Semiconductor laser structure with cyclic strain buffer layer

Abstract

The invention relates to the technical field of semiconductors, and particularly discloses a semiconductor laser structure with cyclic strain buffer layers, which comprises an epitaxial structure layer and a substrate, a plurality of groups of strain buffer layers are arranged between the epitaxial structure layer and the substrate, each group of strain buffer layers comprises a strain layer and a buffer layer, the buffer layers are made of gallium arsenide, and the cyclic strain buffer layers are arranged between the epitaxial structure layer and the substrate. The material of the strain layer is Al < x > Ga < 1-x > In < y > P, xlt; 1, 0lt; yt; Yt; and 0.48, 3 to 50 groups of strain buffer layers are arranged. 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 cyclic strain buffer layer. Background Art

[0002] Most of the buffer layers of traditional high-power laser epitaxial structures are made of gallium arsenide materials. Except for the buffer layer, this structure is usually made of aluminum gallium arsenide materials with different aluminum contents. Although the lattice parameters of aluminum arsenide and gallium arsenide are very close, 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 total compressive stress accumulation.

[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, the warpage is 150 μm without thinning the substrate. If the substrate is thinned to 150 μm, the warpage is extremely severe, 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 severe warpage, this application provides a semiconductor laser structure with a cyclic strain buffer layer.

[0005] This application provides a semiconductor laser structure with a cyclic strain buffer layer, adopting the following technical solution: A semiconductor laser structure with a cyclic strain buffer layer includes an epitaxial structure layer and a substrate. Between the epitaxial structure layer and the substrate, there are several groups of strain buffer layers. Each group of strain buffer layers includes a strain layer and a buffer layer. The material of the buffer layer is gallium arsenide, and the material of the strain layer is Al x Ga 1-x In y P, where 0 < x < 1, 0 < y < 0.48, and there are 3 - 50 groups of the strain buffer layers.

[0006] By adopting the above technical solution, several strain buffer layers are arranged between the epitaxial structure layer and the substrate. By adjusting the proportion of indium components in the strain layer, the stress magnitude is adjusted. When y = 0.48, Al x Ga 1-x In y P is lattice-matched with gallium arsenide. When y < 0.48, Al x Ga 1-x In yThe lattice of P is smaller than that of GaAs, and tensile stress is generated between the buffer layer and the strain layer. The tensile stress opposite to the compressive stress of the laser epitaxial structure is introduced into the structure, so that the stress of the entire epitaxial structure is balanced, the warping of the epitaxial wafer is reduced, the fragmentation rate is reduced, the cavity lines are cleaved, the yield is improved, and the defect of severe warping caused by large compressive stress of the laser epitaxial structure is improved; Compared with directly setting a strain layer and a buffer layer, setting a cyclic strain buffer layer can not only control the total stress of the structure, but also make each layer of GaAs and Al x Ga 1-x In y The thickness of P is reduced, thereby improving the interface quality between the strain layer and the buffer layer, and enhancing the reliability of the entire semiconductor laser structure.

[0007] Optionally, the total thickness of the buffer layer is 200 nm.

[0008] Optionally, the epitaxial growth temperature of the strained layer is 600-750° C., the epitaxial growth pressure is 80-200 mbar, and the epitaxial growth of the strained layer adopts PH3 thermal decomposition, and the flow rate of PH3 is 300-2000 sccm.

[0009] Optionally, the epitaxial structure layer includes a contact layer, a P-face confinement layer, a P-face waveguide layer, an active layer, an N-face waveguide layer and an N-face confinement layer which are arranged in sequence, and the N-face confinement layer is located between the N-face waveguide layer and the substrate.

[0010] Optionally, the materials of the N-side limiting layer and the N-side waveguide layer are both GaAs Al, and the N-side limiting layer and the N-side waveguide layer are doped with silicon, and the doping concentration of silicon is 5×10 16 -3×10 18 cm -3 The epitaxial growth temperature of the N-side confinement layer and the N-side waveguide layer is 600-750° C., and the epitaxial growth pressure is 80-200 mbar.

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

[0012] Optionally, the material of the active layer is indium gallium aluminum, the epitaxial growth temperature of the active layer is 580-750° C., the epitaxial growth pressure is 80-200 mbar, and the thickness is 2-10 nm.

[0013] Optionally, the materials of the P-plane limiting layer and the P-plane waveguide layer are both gallium aluminum arsenide, and the P-plane limiting layer and the P-plane waveguide layer are doped with carbon, and the carbon doping concentration is 5×10 16 -3×1018 cm -3 The epitaxial growth temperature of the P-face limiting layer and the P-face waveguide layer is 600-750° C., the epitaxial growth pressure is 80-200 mbar, and the total thickness of the P-face limiting layer and the P-face waveguide layer is 1-5 μm.

