A method for producing a regrown low-defect semi-insulating semiconductor laser window

Abstract

The application discloses a preparation method of a regrown low-defect semi-insulating semiconductor laser window, and belongs to the technical field of semiconductor laser device preparation. The method comprises the following steps: once epitaxy, window region definition, in-situ cleaning, transition layer growth, semi-insulating regrowth and subsequent processes are completed by relying on secondary epitaxy technology; aluminum oxide at the window interface is removed and the metering ratio of a GaAs surface is ensured by in-situ cleaning of a mixed gas of TBCl and AsH3; a transition layer with a linear gradient of 10% to 90% of aluminum component is grown to realize lattice stress release and no optical absorption; a semi-insulating regrowth layer with high resistivity is prepared by Fe doping to realize electrical isolation of the window region; and subsequent processes such as electrode preparation and cavity surface coating are completed to finish chip processing. According to the method, window defects and optical absorption loss are greatly reduced, interlayer peeling is avoided, and the damage resistance and working stability of the laser cavity surface are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser device fabrication technology, and in particular to a method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window. Background Technology

[0002] High-power AlGaAs-based edge-emitting laser diodes (ALDs) are core optoelectronic devices that occupy an irreplaceable position in high-end applications such as industrial processing, laser medicine, and optical communication due to their high optical power density and high electro-optical conversion efficiency. These applications place stringent technical requirements on the output power, long-term operational stability, and lifespan of lasers. As the core structure for laser light emission, the laser window's fabrication process directly determines the overall performance of high-power AlGaAs-based edge-emitting laser diodes. Therefore, developing low-defect, high-reliability laser window fabrication technology has become a key research focus and crucial development area in this field.

[0003] The current laser window fabrication process for high-power AlGaAs-based edge-emitting laser diodes faces several critical technical bottlenecks that hinder device performance improvement and industrial application. First, in the interface treatment of the laser window region, the native alumina (Al2O3) film formed during device fabrication easily induces numerous crystal defects during subsequent epitaxial growth, increasing light absorption loss in the window region. Existing cleaning processes not only struggle to completely remove the alumina film but also easily disrupt the surface stoichiometry, causing surface reconstruction and elemental deficiencies, thus reducing the quality of epitaxial growth. Second, regarding the structural matching between the window layer and the active region, the lattice mismatch can easily lead to localized stress concentration. Traditional processes often lack a well-designed transition layer, making it difficult to fully release lattice stress, resulting in interlayer delamination between the window layer and the active region, affecting the structural stability and operational reliability of the laser device. Third, in terms of cavity surface protection, ordinary window layers cannot achieve effective electrical isolation, allowing current to easily inject into the laser emission cavity surface during operation, causing cavity surface optical catastrophic damage (COMD), limiting the maximum output power and lifespan of the laser.

