A vertical cavity surface emitting laser and its preparation method

Abstract

The present invention relates to the field of semiconductor laser technology, and in particular, to a vertical cavity surface emitting laser, a semiconductor laser and a preparation method. The vertical cavity surface emitting laser comprises a substrate, an N-electrode, an N-type DBR part, an active region layer, a P-type DBR part and a P-electrode, wherein the substrate, the N-type DBR part, the active region layer, the P-type DBR part and the P-electrode are sequentially stacked from bottom to top, and the N-electrode is arranged on the substrate; a relief structure, wherein the relief structure is arranged on the light emitting surface of the laser, and the relief structure is arranged at the position corresponding to the oxidation hole. In an embodiment, a relief structure is arranged on the light emitting surface of the vertical cavity surface emitting laser, and the relief structure here serves as a transverse coupling cavity, so that photons form a photon-photon resonance (PPR) effect in the transverse coupler cavity, that is, the modulation frequency / modulation bandwidth of the VCSEL laser is increased by the transverse coupling cavity.

Description

Technical Field

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

[0002] In the field of optical communications, with the rapid development of data centers and artificial intelligence (AI), higher requirements are placed on the modulation bandwidth of VCSELs, which are used as optical interconnect light sources. To achieve high modulation bandwidth and high transmission rate, traditional VCSELs usually focus on increasing the intrinsic photon-carrier relaxation oscillation frequency, reducing the damping factor, increasing the external electrical parasitic cutoff frequency, and reducing the self-heating effect.

[0003] Among them, according to the expressions of relaxation oscillation frequency fr and damping factor ᵞ, it can be known that the relaxation oscillation frequency can be increased by increasing the light field confinement factor, differential gain and reducing the volume of the active region; the K factor can be reduced by increasing the differential gain coefficient, reducing the photon lifetime and reducing the gain compression factor. For example, in view of the intrinsic relaxation oscillation frequency and modulation bandwidth, researchers proposed to use InGaAs strained quantum wells to replace unstrained GaAs quantum wells in the active region, so that the differential gain of the quantum well is increased by two times, and a modulation bandwidth of 29GHz is achieved by using half-wavelength cavity, reducing photon volume and placing oxide holes near the quantum well to enhance carrier confinement. In addition, the light field confinement can be enhanced by reducing the diameter of the oxide aperture, which is conducive to high-speed modulation, but the reduction of the oxide aperture will bring heat dissipation problems, resulting in limited modulation rate. In view of the parasitic effects and impedance characteristics of VCSEL lasers, some researchers proposed to use distributed Bragg reflectors (DBR) modulation doping and double oxide photoelectric confinement structures to increase the parasitic cutoff frequency to 20GHz. These studies have greatly improved the high-speed modulation characteristics of VCSEL.

[0004] However, due to the intrinsic limitations of the carrier-photon resonant frequency, as well as the mutual constraints between the relaxation oscillation frequency and the damping effects on the modulation bandwidth, the modulation frequency of conventional structure VCSELs is difficult to exceed 30 GHz.

[0005] Although in terms of circuits, 28GHz bandwidth VCSEL can achieve a transmission rate of 200Gb / s through high-order optical signal modulation modes (such as pulse amplitude modulation PAM-4, PAM8) or short wavelength division multiplexing technology combined with equalization technology, the implementation of these technologies requires perfect matching of optical devices (VCSEL, PD) and driving and amplification circuits, as well as complex PCB board design, which undoubtedly increases the complexity and cost of the optical transmission chain. Summary of the invention

[0006] In view of the above problems, the present invention is proposed to provide a vertical cavity surface emitting laser and a preparation method thereof that overcome the above problems or at least partially solve the above problems.

[0007] In a first aspect, an embodiment of the present invention provides a vertical cavity surface emitting laser, comprising a substrate, an N-electrode, an N-type DBR portion, an active region layer, a P-type DBR portion and a P-electrode, wherein the substrate, the N-type DBR portion, the active region layer, the P-type DBR portion and the P-electrode are sequentially stacked from bottom to top, and the N-electrode is arranged on the substrate;

[0008] A relief structure, the relief structure being arranged on the light emitting surface of the laser, and the relief structure being arranged corresponding to the position of the oxidation hole;

[0009] Wherein, the relief structure is a ring-shaped recessed structure, and the recessed structure is configured to be a structure recessed to a certain depth from the light emitting surface toward the substrate.

