Selectively grown high-speed electro-absorption modulated laser chip
By selectively growing an electroabsorption modulated laser chip, the LD and EAM regions are separated by a mask layer with a pre-defined shape and an isolation region is set. This solves the problems of high cost and interface defects caused by multiple epitaxial growths, and realizes a high-performance, low-cost laser chip.
Patent Information
- Application Number
- CN202520319699.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2026-01-13
- Estimated Expiration
- 2035-02-26
AI Technical Summary
Existing technologies for fabricating electroabsorption modulated lasers suffer from high costs and interface defects due to multiple epitaxial growth processes, which affect the reliability and performance of the chip.
A selective growth process is employed, in which a buffer layer, an EAM active region, and a grating layer are selectively grown by setting a preset shape of a mask layer on the substrate. This separates the LD and EAM regions and sets an isolation region at the junction, avoiding multiple epitaxial growths and optimizing the number of epitaxial growth cycles.
A high-performance, low-cost electroabsorption modulated laser chip was developed, improving material quality, avoiding interface defects, and enhancing chip reliability.
Smart Images
Figure CN223797726U_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical communication technology, and in particular to a selectively grown high-speed electroabsorption modulation laser chip. Background Technology
[0002] Electro-absorption modulated lasers (EMLs) are integrated devices combining electro-absorption modulators (EAMs) and DFB lasers (LDs). They are small, low-chill, high-performance optical communication light sources, integrating an EAM that operates using the quantum confinement Stark effect (QCSE) and a DFB laser that uses internal grating coupling to determine the wavelength. They are currently the ideal light source for information transmission in high-speed fiber optic transmission networks both domestically and internationally. They have numerous applications in access networks, such as serving as signal light sources for fiber optic transmission in metropolitan area networks (MANs) and local area networks (LANs), and as light sources for electro-optic signal conversion and long-distance transmission in phased array radar base stations.
[0003] Compared to directly modulated lasers (DMLs), EMLs offer superior transmission characteristics and performance, especially in high-frequency modulation or long-distance transmission. Current solutions for integrating LDs and EAMs include: identical layer schemes and butt-joint growth.
[0004] The identical layer EML laser method grows both the laser light extraction (LD) and the laser light emission (EAM) structure in a single epitaxial growth process. By adjusting the wavelength detuning of the LD, the absorption of the EAM can be made to meet application requirements. However, it cannot optimize the LD and EAM structures separately, and cannot simultaneously achieve the same light extraction efficiency of the LD and the extinction ratio (ER) of the EAM. Another approach, butt-joint growth, involves designing the LD and EAM structures separately. First, the LD structure is grown on the substrate. Then, a mask protecting the LD region is created using photolithography. After dry and wet etching, the LD structure outside the mask is removed. This is followed by multiple epitaxial growths to grow the EAM structure and other structures. The disadvantages are the need for multiple epitaxial growths and the susceptibility of defects at the growth interface, leading to performance degradation or reliability issues. Utility Model Content
[0005] This invention proposes a selectively grown high-speed electroabsorption modulated laser chip that eliminates the need for multiple epitaxial growth processes, effectively reducing costs. Furthermore, the absence of a docking interface significantly improves material quality, avoids interface defects, and enhances chip reliability.
[0006] The present invention adopts the following technical solution.
[0007] A selectively grown high-speed electro-absorption modulated laser chip, the chip comprising a substrate, and further comprising a buffer layer, an EAM active region, and a grating layer whose growth thickness is adjusted according to a preset shape of a mask layer on the substrate during the selective growth process; the active region of the chip is divided into an LD region on one side for generating laser light and an EAM region on the other side for modulating laser light according to the preset shape of the mask layer on the substrate before the selective growth process; the LD region includes a grating layer and a grating at the grating layer, the grating layer being sequentially covered with an upper cladding layer, a contact layer, and a first metal electrode, an isolation region being provided at the junction of the LD region and the EAM region, and a second metal electrode being provided at the bottom surface of the substrate.
[0008] The adjacent regions of the EAM and LD grating layers are filled with InP.
[0009] No raster layer is set in the EAM area.
[0010] The substrate is an InP substrate.
[0011] The preset shape of the mask layer is a pre-defined mask pattern, which consists of two symmetrical trapezoids; the mask layer is a SiO2 mask layer.
[0012] The first metal electrode is a P-plane metal electrode.
[0013] The contact layer is an InGaAs contact layer that forms an ohmic contact with the P-side metal electrode.
[0014] The second metal electrode is an N-face metal electrode.
[0015] The isolation zone is located at the junction of the LD region and the EA region to prevent current conduction and mutual interference between the LD region and the EA region.
[0016] The grating layer is a holographic grating with a period of 245.61 nm and a duty cycle of 50%.
