Epitaxial wafer with refractive index modulation structure and preparation method

Abstract

The invention provides an epitaxial wafer with a refractive index modulation structure and a preparation method, and relates to the technical field of semiconductor lasers. The epitaxial wafer comprises a substrate, a buffer layer, an N limiting layer, an N waveguide layer, a quantum well layer, a P waveguide layer, a P limiting layer and a cap layer are sequentially arranged on the substrate from bottom to top, and the N waveguide layer sequentially comprises an N passive waveguide layer, an N reverse waveguide layer and an N active waveguide layer in the direction away from the N limiting layer. Along the direction away from the N waveguide layer, the In content in the quantum well layer is gradually reduced, and the As content is gradually increased. The content of Al in the P waveguide layer is gradually increased in the direction away from the quantum well layer. According to the epitaxial wafer with the refractive index modulation structure and the preparation method provided by the invention, a high catastrophe optical damage (COD) threshold, high output power and high photoelectric conversion efficiency are ensured, and resistance and thermal resistance are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to an epitaxial wafer with a refractive index modulation structure and its preparation method. Background Technology

[0002] In recent years, high-power laser diodes (LDs) have seen significant performance improvements and are widely used in fiber lasers, solid-state lasers, infrared illumination, and other fields. These applications require the highest possible optical power, efficiency, and beam quality. To manufacture laser diodes that meet these requirements, their structural design must ensure a high catastrophic optical damage (COD) threshold, low internal optical loss, low thermal resistance (Rth), and low electrical resistance (Rs).

[0003] Currently, improving the COD threshold is typically achieved through modifications to the material system, laser end-face passivation, and coating techniques. Increasing the output power limit of a laser diode generally employs two methods: First, expanding the emitting area, which means increasing the effective thickness of the heterostructure waveguide. Second, broadening the optical field distribution in the direction perpendicular to the junction plane, usually achieved by widening the heterostructure waveguide or inserting a thin anti-waveguide layer between the waveguide layer and the confinement layer. Both of these approaches increase the thickness of the P-side confinement layer and / or waveguide layer, leading to increased resistance and thermal resistance, as well as increased light field penetration into the P-side, resulting in increased free carrier losses and consequently affecting the laser diode's power conversion efficiency. Summary of the Invention

[0004] To address the aforementioned issues, this application provides an epitaxial wafer with a refractive index modulation structure and its fabrication method, which not only ensures a high catastrophic optical damage (COD) threshold, high output power, and high photoelectric conversion efficiency, but also effectively reduces resistance and thermal resistance.

[0005] The technical solution adopted by this invention to solve its technical problem is: An epitaxial wafer with a refractive index modulation structure includes a substrate, on which a buffer layer, an N-confinement layer, an N-waveguide layer, a quantum well layer, a P-waveguide layer, a P-confinement layer and a cap layer are disposed sequentially from bottom to top. The N-waveguide layer includes an N-passive waveguide layer, an N-anti-waveguide layer and an N-active waveguide layer in sequence along the direction away from the N-confinement layer. Along the direction away from the N-waveguide layer, the In content in the quantum well layer gradually decreases, while the As content gradually increases. Along the direction away from the quantum well layer, the Al content in the P-waveguide layer gradually increases.

[0006] Furthermore, the material of the N-passive waveguide layer is Al. x2 Ga x2As, the value of x2 ranges from 0.2 to 0.5, and the doping concentration of the doped source in the N-passive waveguide layer is 2E16-1E17 atoms / cm². 3 The thickness of the N passive waveguide layer is 0.4-0.7 μm.

[0007] Furthermore, the material of the N-anti-waveguide layer is Al. x3 Ga 1-x3 As, the value range of x3 is 0.5≤x2≤0.8, the N-waveguide layer is unintentionally doped, and the thickness of the N-waveguide layer is 15-30nm.

[0008] Furthermore, the material of the N-type active waveguide layer is Al. x4 Ga 1-x4 As, x4 takes values ​​in the range of 0.2 ≤ x2 ≤ 0.5, the N active waveguide layer is unintentionally doped, and the thickness of the N active waveguide layer is 0.3-0.5 μm.