[0014] Optionally, the epitaxial growth of the P-face confinement layer and the P-face waveguide layer is performed by thermal decomposition of AsH3, and the flow rate of AsH3 is 300-2000sccm.

[0015] Optionally, the material of the contact layer is gallium arsenide phosphorus, and the contact layer is doped with carbon, and the carbon doping concentration is 5×10 19 -5×10 20 cm -3 The epitaxial growth temperature of the contact layer is 550-650° C., the epitaxial growth pressure is 80-200 mbar, and the thickness is 50-500 nm.

[0016] In summary, the present application includes at least one of the following beneficial technical effects: A number of strain buffer layers are arranged between the epitaxial structure layer and the substrate. The stress is adjusted by adjusting the proportion of the indium component in the strain layer. When y=0.48, the lattice of AlxGa1-xInyP matches that of gallium arsenide. When y<0.48, the lattice of AlxGa1-xInyP is smaller than that of gallium arsenide, and tensile stress is generated between the buffer layer and the strain layer. The tensile stress opposite to the compressive stress of the laser epitaxial structure is introduced into the structure, so that the stress of the entire epitaxial structure is balanced, the warping of the epitaxial wafer is reduced, the fragmentation rate is reduced, the cavity lines are cleaved, the yield is improved, and the defect of the laser epitaxial structure with large compressive stress and severe warping is improved. Compared with directly setting a strain layer and a buffer layer, setting a cyclic strain buffer layer can not only control the total stress of the structure, but also reduce the thickness of each layer of gallium arsenide and AlxGa1-xInyP, thereby improving the interface quality between the strain layer and the buffer layer and enhancing the reliability of the entire semiconductor laser structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a semiconductor laser structure with a cyclic strain buffer layer according to an embodiment of the present application.

[0018] Explanation of the accompanying drawings: 1. contact layer; 2. P-side confinement layer; 3. P-side waveguide layer; 4. active layer; 5. N-side waveguide layer; 6. N-side confinement layer; 7. strain layer; 8. buffer layer; 9. substrate. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1 This application is described in further detail.

[0020] Example

[0021] The embodiment of the present application discloses a semiconductor laser structure with a cyclic strain buffer layer.

[0022] Example 1

[0023] Reference Figure 1 A semiconductor laser structure with a cyclic strain buffer layer includes a contact layer 1, a P-face confinement layer 2, a P-face waveguide layer 3, an active layer 4, an N-face waveguide layer 5, an N-face confinement layer 6, a plurality of strain buffer layers and a substrate 9 which are arranged in sequence.

[0024] The material of the contact layer 1 is gallium arsenide phosphorus, and the contact layer 1 is doped with carbon, and the doping concentration of carbon is 5×10 19 -5×10 20 cm -3 , the epitaxial growth temperature is 550-650°C, the epitaxial growth pressure is 80-200 mbar, and the thickness is 50-500 nm. In this embodiment, the carbon doping concentration of the contact layer 1 is 5×10 19 cm -3 , the epitaxial growth temperature is 650°C, the epitaxial growth pressure is 80mbar, and the thickness is 200nm.

[0025] The material of the P-plane restriction layer 2 is gallium aluminum arsenide, and the P-plane restriction layer 2 is fixedly connected to the contact layer 1. The P-plane restriction layer 2 is doped with carbon, and the doping concentration of carbon is 5×10 16 -3×10 18 cm -3 The epitaxial growth of the P-face limiting layer 2 is carried out by thermal decomposition of AsH3, the flow rate of AsH3 is 300-2000sccm, the epitaxial growth temperature of the P-face limiting layer 2 is 600-750°C, and the epitaxial growth pressure is 80-200mbar. In this embodiment, the material of the P-face limiting layer 2 is Al 0.2 GaAs. The carbon doping concentration of the P-surface confinement layer 2 is 9×10 16 cm -3 , the flow rate of AsH3 is 1300sccm, the epitaxial growth temperature is 610℃, the epitaxial growth pressure is 200mbar, and the thickness is 500nm.

