Semiconductor laser structure with step strain layer

Abstract

The invention relates to the technical field of semiconductors, and particularly discloses a semiconductor laser structure with stepped strain layers, which comprises a contact layer, a P-surface limiting layer, a P-surface waveguide layer, an active layer, an N-surface waveguide layer, an N-surface limiting layer and a buffer layer which are arranged in sequence, the buffer layer is made of gallium arsenide, a plurality of first strain layers are arranged between the buffer layer and the N-surface limiting layer, and a plurality of second strain layers are arranged between the N-surface limiting layer and the N-surface limiting layer. The material of the first strain layer is Al < x > Ga < 1-x > In < y > P, xlt; 1, 0lt; yt; Yt; 0.48, a second strain layer is arranged between the P-plane waveguide layer and the active layer, the material of the second strain layer is AlaGa1-aInbP, 0 lt; a < lt >; 0 1t, 0.4, 0 1t; blt; and 0.48%. The laser epitaxial structure has the effect of improving the defect of serious warping caused by large pressure stress of the laser epitaxial structure.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a semiconductor laser structure with a stepped strain layer. Background Art

[0002] Most of the buffer layers of traditional high-power laser epitaxial structures are made of gallium arsenide. Except for the buffer layer, this structure is usually made of gallium aluminum arsenide with different aluminum contents. Although the lattice parameters of aluminum arsenide and gallium arsenide are very close, being 5.6691 Å and 5.6533 Å respectively, with a lattice mismatch of 1500 ppm, the total thickness of the aluminum-containing part of the entire laser epitaxial structure is between 4 - 10 μm, resulting in a relatively large accumulation of total compressive stress.

[0003] After testing, for a 4-inch epitaxial wafer, without thinning the substrate, the warpage reaches 20 μm; if the substrate is thinned to 150 μm, the warpage reaches about 260 μm. For a 6-inch epitaxial wafer, without thinning the substrate, the warpage is 150 μm. If the substrate is thinned to 150 μm, the warpage is extremely serious, and it is very easy to break into pieces. Even if it does not break into pieces, cavity lines are easily generated during cleavage, resulting in the failure of cavity surface reliability. Summary of the Invention

[0004] In order to improve the defect that the compressive stress of the laser epitaxial structure is large, resulting in serious warpage, this application provides a semiconductor laser structure with a stepped strain layer.

[0005] This application provides a semiconductor laser structure with a stepped strain layer, adopting the following technical solution: A semiconductor laser structure with a stepped strain layer includes a contact layer, a P-side confinement layer, a P-side waveguide layer, an active layer, an N-side waveguide layer, an N-side confinement layer, and a buffer layer arranged in sequence. The material of the buffer layer is gallium arsenide. Between the buffer layer and the N-side confinement layer, there are a number of first strain layers. The material of the first strain layer is Al x Ga 1-x In y P, where 0 < x < 1, 0 < y < 0.48. Between the P-side waveguide layer and the active layer, there is a second strain layer. The material of the second strain layer is Al a Ga 1-a In b P, where 0 < a < 0.4, 0 < b < 0.48.

[0006] By adopting the above technical solution, a first strain layer is arranged between the buffer layer and the N-side confinement layer, and the stress is adjusted by adjusting the proportion of indium component. When y = 0.48, Al x Ga 1-x In yP lattice matches gallium arsenide, and when y < 0.48, Al x Ga 1-x In y The lattice of P is smaller than that of gallium arsenide. By introducing tensile stress into the structure that is opposite to the compressive stress of the laser epitaxial structure, the stress of the entire epitaxial structure is balanced, reducing epitaxial wafer warpage, reducing fragmentation rate, cleaving cavity texture, improving yield, and improving the defect of high compressive stress in laser epitaxial structure that leads to severe warpage. A second strain layer is set between the P-plane waveguide layer and the active layer. The second strain layer provides tensile stress to the structure and also plays a role in electron confinement. By adjusting the value of 'a', the refractive index and barrier height of the second strain layer can be changed, thereby improving the quantum confinement and optical field confinement effects.

[0007] Optionally, the epitaxial growth temperature of the first strain layer and the second strain layer is 600-750℃, and the epitaxial growth pressure is 80-200mbar.

[0008] Optionally, the epitaxial growth of the first strained layer and the second strained layer is performed by PH3 thermal decomposition, with a PH3 flow rate of 300-2000 sccm.

