SIDE-EMISSIVING SINGLE-MODE LASER WITH A WAVEGUARD WITH OXIDIZED APERTURE HOLE AND ITS MANUFACTURING METHOD
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- SUN YAT SEN UNIV
- Filing Date
- 2023-12-15
- Publication Date
- 2026-07-16
AI Technical Summary
In the prior art, when making the cover structure and waveguide, the etching grating is too close to the active region, resulting in interface growth defects, forming a non-radiative composite center, and reducing the injection efficiency of the laser.
The side-emitting single-mode laser of the oxidized pore-size waveguide is used to prepare a double-oxidized pore-size waveguide structure by growing an oxide layer on both sides of the active layer and reserved a surface mode selection grating area during the photolithography process. The dry etching and wet oxidation process are used to prepare a double-oxidized pore-size waveguide structure to avoid interfacial growth defects in the secondary epitaxial process.
It improves the current injection efficiency of the laser, reduces leakage current, reduces the scattering loss of the waveguide sidewall, realizes the extremely low threshold current density of the high-performance single-mode laser, and simplifies the preparation process and reduces the risk of chamber contamination.
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Abstract
Description
An edge-emitting single-mode laser with an oxidized aperture waveguide and a method for manufacturing the same Technical Field
[0001] The present invention relates to the field of semiconductor technology, in particular to an oxidized aperture waveguide edge-emitting single-mode laser and a manufacturing method thereof. Background Art
[0002] With the continuous development of artificial intelligence and machine learning technologies in recent years, the massive traffic volume has placed greater bandwidth demands on data centers and high-performance computing interconnects. Faced with the ever-increasing investment in pluggable transceivers, there is an urgent need to address their significant energy consumption. Co-packaged optics, with its more compact packaging structure, has the potential to address the current power consumption bottleneck of pluggable optical modules. Semiconductor lasers account for 10%-20% of the module's power consumption. Fabricating high-performance single-mode lasers with high current conversion efficiency is crucial for reducing average power consumption per bit.
[0003] In traditional industrial mass-produced single-mode lasers, after preparing the top grating, secondary epitaxy is used to complete the growth of the cap layer structure and waveguide fabrication. The etched grating is often very close to the active region. Secondary epitaxy on the etched surface can easily introduce interface growth defects, forming non-radiative recombination centers, thereby reducing the laser's injection efficiency. For single-mode lasers with sidewall gratings, especially GaAs, GaSb, and GaN-based epitaxial structures without an etched cutoff layer, the characteristic size requirements of the single-mode sidewall grating are relatively small. During dry etching, the etch rate difference between the inner and outer grating regions is large, resulting in a large difference between the etch depth of the grating region and the etch depth of the overall waveguide, a phenomenon known as etch footing. This introduces ineffective current diffusion and makes the sidewall grating morphology uncontrollable, resulting in an unstable grating coupling coefficient. Deep etching, while achieving a defined grating morphology, can expose surface states in the active region, resulting in a large number of non-radiative recombination centers. This can be quite severe for small devices with narrow ridge widths, degrading the device's threshold current performance.
[0004] The prior art discloses a single-mode high-power semiconductor laser based on a sampled grating and a preparation method thereof. The semiconductor laser comprises, from bottom to top, a substrate, a buffer layer, a lower confinement layer, a multi-quantum well, an upper confinement layer, a grating layer, a graded doping layer, and a cap layer. The waveguide structure of the semiconductor laser comprises a fan-shaped region and a single-mode waveguide region. The fan-shaped region and the single-mode waveguide region each have an independent power supply electrode. The fan-shaped region has a chirped grating, and the single-mode waveguide region has a uniform grating with an inserted phase shift. The Bragg wavelengths of the semiconductor laser cavity are the same. The light-incoming end face of the waveguide structure is coated with a high-reflection film, and the light-outgoing end face is coated with an anti-reflection film. This prior art has the problem of using a secondary epitaxial growth method to complete the growth of the cap layer structure and the fabrication of the waveguide. The etched grating is often very close to the active region. Performing secondary epitaxial growth on the etched surface is prone to interface growth defects, forming non-radiative recombination centers, thereby reducing the injection efficiency of the laser.
