Semiconductor laser element and light emitting device
By employing a double passivation layer design with different refractive indices in the semiconductor laser, the stray light problem caused by the ridge structure was solved, improving the luminous performance and far-field spot quality of the laser element, and ensuring the stability and efficiency of the laser output.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QUANZHOU SANAN SEMICON TECH CO LTD
- Filing Date
- 2026-02-27
- Publication Date
- 2026-05-29
Smart Images
Figure CN122118520A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a semiconductor laser element and a light emitting device. Background Technology
[0002] Semiconductor lasers are light source devices widely used in communications, sensing, medical, and industrial processing. Their core working principle relies on the refractive index difference between the waveguide layer and the confinement layer in their internal structure to limit the lasing mode, thereby ensuring the stability of the laser's far-field spot characteristics and output power.
[0003] In the manufacturing process of semiconductor lasers, a ridge structure is typically etched and passivation layers are coated on both sides to form current injection channels. This structural design helps ensure efficient current transmission and confinement within the laser. However, this design has poor side-mode suppression and is prone to stray light problems. Summary of the Invention
[0004] In view of at least one deficiency of the prior art, the purpose of this application is to provide a semiconductor laser element to improve the performance and reliability of the laser element.
[0005] In a first aspect, embodiments of this application provide a semiconductor laser element, the semiconductor laser element comprising at least a semiconductor stack, a first passivation layer, and a second passivation layer; the semiconductor stack having opposing first and second surfaces, the second surface having a mesa, the mesa forming a ridge extending along a first direction; the ridge having an upper surface and a side surface connecting the upper surface and the mesa, the side surface extending along the first direction; the first passivation layer being disposed at least above a portion of the ridge and on the side surface of a portion of the ridge; the second passivation layer at least covering the mesa and extending to connect with the first passivation layer; wherein the refractive index of the first passivation layer is less than the refractive index of the second passivation layer.
[0006] Secondly, this application also provides a light emitting device, which employs a semiconductor laser element as described in the above embodiments.
[0007] Based on the above, compared with the prior art, the semiconductor laser element provided in this application can improve side mode suppression, effectively eliminate stray light, avoid the phenomenon of stripes caused by lateral perturbation of far-field spot, and improve the light emission performance of semiconductor laser element by designing the refractive index difference between the first passivation layer and the second passivation layer on the ridge side.
[0008] Other features and beneficial effects of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing this application. Attached Figure Description
[0009] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 A cross-sectional view of a semiconductor laser element in a conventional design; Figure 2 This is a top view of the semiconductor laser element provided in Embodiment 1 of this application; Figure 3 , Figure 4 for Figure 2 Cross-sectional views of different variations of AA; Figures 5-8 Cross-sectional views of different variations of the semiconductor laser element provided in Embodiment 2 of this application; Figure 9 The graph shows the far-field intensity-angle distribution of semiconductor laser elements in existing conventional structures. Figure 10 This is a graph showing the far-field light intensity-angle distribution of the semiconductor laser element in the structure of this application embodiment; Figure 11 Illumination diagram for far-field testing of semiconductor laser elements in existing conventional structures; Figure 12 This is an illumination diagram of the far-field test of the semiconductor laser element in this embodiment.
[0011] Figure label: 10. Substrate; 20. Semiconductor stack; 21. First semiconductor layer; 22. Active layer; 23. Second semiconductor layer; 20a. Ridge; S1. Mesa; S2. Top surface; S3. Side surface; 31. First passivation layer; 32. Second passivation layer; 40. Ohmic contact layer; 51. First electrode; 52. Second electrode. Detailed Implementation
[0012] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings; the technical features designed in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0013] This application provides a semiconductor laser element, which includes at least a semiconductor stack, a first passivation layer, and a second passivation layer; the semiconductor stack has opposing first and second surfaces, the second surface having a mesa, the mesa forming a ridge extending along a first direction; the ridge has an upper surface and a side surface connecting the upper surface and the mesa, the side surface extending along the first direction; the first passivation layer is disposed at least above a portion of the ridge and on the side surface of a portion of the ridge; the second passivation layer at least covers the mesa and extends to connect with the first passivation layer; wherein the refractive index of the first passivation layer is less than the refractive index of the second passivation layer.
[0014] Furthermore, the first passivation layer extends from the upper part of the ridge towards the side surface of the ridge, and extends to the entire side surface of the ridge; the second passivation layer covers the platform, and the first passivation layer is connected to the second passivation layer at the end near the platform.
[0015] Furthermore, the second passivation layer extends from the platform to a portion of the side surface of the ridge; the first passivation layer extends from above the ridge to a portion of the side surface of the ridge and is connected to the second passivation layer.
[0016] Furthermore, it also includes an ohmic contact layer that at least covers a portion of the upper surface of the ridge, and the first passivation layer covers a portion of the surface of the ohmic contact layer or a portion of the upper surface of the ridge.