[0010] Furthermore, the inner diameter of the cross section of the recessed structure is not less than the outer diameter of the cross section of the oxidation pore.

[0011] Furthermore, the cross section of the recessed structure is in the shape of a ring, and the inner diameter of the ring is controlled to be 5-7 μm, and the outer diameter is controlled to be 6-8 μm.

[0012] Furthermore, the depth of the recessed structure from the light emitting surface to the substrate is controlled to be 20-30 nm.

[0013] Furthermore, the vertical cavity surface emitting laser further comprises a dielectric layer, and the dielectric layer is arranged on the light emitting surface of the laser.

[0014] Furthermore, the dielectric layer is a stepped structure, and the dielectric layer covers the light exit hole and the relief structure respectively, so as to improve the reflectivity of the upper DBR.

[0015] Furthermore, the dielectric layer is formed by alternating Ta2O5 and SiO2, and the number of dielectric layers is controlled to be 4-6 pairs.

[0016] Furthermore, the optical thickness of the optical resonant cavity where the active region layer is located is 1 / 2 times the optical wavelength.

[0017] The second aspect also discloses a method for preparing a vertical cavity surface emitting laser, the steps comprising:

[0018] Obtaining a semiconductor laser light-emitting structure, the semiconductor laser light-emitting structure comprising a substrate, an N-type DBR portion, an active region layer, a P-type DBR portion, an N-electrode and a P-electrode;

[0019] Etching a circular ring-shaped recessed structure on the upper end surface of the P-type DBR portion to obtain a relief structure;

[0020] Next, a dielectric layer is deposited on the light emitting surface of the semiconductor laser light emitting structure, and the dielectric layer covers the relief structure to obtain a vertical cavity surface emitting laser.

[0021] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0022] A vertical cavity surface emitting laser is provided in an embodiment of the present invention. A relief structure is arranged on the light emitting surface of the vertical cavity surface emitting laser. The relief structure serves as a transverse coupling cavity, so that photons form a photon-photon resonance (PPR) effect in the transverse coupler cavity, that is, the modulation frequency / modulation bandwidth of the VCSEL laser is improved through the transverse coupling cavity.

[0023] The embodiment specifically controls the annular width of the annular recessed structure of the relief structure and the position of the relief structure relative to the oxidation hole to effectively achieve a single-mode spectrum with a large side mode suppression ratio and improve the quality of the light spot. The annular width is controlled at a certain value, so that the transverse coupled cavity (TCC) effect of the relief structure is more significant, so that the photon transverse resonance causes a detuned loading effect, effectively reducing the volume of the resonant cavity, thereby achieving bandwidth improvement.

[0024] The relief layer of the embodiment provides a lateral coupling cavity effect and can suppress high-order modes. The vertical cavity surface emitting laser of the embodiment emits high-speed modulated single-mode laser.

[0025] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0028] Figure 1 is a schematic diagram of a semiconductor laser according to an embodiment;

[0029] Figure 2is a schematic diagram of a vertical cavity surface emitting laser according to a first embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of the vertical cavity surface emitting laser of the first embodiment of the present invention from another angle;

[0031] Figure 4 is a schematic diagram of another state of the vertical cavity surface emitting laser according to the first embodiment of the present invention;

[0032] Figure 5 The present invention Figure 4 Schematic diagram from another perspective;

[0033] Figure 6 It is a schematic diagram of the modulation bandwidth of a vertical cavity surface emitting laser according to an embodiment of the present invention and a conventional vertical cavity surface emitting laser;

[0034] Figure 7 It is an experimental schematic diagram of the single-mode output of a vertical cavity surface emitting laser according to an embodiment of the present invention.

[0035] Indicated in the figure:

[0036] 100. Semiconductor laser;

[0037] 101, substrate; 102, N-type DBR portion; 103, N-electrode; 104, active region layer; 105, P-type DBR portion; 106, P-electrode; 107, oxidation restriction layer; 108, dielectric layer; 109, polymer layer 109; 110, oxidation holes; 111, relief structure;

[0038] 1080, Part 1; 1081, Part 2; 1082, Part 3. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0040] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0041] In this application, the word "exemplary" is used to mean "used as an example, illustration, or description." Any implementation described in this application as "exemplary" is not necessarily to be construed as being more preferred or advantageous than other implementations. The following description is given to enable any technician in the field to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0042] VCSEL is a semiconductor laser structure that forms an optical resonant cavity in a direction perpendicular to the semiconductor epitaxial wafer and emits a laser beam perpendicular to the substrate surface. It is widely used in consumer electronics, military, medical and other fields, such as 3D sensing, AR / VR, robots, LiDAR, consumer electronics, intelligent manufacturing, Internet of Things, data centers, etc. Specific applications include intelligent driving, video surveillance, LiDAR, machine vision, gesture recognition, face recognition, AI artificial intelligence and other fields.