[0026] The material of the P-plane waveguide layer 3 is gallium aluminum arsenide, and the P-plane waveguide layer 3 is fixedly connected to the P-plane limiting layer 2. The P-plane waveguide layer 3 is doped with carbon, and the doping concentration of carbon is 5×10 16 -3×10 18 cm -3The epitaxial growth of the P-face waveguide layer 3 is carried out by thermal decomposition of AsH3, the flow rate of AsH3 is 300-2000sccm, the epitaxial growth temperature of the P-face waveguide layer 3 is 600-750°C, the epitaxial growth pressure is 80-200mbar, and the total thickness of the P-face confinement layer 2 and the P-face waveguide layer 3 is 1-5μm. In this embodiment, the material of the P-face 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 900sccm, the epitaxial growth temperature is 750℃, the epitaxial growth pressure is 200mbar, and the thickness is 1000nm.

[0027] The material of the active layer 4 is indium gallium arsenide, and the active layer 4 is fixedly connected to the P-side waveguide layer 3. The epitaxial growth of the active layer 4 adopts AsH3 thermal decomposition, the flow rate of AsH3 is 50-100 sccm, the epitaxial growth temperature of the active layer 4 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 4 is In 0.08 GaAs. The epitaxial growth temperature of the active layer 4 is 680° C., the epitaxial growth pressure is 160 mbar, the thickness is 6 nm, and the flow rate of AsH3 is 80 sccm.

[0028] The material of the N-side waveguide layer 5 is gallium aluminum arsenide, and the N-side waveguide layer 5 is fixedly connected to the active layer 4. The N-side waveguide layer 5 is doped with silicon, and the doping concentration of silicon is 5×10 16 -3×10 18 cm -3 The epitaxial growth of the N-side waveguide layer 5 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 5 is 600-750°C, and the epitaxial growth pressure is 80-200 mbar. In this embodiment, the material of the N-side waveguide layer 5 is Al 0.4 GaAs. The silicon doping concentration of the N-side waveguide layer 5 is 8×10 16 cm -3 , the flow rate of AsH3 is 1000sccm, the epitaxial growth temperature is 720℃, the epitaxial growth pressure is 150mbar, and the thickness is 1000nm.

[0029] The material of the N-side limiting layer 6 is gallium aluminum arsenide, and the N-side limiting layer 6 is fixedly connected to the N-side waveguide layer 5. The N-side limiting layer 6 is doped with silicon, and the doping concentration of silicon is 5×10 16 -3×10 18 cm -3。The epitaxial growth of the N-side confinement 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 confinement layer 6 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 6 is Al 0.2 GaAs. The doping concentration of silicon element in the N-side confinement layer 6 is 5×10 16 cm -3 , the flow rate of AsH3 is 1100 sccm, the epitaxial growth temperature is 740 °C, the epitaxial growth pressure is 200 mbar, and the thickness is 500 nm.

[0030] There are 3 - 50 groups of strain buffer layers. In this embodiment, there are 10 groups of strain buffer layers. Each group of strain buffer layers includes a strain layer 7 and a buffer layer 8 arranged in sequence.

[0031] The material of the strain layer 7 is Al x Ga 1-x In y P, where 0 < x < 1, 0 < y < 0.48, and one of the strain layers 7 is fixedly connected to the N-side confinement layer 6. The epitaxial growth of the strain layer 7 is carried out by thermal decomposition of PH3. The flow rate of PH3 is 300 - 2000 sccm. The epitaxial growth temperature of the strain layer 7 is 600 - 750 °C, and the epitaxial growth pressure is 80 - 200 mbar. In this embodiment, the materials of the ten strain layers 7 are all Al 0.3 Ga 0.7 In 0.3 P, the flow rate of PH3 is 500 sccm. The epitaxial growth temperature of the strain layer 7 is 690 °C, and the epitaxial growth pressure is 140 mbar.

[0032] The material of the buffer layer 8 is gallium arsenide, and the buffer layer 8 is fixedly connected to the strain layer 7. The total thickness of the buffer layer 8 is 200 nm. Therefore, in this embodiment, the thickness of each buffer layer 8 is 20 nm.

[0033] The material of the substrate 9 is gallium arsenide, and the substrate 9 is fixedly connected to a buffer layer 8. In this embodiment, the size of the substrate 9 is 4 inches, and the thickness is 625 μm. The sizes of the contact layer 1, P-side confinement layer 2, P-side waveguide layer 3, active layer 4, N-side waveguide layer 5, N-side confinement layer 6, strain layer 7, and buffer layer 8 are all equal to that of the substrate 9.

[0034] In this embodiment, the total compressive stress generated by the contact layer 1, P-side confinement layer 2, P-side waveguide layer 3, active layer 4, N-side waveguide layer 5, and N-side confinement layer 6 is 283 ppm×500 nm + 567 ppm×1000 nm + 5731 ppm×6 nm + 567 ppm×1000 nm + 283 ppm×500 nm = 1451386.

