Semiconductor structure and method of manufacturing the same, semiconductor laser

Abstract

The application provides a semiconductor structure and a preparation method thereof and a semiconductor laser, and relates to the field of lasers. The semiconductor structure comprises a substrate, a first waveguide layer, a resonant structure and a second waveguide layer; the first waveguide layer is arranged on the surface of the substrate along the thickness direction; the resonant structure comprises an active region, an input layer and an output layer; the active region, the input layer and the output layer are arranged on the side of the first waveguide layer away from the substrate; in a plane parallel to the plane in which the substrate is located, the input layer and the output layer are located on the two sides of the active region, and the output layer is arranged obliquely; in the direction away from the substrate, the output layer is away from the input layer; the second waveguide layer is arranged on the side of the resonant structure away from the surface of the first waveguide layer, and the second waveguide layer is connected with the resonant structure. The application can reduce the possibility of interference effect between reflected light and the light field in the FP cavity, make the longitudinal mode output of the semiconductor structure more stable, and improve the spectral purity of the semiconductor structure.

Description

Technical Field

[0001] This application relates to the field of lasers, and more particularly to semiconductor structures and their fabrication methods, and semiconductor lasers. Background Technology

[0002] FP-cavity lasers are a common semiconductor structure with advantages such as simple structure and high reliability. However, FP-cavity lasers suffer from problems such as longitudinal mode instability and low spectral purity, resulting in poor light output performance. Summary of the Invention

[0003] This application provides a semiconductor structure and its fabrication method, as well as a semiconductor laser, to solve the problems of longitudinal mode instability and low spectral purity in FP cavity lasers, and the poor light output performance of FP cavity lasers.

[0004] The semiconductor structure provided in this application includes a substrate, a first waveguide layer, a resonant structure, and a second waveguide layer.

[0005] The first waveguide layer is disposed on the surface of the substrate along the thickness direction;

[0006] The resonant structure includes an active region, an input layer, and an output layer, wherein the active region, the input layer, and the output layer are disposed on the side of the first waveguide layer away from the substrate;

[0007] In a plane parallel to the substrate, the input layer and the output layer are located on opposite sides of the active region, and the output layer is inclined and is located away from the input layer in a direction away from the substrate.

[0008] The second waveguide layer is disposed on the surface of the resonant structure away from the first waveguide layer, and the second waveguide layer is connected to the resonant structure.

[0009] By adopting the above technical solution, the semiconductor structure includes a substrate, a first waveguide layer, a resonant structure, and a second waveguide layer. In the resonant structure, the input layer and the output layer are located on opposite sides of the active region. The output layer is tilted relative to the thickness direction of the substrate, and in the direction away from the substrate, the output layer is away from the input layer, resulting in the input and output layers not being parallel.

[0010] In related technologies, the input layer and output layer are usually arranged in parallel and opposite to each other on both sides of the active region. When the semiconductor structure is in operation, interference effects are easily generated between the reflected light in the resonant structure and the light field in the FP cavity, which causes problems such as longitudinal mode instability and low spectral purity in the semiconductor structure.

[0011] In this embodiment, the output layer is tilted relative to the thickness direction of the substrate, so that the input layer and the output layer are not parallel. This causes the reflected light to deviate to a certain extent, thereby reducing the possibility of interference between the reflected light and the optical field in the FP cavity. This makes the longitudinal mode output of the semiconductor structure more stable and improves the spectral purity of the semiconductor structure.

[0012] In some possible implementations, the angle between the output layer and the thickness direction of the substrate is greater than or equal to 2 degrees and less than or equal to 6 degrees.

[0013] And / or, the angle between the output layer and the thickness direction of the substrate is greater than or equal to 2.8 degrees and less than or equal to 3.2 degrees.

[0014] In some possible implementations, the output layer is configured as a multilayer output layer, wherein the multilayer output layer has a reflectivity of less than 0.1% at a wavelength of 970 nm and a transmittance of greater than 99.5% at a wavelength of 970 nm.

[0015] And / or, the input layer is configured as a quarter-wavelength stacked structure, and the reflectivity of the input layer is greater than 90%.

[0016] In some possible implementations, the input layer is provided with a Bragg grating extending toward the output layer, and at least a portion of the Bragg grating is located within the active region.

[0017] In some possible implementations, the period of the Bragg grating is greater than or equal to 137.6 nanometers and less than or equal to 147.6 nanometers;

[0018] And / or, the depth of the Bragg grating is greater than or equal to 100 nanometers and less than or equal to 200 nanometers.

[0019] In some possible implementations, the width of the first waveguide layer is greater than or equal to 2 micrometers and less than or equal to 5 micrometers; the thickness of the first waveguide layer is greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

[0020] And / or, the width of the second waveguide layer is greater than or equal to 2 micrometers and less than or equal to 5 micrometers; the thickness of the second waveguide layer is greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

[0021] In some possible implementations, the length of the active region is greater than or equal to 0.8 mm and less than or equal to 1.5 mm in the direction of the line connecting the input layer and the output layer.