[0043] The relief structure, also known as the surface relief structure, is an effective method for preparing the fundamental transverse mode VCSEL. By etching the surface relief pattern on the light-emitting surface of the device, that is, etching a certain depth in the high-order mode lasing area on the upper DBR surface of the ordinary oxidation-limited VCSEL, its mirror loss is increased, and the mirror reflectivity of the high-order mode is relatively reduced, thereby achieving the purpose of suppressing the high-order mode lasing and effectively realizing the stable output of the fundamental transverse mode.

[0044] Refer to the attached Figure 1 As shown, as an embodiment, the semiconductor laser light emitting structure may include an N-type DBR portion 102, an active region layer 104, and a P-type DBR portion 105 on a substrate 101. The semiconductor laser light emitting structure may include a III-V compound semiconductor material, for example, the semiconductor laser light emitting structure may include a GaAs-based compound semiconductor material, for example, the semiconductor laser light emitting structure material is an InGaAs material.

[0045] As an example embodiment, the substrate 101 may be a semiconductor substrate. For example, a Si substrate, a GaAs substrate, etc. may be used as the substrate. If necessary, a buffer layer and a seed layer whose material for forming the semiconductor laser light emitting structure is lattice-matched with the substrate 101 may be provided between the substrate 101 and the semiconductor laser light emitting structure.

[0046] The active region layer 104 may include multiple groups of quantum wells or quantum dots.

[0047] The N-electrode 103 may be disposed on a portion of the N-type DBR portion 102. The active region layer 104 may be provided in a region of the N-type DBR portion 102 that is not occupied by the N-electrode 103. The P-electrode 106 may be disposed on a portion of the P-type DBR portion 105.

[0048] Figure 1 The semiconductor laser light emitting structure shown is only an example and the scope of the present invention is not limited to Figure 1 The semiconductor laser light emitting structure shown in FIG. may include Figure 1 Various additional components / layers not shown.

[0049] Before describing the embodiments of the present invention in detail, the design concept of the present invention is briefly described below. Figure 2 As shown, the present invention designs a vertical cavity surface emitting laser, and a relief structure 111 is arranged on the light emitting surface of the vertical cavity surface emitting laser. The relief structure 111 is arranged on the light emitting surface of the laser, and the relief structure 111 is matched with the position of the oxidation hole. The relief structure 111 is used as a transverse coupling cavity, so that photons form a photon-photon resonance (PPR) effect in the transverse coupler cavity, that is, the modulation frequency / modulation bandwidth of the VCSEL laser is increased through the transverse coupling cavity.

[0050] The inventors of this application are continuing to study how to effectively solve the problem of poor beam quality caused by the current VCSEL multi-mode operation, which at least includes: the relief layer provides a lateral coupling cavity effect and can suppress high-order modes, so that the vertical cavity surface emitting laser of this embodiment can emit high-speed modulated single-mode laser. After a lot of repeated research, the inventors proposed the vertical cavity surface emitting laser of this application.

[0051] Refer to the attached Figure 4 As shown, in an embodiment of the present invention, a vertical cavity surface emitting laser is provided, comprising a substrate, an N-electrode, an N-type DBR portion, an active region layer, an oxidation restriction layer, a P-type DBR portion and a P-electrode, wherein the substrate, the N-type DBR portion, the active region layer, the P-type DBR portion and the P-electrode are sequentially stacked from bottom to top, and the N-electrode is arranged on the substrate;

[0052] A relief structure 111, wherein the relief structure 111 is disposed on the light emitting surface of the laser, and the relief structure 111 is disposed at a position corresponding to the oxidation hole 110;

[0053] The relief structure 111 is an annular recessed structure, the inner diameter of the cross section of the recessed structure is not less than the outer diameter of the cross section of the oxidation hole 110 , and the width of the cross section of the relief structure 111 is not greater than 1 μm.