[0017] Furthermore, the ohmic contact layer extends from the upper surface of the ridge to cover the upper surface of the second passivation layer.
[0018] Furthermore, the ohmic contact layer extends from the upper surface of the ridge to cover a portion of the side surface of the ridge.
[0019] Furthermore, the second passivation layer extends from the platform to connect with a portion of the side surface of the ridge; the first passivation layer extends from the upper surface of the ohmic contact layer to connect with the upper surface of the second passivation layer.
[0020] Furthermore, the vertical height between the upper surface of the ohmic contact layer and the platform is L1, and the thickness of the second passivation layer is L2, wherein L1 / L2 > 3.
[0021] Furthermore, the refractive index of the first passivation layer is between 1 and 1.9.
[0022] Furthermore, the refractive index of the second passivation layer is greater than or equal to 1.9.
[0023] Furthermore, the material of the first passivation layer includes at least one of SiO2 and Al2O3.
[0024] Furthermore, the material of the second passivation layer includes at least one of Si3N4, TiO2, ZrO2, AlN, Nb2O5, Ta2O5, and HfO2.
[0025] Furthermore, the thickness of the first passivation layer is between 2000 and 4000 angstroms.
[0026] Furthermore, the thickness L2 of the second passivation layer is between 500 and 2000 angstroms.
[0027] This application also provides a light emitting device that employs a semiconductor laser element as described in any of the above embodiments, so as to effectively improve the performance and reliability of the light emitting device.
[0028] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application and through various specific implementation methods.
[0029] Example 1 Please see Figures 2-4 , Figure 2 This is a top view of the semiconductor laser element provided in Embodiment 1 of this application. Figure 3 , Figure 4 yes Figure 2 Cross-sectional views of different variations of AA. To achieve at least one or more of the advantages mentioned above, an embodiment of this application provides a semiconductor laser element comprising at least a substrate 10, a semiconductor stack 20, a first passivation layer 31, and a second passivation layer 32.
[0030] The substrate 10 includes, but is not limited to, gallium nitride substrates, gallium arsenide substrates, sapphire substrates, etc. In this embodiment, the substrate 10 can be a growth substrate or a support substrate. The thickness of the substrate 10 is, for example, at least 40 μm and / or at most 400 μm, preferably 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, and 150 μm.
[0031] The semiconductor stack 20 is located on the substrate 10. In this embodiment, the semiconductor stack 20 can be formed on the substrate 10 by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor deposition (HVPE), physical vapor deposition (PVD), or ion plating. In this embodiment, the semiconductor stack 20 is preferably made of a nitride semiconductor material.
[0032] The semiconductor stack 20 has opposing first and second surfaces, with the first surface located closer to the substrate 10 and the second surface located farther from the substrate 10. The semiconductor stack 20 includes at least an active layer 22, a first semiconductor layer 21 disposed between the active layer 22 and the substrate 10, and a second semiconductor layer 23 disposed on the side of the active layer 22 farther from the substrate 10. In this embodiment, the first semiconductor layer 21 may include, but is not limited to, a lower confinement layer, a lower waveguide layer, and a buffer layer (not shown in the figure), and the second semiconductor layer 23 may include, but is not limited to, an upper waveguide layer, an upper confinement layer, an electron blocking layer, and a contact layer (not shown in the figure). Specific functional layers should be reasonably configured according to actual needs; this embodiment does not impose any limitations on this.
[0033] The lower confinement layer is made of N-type doped material to confine the light field in the direction towards the substrate 10; the upper confinement layer is made of P-type doped material to confine the light field in the direction away from the substrate 10. The lower waveguide layer is made of N-type doped material and the upper waveguide layer is made of P-type doped material to increase the confinement of charge carriers, increase the distribution of charge carriers in the active layer 22, improve the optical confinement factor, reduce the threshold current, and improve the luminous efficiency. Preferably, the lower waveguide layer, upper waveguide layer, upper confinement layer, and lower confinement layer are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, GaO, and BN.
[0034] The active layer 22 can be a single quantum well layer composed of indium gallium nitride / gallium nitride, or a multiple quantum well layer composed of indium gallium nitride / gallium nitride grown in multiple alternating periods, to provide optical gain.
[0035] Furthermore, the semiconductor stack 20 has a mesa S1 on the side away from the substrate 10 (i.e., the second surface), and the mesa S1 forms a ridge 20a extending along a first direction, thereby enabling the formation of an effective refractive index waveguide. The mesa S1 is prepared by selectively etching the surface layer of the extended structure on the side away from the substrate 10. During the etching process, only a portion of the surface layer of the semiconductor stack 20 is removed, and the remaining unetched area forms the ridge 20a. The flat area formed after etching is the mesa S1, and the height difference between the mesa S1 and the ridge 20a is equal to the etching depth. Here, the first direction is the cavity length direction of the semiconductor laser element (e.g., the direction of the resonant cavity). Figure 2As shown, the first direction indicated by the arrow can be either towards or against the direction of light propagation. The ridge 20a extends continuously along the first direction, and its extension length is consistent with the dimension of the semiconductor stack 20 in the first direction, ensuring continuous constraint of the light field along the propagation path. The ridge 20a has an upper surface S2 and a side surface S3 connecting the upper surface S2 and the mesa S1, and the side surface S3 extends along the first direction. That is, the upper surface S2 is a flat plane on the side of the ridge 20a away from the substrate 10, parallel to the mesa S1. There are two side surfaces S3, which are relatively symmetrically distributed about the ridge 20a. Each side surface S3 is a continuous plane, disposed on both sides of the ridge 20a along the first direction. As an example, the depth of the ridge 20a is between 3000 and 7000 angstroms.