[0017] This invention enables selective growth of different functional layers and integration of multiple functions on the same substrate. It eliminates the need for multiple epitaxial growth processes, effectively reducing costs; furthermore, the absence of interface connections significantly improves material quality, avoids interface defects, and enhances chip reliability.
[0018] This invention utilizes a selective growth process to obtain LDs and EAMs with different structures by setting specific mask patterns, while optimizing the number of epitaxial growth cycles, thus enabling the fabrication of high-performance, low-cost high-speed electroabsorption modulated lasers. Attached Figure Description
[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:
[0020] Appendix Figure 1 This is a schematic diagram of the chip for the high-speed electroabsorption modulated laser of this utility model;
[0021] Appendix Figure 2 This is a schematic diagram after completing step two of the embodiment;
[0022] Appendix Figure 3 This is a schematic diagram of the mask pattern in step two of the embodiment;
[0023] Appendix Figure 4 This is a schematic diagram after completing step three of the embodiment;
[0024] Appendix Figure 5 This is a schematic diagram after completing step four of the embodiment;
[0025] Appendix Figure 6 This is a schematic diagram of step five in the embodiment after the isolation area has been formed;
[0026] In the figure: 1-LD region; 2-EAM region; 3-grating; 4-contact layer; 5-upper cladding layer; 6-first metal electrode; 7-grating layer; 8-EAM active region; 9-buffer layer; 10-substrate; 11-second metal electrode; 12-isolation region. Detailed Implementation
[0027] As shown in the figure, a selectively grown high-speed electro-absorption modulated laser chip can be used to selectively grow high-speed electro-absorption modulated lasers. The chip includes a substrate 10, and also includes a buffer layer 9, an EAM active region 8, and a grating layer whose growth thickness is adjusted according to the preset shape of the mask layer on the substrate during the selective growth process. The active region of the chip is divided into an LD region 1 on one side for generating laser and an EAM region 2 on the other side for modulating laser according to the preset shape of the mask layer on the substrate before the selective growth process. The LD region includes a grating layer 7 and a grating 3 on the grating layer. An upper cladding layer 5, a contact layer 4, and a first metal electrode 6 are sequentially coated on the grating layer. An isolation region 12 is provided at the junction of the LD region and the EAM region, and a second metal electrode 11 is provided at the bottom surface of the substrate.
[0028] The adjacent regions of the EAM and LD grating layers are filled with InP.
[0029] No raster layer is set in the EAM area.
[0030] The substrate is an InP substrate.
[0031] The preset shape of the mask layer is a pre-defined mask pattern, which consists of two symmetrical trapezoids; the mask layer is a SiO2 mask layer.
[0032] The first metal electrode is a P-plane metal electrode.
[0033] The contact layer is an InGaAs contact layer that forms an ohmic contact with the P-side metal electrode.
[0034] The second metal electrode is an N-face metal electrode.
[0035] The isolation zone is located at the junction of the LD region and the EA region to prevent current conduction and mutual interference between the LD region and the EA region.
[0036] The grating layer is a holographic grating with a period of 245.61 nm and a duty cycle of 50%.
[0037] Example:
[0038] A method for fabricating a selectively grown high-speed electroabsorption modulated laser chip, the method comprising the following steps;
[0039] Step 1: A SiO2 mask is grown on an InP substrate using PECVD. A specific mask pattern is fabricated through spin coating, exposure, development, and etching. The mask pattern consists of two symmetrical trapezoids.
[0040] The upper base L1 of the trapezoid is 462.5 μm long, the lower base L2 is 637.5 μm long, the height Wm is 87.5 μm, and the distance between the two trapezoids Wg is 30 μm.
[0041] Step 2: On the wafer from Step 1, a buffer layer, an EAM active region, and a grating layer are grown by MOCVD. After growth, the wafer is cleaned with BOE solution, and the SiO2 mask grown in Step 1 is removed.
[0042] Step 3: Fabricate a grating on the wafer from Step 2. Obtain a photoresist mask through holographic exposure, and then etch it with HCl solution to obtain a holographic grating with a period of 245.61nm and a duty cycle of 50%. After the grating is fabricated, continue with spin coating, photolithography, and development to form a photoresist mask in the LD region. Etch the grating in the EAM region with HCl solution. After all etching is completed, remove the photoresist.
[0043] Step 4: After completing Step 3, use BOE solution to remove the oxide on the surface of the wafer, and then place it into the MOCVD equipment to grow a highly doped InP layer and an InGaAs contact layer.
[0044] Step 5: After completing the above steps, the chip fabrication begins. A SiO2 mask is grown using PECVD. The SiO2 mask pattern is fabricated through spin coating, exposure, development, and etching. Then, the ridge waveguide is formed by etching with a solution containing Br2 and HCl:H3PO4. Isolation is then performed in the docking region of LD and EA to prevent the current conduction in the LD and EA regions from interfering with each other. After that, a P-side electrode layer is fabricated to form an ohmic contact with the InGaAs contact layer. The back side of the substrate is then thinned by grinding, with the final thickness remaining at 110±10um.
