surfaces of these structural layers during ion implantation and even subsequent other processes, and at the same time reducing surface defects.

[0026] In an alternative embodiment, the epitaxial structure further has a first electrode region and a connection region connecting the light-emitting region and the first electrode region, and the first electrode region is adapted to connect to an external power supply;

[0027] After performing ion implantation on the side of the epitaxial structure facing away from the substrate layer, the method further includes: forming a dielectric filling layer on the side surface of the first electrode region facing away from the substrate layer.

[0028] Beneficial effects: The light-emitting area and the first electrode area are connected through a connection area. In the first electrode area, electrical excitation is directly connected to an external power supply through wire bonding. The electrical excitation enters the light-emitting area through the connection area, causing photons to be generated in the active area of the light-emitting area, thereby forming a laser output. This enables the first electrode area to have more external connection possibilities and improves the scope of application. The dielectric filling layer is disposed on the epitaxial structure surface of the first electrode area, which helps to optimize the impedance matching between the first electrode and the package body in subsequent packaging processes, can adjust the electric field distribution between the first electrode and other components in the future, thereby reducing the parasitic capacitance, reducing the number of charge and discharge cycles, effectively avoiding interference with the optical signal transmission, and thus improving the modulation bandwidth of the VCSEL to meet the requirements of high-speed optical communication.

[0029] In an optional embodiment, after forming the dielectric filling layer on the surface of the first electrode area facing away from the substrate layer, it further includes:

[0030] Removing a part of the passivation layer on the contact electrode layer to form a first opening exposing the contact electrode layer;

[0031] Forming a first electrode on the first electrode area of the epitaxial structure. The first electrode covers the dielectric filling layer and is connected to the contact electrode layer through the first opening; the first electrode also has a second light-emitting hole corresponding to the first light-emitting hole.

[0032] Beneficial effects: The passivation layer forms a first opening for subsequent current injection from the contact electrode layer; the first electrode is formed over a large area in the first electrode area and extends to the contact electrode layer in the light-emitting area, achieving good electrical connection with the contact electrode layer. The contact electrode layer can also act as a seed layer to enhance the ohmic contact between the first electrode and the surface of the light-emitting area.

[0033] In an optional embodiment, after forming the first electrode on the first electrode area of the epitaxial structure, it further includes:

[0034] Etching away a part of the epitaxial structure to expose a part of the substrate layer to form a second electrode area, and the second electrode area is isolated from both the first electrode area and the light-emitting area;

[0035] Forming a second electrode on the substrate layer of the second electrode area, and the second electrode has an opposite electrical property to the first electrode.

[0036] Beneficial effects: By etching a selected area to form the second electrode area, different positions of the second electrode, the first electrode, and the light-emitting area are formed, improving the compatibility of the laser structure in aspects such as bandwidth detection.

[0037] In an optional embodiment, the second electrode includes a first sub-electrode and a second sub-electrode, and the first sub-electrode, the second sub-electrode and the first electrode constitute a GSG structure; the first sub-electrode and the second sub-electrode are respectively arranged on both sides of the first electrode, and form an L-shaped structure with the connection line of the first electrode, and the light output area is located between the first sub-electrode and the second sub-electrode.

[0038] Beneficial effects: The front electrode solution of the laser structure is a GSG structure. The GSG three-electrode solution on the same surface can be compatible with different types of probes in the high-frequency test of the chip. It can also reduce parasitic capacitance in laser packaging applications and improve the high-speed modulation performance of the chip.

[0039] In an optional embodiment, after the second electrode is formed in the second electrode area, it also includes: forming a protective layer on the side of the substrate layer away from the substrate layer, the protective layer covers the light output area, the first electrode area, the connection area and the second electrode area, the protective layer forms a second opening on the first electrode, and the protective layer forms a third opening on the second electrode.

[0040] Beneficial effects: The entire front side of the laser structure is covered with a protective layer to protect the inside of the laser structure from water vapor erosion, thereby improving the reliability of the product. An opening is provided above the first electrode and the second electrode to facilitate wiring access to an external power supply.

[0041] In an optional embodiment, after forming the protective layer on the side of the substrate layer facing away from the substrate layer, the method further includes:

[0042] Thinning a surface of the substrate layer facing away from the substrate layer;

[0043] A third electrode is formed on a surface of the substrate layer facing away from the epitaxial structure, and the third electrode has the same electrical property as the second electrode.

[0044] Beneficial effect: The N-type electrode designed on the back of the laser structure is conducive to the laser structure adapting to different packaging scenarios at the application end and improving the compatibility of the laser structure at the application end.

[0045] In the second aspect, the present invention also provides a vertical cavity surface emitting laser structure, including: a substrate layer, an epitaxial structure, an oxide layer, an ion injection region and a current injection region, the epitaxial structure is formed on one side surface of the substrate layer, the epitaxial structure includes a first reflector layer, a first confinement layer, an active layer, a second confinement layer and a second reflector layer stacked in sequence, the epitaxial structure has a light emitting region, and an oxide groove is formed on the side of the light emitting region away from the substrate layer, the oxide groove extends from the second reflector layer to the first reflector layer; the oxide layer is formed in the second reflector layer of the light emitting region, the oxide layer has an oxide hole; the current injection region is located in the light emitting region, the ion injection region surrounds the current injection region, and the projection area of the current injection region on the substrate layer covers the projection area of the oxide hole on the substrate layer.

[0046] Beneficial effects: The vertical cavity surface emitting laser structure of the present invention accurately forms an ion implantation region surrounding the current injection region and the oxidation hole, with high reliability. The oxidation layer with the oxidation hole is combined with the ion implantation region to improve the bandwidth performance and transmission rate of the laser structure. The ion implantation region is formed in the epitaxial structure outside the projection region of the oxidation hole to ensure the reliability of the oxidation hole and the oxidation layer. The central region surrounded by the ion implantation region forms a current injection region for laser emission. The ion implantation region is a high-resistance region relative to the current injection region, which can effectively confine the lateral current, reduce the lateral expansion of the current, increase the effective injected current. At the same time, ion implantation can improve the doping characteristics of the epitaxial structure, thereby reducing the parasitic parameters of the laser structure itself and effectively improving the bandwidth and the performance of the laser structure.

[0047] In an optional embodiment, the epitaxial structure includes a light emitting region, a first electrode region, a connection region connecting the light emitting region and the first electrode region, and a second electrode region. The second electrode region is isolated from both the first electrode region and the light emitting region.

[0048] The vertical cavity surface emitting laser structure further includes: a contact electrode layer, a passivation layer, a dielectric filling layer, a first electrode, a second electrode, a protective layer, and a third electrode. The contact electrode layer is formed on the surface of the light emitting region facing away from the substrate layer. The contact electrode layer has a first light emitting hole suitable for laser emission. The projection region of the current injection region on the substrate layer covers the projection region of the first light emitting hole on the substrate layer. The first light emitting hole is concentric with the oxidation hole, and the projection region of the first light emitting hole is larger than the projection region of the oxidation hole. The passivation layer is formed on the side of the epitaxial structure facing away from the substrate layer. The passivation layer covers the surface of the epitaxial structure, the surface of the contact electrode layer, and the inner wall surface of the oxidation trench. The passivation layer has a first opening exposing the contact electrode layer. The dielectric filling layer is formed on the surface of the first electrode region facing away from the substrate layer. The first electrode is formed on the surface of the epitaxial structure in the first electrode region facing away from the substrate layer. The first electrode covers the dielectric filling layer and is connected to the contact electrode layer through the first opening. The first electrode also has a second light emitting hole corresponding to the first light emitting hole. The second electrode is formed on the substrate layer of the second electrode region. The second electrode has the opposite electrical property to the first electrode. The protective layer is formed on the side of the epitaxial structure facing away from the substrate layer. The protective layer covers the light emitting region, the first electrode region, the connection region, and the second electrode region. The protective layer forms a second opening on the first electrode and a third opening on the second electrode. The third electrode is formed on the surface of the substrate layer facing away from the epitaxial structure. The third electrode has the same electrical property as the second electrode.