[0009] Furthermore, along the direction away from the N-waveguide layer, the material composition of the quantum well layer is changed from In... x5 Ga 1- x5 As y1 P 1-y1 Gradually becoming In x6 Ga 1-x6 As y2 P 1-y2 The values ​​of x5, x6, y1 and y2 are respectively 0.2≤x5≤0.6, 0.2≤x6≤0.6, 0.15≤y1≤0.3, and 0.15≤y2≤0.3.

[0010] Furthermore, the quantum well layer is unintentionally doped, and the thickness of the quantum well layer is 8-15 nm.

[0011] Furthermore, along the direction away from the quantum well layer, the material composition of the P-waveguide layer is composed of Al x7 Ga 1-x7 As gradually transforms into Al x8 Ga 1-x8 As, where the values ​​of x7 and x8 are in the range of 0.2≤x7≤0.5 and 0.2≤x8≤0.5.

[0012] Furthermore, the P-waveguide layer is unintentionally doped, and the thickness of the P-waveguide layer is 0.4-0.9 μm.

[0013] A method for preparing an epitaxial wafer with a refractive index modulation structure includes the following steps: S1. Place the substrate in the growth chamber of the MOCVD equipment, heat the H2 environment to 710-730℃ and bake for 20-40 minutes, then introduce AsH3 to perform high-temperature heat treatment on the substrate. S2, control the reaction chamber temperature to slowly decrease to 670±10℃, introduce TMGa and AsH3, and grow a buffer layer on the substrate; S3, the reaction chamber temperature is maintained at 670±10℃, TMAl, TMGa and AH3 are introduced, and an N-confined layer is grown on the buffer layer; S4, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N passive waveguide layer on the N confinement layer; S5, the reaction chamber temperature is maintained at 700±10℃, and TMAl, TMGa and AH3 are introduced to grow an N-anti-waveguide layer on the N-passive waveguide layer; S6, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N active waveguide layer on the N anti-waveguide layer; S7, the reaction chamber temperature is maintained at 670±10℃, and TMGa, TMIn, AH3 and PH3 are introduced to grow a quantum well layer on the N active waveguide layer; S8, the reaction chamber temperature is maintained at 670±10℃, TMAl, TMGa and AH3 are introduced, and a P-waveguide layer is grown on the quantum well layer; S9, the reaction chamber temperature is maintained at 700±10℃, TMAl, TMGa and AH3 are introduced, and a P-waveguide layer is grown on it; P-confining layer; S10, the reaction chamber temperature is maintained at 540-560℃, TMGa and AsH3 are introduced, and a cap layer is grown on the P confinement layer.

[0014] Furthermore, in step S1, the high-temperature heat treatment is carried out at a temperature of 720°C for 30 minutes.

[0015] The beneficial effects of this invention are: 1. The epitaxial wafer with refractive index modulation structure and its preparation method provided in this application are based on the theory of "band engineering". Both the quantum well layer and the P waveguide layer adopt a composition gradient structure, which can increase the refractive index difference and band gap difference between the quantum well layer and the P waveguide layer, thereby effectively reducing carrier leakage.

[0016] 2. This application provides an epitaxial wafer with a refractive index modulation structure. Its N-waveguide layer employs a three-waveguide structure, inserting a low-refractive-index N-anti-waveguide layer between the N-active and N-passive waveguide layers. Through refractive index guidance, the local competition between guided and anti-guided waves is modulated, providing additional degrees of freedom for optical confinement design. When the anti-guided wave dominates, the light field concentrated in the N-passive waveguide layer can penetrate deeply into the N-confinement layer, achieving a high catastrophic optical damage threshold. Meanwhile, the light field penetration in the P-confinement layer is shallower, allowing for further thinning of the P-confinement layer. Thinning the P-confinement layer reduces the diode's resistance and absorption loss, improving the device's output power and electro-optical conversion efficiency, thus enhancing the reliability of the epitaxial structure. It also reduces thermal resistance, mitigating carrier leakage induced by increased thermal resistance.

