Buried dielectric type gallium nitride-based photonic crystal laser and preparation method thereof

Abstract

The application belongs to the field of lasers and photonic devices, and particularly relates to a buried dielectric type GaN-based photonic crystal laser and a preparation method thereof. The laser comprises a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer and a p-type GaN layer; the p-type GaN layer is provided with a p-electrode on the surface, and the n-type GaN layer is provided with an n-electrode on the surface; and the p-type GaN layer is provided with an array of dielectric columns or dielectric holes. The application realizes the buried dielectric column or dielectric hole as a photonic crystal layer structure, which can realize different refractive index regulation, and the preparation process is more simple and convenient; through the direct coupling design of the photonic crystal and the quantum well active layer, combined with the optimized layer structure design, the efficient resonant coupling of the active layer and the photonic crystal layer can be realized, which is beneficial to realize the low threshold and high efficiency laser resonance, and the GaN-based photonic crystal laser with high performance and high reliability is prepared.

Description

Technical Field

[0001] This invention belongs to the field of lasers and photonic devices, specifically relating to a buried dielectric gallium nitride-based photonic crystal laser and its fabrication method. Background Technology

[0002] Photonic crystal lasers, with their advantages such as compact, high-quality resonance, low divergence angle, and high beam quality brought about by two-dimensional feedback mechanisms, have become an important development direction for next-generation high-performance laser sources. These devices mainly encompass two implementation paths: one is a non-defective photonic crystal laser (PCSEL) that utilizes the band-edge modes of a photonic crystal to achieve large-area uniform lasing; the other is a defective photonic crystal laser (LEAP) that introduces point or line defects into the photonic crystal to form a high-Q microcavity, thereby achieving low-threshold, dynamic single-mode lasing. Both have demonstrated enormous application potential in cutting-edge fields such as lidar, high-speed optical communication, and micro-projection.

[0003] Gallium nitride (GaN), a representative of third-generation semiconductor materials, is an ideal platform for fabricating high-performance photonic crystal lasers in the visible light band. Its wide bandgap characteristics provide an excellent material basis for blue-green and ultraviolet lasers, and are expected to achieve performance breakthroughs in fields such as displays, storage, and communications.

[0004] However, the performance of both PCSELs and LEAPs is highly dependent on the fabrication of high-quality photonic crystal structures. Existing GaN-based technologies mainly fall into two categories: one is surface-type photonic crystal structures, whose dry etching process not only limits electrode design and carrier injection efficiency but also easily leads to laser performance degradation; the other is buried air-hole structures, which, while solving surface problems, require extremely complex and expensive hole protection and secondary epitaxial processes. Furthermore, lattice damage and interface defects are inevitably introduced during etching and regrowth, exacerbating light scattering losses and non-radiative recombination. In addition, high-temperature secondary epitaxy easily induces quantum well active region degradation and wavelength drift, severely restricting the device's photoelectric conversion efficiency and operational stability. Particularly for defect-state lasers, process variations are particularly sensitive to the size and morphology of the defect cavity, further increasing the difficulty and uncertainty of high-performance device fabrication. Besides the aforementioned process challenges, both of these traditional structures rely on a fixed refractive index difference between air and GaN, lacking flexible control methods, thus limiting the laser's design freedom and performance ceiling.

[0005] Therefore, it is of great significance to develop a new buried dielectric gallium nitride-based photonic crystal laser. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a gallium nitride-based laser and its fabrication method based on a photonic crystal layer formed by a buried dielectric structure. Through innovative dielectric pillar or dielectric hole design and novel fabrication processes, low-threshold, high-efficiency, and high-performance photolasing is achieved.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] The first aspect of this invention discloses a buried dielectric gallium nitride-based photonic crystal laser, which includes: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer; the surface of the p-type GaN layer is provided with a p electrode, and the surface of the n-type GaN layer is provided with an n electrode;

[0009] The p-type GaN layer contains a dielectric pillar array or a dielectric hole array; the arrangement lattice type of the dielectric pillar array or dielectric hole array includes any one of a square lattice, a triangular lattice, and a honeycomb lattice.

[0010] In some embodiments of the present invention, the arrangement lattice of the dielectric pillar array or dielectric hole array is a square lattice.

[0011] In some embodiments of the present invention, the buried dielectric gallium nitride-based photonic crystal laser is a defect-type gallium nitride-based photonic crystal laser based on a dielectric pillar or a dielectric aperture (LEAP) or a non-defect-type gallium nitride-based photonic crystal laser based on a dielectric pillar or a dielectric aperture (PCSEL).

