A ridge waveguide single-mode semiconductor laser with a spatial modulation structure and a preparation method thereof
By introducing spatial modulation structures and silicon dioxide-filled holes into semiconductor lasers, the damage problem of ridge waveguides during packaging is solved, improving the reliability and heat dissipation performance of the laser and achieving high-efficiency and high-beam-quality laser output.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Shandong Huaguang Optoelectronics Co. Ltd.
- Filing Date
- 2023-10-13
- Publication Date
- 2026-08-04
AI Technical Summary
The ridge waveguide structure of existing semiconductor lasers is easily damaged during the packaging process, affecting reliability. Furthermore, the choice of materials in high-temperature environments limits their high-power applications, resulting in low efficiency and poor beam quality.
The structure employs a spatial modulation method, which creates an effective refractive index difference by setting holes in the P-confinement layer and filling them with silicon dioxide material, thereby achieving refractive index guidance. At the same time, the P-side is flat, which reduces pressure damage during the packaging process and improves heat dissipation.
It improves the yield and lifespan of lasers, enhances heat dissipation performance, solves the damage problem during the packaging process, and maintains high efficiency and beam quality in high-temperature environments.
Smart Images
Figure CN117317806B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a ridge waveguide single-mode semiconductor laser with a spatial modulation structure and its fabrication method, belonging to the field of semiconductor laser technology. Background Technology
[0002] Semiconductor lasers are widely used in optical storage, laser displays, industrial applications, and medical devices. Red-band semiconductor lasers, with their excellent photoelectric conversion efficiency, are widely used in laser pointers, sensing devices, and medical instruments.
[0003] Currently, the main structure of semiconductor lasers is formed by etching raised ridge waveguides to guide the refractive index. However, the chip structure achieved by isolating the ridge waveguide from the air inevitably has height differences. In addition, in order to improve the heat dissipation of the chip, the ridge waveguide is generally packaged downwards, and the ridge waveguide is soldered to the heat sink. There is a certain downward pressure when they come into contact, which can easily damage the ridge waveguide and affect the reliability of the laser.
[0004] To address the above issues, there are two main solutions: The first involves gain guidance, without a ridge waveguide, but by controlling the current injection region, forcing current into a specific area of the laser to form a gain region. Areas without current injection naturally lose light and cannot oscillate. However, gain guidance cannot solve the problem of natural current diffusion and cannot form the strong confinement structure of ridge waveguide refractive index guidance, resulting in an excessively high chip threshold and low efficiency. Currently, this method is mostly used in high-power wide-strip lasers and is rarely reported in lasers with high beam quality and efficiency requirements. The second method involves filling the raised ridge waveguide and the air groove next to it with material to form refractive index guidance. Simultaneously, low-refractive-index material is filled inside to form a planar surface on the laser's P-side, evenly distributing the pressure under the patch and reducing ridge waveguide damage. While this method can form a strong light field confinement through refractive index guidance, the choice of materials limits the high-temperature and high-power applications of the laser. The ridge waveguide generates significant heat during laser operation, and the stability of conventional insulating low-refractive-index materials at high temperatures cannot meet the requirements for long-term laser operation. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides a ridge waveguide single-mode semiconductor laser with a spatial modulation structure. The laser does not require a raised ridge waveguide; instead, a spatial modulation structure is placed at the laser's edge, resulting in a higher effective refractive index in the central region compared to the sides, achieving the same refractive index guiding effect as a ridge waveguide. Simultaneously, the entire P-plane of the laser is planar, which can evenly distribute the pressure on the ridge waveguide during flip-chip mounting, reducing its impact. The structure of this invention is simple to fabricate, improves the efficiency of the laser's post-packaging process, and enables full contact between the solder and the laser surface, enhancing heat dissipation and increasing laser lifespan.
[0006] Meanwhile, the present invention also provides a method for fabricating a ridge waveguide single-mode semiconductor laser with a spatial modulation structure.
[0007] The technical solution of the present invention is as follows:
[0008] A ridge waveguide single-mode semiconductor laser with a spatial modulation structure includes, from bottom to top, an N-plane metal, a substrate, an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, a P-confinement layer, and a P-plane metal;
[0009] There is no spatial modulation structure in the middle region of the chip, and the middle region of the P-confining layer is covered with an ohmic contact layer (there is no ohmic contact layer in other positions). A spatial modulation structure is provided on the P-confining layer except for the middle region. The spatial modulation structure includes a number of holes that gradually increase from the middle to the edge, so that the effective refractive index of the spatial modulation structure changes from strong to weak from the middle to the edge, forming a waveguide region in the middle region.