[0017] 3. The epitaxial wafer with refractive index modulation structure provided in this application inserts a low-refractive-index N-anti-waveguide layer between the N-active waveguide layer and the N-passive waveguide layer. At the same time, by classifying the composition of the aluminum-free active region, the refractive index difference between the quantum well and the P-waveguide layer is increased. Under the premise of effectively limiting carrier leakage, the optical field distribution is controlled by refractive index guidance, reducing optical loss and improving threshold characteristics. Meanwhile, the thin P-confinement layer can also reduce the resistance and thermal resistance of the diode, ultimately achieving high output power and photoelectric conversion efficiency, and improving the overall optoelectronic performance of the device. Attached Figure Description

[0018] Figure 1 A schematic diagram of an epitaxial wafer with a refractive index modulation structure is provided for the embodiments of the application; Figure 2 The band structure diagram of an epitaxial wafer with a refractive index modulation structure is provided for the application embodiment.

[0019] In the figure: 1. Substrate; 2. Buffer layer; 3. N-confinement layer; 4. N-waveguide layer; 41. N-passive waveguide layer; 42. N-anti-waveguide layer; 43. N-active waveguide layer; 5. Quantum well layer; 6. P-waveguide layer; 7. P-confinement layer; 8. Cap layer. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings. The described embodiments are merely a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort should fall within the protection scope of this application.

[0021] like Figure 1As shown, an epitaxial wafer with a refractive index modulation structure includes a substrate 1, on which a buffer layer 2, an N-confinement layer 3, an N-waveguide layer 4, a quantum well layer 5, a P-waveguide layer 6, a P-confinement layer 7, and a cap layer 8 are disposed sequentially from bottom to top.

[0022] The substrate 1 and the buffer layer 2 are made of GaAs. The doping concentration of the dopant source in the buffer layer 2 is 1E18-5E18 atoms / cm³. 3 The thickness of the buffer layer 2 is 100-300 nm.

[0023] In one specific implementation, the doping source in the buffer layer 2 described in this embodiment is Si2H6, and the doping concentration is 2E18 atoms / cm³. 3 The thickness of the buffer layer 2 is 200 nm.

[0024] The material of the N-confining layer 3 is Al. x1 Ga 1-x1 As, the value of x1 ranges from 0.4 to 0.7. The doping concentration of the dopant source in the N-confined layer 3 is 6E17-1E19 atoms / cm³. 3 The thickness of the N-restriction layer 3 is 1-1.5 μm.

[0025] In one specific implementation, the value of x1 in this embodiment is 0.6, that is, the material of the N-confining layer 3 is Al. 0.6 Ga 0.4 As. The doping source in the N-confined layer 3 is Si2H6, and the doping concentration is 8E17 atoms / cm. 3 The thickness of the N-restriction layer 3 is 1 μm.

[0026] The N waveguide layer 4, along the direction away from the N confinement layer 3, sequentially includes an N passive waveguide layer 41, an N anti-waveguide layer 42, and an N active waveguide layer 43.

[0027] The material of the N-passive waveguide layer 41 is Al. x2 Ga x2 As, the value of x2 ranges from 0.2 to 0.5. The doping concentration of the doped source in the N-type passive waveguide layer 41 is 2E16-1E17 atoms / cm². 3 The thickness of the N-passive waveguide layer 41 is 0.4-0.7 μm.

[0028] In one specific implementation, the value of x2 in this embodiment is 0.45, meaning that the material of the N passive waveguide layer 41 is Al. 0.45 The material is Ga0.45As. The doping source for the N-type passive waveguide layer 41 is Si2H6, with a doping concentration of 5E16 atoms / cm³. 3. The thickness of the N passive waveguide layer 41 is 0.6 μm.

[0029] The material of the N inverse waveguide layer 42 is Al x3 Ga 1-x3 As, and the value range of x3 is 0.5 ≤ x2 ≤ 0.8. The N inverse waveguide layer 42 is unintentionally doped. The thickness of the N inverse waveguide layer 42 is 15 - 30 nm.