[0054] Understandably, in the current field of optical communications, due to the intrinsic limitation of the carrier-photon resonance frequency of VCSEL, as well as the mutual restriction of the relaxation oscillation frequency and the damping effect on the modulation bandwidth, the modulation frequency of conventional structure VCSEL is difficult to exceed 30GHz. In terms of circuits, although the 28GHz bandwidth VCSEL has achieved a transmission rate of 200Gb / s through high-order optical signal modulation modes (such as pulse amplitude modulation PAM-4, PAM8) or short wavelength division multiplexing technology combined with equalization technology, the realization of these technologies requires the perfect matching of optical devices (VCSEL, PD) and driving and amplification circuits, as well as complex PCB board design, which undoubtedly increases the complexity and cost of the optical transmission chain.

[0055] An embodiment is to provide a relief structure 111 on the light emitting surface of a vertical cavity surface emitting laser, wherein the relief structure 111 serves as a transverse coupling cavity, so that photons form a photon-photon resonance (PPR) effect in the transverse coupler cavity, that is, the modulation frequency / modulation bandwidth of the VCSEL laser is increased through the transverse coupling cavity.

[0056] The embodiment specifically controls the annular width of the annular recessed structure of the relief structure 111 and the position of the relief structure 111 relative to the oxidation hole 110 to effectively achieve a single-mode spectrum with a large side mode suppression ratio and improve the quality of the light spot. The annular width is controlled at a certain value, so that the transverse coupled cavity (TCC) effect of the relief structure 111 is more significant, so that the photon transverse resonance causes a detuned loading effect, thereby achieving bandwidth improvement.

[0057] The relief layer of the embodiment provides a lateral coupling cavity effect and can suppress high-order modes. The vertical cavity surface emitting laser of the embodiment emits high-speed modulated single-mode laser.

[0058] In the embodiment, the light emitting surface is the surface from which the VCSEL emits light, that is, the surface from which the light beam generated by the VCSEL leaves the VCSEL last is considered as the light emitting surface, and the surface from which the light beam is emitted is the light exit hole.

[0059] The width of the cross section of the relief structure 111 refers to that the relief structure 111 is set as an annular recessed structure, and the lateral width of the cross section of the annular recessed structure can also be considered as the distance between the outer side and the inner side of the cross section of the annular recessed structure.

[0060] In an embodiment, since the etched area generally has a shorter resonance wavelength than the unetched area, the laser in the oxidation hole 110 can propagate laterally to the oxidation area and the relief structure 111 for reflection, thereby forming a transverse coupled cavity (TCC) effect to achieve transverse resonance, thereby achieving an increase in the modulation frequency / modulation bandwidth of the VCSEL laser.

[0061] In some embodiments, referring to Figure 5 As shown, a circular relief structure 111 is etched on the light emitting surface of the VCSEL by a photolithography process, and the difference between the outer diameter D1 and the inner diameter D0 of the circular ring is 1 μm, and the inner diameter of the circular ring is the same as the outer diameter D0 of the oxidation hole 110; in other embodiments, a circular relief structure 111 is etched on the light emitting surface of the VCSEL by a photolithography process, and the difference between the outer diameter D1 and the inner diameter D0 of the circular ring is 0.9 μm, and the inner diameter of the circular ring is smaller than the outer diameter of the oxidation hole 110; in still other embodiments, a circular relief structure 111 is etched on the light emitting surface of the VCSEL by a photolithography process, and the difference between the outer diameter D1 and the inner diameter D0 of the circular ring is 0.8 μm, and the inner diameter of the circular ring is smaller than the outer diameter of the oxidation hole 110.

[0062] Refer to the attached Figure 4 As shown, in a further embodiment, the VCSEL further includes a polymer layer 109 , the polymer layer 109 is disposed on the VCSEL, and the P electrode extends above the polymer layer 109 .

[0063] It can be understood that in the embodiment, the P electrode is extended to the top of the polymer layer 109, and the polymer layer 109 supports the P electrode, so that the P electrode is extended laterally, ensuring lateral current injection. At the same time, through the cooperation of the polymer layer 109, the parasitic capacitance of the laser is effectively reduced, which is beneficial to high-speed modulation applications.

[0064] In the embodiment, the polymer layer 109 is made of benzocyclobutene material, benzocyclobutene BCB (English name: Benzocyclobutene), the molecular formula of BCB is C8H8, which can form both thermoplastic polymers and thermosetting polymers. In this way, the polymer layer 109 has a low dielectric constant and dielectric loss, which helps to reduce the parasitic capacitance of the device. The actual manufacturing process is to deposit the P electrode on the polymer layer 109 by magnetron sputtering to ensure the matching degree of the two.