[0010] An insulating layer covers the P-confining layer except for the middle region. The insulating layer also penetrates the inner wall of the hole of the spatial modulation structure to form a thin insulating layer, thereby achieving the insulating effect. The filling depth of the insulating layer material reaches the P-confining layer.
[0011] The ohmic contact layer and the top of the insulating layer are flush, and the P-side metal is covered on top of them. The insulating layer and the ohmic contact layer are covered by the P-side metal, and the P-side metal and the ohmic contact layer are in contact, so that current is injected only into the ohmic contact layer. In other locations, the P-side metal is below the insulating layer, which is isolated from the P-limiting layer.
[0012] The spatial modulation structure makes the P-side flat, reducing damage to the waveguide during subsequent packaging and improving yield. The raised ridge waveguide experiences downward pressure during packaging when in contact with the heat sink, which can easily damage it and affect laser reliability. The spatial modulation structure increases the contact area of the P-side, not only dispersing the downward pressure generated during contact and protecting the ridge waveguide, but also providing better heat dissipation due to the high thermal conductivity of silicon dioxide (1.4 W / m·℃), significantly higher than air, thus improving device stability.
[0013] Preferably, the middle region is within a width range of 5-8μm from the center of the chip, and more preferably within a width range of 5μm.
[0014] The P-confining layer of this invention contains holes with different duty cycles and diameters, forming a spatial modulation structure. Symmetrical to the chip's center, there is no spatial modulation structure within a 5μm width region in the middle, with the number of holes gradually increasing towards the edges. The distribution of the number of holes is zero in the chip's central region and gradually increases towards the edges. Utilizing the spatial modulation of the refractive index of the confinement layer by these holes creates a refractive index guiding effect similar to a ridge waveguide.
[0015] Preferably, the insulating layer material is silicon dioxide, and the pores are filled with silicon dioxide material that has good heat dissipation, forming an effective refractive index difference and forming a waveguide region in the middle area.
[0016] Preferably, the spatial modulation structure is symmetrical about the chip center, with no holes in the middle area. The holes in the spatial modulation structure have the same diameter or gradually decrease in diameter from the middle to the edge. Regardless of the hole arrangement, the goal is to ensure that the effective refractive index of the spatial modulation structure changes from strong to weak.
[0017] Preferably, the substrate is a GaAs substrate.
[0018] Spatial modulation structures need to achieve refractive index guidance. Silica has a refractive index of 1.44, which allows the effective refractive index of the middle region to be higher than that of the sides. The material on both sides of the raised ridge waveguide can be considered as air, and air has a refractive index of 1. Therefore, lasers with spatial modulation structures can use the filled silica material to achieve the refractive index confinement of the ridge waveguide, thereby controlling carrier diffusion and solving problems such as high threshold, low efficiency, and poor beam quality in all P-surface contact packaged chip structures.
[0019] A method for fabricating the above-mentioned ridge waveguide single-mode semiconductor laser with spatial modulation structure includes the following steps:
[0020] (1) An N-confinement layer, an N-waveguide layer, a quantum hydrazine active layer, a P-waveguide layer, a P-confinement layer and an ohmic contact layer were sequentially grown on the substrate using the MOCVD method.
[0021] (2) After photolithography and development, a spatial control structure, i.e., a specific arrangement of holes, is prepared in the middle region using etching technology, with a depth reaching the P-confinement layer;
[0022] The spatial control structure erodes into the P-confining layer, but the structure does not interfere with the P-waveguide layer below the P-confining layer, thus minimizing the impact of structural changes on optical field transmission.
[0023] (3) After photolithography and development, silicon dioxide is grown at the spatial control structure position using PECVD technology. It can be used as a filling material for holes without affecting its use as an insulating layer.
[0024] (4) Remove the insulating layer on the ohmic contact layer in the middle area by photolithography, etching or stripping to leave a contact area for the next step of P-side ohmic contact;
[0025] (7) Prepare P-side metal by vapor deposition or other methods;
[0026] (8) After substrate thinning, preparation of N-side metal, alloying, and cleavage, a semiconductor laser chip is finally formed.
[0027] For any details not covered in this invention, please refer to the prior art.
[0028] The beneficial effects of this invention are as follows:
[0029] The spatial control structure designed in this invention forms an effective refractive index difference through a simple hole structure, achieving the ridge waveguide confinement effect. The process is simple and easy to manufacture, reducing laser loss and lowering the manufacturing difficulty, while maintaining a high device yield and laser performance parameters.