[0009] Optionally, the number of the first strain layers is 3-10, and the y value of some of the first strain layers varies linearly.

[0010] Optionally, both the N-plane confinement layer and the N-plane waveguide layer are made of aluminum gallium arsenide, and both are doped with silicon at a doping concentration of 5 × 10⁻⁶. 16 -3×10 18 cm -3 The epitaxial growth temperature of the N-plane confinement layer and the N-plane waveguide layer is 600-750℃, and the epitaxial growth pressure is 80-200mbar.

[0011] Optionally, the epitaxial growth of the N-plane confinement layer and the N-plane waveguide layer is performed by AsH3 thermal decomposition, with an AsH3 flux of 300-2000 sccm, and the total thickness of the N-plane confinement layer and the N-plane waveguide layer is 1-5 μm.

[0012] Optionally, the active layer is made of aluminum gallium indium phosphate (GaGa), and the epitaxial growth temperature of the active layer is 580-750℃, the epitaxial growth pressure is 80-200mbar, and the thickness is 2-10nm.

[0013] Optionally, both the P-plane confinement layer and the P-plane waveguide layer are made of aluminum gallium arsenide, and both are doped with carbon at a concentration of 5 × 10⁻⁶. 16 -3×10 18 cm -3The epitaxial growth temperature of the P-plane confinement layer and the P-plane waveguide layer is 600-750℃, the epitaxial growth pressure is 80-200mbar, and the total thickness of the P-plane confinement layer and the P-plane waveguide layer is 1-5μm.

[0014] Optionally, the epitaxial growth of the P-plane confinement layer and the P-plane waveguide layer is performed by AsH3 thermal decomposition, with an AsH3 flux of 300-2000 sccm.

[0015] Optionally, the contact layer is made of gallium arsenide phosphide and is doped with carbon at a concentration of 5 × 10⁻⁶. 19 -5×10 20 cm -3 The epitaxial growth temperature of the contact layer is 550-650℃, the epitaxial growth pressure is 80-200mbar, and the thickness is 50-500nm.

[0016] In summary, this application includes at least one of the following beneficial technical effects: A first strain layer is set between the buffer layer and the N-plane confinement layer. The stress magnitude is adjusted by adjusting the ratio of indium composition. When y=0.48, AlxGa1-xInyP matches the lattice of gallium arsenide. When y<0.48, the lattice of AlxGa1-xInyP is smaller than that of gallium arsenide. Tensile stress opposite to the compressive stress of the laser epitaxial structure is introduced into the structure to balance the stress of the entire epitaxial structure, reduce epitaxial wafer warpage, reduce fragmentation rate, cleave cavity texture, improve yield, and improve the defect of large compressive stress in laser epitaxial structure leading to severe warpage. A second strain layer is set between the P-plane waveguide layer and the active layer. The second strain layer provides tensile stress to the structure and also plays a role in electron confinement. By adjusting the value of 'a', the refractive index and barrier height of the second strain layer can be changed, thereby improving the quantum confinement and optical field confinement effects. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a semiconductor laser structure with a stepped strain layer according to an embodiment of this application.

[0018] Explanation of reference numerals in the attached figures: 1. Contact layer; 2. P-plane confinement layer; 3. P-plane waveguide layer; 4. Second strain layer; 5. Active layer; 6. N-plane waveguide layer; 7. N-plane confinement layer; 8. First strain layer; 9. Buffer layer; 10. Substrate. Detailed Implementation

[0019] The following is in conjunction with the appendix Figure 1 This application will be described in further detail. Example

[0020] This application discloses a semiconductor laser structure with a stepped strain layer.

[0021] Example 1

[0022] Reference Figure 1 A semiconductor laser structure with a stepped strain layer includes a contact layer 1, a P-plane confinement layer 2, a P-plane waveguide layer 3, a second strain layer 4, an active layer 5, an N-plane waveguide layer 6, an N-plane confinement layer 7, a first strain layer 8, a buffer layer 9, and a substrate 10 arranged sequentially.

[0023] The material of contact layer 1 is gallium arsenide phosphide, and contact layer 1 is doped with carbon, with a carbon doping concentration of 5 × 10⁻⁶. 19 -5×10 20 cm -3 The epitaxial growth temperature is 550-650℃, the epitaxial growth pressure is 80-200 mbar, and the thickness is 50-500 nm. In this embodiment, the carbon doping concentration of contact layer 1 is 5 × 10⁻⁶. 20 cm -3 The epitaxial growth temperature is 600℃, the epitaxial growth pressure is 200mbar, and the thickness is 200nm.

