A GaN-based green laser and a preparation method thereof

Abstract

The application discloses a GaN-based green laser and a preparation method thereof, and relates to the technical field of semiconductor lasers. The preparation method comprises the following steps: sequentially depositing a buffer layer and an n-type AlGaN confinement layer comprising a first sublayer and a second sublayer arranged in sequence on a substrate layer, wherein the Al component of the first sublayer is higher than that of the second sublayer; sequentially depositing an n-type waveguide layer, a quantum well layer, a p-type waveguide layer and an electron blocking layer on the n-type AlGaN confinement layer; and sequentially depositing a p-type AlGaN confinement layer and a contact layer on the electron blocking layer, wherein the p-type AlGaN confinement layer comprises a third sublayer and a fourth sublayer arranged in sequence, and the Al component of the third sublayer is lower than that of the fourth sublayer. According to the application, the refractive index difference between the confinement layer and the waveguide layer is significantly improved, and an asymmetric optical potential well is constructed while the stability of the epitaxial structure is ensured, so that the optical confinement capability is enhanced, the light field leakage is inhibited, and the absorption loss of the p-type region is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a GaN-based green laser and its fabrication method. Background Technology

[0002] Gallium nitride (GaN)-based green laser diodes have attracted attention due to their wide application in laser displays, laser lighting, and high-density optical storage. However, compared to blue-light devices, green-light GaN-based lasers require the introduction of higher In content into the InGaN quantum well, which can easily lead to problems such as lattice mismatch, stress accumulation, and increased defects, thus placing higher demands on the epitaxial structure design of the devices.

[0003] In existing technologies, AlGaN confinement layers are typically placed above and below the waveguide layer to achieve optical confinement. However, due to the requirements for crack suppression and crystal quality control during epitaxial growth, the Al composition in the confinement layer is usually difficult to increase significantly, resulting in a small refractive index difference between the confinement layer and the waveguide layer, making it difficult to form an effective optical potential well structure. In this case, the optical field is not sufficiently confined in the vertical direction, and a large amount of light energy leaks into the p-type contact layer or substrate region in the form of evanescent waves, which easily generates parasitic modes and introduces large optical losses, thereby reducing the optical confinement factor and device efficiency.

[0004] Furthermore, existing structures typically employ symmetrical or approximately constant composition designs for the upper and lower confinement layers, without optimizing the light field distribution to account for the high light absorption characteristics of the p-type region. This results in a large proportion of the light field still being distributed in the p-type region, further exacerbating the loss problem caused by free carrier absorption and impurity absorption.

[0005] Therefore, how to improve the refractive index difference between the confinement layer and the waveguide layer to enhance optical confinement capability while ensuring the stability of the epitaxial structure and the quality of the crystal, and at the same time optimize the distribution of the light field in the device to reduce the absorption loss in the p-type region, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] One objective of the first aspect of this invention is to provide a method for fabricating a GaN-based green laser, which solves the technical problems in the prior art, such as weak optical confinement capability, easy leakage of the light field to the p-type region and substrate, large optical absorption loss of the device, and difficulty in achieving the same level of epitaxial structure stability due to insufficient refractive index difference and symmetrical structure between the AlGaN confinement layer and the waveguide layer.

[0007] Another objective of the first aspect of the present invention is to further reduce internal optical loss while maintaining a high optical confinement factor.

[0008] A second aspect of the present invention is to provide a GaN-based green laser prepared according to the above-described preparation method.

[0009] According to a first aspect of the present invention, the present invention provides a method for fabricating a GaN-based green laser, comprising: A buffer layer and an n-type AlGaN confinement layer are sequentially deposited on a substrate. The n-type AlGaN confinement layer includes a first sub-layer and a second sub-layer disposed sequentially. The first sub-layer abuts against the buffer layer. The Al content of the first sub-layer is higher than that of the second sub-layer, and the difference in Al content between the first sub-layer and the second sub-layer is any value between 3% and 6%. An n-type waveguide layer, a quantum well layer, a p-type waveguide layer, and an electron blocking layer are sequentially deposited on the n-type AlGaN confinement layer. A p-type AlGaN confinement layer and a contact layer are sequentially deposited on the electron blocking layer to fabricate the GaN-based green laser. The p-type AlGaN confinement layer includes a third sub-layer and a fourth sub-layer sequentially disposed thereon. The fourth sub-layer abuts against the contact layer. The Al composition of the third sub-layer is lower than that of the fourth sub-layer, and the difference in Al composition between the third and fourth sub-layers is any value between 3% and 7%. The first sublayer has an Al content of any value between 6% and 12%, the second sublayer has an Al content of any value between 3% and 6%, the third sublayer has an Al content of any value between 4% and 8%, and the fourth sublayer has an Al content of any value between 6% and 12%.

[0010] Optionally, the average Al composition of the p-type AlGaN confinement layer is higher than that of the n-type AlGaN confinement layer, wherein the average Al composition is the average value of the Al composition of each sublayer weighted by its thickness.

[0011] Optionally, the average Al component difference is any value between 2% and 8%.

[0012] Optionally, the thickness ratio of the first sub-layer to the second sub-layer is any value between 1 and 2.5, and the thickness ratio of the fourth sub-layer to the third sub-layer is any value between 0.75 and 2.0.

[0013] Optionally, the thickness of the n-type AlGaN confinement layer is any value between 600nm and 1000nm, and the thickness of the p-type AlGaN confinement layer is any value between 200nm and 400nm.

[0014] Optionally, the growth rate of the p-type AlGaN confinement layer and the n-type AlGaN confinement layer is any value between 0.5 μm / h and 1.5 μm / h.

[0015] Optionally, the thickness of the n-type waveguide layer is any value between 250nm and 300nm, and the thickness of the p-type waveguide layer is any value between 180nm and 220nm.