[0012] The dielectric pillar array includes any one of SiO2 dielectric pillar array, SiN dielectric pillar array, and TiO2 dielectric pillar array, and the dielectric pillar array is surrounded by p-type GaN; the dielectric hole array is a p-type GaN pillar, which is surrounded by any one of SiO2, SiN, and TiO2 dielectrics.

[0013] In some embodiments of the present invention, the dielectric pillar array is a SiO2 dielectric pillar array or a SiN dielectric pillar array, and the dielectric pillar array is surrounded by p-type GaN; the dielectric via array is a p-type GaN pillar, and is surrounded by SiO2 or SiN dielectric.

[0014] The dielectric pillar array has a pillar diameter of 50-150 nm, an array period of 180-300 nm, and a height of 50-300 nm; the dielectric aperture array has an aperture diameter of 50-250 nm, an array period of 180-300 nm, and a height of 50-300 nm.

[0015] In some embodiments of the present invention, the buried dielectric gallium nitride-based photonic crystal laser is a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pillars; wherein, the SiO2 dielectric pillar array is arranged in a square lattice, the pillar diameter is 100nm, the period is 220nm, and the height is 100nm; a single-point defect design is adopted, taking the single dielectric pillar at the geometric center of the array as the reference center position, removing the central dielectric pillar and its six adjacent dielectric pillars, for a total of seven dielectric pillars, thereby forming a defect microcavity, the equivalent diameter of which is 750nm.

[0016] In some embodiments of the present invention, the buried dielectric gallium nitride-based photonic crystal laser is a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric holes; wherein, the SiO2 dielectric hole array is arranged in a square lattice, with a hole diameter of 200nm, a period of 230nm, and a height of 150nm; a single-point defect design is adopted, taking the single dielectric hole at the geometric center of the array as the reference center position, removing the central dielectric hole and its six adjacent dielectric holes, for a total of seven dielectric holes are removed, thereby forming a defect microcavity.

[0017] In some embodiments of the present invention, the buried dielectric gallium nitride-based photonic crystal laser is a non-defect gallium nitride-based photonic crystal laser based on SiN dielectric pillars; wherein, the SiN dielectric pillar array is arranged in a square lattice, with a pillar diameter of 140 nm, a period of 200 nm, and a height of 150 nm.

[0018] In some embodiments of the present invention, the buried dielectric gallium nitride-based photonic crystal laser is a non-defect gallium nitride-based photonic crystal laser based on SiN dielectric holes; wherein, the SiN dielectric hole array is arranged in a square lattice, with a hole diameter of 180 nm, a period of 200 nm, and a height of 150 nm.

[0019] In the buried dielectric gallium nitride-based photonic crystal laser, the bottom GaN layer has a thickness of 1500~5000nm and a refractive index of 2.4~2.49; the n-type GaN layer has a thickness of 200~1200nm and a refractive index of 2.4~2.49; the n-type AlGaN layer has a thickness of 100~1000nm, a refractive index of 2.25~2.45, and an Al content of 15%~20%; the quantum well active layer is a 3~8 layer multi-quantum well structure composed of InGaN / GaN pairs; the p-type AlGaN layer has a thickness of 15~20nm, a refractive index of 2.35~2.45, and an Al content of 10%~18%; and the p-type GaN layer has a thickness of 100~1500nm and a refractive index of 2.4~2.49.

[0020] In some embodiments of the present invention, the thickness of the bottom GaN layer is 2000~3000nm; the thickness of the n-type GaN layer is 200~1200nm; the thickness of the n-type AlGaN layer is 500~1000nm; the quantum well active layer is a 3~8 layer multi-quantum well structure composed of InGaN / GaN pairs; the thickness of the p-type AlGaN layer is 15~20nm; and the thickness of the p-type GaN layer is 300~500nm.

[0021] In the quantum well active layer, each cycle includes: In x Ga 1-x N-well layer, x=0.15~0.25, thickness 2~3.5nm, refractive index 2.55~2.65; GaN barrier layer, thickness 8~12nm, refractive index 2.4~2.49.

[0022] In some embodiments of the present invention, each cycle of the quantum well active layer includes: In 0.18 Ga 0.82 N-well layer, thickness 2~3.5nm, refractive index 2.55~2.65; GaN barrier layer, thickness 8~12nm, refractive index 2.4~2.49.