[0065] Refer to the attached Figure 4 As shown, in a further embodiment, the cross section of the recessed structure is annular, and the inner diameter of the annular is controlled to be 5-7 μm, and the outer diameter is controlled to be 6-8 μm. The depth of the recessed structure from the light emitting surface to the substrate is controlled to be 20-30 nm.

[0066] It can be understood that by controlling the width of the annular relief structure 111 within a certain range and coordinating the position of the oxidation hole 110, the transverse coupling cavity effect can be effectively achieved through the annular relief structure 111. The transverse resonance of the transverse coupling cavity effect causes a detuned loading effect and thus achieves bandwidth enhancement.

[0067] Refer to the attached Figure 5 As shown, in some embodiments, the relief structure 111 is a circular ring-shaped recessed structure, and the inner diameter D0 of the circular ring is controlled to 6μm, and the outer diameter D1 of the circular ring is controlled to 7μm, that is, the width of the circular ring is set to 1μm, and the depth of the recess of the circular ring-shaped recessed structure is set to 25 nm; in other embodiments, the relief structure 111 is a circular ring-shaped recessed structure, and the inner diameter D0 of the circular ring is controlled to 5.5μm, and the outer diameter D1 of the circular ring is controlled to 6.4μm, that is, the width of the circular ring is set to 0.9μm, and the depth of the recess of the circular ring-shaped recessed structure is set to 20nm; in still other embodiments, the relief structure 111 is a circular ring-shaped recessed structure, and the inner diameter D0 of the circular ring is controlled to 7μm, and the outer diameter D1 of the circular ring is controlled to 7.8μm, that is, the width of the circular ring is set to 0.8μm, and the depth of the recess of the circular ring-shaped recessed structure is set to 30nm.

[0068] Refer to the attached Figure 3 As shown, in a further embodiment, the VCSEL further comprises a dielectric layer 108, which is disposed on the light emitting surface of the laser. The dielectric layer 108 is a stepped structure and covers the light emitting hole and the relief structure 111 respectively.

[0069] Here, the stepped structure can be understood as the dielectric layer 108 being a non-horizontal planar structure, which can be understood as an uneven relief structure existing at the bottom of the dielectric layer. The dielectric layer is obtained by deposition, and the dielectric layer effectively improves the upward reflection.

[0070] Refer to the attached Figure 2 As shown, in a further embodiment, the dielectric layer 108 is formed by alternately stacking Ta2O5 and SiO2. The number of layers of the dielectric layer 108 is controlled to be 5-8 pairs.

[0071] In the embodiment, the dielectric layer 108 is produced by alternately stacking Ta2O5 and SiO2, and the number of stacked dielectric layers 108 is controlled to be 4-6 pairs. The dielectric layers 108 formed by the staggered stacking effectively improve the upper reflection and form effective lasing.

[0072] In some embodiments, the dielectric layer 108 is formed on the vertical cavity surface emitting laser by a plasma enhanced chemical vapor deposition (PECVD) process, wherein the dielectric layer 108 is formed by alternating 5 pairs of Ta2O5 and SiO2, i.e., a dielectric layer 108 with a ten-layer structure; in other embodiments, the dielectric layer 108 is produced on the vertical cavity surface emitting laser by a plasma enhanced chemical vapor deposition (PECVD) process, wherein the dielectric layer 108 is formed by alternating 4 pairs of Ta2O5 and SiO2, i.e., an dielectric layer 108 with an eight-layer structure; in still other embodiments, the dielectric layer 108 is produced on the vertical cavity surface emitting laser by a plasma enhanced chemical vapor deposition (PECVD) process, wherein the dielectric layer 108 is formed by alternating 6 pairs of Ta2O5 and SiO2, i.e., a dielectric layer 108 with a twelve-layer structure.

[0073] Refer to the attached Figure 3 As shown, in the embodiment further, the dielectric layer 108 includes a first part 1080, a second part 1081 and a third part 1082, and the first part 1080, the second part 1081 and the third part 1082 are arranged in a stepped structure from the oxidation hole 110 to the outside, that is, the top of the first part 1080, the second part 1081 and the third part 1082 are respectively at a height increasing from the center to the outside from the substrate.

[0074] It can be understood that in the embodiment, when the dielectric layer 108 is provided, the dielectric layer 108 covers the light emitting surface of the vertical cavity surface emitting laser, and because the dielectric layer 108 covers the light emitting hole, the relief structure 111 and the P electrode, and because the relief structure 111 is formed by etching on the light emitting surface, the dielectric layer 108 deposited on the vertical cavity surface emitting laser forms a stepped structure. By providing the dielectric layer 108, the upward reflection is improved to ensure laser lasing.