[0016] Optionally, the quantum well layer includes InGaN layers and GaN layers arranged in a periodic manner, wherein the In composition of the InGaN layer is any value between 26% and 30%.

[0017] Optionally, the substrate layer is any one of a sapphire substrate, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate.

[0018] According to a second aspect of the present invention, the present invention also provides a GaN-based green laser prepared by the method described in any one of the above claims, wherein the GaN-based green laser comprises, from bottom to top, a substrate layer, a buffer layer, an n-type AlGaN confinement layer, an n-type waveguide layer, a quantum well layer, a p-type waveguide layer, an electron blocking layer, a p-type AlGaN confinement layer, and a contact layer, wherein a refractive index difference greater than or equal to 0.05 is formed between the n-type AlGaN confinement layer and the n-type waveguide layer, and between the p-type waveguide layer and the p-type AlGaN confinement layer, respectively.

[0019] This invention constructs segmented Al composition control structures in both n-type and p-type AlGaN confinement layers. This design combines a low-Al composition region near the waveguide layer and a high-Al composition region away from the waveguide layer along the epitaxial growth direction. This ensures good lattice matching and epitaxial quality at the interface of the confinement layer, while simultaneously forming a high refractive index barrier on the side away from the active region. This results in a high refractive index difference optical confinement structure within the overall structure. This structure increases the refractive index difference Δn while avoiding the stress accumulation and crystal defect problems associated with traditional overall Al composition increases, achieving compatibility between enhanced optical confinement and improved epitaxial quality. Furthermore, by controlling the optical field distribution through segmented structures, the optical field mode is moved away from the p-type high-absorption region, thereby reducing internal optical losses. This achieves a synergistic effect between improved optical confinement factor, suppressed optical leakage, and optimized material quality, significantly improving the overall optoelectronic performance of the GaN-based green laser.

[0020] Furthermore, by setting the average Al composition of the p-type AlGaN confinement layer to be higher than that of the n-type AlGaN confinement layer, the upper and lower confinement layers form an asymmetric refractive index distribution structure, thereby constructing an asymmetric optical potential well. This effectively reduces the light absorption loss caused by Mg doping, reduces internal optical loss while maintaining a high optical confinement factor, and thus achieves synergistic optimization between optical confinement capability and loss control.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for fabricating a GaN-based green laser according to an embodiment of the present invention; Figure 2 This is a schematic structural diagram of a GaN-based green laser according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the Al composition in a GaN-based green laser according to Embodiment 1 of the present invention; Figure 4 This is a schematic light field distribution diagram of the GaN-based green laser according to Embodiment 1 of the present invention; Figure 5 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the Al composition in the GaN-based green laser according to Comparative Example 1 of the present invention; Figure 7 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 1 of the present invention; Figure 8 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 1 of the present invention; Figure 9 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 2 of the present invention; Figure 10 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 2 of the present invention; Figure 11 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 3 of the present invention; Figure 12 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 3 of the present invention; Figure 13 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 4 of the present invention; Figure 14This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 4 of the present invention; Figure 15 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 5 of the present invention; Figure 16 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 5 of the present invention; Figure 17 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 6 of the present invention; Figure 18 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 6 of the present invention; Figure 19 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 7 of the present invention; Figure 20 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 7 of the present invention.

[0023] Figure label: 100-GaN-based green laser, 10-substrate layer, 20-buffer layer, 30-n-type AlGaN confinement layer, 40-n-type waveguide layer, 50-quantum well layer, 60-p-type waveguide layer, 70-electron blocking layer, 80-p-type AlGaN confinement layer, 90-contact layer. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0026] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] Figure 1 This is a schematic flowchart illustrating a method for fabricating a GaN-based green laser according to an embodiment of the present invention. Figure 2 This is a schematic structural diagram of a GaN-based green laser according to an embodiment of the present invention.

[0029] like Figure 1 As shown, the present invention provides a GaN-based green laser 100 (refer to...). Figure 2 The preparation method of ) includes: Step S100: A buffer layer 20 and an n-type AlGaN confinement layer 30 are sequentially deposited on the substrate layer 10. The n-type AlGaN confinement layer 30 includes a first sub-layer and a second sub-layer disposed sequentially. The first sub-layer abuts against the buffer layer 20. The Al content of the first sub-layer is higher than that of the second sub-layer. The difference in Al content between the first sub-layer and the second sub-layer is any value between 3% and 6%. That is, the difference in Al content between the first sub-layer and the second sub-layer can be 3%, 4%, 5% or 6%, or any other value between 3% and 6%. Step S200: Sequentially deposit an n-type waveguide layer 40, a quantum well layer 50, a p-type waveguide layer 60, and an electron blocking layer 70 on the n-type AlGaN confinement layer 30; Step S300: A p-type AlGaN confinement layer 80 and a contact layer 90 are sequentially deposited on the electron blocking layer 70 to prepare a GaN-based green laser 100. The p-type AlGaN confinement layer 80 includes a third sublayer and a fourth sublayer sequentially disposed thereon. The fourth sublayer is in contact with the contact layer 90. The Al composition of the third sublayer is lower than that of the fourth sublayer, and the difference in Al composition between the third and fourth sublayers is any value between 3% and 7%. That is, the difference in Al composition between the third and fourth sublayers can be 3%, 4%, 5% or 7%, or any other value between 3% and 7%. In this design, the Al content in the first sublayer is any value between 6% and 12%, the Al content in the second sublayer is any value between 3% and 6%, the Al content in the third sublayer is any value between 4% and 8%, and the Al content in the fourth sublayer is any value between 6% and 12%. Specifically, the Al content in the first sublayer can be 6%, 7%, 8%, 9%, 10%, 11%, or 12%, or any other value between 6% and 12%; the Al content in the second sublayer can be 3%, 4%, 5%, or 6%, or any other value between 3% and 6%; the Al content in the third sublayer can be 4%, 5%, 6%, 7%, or 8%, or any other value between 4% and 8%; and the Al content in the fourth sublayer can be 6%, 8%, 10%, or 12%, or any other value between 6% and 12%.

