InP-based small-divergence-angle high-power semiconductor laser structure

Abstract

The InP-based small-divergence-angle high-power semiconductor laser structure comprises a laser, electrodes are arranged on the upper side and the lower side of the laser, and the laser comprises an electrode contact layer, a cover layer, a corrosion stopping layer, an electron direction transition layer, an electron blocking layer, an active region, a hole blocking layer, a waveguide layer, a buffer layer and a substrate which are sequentially arranged from top to bottom. A double-trench structure is etched on the electrode contact layer and the cover layer, and the electrode contact layer and the substrate are both connected with the electrode. According to the InP-based small-divergence-angle high-power semiconductor laser structure, only one-time epitaxy is needed, complex process preparation is not needed, the thick N-type waveguide layer is adopted to limit a light field, and due to the fact that the waveguide layer is thick and the light field of a mode field in the vertical direction is large, a low vertical-direction divergence angle is obtained. According to the structure provided by the invention, the quantum well active region does not need to be etched through, so that the laser with the structure is relatively long in service life and relatively good in reliability.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor lasers, and in particular to an InP-based small divergence angle high-power semiconductor laser structure. Background Art

[0002] In the past few decades, the development of semiconductor lasers with small divergence angle, high power, high reliability and effective fundamental transverse mode emission has been a challenge. In recent years, with the vigorous development of optical communication and lidar industries, the demand for high-power lasers in the 1310nm and 1550nm bands has become increasingly strong. For traditional fundamental transverse mode semiconductor lasers in this band, since the light-emitting area is a long strip, it is several microns parallel to the junction direction and only tens of nanometers perpendicular to the junction direction. Due to the diffraction effect, the divergence angle in the vertical direction is large, generally 35 to 50 degrees, and less than 20 degrees in the horizontal direction. At the same time, the small light-emitting area will lead to a high power density at the light-emitting end face, limiting its maximum output power.

[0003] In order to achieve a small divergence angle in the vertical direction, the following two structures are currently used: mode expansion layer structure and planar coupled optical waveguide structure. The high refractive index mode expansion layer pulls the light field up or down from the active area, thereby increasing the vertical divergence angle. Although this structure can reduce the divergence angle, the light field is still mainly concentrated in the active area, and the power density is still high, which limits its output power. Although the planar coupled optical waveguide structure has a smaller divergence angle and a larger mode field, it needs to etch through the quantum well active area. For the InP / AlGaInAs material system, it is easy to introduce surface defects on the exposed quantum well sidewalls during the etching process. When the device is working, these surface defects are introduced into the quantum well to form non-radiative recombination centers, which limits the reliability and working time of the device and is not conducive to industrialization. Summary of the invention

[0004] In view of the technical problem that the prior art easily introduces surface defects on the exposed quantum well side walls during the etching process, the present invention proposes an InP-based small divergence angle high-power semiconductor laser structure, which can obtain a near-circular spot. At the same time, the near-field spot size in the vertical direction is large, which reduces the end face optical power density, achieves higher internal quantum efficiency and lower loss, and realizes high-power near-circular spot output.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is implemented as follows: an InP-based small divergence angle high-power semiconductor laser structure includes a laser, electrodes are arranged on the upper side and the lower side of the laser, the laser includes an electrode contact layer, a cover layer, an etching stop layer, an electron transition layer, an electron blocking layer, an active area, a hole blocking layer, a waveguide layer, a buffer layer and a substrate arranged in sequence from top to bottom, a double groove structure is etched on the electrode contact layer and the cover layer, and the electrode contact layer and the substrate are both connected to the electrode.

[0006] The double groove structure includes two groove structures and a ridge-type table surface. Both groove structures penetrate the electrode contact layer and the cover layer. The P-surface electrode is arranged on the top of the ridge-type table surface.

[0007] The electrodes include a P-side electrode and an N-side electrode, the P-side electrode is connected to the electrode contact layer, and the N-side electrode is connected to the substrate.

[0008] The shapes of the two groove structures are consistent with each other, and the two groove structures are symmetrically distributed around the center of the ridge-shaped table surface.

[0009] At least two quantum wells are arranged in parallel in the active region.

[0010] A plurality of band gaps are evenly arranged in the electron blocking layer, and the band gap width is greater than the quantum well width.