[0005] Summary of the Invention
[0006] One of the purposes of the present invention is to provide an edge-emitting single-mode laser with an oxidized aperture waveguide. A second purpose of the present invention is to provide a method for fabricating an edge-emitting single-mode laser with an oxidized aperture waveguide, so as to solve the problem in the prior art of using secondary epitaxy to complete the growth of the cap layer structure and the fabrication of the waveguide. The etched grating is often very close to the active area, and secondary epitaxy on the etched surface is prone to interface growth defects, forming non-radiative recombination centers, thereby reducing the injection efficiency of the laser.
[0007] To achieve the above objectives, the present invention provides an edge-emitting single-mode laser with an oxidized aperture waveguide. The structure of the edge-emitting single-mode laser with an oxidized aperture waveguide includes, from top to bottom, a top electrode layer, a first contact layer, a surface grating region, a first confinement layer, a first oxide layer, an active layer, a second oxide layer, a second confinement layer, a second contact layer, and a bottom electrode layer. The resonant cavity of the edge-emitting single-mode laser with an oxidized aperture waveguide is confined by the first oxide layer and the second oxide layer to form a single-mode light output aperture.
[0008] The present invention also provides a method for manufacturing an edge-emitting single-mode laser with an oxidized aperture waveguide, comprising the following steps:
[0009] S1. Performing photolithography on a laser epitaxial substrate having oxide layers on both sides of an active layer to obtain a grating window photoresist pattern. After patterning, the first contact layer and part of the first restriction layer of the epitaxial substrate are etched away to reserve an area for preparing a surface mode selection grating, thereby obtaining a substrate with a pre-etched structure.
[0010] S2. Performing photolithography again on the pre-etched structure substrate to prepare a photoresist pattern with a surface grating morphology, i.e., a patterned surface grating;
[0011] S3, performing dry etching and removing the resist on the patterned surface grating to prepare the surface grating of the laser;
[0012] S4, performing photolithography on the surface grating of the laser, and obtaining a device mesa photoresist pattern structure that coincides with the surface grating normal after patterning;
[0013] S5, dry etching and stripping the photoresist pattern structure on the device mesa to expose the double oxide layer window;
[0014] S6. Wet-oxidize the device mesa obtained in step S5 after dry etching and debonding to prepare a double-oxidized aperture waveguide structure with a certain aperture size.
[0015] Preferably, the edge-emitting single-mode laser is a distributed feedback laser or a distributed Bragg reflector laser.
[0016] Preferably, in step S1, the oxide layer is a double-layer structure and is grown on both sides of the active layer, and the thickness of each layer is 10 to 50 nm.
[0017] Preferably, the materials of the first oxide layer and the second oxide layer are AlGaAs ternary compounds with high aluminum components;
[0018] In step S6, the materials of the first oxide layer (115) and the second oxide layer (131) are oxidized into aluminum oxide.
[0019] Preferably, in step S2, the prepared surface grating is a first-order or third-order grating.
[0020] Preferably, in step S3, the dry etching depth on the surface grating is 0 to 400 nm from the active layer.
[0021] Preferably, in step S5, the depth of the dry etching needs to exceed the depth of the oxide layer.
[0022] Preferably, in step S6, the process parameters of the wet oxidation include process gas flow, pressure, concentration or sample temperature.
[0023] Preferably, in step S6, the certain pore size is 1-3 μm.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] The present invention prepares an oxidized aperture as an optical confinement waveguide structure for a single-mode laser. The partially insulated oxidized aperture limits the current injection window, resulting in high current injection efficiency and low leakage current in the device. At the same time, the waveguide sidewall has lower scattering loss, which has a more obvious suppression effect on high-order modes, and is conducive to realizing a high-performance single-mode laser with an extremely low threshold current density. The present invention also introduces a surface grating structure to realize a single-mode laser design with a strong grating coupling coefficient. The preparation process is simple, reliable, and has good repeatability, avoiding a complex secondary epitaxial process, reducing the risk of chamber contamination, and is conducive to the repeatable preparation of high-quality gratings, thereby realizing a multi-wavelength array. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG1 is a schematic flow chart of a method for manufacturing an edge-emitting single-mode laser with an oxidized aperture waveguide according to an embodiment of the present invention;
[0027] FIG2 is a schematic diagram of the structure and optical field distribution of a double-layer oxidized aperture waveguide edge-emitting single-mode laser according to an embodiment of the present invention;
[0028] 3 is a schematic diagram of the current injection direction of the edge-emitting single-mode laser of the double-layer oxidized aperture waveguide according to an embodiment of the present invention;
[0029] 4 is a schematic diagram of the structure and optical field distribution of a single-layer oxidized aperture waveguide edge-emitting single-mode laser according to an embodiment of the present invention;
[0030] 5 is a schematic diagram of the current injection direction of the edge-emitting single-mode laser of the single-layer oxidized aperture waveguide according to an embodiment of the present invention;
[0031] 6 is a schematic diagram of the structure and optical field distribution of another single-layer oxidized aperture waveguide edge-emitting single-mode laser according to an embodiment of the present invention;
[0032] 7 is a schematic diagram of the current injection direction of another single-layer oxidized aperture waveguide edge-emitting single-mode laser according to an embodiment of the present invention;
[0033] FIG8 is a schematic structural diagram of a common single-mode laser;
[0034] FIG9 is a schematic diagram of the information flow of a method for manufacturing an edge-emitting single-mode laser with an oxidized aperture waveguide according to an embodiment of the present invention.