[0035] Since the material of the strain layer 7 is Al 0.3 Ga 0.7 In 0.3 P, it can be concluded through XRD analysis software that the stress difference between the strain layer 7 and the buffer layer 8 is -12000ppm. In this embodiment, the total thickness of the strain layer 7 is 1451386 / 12000=121nm, so the thickness of each strain layer 7 is 12.1nm.

[0036] Example 2

[0037] The difference between Example 2 and Example 1 is that in Example 2, 50 groups of strain buffer layers are provided.

[0038] In this embodiment, since the values ​​of x and y remain unchanged, the total thickness of the strain layer 7 and the buffer layer 8 remains unchanged. Therefore, the thickness of each strain layer 7 is 2.42 nm, and the thickness of each buffer layer 8 is 4 nm.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 is that in Example 3, three groups of strain buffer layers are provided.

[0041] In this embodiment, since the values ​​of x and y remain unchanged, the total thickness of the strain layer 7 and the buffer layer 8 remains unchanged, so the thickness of each strain layer 7 is 40 nm, and the thickness of each buffer layer 8 is 67 nm.

[0042] Combining Examples 1-3, it can be seen that the thickness of the strain layer 7 is determined by the stress difference between the strain layer 7 and the buffer layer 8, and the total compressive stress generated by the contact layer 1, the P-face confinement layer 2, the P-face waveguide layer 3, the active layer 4, the N-face waveguide layer 5 and the N-face confinement layer 6. The stress difference between the strain layer 7 and the buffer layer 8 is determined by the values ​​of x and y. It can be concluded from the XRD analysis software that when y<0.48, Al x Ga 1-x In y The lattice of P is smaller than that of GaAs, which generates tensile stress between the strain layer 7 and the buffer layer 8. The 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 the warping of the epitaxial wafer, reduce the fragmentation rate, cleave the cavity lines, improve the yield, and improve the defect of the laser epitaxial structure with large compressive stress and severe warping.

[0043] Compared with directly setting a strain layer and a buffer layer, setting a cyclic strain buffer layer can not only control the total stress of the structure, but also reduce the thickness of each layer of gallium arsenide and AlxGa1-xInyP, thereby improving the interface quality between the strain layer 7 and the buffer layer 8 and enhancing the reliability of the entire semiconductor laser structure.

[0044] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A semiconductor laser structure with a cyclic strain buffer layer, comprising an epitaxial structure layer and a substrate (9), characterized in that: A plurality of groups of strain buffer layers are provided between the epitaxial structure layer and the substrate (9). Each group of the strain buffer layers includes a strain layer (7) and a buffer layer (8). The material of the buffer layer (8) is gallium arsenide, and the material of the strain layer (7) is Al x Ga 1-x In y P, where 0 < x < 1 and 0 < y < 0.

48. The strain buffer layers are provided in 3 - 50 groups.

2. The semiconductor laser structure with a cyclic strain buffer layer according to claim 1, characterized in that: The total thickness of the buffer layer (8) is 200 nm.

3. The semiconductor laser structure with a cyclic strain buffer layer according to claim 1, characterized in that: The epitaxial growth temperature of the strain layer (7) is 600-750° C., the epitaxial growth pressure is 80-200 mbar, and the epitaxial growth of the strain layer (7) adopts PH3 thermal decomposition, and the flow rate of PH3 is 300-2000 sccm.

4. The semiconductor laser structure with a cyclic strain buffer layer according to claim 1, characterized in that: The epitaxial structure layer comprises a contact layer (1), a P-face limiting layer (2), a P-face waveguide layer (3), an active layer (4), an N-face waveguide layer (5) and an N-face limiting layer (6) which are arranged in sequence, and the N-face limiting layer (6) is located between the N-face waveguide layer (5) and the substrate (9).

5. The semiconductor laser structure with a cyclic strain buffer layer according to claim 4, characterized in that: The materials of the N-side limiting layer (6) and the N-side waveguide layer (5) are both gallium aluminum arsenide, the epitaxial growth temperature of the N-side limiting layer (6) and the N-side waveguide layer (5) is 600-750° C., and the epitaxial growth pressure is 80-200 mbar.

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

7. The semiconductor laser structure with a cyclic strain buffer layer according to claim 4, characterized in that: The material of the active layer (4) is indium gallium aluminum, the epitaxial growth temperature of the active layer (4) is 580-750° C., and the epitaxial growth pressure is 80-200 mbar.

8. The semiconductor laser structure with a cyclic strain buffer layer according to claim 4, 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 cyclic strain buffer 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 cyclic strain buffer 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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