[0030] As a specific implementation manner, in this embodiment, the value of x3 is 0.7, that is, the material of the N inverse waveguide layer 42 is Al 0.7 Ga0.3As. The thickness of the N inverse waveguide layer 42 is 25 nm.

[0031] The material of the N active waveguide layer 43 is Al x4 Ga 1-x4 As, and the value range of x4 is 0.2 ≤ x2 ≤ 0.5. The N active waveguide layer 43 is unintentionally doped. The thickness of the N active waveguide layer 43 is 0.3 - 0.5 μm.

[0032] As a specific implementation manner, in this embodiment, the value of x4 is 0.45, that is, the material of the N active waveguide layer 43 is Al 0.45 Ga0.55As. The thickness of the N active waveguide layer 43 is 0.4 μm.

[0033] Along the direction away from the N waveguide layer 4, the material composition of the quantum well layer 5 gradually changes from In x5 Ga 1-x5 As y1 P 1-y1 [[ID=3�]]to In x6 Ga 1-x6 As y2 P 1-y2 , where the value ranges of x5, x6, y1 and y2 are 0.2 ≤ x5 ≤ 0.6, 0.2 ≤ x6 ≤ 0.6, 0.15 ≤ y1 ≤ 0.3, 0.15 ≤ y2 ≤ 0.3 respectively, and x5 > x6, y1 < y2. The quantum well layer 5 is unintentionally doped. The thickness of the quantum well layer 5 is 8 - 15 nm.

[0034] As a specific implementation manner, in this embodiment, the value of x5 is 0.4, the value of x6 is 0.3, the value of y1 is 0.2, and the value of y2 is 0.25. The thickness of the quantum well layer 5 is 13 nm.

[0035] Such as Figure 2As shown, by designing the quantum well layer 5 as a graded composition, the bandgap difference between the quantum well layer 5 and the P waveguide layer 6 can be increased. With the increase in the bandgap difference, the potential barrier is higher and electron transition is difficult. Therefore, it can block the leakage of electrons to the P waveguide layer 6.

[0036] In the direction away from the quantum well layer 5, the material composition of the P waveguide layer 6 changes gradually from Al x7 Ga 1-x7 As to Al x8 Ga 1-x8 As, where the values of x7 and x8 range from 0.2 ≤ x7 ≤ 0.5, 0.2 ≤ x8 ≤ 0.5, and x7 < x8. The P waveguide layer 6 is unintentionally doped. The thickness of the P waveguide layer 6 is 0.4 - 0.9 μm.

[0037] As a specific embodiment, in this embodiment, the value of x7 is 0.25, the value of x8 is 0.4, and the thickness of the P waveguide layer 6 is 0.6 μm.

[0038] By designing the P waveguide layer 6 as a graded composition, the refractive index difference between the quantum well layer 5 and the P waveguide layer 6 can be increased, so that the optical field is biased towards the N waveguide layer 4 side to reduce the absorption loss of carriers.

[0039] The material of the P confinement layer 7 is Al x9 Ga 1-x9 As, and the value range of x9 is 0.5 ≤ x9 ≤ 0.8. The doping concentration of the doping source in the P confinement layer 7 is 7E17 - 2E18 atoms / cm 3 . The thickness of the P confinement layer 7 is 0.3 - 0.6 μm.

[0040] As a specific embodiment, in this embodiment, the value of x9 is 0.65, that is, the material of the P confinement layer 7 is Al 0.65 Ga 0.35 As. The doping source in the P confinement layer 7 is CBr4, and the doping concentration is 8E17 atoms / cm 3 . The thickness of the P confinement layer 7 is 0.4 μm.

[0041] The material of the cap layer 8 is GaAs, and the thickness is 100 - 300 nm. The doping concentration of the doping source in the cap layer 8 is 9E18 - 5E19 atoms / cm 3 .

[0042] As a specific embodiment, in this embodiment, the thickness of the cap layer 8 is 200 nm. The doping source in the cap layer 8 is CBr4, and the doping concentration is 4E19 atoms / cm 3 .