[0030] The spatial modulation structure of this invention, by adding holes filled with silicon dioxide on both sides of the P-confining layer, not only achieves an effective refractive index difference and prepares a ridge waveguide structure without protrusions, but also reduces the dispersion of downward pressure during the packaging process by the flat P-surface, thus reducing damage to the protruding ridge waveguide. This ridge-free waveguide not only effectively solves the problem of device packaging damage, but also does not affect the threshold current, light output quality and other characteristic parameters of the laser. Attached Figure Description
[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.
[0032] Figure 1 A schematic diagram of a ridge waveguide single-mode semiconductor laser with a spatial modulation structure, in which the P-side metal layer, insulating layer, and N-side metal layer have been removed.
[0033] Figure 2 A schematic diagram of a ridge waveguide single-mode semiconductor laser with a spatial modulation structure, in which the P-plane and N-plane metal layers have been removed.
[0034] Figure 3 Top view of a ridge waveguide single-mode semiconductor laser with spatial modulation structure, in which the P-plane metal layer and insulating layer have been removed;
[0035] Figure 4 Top view of a ridge waveguide single-mode semiconductor laser with a spatial modulation structure, in which the P-plane metal layer has been removed;
[0036] In the figure, 1 is the GaAs substrate, 2 is the N-confinement layer, 3 is the N-waveguide layer, 4 is the quantum well active layer, 5 is the P-waveguide layer, 6 is the P-confinement layer, 7 is the ohmic contact layer, 8 is the P-plane metal layer, 9 is the N-plane metal layer, 10 is the spatial modulation structure, 11 is the waveguide region, and 12 is the insulating layer. Detailed Implementation
[0037] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.
[0038] Example 1
[0039] A ridge waveguide single-mode semiconductor laser with a spatial modulation structure, such as Figures 1-4 As shown, it includes, from bottom to top, an N-plane metal, a GaAs substrate 1, an N-confinement layer 2, an N-waveguide layer 3, a quantum well active layer 4, a P-waveguide layer 5, a P-confinement layer 6, and a P-plane metal.
[0040] There is no spatial modulation structure in the middle region of the chip, and the middle region of the P-confining layer is covered with an ohmic contact layer 7 (there is no ohmic contact layer in other positions). A spatial modulation structure 10 is provided on the P-confining layer except for the middle region. The spatial modulation structure 10 includes a number of holes that gradually increase from the middle to the edge, so that the effective refractive index of the spatial modulation structure changes from strong to weak from the middle to the edge, and a waveguide region 11 is formed in the middle region.
[0041] An insulating layer 12 is covered on the P-limiting layer except for the middle region. The insulating layer 12 also permeates into the inner wall of the hole of the spatial modulation structure to form an insulating thin layer, thereby achieving insulation. The filling depth of the insulating layer material reaches the P-limiting layer.
[0042] The ohmic contact layer 7 and the insulating layer 12 are flush at the top, and are covered with P-side metal. The insulating layer and the ohmic contact layer are covered with P-side metal, and the P-side metal and the ohmic contact layer are in contact, so that current is injected only into the ohmic contact layer. In other locations, the P-side metal is below the insulating layer, which is isolated from the P-limiting layer.
[0043] The spatial modulation structure makes the P-side flat, reducing damage to the waveguide during subsequent packaging and improving yield. The raised ridge waveguide experiences downward pressure during packaging when in contact with the heat sink, which can easily damage it and affect laser reliability. The spatial modulation structure increases the contact area of the P-side, not only dispersing the downward pressure generated during contact and protecting the ridge waveguide, but also providing better heat dissipation due to the high thermal conductivity of silicon dioxide (1.4 W / m·℃), significantly higher than air, thus improving device stability.
[0044] The middle area is within a 5μm width of the chip center.
[0045] The P-confining layer of this invention contains holes with different duty cycles and diameters, forming a spatial modulation structure. Symmetrical to the chip's center, there is no spatial modulation structure within a 5μm width region in the middle, with the number of holes gradually increasing towards the edges. The distribution of the number of holes is zero in the chip's central region and gradually increases towards the edges. Utilizing the spatial modulation of the refractive index of the confinement layer by these holes creates a refractive index guiding effect similar to a ridge waveguide.
[0046] The insulating layer material is silicon dioxide, and the holes are filled with silicon dioxide material that dissipates heat well, forming an effective refractive index difference and forming a waveguide region in the middle area.
