Photonic crystal surface emitting laser and preparation method thereof

Abstract

The invention provides a photonic crystal surface emitting laser and a preparation method thereof, and the method comprises the steps: S1, providing a substrate, sequentially carrying out the epitaxial growth of an n-limiting layer, an n-waveguide layer, an active region and a photonic crystal layer on one side of the substrate in a first direction, and growing a DBR layer on the other side of the substrate in the first direction; s2, photoetching and etching the surface of the photonic crystal layer so as to etch in the photonic crystal layer to form a plurality of photonic crystal holes; s3, backfilling each photonic crystal hole in the photonic crystal layer by using a backfilling material; s4, a p-waveguide layer, a p-limiting layer and an ohmic contact layer are sequentially grown on the backfilled photonic crystal layer in a secondary epitaxial growth mode; s5, performing metal evaporation on the ohmic contact layer to form a p-electrode layer; and S6, thinning and polishing the surface of the DBR layer, and evaporating metal on the surface of the DBR layer to form an n-electrode layer.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a photonic crystal surface emitting laser and a preparation method thereof. Background Art

[0002] A photonic crystal surface emitting laser (PCSEL) is a new type of semiconductor surface emitting laser. By introducing a photonic crystal structure, there are high symmetry points with zero group velocity at the edge of the photonic crystal energy band, and stable standing wave resonances can be formed near the high symmetry points, thereby realizing surface emission. Compared with other semiconductor lasers, it has the advantages of small divergence angle, large-area coherent light coupling, and good spot quality.

[0003] In the actual preparation process of the photonic crystal surface emitting laser, the primary epitaxial process, the photolithography and etching processes of the photonic crystal layer may all deviate from the design values, causing the lasing wavelength to deviate from the ideal value. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the above deficiencies, the main object of the present invention is to provide a photonic crystal surface emitting laser and a preparation method thereof, to solve the deviation generated by the previous process, to realize the regulation of the lasing wavelength of the photonic crystal surface emitting laser, and to improve the process tolerance of the photonic crystal surface emitting laser.

[0006] (II) Technical Solutions

[0007] To achieve the above object, in a first aspect of the present invention, a preparation method of a photonic crystal surface emitting laser is provided, including: S1, providing a substrate, and epitaxially growing in sequence an n-cladding layer, an n-waveguide layer, an active region, and a photonic crystal layer on one side of the substrate along a first direction, and growing a DBR layer on the other side of the substrate along the first direction; S2, performing photolithography and etching on the surface of the photonic crystal layer to etch a plurality of photonic crystal holes in the photonic crystal layer; S3, backfilling each photonic crystal hole in the photonic crystal layer with a backfilling material; S4, epitaxially growing in sequence a p-waveguide layer, a p-cladding layer, and an ohmic contact layer on the backfilled photonic crystal layer; S5, evaporating metal on the ohmic contact layer to form a p-electrode layer; S6, thinning and polishing the surface of the DBR layer, and evaporating metal on the surface of the DBR layer to form an n-electrode layer.

[0008] In the above solution, S3 includes: backfilling each photonic crystal hole in the photonic crystal layer by controlling the refractive index and growth conditions of the backfilling material.

[0009] In the above solution, S3 further includes: backfilling each photonic crystal hole in the photonic crystal layer by using a material growth process, and the growth process includes MOCVD, MBE, and ALD.

[0010] In the above solution, S4 further includes: during the process of secondary epitaxial growth, making the p-waveguide layer and the p-confining layer match the optical and electrical characteristics of the photonic crystal layer.

[0011] In the above solution, the backfill material is a material with different refractive indexes, and the range of the refractive index is 1.0 to 3.5.

[0012] In the above solution, the material of the photonic crystal layer includes GaAs, InP, and AlGaAs.

[0013] In the above solution, multiple photonic crystal holes are arranged periodically.

[0014] In the above solution, the shapes of the photonic crystal holes include circular holes and triangular holes.

[0015] The second aspect of the present invention provides a photonic crystal surface emitting laser, including: a substrate; an n-confining layer, an n-waveguide layer, an active region, a photonic crystal layer, a p-waveguide layer, a p-confining layer ohmic contact layer, and a p-electrode layer are sequentially stacked on one side of the substrate along a first direction; a DBR layer is provided on the other side of the substrate along the first direction, and an n-electrode layer is provided on the surface of the DBR layer.

[0016] In the above solution, the photonic crystal layer includes multiple photonic crystal holes, and each photonic crystal hole is filled with a backfill material.

[0017] (III) Beneficial effects

[0018] The technical solution of the embodiment of the present invention has at least the following beneficial effects:

[0019] (1) Through the secondary epitaxial backfill process, the preparation method adjusts the deviation generated by the previous process to improve the process tolerance.