[0022] In some possible implementations, a first electrode and a second electrode are also included, wherein the first electrode and the second electrode are configured as strip electrodes;

[0023] The first electrode is disposed on the surface of the substrate away from the first waveguide layer, and the second electrode is disposed on the surface of the second waveguide layer away from the substrate.

[0024] This application provides a method for fabricating a semiconductor structure, including:

[0025] A first waveguide foundation, an active region foundation, and a second waveguide foundation are sequentially formed on the substrate;

[0026] A portion of the first waveguide foundation, a portion of the active region, and a portion of the second waveguide foundation are removed to form a first waveguide layer, an active region, and a second waveguide layer; the first end face of the active region is perpendicular to the substrate, and the second end face of the active region is inclined.

[0027] An input layer and an output layer are formed, wherein the input layer is located on the first end face of the active region and the output layer is located on the second end face of the active region.

[0028] In some possible implementations, including:

[0029] A Bragg grating is formed on the first end face of the active region, and the Bragg grating extends toward the second end face of the active region;

[0030] The input layer is formed, with a first portion covering the first end face of the active region and a second portion covering the Bragg grating.

[0031] This application provides a semiconductor laser, including the semiconductor structure described in any of the above embodiments.

[0032] Since the semiconductor laser includes any of the above-mentioned semiconductor structures, the advantages of the semiconductor laser including any of the above-mentioned semiconductor structures can be found in the relevant description above, and will not be repeated here. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0034] Figure 1 A front view schematic diagram of the semiconductor structure provided in the embodiments of this application. Figure 1 ;

[0035] Figure 2 A front view schematic diagram of the semiconductor structure provided in the embodiments of this application. Figure 2 ;

[0036] Figure 3This is a side view of the semiconductor structure provided in the embodiments of this application;

[0037] Figure 4 A schematic diagram of the first waveguide layer, resonant structure, and second waveguide layer of the semiconductor structure provided in the embodiments of this application;

[0038] Figure 5 This is a schematic flowchart illustrating the method for fabricating a semiconductor structure according to an embodiment of this application.

[0039] Figure label:

[0040] 10. First electrode; 20. Buffer layer; 30. First confinement layer; 40. Second confinement layer; 50. Contact layer; 60. Second electrode; 70. FP cavity;

[0041] 100. Substrate;

[0042] 200. First waveguide layer;

[0043] 300. Resonant structure; 310. Active region; 320. Input layer; 321. Bragg grating; 330. Output layer;

[0044] 400. Second waveguide layer.

[0045] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0046] In related technologies, semiconductor lasers are a crucial component of optical communication, 3D sensing, and multispectral imaging. Among these, the Fabry-Pérot (FP) cavity structure is a common semiconductor structure used to construct FP cavity lasers, offering advantages such as simple structure and high reliability. The semiconductor structure includes a substrate, a first waveguide layer, a resonant structure, and a second waveguide layer. The resonant structure comprises an active region, an input layer, and an output layer, all disposed on the surface of the first waveguide layer facing away from the substrate. The input and output layers are arranged parallel to each other on opposite sides of the active region. The second waveguide layer is disposed on the surface of the resonant structure away from the first waveguide layer and connects to the resonant structure.

[0047] However, the input and output layers are usually arranged parallel to each other on both sides of the active region. When the semiconductor structure is in operation, interference effects are easily generated between the reflected light in the resonant structure and the light field in the FP cavity, which causes problems such as longitudinal mode instability and low spectral purity in the semiconductor structure. This results in problems such as longitudinal mode instability and low spectral purity in FP cavity lasers, and poor light output performance of FP cavity lasers.

[0048] To address the aforementioned technical problems, embodiments of this application provide a semiconductor structure and its fabrication method, as well as a semiconductor laser. The semiconductor structure includes a substrate, a first waveguide layer, a resonant structure, and a second waveguide layer. In the resonant structure, the input layer and the output layer are located on opposite sides of the active region. The output layer is inclined relative to the thickness direction of the substrate, and in the direction away from the substrate, the output layer is far from the input layer, resulting in the input and output layers not being parallel.

[0049] In this embodiment, the output layer is tilted relative to the thickness direction of the substrate, so that the input layer and the output layer are not parallel. This causes the reflected light to deviate to a certain extent, thereby reducing the possibility of interference between the reflected light and the optical field in the FP cavity. This makes the longitudinal mode output of the semiconductor structure more stable and improves the spectral purity of the semiconductor structure.

[0050] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0051] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0052] See Figure 1 The semiconductor structure provided in this application includes a substrate 100, a first waveguide layer 200, a resonant structure 300, and a second waveguide layer 400. The first waveguide layer 200 is disposed on the surface of the substrate 100 along the thickness direction, and the second waveguide layer 400 is disposed on the surface of the resonant structure 300 away from the first waveguide layer 200. The second waveguide layer 400 is connected to the resonant structure 300.

[0053] For example, the resonant structure 300 includes an active region 310, an input layer 320, and an output layer 330, which are disposed on the side of the first waveguide layer 200 facing away from the substrate 100. The input layer 320 and the output layer 330 are located on opposite sides of the active region 310, and the output layer 330 is inclined, moving away from the input layer 320 in the direction away from the substrate 100.

