Tunnel junction cascaded multi-active-area distributed feedback semiconductor laser and manufacturing method thereof

Abstract

The invention discloses a tunnel junction cascade multi-active-region distributed feedback semiconductor laser and a manufacturing method thereof. An epitaxial structure of the tunnel junction cascade multi-active-region distributed feedback semiconductor laser comprises a substrate, a buffer layer, a light-emitting region, a grating layer, a regrowth layer and a contact layer, the light-emitting area comprises at least two light-emitting units, each light-emitting unit comprises an active area, tunnel junctions are arranged between the adjacent light-emitting units, and the adjacent light-emitting units are electrically connected through the tunnel junctions to form a cascade structure; the grating layer comprises a lower spacing layer, a grating structure and an upper spacing layer; the upper spacer layer, the regrowth layer and the contact layer are made of homogeneous materials, and the doping concentration of the regrowth layer is between the doping concentration of the upper spacer layer and the doping concentration of the contact layer. The laser has excellent working efficiency under the condition of low threshold current, stray capacitance is effectively reduced by the cascade structure, the single-mode lasing stability of the distributed feedback structure under a specific wavelength is not influenced, the light beam quality of the device is improved by introducing the regrowth layer, and the laser has the advantages of high efficiency, high reliability and high stability.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor lasers, in particular to the design of high-efficiency and high-stability semiconductor lasers for high-speed communication, laser arrays and high-power laser applications, and specifically to a tunnel junction cascade multi-active region distributed feedback semiconductor laser and a manufacturing method thereof. Background Art

[0002] With the rapid development of information technology, especially in the fields of optical communication, lidar, sensors, and laser printing, the performance requirements of semiconductor lasers are constantly increasing. Distributed feedback (DFB) semiconductor lasers are widely used in these fields due to their excellent single-mode output characteristics. It is a structure widely used in semiconductor lasers, characterized by the stable selection of the laser output light wavelength by embedding a grating structure in the gain medium. DFB lasers are usually composed of a semiconductor light source (usually a quantum well material) and a periodic grating grown on it. This grating will produce Bragg reflection in a specific wavelength range, so that the laser outputs single-mode laser at that wavelength.

[0003] Current DFB lasers usually adopt a single active region design. Although it can achieve single-mode lasing, with the increase in demand, such as high power output and high efficiency, the single active region structure can no longer meet the requirements. The performance improvement of traditional DFB lasers is limited by current distribution, capacitance effects, and thermal management issues. In addition, existing grating designs usually make it difficult to ensure the stability of the laser while maintaining high efficiency. Summary of the invention

[0004] The main purpose of the present invention is to provide a tunnel junction cascade multi-active region distributed feedback semiconductor laser to solve the shortcomings of the distributed feedback semiconductor laser in the prior art in terms of performance requirements such as high efficiency, high power output, thermal management, current distribution uniformity and beam quality.

[0005] To achieve the above-mentioned purpose, the present invention provides a tunnel junction cascade multi-active region distributed feedback semiconductor laser, whose epitaxial structure includes a substrate, a buffer layer, a light-emitting region, a grating layer, a regrown layer and a contact layer from bottom to top; the light-emitting region includes at least two light-emitting units stacked up and down, wherein each light-emitting unit includes an active region and respectively confined heterostructure layers arranged on the upper and lower sides of the active region, and tunnel junctions are arranged between adjacent light-emitting units, and are electrically connected through the tunnel junctions to form a cascade structure; the grating layer includes a lower spacer layer, a grating structure and an upper spacer layer from bottom to top; the upper spacer layer, the regrown layer and the contact layer are homogeneous materials, and the doping concentration of the upper spacer layer is ≤ the doping concentration of the regrown layer < the doping concentration of the contact layer.

[0006] Optionally, the tunnel junction is a reverse-biased PN junction, including a P-type material layer and an N-type material layer, the thickness of the P-type material layer is 8nm-13nm, and the thickness of the N-type material layer is 8nm-13nm.

[0007] Optionally, the P-type material layer is heavily doped P-type indium phosphide or heavily doped P-type indium gallium arsenide, and the N-type material layer is heavily doped N-type indium phosphide.

[0008] Optionally, the active region includes multiple quantum wells; the multiple quantum wells include quantum wells and potential barriers, the quantum wells are compressive strain quantum wells, and the potential barriers are tensile strain potential barriers; the number of periods of the multiple quantum wells is 5 to 9.

