Epitaxial growth method for high-speed optoelectronic devices

Abstract

The invention provides an epitaxial growth method for a high-speed photoelectric device, which integrates material epitaxial growth, performance characterization and device design in a closed-loop feedback system, and generates a design scheme of a laser electrode and a waveguide structure by using electrical and optical performance actual measurement parameters of an actual epitaxial structure. And technological parameters of epitaxial growth are adjusted according to feedback, so that high collaboration of material growth and device design is realized. The method can effectively overcome the adverse effect of material growth deviation on the performance of the device, remarkably improves the performance consistency, reliability and comprehensive performance indexes of the prepared high-speed photoelectric device, and provides an effective way for realizing controllable and accurate manufacturing of the high-performance photoelectric device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device manufacturing technology, and in particular to an epitaxial growth method for high-speed optoelectronic devices. Background Technology

[0002] Semiconductor optoelectronic devices, such as lasers, are core components of modern optical communication, data storage, and sensing systems. Their performance largely depends on the quality and precision of the epitaxial material structure that constitutes the device. Epitaxial growth techniques, such as metal-organic chemical vapor deposition and molecular beam epitaxy, are key processes for fabricating such multilayer epitaxial structures.

[0003] In existing technologies, a single epitaxial growth technique is typically used to fabricate the entire epitaxial structure. Even when different epitaxial techniques are combined, the material growth process and subsequent device structure design are often two relatively independent steps. After material growth, device design is based on a pre-set, idealized model, without fully considering the specific electrical and optical properties of the actual grown material structure. This disconnect between material fabrication and device design has a significant drawback: due to the unavoidable deviation between the performance parameters of the actual epitaxial material and the ideal design, the final optoelectronic device manufactured based on a fixed design model cannot achieve optimal performance, such as response speed and optical mode characteristics. Furthermore, the performance consistency between different batches of devices is poor, making it impossible to achieve accurate prediction and controllable manufacturing of device performance. Summary of the Invention

[0004] In view of this, the present invention provides an epitaxial growth method for high-speed optoelectronic devices to overcome the technical defects existing in the prior art.

[0005] This invention provides an epitaxial growth method for high-speed optoelectronic devices, comprising: Provide a substrate and perform pretreatment on the substrate; A buffer layer and a cladding layer were sequentially grown on a pretreated substrate using a metal-organic chemical vapor deposition process. An active layer is grown on a buffer layer using molecular beam epitaxy to form an epitaxial structure. The performance of the epitaxial structure was characterized to obtain measured electrical and optical performance parameters. Based on the measured electrical and optical performance parameters, a design scheme including the laser electrode structure and the laser waveguide structure is generated. The design scheme includes a set of device design parameters. Based on the device design parameters, the growth parameters of the metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) processes are adjusted, and a new round of epitaxial growth is performed based on the adjusted growth parameters.

[0006] In some embodiments, the pretreatment step on the substrate includes growing a low-temperature pre-growth layer, the material of which is aluminum arsenide.

[0007] In some embodiments, in the step of growing the active layer using molecular beam epitaxy, the growth temperature is controlled in a first temperature range; in the step of growing the buffer layer and cladding layer using metal-organic chemical vapor deposition, the growth temperature is controlled in a second temperature range higher than the first temperature range.

[0008] In some implementations, the steps for characterizing the performance of the epitaxial structure include: The carrier concentration and mobility of the epitaxial structure were measured using the Hall effect test method to obtain the measured parameters of its electrical performance. The refractive index and extinction coefficient of the epitaxial structure were measured using the spectral ellipsometry to obtain the measured parameters of its optical performance.

[0009] In some implementations, when generating the design scheme of the laser electrode structure, the design value of the parasitic capacitance of the laser electrode structure is determined by the following first calculation formula:

[0010] in, Indicates the design value of parasitic capacitance; Represents the vacuum permittivity; The design value of the overlap area between the laser electrode structure and the cladding is represented, which is determined based on the target spot size; M represents the total number of dielectric layers between the laser electrode structure and the active layer. This represents the design thickness value of the m-th dielectric layer, which is set based on the measured thickness of the epitaxial structure. The relative permittivity of the m-th dielectric layer is obtained by querying the measured optical performance parameters obtained from characterization; N represents the total number of conductive paths constituting the laser electrode structure. This represents the designed length of the nth conductive path; This represents the designed width of the nth conductive path; This represents the conductivity of the material used in the nth conductive path; This represents the characteristic impedance of the system.

[0011] In some implementations, the design value for the overlap area is determined by the following second calculation formula:

[0012] in, This represents the design value for the overlap area; P represents the number of main emission peaks displayed by the active layer during measurement. The wavelength of the p-th emission peak is the measured value, provided by the measured optical performance parameters obtained from the characterization. This represents the measured effective refractive index of the waveguide at the p-th emission peak, provided by the measured optical performance parameters obtained through characterization. Represents the mode overlap integral coefficients related to the laser waveguide structure; This represents the gain normalization constant, and its dimension is cubic meters; to This indicates the energy range of the gain spectrum of the active layer; dE represents the joint density of states function of the active layer, calculated from the measured parameters of the optical performance obtained through characterization; dE is the differential of energy E, and the integral sign ∫ denotes the relationship between dE and the joint density of states function. Integrating over energy E is used to calculate the total density of states within a specific energy window; represents the measured value of the differential gain coefficient of the active layer, provided by the measured optical performance parameters obtained from characterization; e represents the base of the natural logarithm.