[0054] It is readily understood that, in a plane parallel to the substrate, the input layer 320 and the output layer 330 are located on opposite sides of the active region 310. The output layer 330 is inclined relative to the thickness direction of the substrate 100. In a direction away from the substrate 100, the output layer 330 is away from the input layer 320, such that the input layer 320 and the output layer 330 are not parallel. The system includes a substrate 100, a first waveguide layer 200, a resonant structure 300, and a second waveguide layer 400.

[0055] In this embodiment, the output layer 330 is tilted relative to the thickness direction of the substrate 100, so that the input layer 320 and the output layer 330 are not parallel. This causes the reflected light to deviate to a certain extent, thereby reducing the possibility of interference between the reflected light and the light field in the FP cavity 70. This makes the longitudinal mode output of the semiconductor structure more stable and improves the spectral purity of the semiconductor structure.

[0056] See also some possible implementations. Figure 2 and Figure 3 A first confinement layer 30 may be disposed on the surface of the first waveguide layer 200 facing the substrate 100. The first confinement layer 30 can be used together with the second confinement layer 40 (mentioned later) located on the surface of the second waveguide layer 400 facing away from the substrate 100 to form a symmetrical or approximately symmetrical barrier structure, which effectively confines injected electrons and holes within the active region 310. The first confinement layer 30 may be made of an aluminum gallium arsenide material with a higher aluminum content than the first waveguide layer 200. The wider bandgap forms a barrier to charge carriers in the energy band, preventing charge carriers injected into the active region 310 from diffusing outward, thereby improving the recombination efficiency of charge carriers and reducing the threshold current. At the same time, the refractive index difference between the first confinement layer 30 and the first waveguide layer 200 also confines the optical field in the vertical direction, which helps to confine the optical mode field within the composite waveguide structure composed of the active region 310, the upper and lower waveguide layers, and the confinement layer, reducing the loss of optical energy leakage into the substrate 100.

[0057] A buffer layer 20 may be disposed on the surface of the first confinement layer 30 facing the substrate 100. The buffer layer 20 can provide a smooth transition between the substrate 100 and the epitaxial functional layer. The buffer layer 20 acts as a template for the initiation of crystal growth, releasing the stress caused by possible minor lattice mismatches or differences in thermal expansion coefficients between the substrate 100 and the epitaxial layer, preventing these stresses from being transmitted upward to the core functional layer such as the active region 310, thereby effectively reducing the proliferation of lattice defects (such as dislocations) and ensuring the growth of a high-quality epitaxial layer.

[0058] A second confinement layer 40 may be disposed on the surface of the second waveguide layer 400 facing away from the substrate 100. The second confinement layer 40, disposed on the surface of the second waveguide layer 400 facing away from the substrate 100, together with the first confinement layer 30, completes the bidirectional confinement of carriers in the active region 310. The second confinement layer 40 may be made of an aluminum gallium arsenide material with a high aluminum content, forming a carrier barrier and a refractive index difference with the second waveguide layer 400.

[0059] A contact layer 50 may be disposed on the surface of the second confinement layer 40 facing away from the substrate 100. The contact layer 50 can be used to improve and stabilize the electrical connection characteristics between the metal electrode and the upper semiconductor material. The second waveguide layer 400 is typically made of an aluminum gallium arsenide material with a specific aluminum composition. When it is in direct contact with the metal electrode, it may form a high contact resistance due to factors such as surface states, band mismatch, or natural oxide layers, resulting in unnecessary Joule heating and voltage drop during device operation, thus reducing power conversion efficiency. By selecting a more suitable semiconductor material and implementing high-concentration doping, the contact layer 50 can reduce contact resistance and form an excellent ohmic contact.

[0060] In some possible implementations, the substrate 100 may be configured as an n-type gallium arsenide (GaAs) substrate 100 (thickness 300 μm, doping concentration...). After being ultrasonically cleaned with organic reagents for 15 minutes, rinsed with deionized water and dried, it was placed into the cavity of the molecular beam epitaxy (MBE) equipment.

[0061] When preparing the first waveguide layer 200, the temperature can be set to 620℃, the flow rate of trimethylaluminum (TMA) can be adjusted, and the first waveguide layer 200 of aluminum gallium arsenide (AlGaAs) with an aluminum (Al) composition of 0.15 and a thickness of 1.5μm can be grown. By adjusting the V / III group source flow rate ratio to 20:1, the refractive index difference of the material can be controlled to reach 1.2%.

[0062] When fabricating the second waveguide layer 400, the temperature can be set to 620℃ to grow an aluminum gallium arsenide (AlGaAs) waveguide layer with an aluminum (Al) composition of 0.15 and a thickness of 1.5μm.

[0063] When preparing the active region 310, a low-temperature growth technique can be used to grow an indium gallium arsenide (InGaAs) quantum well at 580℃ with an indium (In) composition of 0.18 and a thickness of 50nm. The surface smoothness is monitored by real-time reflection high-energy electron diffraction (RHEED), and the roughness is <1nm.

