Preparation method and structure of novel electro-absorption modulated laser

Abstract

The invention discloses a preparation method and a structure of a novel electro-absorption modulated laser, and the method comprises the steps: symmetrically dividing a substrate into a double-end modulation region, a gain region, a grating region and a phase region, manufacturing a first mask pattern on the surface of the gain region, growing an active layer containing a quantum well structure in a mask gap through a selective region epitaxy technology, forbidden band red shift of the gain region is realized; manufacturing a mask covering the gain region and the modulation region, and etching a non-functional region to expose the substrate; a passive material with a wider band gap is grown in the exposed substrate area in a butt joint mode, and a photon limiting structure is formed; manufacturing a sampling grating through electron beam direct writing, growing a cladding layer and a contact layer, and etching an inverted table shallow ridge waveguide; and finally, etching an electrical isolation trench and manufacturing a double-sided electrode to complete device integration. Through the selective area epitaxial growth technology, active materials with two forbidden bandwidths of the gain area and the modulation area are achieved through one-time epitaxial growth, and a solution with extremely low cost is provided for the wavelength tunable electro-absorption modulated laser.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic integrated devices, and in particular to a preparation method and structure of a novel electro-absorption modulated laser. Background Art

[0002] With the rapid development of optical communications and artificial intelligence, semiconductor lasers and their integrated devices are evolving from core communications components to key photonic components for AI. Their performance breakthroughs will directly impact the competitiveness of next-generation communications and intelligent systems. To increase transmission speeds and fully utilize optical network infrastructure to meet the demands of high precision and reliability, laser design and fabrication processes require more precise control to ensure optimal performance.

[0003] Existing technologies offer increased system flexibility and capacity with a wide wavelength tuning range, which is crucial for applications requiring dynamic wavelength resource adjustment. Integrated devices combining tunable lasers and electro-absorption modulation offer solutions to address modulation bandwidth and multi-wavelength utilization. However, current wide-wavelength lasers are mostly fabricated by integrating the modulator via a material docking scheme. This method requires two material growth processes, resulting in high manufacturing costs and insufficient practical application requirements.

[0004] Therefore, the present invention provides a novel preparation method and structure of an electro-absorption modulated laser. By adopting the selective epitaxial growth technology, active materials with two bandgap widths in the gain region and the modulation region are realized by a single epitaxial growth, which greatly reduces the power consumption and manufacturing cost of the integrated chip and provides a low-cost solution for wavelength-tunable electro-absorption modulated lasers. Summary of the Invention

[0005] In view of this, the present invention provides a novel preparation method and structure of an electro-absorption modulated laser. The method adopts the selective epitaxial growth technology to realize active materials with two bandgap widths in the gain region and the modulation region through a single epitaxial growth, thereby solving the technical problem in the prior art that the manufacturing cost of wavelength tunable electro-absorption modulated laser is too high, which is not conducive to large-scale production.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a novel electro-absorption modulated laser, comprising: Performing a surface layout on the substrate, dividing the substrate surface into a first modulation region, a first front grating region, a first gain region, a first phase region, a back grating region, a second phase region, a second gain region, a second grating region, and a second modulation region in sequence along the length direction; wherein the first and second front grating regions, the first and second gain regions, the first and second modulation regions, and the first and second phase regions are arranged symmetrically with respect to the longitudinal axis of the substrate center; A first mask pattern is formed on the surface of the first and second gain regions of the substrate, wherein the first mask pattern is two stripe patterns with the same length as the first and second gain regions and a preset spacing and width; growing an active layer on a portion of the substrate surface excluding the first mask pattern, and then etching away the first mask pattern; Making a second mask pattern located in the first and second gain regions and the first and second modulation regions on the surface of the active layer, and removing the active layer outside the second mask pattern by etching technology; The passive material growth of the rear grating region, the first and second front grating regions, the first and second phase regions, and the substrate portion after the first mask pattern is removed is completed by using a butt-joint growth technique; The sampled gratings are fabricated in the first front grating region, the rear grating region and the second front grating region by electron beam direct writing technology; A cladding layer and an electric contact layer are sequentially grown on the entire surface area, and an inverted shallow ridge waveguide structure is fabricated on the cladding layer and the electric contact layer; Etching electrical isolation trenches on the electrical contact layer to achieve electrical isolation between the regions; A P-side electrode is fabricated on the electrical contact layer of each region, and an N-side electrode is fabricated on the entire surface of the bottom of the substrate after the substrate is thinned, completing the laser fabrication.