[0013] In some implementations, the step of adjusting growth parameters includes: Adjust the growth temperature and precursor beam intensity of the molecular beam epitaxy process according to the device design parameters.

[0014] In some implementations, the feedback adjustment of growth parameters also includes in-situ doping control, which controls the doping concentration and uniformity by adjusting the flow rate of the doping source gas.

[0015] In some implementations, the in-situ doping control step employs a closed-loop feedback mechanism and utilizes real-time monitoring data from secondary ion mass spectrometry to adjust the flow rate of the dopant source gas.

[0016] In some implementations, the laser waveguide structure is designed to confine heterogeneous structures separately.

[0017] At least one embodiment of this invention integrates material epitaxial growth, performance characterization, and device design into a closed-loop feedback system. It utilizes measured electrical and optical performance parameters of the actual epitaxial structure to generate design schemes for laser electrodes and waveguide structures, and adjusts the epitaxial growth process parameters accordingly, achieving a high degree of synergy between material growth and device design. This method effectively overcomes the adverse effects of material growth deviations on device performance, significantly improving the performance consistency, reliability, and overall performance indicators of the fabricated high-speed optoelectronic devices, providing an effective approach for the controllable and precise manufacturing of high-performance optoelectronic devices. Attached Figure Description

[0018] Figure 1 This is a flowchart of an epitaxial growth method for high-speed optoelectronic devices provided by the present invention. Detailed Implementation

[0019] Many specific details are set forth in the following description to provide a full understanding of this specification. However, this specification can be implemented in many other ways than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this specification. Therefore, this specification is not limited to the specific implementations disclosed below.

[0020] The terminology used in one or more embodiments of this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the one or more embodiments of this specification. The singular forms “a” and “the” as used in one or more embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in one or more embodiments of this specification refers to and includes any or all possible combinations of one or more associated listed items. The modifications “a” and “a plurality” as used in this disclosure are illustrative and not restrictive, and those skilled in the art will understand that they should be understood as “one or more” unless the context clearly indicates otherwise.

[0021] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this specification, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this specification, and similarly, second may also be referred to as first. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0022] See Figure 1 , Figure 1 A flowchart of an epitaxial growth method for high-speed optoelectronic devices according to some embodiments of this specification is shown, specifically including the following steps: A substrate is provided and pretreatment is performed on it. A buffer layer and a cladding layer are sequentially grown on the pretreated substrate using metal-organic chemical vapor deposition (MOCVD). An active layer is grown on the buffer layer using molecular beam epitaxy (MBE), forming an epitaxial structure. The epitaxial structure is characterized to obtain measured electrical and optical performance parameters. Based on these parameters, a design scheme including laser electrode and waveguide structures is generated, incorporating a set of device design parameters. The growth parameters of both MOCVD and MBE are adjusted according to the device design parameters, and a new round of epitaxial growth is performed based on the adjusted parameters.

[0023] Pretreatment refers to preparatory steps performed on the substrate surface before the formal growth of functional layers. Examples include high-temperature thermal cleaning to remove oxides and contaminants, ensuring a high-quality growth interface for subsequent epitaxial layers. Metal-organic chemical vapor deposition (MOCVD) is an epitaxial technology that uses a metal-organic compound source and hydride gas to chemically react on a heated substrate surface to deposit semiconductor thin films. For instance, controlling the flow rate and partial pressure of precursors such as trimethylgallium (TMG) and trimethylaluminum (MAA) in a reaction chamber to grow III-V compound thin layers allows for the deposition of large-area, uniform binary or ternary semiconductor alloys. A buffer layer refers to a transitional semiconductor layer grown between the substrate and the active structure to improve material quality. For example, growing a thicker layer of gallium arsenide (GaAs) or indium gallium arsenide (IGaAs) via MOCVD can alleviate lattice mismatch and reduce dislocation density between the substrate and the epitaxial layer. A cladding layer refers to a semiconductor layer located on either side of the active layer with a wide bandgap to confine carriers and the optical field. For example, an aluminum gallium arsenide (AlGaAs) layer with a high aluminum content can effectively confine carriers and photons within the active region.

[0024] Molecular beam epitaxy (MBE) refers to a technique that uses a molecular beam of constituent elements directly sprayed onto a heated substrate in an ultra-high vacuum environment for epitaxial growth. For example, by precisely controlling the shutter opening and closing and intensity of the beam source for elements such as indium, gallium, and arsenic, atomic-level precision thin-layer growth and heterojunction interface control can be achieved. An active layer refers to the core functional semiconductor layer in the epitaxial structure responsible for light emission or absorption. For example, an indium gallium arsenide phosphide (IGaAs) multi-quantum-well structure can be used to generate stimulated emission of light when a bias voltage is applied. An epitaxial structure can refer to a stacked structure containing multiple functional semiconductor thin layers formed on a substrate through epitaxial growth techniques. For example, a complete layered material system consisting of a buffer layer, cladding layer, and active layer can serve as the core chip of optoelectronic devices.