[0020] (2) Through the secondary epitaxial backfill process, the preparation method prepares a high-low refractive index periodic structure and adjusts the energy band near the Γ point, and an ideal lasing wavelength can be obtained.

[0021] (3) The photonic crystal surface emitting laser can adjust the lasing wavelength of the photonic crystal surface emitting laser by backfilling different refractive index materials in the holes, improve the process tolerance of the photonic crystal surface emitting laser, and accurately emit a lasing wavelength that has important application value in the fields of optical communication, sensors, etc. Description of the drawings

[0022] Figure 1Schematically shows a flowchart of a method for fabricating a photonic crystal surface emitting laser according to an embodiment of the present invention;

[0023] Figure 2 Schematically shows a cross-sectional view of a photonic crystal surface emitting laser according to an embodiment of the present invention;

[0024] Figure 3 Schematically shows a top view of a photonic crystal layer according to an embodiment of the present invention;

[0025] Figure 4 Schematically shows a top view schematic diagram after a photonic crystal hole backfilling process according to an embodiment of the present invention;

[0026] Figure 5 Schematically shows a band diagram of a PCSEL when the photonic crystal holes are air holes according to an embodiment of the present invention;

[0027] Figure 6 Schematically shows a band diagram of a PCSEL when a material with a refractive index of 3.0 is backfilled into a circular hole after a secondary backfilling process according to an embodiment of the present invention. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0029] Figure 1 Schematically shows a flowchart of a method for fabricating a photonic crystal surface emitting laser according to an embodiment of the present invention. Figure 2 Schematically shows a cross-sectional view of a photonic crystal surface emitting laser according to an embodiment of the present invention. Figure 3 Schematically shows a top view of a photonic crystal layer according to an embodiment of the present invention. Figure 4 Schematically shows a top view schematic diagram after a photonic crystal hole backfilling process according to an embodiment of the present invention.

[0030] As Figure 1 shown, the above-mentioned method for fabricating a photonic crystal surface emitting laser specifically includes operations S1 to S6.

[0031] In operation S1, a substrate 9 is provided, and an n-cladding layer 8, an n-waveguide layer 7, an active region 6, and a photonic crystal layer 5 are epitaxially grown in sequence on one side of the substrate 9 along the first direction X1, and a DBR layer 10 is grown on the other side of the substrate 9 along the first direction.

[0032] Exemplarily, as Figure 2As shown, on one side of the substrate 9 along the first direction X1, by using the metal organic chemical vapor deposition (MOCVD) process and optimizing parameters such as growth temperature, gas flow rate, and growth time, the n - confinement layer 8, n - waveguide layer 7, active region 6, and photonic crystal layer 5 are epitaxially grown in sequence. On the other side of the substrate 9 along the first direction X1, the DBR distributed Bragg reflector layer 10 is grown.

[0033] In operation S2, photolithography and etching are performed on the surface of the photonic crystal layer 5 to etch and form a plurality of photonic crystal holes 51 within the photonic crystal layer 5.

[0034] In an embodiment of the present invention, the lattice structure of the photonic crystals in the photonic crystal layer 5 includes a triangular lattice, a square lattice, or a hexagonal lattice.

[0035] Furthermore, photolithography is performed on the surface of the photonic crystal layer 5 of the above - mentioned epitaxial structure to form a pattern of the photonic crystal, and then through an etching process, such as electron beam exposure, etc., a plurality of photonic crystal holes 51 are etched out.

[0036] Exemplarily, as Figure 3 shown, the plurality of photonic crystal holes 51 are arranged periodically, and the shape of the photonic crystal holes 51 can be, for example, circular holes, and the diameters of the holes are the same.

[0037] Exemplarily, the shape of the photonic crystal holes 51 can also be triangular holes.

[0038] Exemplarily, the material of the photonic crystal layer 5 can be any one of GaAs, InP, and AlGaAs.

[0039] Exemplarily, the central point defect of the photonic crystal layer 5 can be a single - hole defect or a multi - hole defect.

[0040] In operation S3, each photonic crystal hole 51 in the photonic crystal layer 5 is backfilled with a backfill material.

[0041] Exemplarily, the backfill material is a material with different refractive indices, such as compounds like InN, SiC, etc., and the refractive index ranges from 1.0 to 3.5.

[0042] Exemplarily, before the photonic crystal holes 51 are filled, they are air holes. By utilizing the low refractive index characteristic of the air holes, a high - low refractive index difference is formed with the material of the photonic crystal layer 5, thereby realizing the regulation function of the photonic crystal. The air holes contribute to forming a uniform light field distribution in the photonic crystal and optimizing the optical characteristics of the photonic crystal layer.