[0007] Furthermore, the substrate material is N-type indium phosphide.

[0008] Furthermore, the second mask pattern is removed by using ICP dry etching technology.

[0009] Furthermore, the length of the first\second modulation zone is 150 microns, the length of the first\second gain zone is 300 microns, the length of the first\second phase zone is 100 microns, the length of the first\second grating zone is 50 microns, and the length of the rear grating zone is 500 microns.

[0010] Furthermore, the passive material is InGaAsP, and its light fluorescence wavelength is 1450nm.

[0011] Furthermore, the active layer is an InGaAlAs active layer, and its light fluorescence wavelength is 1545 nm; the active layer includes a lower confinement layer, a multi-quantum well layer and an upper confinement layer from bottom to top.

[0012] Furthermore, the multi-quantum well layer is formed by cross-growth of multiple quantum well layers and multiple barrier layers.

[0013] Furthermore, the thickness of the substrate after thinning is 110 microns.

[0014] Furthermore, the thickness of the cladding layer is 1.5 microns, the thickness of the electrical contact layer is 300 nm, and the width of the inverted shallow ridge waveguide structure is 3 microns.

[0015] On the other hand, the present invention also provides a novel electro-absorption modulated laser structure, wherein the laser is manufactured using the manufacturing method described in the above technical solution, and the laser comprises, from bottom to top, an N-side electrode, a substrate, an active layer, a cladding layer, an electrical contact layer, and a P-side electrode; The laser is divided into a first modulation area, a first front grating area, a first gain area, a first phase area, a back grating area, a second phase area, a second gain area, a second grating area and a second modulation area in sequence along the length direction starting from one side; Among them, the first\second front grating region, the first\second gain region, the first\second modulation region and the first\second phase region are symmetrically arranged with the longitudinal axis of the center of the substrate as the axis; the first front grating region, the back grating region and the second front grating region are made with sampled gratings; the cladding and the electrical contact layer have an inverted shallow ridge waveguide structure, and the electrical contact layer is etched with an electrical isolation groove to achieve electrical isolation between the regions.

[0016] Compared with the existing technology, the preparation method and structure of the new electro-absorption modulated laser proposed in the present invention have the following advantages: the method of the present invention first divides the substrate surface into a double-ended symmetrical modulation zone, a grating zone, a gain zone and a phase zone along the length direction; a strip mask pattern is made on the surface of the gain zone, and an active layer containing a quantum well structure is grown in the mask gap through the selective area epitaxy technology to achieve a red shift of the gain zone band gap; then a secondary mask covering the gain zone and the modulation zone is made, and the non-functional area is etched to expose the substrate; a passive material with a wider band gap is grown in the exposed substrate area to form a photon confinement structure; a sampling grating is made by electron beam direct writing, a cladding and a contact layer are grown, and an inverted shallow ridge waveguide is etched; finally, an electrical isolation groove is etched and double-sided electrodes are made to complete the device integration.