[0025] Performance characterization refers to the process of measuring and analyzing the physical, electrical, and optical properties of epitaxial structures. For example, parameters such as carrier concentration and refractive index can be obtained through Hall effect testing and spectral ellipsometry, respectively, enabling quantitative assessment of the quality of epitaxial materials and providing data support for device design. Measured electrical performance parameters refer to the set of physical quantities describing the conductivity of epitaxial materials, obtained directly through electrical measurement methods. These include key parameters such as carrier concentration and carrier mobility, and can be used to evaluate the material's conductivity and impurity concentration. Measured optical performance parameters refer to the set of physical quantities describing the interaction characteristics between epitaxial materials and light, obtained directly through optical measurement methods. These include refractive index, extinction coefficient, and emission wavelength, and can be used to analyze the material's optical waveguide and gain characteristics.

[0026] Laser electrode structure refers to the physical structure of the metal conductors fabricated on the laser chip for injecting operating current and forming ohmic contacts. Examples include titanium / platinum / gold multilayer metal film systems formed through photolithography and evaporation processes. Their geometry and layout directly affect current injection efficiency, series resistance, and high-frequency parasitic parameters. Laser waveguide structure refers to the distribution of dielectric materials within the laser designed to generate and maintain laser oscillation, confining and guiding the propagation of light waves. Examples include planar or ridge-shaped dielectric waveguides composed of semiconductor layers with different refractive indices (such as indium gallium arsenide phosphide active layers and indium phosphide cladding), used to provide the optical field confinement and resonant feedback conditions required for optical gain. A design scheme including laser electrode and waveguide structures can refer to a complete set of technical documents or parameters defining the physical characteristics and spatial relationships of the core laser components. For example, detailed specifications generated by computer-aided design software, including electrode geometry, waveguide layer thickness and width, and their relative positions, are used to guide subsequent chip manufacturing processes and ensure that device performance meets preset targets. Device design parameters refer to a set of quantifiable variables used in laser design to specifically define the physical characteristics of components such as electrodes and waveguides. These parameters include key dimensional parameters such as electrode overlap area, waveguide layer thickness and width, and can serve as a bridge connecting material properties and final device performance.

[0027] Growth parameters refer to the set of controllable process variables that directly affect the quality and properties of thin film growth in epitaxial growth processes. These include growth temperature, reaction chamber pressure, precursor flow ratio, and growth rate. Adjusting these parameters through feedback can optimize the material properties of subsequent epitaxial layers.

[0028] As a specific example, this invention is implemented on an indium phosphide substrate. First, the substrate is pretreated, including high-temperature annealing in a hydrogen atmosphere. Then, using metal-organic chemical vapor deposition (MOCVD), an iron-doped indium phosphide buffer layer is grown on the pretreated substrate at a growth temperature controlled at approximately 650°C; followed by the growth of a silicon-doped indium phosphide lower cladding layer. The sample is then transferred to a molecular beam epitaxy (MBE) apparatus, where an active layer consisting of multiple indium gallium arsenide phosphide quantum wells and an indium phosphide barrier layer is grown at a growth temperature of approximately 500°C. After growth, the epitaxial structure is characterized: its N-type carrier concentration and electron mobility are measured using a Hall effect meter; and its refractive index and extinction coefficient near the 1550 nm communication band are measured using a spectroellipsometer. Based on these measured parameters, the upper limit of the electrode parasitic capacitance required to achieve the target bandwidth is calculated, thereby generating a laser electrode structure scheme with a specific overlap area, and waveguide size schemes that respectively constrain the heterostructure. Finally, based on these device design parameters, the indium beam intensity during MBE growth of the active layer and the silane doping gas flow rate during MOCVD growth of the cladding are adjusted. A new round of epitaxial growth is then performed based on these adjusted parameters in order to obtain an epitaxial wafer that better matches the requirements of a high-performance laser.

[0029] The beneficial effects of one of the embodiments in this specification include at least the following: by integrating material epitaxial growth, performance characterization, and device design into a closed-loop feedback system, the design schemes for laser electrodes and waveguide structures are generated using measured electrical and optical performance parameters of the actual epitaxial structure, and the epitaxial growth process parameters are adjusted accordingly, achieving a high degree of synergy between material growth and device design. This method can effectively overcome the adverse effects of material growth deviations on device performance, significantly improve the performance consistency, reliability, and overall performance indicators of the fabricated high-speed optoelectronic devices, and provide an effective way to achieve controllable and precise manufacturing of high-performance optoelectronic devices.

[0030] In some embodiments, the pretreatment step on the substrate includes growing a low-temperature pre-growth layer, the material of which is aluminum arsenide.

[0031] Low-temperature pre-growth layers refer to the step of depositing a thin layer of semiconductor material as an initial layer at a relatively low substrate temperature, such as around 300 to 400 degrees Celsius, which is much lower than the growth temperature of subsequent buffer layers. This allows for the formation of a smooth nucleation interface before formal growth, improving crystal quality. Aluminum arsenide refers to a group III-V semiconductor material formed by the combination of aluminum and arsenic, typically represented by the chemical formula AlAs. For example, it can be obtained by reacting trimethylaluminum and arsine as precursors at low temperatures using MOCVD. This provides specific lattice constants and wide bandgap characteristics, which are beneficial for the growth of subsequent layers.

[0032] As a concrete example: after providing the indium phosphide substrate, a pretreatment step is performed. The key to this pretreatment is the growth of a low-temperature pre-growth layer. Specifically, the substrate is placed in an MOCVD reaction chamber, and the temperature is lowered to approximately 380 degrees Celsius. Subsequently, trimethylaluminum and arsine are introduced as reaction sources to grow an aluminum arsenide layer with a thickness of approximately 20 nanometers on the substrate. This AlAs low-temperature pre-growth layer helps to cover any minor defects that may exist on the substrate surface and provides a better nucleation surface for the subsequent buffer layer grown at higher temperatures, thereby suppressing the propagation of through dislocations and improving the overall crystal quality of the epitaxial structure. This step is fundamental to the subsequent growth of the buffer layer, cladding layer, and active layer via MBE.