[0049] Beneficial effects: The first light exit hole of the contact electrode layer is used for laser emission. The contact electrode layer can be used as a positioning mark when the oxidation groove is subsequently formed, which helps to accurately form the oxidation groove. It can also be used as a seed layer to enhance the ohmic contact between the first electrode and the surface of the light exit area. The passivation layer covers the surface of the epitaxial structure away from the substrate layer to ensure the protection of the surface of these structural layers during ion implantation and even other subsequent processes, while reducing surface defects; the first opening of the passivation layer facilitates the subsequent current injection from the contact electrode layer. The dielectric filling layer is arranged on the surface of the epitaxial structure of the first electrode area, which helps to optimize the impedance matching between the first electrode and the package body in the subsequent packaging process, and can adjust the electric field distribution between the subsequent first electrode and other components, thereby reducing parasitic capacitance, reducing the number of charge and discharge times, and effectively avoiding interference with optical signal transmission, thereby improving the modulation bandwidth of VCSEL and meeting the needs of high-speed optical communication. In this embodiment, the first electrode is a front P-type electrode of the laser structure, which is formed in a large area in the first electrode area and extends to the contact electrode layer of the light exit area, and achieves good electrical connection with the contact electrode layer. The second electrode is an N-type electrode on the front of this embodiment. The second electrode area is formed by etching a selected area, and the second electrode is arranged at different positions from the first electrode and the light-emitting area, thereby improving the compatibility of the laser structure in terms of bandwidth detection and other aspects. The front N-type second electrode includes a first sub-electrode and a second sub-electrode, which are combined with the first electrode so that the front electrode scheme of the laser structure is a GSG structure. The GSG three-electrode scheme on the same surface can be compatible with different types of probes in the high-frequency test of the chip, and can also reduce parasitic capacitance when the laser is packaged and applied, thereby improving the high-speed modulation performance of the chip. The protective layer protects the interior of the laser structure from water vapor erosion and improves the reliability of the product. The second opening above the first electrode and the third opening above the second electrode are convenient for wiring to connect to an external power supply. The third electrode of the N-type electrode is designed on the back of the laser structure, which is conducive to the laser structure adapting to different packaging scenarios at the application end and improving the compatibility of the laser structure at the application end. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 is a schematic flow chart of a method for preparing a vertical cavity surface emitting laser structure according to an embodiment of the present invention;

[0052] Figure 2 is a schematic structural diagram of a contact electrode layer provided in a light-emitting region of an epitaxial structure according to an embodiment of the present invention;

[0053] Figure 3 It is a schematic structural diagram after an oxidation trench is provided in the light-emitting region according to an embodiment of the present invention;

[0054] Figure 4 It is a schematic structural diagram after an oxide layer is formed in the light-emitting region according to an embodiment of the present invention;

[0055] Figure 5 It is a schematic structural diagram after a passivation layer is formed according to an embodiment of the present invention;

[0056] Figure 6 It is a schematic structural diagram during ion implantation according to an embodiment of the present invention;

[0057] Figure 7 It is a top view schematic diagram of a vertical cavity surface emitting laser structure according to an embodiment of the present invention;

[0058] Figure 8 It is an enlarged top view schematic diagram of the light-emitting region according to an embodiment of the present invention;

[0059] Figure 9 It is a schematic structural diagram after a dielectric filling layer is formed according to an embodiment of the present invention;

[0060] Figure 10 It is a schematic structural diagram after a first opening is formed in the passivation layer according to an embodiment of the present invention;

[0061] Figure 11 It is a schematic structural diagram after a first electrode is formed according to an embodiment of the present invention;

[0062] Figure 12 It is a schematic structural diagram after a second electrode region and a second electrode are formed according to an embodiment of the present invention;

[0063] Figure 13 It is a schematic structural diagram after a protective layer is formed according to an embodiment of the present invention;

[0064] Figure 14 It is a schematic structural diagram after a second opening and a third opening are formed in the protective layer according to an embodiment of the present invention;

[0065] Figure 15 It is a structural schematic diagram of a vertical cavity surface emitting laser structure after a third electrode is formed according to an embodiment of the present invention;

[0066] Figure 16 It is a schematic diagram of a bandwidth test curve of a vertical cavity surface emitting laser structure according to an embodiment of the present invention at normal temperature and high temperature;

[0067] Figure 17 It is a schematic diagram of a relative intensity noise test curve of a vertical cavity surface emitting laser structure according to an embodiment of the present invention at normal temperature and high temperature.

[0068] Description of reference numerals:

[0069] 100, light shielding layer;

[0070] 1, substrate layer;

[0071] 2, epitaxial structure; 201, first mirror layer; 202, first confinement layer; 203, active layer; 204, second confinement layer; 205, second mirror layer; 206, oxidation trench; 207, light-emitting region; 208, first electrode region; 209, connection region; 2010, second electrode region;

[0072] 3, oxide layer; 301, oxide hole;

[0073] 4, ion implantation region;

[0074] 5, current injection region;

[0075] 6, contact electrode layer; 601, first light-emitting hole;

[0076] 7, passivation layer; 701, first opening;

[0077] 8, dielectric filling layer;

[0078] 9, first electrode; 901, second light-emitting hole;

[0079] 10, second electrode; 1001, first sub-electrode; 1002, second sub-electrode;

[0080] 11, protective layer; 1101, second opening; 1102, third opening;

[0081] 12, third electrode. Detailed implementation manners

[0082] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the convenience of description, only the parts related to the present invention are shown in the drawings, rather than all the structures. In the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concept of the present invention. Various schematic structural diagrams according to the embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element can be directly on the other layer / element, or there may be an intermediate layer / element between them. In addition, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element can be "under" the other layer / element.

[0083] With the continuous development of communication technologies, the demand for vertical-cavity surface-emitting lasers (VCSELs for short) with high speed and high bandwidth is constantly increasing. Currently, for mainstream VCSELs, the transmission rate of a single channel is generally 10 Gbit / s and 25 Gbit / s, and the rate of a few products can reach 56 Gbit / s. Such a transmission rate limits the application of VCSELs. In order to pursue a higher transmission rate, VCSEL products usually adopt the method of reducing the oxidation aperture to achieve it. However, because the oxidation rate is not linear during the wet oxidation process and there are differences in the uniformity of the oxidation process, it is difficult to precisely control the doping oxidation effect. Especially when it is desired to form oxidation holes with a smaller target aperture, it is even more difficult. Therefore, in the mass production process of VCSEL products formed by wet oxidation with a smaller target oxidation aperture, there will be a certain proportion of yield loss. At the same time, if the aperture of the oxidation hole is too small, it will also limit the light extraction efficiency, and the current density in the active region of the laser will be much higher than that of a conventional oxidation aperture product laser, resulting in a multiple increase in the internal junction temperature of the device, and ultimately shortening the service life of the device and seriously affecting the product reliability.