[0023] The p electrode is a Ti / Pt / Au composite metal electrode; the n electrode is a Ti / Al / Ni / Au composite metal electrode.

[0024] A second aspect of this invention provides a method for fabricating a buried dielectric gallium nitride-based photonic crystal laser, comprising the following steps:

[0025] Step 1: Epitaxially grow the bottom GaN layer, n-type GaN layer, n-type AlGaN layer, quantum well active layer and p-type AlGaN layer sequentially on the substrate, and grow the p-type GaN layer for the first time;

[0026] Step 2: Deposit a dielectric layer on the surface of the first-grown p-type GaN layer, spin-coat photoresist on the surface of the dielectric layer, and then fabricate a photoresist mask array;

[0027] Step 3: Using photoresist as a mask, etch the dielectric layer, and use an organic solvent to dissolve and remove the surface photoresist to form a buried dielectric pillar array or dielectric via array;

[0028] Step 4: Perform secondary epitaxy to continue the secondary growth of p-type GaN until a complete p-type GaN layer is formed;

[0029] Step 5: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching to prepare n-electrodes on the surface of the n-GaN layer.

[0030] In step 1, the thickness of the first-growth p-type GaN layer is 10% to 40% of that of the complete p-type GaN layer.

[0031] In some embodiments of the present invention, when preparing a dielectric pillar array, in step 1, the thickness of the first-grown p-type GaN layer is 16.7% to 40% of the thickness of the complete p-type GaN layer; when preparing a dielectric via array, in step 1, the thickness of the first-grown p-type GaN layer is 10% to 33% of the thickness of the complete p-type GaN layer.

[0032] In step 2, the deposition method includes any one of atomic layer deposition, magnetron sputtering, and electron beam evaporation.

[0033] In some embodiments of the present invention, in step 2, the deposition method is atomic layer deposition or plasma-enhanced chemical vapor deposition.

[0034] In step 2, the method used to prepare the photoresist to form the mask array includes any one of electron beam lithography, ultraviolet lithography, and nanoimprint lithography.

[0035] In some embodiments of the present invention, in step 2, the method used to prepare the photoresist columnar array is electron beam lithography or ultraviolet lithography.

[0036] In some embodiments of the present invention, the working principle of the device is as follows: when the frequency of the light emitted by the active layer satisfies the bandgap condition of the photonic crystal, the wavelength resonates in the plane of the photonic crystal to generate a standing wave. The standing wave interacts with the active layer to form a gain, and oscillates under the population inversion condition to generate laser light.

[0037] Beneficial effects:

[0038] 1. This invention utilizes the refractive index modulation characteristics of buried dielectric arrays (SiO2 / SiN / TiO2) to form different refractive index differences with GaN, thereby improving the design flexibility of the resonant cavity and realizing different cavity characteristics; the low refractive index difference between the dielectric and gallium nitride makes it easier to achieve lower loss resonance, and its quality factor is improved by about one order of magnitude.

[0039] 2. By selectively achieving the relative positions of the photonic crystal layer and the active layer through process control, and by significantly increasing the overall refractive index of the photonic crystal region compared to the air hole, the coupling strength of the resonant optical field between the photonic crystal region and the quantum well active layer is improved. The coupling efficiency is increased by more than 40% compared to the traditional air hole structure, providing a foundation for achieving low threshold and high efficiency lasing.

[0040] 3. This invention employs epitaxial burial technology on dielectric materials to form a buried photonic crystal structure, resulting in a simple and low-cost fabrication process. Compared to the complex process of traditional burial of air holes, this invention avoids problems such as interface quality degradation due to air holes and an increase in non-radiative recombination centers. The roughness of the dielectric-semiconductor interface is on the nanometer scale, and the interface state density is reduced by an order of magnitude.

[0041] 4. This invention allows for flexible adjustment of refractive index contrast by selecting different dielectric materials (SiO2 / SiN / TiO2), adapting to different wavelengths and operating modes. Simultaneously, the dielectric pillar array or dielectric via array can support both band-edge and defect modes, greatly expanding the device's application range and design flexibility.

[0042] 5. Compared with traditional surface-etched photonic crystal holes, the present invention has superior electrical structure, carrier injection efficiency, and heat dissipation performance, which can significantly improve laser performance. Attached Figure Description

[0043] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0044] Figure 1 A schematic diagram of the defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pillars in Embodiment 1 of the present invention.

[0045] Figure 2 This is a top view of the SiO2 dielectric pillar array in Embodiment 1 of the present invention.