[0075] In a further embodiment, the distance difference between the end of the first portion 1080 and the end of the second portion 1081 is 20-30 nm, and the distance difference between the end of the second portion 1081 and the end of the third portion 1082 is 20-30 nm.

[0076] It is understandable that in the embodiment, since the relief structure introduces a height difference in the lateral direction, the deposited dielectric layer 108 forms a stepped structure, that is, the height difference between the first portion 1080 and the second portion 1081 is controlled to be 20-30 nm, and the height difference between the second portion 1081 and the third portion 1082 is controlled to be 20-30 nm.

[0077] In some embodiments, the dielectric layer 108 is arranged as a step structure, and the span height of the steps of the step structure is controlled to be 25nm; in other embodiments, the dielectric layer 108 is arranged as a step structure, and the span height of the steps of the step structure is controlled to be 20nm; in still other embodiments, the dielectric layer 108 is arranged as a step structure, and the span height of the steps of the step structure is controlled to be 30nm.

[0078] In a further embodiment, the optical thickness of the optical resonant cavity where the active region layer is located is 1 / 2 times the optical wavelength.

[0079] The embodiment sets a resonant cavity with a total thickness of 1 / 2 times the optical wavelength, shortens the resonant cavity to 1 / 2 times the optical wavelength, reduces the photon lifetime, increases the response bandwidth of the vertical cavity surface laser, and thus improves the rate.

[0080] For example:

[0081] In one embodiment, the vertical cavity surface emitting laser includes a P-type electrode, a P-type DBR portion, an active region layer, an oxidized limiting layer, an N-type DBR portion, an N-type electrode, a relief structure 111 and a dielectric layer 108 stacked in sequence above the substrate layer. Alternatively, in some disclosed embodiments, the vertical cavity surface emitting laser includes an N-type electrode located below the substrate layer, and a P-type DBR portion, an active region layer, an oxidized limiting portion, an N-type DBR portion and an N-type electrode, a relief structure 111 and a dielectric layer 108 stacked in sequence above the substrate layer.

[0082] In the embodiment, an oxidation restriction layer is provided on the upper part of the active region layer, an oxidation hole 110 is provided in the middle of the oxidation restriction layer, and the aperture D0 of the oxidation hole 110 is 6 μm, and the active region layer may include any one of a single quantum well layer and a multiple quantum well (MQW) layer, the optical thickness of the optical resonant cavity where the active region layer is located is 1 / 2 times the lasing wavelength, the material used for the quantum well is InGaAs material, and the barrier layer material is AlGaAs. The relief structure 111 is annular and is located on the surface of the P-type DBR part. The inner diameter D0 of the annular recessed structure is 6 μm, the outer diameter D1 is 7 μm, and the depth is 20 nm. The P-type electrode is an annular electrode, located on the surface of the P-type DBR part, located on the outside of the relief structure 111, and the inner diameter of the P-type electrode is 1 μm away from the relief structure 111. In addition, a dielectric layer 108 is provided on the top of the vertical cavity surface emitting laser, and the dielectric layer 108 is composed of five pairs of Ta2O5 / SiO2 alternating, which is used to improve the reflectivity of the P-type DBR part. In addition, a polymer layer 109 made of benzocyclobutene is provided on the side of the vertical cavity surface emitting laser, and the P-type electrode extends from the light exit hole to the top of the polymer layer 109, so that the P-type electrode is connected to the polymer layer 109.

[0083] As attached Figure 6 It can be seen that the modulation bandwidth of the vertical cavity surface emitting laser in this embodiment is greatly improved compared with the traditional vertical cavity surface emitting laser. Figure 7 Schematic diagram of the single-mode output experiment of the vertical cavity surface emitting laser of this embodiment. It can be seen that by reasonably designing the position of the relief structure 111 and coordinating the oxidation holes 110, the high-order mode can be suppressed to achieve single-mode laser output.

[0084] Based on the same inventive concept, a method for preparing a vertical cavity surface emitting laser is also disclosed, the steps comprising:

[0085] Step S001: obtaining a semiconductor laser light-emitting structure, wherein the semiconductor laser light-emitting structure comprises a substrate, an N-type DBR portion, an active region layer, a P-type DBR portion, an N-electrode and a P-electrode.