[0035] In the figure, 111 is the top electrode layer; 112 is the first contact layer; 113 is the surface grating region; 114 is the first confinement layer; 115 is the first oxide layer; 121 is the active layer; 131 is the second oxide layer; 132 is the second confinement layer; 133 is the second contact layer; 134 is the bottom electrode layer; and 211 is the light-emitting aperture. DETAILED DESCRIPTION
[0036] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.
[0037] In the description of the present invention, it should be noted that terms such as "center," "longitudinal," "transverse," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate and simplify the description of the present invention and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.
[0039] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.
[0040] Example 1
[0041] As shown in FIG1 , a method for manufacturing an edge-emitting single-mode laser with an oxidized aperture waveguide according to a preferred embodiment of the present invention comprises the following steps:
[0042] S1. Perform photolithography on a laser epitaxial substrate having oxide layers on both sides of the active layer 121 to obtain a grating window photoresist pattern. After patterning, the first contact layer 112 and part of the first confinement layer 114 of the epitaxial substrate are etched away to reserve an area for preparing a surface mode selection grating, thereby obtaining a substrate with a pre-etched structure.
[0043] S2. Performing photolithography again on the pre-etched structure substrate to prepare a photoresist pattern with a surface grating morphology, i.e., a patterned surface grating;
[0044] S3, performing dry etching and removing the resist on the patterned surface grating to prepare the surface grating of the laser;
[0045] S4, performing photolithography on the surface grating of the laser, and obtaining a device mesa photoresist pattern structure that coincides with the surface grating normal after patterning;
[0046] S5, dry etching and stripping the photoresist pattern structure on the device mesa to expose the double oxide layer window;
[0047] S6. Wet-oxidize the device mesa obtained in step S5 after dry etching and debonding to prepare a double-oxidized aperture waveguide structure with a certain aperture size.
[0048] The types of edge-emitting single-mode lasers are distributed feedback lasers (DFB) and distributed Bragg reflector lasers (DBR).
[0049] As shown in FIG8 , the initial structure of the single-mode laser includes, from top to bottom, a top electrode layer 111, a first contact layer 112, a first confinement layer 114, a first oxide layer 115, an active layer 121, a second oxide layer 131, a second confinement layer 132, a second contact layer 133, and a bottom electrode layer 134, wherein the first oxide layer 115 and the second oxide layer 131 are AlGaAs ternary compound structures.
[0050] In step S1 , the oxide layer is a double-layer structure and is grown on both sides of the active layer 121 , with each layer having a thickness of 10 to 50 nm.
[0051] The material of the oxide layer is an AlGaAs ternary compound with a high aluminum component, which forms an insulating low-refractive index oxide material during wet oxidation; in step S6, the materials of the first oxide layer (115) and the second oxide layer (131) are oxidized into aluminum oxide.
[0052] In step S2, the prepared surface grating is a first-order or third-order grating.
[0053] In step S3 , the dry etching depth on the surface grating is 0-400 nm from the active layer 121 , and the etching depth directly affects the coupling strength of the surface grating.
[0054] The mesa structure in step S4 should coincide with the normal line of the surface grating structure in step S3 to improve the injection efficiency.
[0055] In step S5 , the depth of the dry etching needs to exceed the depth of the oxide layer to expose a wet oxidation window.
[0056] In step S6 , the process parameters of the wet oxidation include process gas flow rate, pressure, concentration or sample temperature, which control the oxidation rate of the AlGaAs ternary compound with a high Al content.
[0057] In step S6, the certain aperture size is 1-3 μm.