[0046] Figure 3 This is a schematic diagram of the defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pores in Embodiment 2 of the present invention.

[0047] Figure 4 This is a top view of the SiO2 dielectric pore array in Embodiment 2 of the present invention.

[0048] Figure 5 This is a schematic diagram of the structure of the non-defect gallium nitride-based photonic crystal laser based on SiN dielectric pillars in Embodiment 3 of the present invention.

[0049] Figure 6 This is a top view of the SiN dielectric pillar array in Embodiment 3 of the present invention.

[0050] Figure 7 This is a schematic diagram of the structure of the non-defect gallium nitride-based photonic crystal laser based on SiN dielectric holes in Embodiment 4 of the present invention.

[0051] Figure 8 This is a top view of the SiN dielectric hole array in Embodiment 4 of the present invention. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0053] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0054] Example 1:

[0055] This embodiment provides a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pillars. Figure 1 This is a schematic diagram of a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pillars. Specifically, it includes the following structure: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer. The p-type GaN layer contains an array of SiO2 dielectric pillars, and a p-electrode is located on its surface. The n-type GaN layer also has an n-electrode on its surface.

[0056] The bottom GaN layer has a thickness of 2800 nm and a refractive index of 2.45.

[0057] The n-type GaN layer has a thickness of 500 nm, a refractive index of 2.46, and a Si doping concentration of 5 × 10⁻⁶. 18 cm -3 ;

[0058] The n-type AlGaN layer is 500 nm thick, with an Al content of 15% and a refractive index of 2.41. The Si doping concentration is 1 × 10⁻⁶. 18 cm -3 ;

[0059] The active layer of the quantum well uses In 0.18 Ga 0.82 A three-period multi-quantum-well structure composed of N / GaN, wherein: the InGaN well layer has a thickness of 3.2 nm and a refractive index of 2.58, and the GaN barrier layer has a thickness of 10 nm and a refractive index of 2.45;

[0060] The p-type AlGaN layer has a thickness of 15 nm, an Al content of 18%, a refractive index of 2.38, and a Mg doping concentration of 5 × 10⁻⁶. 17 cm -3 ;

[0061] The p-type GaN layer has a thickness of 500 nm, a refractive index of 2.45, and a Mg doping concentration of 8 × 10⁻⁶. 17 cm -3 ;

[0062] The thickness of the p-electrode is 200 nm, and the material used is a Ti / Pt / Au composite metal electrode.

[0063] The thickness of the n-electrode is 200 nm, and the material used is a Ti / Al / Ni / Au composite metal electrode.

[0064] In the p-type GaN layer, the SiO2 dielectric pillar array is arranged in a square lattice, located at the center of the p-type GaN layer in the vertical direction. The pillars have a diameter of 100 nm, a period of 220 nm, and a height of 100 nm. Figure 2 This is a top view of a SiO2 dielectric pillar array, consisting of... Figure 2 As can be seen, this embodiment adopts a square lattice single-point defect design, taking the single dielectric pillar at the geometric center of the array as the reference center position, removing the central dielectric pillar and its six adjacent dielectric pillars, for a total of seven dielectric pillars removed, thereby forming a defect microcavity; Figure 2 This refers to the defect cavity region formed after removing 7 dielectric columns, with an equivalent diameter of 750 nm.

[0065] The fabrication process of the aforementioned defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pillars includes the following steps:

[0066] Step 1: On a sapphire substrate, a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a 200 nm thick p-type GaN layer are grown sequentially using metal-organic chemical vapor deposition (MOCVD) technology.

[0067] Step 2: A 100 nm thick SiO2 dielectric layer is deposited on the surface of the p-type GaN layer using atomic layer deposition (ALD) technology. Then, photoresist is spin-coated on the SiO2 dielectric layer, and a square lattice pattern containing point defects is prepared by electron beam lithography (EBL).

[0068] Step 3: ICP dry etching (Cl2 / BCl3 gas volume flow rate ratio 1:2, RF power 300W, bias voltage 100V) is used to etch the SiO2 dielectric layer using photoresist as a mask.

[0069] Step 4: Use an organic solvent to dissolve and remove the surface photoresist to form a buried SiO2 dielectric pillar array.

[0070] Step 5: Perform secondary epitaxy to continue growing p-type GaN until the surface is flat, and control the total thickness of the p-type GaN layer to be 500nm, completely covering the dielectric pillar array; at this time, the dielectric pillar array is a SiO2 dielectric pillar array, surrounded by p-type GaN.