[0004] To address the technical problems in the existing technology, such as high defect density, large light absorption loss, concentrated lattice stress, and easy damage to the cavity surface in laser windows due to multiple defects in the cleaning process, transition layer design, and window layer electrical isolation design, there is an urgent need to design a low-defect semi-insulating laser window fabrication method that can achieve complete removal of alumina, effective release of lattice stress, and efficient electrical isolation in the window area. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a regenerated long, low-defect semi-insulating semiconductor laser window, comprising the following steps: S1. Primary epitaxy: The basic structure of GaAs edge-emitting laser chip is prepared based on secondary epitaxy technology. Using GaAs substrate as the base, N-type confinement layer, N-type separated confinement layer, quantum well active region, P-type separated confinement layer and P-type confinement layer are epitaxially grown sequentially through metal-organic chemical vapor deposition process. The growth parameters of each layer are precisely controlled to ensure lattice matching and optical performance. S2. Window region definition: The window region is defined at both ends of the active region of the quantum well along the laser emission direction using a photolithography-etching integrated process. First, the window pattern is transferred to the photoresist layer on the device surface using a photolithography process, and then a composite etching process is used to etch to the surface of the N-type separation and confinement layer to form a window groove. S3. In-situ cleaning: The etched chip is transferred to the MOCVD reactor, which is not exposed to the atmospheric environment. A mixture of tributyl chloride (TBCl) and arsine (AsH3) is introduced to perform high-temperature cleaning, which removes the native alumina (Al2O3) at the window groove interface, while maintaining the stoichiometry of the GaAs surface to prevent surface reconstruction and element loss. S4. Transition Layer Growth: Immediately after cleaning, initiate the metal-organic chemical vapor deposition process to epitaxially grow Al with a gradually changing composition. x Ga1- x As a transition layer, it achieves a smooth transition of lattice constant, releases lattice stress between the window layer and the active region, and ensures that the transition layer has no optical absorption for laser emission; S5. Semi-insulating Regeneration: A semi-insulating regeneration layer is epitaxially grown on the transition layer using metal-organic chemical vapor deposition. The regeneration sequence includes a semi-insulating regeneration layer laterally adjacent to the active gain region. Compensating deep-level impurities are introduced during the regeneration process to ensure the resistivity of the semi-insulating regeneration layer is greater than 10 ohms. 6 ohm・cm, to achieve effective electrical isolation between the end face of the window area and the injected current, preventing current from being injected into the cavity surface area; S6. Subsequent processes: On the semi-insulating regenerated layer, the top ohmic contact layer is epitaxially grown using metal-organic chemical vapor deposition. Then, the GaAs edge-emitting laser chip is fabricated by sequentially performing photolithography patterning, etching and windowing, metal electrode evaporation, alloying, and cavity surface coating processes.

[0007] Furthermore, the active region of the quantum well in step S1 is a multi-quantum-well structure, used to achieve high-efficiency optical gain.

[0008] Furthermore, the composite etching process in step S2 mainly uses dry etching and supplemented by wet etching. The dry etching is inductively coupled plasma etching, and the wet etching uses a diluted hydrofluoric acid system.

[0009] Furthermore, the process parameters for in-situ cleaning in step S3 are as follows: the gas flow ratio of TBCl to AsH3 is 1:50-1:200, the cleaning temperature is 700-750℃, and the cleaning time is 30-120 seconds.

[0010] Furthermore, the thickness of the transition layer in step S4 is 5nm-20nm; along the thickness direction of the transition layer, the proportion of aluminum component gradually changes linearly from 10% to 90%, so that the band gap energy of the transition layer increases monotonically from the etching interface to the outer surface of the transition layer, and the final band gap energy is higher than the laser emission photon energy.

[0011] Furthermore, the compensating deep-level impurity mentioned in step S5 is Fe, and the doping concentration of the Fe impurity is 1×10⁻⁶. 16 -1×10 18 atoms / cm 3 .

[0012] Furthermore, the cavity surface coating described in step S6 is a combination structure of an antireflective coating and a high-reflectivity coating.

[0013] The beneficial effects of this invention are: This invention effectively solves the technical pain points of traditional high-power AlGaAs base-edge emitting laser window fabrication, such as numerous defects, high stress, and easy damage to the cavity surface, through core process designs including in-situ precise cleaning, composition-gradient transition layer growth, and iron-doped semi-insulating regeneration. This significantly improves overall performance and industrial applicability. The in-situ cleaning process effectively removes native alumina from the window interface, ensuring stable stoichiometry on the GaAs surface and avoiding impurity-induced crystal defects. Combined with a linearly graded aluminum composition transition layer, it achieves a smooth transition of the lattice constant, effectively releasing lattice stress and preventing interlayer peeling. Simultaneously, the bandgap energy design of the transition layer eliminates optical absorption and reduces optical transmission loss. The high resistivity of the iron-doped semi-insulating regeneration layer efficiently blocks current injection into the laser emission cavity surface, preventing overheating and carrier accumulation, significantly increasing the cavity surface optical catastrophic damage threshold, and improving the laser's maximum output power and operational stability. Furthermore, the entire preparation process is based on mature MOCVD epitaxy and semiconductor micromachining technology, requiring no special equipment, with good process compatibility, enabling industrial-scale mass production, effectively reducing preparation costs, and suitable for high-end application scenarios such as industrial processing, laser medicine, and optical communication. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the GaAs edge-emitting laser chip of the present invention.