[0058] As shown in Figure 9, step S1: photolithography is performed on the laser epitaxial substrate with oxide layers on both sides of the active layer 121: the traditional single-mode edge-emitting laser structure does not contain a high-Al content oxide layer, and the ridge waveguide structure is directly etched to form light confinement. In order to reduce the scattering loss during waveguide transmission, high requirements are placed on the etching process. By introducing a double oxide layer into the traditional laser structure, this problem can be avoided in the manufacturing process and the implementation process can be simplified; after patterning through the development process, in order to further enhance the coupling strength between the light field and the grating structure, it is necessary to further etch and remove the first contact layer 112 and part of the first confinement layer 114 of the epitaxial substrate, leaving an area for preparing the surface mode selection grating;
[0059] Step S2: Photolithography is performed again on the substrate of the pre-etched structure obtained in step S1 to prepare a photoresist pattern with a surface grating morphology. Due to the strong coupling coefficient of the surface grating, the edge-emitting single-mode laser of the oxidized aperture waveguide of the present invention can use a first-order or third-order grating, simplifying the exposure process;
[0060] Step S3: Dry etching and resist stripping are performed on the patterned surface grating obtained in step S2, again removing a portion of the material of the first confinement layer 114 to prepare the surface grating of the laser. Due to its small size and periodic structure, the surface grating is difficult to etch deeply. Since step S1 has already pre-etched a portion of the first confinement layer 114, the surface grating of the present invention only requires a shallow etching of 100-300 nm to achieve sufficient coupling strength, simplifying the etching process requirements.
[0061] Step S4: performing photolithography on the structure obtained in step S3 to obtain a mesa photoresist pattern that coincides with the surface grating normal line after patterning. Non-normal line coincidence structure will reduce mode gain and current injection efficiency, affecting device output performance;
[0062] Step S5: dry-etching and de-resisting the mesa structure obtained in step S4 to expose the oxide layer window on the side of the laser epitaxial substrate, which serves as the starting point for wet oxidation;
[0063] Step S6: The post-etching surface obtained in step S5 is wet-oxidized. The oxidation shape is isotropically transferred from the oxide layer window to the center along the etching table, thereby preparing an oxidized aperture waveguide structure with a certain aperture size. As shown in FIG2 , the insulating oxide layer after oxidation can simultaneously limit the current and light of the laser. Adjusting the aperture size can make the laser operate in single mode.
[0064] A thin layer of the same high-aluminum composition is grown on either side of the active layer 121. After a wet oxidation process, an oxidized aperture of a certain size is obtained. Because the oxidized material is an insulating, low-refractive-index aluminum oxide, the resulting oxidized aperture window can serve as both a current-limiting and optical-limiting window, eliminating surface recombination, reducing current leakage, and improving the device's current injection efficiency. Furthermore, the grating structure utilizes a first- or third-order surface grating aligned with the oxidized aperture window normal. Controlling the etching depth achieves a high optical confinement factor, providing sufficient coupling strength for the device and enabling the production of high-quality single-mode devices.
[0065] Example 2
[0066] As shown in Figure 2, the present invention also provides an edge-emitting single-mode laser with an oxidized aperture waveguide. The structure of the edge-emitting single-mode laser includes, from top to bottom, a top electrode layer 111, a first contact layer 112, a surface grating region 113, a first confinement layer 114, a first oxide layer 115, an active layer 121, a second oxide layer 131, a second confinement layer 132, a second contact layer 133 and a bottom electrode layer 134. The resonant cavity of the edge-emitting single-mode laser is confined by the first oxide layer 115 and the second oxide layer 131 to form a single-mode light-emitting aperture 211. The material of the first oxide layer 115 and the second oxide layer 131 is an AlGaAs ternary compound with a high aluminum component.