[0071] Step 6: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching (etching depth to the n-GaN layer), and prepare n-electrodes on the surface of the n-GaN layer.

[0072] Example 2:

[0073] This embodiment provides a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pores. Figure 3 This is a schematic diagram of a defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric holes. The structure includes: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer. The p-type GaN layer contains an array of SiO2 dielectric holes, and a p-electrode is located on its surface. The n-type GaN layer has an n-electrode on its surface.

[0074] The bottom GaN layer has a thickness of 2800 nm and a refractive index of 2.45.

[0075] The n-type GaN layer has a thickness of 400 nm, a refractive index of 2.46, and a Si doping concentration of 5 × 10⁻⁶. 18 cm -3 ;

[0076] The n-type AlGaN layer is 800 nm thick, with an Al content of 15%, a refractive index of 2.41, and a Si doping concentration of 1 × 10⁻⁶. 18 cm -3 ;

[0077] The active layer of the quantum well uses In 0.18 Ga 0.82 A three-period multi-quantum-well structure composed of N / GaN, wherein: the InGaN well layer has a thickness of 3.2 nm and a refractive index of 2.58, and the GaN barrier layer has a thickness of 10 nm and a refractive index of 2.45;

[0078] The p-type AlGaN layer has a thickness of 15 nm, an Al content of 18%, a refractive index of 2.38, and a Mg doping concentration of 5 × 10⁻⁶. 17 cm -3 ;

[0079] The p-type GaN layer has a thickness of 450 nm, a refractive index of 2.45, and a Mg doping concentration of 8 × 10⁻⁶. 17 cm -3 ;

[0080] The thickness of the p-electrode is 150 nm, and the material used is a Ti / Pt / Au composite metal electrode.

[0081] The thickness of the n-electrode is 200 nm, and the material used is a Ti / Al / Ni / Au composite metal electrode.

[0082] The SiO2 dielectric pore array in the p-type GaN layer is arranged in a square lattice and is located at the center of the p-type GaN layer in the vertical direction. The pore diameter is 200 nm, the period is 230 nm, and the height is 150 nm.

[0083] Figure 4 This is a top view of the SiO2 dielectric pore array, by Figure 4 As can be seen, this embodiment adopts a square lattice single-point defect design, taking the single dielectric hole at the geometric center of the array as the reference center position, removing the central dielectric hole and its six adjacent dielectric holes, removing a total of seven dielectric holes, thereby forming a defect microcavity; Figure 4 This refers to the defect cavity region formed after removing the 7 medium holes.

[0084] The fabrication process of the aforementioned defect-type gallium nitride-based photonic crystal laser based on SiO2 dielectric pores includes the following steps:

[0085] Step 1: On a sapphire substrate, a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a 150 nm thick p-type GaN layer are grown sequentially using metal-organic chemical vapor deposition (MOCVD).

[0086] Step 2: A 150 nm thick SiO2 dielectric layer is deposited on the surface of the p-type GaN layer using atomic layer deposition (ALD) technology. Photoresist is then spin-coated onto the SiO2 dielectric layer, and a square lattice pattern containing point defects is prepared by electron beam lithography (EBL).

[0087] Step 3: ICP dry etching (Cl2 / BCl3 gas volume flow rate ratio 1:2, RF power 300W, bias voltage 100V) is used to etch the SiO2 dielectric layer using photoresist as a mask.

[0088] Step 4: Use an organic solvent to dissolve and remove the surface photoresist to form a buried SiO2 dielectric hole array.

[0089] Step 5: Perform secondary epitaxy to continue growing p-type GaN until the surface is flat, control the total thickness of the p-type GaN layer to 450nm, completely covering the dielectric hole array. At this time, p-type GaN pillars are formed in the dielectric hole array, surrounded by SiO2 dielectric layer.

[0090] Step 6: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching (etching depth to the n-GaN layer), and prepare n-electrodes on the surface of the n-GaN layer.

[0091] Example 3:

[0092] This embodiment provides a defect-free gallium nitride-based photonic crystal laser based on SiN dielectric pillars. Figure 5 This is a schematic diagram of a defect-free gallium nitride-based photonic crystal laser based on SiN dielectric pillars. The structure includes: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer. The p-type GaN layer contains an array of SiN dielectric pillars, and a p-electrode is located on its surface. The n-type GaN layer also has an n-electrode on its surface.