[0011] The top of the electrode contact layer, the two walls of the groove structure and the bottom of the groove structure are all provided with a passivation film layer.

[0012] The substrate is made of N-type InP material, the buffer layer is made of N-type InP material, the waveguide layer is made of N-type InGaAsP material, the hole blocking layer is made of non-doped InGaAsP material, the active region is made of non-doped AlGaInAs material, the electron blocking layer is made of non-doped AlGaInAs material, the electron transition layer is made of P-type doped InP material, the corrosion stop layer is made of P-type doped InGaAsP material, the cap layer is made of P-type doped InP material, and the electrode contact layer is made of P-type heavily doped InGaAsP material.

[0013] The passivation film layer is a silicon dioxide passivation film.

[0014] The N-side electrode is a gold-germanium-nickel electrode, and the P-side electrode is a titanium-platinum-gold electrode.

[0015] The beneficial effects of the present invention are as follows: the utility model can realize a small divergence angle, a fundamental transverse mode, and high-power light output at different ridge widths within a range of 2 microns to 6 microns; at the same time, an etching stop layer is used for blocking, so that the ridge waveguide is easy to prepare; when etching the ridge waveguide, it is not necessary to etch to the active area, and the active area does not need to be exposed to the atmosphere, and surface defects are not introduced, so the reliability is high and the working life is long.

[0016] The InP-based high-power semiconductor laser structure with a small divergence angle of the present application only requires one epitaxy and does not require complicated process preparation. The structure uses a thick N-type waveguide layer to limit the light field. Since the waveguide layer is thicker, the mode field is larger in the vertical direction, thereby obtaining a lower vertical divergence angle. By designing the refractive index of the N-type waveguide layer, the fundamental transverse mode light confinement factor in the vertical direction is greater than each high-order transverse mode, thereby obtaining fundamental transverse mode lasing under different ridge widths. At the same time, the structure does not need to carve through the quantum well active area, so that the laser of the structure has a longer working life and better reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a diagram of the epitaxial growth structure of the InP-based small divergence angle high-power semiconductor laser structure proposed in the utility model.

[0019] Figure 2 This is a chip cross-sectional view of the InP-based small divergence angle high-power semiconductor laser structure proposed in the utility model.

[0020] Figure 3 This is a measured divergence angle diagram of the InP-based small divergence angle high-power semiconductor laser structure chip proposed in the utility model.

[0021] Figure 4 This is the power-current curve of the InP-based small divergence angle high-power semiconductor laser structure chip proposed by the utility model.

[0022] In the figure, 1 is a substrate, 2 is a buffer layer, 3 is a waveguide layer, 4 is a hole blocking layer, 5 is an active area, 6 is an electron blocking layer, 7 is an electron transition layer, 8 is an etching stop layer, 9 is a cap layer, 10 is an electrode contact layer, 11 is a double groove structure, 12 is a passivation film layer, 13 is a P-side electrode, and 14 is an N-side electrode 14. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, an InP-based small divergence angle high-power semiconductor laser structure includes an InP-based small divergence angle high-power semiconductor laser structure, including a laser, electrodes are arranged on the upper and lower sides of the laser, and the laser includes an electrode contact layer 10, a cover layer 9, an etching stop layer 8, an electron transition layer 7, an electron blocking layer 6, an active area 5, a hole blocking layer 4, a waveguide layer 3, a buffer layer 2 and a substrate 1 arranged in sequence from top to bottom, and a double groove structure 11 is etched on the electrode contact layer 10 and the cover layer 9, and the electrode contact layer 10 and the substrate 1 are both connected to the electrode. Among them, the electrode includes a P-side electrode 13 and an N-side electrode 14, the P-side electrode 13 is connected to the electrode contact layer 10, and the N-side electrode 14 is connected to the substrate 1. As shown Figure 2 As shown, the double groove structure 11 includes two groove structures and a ridge-type table. Both groove structures penetrate the electrode contact layer 10 and the cover layer 9. The P-side electrode 13 is arranged on the top of the ridge-type table. The two groove structures have the same shape and are symmetrically distributed around the center of the ridge-type table.