[0064] When preparing the first confinement layer 30, the temperature can be lowered to 620℃ to grow the second confinement layer 40 of aluminum gallium arsenide (AlGaAs) with an aluminum (Al) composition of 0.3 and a thickness of 1.5μm.

[0065] When preparing buffer layer 20, it can be prepared at a temperature of 650°C using trimethylaluminum (TMA), trimethylgallium (TMG), and arsine (...). Using an aluminum (Al) composition of 0.3 as the gas source, an aluminum gallium arsenide (AlGaAs) buffer layer 20 with a thickness of 100 nm and a growth rate of 0.5 μm / h is grown, which effectively reduces the stress mismatch between the substrate 100 and the epitaxial layer.

[0066] When preparing the second confinement layer 40, the temperature can be maintained at 620℃ to grow an aluminum gallium arsenide (AlGaAs) first confinement layer 30 with an aluminum (Al) composition of 0.3 and a thickness of 1.5μm, thereby achieving effective confinement of charge carriers.

[0067] When fabricating contact layer 50, a p-type gallium arsenide (GaAs) contact layer 50 with a thickness of 100 nm can be grown at 550 °C with a doping concentration of [missing information]. Zinc (Zn) is used as the doping source to ensure low-resistance contact with the electrode.

[0068] In some possible implementations, the angle between the output layer 330 and the substrate 100 in the thickness direction can be greater than or equal to 2 degrees and less than or equal to 6 degrees.

[0069] For example, the angle between the output layer 330 and the substrate 100 in the thickness direction can be 3 degrees.

[0070] By setting the output layer 330 as an inclined surface at a specific angle to the direction of light propagation, the propagation path of the light reflected from the inclined surface will be deflected. Within the angle range of 2 to 6 degrees, the reflected light will deviate from the original optical path by 12 to 15 degrees, thus failing to effectively couple back to the original waveguide mode for feedback and oscillation. This effectively suppresses the resonance effect of the Fabry-Perot standard cavity, reduces the influence of end face reflectivity on the cavity mode selection, and creates the necessary conditions for effective wavelength-selective feedback of the Bragg grating 321 integrated on the input side.

[0071] If the angle between the output layer 330 and the substrate 100 in the thickness direction is too small, it will not be enough to deflect the reflected light sufficiently, making it difficult to effectively suppress mode competition; if the angle is too large, it may introduce additional scattering loss, affecting the laser's output efficiency and beam quality. Within this range, especially close to its median value, an optimal balance can be achieved between suppressing unnecessary cavity surface feedback and maintaining low-loss laser output.

[0072] And / or, the angle between the output layer 330 and the substrate 100 in the thickness direction can be greater than or equal to 2.8 degrees and less than or equal to 3.2 degrees.

[0073] In some possible implementations, the output layer 330 can be configured as a multilayer output layer 330, wherein the reflectivity of the multilayer output layer 330 at a wavelength of 970 nm can be less than 0.1%, and the transmittance of the multilayer output layer 330 at a wavelength of 970 nm can be greater than 99.5%.

[0074] The multi-layered output layer 330 reduces Fresnel reflections while simultaneously achieving efficient coupling and output of laser energy. Higher transmittance allows most of the generated laser energy to effectively escape from the resonant structure 300, becoming usable output laser energy. Lower reflectivity weakens the function of the output layer 330's end face as a mirror, preventing it from forming effective Fabry-Perot resonant feedback. Furthermore, it helps reduce the sensitivity of the semiconductor laser, which is extremely sensitive to feedback light, to external reflections, thus improving the device's anti-interference capability and operational stability.

[0075] The multi-layer output layer 330 works in synergy with the tilted cavity surface structure to jointly suppress multi-longitudinal mode oscillations and mode competition behavior caused by end-face reflection, thereby ensuring a stable single-longitudinal mode operating state.

[0076] When preparing the output layer 330, electron beam evaporation technology can be used to sequentially deposit alumina ( (thickness 80nm) and silicon dioxide ( (120nm thick) to form a λ / 4 multilayer film system with a reflectivity of less than 0.1% and a transmittance of greater than 99.5% at a wavelength of 970nm.

[0077] And / or, the input layer 320 can be configured as a quarter-wavelength stacked structure, and the reflectivity of the input layer 320 can be greater than 90%.

[0078] The main function of the high-reflectivity input layer 320 is to form an asymmetric resonant structure 300 together with the low-reflectivity output layer 330. The high reflectivity ensures that most photons arriving at the input end are reflected back to the active region 310 within the resonant structure 300 for further stimulated emission amplification, thereby greatly reducing the threshold current of the laser and improving the internal photon density and differential quantum efficiency.

[0079] The high reflectivity of the input layer 320 contrasts sharply with the low reflectivity of the output layer 330, together determining the net gain and loss distribution within the resonant structure 300, which is a necessary condition for achieving population inversion and laser oscillation.

[0080] The quarter-wavelength stacked structure achieves a high reflectivity of 320 nm in the input layer by leveraging the interference effect at the interfaces of multiple dielectric films. This structure is formed by alternating deposition of two transparent dielectric materials with different refractive indices, each layer having a physical thickness of one-quarter of the target wavelength. The alternating arrangement of high- and low-refractive-index layers allows for constructive interference at the incident interface when light waves are reflected at the interfaces of each layer, thus enhancing the total reflected light intensity; the transmitted light is suppressed due to destructive interference.