[0047] The spatial modulation structure is symmetrical about the chip's center, with no holes in the central region. The holes in the spatial modulation structure have the same diameter from the center to the edge. Figure 3 The image shows one arrangement of holes.
[0048] Spatial modulation structures need to achieve refractive index guidance. Silica has a refractive index of 1.44, which allows the effective refractive index of the middle region to be higher than that of the sides. The material on both sides of the raised ridge waveguide can be considered as air, and air has a refractive index of 1. Therefore, lasers with spatial modulation structures can use the filled silica material to achieve the refractive index confinement of the ridge waveguide, thereby controlling carrier diffusion and solving problems such as high threshold, low efficiency, and poor beam quality in all P-surface contact packaged chip structures.
[0049] Example 2
[0050] A method for fabricating a ridge waveguide single-mode semiconductor laser with a spatial modulation structure includes the following steps:
[0051] (1) An N-confinement layer 2, an N-waveguide layer 3, a quantum hydrazine active layer 4, a P-waveguide layer 5, a P-confinement layer 6 and an ohmic contact layer 7 are sequentially grown on a substrate using the MOCVD method.
[0052] (2) After photolithography and development, a spatial control structure, i.e., a specific arrangement of holes, is prepared in the middle region using etching technology, with a depth reaching the P-confinement layer;
[0053] The spatial control structure erodes into the P-confining layer, but the structure does not interfere with the P-waveguide layer below the P-confining layer, thus minimizing the impact of structural changes on optical field transmission.
[0054] (3) After photolithography and development, silicon dioxide is grown at the spatial control structure position using PECVD technology. It can be used as a filling material for holes without affecting its use as an insulating layer.
[0055] (4) Remove the insulating layer on the ohmic contact layer in the middle area by photolithography, etching or stripping to leave a contact area for the next step of P-side ohmic contact;
[0056] (7) P-side metal was prepared by vapor deposition;
[0057] (8) After substrate thinning, preparation of N-side metal, alloying, and cleavage, a semiconductor laser chip is finally formed.
[0058] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A ridge waveguide single mode semiconductor laser having a spatially modulated structure, characterized in that, It includes, from bottom to top, an N-plane metal, a substrate, an N-confining layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, a P-confining layer, and a P-plane metal; An ohmic contact layer covers the middle region of the P-confining layer. A spatial modulation structure is provided on the P-confining layer except for the middle region. The spatial modulation structure includes a number of holes that gradually increase from the middle to the edge, so that the effective refractive index of the spatial modulation structure decreases from the middle to the edge, forming a waveguide region in the middle region. The holes of the spatial modulation structure are etched into the P-confining layer. An insulating layer covers the P-restriction layer except for the middle region. The insulating layer also permeates into the inner wall of the hole of the spatial modulation structure to form a thin insulating layer, thereby achieving the insulating function. The ohmic contact layer and the top of the insulating layer are flush, and the P-side metal is covered on top of them.
2. The ridge waveguide single mode semiconductor laser with spatially modulated structure of claim 1, wherein, The middle region is within a 5-8μm width range from the center of the chip.
3. The ridge waveguide single mode semiconductor laser with spatially modulated structure of claim 2, wherein, The insulating layer material is silicon dioxide.
4. The ridge waveguide single mode semiconductor laser with spatially modulated structure of claim 3, wherein, In spatial modulation structures, the aperture diameter is the same or gradually decreases from the center to the edge.
5. The ridge waveguide single mode semiconductor laser with spatially modulated structure of claim 4, wherein, The substrate is a GaAs substrate.
6. A method of manufacturing a ridge waveguide single mode semiconductor laser with a spatially modulated structure according to claim 5, characterized in that, Includes the following steps: (1) An N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, a P-confinement layer, and an ohmic contact layer are sequentially grown on the substrate using the MOCVD method; (2) After photolithography and development, a spatial modulation structure, i.e., a specific arrangement of holes, is prepared in the middle region using etching technology, with a depth reaching the P-confinement layer; (3) After photolithography and development, silicon dioxide is grown at the spatial modulation structure position using PECVD technology; (4) Remove the insulating layer on the ohmic contact layer in the middle area by photolithography, etching or stripping to leave a contact area for the next step of P-side ohmic contact; (5) P-side metal was prepared by vapor deposition; (6) After substrate thinning, preparation of N-side metal, alloy treatment, and cleavage, a semiconductor laser chip is finally formed.