[0084] Based on this, referring to Figures 1 to 17 , this embodiment provides a preparation method for a vertical-cavity surface-emitting laser structure. Figure 1 As shown in the flowchart of the preparation method, the preparation method includes the following steps:

[0085] Step S101: An epitaxial structure 2 is formed on one side surface of a substrate layer 1. The epitaxial structure 2 includes a first mirror layer 201, a first confinement layer 202, an active layer 203, a second confinement layer 204, and a second mirror layer 205 that are sequentially stacked; the epitaxial structure 2 has a light-emitting region 207.

[0086] Reference Figure 2 , Exemplarily, the above-mentioned substrate layer 1 can be a gallium arsenide substrate of N-type conductive type; the first mirror layer 201 in the epitaxial structure 2 is a structure formed by alternately stacking gallium arsenide and aluminum arsenide. The first mirror layer 201 is an N-type distributed Bragg reflector (abbreviated as N-type DBR). Aluminum arsenide can be used as a heat dissipation layer to improve the reliability of the epitaxial structure 2; the material of the first confinement layer 202 is gallium aluminum arsenide, forming an N-type confinement layer; the active layer 203 is a strained quantum well structure formed by alternately arranging indium gallium arsenide and gallium aluminum arsenide. In the strained quantum well structure, the lattice constants of the two materials, indium gallium arsenide and gallium aluminum arsenide, that make up the strained quantum well do not match and are grown together using single-atom layer epitaxy technology. Due to the optimization of the physical properties of the materials, the performance of the semiconductor light-emitting device is greatly improved. Compared with the conventional quantum well structure composed of two lattice-matched materials, the degree of freedom in material selection for the strained quantum well structure in this embodiment is higher; the material of the second confinement layer 204 is gallium aluminum arsenide, forming a P-type confinement layer; the second mirror layer 205 is a structure formed by alternately stacking gallium arsenide layers and gallium aluminum arsenide layers. The second mirror layer 205 is a P-type distributed Bragg reflector (abbreviated as P-type DBR). On one side of the horizontal surface, the epitaxial structure 2 after epitaxial growth is divided into multiple different functional regions, such as including a light-emitting region 207 for emitting laser light.

[0087] Step S102: An oxidation trench 206 is formed on the side of the light-emitting region 207 facing away from the substrate layer 1. The oxidation trench 206 extends from the second mirror layer 205 into the first mirror layer 201.

[0088] Reference Figure 3 , Vertical oxidation trenches 206 can be formed in the light-emitting region 207 by means such as dry etching. Starting from the side surface of the second mirror layer 205 facing away from the substrate layer 1, the etching gradually penetrates through the second mirror layer 205, the second confinement layer 204, the active layer 203, and the first confinement layer 202 until it extends into a part of the thickness of the first mirror layer 201, so that the wall surface of the oxidation trench 206 can efficiently reflect photons, improving the effective photons of the active layer 203 and the light-emitting efficiency of the laser structure. In this embodiment, the laser light exits from the part of the light-emitting region 207 surrounded by the oxidation trench 206. Therefore, light field confinement is mainly performed on this part of the light-emitting region 207, and other parts are used as auxiliary regions to achieve the confinement effect.

[0089] Step S103 , forming an oxide layer 3 in the second reflector layer 205 in the light exiting area 207 , wherein the oxide layer 3 has oxide holes 301 .

[0090] refer to Figure 4 A wet oxidation process is used in the oxidation groove 206 to make the oxidation doping material react with the high aluminum layer in the second reflector layer 205. By controlling the reaction time, temperature, airflow and other conditions, an oxidation hole 301 with a target aperture is formed. The aperture of the oxidation hole 301 in this embodiment ranges from 6μm to 7μm. The preparation process system of the oxide layer 3 with the oxidation hole 301 having the aperture range is relatively mature, with high control accuracy and reliability, and can limit the lateral light field and improve the transmission rate of the vertical cavity surface emitting laser structure.

[0091] In step S104, ion implantation is performed on the side of the epitaxial structure 2 facing away from the substrate layer 1 to form an ion implantation region 4 and a current implantation region 5 in the epitaxial structure 2. The current implantation region 5 is located in the light emitting region 207. The ion implantation region 4 surrounds the current implantation region 5, and the projection area of the current implantation region 5 on the substrate layer 1 covers the projection area of the oxidation hole 301 on the substrate layer 1.

[0092] For example, see Figure 5 Before ion implantation, a passivation layer 7 may be formed on the entire surface of the epitaxial structure 2 to effectively protect the surface of the epitaxial structure 2 from damage. Figure 6A specially designed shielding layer 100 is arranged above the part of the epitaxial structure 2 for laser output that does not need ion implantation, and then ion implantation is performed above the surface of the entire epitaxial structure 2 on one side away from the substrate layer 1. Through the ion implantation process which is easy to accurately control, a current injection area 5 containing no implanted ions is formed under the shielding layer 100, and an ion implantation area 4 is formed in other areas of the epitaxial structure 2. Ion implantation can improve the doping characteristics of the epitaxial structure 2, reduce the parasitic parameters of the laser structure itself, and effectively improve the bandwidth and performance of the laser structure. The ion implantation area 4 forms a high-resistance area relative to the current injection area 5, and the current injection area 5 is a low-resistance area. The external ion implantation area 4 can constrain the lateral current, reduce the lateral expansion of the current, and increase the effective current injected. More importantly, the size of the shielding layer 100 needs to be able to shield the surface of the oxide hole 301. This is because ion implantation will change the doping of the second reflector layer 205 above the oxide layer 3 and the doping around the interface of the oxide layer 3. The doping near the interface of the oxide layer 3 changes, and the stress at the interface of the oxide layer 3 will also change accordingly. The surface of the oxide hole 301 is the weakest position of the oxide layer 3. Usually, more than 70% of the failures of VCSELs are related to the interface defects of the oxide hole 301. Therefore, when the projection area of the current injection zone 5 where ion implantation is not performed covers the projection area of the oxide hole 301, the surface of the oxide hole 301 in the interface of the oxide layer 3 can be protected from the influence of ion implantation, thereby ensuring the reliability of the vertical cavity surface emitting laser structure and reducing the risk of failure.

[0093] In summary, after the oxide layer 3 with a relatively large oxide hole 301 is formed by compatible conventional processes, an ion implantation process is used to form an ion implantation region 4 in the epitaxial structure 2 outside the projection area of the oxide hole 301, to ensure the reliability of the oxide hole 301 and the oxide layer 3, and the central area surrounded by the ion implantation region 4 forms a current implantation region 5 for laser emission, and the ion implantation region 4 is a high-resistance region relative to the current implantation region 5, which can effectively constrain the lateral current, reduce the lateral expansion of the current, and increase the effective current injected, and at the same time, the ion implantation can improve the doping characteristics of the epitaxial structure 2, thereby reducing the parasitic parameters of the laser structure itself, and effectively improving the bandwidth performance of the laser structure. Under the premise of forming an oxide layer 3 with a relatively large oxide hole 301, the ion implantation region 4 surrounding the current implantation region 5 and the oxide hole 301 is accurately and efficiently controlled by ion implantation, which effectively improves the reliability of the laser structure, and at the same time greatly improves the bandwidth performance and transmission rate of the laser structure.