[0015] Figure 2 This is a structural diagram of a single epitaxial process.

[0016] Figure 3 This is a structural diagram of the process of etching to form a window.

[0017] Figure 4 This is a structural diagram of the transition layer during growth.

[0018] Figure 5 This is a structural diagram of the semi-insulating epitaxial growth process.

[0019] Figure 6 This is a structural diagram when the dielectric protective layer is removed.

[0020] Figure 7 This is a structural diagram showing the continuous growth of the P-type confinement layer and the growth of the contact layer.

[0021] Figure 8 A structural diagram of the fabrication process for a P-type electrode.

[0022] Figure 9 The structural diagram shows the process of thinning the N-type substrate and fabricating the N-type electrode.

[0023] Figure 10 This is a structural diagram of bar formation when cleaving along the window.

[0024] Figure 11 This is a schematic diagram of the cross-sectional structure of a laser bar.

[0025] In the figure: 101, GaAs substrate; 102, N-type confinement layer; 103, N-type separated confinement layer; 104, quantum well active region; 105, P-type separated confinement layer; 106, P-type confinement layer; 107, dielectric protective layer; 108, window groove; 109, transition layer; 110, semi-insulating regeneration layer; 111, P-type confinement growth continuation layer; 112, top ohmic contact layer; 113, P-type electrode; 114, N-type electrode; 115, Schematic diagram of cleavage line position; 116, antireflection film; 117, high reflectivity film. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings.

[0027] This invention discloses a method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window.

[0028] Reference Figures 1 to 11A method for fabricating a regenerated, long, low-defect semi-insulating semiconductor laser window is disclosed, applicable to high-power AlGaAs-based edge-emitting laser diodes. This method relies on secondary epitaxy technology, integrating core process designs such as in-situ precise cleaning, composition-gradient transition layer growth, and iron-doped semi-insulating regeneration. It solves problems such as numerous defects, high stress, and easy damage to the cavity surface in laser window fabrication, achieving low light absorption, high electrical isolation, and high reliability, effectively improving the maximum output power and operational stability of the laser. The specific fabrication method is as follows: S1. Primary Epitaxy: The basic structure of the GaAs edge-emitting laser chip is fabricated based on secondary epitaxy technology. Using GaAs substrate 101 as the substrate, an N-type confinement layer 102, an N-type separated confinement layer 103, a quantum well active region 104, a P-type separated confinement layer 105, and a P-type confinement layer 106 are sequentially epitaxially grown using metal-organic chemical vapor deposition (MOCVD). During the fabrication process, the growth parameters of each epitaxial layer are precisely controlled to ensure the lattice matching between each layer and the overall optical performance of the device from the process level. Among them, the quantum well active region 104 adopts a multi-quantum well structure, which can achieve high-efficiency optical gain and provide the core gain basis for the laser's optical emission.

[0029] S2. Window region definition: A window region is defined at both ends of the active region 104 of the quantum well along the laser emission direction using a photolithography-etching integrated process. First, the window pattern is transferred to the photoresist layer on the device surface using a photolithography process. A dielectric protective layer 107, such as SiNx or SiO2, can be pre-prepared on the device surface for basic protection. Then, a composite etching process is used to etch the device, and the etching depth is precisely controlled to the surface of the N-type separation confinement layer 103 to form a window groove 108 on the device surface. This composite etching process mainly uses dry etching and supplemented by wet etching. The dry etching uses inductively coupled plasma etching, while the wet etching uses a diluted hydrofluoric acid system. This ensures that the window groove 108 has a regular shape and steep sidewalls, while effectively avoiding structural damage to the active region 104 of the quantum well caused by excessive etching, thus laying a structural foundation for the subsequent epitaxial growth of the window layer.

