A high-speed external modulation laser chip and a preparation method thereof

Abstract

The application relates to the field of optical communication, in particular to a high-speed external modulation laser chip and a preparation method, the chip comprising a modulator module and a laser module on the same substrate and the same first cladding layer, the laser module comprising a first confinement layer, a first multiple quantum well structure and a second confinement layer; the modulator module comprising a third confinement layer, a second multiple quantum well structure and a fourth confinement layer; the first confinement layer is butted with the third confinement layer, the first multiple quantum well structure is butted with the second multiple quantum well structure, and the second confinement layer is butted with the fourth confinement layer; a diffusion barrier layer is buried around the first multiple quantum well structure and the second multiple quantum well structure. The diffusion barrier layer is buried around the multiple quantum well structure of the chip, the diffusion barrier layer can effectively prevent the diffusion of Zn, reduce the leakage current, and improve the modulation bandwidth of the chip.

Description

Technical Field

[0001] This invention relates to the field of optical communication, and in particular to a high-speed externally modulated laser chip and its fabrication method. Background Technology

[0002] In recent years, with the rapid development of 5G mobile communication and the explosive growth of client network traffic, emerging Internet applications such as cloud computing and big data have placed higher demands on network bandwidth. The arrival of 5G mobile communication will further accelerate this trend, thus urgently requiring the development of high-density, high-speed, and low-cost Ethernet systems. Electro-absorption modulated lasers (EMLs), as a stable and reliable light source, play an important role in long-distance high-speed fiber optic transmission systems. How to improve the power, bandwidth, and transmission capacity of EMLs is currently a hot research topic. At present, to obtain excellent characteristics such as low threshold voltage, high power, and high modulation bandwidth, EMLs typically use compressive strain quantum wells. However, the accumulation of repeated compressive strain in the quantum well can lead to the destruction of the crystal structure and the formation of defects. To improve the response bandwidth of EMLs, Fe doping is often introduced into the quantum well material. However, the diffusion of Zn in Fe doping leads to a large leakage current, which actually reduces the response bandwidth.

[0003] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the technical problem to be solved by the present invention is to provide a high-speed externally modulated laser chip and its fabrication method. The purpose is to solve the technical problem that the accumulation of compressive strain in the quantum well leads to the destruction of the quantum well structure and the large leakage current reduces the chip response bandwidth when only using compressive strain quantum wells.

[0005] To achieve the above objectives, according to one aspect of the present invention, a high-speed externally modulated laser chip is provided. The chip includes a modulator module and a laser module located on the same substrate 10 and the same first cladding layer 11. The laser module includes a first confinement layer 14, a first multiple quantum well structure 15, and a second confinement layer 16. The modulator module includes a third confinement layer 17, a second multiple quantum well structure 18, and a fourth confinement layer 19.

[0006] The first confinement layer 14 is docked with the third confinement layer 17, the first multiple quantum well structure 15 is docked with the second multiple quantum well structure 18, and the second confinement layer 16 is docked with the fourth confinement layer 19.

[0007] A growth diffusion barrier layer 27 is buried around the first quantum well structure 15 and the second quantum well structure 18.

[0008] Preferably, the laser module further includes a first filling layer 23 and a first insulating layer 24, wherein:

[0009] The second confinement layer 16 is a shallow ridge waveguide, and the first filling layer 23 fills both sides of the second confinement layer 16;

[0010] The first insulating layer 24 is located between the second limiting layer 16 and the first filling layer 23, and the first insulating layer 24 is flush with the first filling layer 23.

[0011] Preferably, the modulator module further includes a second filling layer 25 and a second insulating layer 26, wherein:

[0012] The fourth confinement layer 19 is a deep ridge waveguide, and the second filling layer 25 fills both sides of the fourth confinement layer 19.

[0013] The second insulating layer 26 is located between the third limiting layer 17 and the second filling layer 25, and the second filling layer 25 and the second insulating layer 26 are flush in height.

[0014] Preferably, the laser module and the modulator module further include a second cladding layer 12, a first contact layer 13, and an electrode layer 31, wherein:

[0015] In the laser module and the modulator module, the second covering layer 12 is located below the first contact layer 13, and the first contact layer 13 is covered by the electrode layer 31.

[0016] Preferably, in the laser module, the second confinement layer 16 is located below the second cladding layer 12; in the modulator module, the fourth confinement layer 19 is located below the second cladding layer 12.