[0009] The grating layer is located above the respectively confined heterostructure layer of the top light-emitting unit, and is used to realize the distributed feedback function to ensure the single-mode output of the laser. Optionally, the grating structure is composed of a P-type lightly doped indium gallium arsenic phosphide and a P-type lightly doped indium phosphorus to form a periodically arranged structure in the light-emitting direction of the laser, and the grating period is precisely designed according to the specific wavelength of the laser to realize the distributed feedback function; the material of the lower spacer layer and the upper spacer layer is P-type lightly doped indium phosphorus. DFB is side-emitting, and the light-emitting direction is perpendicular to the up and down direction of the above-mentioned epitaxial structure stack. The grating structure provides a feedback effect through a periodically changing refractive index, selectively reflecting light of a specific wavelength, thereby ensuring the single-mode operating characteristics of the laser. The spacer layer is used to ensure good electrical isolation between the grating and the light-emitting unit.

[0010] Optionally, the thickness of the upper spacer layer is 8 to 15 nm; the thickness of the regrown layer is 1000 to 1400 nm; and the thickness of the contact layer is 8 to 15 nm.

[0011] Optionally, the number of the light emitting units is 2 to 5.

[0012] Optionally, the regrown layer includes at least two stacked doping concentration layers, and the doping concentration of the upper doping concentration layer is greater than the doping concentration of the lower doping concentration layer. The upper spacer layer is used for optical isolation and transition of the grating layer. The regrown layer is used to support the contact layer and optimize current transmission. It is thicker and its function is more inclined to electrical optimization. The doping concentration of the doping concentration layer adjacent to the upper spacer layer of the regrown layer is preferably the same as that of the upper spacer layer to achieve a smooth functional transition. The same doping concentration can reduce the doping concentration mutation on the interface, which helps to reduce the interface resistance and possible defect generation.

[0013] Optionally, the substrate is an N-type indium phosphorus substrate, and the buffer layer is an N-type indium phosphorus buffer layer; the laser further includes a top ohmic contact electrode and a bottom ohmic contact electrode disposed at the upper and lower ends of the epitaxial structure.

[0014] The above heavy doping and light doping are relative. Preferably, the heavy doping of the tunnel junction refers to a doping concentration range of 1×10 19 cm -3 Up to 5×10 20 cm -3 The light doping of the grating structure refers to a doping concentration range of 1×10 16 cm -3 Up to 5×10 17 cm -3 Preferably, the upper spacer layer, the regrown layer and the contact layer are all p-type indium phosphorus materials, wherein the doping concentration of the upper spacer layer is in the range of 1×10 17 cm -3 Up to 2×10 18 cm -3 , the doping concentration of the regrown layer ranges from 1×10 17 cm -3 Up to 2×10 18 cm -3 , the doping concentration of the contact layer ranges from 1×10 18 cm -3 Up to 5×10 19 cm -3 .

[0015] A method for manufacturing the above-mentioned tunnel junction cascade multi-active region distributed feedback semiconductor laser, comprising:

[0016] Using an epitaxial growth process, a buffer layer and a light-emitting region are sequentially grown on a substrate, wherein the light-emitting region includes light-emitting units and tunnel junctions that are alternately grown;

[0017] A grating layer is fabricated on the last light-emitting unit, wherein the grating layer is formed into a grating structure through an etching process;

[0018] A regrown layer and a contact layer are sequentially grown on the grating layer.

[0019] Optionally, the manufacturing of the grating layer includes:

[0020] (1) growing a P-type indium phosphorus material on the last light-emitting unit to form a lower spacer layer;

[0021] (2) etching the lower spacer layer to form periodic grating grooves;

[0022] (3) filling the grating groove with a P-type indium gallium arsenic phosphide material to form a grating structure;

[0023] (4) Grow another layer of P-type indium phosphorus material on the grating structure to form an upper spacer layer.

[0024] The beneficial effects of the present invention are:

[0025] 1. Improve photoelectric conversion efficiency: By introducing a tunnel junction cascade multi-active region design, the present invention can optimize current distribution and reduce current loss, thereby significantly improving photoelectric conversion efficiency. The multi-active region design increases the gain characteristics of the laser, enabling the laser to achieve higher optical output power under lower current conditions, thereby improving the overall working efficiency of the laser.