[0036] The semiconductor laser element also includes a second electrode 52 located on the side of the semiconductor stack 20 away from the substrate 10 and a first electrode 51 located on the side of the substrate 10 away from the semiconductor stack 20. The second electrode 52 is electrically connected to the second semiconductor layer 23, and the first electrode 51 is electrically connected to the first semiconductor layer 21. Both the first electrode 51 and the second electrode 52 are typically made of metal and electrically connected to the outside environment to control the conduction of the semiconductor laser. The material of the second electrode 52 may include any one of Pd, Pt, Ni, Au, Ti, W, Cu, Ag, Zn, Sn, In, Al, Ir, Rh, or ITO. The material of the first electrode 51 may include any one or a combination of two or more of Ni, Ti, Pd, Pt, Au, Al, TiN, ITO, and IGZO, and is not limited thereto.
[0037] In traditional semiconductor laser device designs, stray light is easily generated on both sides of the master laser mode. This stray light causes lateral perturbations and fringe defects in the far-field beam, severely affecting the beam quality of the laser output. In particular, the passivation layer around the ridge 20a in traditional structures has a single refractive index, such as... Figure 1 As shown, the inventors found that the structure cannot effectively suppress stray light on both sides of the main mode, resulting in excessively high side mode restriction, which in turn leads to mode competition and spot distortion. Especially in single-mode lasers, if the ridge 20a is too deep, this problem will be aggravated, making it easier for higher-order side modes to reach the threshold lasing.
[0038] To address the aforementioned issues, this embodiment is described in detail below. Please refer to the documentation for further details. Figures 2-4 The semiconductor laser element also includes a first passivation layer 31 and a second passivation layer 32. By using a design with different refractive indices for the two passivation layers, the problem of stray light suppression is specifically addressed.
[0039] In specific implementation, the first passivation layer 31 is at least disposed above a portion of the ridges 20a and on the side surface S3 of a portion of the ridges 20a. The arrangement of the first passivation layer 31 above the ridges 20a (i.e., above the upper surface S2) can be flexibly selected. It can be directly attached to and covering the upper surface S2 of the ridges 20a, or it can be indirectly disposed above the ridges 20a through other functional layers such as ohmic contact layers (i.e., above the upper surface S2, spaced apart from the ridges 20a by intermediate functional layers). The upper surface S2 is a flat plane on the side of the ridges 20a away from the substrate 10, and can be flexibly disposed above a partial or complete area of this surface according to actual process requirements. Simultaneously, the first passivation layer extends to a portion of the side surface S3 of the ridge 20a. Here, "side surface S3 of the ridge 20a" specifically refers to the vertical or inclined transition surface connecting the upper surface S2 of the ridge 20a and the mesa S1 of the semiconductor stack 20. "Partial side surface S3" can encompass a local area of a single side surface S3, the entire area of a single side surface S3, or a local and entire area of both side surfaces S3. Similarly, the first passivation layer 31 disposed on one side of the side surface S3 of the ridge 20a can either directly adhere to and cover at least a portion of the side surface S3 of the ridge 20a, or be indirectly disposed on one side of the side surface S3 of the ridge 20a through other functional layers such as an ohmic contact layer.
[0040] When the first passivation layer 31 is prepared using CVD film deposition process, the thickness of the first passivation layer 31 disposed above the ridge 20a will naturally be greater than the thickness of the side surface S3 disposed on the ridge 20a. This thickness difference does not require additional process adjustment and will not affect the stray light suppression effect.
[0041] The second passivation layer 32 at least covers the mesa S1 and extends to connect with the first passivation layer 31. The second passivation layer 32 must completely cover the core area of the mesa S1 related to current transmission and optical field confinement. It can extend to cover the edge area of the mesa S1, or further extend towards the sidewalls of the semiconductor stack 20, depending on actual needs. "Extending to connect with the first passivation layer 31" means that the second passivation layer 32 extends along the mesa S1 to the edge area of the first passivation layer 31, forming a seamless connection. Specifically, this can be manifested as the end edge of the second passivation layer 32 adhering to a portion of the side surface of the first passivation layer 31, or the edge portion of the second passivation layer 32 covering the edge side surface of the first passivation layer 31, or the edge portion of the first passivation layer 31 covering the edge portion of the second passivation layer 32. All these connection methods must ensure the physical continuity and structural stability of the two layers, avoid the risk of interlayer peeling, and simultaneously solve the stray light suppression problem.