[0017] Preferably, the first multiple quantum well structure 15 has 5-10 quantum wells and the width of the quantum wells is 1.6μm-1.7μm, the second multiple quantum well structure 18 has 10-15 quantum wells and the width of the quantum wells is 1.6μm-1.7μm; the bandgap wavelength of the first multiple quantum well structure 15 is smaller than the bandgap wavelength of the second multiple quantum well structure 18.

[0018] Preferably, in the first multiple quantum well structure 15 and the second multiple quantum well structure 18, the material of the quantum well is represented as In. x Ga 1-x As y P 1-y, where x and y take values ​​between 0 and 1.

[0019] Preferably, the end face of the laser module facing away from the modulator module is coated with a reflective film 21, and the end face of the modulator module facing away from the laser module is coated with a transmissive film 22, wherein the reflective film 21 has a reflectivity greater than 99%, and the transmissive film 22 has a reflectivity less than 0.01%.

[0020] Preferably, a grating is formed on the surface of the second confinement layer 16, the grating being one of a quarter-laser wavelength phase-shift grating, a chirped grating, and a surface grating.

[0021] In a second aspect, the present invention provides a method for fabricating a high-speed externally modulated laser chip, the method being used to fabricate the high-speed externally modulated laser chip mentioned in the first aspect, the method comprising:

[0022] A first cladding layer 11, a first confinement layer 14, a first multiple quantum well structure 15, and a second confinement layer 16 are sequentially epitaxially formed on the substrate 10.

[0023] A laser module is defined by photolithography on the second confinement layer 16 and a masking layer is grown to mask the laser module. Then, the portion other than the laser module is etched away, and the etching continues down to the first covering layer 11.

[0024] Then, a third confinement layer 17, a second multiple quantum well structure 18, and a fourth confinement layer 19 are sequentially epitaxially formed on the first covering layer 11. A modulator module is defined by photolithography on the fourth confinement layer 19. A diffusion barrier layer 27 is buried around the first multiple quantum well structure 15 and the second multiple quantum well structure 18.

[0025] After the laser module and the modulator module are flush in height, an isolation trench is formed between the laser module and the modulator module by etching.

[0026] The laser module emits a laser beam, which is transmitted through the isolation trench to the modulator module, where the modulator module modulates the laser beam.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention employs an alternating growth method of compressive strain quantum wells and tensile strain quantum wells to compensate for strain superlattice growth. It utilizes the low threshold, high power, high modulation characteristics, and excellent temperature characteristics of compressive strain quantum wells while using tensile strain quantum wells to alleviate compressive strain and prevent the lattice structure from being destroyed.

[0029] 2. The present invention grows a diffusion barrier layer around the multi-quantum well structure of the chip. The diffusion barrier layer can effectively prevent the diffusion of Zn, reduce leakage current, and improve the modulation bandwidth of the chip. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0031] Figure 1 This is a schematic diagram of a high-speed externally modulated laser chip provided by the present invention;

[0032] Figure 2 This is a schematic diagram of the process for fabricating a high-speed externally modulated laser chip provided by the present invention;

[0033] Figure 3 This is a schematic diagram of a laser module in a high-speed externally modulated laser chip provided by the present invention;

[0034] Figure 4 This is a schematic diagram of the modulator module in a high-speed externally modulated laser chip provided by the present invention;

[0035] Figure 5 This is a schematic diagram of the test results of a high-speed externally modulated laser chip provided by the present invention;

[0036] Figure 6 This is a schematic diagram of the test results of a high-speed externally modulated laser chip provided by the present invention;

[0037] Figure 7 This is a flowchart of a high-speed externally modulated laser chip fabrication method provided by the present invention.