[0026] 2. Reduce threshold current and power consumption: The tunnel junction structure provides a low current loss path between multiple active areas, reducing current loss and the laser's startup current (threshold current), allowing the laser to operate at lower power consumption. This innovative design effectively improves the energy efficiency of the laser, making it more suitable for low power consumption and high efficiency applications.

[0027] 3. Maintaining single-mode lasing stability: The grating layer ensures that the laser achieves single-mode lasing at a specific wavelength through distributed feedback. The grating structure provides feedback through periodically changing refractive index, allowing the laser to work stably in a single-mode state, avoiding multi-mode oscillation, thereby ensuring the high-quality beam and stable wavelength characteristics of the laser output.

[0028] 4. High reliability and long-term stability: The innovative structure of the tunnel junction, grating layer and regrown layer of the present invention not only improves the working efficiency of the laser, but also enhances its long-term operating reliability. By optimizing material selection and structural design, the failure rate is reduced and the stability and durability of the laser in harsh working environments are improved.

[0029] 5. Applicable to a variety of high-demand application scenarios: The laser of the present invention exhibits excellent performance in terms of high efficiency, low power consumption, single-mode lasing stability and high beam quality. It is widely used in optical communications, laser ranging, medical diagnosis, laser radar and other occasions that require high efficiency and high stability.

[0030] Other features and advantages of the present invention will be set forth in the following description, and in part will be apparent from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the main structure of a tunnel junction cascade multi-active region distributed feedback semiconductor laser of an embodiment in which two tunnel junctions are arranged;

[0032] Figure 2 for Figure 1 The main structural diagram of the light-emitting unit in the tunnel junction cascade multi-active region distributed feedback semiconductor laser shown;

[0033] Figure 3 for Figure 1The main structural diagram of the grating layer in the tunnel junction cascade multi-active region distributed feedback semiconductor laser shown;

[0034] Figure 4 for Figure 1 The simulated PIV curve of the tunnel junction cascade multi-active region distributed feedback semiconductor laser shown;

[0035] Figure 5 for Figure 1 The spectrum diagram of the tunnel junction cascade multi-active region distributed feedback semiconductor laser shown;

[0036] Wherein, the figure numbers of the above drawings are:

[0037] 0. Bottom ohmic contact electrode; 1. substrate; 2. first buffer layer; 3. second buffer layer; 4. first light-emitting unit; 401. lower confinement layer; 402. lower waveguide layer; 403. multiple quantum well; 404. upper waveguide layer; 405. upper confinement layer; 5. first tunnel junction; 6. second light-emitting unit; 7. second tunnel junction; 8. third light-emitting unit; 9. grating layer; 901. lower spacer layer; 902. grating structure; 903. upper spacer layer; 10. regrown layer; 11. contact layer; 12. top ohmic contact electrode. DETAILED DESCRIPTION

[0038] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The various drawings of the present invention are only for illustration to make it easier to understand the present invention, and the specific proportions can be adjusted according to design requirements. The upper and lower relationships of the relative elements and the definitions of the front / back in the figures described in the text should be understood by those skilled in the art to refer to the relative positions of the components, so they can all be flipped to present the same components, which should all fall within the scope disclosed in this specification.

[0039] The embodiment proposes a tunnel junction cascade multi-active region distributed feedback quantum well semiconductor laser, whose epitaxial structure includes, from bottom to top, a substrate, a buffer layer, a light-emitting region, a grating layer, a regrown layer and a contact layer; the light-emitting region includes at least two light-emitting units stacked up and down, wherein each light-emitting unit includes an active region and respectively confined heterostructure layers arranged on the upper and lower sides of the active region, a tunnel junction is provided between adjacent light-emitting units, and they are electrically connected through the tunnel junction to form a cascade structure; the grating layer includes, from bottom to top, a lower spacer layer, a grating structure and an upper spacer layer; the upper spacer layer, the regrown layer and the contact layer are homogeneous materials, and the doping concentration of the upper spacer layer is ≤ the doping concentration of the regrown layer < the doping concentration of the contact layer.