[0025] The double groove structure 11 is formed into a ridge-type terrace by photolithography, dry etching and wet etching. The electrode contact layer 10 and part of the cover layer 9 are removed by dry etching. The cover layer 9 is removed by wet etching. The etching stops on the etching stop layer 8 to form the double groove structure 11.

[0026] The top of the quantum well 10, the two walls of the trench structure and the bottom of the trench structure are all provided with a passivation film layer 12, while the top of the ridge terrace is not provided with a passivation film layer 12. The passivation film layer 12 is mainly used to form a passivation film to prevent the epitaxial material from being oxidized.

[0027] Specifically, the substrate 1 is mainly used for epitaxial growth of various layers of laser materials, and the substrate 1 is made of N-type InP material. The buffer layer 2 is made of N-type InP material, and the buffer layer 2 is mainly used to form a high-quality epitaxial surface, reduce the stress between the substrate 1 and other layers, eliminate defects of the substrate 1, and prevent defects from propagating to other layers, so as to facilitate the growth of other layers of laser materials.

[0028] The waveguide layer 3 is made of N-type InGaAsP material, and its purpose is to limit the optical field of the laser. The waveguide layer 3 is relatively thick. Since the vertical divergence angle of less than 20 degrees can only be obtained when the waveguide layer 3 is greater than 4um, a thicker waveguide layer 3 is required to expand the optical field of the laser, increase the spot size in the vertical direction of the laser, reduce the optical power density of the end face, and improve the beam quality. The material refractive index of the waveguide layer 3 should be reasonably selected according to the hole blocking layer 4, the active area 5 and the electron blocking layer 6. If it is too large, it will easily lead to high-order mode lasing, and if it is too low, the optical field cannot be effectively expanded.

[0029] The hole blocking layer 4 is made of non-doped InGaAsP material, and is mainly used to block the holes in the active area 5 from diffusing to the waveguide layer 3, thereby improving the internal quantum efficiency of the laser and reducing the loss of the laser when working at a large current.

[0030] The active region 5 is made of non-doped AlGaInAs material, and is mainly used to provide optical gain for the laser and determine the laser lasing wavelength. The active region 5 is a multi-quantum well structure, containing 2-5 quantum wells, and the quantum wells are mainly used to limit the injected carriers and improve the slope efficiency of the laser.

[0031] The electron blocking layer 6 is made of non-doped AlGaInAs material and is mainly used to block electrons in the active region 5 from diffusing into the transition layer 7. Multiple band gaps are evenly arranged in the electron blocking layer 6, and the band gap width is greater than the quantum well width.

[0032] The transition layer 7 is made of P-type doped InP material. The transition layer 7 is mainly used for transitioning the growth of the etching stop layer 8 . Meanwhile, the band gap of InP is relatively large, and it can block the electron leakage of the active area 5 .

[0033] The etching stop layer 8 is made of P-type doped InGaAsP material. The etching stop layer 8 is mainly used to stop the wet etching solution on the etching stop layer 8 when making the ridge waveguide, protecting the active area 5 from being exposed to the atmosphere, while ensuring a high yield rate for the device ridge waveguide preparation.

[0034] The cap layer 9 is made of P-type doped InP material, which is used to make ridge waveguide. The cap layer 9 has a height of more than 1.5 microns, which reduces the stress of the etch stop layer 8 and the electrode contact layer 10 and realizes the transition from the etch stop layer 8 to the electrode contact layer 10.

[0035] The electrode contact layer 10 is made of P-type heavily doped InGaAsP material, the purpose of which is to form a good ohmic contact with the subsequent electrode 13. The medium doping is used to reduce the series resistance of the laser and increase the electro-optical / conversion efficiency.

[0036] The N-side electrode 14 is a gold-germanium-nickel electrode, which is made under the substrate 1 and is made of gold-germanium-nickel material, and its purpose is to reduce the series resistance of the device. The P-side electrode 13 is a titanium-platinum electrode, which is made on the electrode contact layer 10 on the top of the ridge-shaped table, and its purpose is to form an ohmic contact with the electrode contact layer 10 to reduce the series resistance.

[0037] When in use, a voltage is applied to both ends of the laser through the N-side electrode 14 and the P-side electrode 13 , and the laser outputs laser light through the active region 5 .