[0038] 10-Substrate; 11-First cladding layer; 12-Second cladding layer; 13-First contact layer; 14-First confinement layer; 15-First multi-quantum well structure; 16-Second confinement layer; 17-Third confinement layer; 18-Second multi-quantum well structure; 19-Fourth confinement layer; 21-High reflectivity film; 22-Transmittance film; 23-First filling layer; 24-First insulating layer; 25-Second filling layer; 26-Second insulating layer; 27-Diffusion barrier layer; 31-Electrode layer. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0040] In the description of this invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] Example 1:

[0043] To achieve excellent characteristics such as low threshold voltage, high power, and high modulation bandwidth in currently fabricated electroabsorption modulated lasers, this embodiment employs an alternating growth method of compressive strain quantum wells and tensile strain quantum wells to compensate for strained superlattice growth. While utilizing the low threshold voltage, high power, high modulation characteristics, and excellent temperature characteristics of the compressive strain quantum wells, the tensile strain quantum wells alleviate the compressive strain and prevent lattice structure destruction. Simultaneously, to improve the response bandwidth, this embodiment embeds a diffusion barrier layer around the quantum well structure to effectively prevent Zn diffusion, reduce leakage current, and thus enhance the response bandwidth.

[0044] This embodiment provides a high-speed externally modulated laser chip, which includes a modulator module and a laser module located on the same substrate 10 and the same first cladding layer 11, such as... Figures 1 to 4 As shown, where:

[0045] like Figure 3 As shown, the laser module includes a first confinement layer 14, a first multi-quantum-well structure 15, and a second confinement layer 16. Figure 4 As shown, the modulator module includes a third confinement layer 17, a second multi-quantum well structure 18, and a fourth confinement layer 19.

[0046] like Figure 1 As shown, the first confinement layer 14 is docked with the third confinement layer 17, the first multi-quantum well structure 15 is docked with the second multi-quantum well structure 18, and the second confinement layer 16 is docked with the fourth confinement layer 19.

[0047] like Figure 3 and Figure 4 As shown, a growth diffusion barrier layer 27 is buried around the first multi-quantum well structure 15 and the second multi-quantum well structure 18.

[0048] exist Figure 2 In Figure (a), a first cladding layer 11, a first confinement layer 14, a first multiple quantum well structure 15, and a second confinement layer 16 are epitaxially deposited on substrate 10 through a single metal-organic chemical vapor deposition (MOCVD) process. The first cladding layer 11 is made of n-InP material, which can match the lattice of substrate 10. Figure 2 In Figure (b), a laser module is photolithographically defined on the second confinement layer 16, and a masking layer is grown to mask the laser module. Figure 2 In Figure (c), the portion excluding the laser module is etched away, down to the first cladding layer 11. Figure 2 In Figure (d), a third confinement layer 17, a second multiple quantum well structure 18, and a fourth confinement layer 19 are sequentially epitaxially formed on the first covering layer 11. A modulator module is then defined by photolithography on the fourth confinement layer 19. In this embodiment, the diffusion barrier layer 27 is a Ru diffusion barrier layer. The Ru diffusion barrier layer can effectively prevent the diffusion of Zn, reduce leakage current, and improve the modulation bandwidth of the chip.

[0049] After the laser module and modulator module are fabricated, a metal electrode layer is finally created on top. The isolation trench is created by etching the portion of the metal electrode layer between the two modules until the insulating layer is reached. This trench disconnects the laser module from the modulator module, achieving electrical isolation and preventing electrical crosstalk between the two modules. After the isolation trench is formed, the light intensity can be modulated by applying a voltage to the electrodes in the modulator module, which then outputs the modulated laser light.

[0050] In this first embodiment, the laser module and modulator module of the high-speed externally modulated laser chip are integrated on the same substrate through docking coupling technology, such as... Figure 1 As shown. The advantage of using docking coupling technology is that the structural parameters such as bandgap wavelength, refractive index, and thickness of the laser module and modulator module can be optimized independently, maximizing the performance of both regions and thus improving the overall performance of the integrated device. The high-speed externally modulated laser chip proposed in this embodiment has the characteristics of low threshold, high power, wide bandwidth, and stable reliability, which greatly improves the R&D and processing capabilities of high-end optoelectronic integrated chips in my country, laying the foundation for the application of integrated optoelectronic chips in 5G medium- and long-distance optical communication solutions.

[0051] To ensure the output performance of the laser, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 3 As shown, the laser module further includes a first filling layer 23 and a first insulating layer 24, wherein:

[0052] The second confinement layer 16 is a shallow ridge waveguide, and the first filling layer 23 fills both sides of the second confinement layer 16;

[0053] The first insulating layer 24 is located between the second limiting layer 16 and the first filling layer 23, and the first insulating layer 24 is flush with the first filling layer 23.