[0017] This method uses selective epitaxy to achieve homogeneous single-pass epitaxial growth of the gain and modulation regions, significantly reducing manufacturing costs. The passive layer and gain region bandgap are designed in tandem to achieve efficient photon confinement, supporting wide-range continuous wavelength tuning. The symmetrical functional region layout combined with an inverted ridge waveguide structure simplifies the process while improving photoelectric isolation performance and energy efficiency. This invention significantly reduces the manufacturing cost of integrated chips by utilizing selective epitaxy to achieve active materials with two bandgap widths in both the gain and modulation regions in a single epitaxial growth. This provides a low-cost solution for wavelength-tunable electro-absorption modulated lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic flow chart of a method for preparing a novel electro-absorption modulated laser provided by the present invention; Figure 2A schematic diagram of the structure of the substrate and area division provided by the present invention; Figure 3 A top view of the structure of a first mask pattern for producing selective epitaxy of a gain region on a substrate surface provided by the present invention; Figure 4 This is a schematic diagram of the structure of the laser provided by the present invention after the active layer is grown; Figure 5 A schematic structural diagram of the laser provided by the present invention after the active layer outside the second mask pattern is removed; Figure 6 A schematic diagram of the structure of the grating region layer and the phase region material obtained by the butt-jointed growth technique provided by the present invention; Figure 7 This is a schematic diagram of the structure after the grating, cladding and electrical contact layer are manufactured according to the present invention; Figure 8 A side view of the completed laser provided by the present invention; Figure 9 A schematic cross-sectional view of the completed laser provided by the present invention; In the figure, 1-first modulation zone, 2-first front grating zone, 3-first gain zone, 4-first phase zone, 5-back grating zone, 6-second phase zone, 7-second gain zone, 8-second grating zone, 9-second modulation zone 9, 11-substrate, 12-first mask pattern, 13-lower confinement layer, 14-multi-quantum well layer, 15-upper confinement layer, 16-second mask pattern, 17-passive layer, 18-grating, 19-cladding, 20-electrical contact layer, 21-electrical isolation groove, 22-P-side electrode, 23-N-side electrode. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0020] Example 1 See Figure 1 , Figure 1 A schematic flow chart of a method for preparing a novel electro-absorption modulated laser provided in this embodiment is shown, and the method includes: Step S101: Surface layout of the substrate is performed, and the substrate surface is divided into a first modulation region, a first front grating region, a first gain region, a first phase region, a back grating region, a second phase region, a second gain region, a second grating region, and a second modulation region in sequence along the length direction; wherein the first and second front grating regions, the first and second gain regions, the first and second modulation regions, and the first and second phase regions are arranged symmetrically with respect to the longitudinal axis of the substrate center; Step S102: forming first mask patterns on the surfaces of the first and second gain regions of the substrate, respectively. The first mask patterns are two stripe patterns with the same length as the first and second gain regions and a preset spacing and width. Step S103: growing an active layer on the substrate surface except for the first mask pattern, and then etching away the first mask pattern; Step S104: forming a second mask pattern located in the first and second gain regions and the first and second modulation regions on the surface of the active layer, and removing the active layer outside the second mask pattern by etching technology; Step S105: using a butt-joint growth technique to complete the passive material growth of the rear grating region, the first and second front grating regions, the first and second phase regions, and the substrate portion after the first mask pattern is removed; Step S106: fabricating sampled gratings in the first front grating region, the rear grating region, and the second front grating region by electron beam direct writing technology; Step S107: sequentially growing a cladding layer and an electrical contact layer on the entire surface area, and forming an inverted shallow ridge waveguide structure on the cladding layer and the electrical contact layer; Step S108: etching electrical isolation trenches on the electrical contact layer to achieve electrical isolation between the regions; Step S109: fabricating a P-side electrode on the electrical contact layer in each region, and fabricating an N-side electrode on the entire surface of the bottom of the substrate after thinning the substrate, thereby completing the fabrication of the laser.

[0021] The laser fabrication method provided in this embodiment forms the gain region and the modulation region simultaneously in a single epitaxial growth process by creating a mask pattern on the surface of the gain region and performing selective epitaxial growth. This avoids the complex process of two epitaxy processes required for the gain region and the modulation region in traditional solutions, thus reducing the use time of the fabrication equipment and the number of wafer transfers. The growth position of the gain region is defined by the initial mask, and the concentration gradient of the vapor precursor at the SAG edge is utilized to achieve a gradual change in the quantum well composition of the gain region, inducing a red shift in the bandgap width. The redshifted gain region improves the carrier confinement capability, reduces the threshold current, and simplifies the energy band engineering design. A design in which the passive layer bandgap is smaller than the gain region bandgap forms a photon barrier and reduces carrier leakage. The functional region is designed with a centrally symmetrical layout, combined with a shared reflective cavity in the rear grating region, to achieve dual-end light output. Furthermore, symmetrical current injection offsets thermal drift, improving the stability of wavelength tuning. This method significantly reduces the power consumption and manufacturing cost of the integrated chip, providing a low-cost solution for wavelength-tunable electro-absorption modulated lasers.