[0086] In an embodiment, an epitaxial wafer is formed on a wafer, the epitaxial wafer comprising: a substrate, an N-type DBR portion, an active region layer, an oxidation restriction layer, and a P-type DBR portion arranged in sequence from bottom to top; wherein the total thickness of the resonant cavity where the active region layer is located is 1 / 2 times the optical wavelength.

[0087] For example, the steps for preparing the epitaxial wafer of the semiconductor laser light-emitting structure are as follows:

[0088] Step S011: Grow an N-type DBR section on a substrate using metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The N-type DBR section includes AlxGa(1-x)As materials with alternating growth of high-refractive-index materials and low-refractive-index materials. Among them, in the high-refractive-index material, x = x1, and 0.05 < x1 < 0.2 is satisfied. In the low-refractive-index material, x = x2, and x2 = 1 is satisfied. The thickness of each layer of AlxGa(1-x)As material is one-quarter of the optical thickness. Among them, using AlAs binary material can effectively reduce the thermal resistance.

[0089] Step S012: Form a resonant cavity on the surface of the N-type DBR section. The resonant cavity includes an AlGaAs bulk material with a gradually changing aluminum composition. Step S013: Deposit an active region layer. The active region layer includes multiple groups of strained quantum wells containing InGaAs and AlGaAs, which are used to generate the gain required for laser. The active region layer is located at the position of the antinode of the standing wave in the cavity. After the deposition of the active region layer is completed, further grow the remaining thickness of the resonant cavity.

[0090] Step S014: Form an oxidation confinement layer above the resonant cavity. The thickness of the oxidation confinement layer is 20 - 30 nm, and the material is AlyGa(1-y)As, y = 0.98. In order to reduce the parasitic capacitance of the oxidation confinement layer, several more layers of oxidation confinement layer will be grown on the basis of the above oxidation confinement layer, and the material is AlyGa(1-y)As, y = 0.96.

[0091] Step S015: Form a P-type DBR section above the resonant cavity to complete the growth of the epitaxial wafer. The P-type DBR section includes AlyGa(1-y)As materials with alternating growth of high-refractive-index materials and low-refractive-index materials. Among them, in the high-refractive-index material, y = y1, and 0.05 < y1 < 0.2 is satisfied. In the low-refractive-index material, y = y2, and 0.8 < y2 < 0.9 is satisfied. The thickness of each layer of AlyGa(1-y)As material is one-quarter of the optical thickness.

[0092] Step S002: Etch a circular concave structure on the upper end face of the P-type DBR section to obtain a relief structure 111;

[0093] After the growth of the epitaxial wafer is completed, use electron beam lithography (EBL) to etch a circular relief structure. The inner diameter of the circular ring is 6 μm, the outer diameter is 7 μm, and the depth is 20 - 30 nm.

[0094] In the embodiment, after etching the epitaxial wafer to form a relief structure, a P-type electrode is obtained by a deposition process using Ti / Pt / Au material. The inner diameter of the P-type electrode, which is a contact metal ring, is larger than the outer diameter of the relief structure, that is, the inner diameter of the P-type electrode is 7 μm, and the width of the metal ring of the P-type electrode is 3 μm.

[0095] In the embodiment, after depositing the P-type annular electrode, a polymer layer 109 and a P-type electrode on the polymer need to be made. When making the polymer layer 109, since the polymer layer 109 is located below the P-type electrode, the polymer layer 109 needs to be made first. In the embodiment, the polymer layer 109 adopts a new type of active resin, and the material used is benzocyclobutene BCB (English name: Benzocyc l obutene), and the molecular formula of BCB is C8H8. The polymer layer 109 can form a thermoplastic polymer or a thermosetting polymer. In this way, the polymer layer 109 has a low dielectric constant and dielectric loss, which helps to reduce the device capacitance. Next, the material Ti / Pt / Au is used to deposit the P-type electrode using a magnetron sputtering process. The P-type electrode is a P-type electrode that contacts the metal ring. The inner diameter of the P-type electrode is larger than the outer diameter of the relief structure, that is, the inner diameter of the P-type electrode is 7μm, and the width of the metal ring of the P-type electrode is 3μm.

[0096] Step S003: Next, a dielectric layer 108 is obtained by deposition on the light emitting surface of the semiconductor laser light emitting structure. The dielectric layer 108 covers the relief structure to obtain a vertical cavity surface emitting laser.