[0033] By introducing a low-temperature pre-growth layer of specific materials in the pretreatment process, this invention can effectively improve the substrate surface condition, provide a better crystal template for the subsequent epitaxial growth of key functional layers, thereby reducing the defect density of the epitaxial structure and improving the reliability and performance consistency of the final optoelectronic device.

[0034] In some embodiments, in the step of growing the active layer using molecular beam epitaxy, the growth temperature is controlled in a first temperature range; in the step of growing the buffer layer and cladding layer using metal-organic chemical vapor deposition, the growth temperature is controlled in a second temperature range higher than the first temperature range.

[0035] Controlling the growth temperature in the first temperature range can refer to heating the substrate and maintaining it within a specific low temperature range during the molecular beam epitaxy (MBE) growth of the active layer, such as between 400°C and 500°C. This protects the temperature-sensitive active region material composition and interface quality, and prevents the re-evaporation of volatile elements such as In. Controlling the growth temperature in the second temperature range, which is higher than the first temperature range, can refer to using a higher substrate temperature range during the metal-organic chemical vapor deposition (MOCVD) growth of buffer layers and cladding layers, such as between 600°C and 700°C. This promotes the complete decomposition and surface migration of the precursor, resulting in thicker layers with better crystallinity.

[0036] As a concrete example: when growing the active layer, molecular beam epitaxy is used, and the growth temperature is controlled within a relatively low first temperature range, such as 480 degrees Celsius. This temperature is beneficial for precisely controlling the interface steepness and compositional uniformity of the indium gallium arsenide phosphide (IGaAs) multi-quantum well. In contrast, when growing the buffer layer and cladding layer using metal-organic chemical vapor deposition (MOCVD), the growth temperature is controlled within a relatively high second temperature range, such as 650 degrees Celsius. The higher temperature is beneficial for obtaining a high-quality AlGaAs cladding layer with fewer defects and more uniform doping. This differentiated temperature control strategy allows the temperature-sensitive active layer to grow under optimized conditions while ensuring that the buffer layer and cladding layer possess excellent bulk material properties.

[0037] By setting different optimized temperature ranges for the active layer grown by molecular beam epitaxy and the buffer layer and cladding layer grown by metal-organic chemical vapor deposition, this invention enables both the temperature-sensitive active region material and the cladding material requiring high-temperature optimization to grow under their respective optimal thermodynamic conditions, thereby taking into account both interface quality and bulk material properties as a whole and improving the overall performance of the epitaxial structure.

[0038] In some embodiments, the steps for characterizing the performance of the epitaxial structure include: measuring the carrier concentration and mobility of the epitaxial structure using the Hall effect test method to obtain measured electrical performance parameters; and measuring the refractive index and extinction coefficient of the epitaxial structure using the spectral ellipsometric method to obtain measured optical performance parameters.

[0039] Hall effect measurement is a standard method for electrical characterization using the Hall effect principle. For example, by fabricating van der Berg electrode configurations on an epitaxial structure and applying a magnetic field perpendicular to the sample surface, the resulting Hall voltage can be measured. This allows for the calculation of key electrical parameters such as carrier type, concentration, and mobility. Carrier concentration in an epitaxial structure refers to the number of free charge carriers per unit volume of epitaxial material. For example, the electron or hole concentration calculated through Hall effect testing directly reflects the material's doping level and conductivity. Mobility refers to the average drift velocity of carriers under a unit electric field, characterizing the ease with which carriers move within a semiconductor. For example, it can be calculated by combining the conductivity measured in Hall effect testing with carrier concentration. High mobility implies low scattering probability and excellent crystal quality. Spectroscopic ellipsometry is a non-destructive optical measurement technique that uses polarized light to illuminate a sample at different incident angles and analyzes the changes in the polarization state of the reflected light. By fitting the amplitude ratio Ψ and phase difference Δ as a function of wavelength, the optical constants and thickness of a thin film can be accurately obtained. The refractive index of an epitaxial structure refers to the ratio of the speed of light in a semiconductor material to its speed in a vacuum, characterizing the material's ability to bend light. For example, the real part of the complex refractive index at different wavelengths, obtained by fitting spectral ellipsometry data, is a key optical parameter for designing optical waveguides and laser resonators. The extinction coefficient, referring to the imaginary part of the complex refractive index, characterizes the degree of light attenuation during propagation in a material. For example, it is obtained by fitting spectral ellipsometry measurements; its value is directly related to the material's absorption coefficient and reflects the intrinsic absorption and free carrier absorption characteristics of the active region. Measured optical performance parameters can refer to the target outputs of optical characterization steps, such as the set of curves showing the refractive index and extinction coefficient as a function of wavelength obtained by measuring and fitting the spectral ellipsometry. These parameters are crucial for accurately simulating optical field modes and calculating waveguide confinement factors.