[0054] In this first embodiment, as Figure 3 As shown, the second confinement layer 16 of the laser module employs a shallow ridge waveguide with a ridge width of 1.8 μm to ensure the output performance of the laser. In this embodiment, the first filling layer 23 uses an insulating resin material, such as benzocyclobutene (BCB). The first filling layer 23 fills both sides of the shallow ridge waveguide to form a buried heterostructure, which improves the optical confinement factor and facilitates the matching of the output optical field of the laser module and the output optical field of the modulator module, thereby improving the coupling efficiency.

[0055] To improve the optical confinement factor of the modulator, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 4 As shown, the modulator module further includes a second filling layer 25 and a second insulating layer 26, wherein:

[0056] The fourth confinement layer 19 is a deep ridge waveguide, and the second filling layer 25 fills both sides of the fourth confinement layer 19.

[0057] The second insulating layer 26 is located between the third limiting layer 17 and the second filling layer 25, and the second filling layer 25 and the second insulating layer 26 are flush in height.

[0058] In this first embodiment, the fourth confinement layer 19 in the modulator module employs a deep ridge waveguide with a ridge width of 1.8 μm. The deep ridge waveguide is used to improve the optical confinement factor of the modulator. Insulating resin material is filled on both sides of the deep ridge waveguide to reduce the parasitic capacitance of the modulator. The second filling layer 25 uses an insulating resin material, such as benzocyclobutene (BCB). The second filling layer 25 fills both sides of the deep ridge waveguide, forming a buried heterostructure, further improving the optical confinement factor. This increases the transmission bandwidth of the high-speed externally modulated laser chip without reducing the quantum well width. Furthermore, the improved optical confinement factor prevents output beam distortion in the high-speed externally modulated laser chip.

[0059] To achieve the loading of electrical signals, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 3 and Figure 4 As shown, the laser module and the modulator module further include a second cladding layer 12, a first contact layer 13, and an electrode layer 31, wherein:

[0060] In the laser module and the modulator module, the second covering layer 12 is located below the first contact layer 13, and the first contact layer 13 is covered by the electrode layer 31.

[0061] In this first embodiment, the second coating layer 12 is made of P-InP material, which can match the lattice of the first contact layer 13. The first contact layer 13 is made of InGaAs material. The material chosen for the first contact layer 13 is to better load electrical signals and enable the laser chip to work normally. Furthermore, a first electrode is attached to the top surface of the first contact layer 13, and a second electrode is attached to the bottom surface of the substrate 10. The first electrode and the second electrode are mutually exclusive in order to form a circuit loop. However, the first electrode and the second electrode themselves do not have polarity; their polarity is defined only by the applied current and voltage.

[0062] To ensure that the multi-quantum-well structure emits laser light normally, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figures 2 to 4 As shown, in the laser module, the second confinement layer 16 lies below the second cladding layer 12; in the modulator module, the fourth confinement layer 19 lies below the second cladding layer 12. The second confinement layer 16 and the first confinement layer 14 together constitute the optical confinement layer of the first multiple quantum well structure 15. They form a "sandwich" structure with the first multiple quantum well structure 15. Light emitted from the first multiple quantum well structure 15 reflects back and forth between the confinement layers and is finally output from the side. If only one side is confined, the light emitted from the quantum well will leak from the other side, and laser output will be impossible. Similarly, the third confinement layer 17 and the fourth confinement layer 19 together constitute the optical confinement layer of the second multiple quantum well structure 18. Light emitted from the second multiple quantum well structure 18 reflects back and forth between the confinement layers and is finally output from the side.

[0063] In order to obtain good laser characteristics, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme. Specifically, the number of quantum wells in the first multi-quantum well structure 15 is 5-10, and the width of the quantum wells is 1.6μm-1.7μm; the number of quantum wells in the second multi-quantum well structure 18 is 10-15, and the width of the quantum wells is 1.6μm-1.7μm.

[0064] The bandgap wavelength of the first multiple quantum well structure 15 is smaller than that of the second multiple quantum well structure 18.

[0065] The number and width of the quantum wells are calculated. Since the first quantum well structure 15 is a laser module that emits laser light, and the second quantum well structure 18 is a modulator module that absorbs and modulates the laser light, the bandgap wavelength of the first quantum well structure 15 is smaller than that of the second quantum well structure 18. The high-speed externally modulated laser chip provided in this embodiment operates by having the laser light emitted by the laser module absorbed and modulated by the modulator module before being emitted again. If the bandgap wavelength of the first quantum well structure 15 is greater than or equal to that of the second quantum well structure 18, the emitted light will be completely absorbed, and the laser chip will not function properly.