[0043] A method for preparing an epitaxial wafer with a refractive index modulation structure includes the following steps: S1. Place substrate 1 in the growth chamber of the MOCVD equipment, heat the H2 environment to 710-730℃ and bake for 20-40 minutes, then introduce AsH3 to perform high-temperature heat treatment on substrate 1 to remove water and oxygen from the surface of substrate 1.

[0044] In one specific implementation, in step S1 of this embodiment, the temperature for high-temperature heat treatment is 720°C, and the baking time is 30 minutes.

[0045] S2, control the reaction chamber temperature to slowly decrease to 670±10℃, with a cooling rate not exceeding 30℃ / min, introduce TMGa and AsH3, and grow a buffer layer 2 with a thickness of 100-300nm on substrate 1.

[0046] In one specific implementation, in step S2 of this embodiment, the temperature of the reaction chamber is gradually reduced to 670°C.

[0047] S3, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N-confined layer 3 with a thickness of 1-1.5um on the buffer layer 2.

[0048] S4, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N passive waveguide layer 41 with a thickness of 0.4-0.7um on the N confinement layer 3.

[0049] S5, control the temperature of the reaction chamber to rise to 700±10℃ and maintain the temperature of the reaction chamber at 700±10℃, introduce TMAl, TMGa and AH3, and grow an N-reverse waveguide layer 42 with a thickness of 15-30nm on the N passive waveguide layer 41.

[0050] S6, control the temperature of the reaction chamber to drop to 670±10℃ and maintain the temperature of the reaction chamber at 670±10℃, introduce TMAl, TMGa and AH3, and grow an N active waveguide layer 43 with a thickness of 0.3-0.5um on the N anti-waveguide layer 42.

[0051] S7, the reaction chamber temperature is maintained at 670±10℃, and TMGa, TMIn, AH3 and PH3 are introduced to grow a quantum well layer 5 with a thickness of 8-15nm on the N active waveguide layer 43.

[0052] S8, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow a P waveguide layer 6 with a thickness of 0.4-0.9um on the quantum well layer 5.

[0053] S9, control the reaction chamber temperature to rise to 700±10℃ and maintain the reaction chamber temperature at 700±10℃, introduce TMAl, TMGa and AH3, and grow a P-confining layer 7 with a thickness of 0.3-0.6um on the P waveguide layer 6.

[0054] S10, control the reaction chamber temperature to drop to 540-560℃ and maintain the reaction chamber temperature at 540-560℃, introduce TMGa and AsH3, and grow a cap layer 8 with a thickness of 100-300nm on the P confinement layer 7.

[0055] Other embodiments obtained by those skilled in the art based on the embodiments provided in this application by combining, splitting, or reorganizing the embodiments of this application do not exceed the protection scope of this application.

[0056] The above detailed embodiments have provided a detailed explanation of the purpose, technical solutions, and beneficial effects of the embodiments of this application. The above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. That is, any modifications, equivalent substitutions, improvements, etc., made on the basis of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. An epitaxial wafer with a refractive index modulation structure, comprising a substrate (1), wherein a buffer layer (2), an N-confinement layer (3), an N-waveguide layer (4), a quantum well layer (5), a P-waveguide layer (6), a P-confinement layer (7), and a cap layer (8) are sequentially disposed on the substrate (1) from bottom to top, characterized in that: The N waveguide layer (4) includes, in sequence, an N passive waveguide layer (41), an N anti-waveguide layer (42), and an N active waveguide layer (43) along the direction away from the N confinement layer (3). Along the direction away from the N waveguide layer (4), the In content in the quantum well layer (5) gradually decreases and the As content gradually increases; Along the direction away from the quantum well layer (5), the Al content in the P waveguide layer (6) gradually increases.

2. An epitaxial wafer with a refractive index modulation structure according to claim 1, characterized in that: The material of the N-passive waveguide layer (41) is Al. x2 Ga x2 As, the value range of x2 is 0.2≤x2≤0.5, and the doping concentration of the doped source in the N passive waveguide layer (41) is 2E16-1E17 atoms / cm. 3 The thickness of the N passive waveguide layer (41) is 0.4-0.7 μm.