[0040] As a concrete example, after epitaxial growth is completed, the performance of the epitaxial structure is characterized. First, measurements are performed using the Hall effect method: an indium-point ohmic electrode is fabricated at the edge of the sample and placed in a constant magnetic field generated by an electromagnet. The Hall voltage and longitudinal voltage are measured under different current and magnetic field directions. The carrier concentration (e.g., n-type, concentration of 2e18 cm^-3) and mobility (e.g., 800 cm^2 / V·s) of the epitaxial structure are calculated, thus obtaining the measured electrical performance parameters. Next, measurements are performed using spectral ellipsometric analysis: using a spectral ellipsometer, the change in polarization state of light after reflection from the sample surface is measured at multiple incident angles in the wavelength range of 250 nm to 1700 nm. The refractive index (e.g., 3.4) and extinction coefficient (e.g., 0.01) of the epitaxial structure in the target wavelength range (e.g., near 1550 nm) are obtained through modeling and fitting, thus obtaining the measured optical performance parameters. These two sets of measured parameters together provide crucial input for subsequent laser design.

[0041] By combining the Hall effect test method and the spectral ellipsometry, two complementary characterization methods, this invention can systematically and accurately obtain the core measured parameters of epitaxial materials in terms of electrical conduction and optical properties. This provides a reliable data foundation for subsequent laser electrode and waveguide design that is highly matched with the actual performance of the materials, thereby effectively improving the accuracy of device performance prediction and the performance consistency of the final product.

[0042] In some implementations, when generating the design scheme of the laser electrode structure, the design value of the parasitic capacitance of the laser electrode structure is determined by the following first calculation formula:

[0043] in, Indicates the design value of parasitic capacitance; Represents the vacuum permittivity; The design value of the overlap area between the laser electrode structure and the cladding is represented, which is determined based on the target spot size; M represents the total number of dielectric layers between the laser electrode structure and the active layer. This represents the design thickness value of the m-th dielectric layer, which is set based on the measured thickness of the epitaxial structure. The relative permittivity of the m-th dielectric layer is obtained by querying the measured optical performance parameters obtained from characterization; N represents the total number of conductive paths constituting the laser electrode structure. This represents the designed length of the nth conductive path; This represents the designed width of the nth conductive path; This represents the conductivity of the material used in the nth conductive path; This represents the characteristic impedance of the system.

[0044] The parasitic capacitance design value of a laser electrode structure refers to the target value of an undesirable capacitance parameter introduced by the electrode structure itself in the laser's equivalent circuit model. For example, it might be a pre-set upper limit for capacitance through electromagnetic simulation or analytical models, and its magnitude directly affects the high-speed modulation bandwidth of the device. The vacuum dielectric constant refers to a physical constant characterizing the ratio of electric displacement field to electric field strength under vacuum conditions, with a value of approximately 8.854 × 10⁻¹² F / m. For example, it is introduced as a fundamental constant in this calculation to connect capacitance calculations in the International System of Units (SI). The overlap area design value refers to the target size of the area where the metal electrode and the underlying semiconductor cladding overlap in the vertical projection direction of the laser structure. For example, it might be an optimized area value calculated by back-calculating based on spot size and mode constraints, and it directly affects parasitic capacitance and current spread. The target spot size refers to the preset spot size for the laser output beam. The total number of dielectric layers between the laser electrode structure and the active layer can refer to the number of all insulating or semiconductor spacers between the electrode metal and the active region. These layers may include cladding layers, barrier layers, etc. The total number of layers M affects the electric field distribution and the total capacitance. The design thickness of the m-th dielectric layer can refer to the preset vertical dimension of the m-th dielectric material between the electrode and the active layer. For example, a target value can be set based on the measured thickness data of each layer after epitaxial growth. This value is a key parameter for calculating the capacitance of the layered structure. The relative permittivity of the m-th dielectric layer can refer to the ratio of the permittivity of the m-th dielectric material to the vacuum permittivity, characterizing its polarization ability and charge storage capacity. For example, it can be obtained by looking up the optical constant (refractive index n) measured by spectral ellipsometry and calculating it using the relationship ε_r ≈ n^2. The measured optical performance parameters can refer to the direct acquisition or calculation of the required dielectric constant value from a database of optical parameters previously measured by spectral ellipsometry or other methods. For example, the relative permittivity of each layer at the operating wavelength can be derived using measured refractive index data. The total number of conductive paths constituting the laser electrode structure can refer to the number of all independent metal lines or regions used for conducting current in the laser electrode layout, such as main injection strips, connecting arms, and pads. This total number, N, affects the current distribution and parasitic resistance. The design length of the nth conductive path can refer to the preset dimension of the nth conductive path in the main current flow direction, such as the metal strip length determined based on the laser cavity length and electrode layout planning. This value affects the series resistance of the path. The design width of the nth conductive path can refer to the preset dimension of the nth conductive path perpendicular to the current flow direction, such as the metal strip width set according to processing limits and current carrying capacity. This value affects the current density and path resistance. The conductivity of the material used in the nth conductive path can refer to the physical parameter of the current-conducting ability of the metal material constituting the nth conductive path (such as gold, titanium-platinum systems), for example, using the standard conductivity value of bulk materials (such as the conductivity of gold being 4.1 × 10^7 S / m) as input.System characteristic impedance refers to the target value of the characteristic impedance presented by the transmission line or electrode structure in high-speed circuit design. For example, it is usually designed to be 50 ohms to achieve impedance matching with external test systems and drive circuits and minimize signal reflection.

[0045] By employing a dedicated calculation formula that comprehensively considers electrode geometry, multilayer dielectric material properties, and conductive path resistance effects to determine the parasitic capacitance design value of laser electrodes, this invention enables electrode design to accurately match measured material parameters and system high-frequency requirements, thereby effectively optimizing the high-speed response characteristics of the laser and improving modulation bandwidth.