[0030] This embodiment provides a method for fabricating a GaN-based green laser 100. The method includes: sequentially depositing a buffer layer 20 and an n-type AlGaN confinement layer 30 on a substrate layer 10. The n-type AlGaN confinement layer 30 includes a first sublayer and a second sublayer sequentially disposed thereon. The first sublayer abuts against the buffer layer 20. The Al composition of the first sublayer is higher than that of the second sublayer, and the difference in Al composition between the first sublayer and the second sublayer is any value between 3% and 6%, wherein the Al composition of the first sublayer is any value between 6% and 12%, and the Al composition of the second sublayer is any value between 3% and 6%. An n-type waveguide layer 40, a quantum well layer 50, a p-type waveguide layer 60, and an electron blocking layer 70 are sequentially deposited on the electron blocking layer 30. A p-type AlGaN confinement layer 80 and a contact layer 90 are sequentially deposited on the electron blocking layer 70. The p-type AlGaN confinement layer 80 includes a third sublayer and a fourth sublayer sequentially disposed thereon. The fourth sublayer abuts against the contact layer 90. The Al composition of the third sublayer is lower than that of the fourth sublayer, and the difference in Al composition between the third and fourth sublayers is any value between 3% and 7%, wherein the Al composition of the third sublayer is any value between 4% and 8%, and the Al composition of the fourth sublayer is any value between 6% and 12%.

[0031] In this embodiment, segmented Al composition control structures are constructed in the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80, respectively. A combination design of a low Al composition region near the waveguide layer and a high Al composition region far from the waveguide layer is formed along the epitaxial growth direction. This design ensures good lattice matching and epitaxial quality at the interface of the confinement layer, while simultaneously forming a higher refractive index barrier on the side far from the active region. This results in a high refractive index difference optical confinement structure within the overall structure. This structure increases the refractive index difference Δn while avoiding the stress accumulation and crystal defect problems associated with traditional overall Al composition increases, achieving compatibility between enhanced optical confinement and improved epitaxial quality. Furthermore, by controlling the optical field distribution through segmented structures, the optical field mode is moved away from the p-type high absorption region, thereby reducing internal optical losses and achieving a synergistic effect between improved optical confinement factor, suppressed optical leakage, and optimized material quality. Overall, this significantly improves the optoelectronic performance of the GaN-based green laser 100.

[0032] In this embodiment, the n-type AlGaN confinement layer 30 is segmented into a first sublayer and a second sublayer. The second sublayer, closer to the waveguide layer, uses a lower Al composition, while the first sublayer, farther from the waveguide layer, uses a higher Al composition. This improves the lattice matching at the interface, which helps reduce the interface defect density and enhances the epitaxial quality of the waveguide layer and quantum well layer 50. Simultaneously, the high Al composition molecular layer, farther from the active region, effectively reduces the refractive index, forming an optical barrier and enhancing the light field's reflectivity. By controlling the Al composition difference between the two sublayers within the range of 3%-6%, a balance between optical confinement capability and structural stability is achieved while ensuring that stress does not change excessively, thereby reducing light field leakage and improving the optical confinement factor.

[0033] In this embodiment, within the p-type AlGaN confinement layer 80, a segmented structure of a third and fourth sub-layer is employed. The third sub-layer, closer to the waveguide layer, maintains a lower Al composition, thereby reducing interfacial stress and improving epitaxial quality. Conversely, the fourth sub-layer, closer to the contact layer 90, employs a higher Al composition to further reduce the refractive index and enhance optical reflectivity. This segmented design allows for more rapid attenuation of the light field in the p-type region, effectively suppressing the propagation of the light field towards the p-type contact layer 90, thus significantly reducing optical absorption loss caused by Mg doping. By controlling the Al composition difference between the two sub-layers within the range of 3%-7%, excessive stress concentration is avoided while ensuring optical confinement effectiveness, thereby achieving synergistic optimization of optical performance and material reliability.

[0034] In this embodiment, by segmenting the composition of the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80, a large refractive index difference Δn is formed between the confinement layer and the waveguide layer, thereby significantly enhancing the confinement capability of the optical waveguide structure for the optical field. According to optical waveguide theory, the increase in refractive index difference accelerates the attenuation of evanescent waves in the confinement layer, making the optical field more concentrated in the active region of the quantum well and the waveguide layer region. This concentrates the optical field in the structure mainly near the active region, significantly reducing the proportion of the optical field in the p-type region, thereby effectively suppressing parasitic modes and optical leakage, and improving the optical utilization efficiency of the GaN-based green laser 100.

[0035] Compared to traditional confinement layer structures using a constant Al composition, this embodiment achieves a refractive index difference increase from less than 0.04 to greater than or equal to 0.05 through segmented control, thereby significantly enhancing optical confinement capability and noticeably improving the optical confinement factor in the multi-quantum-well active region, while reducing the trailing effect of the optical field in the p-type region. This not only reduces internal optical losses but also effectively suppresses thermal effects and the risk of catastrophic optical damage caused by light absorption, ultimately resulting in a lower threshold current, improved slope efficiency, and an overall improvement in device output performance.