[0042] In this embodiment, the refractive index of the first passivation layer 31 is lower than that of the second passivation layer 32. The first passivation layer 31 is positioned close to the ridge 20a; its lower refractive index reduces the refractive index difference between the ridge 20a and adjacent structures, thereby weakening the side-mode confinement effect and reducing stray light generation. The second passivation layer 32, with a higher refractive index, covers the mesa S1 region, forming a refractive index gradient distribution with the first passivation layer 31. This guides the concentrated transmission of the master mode light field while blocking the propagation path of stray light, preventing it from interfering with the formation of far-field light spots and fringes in the master mode. This embodiment addresses the stray light suppression problem specifically through the differentiated refractive index design of the dual passivation layers, without requiring additional limitations on other properties such as thermal expansion coefficient and thermal conductivity. Highly efficient stray light elimination can be achieved simply through refractive index matching, simplifying the process while ensuring stable performance. Especially for single-mode lasers, when the width of the ridge 20a is narrow, its deep etching depth may cause an excessive refractive index difference on both sides of the ridge 20a, making it easy for higher-order lateral modes to reach the threshold lasing. However, by covering the side surface S3 of the ridge 20a with the first passivation layer 31, the abrupt change in refractive index can be further buffered. Combined with the high refractive index guidance of the second passivation layer 32, higher-order modes can be effectively suppressed, avoiding far-field spot stripe defects caused by mode competition.
[0043] Optionally, referring to 3, the first passivation layer 31 extends from the upper part of the ridge 20a to the side surface S3 of the ridge 20a, and extends to the entire side surface S3 of the ridge 20a; the first passivation layer 31 at the end near the platform S1 (i.e. Figure 3 The first passivation layer 31 located at the bottom of the ridge 20a is connected to the second passivation layer 32.
[0044] In specific implementation, the first passivation layer 31 extends downward from the upper surface S2 of the ridge 20a and can be arranged on the two side surfaces S3 of the ridge 20a through direct or indirect coverage, thereby forming a fully enclosed low-refractive-index constraint layer on the outside of the side surfaces S3. This full-coverage design maximizes the stray light suppression effect of the first passivation layer 31, avoids abrupt changes in refractive index caused by partial uncovering of the side surfaces S3, and thus prevents stray light from scattering or propagating in the uncovered areas. Since the side surfaces S3 of the ridge 20a extend continuously along the first direction, this embodiment preferably also covers the entire length of the first passivation layer 31 along the first direction, and its extension length is completely consistent with the extension length of the ridge 20a, ensuring that the light field is uniformly constrained by low refractive index throughout the entire propagation path. When prepared using a CVD film deposition process, the thickness of the first passivation layer 31 on the upper surface S2 of the ridge 20a is naturally greater than the thickness of the side surfaces S3. The thicker passivation layer on the upper surface S2 can enhance the longitudinal constraint on the main mode optical field, while the appropriate thickness on the side surface S3 can effectively block stray light while avoiding the introduction of additional light absorption loss due to excessive film thickness.
[0045] like Figure 3 As shown, the second passivation layer 32 covers the entire mesa S1 of the semiconductor stack 20. Since the first passivation layer 31 covers the entire side surface S3 of the ridge 20a, the second passivation layer 32 does not directly contact the side surface S3 of the ridge 20a; that is, the first passivation layer 31 separates the side surface S3 of the ridge 20a from the second passivation layer 32. In this embodiment, the end of the first passivation layer 31 near the mesa S1 contacts the edge of the second passivation layer 32.
[0046] By designing the first passivation layer 31, which has a low refractive index, to fully enclose the outer side surface S3 of the ridge 20a, the refractive index gradient between the ridge 20a and the mesa S1 can be more effectively buffered, thus completely weakening the side mode confinement effect and preventing stray light from both sides of the main mode from escaping from the side surface S3. The second passivation layer 32, with a high refractive index, covers the mesa S1, creating a refractive index difference with the first passivation layer 31. This effectively guides the main mode light field to concentrate in the ridge 20a and the active layer 22 region for transmission, while blocking the propagation path of stray light and further eliminating lateral disturbances and fringe defects in the far-field spot.