[0093] The bottom GaN layer has a thickness of 3000 nm and a refractive index of 2.46.

[0094] The n-type GaN layer has a thickness of 1200 nm, a refractive index of 2.47, and a Si doping concentration of 4 × 10⁻⁶. 18 cm -3 ;

[0095] The n-type AlGaN layer is 800 nm thick, with an Al content of 20%, a refractive index of 2.35, and a Si doping concentration of 7 × 10⁻⁶. 17 cm -3 ;

[0096] The active layer of the quantum well uses In 0.18 Ga 0.82 A 5-period multi-quantum-well structure composed of N / GaN, wherein: the InGaN well layer has a thickness of 2nm and a refractive index of 2.58, and the GaN barrier layer has a thickness of 8nm and a refractive index of 2.45;

[0097] The p-type AlGaN layer has a thickness of 20 nm, an Al content of 15%, a refractive index of 2.41, and a Mg doping concentration of 4 × 10⁻⁶. 17 cm -3 ;

[0098] The p-type GaN layer has a thickness of 300 nm, a refractive index of 2.46, and a Mg doping concentration of 6 × 10⁻⁶. 17 cm -3 ;

[0099] The thickness of the p-electrode is 200 nm, and the material used is a Ti / Pt / Au composite metal electrode.

[0100] The thickness of the n-electrode is 250 nm, and the material used is a Ti / Al / Ni / Au composite metal electrode.

[0101] In the p-type GaN layer, the SiN dielectric pillar array is arranged in a square lattice. The vertical distance from the top of the p-type AlGaN layer is 50 nm, the pillar diameter is 140 nm, the period is 200 nm, and the height is 150 nm. Figure 6 This is a top view of a SiN dielectric pillar array.

[0102] The fabrication process of the aforementioned defect-free gallium nitride-based photonic crystal laser based on SiN dielectric pillars includes the following steps:

[0103] Step 1: On a sapphire substrate, a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a 50 nm thick p-type GaN layer are grown sequentially using metal-organic chemical vapor deposition (MOCVD) technology.

[0104] Step 2: A 150 nm thick SiN dielectric layer (refractive index 2.0) is deposited on the surface of the p-type GaN layer using plasma-enhanced chemical vapor deposition (PECVD). Photoresist is then spin-coated onto the SiN dielectric layer, and a complete square lattice pattern is prepared using ultraviolet lithography.

[0105] Step 3: ICP dry etching (Cl2 / BCl3 gas volume flow rate ratio 1:1.8, RF power 280W, bias voltage 9V) is used to etch the SiN dielectric layer using photoresist as a mask.

[0106] Step 4: Use an organic solvent to dissolve and remove the surface photoresist to form a buried SiN dielectric pillar array.

[0107] Step 5: Perform secondary epitaxy to continue growing p-type GaN until the surface is flat, control the total thickness of the p-type GaN layer to 300nm, and completely cover the dielectric pillar array. At this time, the dielectric pillar array is a SiN dielectric pillar array, surrounded by p-type GaN.

[0108] Step 6: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching (etching depth to the n-GaN layer), and prepare n-electrodes on the surface of the n-GaN layer.

[0109] Example 4:

[0110] This embodiment provides a defect-free gallium nitride-based photonic crystal laser based on SiN dielectric pores. Figure 7 This is a schematic diagram of a defect-free gallium nitride-based photonic crystal laser based on SiN dielectric holes. The structure includes: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer. The p-type GaN layer contains an array of SiN dielectric holes, and a p-electrode is located on its surface. The n-type GaN layer has an n-electrode on its surface.

[0111] The bottom GaN layer has a thickness of 2000 nm and a refractive index of 2.46.

[0112] The n-type GaN layer has a thickness of 1000 nm, a refractive index of 2.47, and a Si doping concentration of 4 × 10⁻⁶. 18 cm -3 ;

[0113] The n-type AlGaN layer is 1000 nm thick, with an Al content of 20%, a refractive index of 2.35, and a Si doping concentration of 7 × 10⁻⁶. 17 cm -3 ;

[0114] The active layer of the quantum well uses In 0.18 Ga 0.82 A 5-period multi-quantum-well structure composed of N / GaN, wherein: the InGaN well layer has a thickness of 2nm and a refractive index of 2.58, and the GaN barrier layer has a thickness of 8nm and a refractive index of 2.45;

[0115] The p-type AlGaN layer has a thickness of 20 nm, an Al content of 15%, a refractive index of 2.41, and a Mg doping concentration of 4 × 10⁻⁶. 17 cm -3 ;

[0116] The p-type GaN layer has a thickness of 500 nm, a refractive index of 2.46, and a Mg doping concentration of 6 × 10⁻⁶. 17 cm -3 ;

[0117] The thickness of the p-electrode is 200 nm, and the material used is a Ti / Pt / Au composite metal electrode.