[0094] In one embodiment, the shape of the oxide layer 3 and the shape of the current injection region 5 are both olive-shaped structures.

[0095] Figure 7 FIG. 4 shows a schematic top view of the structure of the vertical cavity surface emitting laser of this embodiment, Figure 8This is an enlarged view of the light-emitting area in the vertical cavity surface emitting laser structure. Figure 7 and Figure 8 In this embodiment, the oxidation groove 206 is set to be a partial olive ring structure, and the oxidation layer 3 is formed by doping the inner wall surface of the oxidation groove 206 inward. The oxidation layer 3 and the oxidation groove 206 have similar olive-shaped oxidation holes 301. Based on this, the shape of the shielding layer 100 is set to be a similar olive shape with a different size but the same shape as the oxidation groove 206, so that the projection shape of the current injection area 5 formed directly below the shielding layer 100 is also a similar olive shape. In this way, the olive-shaped low-resistance current injection area 5 that has not been ion-implanted is consistent with the morphology of the oxide layer 3, forming a perfect guide layer. When current is injected, the current will be uniformly guided to the oxide layer 3 and then to the active area, which not only ensures the uniformity of current injection, but also maximizes the efficiency of current injection, effectively solves the performance defects and reliability problems of the laser structure caused by abnormal current density distribution, and improves the overall photoelectric conversion efficiency. The improvement of the photoelectric conversion efficiency can fully reduce the spontaneous radiation of the laser structure during laser lasing, thereby reducing the relative intensity noise of the laser structure when it is working. According to Shannon's law, under limited bandwidth, the relative intensity noise of the laser structure can be reduced when it is working, that is, the signal-to-noise ratio and channel capacity of the laser structure are improved, and finally the bandwidth and transmission rate are effectively improved.

[0096] Furthermore, the ratio of the major axis to the minor axis of the olive-shaped structure is in the range of 6:5 to 5:4.

[0097] Limiting the ratio of the major axis to the minor axis of the olive-shaped structure to between 1.2 and 1.25, that is, limiting the shape ratio of the shielding layer 100, the oxide layer 3 and the current injection area 5, can maximize the uniformity and efficiency of current injection, effectively solve the performance defects and reliability problems of the laser structure caused by abnormal current density distribution, and at the same time improve the overall photoelectric conversion efficiency by about 5%-7%; thereby fully reducing the spontaneous radiation of the laser structure during laser lasing, reducing the relative intensity noise of the laser structure, improving the signal-to-noise ratio and channel capacity, and ultimately achieving the maximum improvement in bandwidth and transmission rate.

[0098] In one embodiment, the ion implantation on the side of the epitaxial structure 2 facing away from the substrate layer 1 includes: implanting multiple ions into the epitaxial structure 2 along a direction perpendicular to the surface of the side of the epitaxial structure 2 facing away from the substrate layer 1 .

[0099] By performing ion implantation with a variety of different types of ions, the dosage and effect of ion implantation can be effectively controlled in stages. At the same time, different ions can form different doping in the epitaxial structure 2, effectively improving doping uniformity and density.

[0100] Specifically, the step S104 of performing ion implantation on the side of the epitaxial structure 2 away from the substrate layer 1 includes:

[0101] Step S1041: Perform a first ion implantation on the side of the epitaxial structure 2 away from the substrate layer 1. The doping ions for the first ion implantation are boron ions, and the total dose of the boron ions is 1.6E+13 cm -2 , with a single implantation;

[0102] Step S1042: Perform a second ion implantation on the side of the epitaxial structure 2 away from the substrate layer 1. The doping ions for the second ion implantation are helium ions, and the total dose of the helium ions is 4E+13 cm -2 , with three separate implantations;

[0103] Step S1043: Perform a third ion implantation on the side of the epitaxial structure 2 away from the substrate layer 1. The doping ions for the third ion implantation are hydrogen ions, and the total dose of the hydrogen ions is 2E+13 cm -2 , with two separate implantations.

[0104] Conventional ion implantation schemes generally use argon ions, fluorine ions, oxygen ions and other ions as dopant ions for implantation. These ions are likely to react with the gold layer when implanting into the structure layer containing the gold layer, causing damage to the gold layer structure. The laser structure usually uses the gold layer as the electrode material or electrode contact material to ensure the conductivity. Therefore, the damage to the structure layer formed by the gold layer will also affect the reliability of the laser structure. Therefore, in this embodiment, it is innovatively adopted to include boron ions, helium ions and hydrogen ions as dopant ions for implantation, and the helium ions and hydrogen ions are implanted in separate times, further avoiding ion implantation damage, ensuring both the doping effect after ion implantation and the integrity of the structure layer formed by the gold layer, and ensuring the reliability of the laser structure.

[0105] Based on the above solution, after forming the epitaxial structure 2 on one side surface of the substrate layer 1 and before forming the oxidation trench 206 on the side of the light-emitting region 207 away from the substrate layer 1, it further includes: forming a contact electrode layer 6 on the side surface of the light-emitting region 207 away from the substrate layer 1. The contact electrode layer 6 has a first light-emitting hole 601 suitable for laser emission; the projection area of the current injection region 5 on the substrate layer 1 covers the projection area of the first light-emitting hole 601 on the substrate layer 1. The first light-emitting hole 601 is concentric with the oxidation hole 301, and the projection area of the first light-emitting hole 601 is larger than the projection area of the oxidation hole 301.

[0106] Reference Figure 2After forming the epitaxial structure 2 on the substrate layer 1, a contact electrode layer 6 is firstly provided on the epitaxial structure 2 in the light emitting area 207. The contact electrode layer 6 is provided in a circular ring structure, and the hollowed-out portion in the middle forms a first light emitting hole 601 for laser emission. The formed contact electrode layer 6 can also be used as a positioning mark when subsequently forming the oxidation trench 206, which is helpful for accurately forming the oxidation trench 206. Figure 6 The first light output hole 601 of the formed contact electrode layer 6 should be concentric with the oxidation hole 301 of the oxidation layer 3, and the aperture of the first light output hole 601 should be larger than the aperture of the oxidation hole 301, so as to ensure that after subsequent processes, the output laser after being restricted by the oxidation hole 301 can still be emitted from the first light output hole 601 to the greatest extent.

[0107] Exemplarily, the width of the annular contact electrode layer 6 of the present embodiment ranges from 13 μm to 17 μm, the aperture of the first light output hole 601 ranges from 30 μm to 40 μm, and the distance between the edge of the current injection zone 5 and the outer edge of the contact electrode layer 6 can be set to -0.5 μm to 1 μm. That is to say, the current injection zone 5 can be slightly extended outside the contact electrode layer 6, or it can be located within a certain width within the outer edge of the contact electrode layer 6, as long as the current injection zone 5 that has not been ion-implanted can cover the surface of the oxidation hole 301.