[0043] In an embodiment of the present invention, the photonic crystal surface - emitting laser is a vertical - cavity surface - emitting laser. By optimizing the lattice constant and air - hole size of the photonic crystal layer 5, precise regulation of the lasing wavelength can be achieved.

[0044] Exemplarily, as Figure 4 shown, by using a material growth process such as MOCVD, MBE, ALD, etc., each photonic crystal hole 51 in the photonic crystal layer 5 is backfilled by controlling the refractive index and growth conditions of the backfill material.

[0045] In an embodiment of the present invention, MOCVD process is used for the backfill of secondary epitaxy. By optimizing the growth parameters, the refractive index of the backfill material is ensured to be 3.0, and the diameter of the photonic crystal hole 51 is reduced from 130 nm to 110 nm.

[0046] In an embodiment of the present invention, each photonic crystal hole 51 in the photonic crystal layer 5 is backfilled by controlling the refractive index and growth conditions of the backfill material. By precisely controlling the refractive index of the backfill material, the bandgap structure and optical field distribution of the photonic crystal layer are further optimized, so as to realize the regulation of the lasing wavelength.

[0047] In operation S4, on the backfilled photonic crystal layer 5, secondary epitaxial growth successively includes a p-waveguide layer 4, a p-confining layer 3, and an ohmic contact layer 2.

[0048] In an embodiment of the present invention, S4 further includes: during the process of secondary epitaxial growth, making the optical and electrical characteristics of both the p-waveguide layer 4 and the p-confining layer 3 match those of the photonic crystal layer 5.

[0049] Exemplarily, as Figure 2 shown, on the photonic crystal layer 5, a p-waveguide layer 4, a p-confining layer 3, and an ohmic contact layer 2 are successively epitaxially grown. By optimizing the epitaxial growth process, the optical and electrical characteristics of the p-waveguide layer 4 and the p-confining layer 3 are ensured to match those of the photonic crystal layer 5, thereby improving the overall performance of the laser.

[0050] In operation S5, metal is evaporated on the ohmic contact layer 2 to form a p-electrode layer 1.

[0051] Exemplarily, as Figure 2 shown, on the surface of the ohmic contact layer 2 of the above epitaxial structure, an electron beam evaporation technique is used to evaporate a layer of highly conductive metal material to form a p-electrode layer 1. By optimizing the electrode material and evaporation process, the conductivity and stability of the electrode are ensured.

[0052] In operation S6, the surface of the DBR layer 10 is thinned and polished, and metal is evaporated on the surface of the DBR layer 10 to form an n-electrode layer 11.

[0053] Exemplarily, as Figure 2As shown, the bottom of the DBR layer 10 is thinned and polished. After reducing the substrate thickness to a suitable range, a highly conductive metal material, such as Ti / Au alloy, is evaporated on the bottom to form the n - electrode layer 11, ensuring good contact between the electrode and the substrate and improving the current injection efficiency of the laser.

[0054] Figure 5 Schematically shows the energy band diagram of the PCSEL when the photonic crystal holes are air holes according to an embodiment of the present invention. Figure 6 Schematically shows the energy band diagram of the PCSEL when the material with a refractive index of 3.0 is backfilled in the circular holes after adopting the secondary backfilling process according to an embodiment of the present invention.

[0055] Through the embodiments of the present invention, the secondary epitaxial backfilling process in the preparation process of the photonic crystal surface - emitting laser is completed. The secondary epitaxial backfilling process for preparing the inner - cavity photonic crystal layer is the core process of the PCSEL. Through the secondary epitaxial backfilling process, different refractive index materials are backfilled in the photonic crystal holes to adjust the deviation generated by the previous primary process and prepare a high - low refractive index periodic structure. As Figure 5 and Figure 6 shown, through the secondary epitaxial backfilling process, the energy band near the Γ point can be adjusted, the process tolerance can be improved, and an ideal lasing wavelength can be obtained.

[0056] Based on the above - mentioned preparation method of the photonic crystal surface - emitting laser, an embodiment of the present invention provides a photonic crystal surface - emitting laser.

[0057] As Figure 2 shown, a photonic crystal surface - emitting laser includes: a substrate 9; an n - confinement layer 8, an n - waveguide layer 7, an active region 6, a photonic crystal layer 5, a p - waveguide layer 4, a p - confinement layer 3, an ohmic contact layer 2, and a p - electrode layer 1 are sequentially stacked on one side of the substrate 9 along the first direction X1; a DBR layer 10 is provided on the other side of the substrate 9 along the first direction X1, and an n - electrode layer 11 is provided on the surface of the DBR layer 10. As Figure 3 With Figure 4 shown, the photonic crystal layer 5 includes a plurality of photonic crystal holes 51, and each photonic crystal hole 51 has a backfill material.