[0047] In another alternative implementation, please refer to Figure 4 The second passivation layer 32 extends from the mesa S1 to connect with a portion of the side surface S3 of the ridge 20a; the first passivation layer 31 extends from above the ridge 20a to a portion of the side surface S3 of the ridge 20a and is connected with the second passivation layer 32. That is, unlike the above structure, the second passivation layer 32 directly contacts the side surface S3 of the ridge 20a or is indirectly disposed on the outside of the side surface S3 through other functional layers. It starts from the mesa S1 of the semiconductor stack 20 and extends towards the side surface S3 of the ridge 20a, ultimately directly or indirectly covering a portion, rather than all, of the side surface S3 of the ridge 20a. The first passivation layer 31 extends downward from the upper surface S2 of the ridge 20a, similarly directly or indirectly covering a portion of the side surface S3 of the ridge 20a, and the extended area is adjacent to or partially overlaps with the coverage area of the second passivation layer 32 on the side surface S3, ultimately achieving a tight connection with the second passivation layer 32. The extension path of the first passivation layer 31 needs to be adapted to the extension direction of the second passivation layer 32. If the second passivation layer 32 covers the lower middle region of the side surface S3, the first passivation layer 31 can cover the upper middle region of the side surface S3 and extend to dock with the second passivation layer 32, or the two can overlap at the same height in the side surface S3.
[0048] The above design can further enhance the blocking effect of high refractive index material on stray light. Combined with the low refractive index constraint of the first passivation layer 31, it can effectively reduce the refractive index difference on both sides of the ridge 20a, weaken the side mode restriction effect, and prevent stray light from escaping from the uncovered area of the side surface S3.
[0049] Based on the above embodiments, in this embodiment, the refractive index of the first passivation layer 31 is preferably between 1 and 1.9. It should be noted that the refractive index range of the first passivation layer 31 includes 1 and 1.9. That is, the material of the first passivation layer 31 is a low refractive index material whose refractive index strictly falls within this range. Specifically, at least one of SiO2 and Al2O3 can be selected. Such materials not only meet the refractive index requirements, but also have good film-forming compatibility and structural stability, are suitable for mainstream preparation processes such as CVD, and have excellent interfacial adhesion with the semiconductor stack 20 and the second passivation layer 32, without causing interlayer delamination or defect accumulation problems. The refractive index of the second passivation layer 32 is greater than or equal to 1.9. Its material must be of a high refractive index and complementary to the properties of the first passivation layer 31. Specifically, it can include at least one of Si3N4, TiO2, ZrO2, AlN, Nb2O5, Ta2O5, and HfO2. This material combination has eliminated Al2O3, which overlaps with the refractive index range of the first passivation layer 31, and GaN, which is not suitable for passivation, ensuring the stable and reliable high refractive index characteristics of the second passivation layer 32. This type of high refractive index material not only forms a clear refractive index difference with the first passivation layer 31, but also possesses good insulation and environmental resistance, effectively protecting the mesa S1 region from external impurities while not interfering with the current transmission path.
[0050] The first passivation layer 31, as a low-refractive-index constraint layer that directly or indirectly covers the ridge 20a, needs sufficient thickness to form a stable and continuous optical barrier, preventing stray light from penetrating and escaping through the passivation layer, while ensuring close adhesion to the surface of the ridge 20a to reduce interface defects. As an example, the thickness of the first passivation layer 31 is between 2000 and 4000 angstroms; for example, 2000 angstroms, 2400 angstroms, 2500 angstroms, 2600 angstroms, 2800 angstroms, 3000 angstroms, 3200 angstroms, 3500 angstroms, 3600 angstroms, and 4000 angstroms.
[0051] The second passivation layer 32, as a high-refractive-index guiding layer covering the mesa S1, plays a crucial role in forming a refractive index gradient with the first passivation layer 31. Excessive thickness may introduce additional light absorption losses; therefore, it is preferable to control its thickness to not exceed that of the first passivation layer 31. This ensures both the light field guiding function and the light extraction efficiency of the device. For example, the thickness L2 of the second passivation layer 32 is between 500 and 2000 angstroms; for instance, 500 angstroms, 600 angstroms, 800 angstroms, 1000 angstroms, 1200 angstroms, 1500 angstroms, 1600 angstroms, 1800 angstroms, and 2000 angstroms.
[0052] The aforementioned thickness design is also adapted to the characteristics of the CVD film deposition process. The first passivation layer 31, with a thickness range of 2000 to 4000 angstroms, can meet the thickness difference requirements when covering the upper surface S2 and the side surface S3 of the ridge 20a. Even if the CVD process causes the thickness of the upper surface S2 to be naturally greater than that of the side surface S3, it can still ensure that the passivation layer thickness of the side surface S3 is not less than 2000 angstroms, which is sufficient to block stray light. The second passivation layer 32, with a thickness range of 500 to 2000 angstroms, not only ensures complete coverage of the mesa S1 region, but also avoids stress accumulation or increased optical loss due to excessive film thickness.
[0053] When the first passivation layer 31 is SiO2 and the second passivation layer 32 is Si3N4, the structure in which the thickness of the first passivation layer 31 is greater than the thickness of the second passivation layer 32 can create a stronger optical field constraint in the low refractive index region around the ridge 20a. Stray light is blocked near the ridge 20a and cannot propagate to the mesa S1 region. When the thicknesses of the first passivation layer 31 and the second passivation layer 32 are equal (e.g., both are 2000 angstroms), the first passivation layer 31 can still ensure sufficient constraint strength, and the second passivation layer 32 will not introduce additional losses due to excessive thickness, thus achieving a good stray light suppression effect.