[0108] refer to Figures 4 to 6 After forming the oxide layer 3 in the second reflector layer 205 in the light emitting area 207 and before performing ion implantation on the side of the epitaxial structure 2 away from the substrate layer 1, it also includes: forming a passivation layer 7 on the side of the epitaxial structure 2 away from the substrate layer 1, and the passivation layer 7 covers the surface of the epitaxial structure 2, the surface of the contact electrode layer 6 and the inner wall surface of the oxidation groove 206.

[0109] Specifically, the passivation layer 7 can be made of silicon nitride material, and the passivation layer 7 completely covers the surface of the epitaxial structure 2 facing away from the substrate layer 1, including the surface of the contact electrode layer 6 and the inner wall of the oxidation groove 206, so as to ensure the protection of the surface of these structural layers during ion implantation and even other subsequent process steps, while reducing surface defects.

[0110] refer to Figure 7 The epitaxial structure 2 of this embodiment further comprises a first electrode region 208 and a connection region 209 connecting the light emitting region 207 and the first electrode region 208 . The first electrode region 208 is suitable for connecting to an external power source.

[0111] The light emitting area 207 and the first electrode area 208 of this embodiment are connected through the connection area 209. The first electrode area 208 is used for direct wiring connection to the external power supply to pass the electrical excitation. The electrical excitation enters the light emitting area through the connection area 209, so that the active area of the light emitting area generates photons, thereby forming laser emission. Such a structural setting can make the first electrode area 208 have more external connection possibilities and improve the scope of application. It should be noted that the light emitting area 207, the connection area 209 and the first electrode area 208 of this embodiment are as follows: Figure 7 The cross-sectional views of different structures are arranged in the same perspective for the convenience of illustration. Figures 2 to 15 In addition to Figure 7 and Figure 8 All the cross-sectional diagrams except for the above do not represent the actual positional relationship of each region, but are only used to illustrate the relevant structural layers. For example, the interface diagram of the light-emitting region 207 may be along Figure 7 The cross-sectional diagram is taken along line aa, while the cross-sectional diagram of the first electrode region 208 is taken along line bb.

[0112] Based on this, see Figure 9 , after step S104 of performing ion implantation on the side of the epitaxial structure 2 facing away from the substrate layer 1, the method further includes:

[0113] Step S105 , forming a dielectric filling layer 8 on a surface of the first electrode region 208 that is away from the substrate layer 1 .

[0114] Specifically, the dielectric filling layer 8 is laid on the surface of the epitaxial structure 2 of the second electrode area 2010, and the material of the dielectric filling layer 8 includes one or more of benzocyclobutene resin (BCB), poly-p-phenylenebenzobisoxazole fiber (PBO) and polyimide (PI). In the field of high-speed optical communication, the dielectric filling layer 8 is arranged on the surface of the epitaxial structure 2 of the first electrode area 208, which helps to optimize the impedance matching between the first electrode 9 and the package body in the subsequent packaging process. The dielectric constants of the above-mentioned materials are small, and the electric field distribution between the subsequent first electrode 9 and other components can be adjusted, thereby reducing parasitic capacitance, reducing the number of charge and discharge times, and effectively avoiding interference with optical signal transmission, thereby improving the modulation bandwidth of VCSEL and meeting the needs of high-speed optical communication.

[0115] In addition, the dielectric filling layer 8 also has the following advantages in many aspects: First, it flattens the surface of the first electrode region 208, enhances the uniformity of subsequent metal electrode deposition, avoids local short circuits or open circuits, improves the performance and reliability of the first electrode 9, and at the same time can also avoid problems such as surface unevenness, material non-uniformity or optical defects, which may cause wavefront distortion, beam divergence angle increase, etc. during the propagation of laser light, and effectively improves the beam quality. Second, by setting the dielectric filling layer 8 on the surface of the first electrode region 208, simply raising the entire first electrode region 208 can meet the specific optical, electrical or mechanical performance requirements in fields such as 3D sensing and optical communication, improve the matching with other optical components or circuit layers, and obtain better beam quality, higher coupling efficiency or a more compact package structure. Third, the above-mentioned several materials have good insulation properties and form an effective insulating isolation layer on the surface of the first electrode region 208, which can prevent electrical problems such as leakage and short circuits between the surface of the first electrode region 208 and surrounding components, and improve the electrical performance and reliability of the VCSEL laser structure. Third, enhance mechanical properties and strength: By setting the above-mentioned materials to fill and raise the first electrode region 208, due to the good flexibility and adhesion of the above-mentioned materials, a strong connection layer is formed between the first electrode 9 and other materials, effectively dispersing and buffering the strain generated when the laser structure is subjected to mechanical stress, thereby improving the overall mechanical strength of the laser structure. Fourth, improve thermal expansion matching: The thermal expansion coefficients of the above-mentioned materials have certain adjustability and adaptability, which can improve the thermal expansion matching between the materials of each layer of the laser structure. When the temperature changes, the thermal stress between the materials of each layer can be effectively reduced, ensuring that the VCSEL can work stably and reliably in different working temperature environments. Fifth, optimize optical performance and reduce light absorption and scattering: The above-mentioned materials have low absorption coefficients and scattering coefficients for the laser wavelength emitted by the VCSEL, which can effectively reduce the light absorption and scattering losses during the propagation of laser light in the first electrode region 208. The VCSEL can output more energy in the form of laser light, thereby improving the luminous efficiency and output power.

[0116] After the step S105 of forming the dielectric filling layer 8 on the surface of the first electrode region 208 facing away from the substrate layer 1, it further includes:

[0117] Step S106, removing a part of the passivation layer 7 on the contact electrode layer 6 to form a first opening 701 that exposes the contact electrode layer 6 in the passivation layer 7.

[0118] Reference Figure 10 , exemplarily, the passivation layer 7 on the contact electrode layer 6 can be removed by dry etching, so as to perform current injection from the contact electrode layer 6 subsequently.

[0119] Step S107: Form a first electrode 9 on the first electrode region 208 of the epitaxial structure 2. The first electrode 9 covers the dielectric filling layer 8 and is connected to the contact electrode layer 6 through the first opening 701. The first electrode 9 also has a second light-emitting hole 901 corresponding to the first light-emitting hole 601.

[0120] Reference Figure 11 , Exemplarily, the first electrode 9 is a composite metal layer stacked with three layers of titanium / platinum / gold. The titanium is in direct contact with the contact electrode layer 6 to improve the contact strength. The first electrode 9 is the positive P-type electrode of the laser structure in this embodiment. The first electrode 9 is formed over a large area on the first electrode region 208 and extends to the contact electrode layer 6 in the light-emitting region 207, achieving good electrical connection with the contact electrode layer 6. The contact electrode layer 6 can also serve as a seed layer to enhance the ohmic contact between the first electrode 9 and the surface of the light-emitting region 207. It should be noted that the first electrode 9 does not cover the first light-emitting hole 601, and a second light-emitting hole 901 is formed in the region corresponding to the first light-emitting hole 601, forming a light-emitting path convenient for laser output.

[0121] Reference Figure 12 , In one embodiment, after step S107 of forming the first electrode 9 on the first electrode region 208 of the epitaxial structure 2, it further includes:

[0122] Step S108: Etch away a part of the epitaxial structure 2 to expose a part of the substrate layer 1 to form a second electrode region 2010. The second electrode region 2010 is isolated from both the first electrode region 208 and the light-emitting region 207.