[0045] An N-sided electrode layer is deposited on the back side. Then, the wafer is cut into bars, optical coatings are applied to both ends of the bars, and finally, the bars are separated into individual chips to complete all processes.
[0046] Example:
[0047] To obtain high-performance, low-cost high-speed electro-absorption modulated lasers, it is necessary to obtain LDs and EAMs with different structures and optimize the epitaxial growth cycle. Therefore, in this example, a selectively grown high-speed electro-absorption modulated laser and its fabrication method are adopted. The detailed technical solution is as follows:
[0048] In this example, the selectively grown high-speed electro-absorption modulated laser includes a substrate, a mask layer on the substrate, a buffer layer, active regions of LD and EAM, a grating layer in the LD region, an EAM region without a grating layer filled with InP, a cladding layer covering the grating layer, a contact layer, a P-side metal electrode, an isolation region at the junction of LD and EAM, and an N-side metal electrode at the bottom of the substrate.
[0049] The preparation method includes the following steps:
[0050] Step 1: A SiO2 mask is grown on an InP substrate by PECVD. A specific mask pattern is fabricated by spin coating, exposure, development and etching. The mask pattern consists of two symmetrical trapezoids with an upper base L1 of 462.5 μm, a lower base L2 of 637.5 μm, a height Wm of 87.5 μm, and a spacing Wg of 30 μm between the two trapezoids.
[0051] Step 2: On the wafer that has completed Step 1, grow the buffer layer, EAM active region and grating layer by MOCVD. After growth, clean with BOE solution and remove the SiO2 mask grown in Step 1.
[0052] Step 3: Fabricate the grating on the wafer from Step 2. Obtain a photoresist mask through holographic exposure, and then etch it using HCl solution until a holographic grating with a period of 245.61nm and a duty cycle of 50% is formed. After the grating is fabricated, continue with spin coating, photolithography, and development to form a photoresist mask in the LD region. Etch the grating in the EAM region using HCl solution. After all etching is completed, remove the photoresist.
[0053] Step 4: After completing Step 3, use BOE to remove the surface oxide, and then place it into the MOCVD equipment to grow a highly doped InP layer and an InGaAs contact layer.
[0054] Step 5: After completing the above steps, chip fabrication begins. A SiO2 mask is grown using PECVD. The SiO2 mask pattern is fabricated through spin coating, exposure, development, and etching. Then, the ridge waveguide is etched using a solution containing Br2 and HCl:H3PO4. Isolation is then applied to the docking area between the LD and EA to prevent the current conduction in the LD and EA areas from interfering with each other. Next, a P-side electrode layer is fabricated to form an ohmic contact with the InGaAs contact layer. The back side of the substrate is then thinned by grinding, with the final thickness remaining at 110±10um. An N-side electrode layer is deposited on the back side. The wafer is then cut into bars, and optical coatings are applied to both ends of the bars. Finally, the bars are separated into individual chips, completing all processes.
Claims
1. A selectively grown high-speed electroabsorption modulator laser chip, characterized by: The chip comprises a substrate, a buffer layer, an EAM active region and a grating layer, the growth thickness of the buffer layer being adjusted according to a preset shape of a mask layer on the substrate during a selective growth process; the active region of the chip is divided into an LD region for generating laser and an EAM region for modulating laser according to the preset shape of the mask layer on the substrate before the selective growth process; the LD region comprises the grating layer and a grating at the grating layer, and the grating layer sequentially has an upper cladding layer, a contact layer and a first metal electrode; a second metal electrode is arranged at the bottom surface of the substrate.
2. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The same layer region adjacent to the grating layer of the LD region in the EAM region is an InP-filled region.
3. The selectively grown high-speed electroabsorption modulator laser chip of claim 2, wherein: The EAM region is not provided with the grating layer.
4. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The substrate is an InP substrate.
5. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The preset shape of the mask layer is a preset mask pattern, and the mask pattern is two symmetrical trapezoids; the mask layer is a SiO2 mask layer.
6. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The first metal electrode is a P-face metal electrode.
7. The selectively grown high-speed electroabsorption modulator laser chip of claim 6, wherein: The contact layer is an InGaAs contact layer forming ohmic contact with the P-face metal electrode.
8. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The second metal electrode is an N-face metal electrode.
9. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The isolation region is arranged at the abutting position of the LD region and the EA region, and is used for preventing current conduction and mutual influence of the LD region and the EA region.
10. The selectively grown high-speed electroabsorption modulator laser chip of claim 1, wherein: The grating layer is a holographic grating.