[0054] The structural design of this embodiment is also compatible with GaN-based laser elements of different wavelengths such as blue and green light, and the fabrication process is seamlessly integrated with the existing mass production process of semiconductor laser elements, without the need for additional special equipment or processes.
[0055] It should be understood that, due to limitations in process precision, the anisotropic corrosion characteristics of etching processes, differences in the conformability of film formation processes, and the influence of the material's own crystal orientation, the sides of each layer structure are not absolutely vertical as shown in the attached diagram. They may exhibit a slightly tilted slope design due to process fluctuations, or a slope with a specific tilt angle intentionally designed based on process requirements (such as...). Figure 6 The inclined planes shown are all conventional process fluctuations or simple and reasonable process adjustments in this field, and all fall within the protection scope of the technical solution of this application, and are not intended to limit the technical solution of this application.
[0056] Example 2 Based on the above embodiment one, please refer to Figures 5-8 This embodiment also includes an ohmic contact layer 40, which at least covers a portion of the upper surface S2 of the ridge 20a. Its core function is to reduce the contact resistance between the ridge 20a and the first electrode 51, preventing the formation of a Schottky contact, ensuring efficient current conduction and uniform injection into the active layer 22, while not interfering with the stray light suppression functions of the first passivation layer 31 and the second passivation layer 32, thus achieving synergistic optimization of electrical and optical performance.
[0057] The ohmic contact layer 40 is made of a transparent conductive material with good conductivity and light transmittance. Specifically, at least one of ITO (indium tin oxide), ZnO (zinc oxide), IZO (indium zinc oxide), and Ga2O3 (gallium oxide) can be selected. Such materials can ensure smooth current transmission and will not significantly absorb the laser light field.
[0058] The ohmic contact layer 40 may cover only part or all of the upper surface S2 of the ridge 20a (e.g., Figure 5 , Figure 6 ), or extending from the upper surface S2 of the ridge 20a to cover part of the side surface S3 of the ridge 20a (e.g. Figure 7 When the ohmic contact layer 40 covers a portion of the upper surface S2, the first passivation layer 31 covers a portion of the surface of the ohmic contact layer 40 or a portion of the upper surface S2 of the ridge 20a; that is, both uncovered and covered areas can contact the first passivation layer 31. When the ohmic contact layer 40 covers the entire upper surface S2, the ohmic contact layer 40 completely adheres to the upper surface S2 of the ridge 20a, and the upper surface edge of the ohmic contact layer 40 is flush with or partially overlaps the first passivation layer 31. In this case, the first passivation layer 31 can optionally extend from the upper surface edge of the ohmic contact layer 40 to the side surface S3 of the ridge 20a, completely covering the side surface S3 of the ridge 20a, and its end connects with the second passivation layer 32 on the platform S1; or the first passivation layer 31 only covers a portion of the side surface S3 of the ridge 20a and connects with the second passivation layer 32 extending to the side surface S3. When the ohmic contact layer 40 extends from the upper surface S2 of the ridge 20a to cover a portion of the side surface S3 of the ridge 20a, the "partial side surface S3" can refer to a local area of a single side surface S3 or a corresponding local area of both side surfaces S3. At this time, the first passivation layer 31 covers the surface of the ohmic contact layer 40 located on the side surface S3 and is connected to the second passivation layer 32.
[0059] The performance of semiconductor laser devices can be further improved by designing the positions of the ohmic contact layer 40, the first passivation layer 31, and the second passivation layer 32 as described above. Specifically, the ohmic contact layer 40 ensures a uniform distribution of injected current across the ridge 20a and the active layer 22, preventing localized heating or optical field distortion caused by uneven current distribution. The first passivation layer 31 and the second passivation layer 32 suppress stray light through refractive index differences, improving far-field beam quality. The combination of these two elements enables the device to simultaneously possess low threshold current, high output power, and excellent beam quality.
[0060] Optionally, such as Figure 5As shown, the first passivation layer 31 extends from the upper surface of the ohmic contact layer 40 (i.e., the surface of the ohmic contact layer 40 away from the semiconductor stack 20) to the side surface S3 of the ridge 20a and covers the entire side surface S3 of the ridge 20a; the second passivation layer 32 covers the mesa S1, and the end of the first passivation layer 31 is connected to the second passivation layer 32.
[0061] In specific implementation, the ohmic contact layer 40 preferentially and completely covers the upper surface S2 of the ridge 20a, with its edge flush with the boundary of the upper surface S2 of the ridge 20a, ensuring that current can uniformly cover the entire upper surface S2 of the ridge 20a and be injected downwards into the active layer 22. The first passivation layer 31 extends downwards from the upper surface edge of the ohmic contact layer 40 in a direction perpendicular to the substrate 10, closely adhering to the two side surfaces S3 of the ridge 20a until it completely covers the entire side surface S3 without any exposed areas. The second passivation layer 32 completely covers the entire mesa S1 of the semiconductor stack 20. That is, the second passivation layer 32 is separated from the side surface S3 of the ridge 20a by the first passivation layer 31. The end of the first passivation layer 31 is connected to the edge of the second passivation layer 32, specifically, one end of the first passivation layer 31 on the mesa S1 is in contact with the second passivation layer 32. The specific configuration is determined according to actual requirements.