[0024] The p-side confinement layer 2 is made of aluminum gallium arsenide and is fixedly connected to the contact layer 1. The p-side confinement layer 2 is doped with carbon at a concentration of 5 × 10⁻⁶. 16 -3×10 18 cm -3 The epitaxial growth of the P-side confinement layer 2 is achieved through the thermal decomposition of AsH3, with an AsH3 flow rate of 300-2000 sccm. The epitaxial growth temperature of the P-side confinement layer 2 is 600-750℃, and the epitaxial growth pressure is 80-200 mbar. In this embodiment, the material of the P-side confinement layer 2 is Al. 0.2 GaAs. The carbon doping concentration of the p-face confinement layer 2 is 5 × 10⁻⁶. 16 cm -3 The flow rate of AsH3 was 1800 sccm, the epitaxial growth temperature was 650℃, the epitaxial growth pressure was 200 mbar, and the thickness was 500 nm.

[0025] The P-plane waveguide layer 3 is made of aluminum gallium arsenide and is fixedly connected to the P-plane confinement layer 2. The P-plane waveguide layer 3 is doped with carbon at a concentration of 5 × 10⁻⁶. 16 -3×10 18 cm -3。The epitaxial growth of the P-side waveguide layer 3 is carried out by thermal decomposition of AsH3. The flow rate of AsH3 is 300 - 2000 sccm. The epitaxial growth temperature of the P-side waveguide layer 3 is 600 - 750 °C, the epitaxial growth pressure is 80 - 200 mbar, and the total thickness of the P-side confinement layer 2 and the P-side waveguide layer 3 is 1 - 5 μm. In this embodiment, the material of the P-side waveguide layer 3 is Al 0.4 GaAs. The carbon doping concentration of the P-side waveguide layer 3 is 3×10 17 cm -3 , the flow rate of AsH3 is 1600 sccm, the epitaxial growth temperature is 750 °C, the epitaxial growth pressure is 200 mbar, and the thickness is 1000 nm.

[0026] The material of the second strain layer 4 is Al a Ga 1-a In b P, where 0 < a < 0.4, 0 < b < 0.48, and the second strain layer 4 is fixedly connected to the P-side waveguide layer 3. The epitaxial growth of the second strain layer 4 is carried out by thermal decomposition of PH3. The flow rate of PH3 is 300 - 2000 sccm. The epitaxial growth temperature of the second strain layer 4 is 600 - 750 °C, and the epitaxial growth pressure is 80 - 200 mbar. In this embodiment, the material of the second strain layer 4 is Al 0.3 Ga 0.7 In 0.4 P, the flow rate of PH3 is 2000 sccm. The epitaxial growth temperature of the second strain layer 4 is 700 °C, and the epitaxial growth pressure is 180 mbar.

[0027] The material of the active layer 5 is gallium indium arsenide, and the active layer 5 is fixedly connected to the second strain layer 4. The epitaxial growth of the active layer 5 is carried out by thermal decomposition of AsH3. The flow rate of AsH3 is 50 - 100 sccm. The epitaxial growth temperature of the active layer 5 is 580 - 750 °C, the epitaxial growth pressure is 80 - 200 mbar, and the thickness is 2 - 10 nm. In this embodiment, the material of the active layer 5 is In 0.08 GaAs. The epitaxial growth temperature of the active layer 4 is 630 °C, the epitaxial growth pressure is 120 mbar, the thickness is 6 nm, and the flow rate of AsH3 is 80 sccm.

[0028] The material of the N-side waveguide layer 6 is aluminum gallium arsenide, and the N-side waveguide layer 6 is fixedly connected to the active layer 5. The N-side waveguide layer 6 is doped with silicon element, and the doping concentration of silicon is 5×10 16 -3×10 18 cm -3。The epitaxial growth of the N-side waveguide layer 6 is carried out by thermal decomposition of AsH3. The flow rate of AsH3 is 300 - 2000 sccm, the epitaxial growth temperature of the N-side waveguide layer 6 is 600 - 750 °C, and the epitaxial growth pressure is 80 - 200 mbar. In this embodiment, the material of the N-side waveguide layer 6 is Al 0.4 GaAs. The doping concentration of silicon element in the N-side waveguide layer 6 is 5×10 17 cm -3 . The flow rate of AsH3 is 1900 sccm, the epitaxial growth temperature is 670 °C, the epitaxial growth pressure is 150 mbar, and the thickness is 1000 nm.