[0036] In a further embodiment, the average Al composition of the p-type AlGaN confinement layer 80 is higher than that of the n-type AlGaN confinement layer 30, wherein the average Al composition is the average value of the Al composition of each sublayer weighted by its thickness. In this embodiment, by setting the average Al composition of the p-type AlGaN confinement layer 80 to be higher than that of the n-type AlGaN confinement layer 30, an asymmetric refractive index distribution structure is formed between the upper and lower confinement layers, thereby constructing an asymmetric optical potential well. This effectively reduces the light absorption loss caused by Mg doping, reduces internal optical loss while maintaining a high optical confinement factor, and thus achieves synergistic optimization between optical confinement capability and loss control.

[0037] In this embodiment, the increased Al content reduces the refractive index of the AlGaN material, resulting in a greater refractive index difference between the p-type waveguide layer 60 and the p-type AlGaN confinement layer 80 than between the n-type waveguide layer 40 and the n-type AlGaN confinement layer 30. This larger upper refractive index difference causes faster evanescent wave attenuation in the p-type direction, thus suppressing the extension of the light field into the p-type confinement layer and contact layer 90. The relatively smaller lower refractive index difference allows the light field to maintain a moderate expansion in the n-type region, enabling a controllable shift of the mode field distribution center towards the n-side. During this process, the light field remains primarily confined within the waveguide layer and quantum well region, with asymmetric adjustments only occurring at the edges. Consequently, the integral proportion of the light field in the p-type region is significantly reduced, effectively decreasing optical absorption loss caused by Mg doping and reducing internal optical losses. Simultaneously, since the overlap of the light field within the quantum well layer 50 region is not significantly reduced, a high optical confinement factor can still be maintained, achieving synergistic optimization between optical confinement capability and loss control.

[0038] Furthermore, by rationally controlling the difference in average Al composition between the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80, excessive mode field shift and structural stress imbalance can be avoided, thereby improving device efficiency while ensuring mode stability and structural reliability. Moreover, since Mg doping in the p-type region introduces a higher light absorption coefficient, its overlap integral in the p-type region is significantly reduced when the light field migrates to the n-type region, thus reducing light absorption loss and internal optical loss. Simultaneously, since the light field is still confined within the waveguide layer and quantum well region, leakage towards the n-type substrate layer 10 is not triggered, thus maintaining good optical confinement capability while reducing p-type region loss.

[0039] In a further embodiment, the average Al composition difference between the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80 is any value between 2% and 8%, that is, the average Al composition difference can be 2%, 3%, 4%, 5%, 6%, 7%, or 8%, or any other value between 2% and 8%. In this embodiment, by controlling the average Al composition difference between the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80 within the range of 2% to 8%, the intensity of the asymmetric optical potential well is kept within a reasonable controllable range, thereby achieving controllable adjustment of the optical field distribution. This allows for mode stability while ensuring a moderate shift in the optical field, ensuring that the optical field is mainly concentrated in the quantum well and waveguide layer regions, and as far away as possible from the high-absorption p-type region, thus achieving a balance between optical confinement capability and loss control. In addition, this range can also avoid stress asymmetry problems caused by excessive composition differences between the upper and lower confinement layers, thereby improving the structural stability and reliability of the GaN-based green laser 100.

[0040] In this embodiment, the average Al composition of the p-type AlGaN confinement layer 80 and the n-type AlGaN confinement layer 30 is an average value calculated by weighting the thickness of each sublayer, specifically according to the following formula: ; The total thickness is the sum of the thicknesses of all sublayers in a confinement layer. A single sublayer is a sublayer region divided along the thickness direction of the confinement layer. The Al component content of a single sublayer is the molar component content of Al element in Group III elements in that sublayer, that is, the molar percentage of Al in the total amount of Al and Ga elements.

[0041] In one embodiment, the n-type AlGaN confinement layer 30 includes a first sublayer and a second sublayer. The first sublayer has a thickness of 300 nm and an Al composition of 6%; the second sublayer has a thickness of 300 nm and an Al composition of 3%. The total thickness of the n-type AlGaN confinement layer is 600 nm. According to formula (1), the average Al composition of the n-type AlGaN confinement layer is 300 / 600×6%+300 / 600×3%=4.5%. Therefore, in this embodiment, the average Al composition of the n-type AlGaN confinement layer 30 is 4.5%. Similarly, the average Al composition of the p-type AlGaN confinement layer 80 can also be calculated according to formula (1) based on the thickness of each step layer and the corresponding Al composition content. In other embodiments, when the difference in average Al composition is small, the refractive index difference between the upper and lower confinement layers is close to symmetrical, the light field shift effect is not obvious, and it is difficult to effectively reduce the absorption loss in the p-type region; while when the difference is too large, it will cause the light field to shift excessively to the n-type region, which may cause unstable mode distribution and even increase the risk of leakage towards the substrate.

[0042] In a further embodiment, the thickness ratio of the first sublayer to the second sublayer is any value between 1 and 2.5, and the thickness ratio of the fourth sublayer to the third sublayer is any value between 0.75 and 2.0. That is, the thickness ratio of the first sublayer to the second sublayer can be 1, 1.5, 2, or 2.5, or any other value between 1 and 2.5, and the thickness ratio of the fourth sublayer to the third sublayer can be 0.75, 1.0, 1.5, or 2.0, or any other value between 0.75 and 2.0. In this embodiment, by controlling the thickness ratio of the first sublayer to the second sublayer to be between 1 and 2.5, and the thickness ratio of the fourth sublayer to the third sublayer to be between 0.75 and 2.0, and co-designing with the Al composition gradient distribution of each sublayer, the confinement layer maintains low stress and high crystal quality on the side near the waveguide layer, while forming a high barrier region with sufficient optical thickness on the side away from the waveguide layer. This achieves rapid attenuation and enhanced reflection of the light field in the confinement layer. Furthermore, by changing the equivalent refractive index distribution through thickness weighting, the light field always satisfies the total internal reflection condition of propagation from high refractive index to low refractive index during propagation, thereby effectively suppressing the leakage of the light field to the outside of the confinement layer.