[0062] In another alternative implementation, such as Figure 6 As shown, the second passivation layer 32 extends from the mesa S1 to connect with a portion of the side surface S3 of the ridge 20a; the first passivation layer 31 extends from the upper surface of the ohmic contact layer 40 to connect with the upper surface of the second passivation layer 32 (i.e., the side surface of the second passivation layer 32 away from the semiconductor stack 20). That is, compared to the scheme where the second passivation layer 32 and the side surface S3 of the ridge 20a are separated by the first passivation layer 31, the second passivation layer 32 can also directly contact the side surface S3 of the ridge 20a, while the first passivation layer 31 extends downward from the upper surface of the ohmic contact layer 40, covering a portion of the side surface S3. The extended and covered area is adjacent to or partially overlaps with the area covered by the second passivation layer 32 on the side surface S3, thus achieving connection with the second passivation layer 32. This design also effectively suppresses stray light and eliminates lateral disturbances and stripe defects in the far-field spot.
[0063] On the basis of direct contact between the second passivation layer 32 and the side surface S3 of the ridge 20a, preferably, as Figure 6 , Figure 7 , Figure 8 As shown, the vertical height between the upper surface of the ohmic contact layer 40 and the platform S1 is L1, and the thickness of the second passivation layer 32 is L2, wherein L1 / L2 > 3.
[0064] In specific implementation, L1 is the vertical distance between the upper surface of the ohmic contact layer 40 and the mesa S1, and L2 is the thickness of the second passivation layer 32 itself. By limiting the ratio of L1 / L2 to 3, the second passivation layer 32 can be made thinner and have a higher equivalent refractive index while ensuring sufficient insulation performance. This enhances the ability to confine the light field and reduces light transmission loss, allowing the laser to be output more efficiently and smoothly.
[0065] Better, such as Figure 8 As shown, the ohmic contact layer 40 extends from the upper surface S2 of the ridge 20a to cover the upper surface of the first passivation layer 31 (i.e., the side of the first passivation layer 31 away from the semiconductor stack 20). In specific implementation, the ohmic contact layer 40 first completely covers the entire upper surface S2 of the ridge 20a to ensure an ohmic contact with the ridge 20a, thereby ensuring uniform current injection into the active layer 22; then it extends outwards to cover the upper surface of the first passivation layer 31. This design not only ensures a stable bond with the first passivation layer 31, but also increases the contact area between the ohmic contact layer 40 and the first electrode 51, allowing the injected current to diffuse more efficiently throughout the ridge 20a and the active layer 22, avoiding current congestion. Simultaneously, the uniform current distribution reduces localized heating, prevents optical field distortion caused by uneven temperature, and ensures the stability of the laser output power.
[0066] Furthermore, when the ohmic contact layer 40 includes a metallic material, the metallic light absorption effect of the ohmic contact layer 40 can be used to absorb stray light, further weakening the propagation and interference of stray light, thereby allowing the lateral disturbance and stripe defects of the far-field spot to be eliminated more thoroughly.
[0067] Furthermore, the specific structure, materials, functions, and other designs of the first passivation layer 31 and the second passivation layer 32 can be referred to in Embodiment 1, and will not be repeated here.
[0068] To effectively illustrate the effects of the above embodiments, this solution conducts far-field performance tests on semiconductor laser elements with conventional structures and those of the embodiments of this application, respectively, using quantitative intensity-angle distribution curves and qualitative spot effects. For semiconductor laser elements employing a single refractive index passivation layer in conventional technology, far-field intensity-angle distribution tests are performed, yielding the following results: Figure 9 The curves shown (horizontal axis represents the far-field divergence angle, and vertical axis represents the relative light intensity) show multiple distinct secondary peaks on both sides of the main intensity peak of the red and blue curves. Some of these secondary peaks have a relative intensity exceeding 0.1. This characteristic corresponds to the fine stripe defect in the far-field light spot. Essentially, the single refractive index passivation layer cannot buffer the refractive index gradient between the ridge 20a and the mesa S1. Stray lights on both sides of the main mode are not suppressed. These stray lights diverge at different angles and superimpose with the main mode, ultimately leading to a dispersed light field distribution and a significant decrease in uniformity.