[0067] As shown in Figures 3-7, Figure 3 is a schematic diagram of the current injection direction of an edge-emitting single-mode laser with a double-layer oxidized aperture waveguide. The resonant cavity of the edge-emitting single-mode laser is electrically confined by the first oxide layer 115 and the second oxide layer 131. The arrows represent the current flow, which highly overlaps with the light exit aperture, facilitating improved device current injection efficiency. Figure 4 is a schematic diagram of the structure and optical field distribution of an edge-emitting single-mode laser with a single-layer oxidized aperture waveguide. The resonant cavity of the edge-emitting single-mode laser is optically confined by the first oxide layer 115, forming a single-mode light exit aperture 211. Figure 5 is a schematic diagram of the current injection direction of an edge-emitting single-mode laser with a single-layer oxidized aperture waveguide. The resonant cavity of the edge-emitting single-mode laser is electrically confined by the first oxide layer 115. The arrows represent the current flow, which highly overlaps with the light exit aperture, facilitating improved device current injection efficiency. Figure 6 is a schematic diagram of the structure and optical field distribution of an edge-emitting single-mode laser with a single-layer oxidized aperture waveguide. The resonant cavity of the edge-emitting single-mode laser is optically confined by the first oxide layer 115, forming a single-mode light exit aperture 211. FIG7 is a schematic diagram of the current injection direction of an edge-emitting single-mode laser in a single-layer oxidized aperture waveguide. The resonant cavity of the edge-emitting single-mode laser is electrically confined by the first oxide layer 115. The arrows represent the current flow, which highly overlaps with the light-emitting aperture, thereby improving the current injection efficiency of the device.
[0068] In summary, the embodiments of the present invention provide an edge-emitting single-mode laser with an oxidized aperture waveguide and a manufacturing method thereof, wherein an oxidized aperture is prepared as an optical confinement waveguide structure for a single-mode laser, and the partially insulated oxidized aperture limits the current injection window, so that the device has high current injection efficiency and low leakage current. At the same time, the waveguide sidewall has lower scattering loss, and the suppression effect on high-order modes is more obvious, which is conducive to realizing a high-performance single-mode laser with an extremely low threshold current density; a surface grating structure is also introduced to realize a single-mode laser design with a strong grating coupling coefficient, and the preparation process is simple and reliable with good repeatability, avoiding a complex secondary epitaxial process, reducing the risk of chamber contamination, and is conducive to the repeatable preparation of high-quality gratings to realize a multi-wavelength array.
[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.
Claims
1. An edge-emitting single-mode laser with an oxidized aperture waveguide, characterized in that: The structure of the oxidized aperture waveguide edge-emitting single-mode laser comprises, from top to bottom, a top electrode layer (111), a first contact layer (112), a surface grating region (113), a first limiting layer (114), a first oxide layer (115), an active layer (121), a second oxide layer (131), a second limiting layer (132), a second contact layer (133) and a bottom electrode layer (134); the resonant cavity of the oxidized aperture waveguide edge-emitting single-mode laser is limited by the first oxide layer (115) and the second oxide layer (131) to form a single-mode light-emitting aperture (211).
2. A method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide, characterized in that: Here are the steps: S1, performing photolithography on a laser epitaxial substrate having an oxide layer on both sides of an active layer (121) to obtain a grating window photoresist pattern, and after patterning, etching away a first contact layer (112) and a portion of a first restriction layer (114) of the epitaxial substrate to reserve an area for preparing a surface mode selection grating, thereby obtaining a substrate with a pre-etched structure; S2, performing photolithography again on the substrate with the pre-etched structure to prepare a photoresist pattern with a surface grating morphology, i.e., a patterned surface grating; S3, performing dry etching and debonding on the patterned surface grating to prepare the surface grating of the laser; S4, performing photolithography on the surface grating of the laser, and obtaining a device mesa photoresist pattern structure that coincides with the surface grating normal after patterning; S5, dry etching and stripping the photoresist pattern structure on the device mesa to expose the double oxide layer window; S6. Wet-oxidize the device mesa obtained in step S5 after dry etching and debonding to prepare a double-oxidized aperture waveguide structure with a certain aperture size.
3. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 2, characterized in that: The types of the edge-emitting single-mode laser are distributed feedback laser and distributed Bragg reflection laser.
4. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S1, the oxide layer is a double-layer structure and is grown on both sides of the active layer (121), and the thickness of each layer is 10-50 nm.
5. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 4, characterized in that: The materials of the first oxide layer (115) and the second oxide layer (131) are AlGaAs ternary compounds with high aluminum components; In step S6, the materials of the first oxide layer (115) and the second oxide layer (131) are oxidized into aluminum oxide.
6. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S2, the prepared surface grating is a first-order or third-order grating.
7. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S3, the dry etching depth on the surface grating is 0 to 400 nm from the active layer (121).
8. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S5, the depth of the dry etching needs to exceed the depth of the oxide layer.
9. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S6, the process parameters of the wet oxidation include process gas flow, pressure, concentration or sample temperature.
10. The method for manufacturing an edge-emitting single-mode laser of an oxidized aperture waveguide according to claim 1, characterized in that: In step S6, the certain pore size is 1-3 um.