[0081] The reflectivity primarily depends on the refractive index contrast between the two materials and the number of stacked periods. A higher number of periods results in a greater refractive index contrast and a higher peak reflectivity. Common film material combinations include titanium dioxide and silicon dioxide, or zinc sulfide and magnesium fluoride, etc.

[0082] For example, titanium dioxide can be deposited when preparing the input layer 320. (thickness 150nm) and silicon dioxide ( (90nm thick) to form a quarter-wavelength stacked structure to achieve a reflectivity greater than 95% and optimize the optical field distribution within the cavity.

[0083] See also some possible implementations. Figure 4 The input layer 320 may be provided with a Bragg grating 321, which may extend toward the output layer 330, and at least a portion of the Bragg grating 321 may be located within the active region 310.

[0084] The Bragg grating 321 can introduce a distributed, highly wavelength-selective optical feedback within the resonant structure 300, effectively reflecting light within a narrow range near a specific wavelength that satisfies its Bragg condition. The arrangement of the Bragg grating 321 extending towards the output layer 330 ensures sufficient interaction with the optical wave field. By placing at least a portion of the Bragg grating 321 within the active region 310, the feedback effect of the Bragg grating 321 can directly act on the gain region, allowing light waves satisfying the Bragg condition to be preferentially amplified, thereby suppressing oscillations of other longitudinal modes and ensuring that the semiconductor structure achieves and maintains a stable single-longitudinal-mode output.

[0085] When fabricating the Bragg grating 321, the grating pattern can first be defined on the semiconductor surface using secondary electron beam lithography, and the exposure dose can be optimized to... A grating stripe with a period of 142.6 nm is defined on the left side with a duty cycle of 0.5. Excess photoresist is removed using a lift-off process to form a metal (chromium Cr / gold Au) mask. Then, an ion beam etching machine is used with argon (Ar) as the etching gas, an accelerating voltage of 1000V, and a beam current density of [missing information]. The etching depth is 150nm, and the depth accuracy is ensured by real-time monitoring of the etching rate (10nm / min), forming a periodic refractive index modulation structure.

[0086] In some possible implementations, the period of the Bragg grating 321 can be greater than or equal to 137.6 nanometers and less than or equal to 147.6 nanometers.

[0087] By controlling the period of the Bragg grating 321 to between 137.6 nm and 147.6 nm, it can be ensured that the Bragg wavelength of the Bragg grating 321 can be well matched with the gain peak of the indium gallium arsenide active region 310 near 970 nm, thereby enabling the semiconductor structure to achieve efficient single-mode operation under high gain conditions.

[0088] The period range of the Bragg grating 321 is a result of combining optical design and material properties. An excessively long period will cause a redshift in the Bragg wavelength, potentially deviating from the peak gain range of the active region 310 and reducing laser efficiency; an excessively short period will cause a blueshift in the Bragg wavelength, failing to effectively utilize the central region of the gain spectrum. Furthermore, the manufacturing precision of the Bragg grating 321, including the uniformity of its period, edge steepness, and sidewall morphology, also affects its spectral response characteristics, such as the width of the reflection spectrum and the sidelobe level, thereby influencing the side-mode suppression ratio and mode stability of the semiconductor structure.

[0089] And / or, the depth of the Bragg grating 321 can be greater than or equal to 100 nanometers and less than or equal to 200 nanometers.

[0090] The depth of the Bragg grating 321 can be used to tune its coupling coefficient. The coupling coefficient is an important physical quantity characterizing the feedback strength per unit length of the grating. The magnitude of the coupling coefficient directly determines the grating's reflection efficiency for a specific wavelength of light and the bandwidth of the reflection spectrum. Bragg gratings 321 with depths within this range can provide sufficiently strong distributed feedback, thereby effectively suppressing longitudinal mode oscillations other than the dominant mode, ensuring that the laser achieves single-longitudinal-mode operation with a high side-mode suppression ratio.

[0091] If the Bragg grating 321 is too shallow, the coupling coefficient will be insufficient, resulting in insufficient grating feedback strength and difficulty in effectively suppressing adjacent longitudinal modes, which may lead to multimode lasing or mode switching. If the Bragg grating 321 is too deep, the coupling coefficient will be too large. Although the reflection bandwidth will increase, it may lead to excessive localization of the optical field, introduce unnecessary scattering loss, and may damage the active region 310 or waveguide layer due to the etching process, thereby reducing the overall efficiency and reliability of the laser.

[0092] In some possible implementations, the width of the first waveguide layer 200 may be greater than or equal to 2 micrometers and less than or equal to 5 micrometers. The thickness of the first waveguide layer 200 may be greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

[0093] For example, the width of the first waveguide layer 200 can be 3 micrometers.