[0030] S3. In-situ Cleaning: The etched chip is transferred to an MOCVD reactor, away from the atmospheric environment, to avoid introducing new impurities and oxide layers onto the chip surface. A mixed gas of tributyl chloride (TBCl) and arsine (AsH3) is introduced for high-temperature cleaning. The cleaning process parameters are precisely controlled as follows: TBCl to AsH3 gas flow rate ratio of 1:50-1:200, cleaning temperature of 700-750℃, and cleaning time of 30-120 seconds. Under these parameters, the native alumina (Al2O3) at the window recess 108 interface can be completely removed, avoiding oxide-induced epitaxial growth defects at the source. At the same time, it ensures the stability of the stoichiometry of the GaAs substrate 101 and the device surface, preventing surface reconstruction and element loss, and providing a good surface condition for subsequent epitaxial growth. During the cleaning process, the mixed gas flow rate and cleaning temperature must be precisely controlled to avoid excessive etching of the GaAs surface due to excessive flow rate or temperature, which would affect the quality of subsequent epitaxial growth.

[0031] S4, Growth of transition layer 109: Immediately after in-situ cleaning, the metal-organic chemical vapor deposition process is started to epitaxially grow Al with a compositional gradient at the window groove 108. x Ga1- x As the transition layer 109, the thickness of the transition layer 109 is controlled within the range of 5nm-20nm, and the proportion of aluminum composition linearly increases from 10% to 90% along the thickness direction of the transition layer 109. This compositional gradient design makes the bandgap energy of the transition layer 109 monotonically increase from the etching interface to the outer surface of the transition layer 109, and the final bandgap energy is higher than the laser emission photon energy, ensuring that the transition layer 109 has no optical absorption for laser emission. At the same time, the linear gradient of the aluminum composition achieves a smooth transition of the lattice constant, effectively releasing the lattice stress between the subsequent window layer and the quantum well active region 104, avoiding the interlayer delamination problem caused by stress concentration, and balancing the stress release effect and the device integration. During the fabrication process, it is necessary to ensure that the aluminum composition gradient rate of the transition layer 109 is uniform, and the linear gradient of the composition is achieved by precisely controlling the source material flow rate of MOCVD.

[0032] S5, Semi-insulation regeneration: In Al x Ga1- x On the As transition layer 109, a semi-insulating regenerated layer 110 is epitaxially grown using a metal-organic chemical vapor deposition process. The regenerated layer sequence includes a semi-insulating regenerated layer 110 laterally adjacent to the active gain region. To achieve efficient electrical isolation in the window region, a compensating deep-level impurity is introduced during the regenerated process. The impurity is selected as iron (Fe), and the Fe impurity doping concentration is precisely controlled at 1 × 10⁻⁶. 16 -1×10 18 atoms / cm³, making the resistivity of the semi-insulating regrown layer 110 greater than 10. 6To achieve effective electrical isolation between the end face of the window region and the injected current, the injection of current into the laser emission cavity surface is blocked, thus avoiding catastrophic optical damage to the cavity surface caused by local overheating and carrier accumulation. To precisely control the doping effect, the Fe doping concentration of the semi-insulating regenerated layer 110 is professionally characterized using secondary ion mass spectrometry (SIMS). Doping parameters are adjusted in real time based on the characterization results to avoid excessively high doping concentrations introducing additional optical absorption, or excessively low doping concentrations failing to meet the preset resistivity requirements, thereby ensuring the stability of the electrical isolation effect of the semi-insulating regenerated layer 110.

[0033] S6. Subsequent Processes: On the semi-insulating regeneration layer 110, a P-type confined growth continuation layer 111 is epitaxially grown using metal-organic chemical vapor deposition. Then, a top ohmic contact layer 112 is epitaxially grown on the P-type confined growth continuation layer 111 to achieve electrode extraction and effective current injection for the laser. Subsequently, the device is sequentially patterned by photolithography and etched to create windows, thus accurately defining the electrode region. Then, a P-type electrode 113 is prepared by vapor deposition on the surface of the top ohmic contact layer 112 using a Ti / Pt / Au multilayer metal structure. After vapor deposition, alloying treatment is performed to improve the ohmic contact performance between the P-type electrode 113 and the device surface. At the same time, the GaAs substrate 101 is thinned to form an N-type electrode 114, constituting the complete electrode structure of the device. After the electrode fabrication is completed, the position of the cleavage line is marked at the preset position of the device (115), and the device is cleaved according to the position of the line to form a flat laser emission cavity surface. Finally, the laser emission cavity surface is coated with a cavity surface coating. The coating adopts a combination structure of antireflection film 116 and high reflectivity film 117 to optimize the light emission and light gain efficiency of the laser. After the above full process, a high-performance GaAs edge-emitting laser chip is finally obtained.