[0118] The thickness of the n-electrode is 200 nm, and the material used is a Ti / Al / Ni / Au composite metal electrode.

[0119] The SiN dielectric pore array in the p-type GaN layer is arranged in a square lattice, with a vertical distance of 50 nm from the top of the p-type AlGaN layer, a pore diameter of 180 nm, a period of 200 nm, and a height of 150 nm. Figure 8 This is a top view of the SiN dielectric hole array.

[0120] The fabrication process of the aforementioned defect-free gallium nitride-based photonic crystal laser based on SiN dielectric pores includes the following steps:

[0121] Step 1: On a sapphire substrate, a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a 50 nm thick p-type GaN layer are grown sequentially using metal-organic chemical vapor deposition (MOCVD) technology.

[0122] Step 2: A 150 nm thick SiN dielectric layer (refractive index 2.0) is deposited on the surface of the p-type GaN layer using plasma-enhanced chemical vapor deposition (PECVD). Photoresist is then spin-coated onto the SiN dielectric layer, and a complete square lattice pattern is prepared using ultraviolet lithography.

[0123] Step 3: ICP dry etching (Cl2 / BCl3 gas volume flow rate ratio 1:1.8, RF power 280W, bias voltage 9V) is used to etch the SiN dielectric layer using photoresist as a mask.

[0124] Step 4: Use an organic solvent to dissolve and remove the surface photoresist to form a buried SiN dielectric hole array.

[0125] Step 5: Perform secondary epitaxy to continue growing p-type GaN until the surface is flat, control the total thickness of the p-type GaN layer to 500nm, completely covering the dielectric hole array. At this time, p-type GaN pillars are formed in the dielectric hole array, surrounded by SiN dielectric layer.

[0126] Step 6: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching (etching depth to the n-GaN layer), and prepare n-electrodes on the surface of the n-GaN layer.

[0127] Comparative Example 1:

[0128] To characterize the advantages of the non-defect gallium nitride-based photonic crystal laser based on SiN dielectric holes in Example 4 over the traditional unburied dielectric air-hole photonic crystal laser, a control group with perfectly matched epitaxial structure, cavity length, and injection conditions was set up for FDTD optical field simulation and device performance comparison verification. The specific comparison conditions and test results are as follows:

[0129] To quantitatively verify the optical field coupling enhancement effect of the present invention, two sets of comparative samples were set up, with the only difference being the photonic crystal structure. Except for the photonic crystal channel structure, the epitaxial layer thickness, quantum well composition, cavity length, and electrode fabrication process of the two sets of samples were completely consistent. The optical field mode simulation was carried out using Lumerical FDTD software, and wafer fabrication and room temperature optoelectronic testing were completed.

[0130] 1. Control group (traditional all-air-hole photonic crystal laser)

[0131] Buried air holes were etched in the p-GaN layer, with the holes filled entirely with air. Simulation results showed that the optical field coupling efficiency between the photonic crystal and the quantum well active layer was 51.2%. The threshold current density of the fabricated device was 980 A / cm². 2Traditional air-hole grooves suffer significant lattice damage due to dry etching and ion bombardment, resulting in high interface defect density, substantial non-radiative recombination losses, and the absence of a complete native GaN substrate at the bottom of the groove. This makes secondary epitaxial growth prone to crystal defects such as voids and dislocations, leading to low device fabrication yield.

[0132] 2. Experimental group (dielectric aperture photonic crystal laser prepared in Example 4)

[0133] Under the same simulation test conditions as the control group, the optical field coupling efficiency between the photonic crystal and the quantum well active layer was improved to 72.1%, representing a 40.8% improvement in coupling efficiency compared to the control group. The corresponding threshold current density of the fabricated device decreased to 615 A / cm². 2 Under the same injection current, the optical output power is increased by 32%, which verifies the advantages of this structure in low threshold and high efficiency photolasing.