[0040] In the active area, multiple quantum wells are included, and two adjacent quantum wells are connected by potential barriers. The function of the potential barrier is to isolate different quantum wells, so that electrons and holes can complete recombination in one quantum well and continue to flow into the next quantum well for recombination. The quantum well is preferably a compressive strain quantum well formed by indium gallium arsenic phosphide material, and the potential barrier is preferably a tensile strain barrier formed by indium gallium arsenic phosphide material. The number of periods of the multiple quantum wells is 5-9, preferably 7-8. The tunnel junction connects multiple light-emitting units in series to form a cascade structure. In this way, the gain and output power of the laser can be significantly improved. The active area of ​​each light-emitting unit can provide gain for the laser, so the cascade of multiple active areas can effectively increase the gain, and also enable the laser to handle higher current and power.

[0041] The tunnel junction is a reverse biased PN junction, the thickness of the P-type material is 8nm to 13nm, and the thickness of the N-type material is 8nm to 13nm. The tunnel junction can be composed of a stacked P-type indium phosphide layer and an N-type indium phosphide layer or a P-type indium phosphide layer and an N-type indium gallium arsenide layer.

[0042] As a preferred solution of this embodiment, each light-emitting unit includes a lower confinement layer, a lower waveguide layer, an active region, an upper waveguide layer, and an upper confinement layer. The lower confinement layer, the upper confinement layer, and the waveguide layer together constitute a confined heterostructure, thereby effectively controlling the spatial distribution of carriers and promoting the recombination of carriers in the active region.

[0043] Preferably, the number of the light-emitting units is 2 to 5, preferably 2-3.

[0044] Preferably, the regrown layer includes at least two stacked doping concentration layers, and the doping concentration of the upper doping concentration layer is greater than the doping concentration of the lower doping concentration layer.

[0045] In the light-emitting direction of the laser, the grating layer uses a combination of InGaAsP material and InP material to form a periodic arrangement structure. This structure can optimize the optical feedback characteristics of the laser and improve the single-mode output capability and spectral stability by precisely controlling the grating period, depth and other parameters. The combination of InGaAsP and InP materials, due to its excellent bandgap characteristics and good optical properties, can effectively support the efficient operation of the laser within the designed wavelength range.

[0046] The method for manufacturing the tunnel junction cascade multi-active region distributed feedback semiconductor laser epitaxial structure comprises the following steps:

[0047] Step 1: First grow a first buffer layer on the substrate to provide appropriate lattice matching and stress relief. Subsequently, continue to grow a second buffer layer on the first buffer layer to further optimize the material quality between layers. On the second buffer layer, grow the first light-emitting unit, which includes a lower confinement layer, an active area, and an upper confinement layer. These three layers grow in sequence and form a complete light-emitting area. The light-emitting unit structure is a separately confined heterostructure, which can effectively limit the diffusion of carriers in the active area and improve the recombination efficiency, thereby ensuring the performance of the laser.

[0048] Step 2: Form a tunnel junction structure on the first light-emitting unit. The tunnel junction can effectively guide the flow of carriers through the PN junction characteristics and ensure the carrier transmission and activation between different active regions.

[0049] Step 3: Grow a new light-emitting unit on the tunnel junction structure. The light-emitting unit includes a lower confinement layer, an active region, and an upper confinement layer grown in sequence. The structure is the same as that of the previous light-emitting unit, ensuring that each light-emitting unit is a separately confined heterostructure. This step enables the laser to obtain higher gain and increase output power by cascading multiple light-emitting units.

[0050] Step 4: Repeat steps 2 and 3 to add more light-emitting units and tunnel junctions to the structure according to the design requirements.

[0051] Step 5: Grow a lower spacer layer on the last light-emitting unit. The main function of the lower spacer layer is to isolate different areas to avoid mutual influence between different areas, and it also helps the effective propagation of the light beam.

[0052] Step 6: Make a grating structure on the lower spacer layer. The grating structure uses a combination of indium gallium arsenic phosphide and indium phosphide materials to form a periodic arrangement structure in the light-emitting direction. In order to form the desired grating structure, holographic interference lithography, electron beam lithography, nanoimprinting or projection lithography can be used to transfer the designed grating pattern to the photoresist. Then, dry etching or wet etching is used to complete the production of the grating pattern.

[0053] Step 7: Continue to epitaxially grow an upper spacer layer on the grating structure. This layer is mainly used to further isolate the grating layer from the upper structure.

[0054] Step 8: Continue growing a regrown layer on the upper spacer layer to provide necessary electrical contact and thermal management functions.