[0094] The width parameter of the first waveguide layer 200 can be used to achieve lateral confinement of the optical field and ensure that the laser operates in the fundamental transverse mode. The width range of the first waveguide layer 200 can balance the relationship between optical field confinement and modal stability. If the width is too narrow, the optical field confinement will be enhanced, but it may lead to increased optical loss and impose stringent requirements on the alignment accuracy of the fabrication process. It may also cause the current injection area to be too concentrated, affecting heat dissipation. If the width is too wide, the lateral optical field confinement will be weakened, which may lead to higher-order transverse mode lasing, resulting in a deterioration in the output beam quality and the appearance of a multi-lobed structure in the far-field spot. The width range of the first waveguide layer 200 can effectively support single transverse mode transmission, while providing reasonable process tolerances for electrode fabrication and current channel definition.

[0095] The thickness parameter of the first waveguide layer 200 works in conjunction with the second waveguide layer 400 to confine and distribute the optical field in the vertical direction. The thickness range of the first waveguide layer 200 affects the optical field mode size and the degree of overlap between the optical field and the active region 310. Too thin a layer causes the optical field to diffuse into the substrate 100, reducing the overlap with the active region 310, thereby decreasing the mode gain and increasing the laser's threshold current. Too thick a layer increases material growth time and cost, introduces additional internal stress, affects crystal quality, and an excessively large vertical dimension is detrimental to heat dissipation. The thickness range of the first waveguide layer 200 allows for achieving high mode gain and a good heat dissipation path while ensuring sufficient optical field confinement.

[0096] And / or, the width of the second waveguide layer 400 can be greater than or equal to 2 micrometers and less than or equal to 5 micrometers. The thickness of the second waveguide layer 400 can be greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

[0097] For example, the width of the second waveguide layer 400 can be 3 micrometers.

[0098] When the width of the second waveguide layer 400 is set to 2 to 5 micrometers, it helps to ensure the concentration and uniformity of current injection, and works in conjunction with the ridge structure formed by etching to achieve lateral confinement of the optical field and current.

[0099] The thickness parameter of the second waveguide layer 400 can be used to form a symmetrical or approximately symmetrical planar waveguide structure together with the first waveguide layer 200, the intermediate confinement layer, and the active region 310, to optimize the distribution of the optical field in the vertical direction. The thickness range of the second waveguide layer 400 can affect the confinement factor of the optical field, that is, the proportion of optical field energy distributed within the active region 310. Choosing an appropriate thickness can ensure that the optical field energy fully overlaps with the active region 310, thereby obtaining high modal gain, while avoiding the optical field from being too close to the p-type contact layer 50 or the metal electrode, which would introduce excessive optical absorption loss.

[0100] The coordinated design of the width and thickness of the second waveguide layer 400 and the first waveguide layer 200 jointly determines the overall characteristics of the laser waveguide. The dimensions of the second waveguide layer 400 and the first waveguide layer 200 can be the same or different depending on specific design requirements. For example, in one implementation, the upper and lower waveguide layers can use the same material and thickness to form a completely symmetrical waveguide structure, which is beneficial for obtaining symmetrical near-field beams and far-field divergence angles. In another implementation, due to electrode contact or bandgap engineering requirements, the thickness or aluminum composition of the upper and lower waveguide layers may be asymmetrically adjusted to optimize carrier injection efficiency or heat dissipation paths.

[0101] In some possible implementations, the length of the active region 310 in the direction of the connection between the input layer 320 and the output layer 330 can be greater than or equal to 0.8 mm and less than or equal to 1.5 mm.

[0102] The length of the active region 310 defines the physical cavity length of the laser resonator. The cavity length is the fundamental factor determining the longitudinal mode spacing of the laser, and the longitudinal mode spacing is inversely proportional to the cavity length. When the cavity length is between 0.8 mm and 1.5 mm, the corresponding longitudinal mode spacing is controlled within an appropriate range, ensuring that the longitudinal mode density is not too high, allowing the Bragg grating 321 integrated on the input side to effectively filter and stabilize a single longitudinal mode with its narrow-band reflection spectrum, suppressing competition between adjacent longitudinal modes; at the same time, it avoids the longitudinal mode spacing being too large due to an excessively short cavity length, resulting in too few longitudinal modes supported within the available gain bandwidth, thus affecting the output power.

[0103] For example, the active region 310 can be 1 mm long. A 1 mm long active region 310 has a longitudinal mode spacing of 0.8 nm at a wavelength of 970 nm, facilitating single-mode screening by the Bragg grating 321; the cavity surface can be formed by dry etching of aluminum gallium arsenide (AlGaAs) material using boron trichloride (BTC). ) / Chlorine ( Argon (Ar) / Nitrogen ( A mixed gas (volume ratio 6:5:3:2) under 15mTorr pressure, 800W coil power and 100W pressure plate power can achieve a sidewall roughness of 90%, providing narrowband reflection feedback to replace traditional cleavage surface reflectors.

[0104] In some possible implementations, a first electrode 10 and a second electrode 60 may also be included, and the first electrode 10 and the second electrode 60 may be configured as strip electrodes.