[0022] The following combination Figure 2-Figure 9 The above steps are shown and explained in detail.

[0023] As a specific embodiment, the steps of the production method include: (1) Select an N-type indium phosphide substrate 11, such as Figure 2 As shown, the surface of the substrate 11 is divided into a first modulation region 1, a first front grating region 2, a first gain region 3, a first phase region 4, a back grating region 5, a second phase region 6, a second gain region 7, a second grating region 8, and a second modulation region 9 along the longitudinal direction. The first and second front grating regions, the first and second gain regions, the first and second modulation regions, and the first and second phase regions are arranged symmetrically about the longitudinal axis of the substrate center. The lengths of the first modulation region 1 and the second modulation region 9 are 150 microns, the length of the back grating region 5 is 500 microns, the lengths of the first gain region 3 and the second gain region 7 are 300 microns, the lengths of the first phase region 4 and the second phase region 6 are 100 microns, and the lengths of the first front grating region 2 and the second front grating region 8 are 50 microns.

[0024] (2) 150 nm of silicon dioxide is grown on the surface of the substrate 11 by PECVD equipment, and a first mask pattern 12 for selective epitaxy of the first gain region 3 and the second gain region 7 is produced by photolithography and wet etching. The first mask pattern 12 for selective epitaxy is two strip patterns with the same length as the first gain region 3 and the second gain region 7 (the actual length is set to 300 μm), a width of 12 μm, and a spacing of 20 μm, as shown in FIG. Figure 3 As shown, Figure 3 A top view of the substrate surface.

[0025] (3) An InGaAlAs active layer is grown on the surface of the substrate 11 in sequence. The active layer includes a lower confinement layer 13, a multi-quantum well layer 14, and an upper confinement layer 15. The fluorescence wavelength of the active region is 1545 nm. The thickness of the lower confinement layer 13 is 100 nm. The multi-quantum well layer 14 is formed by six 5 nm thick quantum well layers and seven 10 nm thick barrier layers grown crosswise. The thickness of the upper confinement layer 15 is 100 nm. Figure 4 As shown, Figure 4 A side view of the laser.

[0026] (4) Etch away the first mask pattern 12 of the selective epitaxy, grow 150nm of silicon dioxide on the upper confinement layer 15 again using PECVD equipment, and then use photolithography and wet etching to produce the second mask pattern 16 located in the first gain region 3, the second gain region 7 and the first modulation region 1, the second modulation region 9. In practice, the width of the second mask pattern 16 is 20 microns. Figure 5 As shown, Figure 5 A side view of the laser after the second mask pattern 16 is completed is shown.

[0027] (5) The active layer outside the second mask pattern 16 is removed by ICP dry etching technology, and the passive layer 17 of the rear grating region 5, the first front grating region 2, the second front grating region 8, the first phase region 4, and the second phase region 6 is obtained by butt-joint growth technology. The material of the passive layer 17 is InGaAsP, as shown in FIG. Figure 6 As shown, the fluorescence wavelength of the passive layer is 1450 nm.

[0028] (6) The silicon dioxide material of the second mask pattern 16 is removed by etching with hydrofluoric acid, and a sampling grating 18 is produced in the first front grating region 2, the rear grating region 5 and the second front grating region 8 by electron beam direct writing technology, as shown in FIG. Figure 7 shown.