[0043] Furthermore, the aforementioned thickness ratio range can also avoid stress accumulation problems caused by excessive thickness in high Al composition regions, achieving synergistic optimization of optical performance and material reliability.

[0044] In a further embodiment, the thickness of the n-type AlGaN confinement layer 30 is any value between 600nm and 1000nm, and the thickness of the p-type AlGaN confinement layer 80 is any value between 200nm and 400nm. That is, the thickness of the n-type AlGaN confinement layer 30 can be 600nm, 700nm, 800nm, 900nm, or 1000nm, or any other value between 600nm and 1000nm, and the thickness of the p-type AlGaN confinement layer 80 can be 200nm, 250nm, 300nm, 350nm, or 400nm, or any other value between 200nm and 400nm. In this embodiment, by controlling the thickness of the n-type AlGaN confinement layer 30 to be 600nm-1000nm and the thickness of the p-type AlGaN confinement layer 80 to be 200nm-400nm, and by reasonably setting the thickness of the p-type AlGaN confinement layer 80, the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80 have sufficient optical thickness to achieve effective attenuation of evanescent waves, thereby preventing the light field from leaking to the substrate or the p-type contact layer 90 region, while avoiding the p-type AlGaN confinement layer 80 being too thick to achieve material growth.

[0045] In a further embodiment, the growth rates of the p-type AlGaN confinement layer 80 and the n-type AlGaN confinement layer 30 are any values ​​between 0.5 μm / h and 1.5 μm / h. Specifically, the growth rate of the p-type AlGaN confinement layer 80 can be 0.5 μm / h, 1.0 μm / h, or 1.5 μm / h, or any other value within this range. Similarly, the growth rate of the n-type AlGaN confinement layer 30 can be 0.5 μm / h, 1.0 μm / h, or 1.5 μm / h, or any other value within this range. This ensures that the epitaxial growth process is under relatively stable kinetic conditions, thereby improving the controllability of the Al composition and the quality of the interlayer interface. Lower or moderate growth rates facilitate the effective incorporation of Al atoms, reducing compositional fluctuations and interface roughness, thereby reducing light scattering loss and improving overall optical performance.

[0046] In a further embodiment, the thickness of the n-type waveguide layer 40 is any value between 250nm and 300nm, and the thickness of the p-type waveguide layer 60 is any value between 180nm and 220nm. That is, the thickness of the n-type waveguide layer 40 can be 250nm, 260nm, 270nm, 280nm, 290nm, or 300nm, or any other value between 250nm and 300nm, and the thickness of the p-type waveguide layer 60 can be 180nm, 190nm, 200nm, 210nm, or 220nm, or any other value between 180nm and 220nm. By controlling the thickness of the n-type waveguide layer 40 to 250nm-300nm and the thickness of the p-type waveguide layer 60 to 180nm-220nm, the mode size and distribution of the optical waveguide structure are optimized. Since the thickness of the waveguide layer directly determines the spatial distribution range of the optical mode, a reasonable thickness can ensure that the optical field does not diffuse excessively to the confinement layer and can fully cover the active region, thereby maximizing the optical gain and increasing the degree of overlap of the optical field in the quantum well region, i.e., increasing the optical confinement factor Γ_MQW.

[0047] In a further embodiment, the quantum well layer 50 includes periodically arranged InGaN and GaN layers. When the thickness of the InGaN layer is 3 nm, the In composition in the InGaN layer is any value between 26% and 30%, that is, the In composition in the InGaN layer can be 26%, 27%, 29%, or 30%, or any other value between 26% and 30%. By controlling the In composition in the InGaN quantum well layer 50 within the range of 26%-30%, the device can stably achieve green light emission while avoiding lattice mismatch and lattice relaxation problems caused by excessively high In composition. Here, the wavelength of the green light band is 520 nm.

[0048] In a further embodiment, the substrate layer 10 is any one of a sapphire substrate, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate. The gallium nitride substrate has a high lattice matching degree with the epitaxial layer, which is beneficial to reducing dislocation density and improving device luminous efficiency. The silicon carbide substrate has high thermal conductivity, which is beneficial to device heat dissipation and improving high-power operation stability. The sapphire substrate has a mature process foundation and low cost, making it suitable for large-scale fabrication. The silicon substrate has the advantages of large size and low cost, which is beneficial to achieving compatibility with existing integrated circuit processes.

[0049] The present invention also provides a GaN-based green laser 100 prepared according to the above-described method for preparing a GaN-based green laser 100. The GaN-based green laser 100 includes a substrate layer 10, a buffer layer 20, an n-type AlGaN confinement layer 30, an n-type waveguide layer 40, a quantum well layer 50, a p-type waveguide layer 60, an electron blocking layer 70, a p-type AlGaN confinement layer 80, and a contact layer 90 arranged sequentially from bottom to top. In the GaN-based green laser 100, a refractive index difference greater than or equal to 0.05 is formed between the n-type AlGaN confinement layer 30 and the n-type waveguide layer 40, and between the p-type waveguide layer 60 and the p-type AlGaN confinement layer 80.

[0050] In this embodiment, a refractive index difference greater than or equal to 0.05 is formed between the n-type AlGaN confinement layer 30 and the n-type waveguide layer 40, and between the p-type waveguide layer 60 and the p-type AlGaN confinement layer 80, respectively, thereby constructing an optical confinement structure with a high refractive index difference on the upper and lower sides. Based on optical waveguide theory, a larger refractive index difference can significantly enhance the confinement capability of the light field in the waveguide layer and the active region of the quantum well, accelerate the attenuation of the evanescent wave in the confinement layer, and effectively suppress the leakage of the light field to the substrate and the p-type contact layer 90, thereby significantly improving the optical confinement factor, allowing more light energy to be concentrated in the multi-quantum-well active region to participate in stimulated emission, while reducing the distribution ratio of the light field in the high-absorption p-type region, thereby reducing the light absorption loss caused by free carriers and impurities.