[0134] This invention provides a buried dielectric gallium nitride-based photonic crystal laser and its fabrication method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A buried dielectric gallium nitride-based photonic crystal laser, characterized in that, The buried dielectric gallium nitride-based photonic crystal laser comprises: a bottom GaN layer, an n-type GaN layer, an n-type AlGaN layer, a quantum well active layer, a p-type AlGaN layer, and a p-type GaN layer; the surface of the p-type GaN layer is provided with a p electrode, and the surface of the n-type GaN layer is provided with an n electrode; The p-type GaN layer contains a dielectric pillar array or a dielectric hole array; the arrangement lattice type of the dielectric pillar array or dielectric hole array includes any one of a square lattice, a triangular lattice, and a honeycomb lattice.

2. The buried dielectric gallium nitride-based photonic crystal laser according to claim 1, characterized in that, The dielectric pillar array includes any one of SiO2 dielectric pillar array, SiN dielectric pillar array, and TiO2 dielectric pillar array, and the dielectric pillar array is surrounded by p-type GaN; the dielectric hole array is a p-type GaN pillar, which is surrounded by any one of SiO2, SiN, and TiO2 dielectrics.

3. The buried dielectric gallium nitride-based photonic crystal laser according to claim 1 or 2, characterized in that, The diameter of the pillars in the dielectric pillar array is 50~150nm, the array period is 180~300nm, and the height is 50~300nm; the diameter of the holes in the dielectric aperture array is 50~250nm, the array period is 180~300nm, and the height is 50~300nm.

4. The buried dielectric gallium nitride-based photonic crystal laser according to claim 3, characterized in that, In the buried dielectric gallium nitride-based photonic crystal laser, the bottom GaN layer has a thickness of 1500-5000 nm and a refractive index of 2.4-2.49; the n-type GaN layer has a thickness of 200-1200 nm and a refractive index of 2.4-2.49; the n-type AlGaN layer has a thickness of 100-1000 nm, a refractive index of 2.25-2.45, and an Al content of 15%-20%; the quantum well active layer is a 3-8 layer multi-quantum well structure composed of InGaN / GaN pairs; the p-type AlGaN layer has a thickness of 15-20 nm, a refractive index of 2.35-2.45, and an Al content of 10%-18%; the p-type GaN layer has a thickness of 100-1500 nm and a refractive index of 2.4-2.49; wherein, in the quantum well active layer, each period includes: In x Ga 1-x N-well layer, x=0.15~0.25, thickness 2~3.5nm, refractive index 2.55~2.65; GaN barrier layer, thickness 8~12nm, refractive index 2.4~2.

49.

5. The buried dielectric gallium nitride-based photonic crystal laser according to claim 3, characterized in that, The p electrode is a Ti / Pt / Au composite metal electrode; the n electrode is a Ti / Al / Ni / Au composite metal electrode.

6. The method for fabricating a buried dielectric gallium nitride-based photonic crystal laser according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Epitaxially grow the bottom GaN layer, n-type GaN layer, n-type AlGaN layer, quantum well active layer and p-type AlGaN layer sequentially on the substrate, and grow the p-type GaN layer for the first time; Step 2: Deposit a dielectric layer on the surface of the first-grown p-type GaN layer, spin-coat photoresist on the surface of the dielectric layer, and then fabricate a photoresist mask array; Step 3: Using photoresist as a mask, etch the dielectric layer, and use an organic solvent to dissolve and remove the surface photoresist to form a buried dielectric pillar array or dielectric via array; Step 4: Perform secondary epitaxy to continue the secondary growth of p-type GaN until a complete p-type GaN layer is formed; Step 5: Prepare p-electrodes using photolithography and lift-off processes; then form mesa mesa surfaces using photolithography-dry etching to prepare n-electrodes on the surface of the n-GaN layer.

7. The preparation method according to claim 6, characterized in that, In step 1, the thickness of the first-growth p-type GaN layer is 10% to 40% of that of the complete p-type GaN layer.

8. The preparation method according to claim 7, characterized in that, When fabricating a dielectric pillar array, in step 1, the thickness of the first-grown p-type GaN layer is 16.7% to 40% of the thickness of the complete p-type GaN layer; when fabricating a dielectric via array, in step 1, the thickness of the first-grown p-type GaN layer is 10% to 33% of the thickness of the complete p-type GaN layer.

9. The preparation method according to claim 6, characterized in that, In step 2, the deposition method includes any one of atomic layer deposition, magnetron sputtering, and electron beam evaporation.

10. The preparation method according to claim 6, characterized in that, In step 2, the method used to prepare the photoresist mask array includes any one of electron beam lithography, ultraviolet lithography, and nanoimprint lithography.

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