[0046] In some implementations, the design value for the overlap area is determined by the following second calculation formula:

[0047] in, This represents the design value for the overlap area; P represents the number of main emission peaks displayed by the active layer during measurement. The wavelength of the p-th emission peak is the measured value, provided by the measured optical performance parameters obtained from the characterization. This represents the measured effective refractive index of the waveguide at the p-th emission peak, provided by the measured optical performance parameters obtained through characterization. Represents the mode overlap integral coefficients related to the laser waveguide structure; This represents the gain normalization constant, and its dimension is cubic meters; to This indicates the energy range of the gain spectrum of the active layer; dE represents the joint density of states function of the active layer, calculated from the measured parameters of the optical performance obtained through characterization; dE is the differential of energy E, and the integral sign ∫ denotes the relationship between dE and the joint density of states function. Integrating over energy E is used to calculate the total density of states within a specific energy window; represents the measured value of the differential gain coefficient of the active layer, provided by the measured optical performance parameters obtained from characterization; e represents the base of the natural logarithm.

[0048] The number of major emission peaks displayed by the active layer in the measurement can refer to the number of emission peaks with significantly prominent intensity within the gain spectrum observed through photoluminescence or electroluminescence spectroscopy. For example, for a multi-quantum-well active layer, this may correspond to radiative recombination processes between different sub-bands. The measured wavelength of the p-th emission peak can refer to the center wavelength value corresponding to the p-th major emission peak directly read by a spectral measurement device, such as the wavelength position corresponding to the peak in a spectral curve acquired by a monochromator and detector system. The measured optical performance parameters can refer to the wavelength data obtained from the raw or processed data set obtained by performing optical performance (such as photoluminescence spectroscopy) on the completed epitaxial structure as described in the preceding claims. The measured effective refractive index of the waveguide at the p-th emission peak can refer to the equivalent refractive index measurement value corresponding to the wavelength of the p-th emission peak when the light wave propagates along the propagation direction in the laser waveguide structure. This value comprehensively reflects the ability of the waveguide material and geometry to constrain the light field. The mode overlap integral coefficient associated with the laser waveguide structure can be a dimensionless parameter used to quantify the spatial overlap between the optical mode field intensity distribution and the active layer gain region. Its value is between 0 and 1, ideally close to 1. The gain normalization constant can be a constant coefficient used to normalize the gain expression in a theoretical model or to have a specific dimension; its specific value depends on the gain model and unit system used. The gain spectrum energy range of the active layer can refer to the photon energy range in which the active layer material can provide optical gain, typically corresponding to a specific energy window in the photoluminescence or absorption spectrum, such as the energy near the transition from the first electron level to the first hole level. The joint density of states function of the active layer can be a function describing the joint distribution of electron and hole state densities at a given energy in a semiconductor band structure; this function determines the basic shape and width of the active layer gain spectrum. The measured value of the differential gain coefficient of the active layer can refer to the rate of change of the optical gain of the active layer material relative to the carrier concentration, i.e., dg / dN, a key parameter directly reflecting the laser's threshold characteristics and modulation response speed. The base of the natural logarithm can refer to an irrational constant widely used in mathematics and natural sciences, with a value of approximately 2.71828, which forms the basis of the natural logarithm function.

[0049] By employing a dedicated computational model that deeply integrates multiple core optical measurement parameters of the active layer (such as emission wavelength, effective refractive index, joint density of states, and differential gain) to determine the electrode overlap area, this invention enables the electrode geometry design to be precisely adapted to the actual optical gain characteristics and waveguide mode characteristics of the active region, thereby optimizing high-frequency electrical performance while ensuring effective utilization of the optical field.

[0050] In some implementations, the step of adjusting growth parameters includes adjusting the growth temperature and precursor beam intensity of the molecular beam epitaxy process based on device design parameters.

[0051] Adjusting the growth temperature in the molecular beam epitaxy (MBE) process can refer to changing the set temperature of the substrate heater in the MBE system to control the surface reaction kinetics during epitaxy. For example, by fine-tuning the growth temperature by tens of degrees Celsius within the allowable range according to the design requirements for the active layer quality, the interface quality and compositional uniformity of the quantum well can be optimized. The precursor beam intensity refers to the flux of atomic or molecular beams escaping from each jet source furnace and reaching the substrate during MBE. For example, by adjusting the temperature of the source furnace to precisely control the beam intensity of elements such as gallium, indium, and aluminum, the growth rate and chemical composition of the epitaxial layer can be directly determined.

[0052] As a concrete example: after obtaining the device design parameters for the laser electrodes and waveguide structure, a feedback adjustment step is performed to adjust the growth parameters. Specifically for molecular beam epitaxy (MBE), the growth temperature is adjusted according to new design requirements (e.g., more precise control of the active layer thickness and interface is needed to achieve lower parasitic capacitance and specific waveguide modes). For example, the original 480 degrees Celsius is increased to 495 degrees Celsius to improve material quality. Simultaneously, the precursor beam intensity is adjusted; for example, the beam intensity of the indium source is appropriately reduced to fine-tune the composition and strain state of the indium gallium arsenide phosphide (IGaAs) trap layer in the multi-quantum well. These adjusted growth parameters are recorded and used to perform a new round of epitaxial growth, with the goal of making the performance of the newly grown epitaxial wafer more closely match the requirements of the device design.