[0097] In the embodiment, the epitaxial wafer after obtaining the P-type electrode through the deposition process is alternately deposited on the vertical cavity surface emitting laser by using the plasma enhanced chemical vapor deposition process to obtain five pairs of dielectric layers 108. The dielectric layer 108 covers the surface of the relief structure, the surface of the light exit hole and the surface of the P-type electrode part, and the dielectric layer 108 can provide stronger upward reflection to form laser lasing.

[0098] Finally, an N-type electrode is formed on the upper side of the epitaxial wafer substrate by evaporation using Au / Ge / Ni / Au materials. In another embodiment, the N-type electrode can also be disposed on the lower side of the substrate by evaporation.

[0099] Based on the same inventive concept, a method for using a vertical cavity surface emitting laser is also disclosed, including a method for using the vertical cavity surface emitting laser in the field of data centers.

[0100] The specific examples and beneficial effects of the method described in this embodiment can be found in the description of the semiconductor laser mentioned above, and will not be described in detail here.

[0101] Obviously, various changes and modifications may be made to the present invention by those skilled in the art without departing from the spirit and scope of the present invention. The present disclosure is not limited to the precise structure described above and shown in the accompanying drawings, and various changes and modifications may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims. Thus, if these changes and modifications of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and modifications.

Claims

1. A vertical cavity surface emitting laser, characterized in that: It comprises a substrate, an N-electrode, an N-type DBR part, an active region layer, a P-type DBR part and a P-electrode, wherein the substrate, the N-type DBR part, the active region layer, the P-type DBR part and the P-electrode are sequentially stacked from bottom to top, and the N-electrode is arranged on the substrate; A relief structure, the relief structure being arranged on the light emitting surface of the laser, and the relief structure being arranged corresponding to the position of the oxidation hole; The relief structure is an annular concave structure, the inner diameter of the cross section of the concave structure is not less than the outer diameter of the cross section of the oxidation hole, and the width of the cross section of the relief structure is not greater than 1 μm; the lateral coupling cavity effect of the relief structure is improved by the position coordination of the relief structure relative to the oxidation hole; The vertical cavity surface emitting laser further comprises a dielectric layer, which is arranged on the light emitting surface of the laser and covers the light emitting hole and the relief structure respectively.

2. The vertical cavity surface emitting laser according to claim 1, characterized in that: The cross section of the concave structure is a circular ring, and the inner diameter of the circular ring is controlled to be 5-7 μm, and the outer diameter is controlled to be 6-8 μm.

3. The vertical cavity surface emitting laser according to claim 1, characterized in that: The depth of the recessed structure from the light emitting surface to the substrate is controlled to be 20-30 nm.

4. The vertical cavity surface emitting laser according to claim 1, characterized in that: The dielectric layer has a stepped structure.

5. The vertical cavity surface emitting laser according to claim 1 or 4, characterized in that: The dielectric layer is formed by alternately stacking Ta2O5 and SiO2, and the number of dielectric layers is controlled to be 4-6 pairs.

6. The vertical cavity surface emitting laser according to claim 1, characterized in that: The optical thickness of the optical resonant cavity where the active region layer is located is 1 / 2 times the optical wavelength.

7. A method for preparing a vertical cavity surface emitting laser, characterized in that the steps include: Obtaining a semiconductor laser light-emitting structure, the semiconductor laser light-emitting structure comprising a substrate, an N-type DBR portion, an active region layer, a P-type DBR portion, an N-electrode and a P-electrode; A circular concave structure is etched on the upper end surface of the P-type DBR portion to obtain a relief structure; Wherein, the relief structure is arranged on the light emitting surface of the laser, and the relief structure is arranged corresponding to the position of the oxidation hole; The relief structure is an annular concave structure, the inner diameter of the cross section of the concave structure is not less than the outer diameter of the cross section of the oxidation hole, and the width of the cross section of the relief structure is not greater than 1 μm; the lateral coupling cavity effect of the relief structure is improved by the position coordination of the relief structure relative to the oxidation hole; Next, a dielectric layer is deposited on the light emitting surface of the semiconductor laser light emitting structure, and the dielectric layer covers the relief structure to obtain a vertical cavity surface emitting laser; Wherein, the dielectric layer is arranged on the light emitting surface of the laser and covers the light emitting hole and the relief structure respectively.

8. A method for using a vertical cavity surface emitting laser, characterized in that: A method for using the vertical cavity surface emitting laser described in any one of claims 1 to 6 in the field of optical communications.

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