[0029] The material of the N-side confinement layer 7 is aluminum gallium arsenide, and the N-side confinement layer 7 is fixedly connected to the N-side waveguide layer 6. The N-side confinement layer 7 is doped with silicon element, and the doping concentration of silicon is 5×10 16 -3×10 18 cm -3 . The epitaxial growth of the N-side confinement layer 7 is carried out by thermal decomposition of AsH3. The flow rate of AsH3 is 300 - 2000 sccm, the epitaxial growth temperature of the N-side confinement layer 7 is 600 - 750 °C, the epitaxial growth pressure is 80 - 200 mbar, and the thickness is 1 - 5 μm. In this embodiment, the material of the N-side confinement layer 7 is Al 0.2 GaAs. The doping concentration of silicon element in the N-side confinement layer 7 is 5×10 16 cm -3 . The flow rate of AsH3 is 2000 sccm, the epitaxial growth temperature is 700 °C, the epitaxial growth pressure is 120 mbar, and the thickness is 500 nm.

[0030] The material of the first strain layer 8 is Al x Ga 1-x In y P, where 0 < x < 1, 0 < y < 0.48, and the first strain layer 8 is fixedly connected to the N-side confinement layer 7. The epitaxial growth of the first strain layer 8 is carried out by thermal decomposition of PH3. The flow rate of PH3 is 300 - 2000 sccm. The epitaxial growth temperature of the first strain layer 8 is 600 - 750 °C, and the epitaxial growth pressure is 80 - 200 mbar. In this embodiment, there are three first strain layers 8, and the materials of the three first strain layers 8 are respectively Al 0.3 Ga 0.7 In 0.25 P, Al 0.3 Ga 0.7 In 0.3 P, and Al 0.3 Ga 0.7 In 0.35The flow rate of P and PH3 is 1000 sccm. The epitaxial growth temperature of the first strain layer 8 is 720℃, and the epitaxial growth pressure is 190 mbar.

[0031] The buffer layer 9 is made of gallium arsenide and is fixedly connected to the first strain layer 8. In this embodiment, the thickness of the buffer layer 9 is 200 nm.

[0032] The substrate 10 is made of gallium arsenide and is fixedly connected to the buffer layer 9. In this embodiment, the substrate 10 is 6 inches in size and 675 μm thick. The contact layer 1, the P-plane confinement layer 2, the P-plane waveguide layer 3, the second strain layer 4, the active layer 5, the N-plane waveguide layer 6, the N-plane confinement layer 7, the first strain layer 8, and the buffer layer 9 are all the same size as the substrate 10.

[0033] In this embodiment, the total compressive stress generated by the contact layer 1, P-plane confinement layer 2, P-plane waveguide layer 3, active layer 5, N-plane waveguide layer 6, and N-plane confinement layer 7 is 283ppm×500nm+567ppm×1000nm+5731ppm×6nm+567ppm×1000nm+283ppm×500nm=1451386.

[0034] Since the materials of the three first strain layers 8 are Al 0.3 Ga 0.7 In 0.25 P, Al 0.3 Ga 0.7 In 0.3 P and Al 0.3 Ga 0.7 In 0.35 P, the material of the second strain layer 4 is Al 0.3 Ga 0.7 In 0.4 XRD analysis revealed that the stress differences between the three first strain layers 8 and the buffer layer 9 were -15691 ppm, -12000 ppm, and -8294 ppm, respectively, while the stress difference between the second strain layer 4 and the buffer layer 4 was -4595 ppm. To eliminate these stress differences, the thicknesses of the first strain layers 8 and the second strain layer 4 can have various values. In this embodiment, the thicknesses of the three first strain layers 8 are 20 nm, 20 nm, and 30 nm, respectively, while the thickness of the second strain layer 4 is 141 nm.

[0035] Example 2

[0036] The difference between Example 2 and Example 1 is that the thicknesses of the first strain layer 8 and the second strain layer 4 are different.

[0037] In this embodiment, the thickness of each of the three first strain layers 8 is 30 nm, while the thickness of the second strain layer 4 is 80 nm.