[0029] (7) A cladding layer 19 with a thickness of 1.5 μm and an electrical contact layer 20 with a thickness of 300 nm are grown on the surface of the entire laser, and a 3 μm wide inverted shallow ridge waveguide structure is fabricated on the cladding layer 19 and the electrical contact layer 20, as shown in FIG. Figure 8 As shown, an electrical isolation groove 21 is etched on the electrical contact layer 20. The depth of the electrical isolation groove 21 is 300 nm and the width is 50 microns. The electrical isolation groove 21 is used to achieve electrical isolation between the various areas of the laser. (8) A P-side electrode 22 (comprising a 50 nm thick titanium thin layer and a 300 nm thick gold thin film) is fabricated on the electrical contact layer 20 of the first modulation region 1, the second modulation region 9, the back grating region 5, the first gain region 3, the second gain region 7, the first phase region 4, the second phase region 6, the first front grating region 2, and the second front grating region 8. The thickness of the substrate 11 is reduced to 110 μm. Then, an N-side electrode 23 (comprising a 50 nm thick titanium thin layer and a 300 nm thick gold thin film) is fabricated on the bottom of the entire die to complete the fabrication of the laser. Figure 9 As shown, Figure 9 A cross-sectional view of the completed laser chip is shown.

[0030] The method of this embodiment has three core advantages: First, selective area epitaxy technology enables single-pass epitaxial homogeneous growth of the gain and modulation regions, significantly reducing manufacturing costs. This allows material to be deposited between masks, achieving a redshift in the PLmapping spectrum, reducing the laser bandgap and shifting the wavelength of absorbed light to a longer wavelength. Second, the coordinated design of the passive layer and gain region bandgap creates efficient photon confinement, supporting wide-range continuous wavelength tuning. Third, the symmetrical functional area layout combined with the inverted ridge waveguide structure simplifies the process while improving optoelectronic isolation performance and energy efficiency. This method provides a high-bandwidth, low-cost photonic integration solution for the fields of optical communications and artificial intelligence.

[0031] Example 2 The embodiment of the present invention further provides a structure of a novel electro-absorption modulated laser, which is manufactured using the method for preparing the novel electro-absorption modulated laser described in Example 1. Figure 8 As shown, the laser comprises, from bottom to top, an N-side electrode 23, a substrate 11, an active layer (including a lower confinement layer 13, a multi-quantum well layer 14 and an upper confinement layer 15), a cladding layer 19, an electrical contact layer 20 and a P-side electrode 22; The laser is divided into a first modulation area 1, a first front grating area 2, a first gain area 3, a first phase area 4, a rear grating area 5, a second phase area 6, a second gain area 7, a second grating area 8 and a second modulation area 9 in sequence along the length direction starting from one side; Among them, the first\second front grating region, the first\second gain region, the first\second modulation region and the first\second phase region are symmetrically arranged with the longitudinal center of the substrate 11 as the axis; the first front grating region 2, the back grating region 5 and the second front grating region 8 are made with sampled gratings; the cladding 19 and the electrical contact layer 20 have an inverted shallow ridge waveguide structure, and the electrical contact layer 20 is etched with an electrical isolation groove 21 to achieve electrical isolation between the regions.

[0032] Figure 9 The cross-sectional view of the laser structure is shown. The wavelength tuning range of the laser is greater than 30nm and can be continuously tuned.

[0033] The laser structure provided in this embodiment divides the laser area into multiple different functional areas along the length direction and sets up the two ends symmetrically in the longitudinal direction with the substrate as the center, so as to ensure that the performance of each functional area is optimized independently. Through the precise design and optimization of the gain area, modulation area and other intervals, the optical performance and modulation efficiency of the laser can be greatly improved to meet the requirements of high power, low noise and strong stability. Sampled gratings are made on the first front grating area, the rear grating area and the second front grating area, so that the optical feedback and mode control of the laser are more precise. The design of the sampled grating can improve the wavelength selectivity and mode selectivity of the laser, ensure the stability of the optical performance, and thus improve the output quality of the laser. By etching an electrical isolation groove on the electrical contact layer, electrical isolation between the functional areas can be achieved, avoiding current interference between different functional areas. The electrical isolation design ensures the independent operation of different areas, improves the overall electrical efficiency and reliability of the laser, and reduces the impact of thermal effects on performance. The inverted shallow ridge waveguide structure is arranged on the cladding and the electrical contact layer, which helps to improve the optical guide efficiency of the laser. This structure optimizes the light propagation path, reduces losses, improves the quality and propagation efficiency of the light beam, and further enhances the overall performance of the laser.