[0038] like Figure 3 As shown, Figure 3The far-field divergence angle of a laser with a cavity length of 2000 microns, a ridge waveguide width of 5 microns, and a wavelength of 1550nm prepared using the epitaxial structure of the utility model is demonstrated. The half-width at half-maximum of the horizontal divergence angle is 8.37 degrees, and the half-width at half-maximum of the vertical divergence angle is 18.57 degrees.

[0039] like Figure 4 As shown, the power current curve of a laser with a cavity length of 2000 microns, a ridge waveguide width of 5 microns, and a wavelength of 1550nm prepared using the epitaxial structure of the utility model is shown.

[0040] The InP-based high-power semiconductor laser structure with a small divergence angle of the present application only requires one epitaxy and does not require complicated process preparation. The structure uses a thick N-type waveguide layer to limit the light field. Since the waveguide layer is thicker, the mode field is larger in the vertical direction, thereby obtaining a lower vertical divergence angle. By designing the refractive index of the N-type waveguide layer, the fundamental transverse mode light confinement factor in the vertical direction is greater than each high-order transverse mode, thereby obtaining fundamental transverse mode lasing under different ridge widths. At the same time, the structure does not need to carve through the quantum well active area, so that the laser of the structure has a longer working life and better reliability.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An InP-based small divergence angle high-power semiconductor laser structure, characterized in that: The invention comprises a laser, wherein electrodes are arranged on the upper and lower sides of the laser, and the laser comprises an electrode contact layer (10), a cover layer (9), an etching stop layer (8), an electron transition layer (7), an electron blocking layer (6), an active region (5), a hole blocking layer (4), a waveguide layer (3), a buffer layer (2) and a substrate (1) which are arranged in sequence from top to bottom; a double groove structure (11) is etched on the electrode contact layer (10) and the cover layer (9); and the electrode contact layer (10) and the substrate (1) are both connected to the electrodes.

2. The InP-based small divergence angle high-power semiconductor laser structure according to claim 1, characterized in that: The double groove structure (11) comprises two groove structures and a ridge-type table surface, the two groove structures both penetrate the electrode contact layer (10) and the cover layer (9), and the P-surface electrode (13) is arranged on the top of the ridge-type table surface.

3. The InP-based small divergence angle high-power semiconductor laser structure according to claim 2, characterized in that: The electrode comprises a P-side electrode (13) and an N-side electrode (14); the P-side electrode (13) is connected to the electrode contact layer (10), and the N-side electrode (14) is connected to the substrate (1).

4. The InP-based small divergence angle high-power semiconductor laser structure according to claim 2 or 3, characterized in that: The two groove structures have the same shape, and are symmetrically distributed around the center of the ridge-shaped table.

5. The InP-based small divergence angle high-power semiconductor laser structure according to claim 4, characterized in that: At least two quantum wells are arranged in parallel in the active region (5).

6. The InP-based small divergence angle high-power semiconductor laser structure according to claim 5, characterized in that: A plurality of band gaps are evenly arranged in the electron blocking layer (6), and the band gap width is greater than the quantum well width.

7. The InP-based small divergence angle high-power semiconductor laser structure according to claim 6, characterized in that: The top of the electrode contact layer (10), the two walls of the groove structure and the bottom of the groove structure are all provided with a passivation film layer (12).

8. The InP-based small divergence angle high-power semiconductor laser structure according to claim 7, characterized in that: The substrate (1) is made of N-type InP material, the buffer layer (2) is made of N-type InP material, the waveguide layer (3) is made of N-type InGaAsP material, the hole blocking layer (4) is made of non-doped InGaAsP material, the active region (5) is made of non-doped AlGaInAs material, the electron blocking layer (6) is made of non-doped AlGaInAs material, the electron transition layer (7) is made of P-type doped InP material, the etching stop layer (8) is made of P-type doped InGaAsP material, the cap layer (9) is made of P-type doped InP material, and the electrode contact layer (10) is made of P-type heavily doped InGaAsP material.

9. The InP-based small divergence angle high-power semiconductor laser structure according to claim 7 or 8, characterized in that: The passivation film layer (12) is a silicon dioxide passivation film.

10. The InP-based small divergence angle high-power semiconductor laser structure according to claim 3, characterized in that: The N-side electrode (14) is a gold-germanium-nickel electrode, and the P-side electrode (13) is a titanium-platinum-gold electrode.

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