[0051] Furthermore, a large refractive index difference is achieved on both the upper and lower sides, enabling the GaN-based green laser 100 to form a stable double-sided optical potential well structure. This ensures strong optical field confinement while maintaining the stability of the mode distribution, preventing mode diffusion or the generation of parasitic modes. Simultaneously, by combining this with the segmented Al composition design in this embodiment, the high refractive index difference structure and the asymmetric potential well work together to not only enhance optical confinement capabilities but also optimize the optical field distribution position. This results in increased light output efficiency while reducing the threshold current, achieving an overall performance improvement for the GaN-based green laser 100.

[0052] The technical solution of this application will be further described below with reference to specific embodiments.

[0053] In some embodiments, the fabrication method of the GaN-based green laser 100 includes the following steps: Step S100: A Si-doped AlGaN buffer layer 20 and an n-type AlGaN confinement layer 30 with a thickness of 1.3 μm are sequentially deposited on the substrate layer 10. The n-type AlGaN confinement layer 30 includes a first sub-layer and a second sub-layer disposed sequentially. The first sub-layer abuts against the buffer layer 20. The Al content of the first sub-layer is higher than that of the second sub-layer, and the difference in Al content between the first sub-layer and the second sub-layer is any value between 3% and 6%. Step S200: An n-type waveguide layer 40, a quantum well layer 50, a p-type waveguide layer 60, and an electron blocking layer 70 are sequentially deposited on the n-type AlGaN confinement layer 30. The n-type waveguide layer 40 is Si-doped GaN with a thickness of 290 nm. The quantum well layer 50 is composed of two periods of InGaN (3 nm) / GaN (8 nm) quantum wells. The In composition in the InGaN layer is 26%-30%. The p-type waveguide layer 60 is Mg-doped GaN with a thickness of 200 nm. The electron blocking layer 70 is Mg-doped AlGaN with a thickness of 10 nm. Step S300: A p-type AlGaN confinement layer 80 and a contact layer 90 are sequentially deposited on the electron blocking layer 70. The p-type AlGaN confinement layer 80 includes a third sub-layer and a fourth sub-layer sequentially disposed. The fourth sub-layer abuts against the contact layer 90. The Al composition of the third sub-layer is lower than that of the fourth sub-layer, and the difference in Al composition between the third and fourth sub-layers is any value between 3% and 7%. A GaN-based green laser 100 is thus fabricated. The first sublayer contains any value of Al between 6% and 12%, the second sublayer contains any value of Al between 3% and 6%, the third sublayer contains any value of Al between 4% and 8%, and the fourth sublayer contains any value of Al between 6% and 12%.

[0054] Example 1 The fabrication method of GaN-based green laser 100 includes the following steps: Step S100: A Si-doped AlGaN buffer layer 20 with a thickness of 1.3 μm and an n-type AlGaN confinement layer 30 with a thickness of 1 μm are sequentially deposited on the substrate layer 10. The n-type AlGaN confinement layer 30 includes a first sub-layer and a second sub-layer disposed sequentially. The first sub-layer abuts against the buffer layer 20. The Al composition of the first sub-layer is 10%, and the Al composition of the second sub-layer is 4%. Step S200: An n-type waveguide layer 40, a quantum well layer 50, a p-type waveguide layer 60, and an electron blocking layer 70 are sequentially deposited on the n-type AlGaN confinement layer 30. The n-type waveguide layer 40 is Si-doped GaN with a thickness of 290 nm. The quantum well layer 50 consists of two periods of InGaN / GaN quantum wells. The In composition of the InGaN layer is 26% to adjust the emission wavelength to 520 nm. The p-type waveguide layer 60 is Mg-doped GaN with a thickness of 200 nm. The electron blocking layer 70 is Mg-doped AlGaN with a thickness of 10 nm. Step S300: A p-type AlGaN confinement layer 80 with a thickness of 0.33 μm and a Mg-doped GaN contact layer 90 with a thickness of 150 nm are sequentially deposited on the electron blocking layer 70. The p-type AlGaN confinement layer 80 includes a third sublayer and a fourth sublayer sequentially disposed therefrom, with the fourth sublayer abutting against the contact layer 90. The Al composition of the third sublayer is 6%, and the Al composition of the fourth sublayer is 12% (the Al composition distribution in each structural layer is referred to...). Figure 3 ).

[0055] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the n-type AlGaN confinement layer 30 has a constant Al composition of 7%, and the p-type AlGaN confinement layer 80 has a constant Al composition of 7%.

[0056] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the Al component in both the first and second sublayers is 7%.

[0057] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the Al component is 7% in both the third and fourth sublayers.

[0058] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the Al composition of the first sublayer is 11% and the Al composition of the second sublayer is 3%.

[0059] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the Al composition of the first sublayer is 6% and the Al composition of the second sublayer is 4%.

[0060] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the Al composition of the third sublayer is 6% and the Al composition of the fourth sublayer is 8%.

[0061] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the Al composition of the third sublayer is 4% and the Al composition of the fourth sublayer is 12%.