3. An epitaxial wafer with a refractive index modulation structure according to claim 1, characterized in that: The material of the N-reverse waveguide layer (42) is Al. x3 Ga 1-x3 As, the value range of x3 is 0.5≤x2≤0.8, the N-anti-waveguide layer (42) is unintentionally doped, and the thickness of the N-anti-waveguide layer (42) is 15-30nm.

4. An epitaxial wafer with a refractive index modulation structure according to claim 1, characterized in that: The material of the N-active waveguide layer (43) is Al. x4 Ga 1-x4 As, the value range of x4 is 0.2≤x2≤0.5, the N active waveguide layer (43) is unintentionally doped, and the thickness of the N active waveguide layer (43) is 0.3-0.5μm.

5. An epitaxial wafer with a refractive index modulation structure according to claim 1, characterized in that: Along the direction away from the N-waveguide layer (4), the material composition of the quantum well layer (5) is composed of In x5 Ga 1-x5 As y1 P 1-y1 Gradually becoming In x6 Ga 1- x6 As y2 P 1-y2 The values ​​of x5, x6, y1 and y2 are respectively 0.2≤x5≤0.6, 0.2≤x6≤0.6, 0.15≤y1≤0.3, and 0.15≤y2≤0.

3.

6. An epitaxial wafer with a refractive index modulation structure according to claim 5, characterized in that: The quantum well layer (5) is unintentionally doped, and the thickness of the quantum well layer (5) is 8-15 nm.

7. An epitaxial wafer with a refractive index modulation structure according to claim 1, characterized in that: Along the direction away from the quantum well layer (5), the material composition of the P-waveguide layer (6) is composed of Al x7 Ga 1-x7 As gradually transforms into Al x8 Ga 1-x8 As, where the values ​​of x7 and x8 are in the range of 0.2≤x7≤0.5 and 0.2≤x8≤0.

5.

8. An epitaxial wafer with a refractive index modulation structure according to claim 7, characterized in that: The P-waveguide layer (6) is unintentionally doped, and the thickness of the P-waveguide layer (6) is 0.4-0.9 μm.

9. A method for preparing an epitaxial wafer with a refractive index modulation structure as described in any one of claims 1-8, characterized in that: Includes the following steps, S1, place the substrate (1) in the growth chamber of the MOCVD equipment, heat the H2 environment to 710-730℃ and bake for 20-40 minutes, then introduce AsH3 to perform high-temperature heat treatment on the substrate (1); S2, control the reaction chamber temperature to slowly decrease to 670±10℃, introduce TMGa and AsH3, and grow a buffer layer (2) on the substrate (1). S3, the reaction chamber temperature is maintained at 670±10℃, TMAl, TMGa and AH3 are introduced, and an N-confined layer (3) is grown on the buffer layer (2). S4, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N passive waveguide layer (41) on the N confinement layer (3). S5, the reaction chamber temperature is maintained at 700±10℃, and TMAl, TMGa and AH3 are introduced to grow an N-anti-waveguide layer (42) on the N-passive waveguide layer (41). S6, the reaction chamber temperature is maintained at 670±10℃, and TMAl, TMGa and AH3 are introduced to grow an N active waveguide layer (43) on the N anti-waveguide layer (42). S7, the reaction chamber temperature is maintained at 670±10℃, and TMGa, TMIn, AH3 and PH3 are introduced to grow a quantum well layer (5) on the N active waveguide layer (43). S8, the reaction chamber temperature is maintained at 670±10℃, TMAl, TMGa and AH3 are introduced, and the quantum well layer (5) is grown; P waveguide layer (6); S9, the reaction chamber temperature is maintained at 700±10℃, TMAl, TMGa and AH3 are introduced, and growth is carried out on the P waveguide layer (6); P confinement layer (7); S10, the reaction chamber temperature is maintained at 540-560℃, TMGa and AsH3 are introduced, and a cap layer (8) is grown on the P confinement layer (7).

10. The method for preparing an epitaxial wafer with a refractive index modulation structure according to claim 9, characterized in that: In step S1, the high-temperature heat treatment is carried out at a temperature of 720°C for 30 minutes.

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