[0069] Regarding the embodiments of this application Figure 5 The semiconductor laser element with a birefringence passivation layer shown in the structure was tested under the same test conditions (same test distance, drive current, and environmental parameters), and the results were as follows. Figure 10 The far-field intensity-angle distribution curve is shown. The main intensity peak is sharp and concentrated, while the secondary peaks on either side of the main peak almost completely disappear, with only weak background fluctuations (relative intensity less than 0.1) existing over a very wide angular range. This change confirms the gradient design effect of the double passivation layers: the low-refractive-index first passivation layer 31 buffers the abrupt change in refractive index between the ridge 20a and the mesa S1, while the high-refractive-index second passivation layer 32 guides the concentrated transmission of the main mode light field. Together, they block the generation and propagation path of stray light, stably confining the light field to the main mode direction, thus completely suppressing the interference of stray light on the main mode.
[0070] In the corresponding far-field spot test, the existing conventional structure components exhibit the following characteristics: Figure 11 The effect shown. According to... Figure 11 It can be seen that fine, multiple stripes are distributed around the light spot, and there are obvious lateral diffusion traces at the edges, which is consistent with... Figure 9 The light intensity curve characteristics are completely consistent, indicating that the lateral disturbances and stripe defects caused by stray light result in extremely poor beam uniformity and concentration, making it difficult to meet the beam quality requirements of high-precision scenarios.
[0071] In the embodiments of this application Figure 5 The far-field spot of the element shown in the structure under the same conditions ( Figure 12 It exhibits a clear and regular outline, without any fine stripes around it, and no obvious diffusion at the edges; this is consistent with... Figure 10 The concentrated light intensity curves corroborate each other, indicating that the differentiated design of the double passivation layer forms a continuous gradient light field modulation. The main mode light field is stably constrained in the ridge 20a and active layer 22 regions, the interference of stray light is completely eliminated, and the uniformity and concentration of the far-field light spot are significantly improved.
[0072] In summary, from the quantitative intensity-angle distribution curve to the qualitative far-field spot effect, the double passivation layer refractive index gradient design of the present application embodiment has been verified to effectively suppress stray light, completely solve the problem of spot distortion in conventional technology, and significantly improve the quality of laser beam.
[0073] Example 3 This application also provides a light emitting device, which includes at least one semiconductor laser element as described in any of the above embodiments, which can effectively improve the light emission performance and can be applied to light emitting devices using semiconductor laser elements in various industries.
[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A semiconductor laser element, characterized in that, The semiconductor laser element includes: A semiconductor stack has opposing first and second surfaces, the second surface having a mesa, the mesa having a ridge extending along a first direction; the ridge having an upper surface and a side surface connecting the upper surface and the mesa, the side surface extending along the first direction; A first passivation layer is disposed at least above a portion of the ridge and on the side surface of a portion of the ridge; A second passivation layer at least covers the platform and extends to connect with the first passivation layer; wherein the refractive index of the first passivation layer is less than the refractive index of the second passivation layer.
2. The semiconductor laser element according to claim 1, characterized in that: The first passivation layer extends from the top of the ridge to the side surface of the ridge and extends to the entire side surface of the ridge; the first passivation layer is connected to the second passivation layer at the end near the platform.
3. The semiconductor laser element according to claim 1, characterized in that: The second passivation layer extends from the platform to a portion of the side surface of the ridge; the first passivation layer extends from above the ridge to a portion of the side surface of the ridge and is connected to the second passivation layer.
4. The semiconductor laser element according to claim 1, characterized in that: It also includes an ohmic contact layer that at least covers a portion of the upper surface of the ridge, and the first passivation layer covers a portion of the surface of the ohmic contact layer or a portion of the upper surface of the ridge.
5. The semiconductor laser element according to claim 4, characterized in that: The ohmic contact layer extends from the upper surface of the ridge to cover the upper surface of the second passivation layer.
6. The semiconductor laser element according to claim 4, characterized in that: The ohmic contact layer extends from the upper surface of the ridge and covers a portion of the side surface of the ridge.
7. The semiconductor laser element according to claim 4, characterized in that: The second passivation layer extends from the platform to connect with a portion of the side surface of the ridge; the first passivation layer extends from the upper surface of the ohmic contact layer to connect with the upper surface of the second passivation layer.
8. The semiconductor laser element according to claim 7, characterized in that: The vertical height between the upper surface of the ohmic contact layer and the platform is L1, and the thickness of the second passivation layer is L2, wherein L1 / L2 > 3.
9. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The refractive index of the first passivation layer is between 1 and 1.
9.
10. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The refractive index of the second passivation layer is greater than or equal to 1.
9.
11. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The material of the first passivation layer includes at least one of SiO2 and Al2O3.
12. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The material of the second passivation layer includes at least one of Si3N4, TiO2, ZrO2, AlN, Nb2O5, Ta2O5, and HfO2.
13. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The thickness of the first passivation layer is between 2000 and 4000 angstroms.
14. The semiconductor laser element according to any one of claims 1 to 8, characterized in that: The thickness L2 of the second passivation layer is between 500 and 2000 angstroms.
15. A light emitting device, characterized in that: This includes using a semiconductor laser element as described in any one of claims 1 to 14.