[0062] Figure 3 This is a schematic diagram of the Al composition in a GaN-based green laser according to Embodiment 1 of the present invention. Figure 4 This is a schematic light field distribution diagram of the GaN-based green laser according to Embodiment 1 of the present invention. Figure 5 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser according to Embodiment 1 of the present invention. Figure 6 This is a schematic diagram of the Al composition in the GaN-based green laser according to Comparative Example 1 of the present invention. Figure 7 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 1 of the present invention. Figure 8 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 1 of the present invention. Figure 9 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 2 of the present invention. Figure 10 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 2 of the present invention. Figure 11 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 3 of the present invention. Figure 12 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 3 of the present invention. Figure 13 This is a schematic light field distribution diagram of the GaN-based green laser in Comparative Example 4 of the present invention. Figure 14 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 4 of the present invention. Figure 15 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 5 of the present invention. Figure 16 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 5 of the present invention. Figure 17 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 6 of the present invention. Figure 18 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 6 of the present invention. Figure 19 This is a schematic optical field distribution diagram of the GaN-based green laser in Comparative Example 7 of the present invention. Figure 20 This is a diagram of the optical field components along the epitaxial direction of the GaN-based green laser in Comparative Example 7 of the present invention.

[0063] Light field distribution tests were performed on Example 1 and Comparative Examples 1-7, and the results are shown in Table 1 and... Figures 3 to 20 The test results are shown.

[0064] Table 1. Optical field distribution results of GaN-based green lasers in Example 1 and Comparative Examples 1-7

[0065] Here, the total confinement factor is the total confinement factor of the optical field in the quantum well layer and the waveguide layer, the optical field component -p is the optical field component in the p-type region, and the optical field distribution ratio is the optical field distribution ratio between the n-type region and the p-type region.

[0066] From Table 1 and Figures 3 to 20 As can be seen, after employing a segmented Al composition control structure in both the n-type AlGaN confinement layer 30 and the p-type AlGaN confinement layer 80 in Example 1, the distribution ratio of the optical field in the quantum well layer 50 and the waveguide layer is significantly improved. Specifically, the multi-quantum well optical confinement factor Γ_MQW in Example 1 is 3.33%, and the total confinement factor Γ_WG+MQW is 90.64%, indicating that the optical field can be well concentrated within the effective optical region formed by the quantum well layer 50 and the upper and lower waveguide layers. Meanwhile, the optical field component in the p-type region in Example 1 is 15.15%, and the optical field distribution ratio between the n-type and p-type regions is 5.096, indicating that while maintaining high effective confinement, the optical field does not significantly extend into the p-type high absorption region, thus reducing the optical absorption loss caused by the p-type doping region.

[0067] Compared to Comparative Example 1, the Γ_MQW of Example 1 increased from 2.10% to 3.33%, the Γ_WG+MQW increased from 85.24% to 90.64%, the p-type region optical field component decreased from 31.61% to 15.15%, and the ratio of the n-type to p-type region optical field distribution increased from 1.991 to 5.096. These results demonstrate that, compared to a structure with constant Al composition in the upper and lower confinement layers, Example 1, by introducing a segmented Al composition distribution in the upper and lower AlGaN confinement layers, can maintain a lower Al composition near the waveguide layer to improve interface quality, and set a higher Al composition away from the waveguide layer to increase the refractive index barrier, thereby simultaneously achieving optical field concentration and p-type region leakage suppression. Figure 4 , Figure 5 and Figure 7 , Figure 8 The comparison shows that the light field distribution in Example 1 is more concentrated in the quantum well layer 50 and waveguide layer region, and the tailing along the epitaxial direction toward the p-type contact layer 90 side is significantly weakened.

[0068] Comparative Example 2 uses the same Al composition for the first and second sublayers of the n-type AlGaN confinement layer 30, with a Γ_MQW of 1.355% and a Γ_WG+MQW of 29.87%. Comparative Example 3 uses the same Al composition for the third and fourth sublayers of the p-type AlGaN confinement layer 80, with a Γ_MQW of 1.246% and a Γ_WG+MQW of 27.88%. Although the p-type region optical field components in Comparative Examples 2 and 3 are 8.048% and 7.833%, respectively, which are lower than in Example 1, their total confinement factor decreases significantly, indicating that the optical field is not effectively maintained within the effective working region formed by the quantum well layer 50 and the waveguide layer. Therefore, segmenting the confinement layer on one side or only reducing the p-type region optical field component cannot achieve superior device optical performance. Only when the Al composition distributions of the upper and lower confinement layers are synergistically matched can a high level of effective optical confinement be maintained while reducing the absorption loss in the p-type region.

[0069] In Comparative Example 4, the Al composition difference between the first and second sublayers is too large, with Γ_MQW at 1.215% and Γ_WG+MQW at 29.20%. In Comparative Example 5, the Al composition difference between the first and second sublayers is too small, with Γ_MQW at 1.79% and Γ_WG+MQW at 40.00%. These results indicate that the Al composition difference between the first and second sublayers in the n-type AlGaN confinement layer 30 is not necessarily better the larger or smaller it is. When the difference is too large, the abrupt change in refractive index distribution between the side near and far from the waveguide layer is too strong, easily causing the light field distribution to deviate from the effective confinement range of the quantum well layer 50 and the waveguide layer. When the difference is too small, the n-type confinement layer cannot form a sufficient refractive index barrier, and the confinement capability of the light field within the effective optical region is still insufficient. Example 1 controls the Al composition difference between the first and second sublayers to 6%, achieving a better balance between interface stress control and refractive index barrier construction.