[0034] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a novel electroabsorption modulated laser, characterized in that: include: Performing a surface layout on the substrate, dividing the substrate surface into a first modulation region, a first front grating region, a first gain region, a first phase region, a back grating region, a second phase region, a second gain region, a second grating region, and a second modulation region in sequence along the length direction; wherein the first and second front grating regions, the first and second gain regions, the first and second modulation regions, and the first and second phase regions are arranged symmetrically with respect to the longitudinal axis of the substrate center; A first mask pattern is formed on the surface of the first and second gain regions of the substrate, wherein the first mask pattern is two stripe patterns with the same length as the first and second gain regions and a preset spacing and width; growing an active layer on a portion of the substrate surface excluding the first mask pattern, and then etching away the first mask pattern; Making a second mask pattern located in the first and second gain regions and the first and second modulation regions on the surface of the active layer, and removing the active layer outside the second mask pattern by etching technology; The passive material growth of the rear grating region, the first and second front grating regions, the first and second phase regions, and the substrate portion after the first mask pattern is removed is completed by using a butt-joint growth technique; The sampled gratings are fabricated in the first front grating region, the rear grating region and the second front grating region by electron beam direct writing technology; A cladding layer and an electric contact layer are sequentially grown on the entire surface area, and an inverted shallow ridge waveguide structure is fabricated on the cladding layer and the electric contact layer; Etching electrical isolation trenches on the electrical contact layer to achieve electrical isolation between the regions; A P-side electrode is fabricated on the electrical contact layer of each region, and an N-side electrode is fabricated on the entire surface of the bottom of the substrate after the substrate is thinned, completing the laser fabrication.

2. The method for preparing a novel electroabsorption modulated laser according to claim 1, characterized in that: The substrate material is N-type indium phosphide.

3. The method for preparing a novel electro-absorption modulated laser according to claim 1, characterized in that: The second mask pattern is removed by using ICP dry etching technology.

4. The method for preparing a novel electroabsorption modulated laser according to claim 1, characterized in that: The length of the first\second modulation zone is 150 microns, the length of the first\second gain zone is 300 microns, the length of the first\second phase zone is 100 microns, the length of the first\second grating zone is 50 microns, and the length of the rear grating zone is 500 microns.

5. The method for preparing a novel electro-absorption modulated laser according to claim 1, characterized in that: The passive material is InGaAsP, and its light fluorescence wavelength is 1450nm.

6. The method for preparing a novel electro-absorption modulated laser according to claim 1, characterized in that: The active layer is an InGaAlAs active layer, and its light fluorescence wavelength is 1545nm; the active layer comprises a lower confinement layer, a multi-quantum well layer and an upper confinement layer in order from bottom to top.

7. The method for preparing a novel electro-absorption modulated laser according to claim 6, characterized in that: The multi-quantum well layer is formed by cross-growth of multiple quantum well layers and multiple barrier layers.

8. The method for preparing a novel electro-absorption modulated laser according to claim 1, characterized in that: The thickness of the substrate after thinning is 110 microns.

9. The method for preparing a novel electro-absorption modulated laser according to claim 1, characterized in that: The thickness of the cladding layer is 1.5 microns, the thickness of the electric contact layer is 300 nm, and the width of the inverted shallow ridge waveguide structure is 3 microns.

10. A novel structure of an electro-absorption modulated laser, characterized in that: The laser is manufactured by the manufacturing method according to any one of claims 1 to 9, and the laser comprises, from bottom to top, an N-side electrode, a substrate, an active layer, a cladding layer, an electrical contact layer, and a P-side electrode; The laser is divided into a first modulation area, a first front grating area, a first gain area, a first phase area, a back grating area, a second phase area, a second gain area, a second grating area and a second modulation area in sequence along the length direction starting from one side; Among them, the first\second front grating region, the first\second gain region, the first\second modulation region and the first\second phase region are symmetrically arranged with the longitudinal axis of the center of the substrate as the axis; the first front grating region, the back grating region and the second front grating region are made with sampled gratings; the cladding and the electrical contact layer have an inverted shallow ridge waveguide structure, and the electrical contact layer is etched with an electrical isolation groove to achieve electrical isolation between the regions.

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