[0123] Step S109: Form a second electrode 10 on the substrate layer 1 of the second electrode region 2010. The second electrode 10 has an opposite electrical property to the first electrode 9.

[0124] Exemplarily, the second electrode 10 of this embodiment is a composite metal layer stacked with multiple layers such as gold / germanium / nickel / gold. The second electrode 10 is the N-type electrode on the front side of this embodiment. By etching in a selected area to form the second electrode region 2010, the second electrode 10 and the first electrode 9 are arranged at different positions in the light-emitting region, improving the compatibility of the laser structure in aspects such as bandwidth detection.

[0125] Further, reference Figure 7 , The second electrode 10 includes a first sub-electrode 1001 and a second sub-electrode 1002. The first sub-electrode 1001, the second sub-electrode 1002, and the first electrode 9 form a GSG structure. The first sub-electrode 1001 and the second sub-electrode 1002 are respectively arranged on both sides of the first electrode 9, and the connection lines with the first electrode 9 form an L-shaped structure. The light-emitting region 207 is located between the first sub-electrode 1001 and the second sub-electrode 1002.

[0126] Specifically, in this embodiment, two front N-type electrodes are arranged, that is, the second electrode 10 includes a first sub-electrode 1001 and a second sub-electrode 1002. The front electrode scheme of the laser structure is a GSG structure. The scheme of three GSG electrodes on the same surface can be compatible with different types of probes in the high-frequency test of the chip. It can also reduce parasitic capacitance in laser packaging applications and improve the high-speed modulation performance of the chip.

[0127] refer to Figure 13 and Figure 14 , after step S108 of forming the second electrode 10 in the second electrode region 2010, further comprising:

[0128] In step S1010, a protective layer 11 is formed on the side of the substrate layer 1 facing away from the substrate layer 1, and the protective layer 11 covers the light emitting area 207, the first electrode area 208, the connection area 209 and the second electrode area 2010. The protective layer 11 forms a second opening 1101 on the first electrode 9, and the protective layer 11 forms a third opening 1102 on the second electrode 10.

[0129] For example, the protective layer 11 is made of aluminum oxide, and the entire front side of the laser structure is covered with the protective layer 11 to protect the inside of the laser structure from water vapor erosion and improve the reliability of the product. Then, an opening is set above the first electrode 9 and the second electrode 10 to facilitate wire bonding to an external power source.

[0130] refer to Figure 15 After step S109 of forming a protective layer 11 on a side of the substrate layer 1 facing away from the substrate layer 1, the preparation method of this embodiment further includes:

[0131] Step S1011, thinning a surface of the substrate layer 1 that is away from the substrate layer 1;

[0132] Step S1012 , forming a third electrode 12 on a surface of the substrate layer 1 facing away from the epitaxial structure 2 , wherein the third electrode 12 has the same electrical property as the second electrode 10 .

[0133] Exemplarily, the third electrode 12 is a composite metal layer formed by multiple layers of metals such as gold / germanium / nickel / gold to form a back N-type electrode. The N-type electrode is designed on the back of the laser structure, which is beneficial for the laser structure to adapt to different packaging scenarios at the application end and improve the compatibility of the laser structure at the application end.

[0134] refer to Figure 7 , Figure 8 and Figure 15, this embodiment also provides a vertical cavity surface emitting laser structure, which is obtained by using the preparation method of the above vertical front-emitting laser structure, and includes: a substrate layer 1, an epitaxial structure 2, an oxide layer 3, an ion implantation region 4, and a current injection region 5. The epitaxial structure 2 is formed on one side surface of the substrate layer 1. The epitaxial structure 2 includes a first mirror layer 201, a first confinement layer 202, an active layer 203, a second confinement layer 204, and a second mirror layer 205 that are sequentially stacked. The epitaxial structure 2 has a light-emitting region 207, and an oxidation trench 206 is formed on the side of the light-emitting region 207 facing away from the substrate layer 1. The oxidation trench 206 extends from the second mirror layer 205 into the first mirror layer 201; the oxide layer 3 is formed in the second mirror layer 205 of the light-emitting region 207, and the oxide layer 3 has an oxidation hole 301; the current injection region 5 is located in the light-emitting region 207, the ion implantation region 4 surrounds the current injection region 5, and the projection area of the current injection region 5 on the substrate layer 1 covers the projection area of the oxidation hole 301 on the substrate layer 1.

[0135] In the vertical cavity surface emitting laser structure of this embodiment, the ion implantation region 4 that precisely surrounds the current injection region 5 and the oxidation hole 301 has high reliability. The combination of the oxide layer 3 having the oxidation hole 301 and the ion implantation region 4 improves the bandwidth and transmission rate of the laser structure. The ion implantation region 4 is formed in the epitaxial structure 2 outside the projection area of the oxidation hole 301 to ensure the reliability of the oxidation hole 301 and the oxide layer 3. The central region surrounded by the ion implantation region 4 forms a current injection region 5 for laser emission. The ion implantation region 4 is a high-resistance region relative to the current injection region 5, which can effectively confine the lateral current, reduce the lateral expansion of the current, increase the effective injected current. At the same time, ion implantation can improve the doping characteristics of the epitaxial structure 2, thereby reducing the parasitic parameters of the laser structure itself and effectively improving the bandwidth and the performance of the laser structure.

[0136] In one embodiment, the shape of the oxide layer 3 is similar to the shape of the current injection region 5 and is an olive-shaped structure; the ratio range of the long axis to the short axis of the olive-shaped structure is 6:5 to 5:4, which maximally improves the uniformity and efficiency of current injection, effectively solves the problems of performance defects and reliability caused by abnormal current density distribution in the laser structure, and at the same time increases the overall photoelectric conversion efficiency by about 5%-7%; thereby fully reducing the spontaneous emission of the laser structure during laser emission, reducing the relative intensity noise of the laser structure, improving the signal-to-noise ratio and the channel capacity, and finally achieving the maximum improvement in bandwidth and transmission rate.

[0137] In one embodiment, the epitaxial structure 2 includes a light-emitting region 207, a first electrode region 208, a connection region 209 connecting the light-emitting region 207 and the first electrode region 208, and a second electrode region 2010. The second electrode region 2010 is isolated from both the first electrode region 208 and the light-emitting region 207.

[0138] In this embodiment, the light-emitting region 207 and the first electrode region 208 are connected through a connection region 209. The first electrode region 208 and the second electrode region 2010 are used for directly wire-bonding to connect an external power supply to input an electrical excitation, so that the first electrode region 208 and the second electrode region 2010 have more external connection possibilities and improve the applicable range.