[0053] By reverse-engineering key growth parameters of molecular beam epitaxy, such as temperature and precursor beam current, according to the device design scheme, this invention can achieve directional optimization of the properties of the active layer material, making the epitaxial growth process more target-oriented, thereby improving the ability of the finally prepared epitaxial material to support the performance of the target laser.

[0054] In some implementations, the feedback adjustment of growth parameters also includes in-situ doping control, which controls the doping concentration and uniformity by adjusting the flow rate of the doping source gas.

[0055] In-situ doping control refers to the process of simultaneously introducing dopant elements during epitaxial growth to change the conductivity type of the material in real time. For example, in MOCVD or MBE growth, a silicon- or beryllium-containing gas or solid source is introduced to directly form N-type or P-type semiconductor layers during crystal growth. Adjusting the flow rate of the dopant source gas refers to changing the flow rate of the dopant precursor (such as silane or diethylzinc) delivered to the reaction chamber, thereby adjusting the doping level in real time. For example, using a mass flow controller for precise flow setting and feedback can achieve linear control of carrier concentration. Doping concentration refers to the number of impurity atoms incorporated into a unit volume of semiconductor material. It is a key parameter determining the conductivity type and resistivity of the material. For example, by adjusting the dopant source flow rate, the goal is to control the carrier concentration of the epitaxial layer (such as the cladding) within a specific range of 1e17 cm^-3 to 1e19 cm^-3. Uniformity refers to the consistency of dopant atoms distribution within the epitaxial layer plane and along the growth direction. It is an important indicator for evaluating the quality of epitaxial wafers. For example, by optimizing the flow field in the reaction chamber and the growth temperature, efforts are made to ensure that the fluctuation of doping concentration within the wafer is less than a specific percentage.

[0056] As a concrete example, the feedback adjustment of growth parameters specifically includes in-situ doping control of the MOCVD process. To achieve the target cladding carrier concentration for device design parameters (such as specific series resistance requirements), doping concentration and uniformity are controlled by precisely adjusting the flow rate of the dopant source gas (e.g., silane for N-type doping). For instance, based on design feedback, the silane flow rate is increased from 10 sccm to 12 sccm to increase the electron concentration in the lower cladding from 5e17 cm^-3 to 8e17 cm^-3, while optimizing reaction chamber conditions to ensure doping uniformity within the wafer is better than ±2%. This real-time, controllable doping adjustment is a crucial step in ensuring that the electrical properties of the epitaxial material meet the design requirements of high-frequency lasers.

[0057] By introducing and precisely controlling the in-situ doping process in the feedback adjustment stage, this invention can actively and precisely regulate the electrical characteristics (carrier concentration and distribution uniformity) of the epitaxial layer (such as the cladding), ensuring that it strictly follows the conductivity requirements of the device design scheme, thereby effectively optimizing the injection efficiency and overall electrical performance of the laser.

[0058] In some implementations, the in-situ doping control step employs a closed-loop feedback mechanism and utilizes real-time monitoring data from secondary ion mass spectrometry to adjust the flow rate of the dopant source gas.

[0059] A closed-loop feedback mechanism refers to a control strategy that compares the system output (such as the real-time monitored doping concentration) with the target value and automatically adjusts the input (such as the gas flow rate) based on the deviation. For example, it can use a proportional-integral-derivative controller for dynamic adjustment to maintain the stability and accuracy of process parameters. Real-time monitoring data from secondary ion mass spectrometry (SIMS) refers to the instantaneous acquisition and analysis of the mass-to-charge ratio information of sputtered ions during the growth process by the SIMS equipment, such as the signal intensity of specific dopant isotopes. This data can semi-quantitatively or quantitatively reflect the instantaneous doping concentration near the growth surface.

[0060] As a concrete example, a closed-loop feedback mechanism is employed when implementing in-situ doping control. Specifically, a secondary ion mass spectrometer (SIMS) connected to the MOCVD reaction chamber is used for real-time monitoring. The SIMS system continuously acquires ion signals from the grown surface region, providing real-time monitoring data on the concentration of dopants (such as silicon). This data is sent to the process control system and compared with a preset target doping concentration curve. If the real-time data indicates that the doping concentration deviates from the target, the system immediately generates a correction signal and automatically adjusts the flow rate of the doping source gas (such as silane), for example, by reducing the flow rate to lower the excessively high doping concentration. This closed-loop control based on real-time SIMS data significantly improves the control accuracy and repeatability of doping concentration and longitudinal distribution.

[0061] By introducing a closed-loop feedback mechanism based on real-time monitoring of secondary ion mass spectrometry into in-situ doping control, this invention can achieve high-precision, dynamic online control of doping concentration and its distribution, significantly reduce performance fluctuations between batches, and ensure that the electrical parameters of the epitaxial material closely match the stringent requirements of device design.

[0062] In some implementations, the laser waveguide structure is designed to confine heterogeneous structures separately.

[0063] Separate confinement of heterostructures can refer to a specific laser waveguide design scheme in which the carrier confinement function and the optical field confinement function are respectively undertaken by different material layers or structures. For example, a three-layer symmetrical or asymmetrical structure with a narrow bandgap active layer (such as indium gallium arsenide phosphide) sandwiched between a wide bandgap cladding layer (such as indium phosphide) can achieve efficient confinement of carriers and optical mode fields to different degrees.