[0070] In Comparative Example 6, the Al composition difference between the third and fourth sublayers is relatively small, with Γ_MQW at 1.208% and Γ_WG+MQW at 28.36%. In Comparative Example 7, the Al composition difference between the third and fourth sublayers is relatively large, with Γ_MQW at 1.405% and Γ_WG+MQW at 33.94%. These results indicate that the Al composition difference between the third and fourth sublayers in the p-type AlGaN confinement layer 80 also needs to be within a reasonable range. If the difference is too small, the p-type confinement layer will struggle to form a sufficiently high upper refractive index barrier, which is detrimental to effectively compressing the p-type optical field tail. If the difference is too large, although it can further reduce the p-type optical field component, it can easily cause excessive mode field shift or a decrease in the proportion of the optical field within the effective working region. In Example 1, the third sublayer Al composition is 6% and the fourth sublayer Al composition is 12%, which creates strong optical confinement on the p side while still maintaining 90.64% of Γ_WG+MQW. This indicates that the composition difference can balance p-side leakage suppression and effective region optical field preservation.

[0071] Further comparison of Example 1 with Comparative Examples 2 to 7 shows that although the p-type region optical field components of some samples in Comparative Examples 2 to 7 are lower than those in Example 1, their Γ_MQW and Γ_WG+MQW are significantly lower than those in Example 1. The results indicate that this application moderately reduces the proportion of the p-type region optical field distribution while ensuring that the optical field is mainly concentrated in the quantum well layer 50 and the waveguide layer. If only the reduction of the p-type region optical field components is pursued, it may cause the main optical field to deviate from the effective gain region, reducing the overall confinement factor, which is detrimental to obtaining a high modal gain for the laser. Furthermore, combined with... Figures 3 to 20 The optical field distribution and component diagrams further confirm that the Al-component segmented structure of Example 1 can keep the main optical field near the quantum well layer 50 and the waveguide layer, and suppress the optical field tailing in the p-type region. However, in each comparative example, due to the elimination of a segment on one side, excessively small component differences, or excessively large component differences, the refractive index distribution matching relationship between the upper and lower confinement layers is disrupted to varying degrees, making it difficult for the optical field to simultaneously meet the requirements of high Γ_MQW, high Γ_WG+MQW, and low p-type region leakage.

[0072] In summary, this application achieves a synergistic effect between optical barrier construction, interface stress control, and asymmetric optical field modulation by segmentally controlling the Al composition of the first and second sublayers in the n-type AlGaN confinement layer 30 and the third and fourth sublayers in the p-type AlGaN confinement layer 80, while keeping the composition difference between the upper and lower confinement layers within a reasonable range. This structure not only improves the optical confinement factor of the multi-quantum-well active region and the total confinement factor of the quantum well / waveguide region, but also reduces the proportion of the optical field distribution in the p-type region, thereby helping to reduce absorption loss in the p-type region and improve the output efficiency and operational stability of the GaN-based green laser 100.

[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for fabricating a GaN-based green laser, characterized in that, include: A buffer layer and an n-type AlGaN confinement layer are sequentially deposited on a substrate. The n-type AlGaN confinement layer includes a first sub-layer and a second sub-layer disposed sequentially. The first sub-layer abuts against the buffer layer. The Al content of the first sub-layer is higher than that of the second sub-layer, and the difference in Al content between the first sub-layer and the second sub-layer is any value between 3% and 6%. An n-type waveguide layer, a quantum well layer, a p-type waveguide layer, and an electron blocking layer are sequentially deposited on the n-type AlGaN confinement layer. A p-type AlGaN confinement layer and a contact layer are sequentially deposited on the electron blocking layer to fabricate the GaN-based green laser. The p-type AlGaN confinement layer includes a third sub-layer and a fourth sub-layer sequentially disposed thereon. The fourth sub-layer abuts against the contact layer. The Al composition of the third sub-layer is lower than that of the fourth sub-layer, and the difference in Al composition between the third and fourth sub-layers is any value between 3% and 7%. The first sublayer has an Al content of any value between 6% and 12%, the second sublayer has an Al content of any value between 3% and 6%, the third sublayer has an Al content of any value between 4% and 8%, and the fourth sublayer has an Al content of any value between 6% and 12%.

2. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The average Al composition of the p-type AlGaN confinement layer is higher than that of the n-type AlGaN confinement layer, wherein the average Al composition is the average value of the Al composition of each sublayer weighted by its thickness.

3. The method for fabricating a GaN-based green laser according to claim 2, characterized in that, The average Al component difference is any value between 2% and 8%.

4. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The thickness ratio of the first sublayer to the second sublayer is any value between 1 and 2.5, and the thickness ratio of the fourth sublayer to the third sublayer is any value between 0.75 and 2.

0.

5. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The thickness of the n-type AlGaN confinement layer is any value between 600nm and 1000nm, and the thickness of the p-type AlGaN confinement layer is any value between 200nm and 400nm.

6. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The growth rate of the p-type AlGaN confinement layer and the n-type AlGaN confinement layer is any value between 0.5 μm / h and 1.5 μm / h.

7. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The thickness of the n-type waveguide layer is any value between 250nm and 300nm, and the thickness of the p-type waveguide layer is any value between 180nm and 220nm.

8. The method for fabricating a GaN-based green laser according to any one of claims 1-7, characterized in that, The quantum well layer comprises an InGaN layer and a GaN layer arranged in a periodic manner, wherein the In composition of the InGaN layer is any value between 26% and 30%.

9. The method for fabricating a GaN-based green laser according to claim 1, characterized in that, The substrate is any one of sapphire substrate, silicon carbide substrate, silicon substrate or gallium nitride substrate.

10. A GaN-based green laser prepared by a method according to any one of claims 1-9, characterized in that, The GaN-based green laser comprises, from bottom to top, a substrate layer, a buffer layer, an n-type AlGaN confinement layer, an n-type waveguide layer, a quantum well layer, a p-type waveguide layer, an electron blocking layer, a p-type AlGaN confinement layer, and a contact layer, wherein a refractive index difference greater than or equal to 0.05 is formed between the n-type AlGaN confinement layer and the n-type waveguide layer, and between the p-type waveguide layer and the p-type AlGaN confinement layer.

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