[0105] Setting the first electrode 10 and the second electrode 60 provides a channel for external power injection into the laser, thereby forming a forward bias voltage on the pn junction containing the active region 310, driving carrier injection and stimulated radiative recombination. Designing the first electrode 10 and the second electrode 60 as a strip structure confines the injected current laterally to a narrow region. The strip-shaped first electrode 10 and the second electrode 60 can be spatially aligned or associated with the underlying ridge waveguide structure, jointly forming a gain-guiding or refractive index-guiding mechanism. This ensures that the injected current is concentrated through a specific region of the active region 310, resulting in population inversion and providing optical gain in that region.

[0106] The first electrode 10 can be disposed on the surface of the substrate 100 away from the first waveguide layer 200, and the second electrode 60 can be disposed on the surface of the second waveguide layer 400 away from the substrate 100.

[0107] The first electrode 10 is located at the bottom of the substrate 100 and can form an ohmic contact with the n-type substrate 100, serving as a cathode. The second electrode 60 is located at the top of the semiconductor structure and forms an ohmic contact with the p-type contact layer 50, serving as an anode.

[0108] When preparing the first electrode 10, a multilayer metal of titanium (Ti) / platinum (Pt) / gold (Au) can be deposited on the bottom of the substrate 100 to form an ohmic contact.

[0109] When fabricating the second electrode 60, a strip pattern can be defined by photolithography above the contact layer 50, and nickel (Ni) / gold (Au) can be vapor-deposited to form a strip upper electrode to restrict current injection.

[0110] In summary, the semiconductor structure of this application embodiment may include, from bottom to top, a first electrode 10, a substrate 100, a buffer layer 20, a first confinement layer 30, a first waveguide layer 200, a resonant structure 300, a second waveguide layer 400, a second confinement layer 40, a contact layer 50, and a second electrode 60.

[0111] See Figure 5 This application provides a method for fabricating a semiconductor structure, comprising:

[0112] The first waveguide foundation, the active region foundation, and the second waveguide foundation are formed sequentially on the substrate;

[0113] Part of the first waveguide foundation, part of the active region, and part of the second waveguide foundation are removed to form a first waveguide layer, an active region, and a second waveguide layer; the first end face of the active region is perpendicular to the substrate, and the second end face of the active region is inclined.

[0114] An input layer and an output layer are formed, with the input layer located on the first end face of the active region and the output layer located on the second end face of the active region.

[0115] The method of sequentially forming the first waveguide foundation, the active region foundation, and the second waveguide foundation on the substrate can include using an n-type gallium arsenide (GaAs) substrate (thickness 300 μm, doping concentration...). After ultrasonic cleaning with organic reagents for 15 minutes, rinsing with deionized water and drying, the material was placed in the molecular beam epitaxy (MBE) chamber. The temperature was then maintained at 620℃, and the flow rate of trimethylaluminum (TMA) was adjusted to grow an aluminum gallium arsenide (AlGaAs) first waveguide base with an aluminum (Al) composition of 0.15 and a thickness of 1.5 μm. By adjusting the V / III group source flow rate ratio to 20:1, the refractive index difference of the material was controlled to reach 1.2%. Then, the active region base was grown using low-temperature growth technology. An indium gallium arsenide (InGaAs) quantum well was grown at 580℃ with an indium (In) composition of 0.18 and a thickness of 50 nm. The surface smoothness was monitored by real-time reflection high-energy electron diffraction (RHEED), and the roughness was <1 nm. The temperature was then raised back to 620℃ to grow an aluminum gallium arsenide (AlGaAs) second waveguide layer base with an aluminum (Al) composition of 0.15 and a thickness of 1.5 μm.

[0116] The method for removing a portion of the first waveguide foundation, a portion of the active region, and a portion of the second waveguide foundation to form the first waveguide layer, the active region, and the second waveguide layer may include using a Raith150 electron beam lithography machine to spin-coat photoresist (1 μm thick) on the surface, with an electron beam acceleration voltage of 50 kV and an exposure dose of [missing information]. The process involves defining a ridge waveguide and grating pattern, forming a photoresist mask through development (methyl isobutyl ketone: isopropanol = 1:3) and fixing processes, and then employing an etching system with boron trichloride as the etching gas. ) / Chlorine ( Argon (Ar) / Nitrogen ( (Flow ratio 6:5:3:2), chamber pressure 15mTorr, coil power 800W, pressure plate power 100W, etching time 5 minutes, forming an inverted trapezoidal FP cavity structure with a tilt angle of 3 degrees and a ridge waveguide with a width of 3μm, etching rate controlled at 300nm / min, sidewall verticality deviation <1 degree.

[0117] Methods for forming the input and output layers may include forming the input layer using electron beam evaporation technology, followed by the sequential deposition of alumina (… (thickness 80nm) and silicon dioxide ( (Thickness 120nm), forming a λ / 4 multilayer film system with a reflectivity <0.1% and transmittance >99.5% at a wavelength of 970nm; deposited titanium dioxide ( (thickness 150nm) and silicon dioxide ( (90nm thick) to form a quarter-wavelength stacked output layer with reflectivity >95%, optimizing the intracavity light field distribution.

[0118] In some possible implementations, including:

[0119] A Bragg grating is formed on the first end face of the active region, and the Bragg grating extends toward the second end face of the active region;

[0120] An input layer is formed, with the first part of the input layer covering the first end face of the active region and the second part of the input layer covering the Bragg grating.