[0064] As a specific example, in this invention, the generated laser waveguide structure is specifically designed to separately confine heterogeneous structures. For instance, this structure consists of an indium gallium arsenide phosphide multiple quantum well layer serving as the active region, and indium phosphide layers on its upper and lower sides. The indium phosphide cladding has a wider bandgap than the active region, and its main function is to effectively confine the injected carriers within the active region for radiative recombination. Simultaneously, due to the refractive index difference between indium phosphide and the active region material, this structure also confines the generated optical mode field to propagate within the waveguide layer. This separate confinement design allows for the optimization of carrier confinement and optical field confinement separately, thereby helping to reduce the laser's threshold current and improve mode stability.

[0065] By specifically designing the laser waveguide structure to confine heterogeneous structures separately, this invention enables independent optimization of the carrier and optical mode field confinement capabilities. This results in a reduction of device threshold current and an improvement in quantum efficiency, while simultaneously achieving a more stable transverse optical mode and beam quality, thereby enhancing the overall performance of the laser.

[0066] The preferred embodiments disclosed above are merely illustrative of this specification. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this invention. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize this specification. This specification is limited only by the claims and their full scope and equivalents.

Claims

1. An epitaxial growth method for high speed optoelectronic devices, characterized by, The application relates to a method for designing a laser structure, comprising the following steps: providing a substrate and performing pretreatment on the substrate; growing a buffer layer and a cladding layer on the pretreated substrate in sequence by a metal organic chemical vapor deposition process; growing an active layer on the buffer layer by a molecular beam epitaxy process, so as to form an epitaxial structure; performing performance characterization on the epitaxial structure, so as to obtain measured electrical performance parameters and measured optical performance parameters; generating a design scheme including a laser electrode structure and a laser waveguide structure based on the measured electrical performance parameters and the measured optical performance parameters, wherein the design scheme contains a group of device design parameters; adjusting growth parameters of the metal organic chemical vapor deposition process and the molecular beam epitaxy process according to the device design parameters, and performing a new round of epitaxial growth based on the adjusted growth parameters.

2. The method of claim 1, wherein, The step of performing pretreatment on the substrate comprises growing a low-temperature pre-growth layer, and the material of the low-temperature pre-growth layer is aluminum arsenide.

3. The method of claim 1, wherein, In the step of growing the active layer by the molecular beam epitaxy process, the growth temperature is controlled in a first temperature range; in the steps of growing the buffer layer and the cladding layer by the metal organic chemical vapor deposition process, the growth temperature is controlled in a second temperature range which is higher than the first temperature range.

4. The method of claim 1, wherein, The step of performing performance characterization on the epitaxial structure comprises: measuring the carrier concentration and the mobility of the epitaxial structure by a Hall effect test method, so as to obtain the measured electrical performance parameters; measuring the refractive index and the extinction coefficient of the epitaxial structure by a spectroscopic ellipsometry method, so as to obtain the measured optical performance parameters.

5. The method of claim 1, wherein, In the step of generating the design scheme of the laser electrode structure, the parasitic capacitance design value of the laser electrode structure is determined by a first calculation formula as follows: wherein, represents the parasitic capacitance design value; represents the vacuum permittivity; represents the laser electrode structure and the cladding layer overlap area design value, determined based on the target spot size; M represents the total number of dielectric layers between the laser electrode structure and the active layer; represents the thickness design value of the mth dielectric layer, set according to the measured thickness of the epitaxial structure; represents the relative permittivity of the mth dielectric layer, obtained by querying the obtained measured parameters of the optical performance; N represents the total number of conductive paths constituting the laser electrode structure; represents the length design value of the nth conductive path; represents the width design value of the nth conductive path; represents the electrical conductivity of the material used by the nth conductive path; represents the system characteristic impedance.

6. The method of claim 5, wherein, the overlapping area design value is determined by a second calculation formula as follows: wherein represents the overlap area design value; P represents the number of main emission peaks shown by the active layer in the measurement; represents the wavelength measured value of the pth emission peak, provided by the optical performance measured parameters obtained by characterization; represents the effective refractive index measured value of the waveguide at the pth emission peak, provided by the optical performance measured parameters obtained by characterization; represents the mode overlap integral coefficient related to the laser waveguide structure; represents the gain normalization constant, with the dimension of cubic meter; to represents the gain spectrum energy range of the active layer; represents the joint density of states function of the active layer, calculated from the optical performance measured parameters obtained by characterization; dE is the differential of the energy E, dE and the integral symbol ∫ represent the integration of the joint density of states function over the energy E, for calculating the total density of states within a specific energy window; represents the differential gain coefficient measured value of the active layer, provided by the optical performance measured parameters obtained by characterization; e represents the base number of the natural logarithm.

7. The method of claim 1, wherein, The step of adjusting the growth parameters comprises: adjusting the growth temperature and the precursor beam current intensity of the molecular beam epitaxy process according to the device design parameters.

8. The method of claim 7, wherein, The step of adjusting the growth parameters further comprises in-situ doping control, and the doping concentration and uniformity are controlled by adjusting the flow of a doping source gas.

9. The method of claim 8, wherein, The in-situ doping control step adopts a closed-loop feedback mechanism, and the flow of the doping source gas is adjusted by using real-time monitoring data of secondary ion mass spectrometry.

10. The method of claim 1, wherein, The laser waveguide structure is designed to limit heterostructures respectively.

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