[0038] As can be seen from Examples 1-2, the thicknesses of the first strain layer 8 and the second strain layer 4 are determined by the stress difference between the first strain layer 8, the second strain layer 4, and the buffer layer 9, as well as the total compressive stress generated by the contact layer 1, the P-plane confinement layer 2, the P-plane waveguide layer 3, the active layer 5, the N-plane waveguide layer 6, and the N-plane confinement layer 7. The stress difference between the first strain layer 8 and the buffer layer 9 is determined by the values ​​of x and y, and the stress difference between the second strain layer 4 and the buffer layer 9 is determined by the values ​​of a and b.

[0039] XRD analysis software shows that when y < 0.48, Al x Ga 1-x In y The smaller lattice size of P compared to gallium arsenide creates tensile stress between the first strain layer 8 and the buffer layer 9. Introducing tensile stress into the structure, opposite to the compressive stress of the laser epitaxial structure, balances the stress throughout the epitaxial structure, reduces epitaxial wafer warpage, lowers the fragmentation rate, cleaves cavity textures, improves yield, and mitigates the defects caused by high compressive stress leading to severe warpage in the laser epitaxial structure.

[0040] The second strain layer 4 not only provides tensile stress to the structure, but also plays a role in electron confinement. By adjusting the value of 'a', the refractive index and barrier height of the second strain layer 4 can be changed, thereby improving the quantum confinement and optical field confinement effects.

[0041] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A semiconductor laser structure with a step strain layer, comprising a contact layer (1), a P-face confinement layer (2), a P-face waveguide layer (3), an active layer (5), an N-face waveguide layer (6), an N-face confinement layer (7) and a buffer layer (9) arranged in sequence, characterized in that: The material of the buffer layer (9) is gallium arsenide, and a plurality of first strain layers (8) are provided between the buffer layer (9) and the N-side confinement layer (7). The material of the first strain layer (8) is Al x Ga 1-x In y P, where 0 < x < 1 and 0 < y < 0.

48. A second strain layer (4) is provided between the P-side waveguide layer (3) and the active layer (5). The material of the second strain layer (4) is Al a Ga 1-a In b P, where 0 < a < 0.4 and 0 < b < 0.

48.

2. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The epitaxial growth temperature of the first strained layer (8) and the second strained layer (4) is 600-750° C., and the epitaxial growth pressure is 80-200 mbar.

3. The semiconductor laser structure with a step strain layer according to claim 2, characterized in that: The epitaxial growth of the first strained layer (8) and the second strained layer (4) is carried out by thermal decomposition of PH3, and the flow rate of PH3 is 300-2000 sccm.

4. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The number of the first strain layers (8) is 3-10, and the y values ​​of a plurality of the first strain layers (8) vary linearly.

5. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The materials of the N-side limiting layer (7) and the N-side waveguide layer (6) are both gallium aluminum arsenide, the epitaxial growth temperature of the N-side limiting layer (7) and the N-side waveguide layer (6) is 600-750° C., and the epitaxial growth pressure is 80-200 mbar.

6. The semiconductor laser structure with a step strain layer according to claim 5, characterized in that: The epitaxial growth of the N-side limiting layer (7) and the N-side waveguide layer (6) is carried out by thermal decomposition of AsH3, with the flow rate of AsH3 being 300-2000sccm.

7. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The material of the active layer (5) is indium gallium aluminum, the epitaxial growth temperature of the active layer (5) is 580-750° C., and the epitaxial growth pressure is 80-200 mbar.

8. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The materials of the P-face limiting layer (2) and the P-face waveguide layer (3) are both gallium aluminum arsenide, the epitaxial growth temperature of the P-face limiting layer (2) and the P-face waveguide layer (3) is 600-750° C., and the epitaxial growth pressure is 80-200 mbar.

9. The semiconductor laser structure with a step strain layer according to claim 8, characterized in that: The epitaxial growth of the P-face limiting layer (2) and the P-face waveguide layer (3) is carried out by thermal decomposition of AsH3, and the flow rate of AsH3 is 300-2000sccm.

10. The semiconductor laser structure with a step strain layer according to claim 1, characterized in that: The material of the contact layer (1) is gallium arsenide phosphide, the epitaxial growth temperature of the contact layer (1) is 550-650° C., and the epitaxial growth pressure is 80-200 mbar.

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