[0139] The vertical cavity surface emitting laser structure of this embodiment further includes: a contact electrode layer 6, a passivation layer 7, a dielectric filling layer 8, a first electrode 9, a second electrode 10, a protective layer 11, and a third electrode 12. The contact electrode layer 6 is formed on the surface of the light-emitting region 207 facing away from the substrate layer 1. The contact electrode layer 6 has a first light-emitting hole 601 suitable for laser emission. The projection area of the current injection region 5 on the substrate layer 1 covers the projection area of the first light-emitting hole 601 on the substrate layer 1. The first light-emitting hole 601 is concentric with the oxidation hole 301, and the projection area of the first light-emitting hole 601 is larger than the projection area of the oxidation hole 301; the passivation layer 7 is formed on the side of the epitaxial structure 2 facing away from the substrate layer 1. The passivation layer 7 covers the surface of the epitaxial structure 2, the surface of the contact electrode layer 6, and the inner wall surface of the oxidation trench 206. The passivation layer 7 has a first opening 701 exposing the contact electrode layer 6; the dielectric filling layer 8 is formed on the surface of the first electrode region 208 facing away from the substrate layer 1; the first electrode 9 is formed on the surface of the epitaxial structure 2 in the first electrode region 208 facing away from the substrate layer 1. The first electrode 9 covers the dielectric filling layer 8 and is connected to the contact electrode layer 6 through the first opening 701. The first electrode 9 also has a second light-emitting hole 901 corresponding to the first light-emitting hole 601; the second electrode 10 is formed on the substrate layer 1 of the second electrode region 2010. The second electrode 10 has the opposite electrical property to the first electrode 9; the protective layer 11 is formed on the side of the epitaxial structure 2 facing away from the substrate layer 1. The protective layer 11 covers the light-emitting region 207, the first electrode region 208, the connection region 209, and the second electrode region 2010. The protective layer 11 forms a second opening 1101 on the first electrode 9. The protective layer 11 forms a third opening 1102 on the second electrode 10; the third electrode 12 is formed on the surface of the substrate layer 1 facing away from the epitaxial structure 2. The third electrode 12 has the same electrical property as the second electrode 10.

[0140] Specifically, the first light exit hole 601 of the contact electrode layer 6 is used for laser emission. The contact electrode layer 6 can be used as a positioning mark when the oxidation groove 206 is subsequently formed, which helps to accurately form the oxidation groove 206. It can also be used as a seed layer to enhance the ohmic contact between the first electrode 9 and the surface of the light exit area 207. The passivation layer 7 covers the surface of the epitaxial structure 2 away from the substrate layer 1 to ensure the protection of the surface of these structural layers during ion implantation and even other subsequent processes, while reducing surface defects; the first opening 701 of the passivation layer 7 facilitates the subsequent current injection from the contact electrode layer 6. The dielectric filling layer 8 is arranged on the surface of the epitaxial structure 2 in the first electrode area 208, which helps to optimize the impedance matching between the first electrode 9 and the package body in the subsequent packaging process, and can adjust the electric field distribution between the subsequent first electrode 9 and other components, thereby reducing parasitic capacitance, reducing the number of charge and discharge times, and effectively avoiding interference with optical signal transmission, thereby improving the modulation bandwidth of the VCSEL and meeting the needs of high-speed optical communication. The first electrode 9 is a front P-type electrode of the laser structure in this embodiment, which is formed in a large area on the first electrode region 208 and extends to the contact electrode layer 6 of the light-emitting region 207 to achieve good electrical connection with the contact electrode layer 6. The second electrode 10 is an N-type electrode on the front of this embodiment. The second electrode region 2010 is formed by etching a selected area, and the second electrode 10 is arranged at different positions with the first electrode 9 and the light-emitting region, thereby improving the compatibility of the laser structure in terms of bandwidth detection and the like. The front N-type second electrode 10 includes a first sub-electrode 1001 and a second sub-electrode 1002, which are combined with the first electrode 9, so that the front electrode scheme of the laser structure is a GSG structure. The scheme of the three GSG electrodes on the same surface can be compatible with different types of probes in the high-frequency test of the chip, and can also reduce parasitic capacitance when the laser is packaged and applied, thereby improving the high-speed modulation performance of the chip. The protective layer 11 protects the inside of the laser structure from water vapor erosion, thereby improving the reliability of the product. The second opening 1101 above the first electrode 9 and the third opening 1102 above the second electrode 10 are convenient for wire bonding to connect to an external power supply. The third electrode 12 of the N-type electrode is designed on the back of the laser structure, which is beneficial for the laser structure to adapt to different packaging scenarios at the application end and improve the compatibility of the laser structure at the application end.

[0141] The further functional description of each of the above modules is the same as that of the above corresponding embodiments and will not be repeated here.

[0142] Figure 16 Schematic diagram of bandwidth test curves of the vertical cavity surface emitting laser structure at room temperature and high temperature in this embodiment, the horizontal axis is the bandwidth frequency, the unit is Ghz, the left horizontal axis is the relative power intensity of the laser structure, the right side shows the test temperature, the upper curve is the bandwidth test curve at room temperature, the lower curve is the bandwidth test curve at high temperature, Figure 16As can be seen from the dotted line in the middle, for the vertical cavity surface emitting laser structure of this embodiment, when the operating current is 8 mA, the bandwidth frequency at room temperature (25 °C) is tested to be as high as 32 GHz, and the bandwidth frequency at high temperature (85 °C) is also as high as 25 GHz. It can be obtained that the bandwidth frequency of the vertical cavity surface emitting laser structure of this embodiment is significantly improved compared with the bandwidth frequency of 15 GHz to 23 GHz of conventional devices.

[0143] Figure 17 This is a schematic diagram of the relative intensity noise test curves of the vertical cavity surface emitting laser structure of this embodiment at room temperature and high temperature. The abscissa is the bandwidth frequency, the left abscissa is the relative noise intensity, with the unit of dB / Hz, and the right side shows the test temperature. The upper curve is the relative intensity noise test curve at room temperature, and the lower curve is the relative intensity noise test curve at high temperature. From Figure 17 it can be obtained that for the vertical cavity surface emitting laser structure of this embodiment, when the operating current is 8 mA and the bandwidth frequency is about 25 GHz, when testing the intensity noise intensity at room temperature (25 °C) and high temperature (85 °C), the relative intensity noise at room temperature is lower than -144 dB / Hz, and the relative intensity noise at high temperature is lower than -142 dB / Hz. Compared with the relative intensity noise of -135 dB / Hz to -120 dB / Hz of conventional devices, the relative intensity noise is significantly reduced.

[0144] In the above description, technical details such as the layout and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of the required shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not exactly the same as the methods described above. In addition, although the above embodiments are described separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0145] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for preparing a vertical cavity surface emitting laser structure, characterized in that, Comprising: An epitaxial structure is formed on one surface of a substrate layer. The epitaxial structure includes a first mirror layer, a first confinement layer, an active layer, a second confinement layer, and a second mirror layer that are sequentially stacked. The epitaxial structure has a light-emitting region. An oxidation trench is formed on the side of the light-emitting region facing away from the substrate layer. The oxidation trench extends from the second mirror layer into the first mirror layer. An oxide layer is formed in the second mirror layer of the light-emitting region. The oxide layer has oxidation holes. Ion implantation is performed on the side of the epitaxial structure facing away from the substrate layer to form an ion implantation region and a current injection region in the epitaxial structure. The current injection region is located in the light-emitting region. The ion implantation region surrounds the current injection region. And the projection area of the current injection region on the substrate layer covers the projection area of the oxidation hole on the substrate layer.

2. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 1, characterized in that, The shape of the oxide layer and the shape of the current injection region are both olive-shaped structures.

3. The method for manufacturing a vertical cavity surface emitting laser according to claim 2, characterized in that, The ratio range of the major axis to the minor axis of the olive-shaped structure is 6:5 to 5:

4.

4. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 1, characterized in that, The ion implantation on the side of the epitaxial structure facing away from the substrate layer includes: performing multiple ion implantations on the epitaxial structure along a direction perpendicular to the surface of the side of the epitaxial structure facing away from the substrate layer.

5. The preparation method of the vertical cavity surface emitting laser structure according to claim 4, characterized in that, The ion implantation on the side of the epitaxial structure facing away from the substrate layer includes: Perform a first ion implantation on the side of the epitaxial structure facing away from the substrate layer. The doping ions for the first ion implantation are boron ions, and the total dose of the boron ions is 1.6E+13 cm -2 , and it is a single implantation; A second ion implantation is performed on a side of the epitaxial structure away from the substrate layer. The doping ions for the second ion implantation are helium ions, and the total dose of the helium ions is 4E+13 cm -2 , and the implantation is carried out in three times; A third ion implantation is performed on a side of the epitaxial structure facing away from the substrate layer. The doping ions for the third ion implantation are hydrogen ions, and the total dose of the hydrogen ions is 2E+13 cm -2 , and the implantation is carried out in two times.

6. The preparation method of the vertical cavity surface emitting laser structure according to any one of claims 1-5, characterized in that, After forming the epitaxial structure on one surface of the substrate layer and before forming the oxidation trench on the side of the light-emitting region facing away from the substrate layer, it further includes: A contact electrode layer is formed on the side surface of the light-emitting region facing away from the substrate layer. The contact electrode layer has a first light-emitting hole suitable for laser emission. The projection area of the current injection region on the substrate layer covers the projection area of the first light-emitting hole on the substrate layer. The first light-emitting hole is concentric with the oxidation hole, and the projection area of the first light-emitting hole is larger than the projection area of the oxidation hole.

7. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 6, characterized in that, After forming the oxide layer in the second mirror layer of the light-emitting region and before performing ion implantation on the side of the epitaxial structure facing away from the substrate layer, it further includes: A passivation layer is formed on the side of the epitaxial structure facing away from the substrate layer. The passivation layer covers the surface of the epitaxial structure, the surface of the contact electrode layer, and the inner wall surface of the oxidation trench.

8. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 7, characterized in that, The epitaxial structure further has a first electrode region and a connection region connecting the light-emitting region and the first electrode region. The first electrode region is suitable for connecting to an external power source. After performing ion implantation on the side of the epitaxial structure facing away from the substrate layer, it further includes: forming a dielectric filling layer on the side surface of the first electrode region facing away from the substrate layer.

9. The preparation method of the vertical cavity surface emitting laser structure according to claim 8, characterized in that, After forming the dielectric filling layer on the side surface of the first electrode region facing away from the substrate layer, it further includes: Removing a part of the passivation layer located on the contact electrode layer so that the passivation layer forms a first opening exposing the contact electrode layer. A first electrode is formed on the first electrode region of the epitaxial structure, the first electrode covers the dielectric filling layer and is connected to the contact electrode layer through the first opening; the first electrode also has a second light exit hole corresponding to the first light exit hole.

10. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 9, characterized in that, After forming a first electrode on the first electrode region of the epitaxial structure, the method further includes: Etching and removing part of the epitaxial structure to expose part of the substrate layer to form a second electrode region, wherein the second electrode region is isolated from the first electrode region and the light output region; A second electrode is formed on the substrate layer in the second electrode region, wherein the second electrode has an electrical property opposite to that of the first electrode.

11. The manufacturing method of the vertical cavity surface emitting laser structure according to claim 10, characterized in that, The second electrode includes a first sub-electrode and a second sub-electrode, and the first sub-electrode, the second sub-electrode and the first electrode constitute a GSG structure; the first sub-electrode and the second sub-electrode are respectively arranged on both sides of the first electrode, and form an L-shaped structure with the connection line of the first electrode, and the light output area is located between the first sub-electrode and the second sub-electrode.

12. The method for preparing the vertical cavity surface emitting laser structure according to claim 11, characterized in that, After forming the second electrode in the second electrode region, the method further comprises: A protective layer is formed on the side of the substrate layer facing away from the substrate layer, the protective layer covers the light exit area, the first electrode area, the connection area and the second electrode area, the protective layer forms a second opening on the first electrode, and the protective layer forms a third opening on the second electrode.

13. The method for manufacturing the vertical cavity surface emitting laser structure according to claim 12, wherein, After forming a protective layer on a side of the substrate layer away from the substrate layer, the method further comprises: Thinning a surface of the substrate layer facing away from the substrate layer; A third electrode is formed on a surface of the substrate layer facing away from the epitaxial structure, and the third electrode has the same electrical property as the second electrode.

14. A vertical cavity surface emitting laser structure, characterized in that, include: substrate layer; An epitaxial structure is formed on a surface of one side of the substrate layer, the epitaxial structure comprising a first reflector layer, a first confinement layer, an active layer, a second confinement layer, and a second reflector layer stacked in sequence; the epitaxial structure has a light emitting region, and an oxidation trench is formed on a side of the light emitting region away from the substrate layer, the oxidation trench extends from the second reflector layer into the first reflector layer; an oxide layer, formed in the second reflector layer in the light exiting area, the oxide layer having oxide holes; An ion injection region and a current injection region, wherein the current injection region is located in the light exit region, the ion injection region surrounds the current injection region, and the projection region of the current injection region on the substrate layer covers the projection region of the oxidation hole on the substrate layer.

15. The vertical cavity surface emitting laser structure according to claim 14, characterized in that, The epitaxial structure comprises a light emitting region, a first electrode region, a connection region connecting the light emitting region and the first electrode region, and a second electrode region, wherein the second electrode region is isolated from the first electrode region and the light emitting region; The vertical cavity surface emitting laser structure also includes: A contact electrode layer is formed on a surface of the light-emitting region facing away from the substrate layer. The contact electrode layer has a first light-emitting hole adapted for laser emission. A projection area of the current injection region on the substrate layer covers a projection area of the first light-emitting hole on the substrate layer. The first light-emitting hole is concentric with the oxidation hole, and a projection area of the first light-emitting hole is larger than a projection area of the oxidation hole. A passivation layer is formed on a side of the epitaxial structure facing away from the substrate layer. The passivation layer covers a surface of the epitaxial structure, a surface of the contact electrode layer, and an inner wall surface of the oxidation trench. The passivation layer has a first opening exposing the contact electrode layer. A dielectric filling layer is formed on a surface of the first electrode region facing away from the substrate layer. A first electrode is formed on a surface of the epitaxial structure in the first electrode region facing away from the substrate layer. The first electrode covers the dielectric filling layer and is connected to the contact electrode layer through the first opening. The first electrode also has a second light-emitting hole corresponding to the first light-emitting hole. A second electrode is formed on the substrate layer in the second electrode region. The second electrode has an opposite electrical property to the first electrode. A protective layer is formed on a side of the epitaxial structure facing away from the substrate layer. The protective layer covers the light-emitting region, the first electrode region, the connection region, and the second electrode region. The protective layer forms a second opening on the first electrode and a third opening on the second electrode. A third electrode is formed on a surface of the substrate layer facing away from the epitaxial structure. The third electrode has the same electrical property as the second electrode.

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