[0066] To optimize the performance of the electroabsorption modulator, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 3 and Figure 4 As shown, in the first multiple quantum well structure 15 and the second multiple quantum well structure 18, the material of the quantum well can be represented as In. x Ga 1-x As y P 1-y Where x and y take values ​​between 0 and 1, and a diffusion barrier layer 27 is buried and grown around the first quantum well structure 15 and the second quantum well structure 18. The diffusion barrier layer 27 surrounds the quantum well structure. In this embodiment, the diffusion barrier layer 27 is a Ru diffusion barrier layer. The Ru diffusion barrier layer can effectively prevent the diffusion of Zn, reduce leakage current, and improve the modulation bandwidth of the chip.

[0067] By designing the composition, thickness, and period number of the wells and barriers in a multi-quantum-well structure, a high-performance absorption material can be artificially fabricated. This material exhibits a steep absorption edge, good thermal stability, and a significant shift of the exciton absorption peak towards longer wavelengths when a suitable reverse electric field is applied. Furthermore, the absorption spectrum is reversibly reduced after the external electric field is removed. The material of the quantum well is denoted as In. x Ga 1-x As y P 1-y The values ​​of x and y are between 0 and 1. By adjusting the values ​​of x and y, the quantum well material can be optimized, thereby optimizing the performance of the electroabsorption modulator.

[0068] In this first embodiment, Fe doping is introduced into the quantum well material, and a Ru diffusion barrier layer is grown buried within it. The purpose of Fe doping in the quantum well is to reduce parasitic capacitance and improve high-frequency characteristics. However, Zn is often introduced during the Fe doping process, and the disordered diffusion of Zn in the quantum well deteriorates its performance. To address this, this first embodiment grows a Ru diffusion barrier layer buried within the quantum well, effectively suppressing Zn diffusion, reducing leakage current, and improving high-frequency response characteristics.

[0069] To achieve absorption modulation followed by laser emission, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 1 As shown, the laser module's end face facing away from the modulator module is coated with a reflective film 21, and the modulator module's end face facing away from the laser module is coated with a transmissive film 22. The reflective film 21 has a reflectivity greater than 99%, and the transmissive film 22 has a reflectivity less than 0.01%. Both ends of the laser can emit laser light, but in this embodiment, the laser chip operates by having the laser emitted from the laser module absorbed and modulated by the modulator module before being emitted. Therefore, the laser must be emitted from the modulator module end face. Thus, a high-reflectivity film is coated on one end of the laser module to reflect all the laser light back after reaching the end face, while a high-transmissivity film is coated on the other end of the modulator module to transmit all the laser light after reaching the end face, thereby achieving the purpose of absorption, modulation, and then emission of the laser light.

[0070] To facilitate the lasing of the laser, in conjunction with the embodiments of the present invention, there is also a preferred implementation scheme, specifically, as follows: Figure 1 As shown, a grating is formed on the surface of the second confinement layer 16, and the grating is one of a quarter-laser wavelength phase-shift grating, a chirped grating, and a surface grating.

[0071] In this first embodiment, a quarter-laser wavelength phase-shifting grating is formed on the surface of the second confinement layer 16 because a quarter-laser wavelength phase-shifting grating is most conducive to the lasing of the laser and has good single-mode performance.

[0072] The chip provided in this embodiment has been tested under the following conditions: the laser emitted by the laser chip is coupled through an optical fiber in air at room temperature, and the other end of the optical fiber is connected to the test equipment to obtain the test results directly from the test equipment.

[0073] Test results are as follows Figure 5 and Figure 6 As shown, the chip has a threshold current of less than 15mA and an output power of nearly 6mW at a current of 100mA, exhibiting the characteristics of low threshold and high power. The chip also has a large transmission capacity, with a bandwidth of up to 43.2GHz when the modulator bias is 0.9V, demonstrating wide bandwidth and stable reliability.

[0074] Example 2:

[0075] This second embodiment provides a method for fabricating a high-speed externally modulated laser chip. This method is used to fabricate the high-speed externally modulated laser chip mentioned in the first embodiment, such as... Figure 7 As shown, the method includes:

[0076] S101: A first cladding layer 11, a first confinement layer 14, a first multi-quantum well structure 15, and a second confinement layer 16 are sequentially epitaxially formed on the substrate 10.