[0121] The method for forming a Bragg grating may include first defining a grating pattern on the semiconductor surface using secondary electron beam lithography, and then optimizing the exposure dose to... A grating stripe with a period of 142.6 nm is defined on the left side with a duty cycle of 0.5. Excess photoresist is removed using a lift-off process to form a metal (chromium Cr / gold Au) mask. Then, an ion beam etching machine is used with argon (Ar) as the etching gas, an accelerating voltage of 1000V, and a beam current density of [missing information]. The etching depth is 150nm, and the depth accuracy is ensured by real-time monitoring of the etching rate (10nm / min), forming a periodic refractive index modulation structure.

[0122] This application provides a semiconductor laser, including the semiconductor structure of any of the above embodiments.

[0123] Since the semiconductor laser includes the semiconductor structure of any of the above embodiments, the advantages of the semiconductor laser including the semiconductor structure of any of the above embodiments can be found in the relevant description above, and will not be repeated here.

[0124] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0125] In the description of this invention, it should be understood that the terms “comprising” and “having” as used herein, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0126] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can be a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A semiconductor structure, characterized in that, Suitable for FP cavity lasers, including a substrate, a first waveguide layer, a resonant structure, and a second waveguide layer; The first waveguide layer is disposed on the surface of the substrate along the thickness direction; The resonant structure includes an active region, an input layer, and an output layer, wherein the active region, the input layer, and the output layer are disposed on the side of the first waveguide layer away from the substrate; In a plane parallel to the substrate, the input layer and the output layer are located on opposite sides of the active region, and the output layer is inclined and is located away from the input layer in a direction away from the substrate. The second waveguide layer is disposed on the surface of the resonant structure away from the first waveguide layer, and the second waveguide layer is connected to the resonant structure; The angle between the output layer and the substrate in the thickness direction is greater than or equal to 2 degrees and less than or equal to 6 degrees.

2. The semiconductor structure according to claim 1, characterized in that, The angle between the output layer and the substrate in the thickness direction is greater than or equal to 2.8 degrees and less than or equal to 3.2 degrees.

3. The semiconductor structure according to claim 1, characterized in that, The output layer is configured as a multilayer output layer, wherein the reflectivity of the multilayer output layer at a wavelength of 970 nm is less than 0.1%, and the transmittance of the multilayer output layer at a wavelength of 970 nm is greater than 99.5%. And / or, the input layer is configured as a quarter-wavelength stacked structure, and the reflectivity of the input layer is greater than 90%.

4. The semiconductor structure according to any one of claims 1-3, characterized in that, The input layer is provided with a Bragg grating that extends toward the output layer, and at least a portion of the Bragg grating is located within the active region.

5. The semiconductor structure according to claim 4, characterized in that, The period of the Bragg grating is greater than or equal to 137.6 nanometers and less than or equal to 147.6 nanometers. And / or, the depth of the Bragg grating is greater than or equal to 100 nanometers and less than or equal to 200 nanometers.

6. The semiconductor structure according to claim 1, characterized in that, The width of the first waveguide layer is greater than or equal to 2 micrometers and less than or equal to 5 micrometers; the thickness of the first waveguide layer is greater than or equal to 1 micrometer and less than or equal to 2 micrometers. And / or, the width of the second waveguide layer is greater than or equal to 2 micrometers and less than or equal to 5 micrometers; the thickness of the second waveguide layer is greater than or equal to 1 micrometer and less than or equal to 2 micrometers.

7. The semiconductor structure according to claim 1, characterized in that, In the direction of the line connecting the input layer and the output layer, the length of the active region is greater than or equal to 0.8 mm and less than or equal to 1.5 mm.

8. The semiconductor structure according to claim 1, characterized in that, It also includes a first electrode and a second electrode, wherein the first electrode and the second electrode are configured as strip electrodes; The first electrode is disposed on the surface of the substrate away from the first waveguide layer, and the second electrode is disposed on the surface of the second waveguide layer away from the substrate.

9. A method for fabricating a semiconductor structure, characterized in that, The method for preparing the semiconductor structure as described in any one of claims 1-8 includes: The first waveguide foundation, the active region foundation, and the second waveguide foundation are formed sequentially on the substrate; A portion of the first waveguide foundation, a portion of the active region, and a portion of the second waveguide foundation are removed to form a first waveguide layer, an active region, and a second waveguide layer; the first end face of the active region is perpendicular to the substrate, and the second end face of the active region is inclined. An input layer and an output layer are formed, wherein the input layer is located on the first end face of the active region, and the output layer is located on the second end face of the active region. The angle between the output layer and the thickness direction of the substrate is greater than or equal to 2 degrees and less than or equal to 6 degrees.

10. The method for preparing a semiconductor structure according to claim 9, characterized in that, include: A Bragg grating is formed on the first end face of the active region, and the Bragg grating extends toward the second end face of the active region; The input layer is formed, with a first portion covering the first end face of the active region and a second portion covering the Bragg grating.

11. A semiconductor laser, characterized in that, Including the semiconductor structure as described in any one of claims 1-8.

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