[0058] Exemplarily, the material of the photonic crystal layer 5 is GaAs, whose bandgap energy matches the lasing wavelength of the laser and can effectively support the generation and amplification of light. In addition, the high refractive index characteristic of GaAs enables efficient optical field confinement and regulation in the photonic crystal structure.

[0059] Exemplarily, the refractive index of the backfill material can be 3.0.

[0060] Exemplarily, the lattice constant of the photonic crystal layer 5 is 277 nm.

[0061] Exemplarily, the lasing wavelength of the photonic crystal surface emitting laser can be adjusted to 940 nm.

[0062] Exemplarily, the lattice structure of the photonic crystal in the photonic crystal layer 5 is a square lattice. The square lattice structure has advantages such as high symmetry and strong optical modulation ability, and can achieve a significant optical bandgap at a relatively small lattice constant, thereby improving the performance and efficiency of the laser.

[0063] Through the embodiments of the present invention, the photonic crystal surface emitting laser can adjust the lasing wavelength of the photonic crystal surface emitting laser by backfilling different refractive index materials into the holes, improve the process tolerance of the photonic crystal surface emitting laser, and accurately emit a lasing wavelength that has important application values in the fields of optical communication, sensors, etc.

[0064] Those skilled in the art can understand that although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, those skilled in the art should understand that various changes in form and details can be made to the present invention without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents. Therefore, the scope of the present invention should not be limited to the above embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

[0065] The above specific embodiments have further elaborated on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a photonic crystal surface emitting laser, characterized in that: include: S1, providing a substrate (9), epitaxially growing an n-limiting layer (8), an n-waveguide layer (7), an active region (6) and a photonic crystal layer (5) in sequence on one side of the substrate (9) along a first direction, and growing a DBR layer (10) on the other side of the substrate (9) along the first direction; S2, performing photolithography and etching on the surface of the photonic crystal layer (5) to form a plurality of photonic crystal holes (51) by etching in the photonic crystal layer (5); S3, backfilling each of the photonic crystal holes (51) in the photonic crystal layer (5) using a backfill material; S4, secondary epitaxial growth on the backfilled photonic crystal layer (5) sequentially includes a p-waveguide layer (4), a p-confinement layer (3) and an ohmic contact layer (2); S5, evaporating metal on the ohmic contact layer (2) to form a p-electrode layer (1); S6, thinning and polishing the surface of the DBR layer (10), and evaporating metal on the surface of the DBR layer (10) to form an n-electrode layer (11).

2. The preparation method according to claim 1, characterized in that: The S3 includes: Each of the photonic crystal holes (51) in the photonic crystal layer (5) is backfilled by controlling the refractive index and growth conditions of the backfill material.

3. The preparation method according to claim 1 or 2, characterized in that: The S3 further includes: Each of the photonic crystal holes (51) in the photonic crystal layer (5) is backfilled using a material growth process, wherein the growth process includes MOCVD, MBE and ALD.

4. The preparation method according to claim 1 or 2, characterized in that: The S4 further comprises: During the secondary epitaxial growth process, the p-waveguide layer (4) and the p-limiting layer (3) are matched with the optical and electrical properties of the photonic crystal layer (5).

5. The preparation method according to claim 2, characterized in that: The backfill material is a material with different refractive indexes, and the refractive index ranges from 1.0 to 3.

5.

6. The preparation method according to claim 1 or 2, characterized in that: The material of the photonic crystal layer (5) includes GaAs, InP and AlGaAs.

7. The preparation method according to claim 2, characterized in that: The multiple photonic crystal holes (51) are arranged periodically.

8. The preparation method according to claim 2, characterized in that: The shapes of the photonic crystal holes (51) include circular holes and triangular holes.

9. A photonic crystal surface emitting laser, characterized in that: include: Substrate (9); An n-limiting layer (8), an n-waveguide layer (7), an active region (6), a photonic crystal layer (5), a p-waveguide layer (4), a p-limiting layer (3), an ohmic contact layer (2) and a p-electrode layer (1) are sequentially stacked on one side of the substrate (9) along the first direction; A DBR layer (10) is provided on the other side of the substrate (9) along the first direction, and an n-electrode layer (11) is provided on the surface of the DBR layer (10).

10. The photonic crystal surface emitting laser according to claim 9, characterized in that: The photonic crystal layer (5) comprises a plurality of photonic crystal holes (51), and each of the photonic crystal holes (51) contains a backfill material.

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