[0077] like Figure 2 In Figure (a), a docking coupling method is used. Specifically, a first cladding layer 11, a first confinement layer 14, a first multiple quantum well structure 15, and a second confinement layer 16 are epitaxially deposited on the substrate 10 through a single metal-organic chemical vapor deposition (MOCVD). The first cladding layer 11 is made of n-InP material, which can match the lattice of the substrate 10.

[0078] S201: The laser module is defined by photolithography on the second confinement layer 16 and a masking layer is grown to mask the laser module. Then, the portion other than the laser module is etched away and etched down to the first covering layer 11.

[0079] like Figure 2 In Figure (b), a laser module is photolithographically defined on the second confinement layer 16, and a masking layer is grown to mask the laser module, as shown below. Figure 2 In Figure (c), the part excluding the laser module is etched away and etched down to the first cladding layer 11.

[0080] S301: Then, a third confinement layer 17, a second multiple quantum well structure 18, and a fourth confinement layer 19 are sequentially epitaxially formed on the first covering layer 11. A modulator module is defined by photolithography on the fourth confinement layer 19. A diffusion barrier layer 27 is buried around the first multiple quantum well structure 15 and the second multiple quantum well structure 18.

[0081] like Figure 2 As shown, Figure 2 In Figure (d), a third confinement layer 17, a second multiple quantum well structure 18, and a fourth confinement layer 19 are sequentially epitaxially formed on the first covering layer 11. A modulator module is then defined by photolithography on the fourth confinement layer 19. In this embodiment, the diffusion barrier layer 27 is a Ru diffusion barrier layer. The Ru diffusion barrier layer can effectively prevent the diffusion of Zn, reduce leakage current, and improve the modulation bandwidth of the chip.

[0082] S401: After the laser module and the modulator module are flush at the same height, an isolation trench is formed between the laser module and the modulator module by etching.

[0083] After the laser module and modulator module are fabricated, a metal electrode layer is fabricated on top. The isolation trench is fabricated by etching the part between the two modules on the metal electrode layer until the insulating layer is reached. The isolation trench disconnects the laser module and modulator module, achieving electrical isolation and preventing electrical crosstalk between the two modules.

[0084] S501: The laser module emits a laser, which is transmitted to the modulator module through the isolation trench, and the modulator module modulates the laser.

[0085] After the isolation trench is formed, the intensity of the light can be modulated by applying a voltage to the electrodes in the modulator module, and the modulator module will output the modulated laser.

[0086] In this second embodiment, the laser module and modulator module of the high-speed externally modulated laser chip are integrated on the same substrate through docking coupling technology, such as... Figure 5 As shown, docking coupling technology allows for independent optimization of structural parameters such as bandgap wavelength, refractive index, and thickness of the laser module and modulator module, maximizing the performance of both regions and thus improving the overall performance of the integrated device. The high-speed externally modulated laser chip proposed in this embodiment features low threshold voltage, high power, wide bandwidth, and stable reliability.

[0087] This second embodiment employs an alternating growth method of compressive strain quantum wells and tensile strain quantum wells to compensate for strained superlattice growth. It utilizes the low threshold voltage, high power, high modulation characteristics, and excellent temperature characteristics of the compressive strain quantum wells while using tensile strain quantum wells to alleviate compressive strain and prevent lattice structure destruction. In this embodiment, a diffusion barrier layer is buried around the quantum well structure. This diffusion barrier layer effectively prevents Zn diffusion, reduces leakage current, and improves the chip's modulation bandwidth.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed externally modulated laser chip, characterized in that, The chip includes a modulator module and a laser module located on the same substrate (10) and the same first cladding layer (11). The laser module includes a first confinement layer (14), a first multi-quantum well structure (15), and a second confinement layer (16). The modulator module includes a third confinement layer (17), a second multi-quantum well structure (18), and a fourth confinement layer (19). The first confinement layer (14) is docked with the third confinement layer (17), the first multi-quantum well structure (15) is docked with the second multi-quantum well structure (18), and the second confinement layer (16) is docked with the fourth confinement layer (19). A diffusion barrier layer (27) is buried around the first multi-quantum well structure (15) and the second multi-quantum well structure (18); wherein, the first multi-quantum well structure (15) and the second multi-quantum well structure (18) are grown by alternating growth of compressive strain quantum wells and tensile strain quantum wells, Fe doping is introduced into the quantum well material, the diffusion barrier layer (27) surrounds the multi-quantum well structure, the diffusion barrier layer (27) is a Ru diffusion barrier layer, the Ru diffusion barrier layer can effectively prevent the diffusion of Zn introduced during the Fe doping process; the purpose of doping Fe in the quantum well is to reduce parasitic capacitance; The laser module further includes a first filling layer (23) and a first insulating layer (24). The second confinement layer (16) is a shallow ridge waveguide. The first filling layer (23) fills both sides of the second confinement layer (16) to form a buried heterostructure and improve the optical confinement factor. The first insulating layer (24) is located between the second confinement layer (16) and the first filling layer (23). The first insulating layer (24) is flush with the height of the first filling layer (23).