[0034] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window, characterized in that: Includes the following steps: S1. Primary epitaxy: The basic structure of GaAs edge-emitting laser chip is prepared based on secondary epitaxy technology. Using GaAs substrate (101) as the substrate, N-type confinement layer (102), N-type separated confinement layer (103), quantum well active region (104), P-type separated confinement layer (105) and P-type confinement layer (106) are epitaxially grown sequentially by metal-organic chemical vapor deposition process. The growth parameters of each layer are precisely controlled to ensure lattice matching and optical performance. S2, Window region definition: The window region is defined at both ends of the active region (104) of the quantum well along the laser emission direction using a photolithography-etching integrated process; the window pattern is first transferred to the photoresist layer on the device surface by photolithography, and then etched to the surface of the N-type separation confinement layer (103) by a composite etching process to form a window groove (108); S3, In-situ cleaning: The etched chip is transferred to the MOCVD reactor and is not exposed to the atmospheric environment. A mixture of tributyl chloride (TBCl) and arsine (AsH3) gas is introduced to perform high-temperature cleaning to remove the native alumina Al2O3 at the window groove (108) interface, while maintaining the stoichiometry of the GaAs surface to prevent surface reconstruction and element loss. S4, Transition Layer (109) Growth: Immediately after cleaning, start the metal-organic chemical vapor deposition process to epitaxially grow Al with gradually changing composition. x Ga1- x As a transition layer (109), a smooth transition of the lattice constant is achieved, the lattice stress between the window layer and the active region is released, and the transition layer (109) is ensured to have no optical absorption for laser emission. S5. Semi-insulating regeneration: A semi-insulating regeneration layer (110) is epitaxially grown on the transition layer (109) using a metal-organic chemical vapor deposition process. The regeneration sequence includes a semi-insulating regeneration layer (110) laterally adjacent to the active gain region. By introducing compensating deep-level impurities during the regeneration process, the resistivity of the semi-insulating regeneration layer (110) is made greater than 10 Ω·cm. 6 ohm・cm, to achieve effective electrical isolation between the end face of the window area and the injected current, preventing current from being injected into the cavity surface area; S6. Subsequent processes: On the semi-insulating regenerated layer (110), the top ohmic contact layer (112) is epitaxially grown by metal-organic chemical vapor deposition. Then, the GaAs edge-emitting laser chip is obtained by sequentially performing photolithography patterning, etching and windowing, metal electrode evaporation, alloying treatment and cavity surface coating processes.

2. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The quantum well active region (104) mentioned in step S1 is a multi-quantum well structure used to achieve high-efficiency optical gain.

3. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The composite etching process in step S2 mainly uses dry etching and supplemented by wet etching. The dry etching is inductively coupled plasma etching, and the wet etching uses a diluted hydrofluoric acid system.

4. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The process parameters for in-situ cleaning in step S3 are as follows: the gas flow ratio of TBCl to AsH3 is 1:50-1:200, the cleaning temperature is 700-750℃, and the cleaning time is 30-120 seconds.

5. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The thickness of the transition layer (109) in step S4 is 5nm-20nm; along the thickness direction of the transition layer (109), the proportion of aluminum component gradually changes linearly from 10% to 90%, so that the band gap energy of the transition layer (109) increases monotonically from the etching interface to the outer surface of the transition layer (109), and the final band gap energy is higher than the laser emission photon energy.

6. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The compensating deep-level impurity mentioned in step S5 is Fe, and the doping concentration of the Fe impurity is 1×10⁻⁶. 16 -1×10 18 atoms / cm 3 .

7. The method for fabricating a regenerated long, low-defect semi-insulating semiconductor laser window according to claim 1, characterized in that: The cavity surface coating in step S6 is a combination structure of antireflective coating (116) and high reflective coating (117).

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