2. The high-speed externally modulated laser chip according to claim 1, characterized in that, The modulator module further includes a second filling layer (25) and a second insulating layer (26), wherein: The fourth confinement layer (19) is a deep ridge waveguide, and the second filling layer (25) fills both sides of the fourth confinement layer (19); The second insulating layer (26) is located between the third limiting layer (17) and the second filling layer (25), and the second filling layer (25) and the second insulating layer (26) are flush in height.

3. The high-speed externally modulated laser chip according to claim 1, characterized in that, The laser module and the modulator module further include a second cladding layer (12), a first contact layer (13), and an electrode layer (31), wherein: In the laser module and the modulator module, the second covering layer (12) is located below the first contact layer (13), and the first contact layer (13) is covered by the electrode layer (31).

4. The high-speed externally modulated laser chip according to claim 3, characterized in that, In the laser module, the second confinement layer (16) is located below the second cladding layer (12); in the modulator module, the fourth confinement layer (19) is located below the second cladding layer (12).

5. The high-speed externally modulated laser chip according to claim 3, characterized in that, The first multi-quantum well structure (15) has 5-10 quantum wells and the width of the quantum wells is 1.6μm-1.7μm. The second multi-quantum well structure (18) has 10-15 quantum wells and the width of the quantum wells is 1.6μm-1.7μm. The bandgap wavelength of the first multi-quantum well structure (15) is smaller than that of the second multi-quantum well structure (18).

6. The high-speed externally modulated laser chip according to claim 1, characterized in that, In the first multiple quantum well structure (15) and the second multiple quantum well structure (18), the material of the quantum well is represented as In. x Ga 1-x As y P 1-y , where x and y take values ​​between 0 and 1.

7. The high-speed externally modulated laser chip according to claim 1, characterized in that, The laser module has a reflective film (21) on its end face facing away from the modulator module, and the modulator module has a transmissive film (22) on its end face facing away from the laser module. The reflective film (21) has a reflectivity greater than 99%, and the transmissive film (22) has a reflectivity less than 0.01%.

8. The high-speed externally modulated laser chip according to claim 1, characterized in that, A grating is formed on the surface of the second confinement layer (16), the grating being one of a quarter-laser wavelength phase-shift grating, a chirped grating, and a surface grating.

9. A method for fabricating a high-speed externally modulated laser chip, characterized in that, The method is used to prepare the high-speed externally modulated laser chip according to any one of claims 1 to 8, and the method includes: A first cladding layer (11), a first confinement layer (14), a first multi-quantum well structure (15), and a second confinement layer (16) are sequentially epitaxially formed on a substrate (10). The laser module is defined by photolithography on the second confinement layer (16) and a masking layer is grown to mask the laser module. Then, the part other than the laser module is etched away and etched to the first covering layer (11). Then, a third confinement layer (17), a second multiple quantum well structure (18) and a fourth confinement layer (19) are sequentially epitaxially formed on the first covering layer (11). A modulator module is defined by photolithography on the fourth confinement layer (19). A growth diffusion barrier layer (27) is buried around the first multiple quantum well structure (15) and the second multiple quantum well structure (18). After the laser module and the modulator module are flush in height, an isolation trench is formed between the laser module and the modulator module by etching. The laser module emits a laser beam, which is transmitted through the isolation trench to the modulator module, where the modulator module modulates the laser beam.

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