[0055] Step 9: Grow a contact layer on the regrown layer.

[0056] The following is a detailed description of the epitaxial structure design of an InGaAsP multi-quantum well distributed feedback semiconductor laser with a wavelength of 1550nm. The laser adopts a multi-active region structure of tunnel junction cascade, which is suitable for general tunnel junction cascade multi-active region distributed feedback semiconductor lasers. By designing the structure of each layer, the gain of the device can be effectively improved and the output power can be optimized. The laser in this embodiment uses an InGaAsP material system and uses InP as the substrate material, which can achieve the required performance and functions.

[0057] Reference Figure 1 As shown in FIG. 1 , on a highly doped N-type indium phosphorus substrate 1 (thickness 3000nm, doping concentration 1×10 18 cm -3 ) is epitaxially grown from bottom to top as follows: the first N-type indium phosphorus buffer layer 2 (thickness 600nm, doping concentration 1×10 18 cm -3 ); a second N-type indium phosphorus buffer layer 3 (with a thickness of 400 nm and a doping concentration of 1×10 17 cm -3 );

[0058] The first light emitting unit 4 grown on the buffer layer 3 of the second layer, Figure 2 , from bottom to top: non-doped lattice-matched InGaAsP lower confinement layer 401 (thickness 35nm, light fluorescence wavelength 1100nm), non-doped lattice-matched InGaAsP lower waveguide layer 402 (thickness 35nm, light fluorescence wavelength 1200nm), InGaAsP active region multiple quantum well 403 (period number 8, quantum well thickness 7nm, 1% compressive strain, light fluorescence wavelength 1790nm, barrier thickness 9nm, 0.3% tensile strain, light fluorescence wavelength 1200nm ), a non-doped lattice-matched InGaAsP upper waveguide layer 404 (thickness 35nm, light fluorescence wavelength 1200nm), and a non-doped lattice-matched InGaAsP upper confinement layer 405 (thickness 35nm, light fluorescence wavelength 1100nm), constitute a complete light-emitting unit structure of a distributed feedback semiconductor laser; the cascade structure is connected through the first tunnel junction 5, which is composed of stacked heavily doped P-type InP and heavily doped N-type InP (thickness 20nm, doping concentration 2×10 19 cm -3); epitaxially grow a second light-emitting unit 6 on the first tunnel junction 5, which includes, from bottom to top: a non-doped lattice-matched InGaAsP lower confinement layer (thickness 35nm, light fluorescence wavelength 1100nm), a non-doped lattice-matched InGaAsP lower waveguide layer (thickness 35nm, light fluorescence wavelength 1200nm), an InGaAsP active region multiple quantum well (period number 8, quantum well thickness 7nm, 1% compressive strain, light fluorescence wavelength 1790nm, barrier thickness 9nm, 0.3% tensile strain, light fluorescence wavelength The cascade structure is connected through the second tunnel junction 7, which is composed of stacked heavily doped P-type Indium Phosphate and heavily doped N-type Indium Phosphate (with a thickness of 20 nm and a doping concentration of 2×10 19 cm -3 ); a third light-emitting unit 8 is epitaxially grown on the second tunnel junction 7, comprising, from bottom to top: a non-doped lattice-matched InGaAsP lower confinement layer (thickness 35nm, light fluorescence wavelength 1100nm), a non-doped lattice-matched InGaAsP lower waveguide layer (thickness 35nm, light fluorescence wavelength 1200nm), an InGaAsP active region multiple quantum well (number of periods is 8, quantum well thickness is 7nm, 1% compressive strain, light fluorescence wavelength is 1790nm, barrier thickness is 9nm, 0.3% tensile strain, light fluorescence wavelength is 1200nm), a non-doped lattice-matched InGaAsP upper waveguide layer (thickness 35nm, light fluorescence wavelength is 1200nm) and a non-doped lattice-matched InGaAsP upper confinement layer (thickness 35nm, light fluorescence wavelength is 1100nm), constituting a complete light-emitting unit structure of a distributed feedback semiconductor laser. The light emitting area of ​​the laser is formed by the above, which includes the first light emitting unit 4, the first tunnel junction 5, the second light emitting unit 6, the second tunnel junction 7 and the third light emitting unit 8 from bottom to top.

[0059] A P-type indium phosphorus lower spacer layer 901 (with a thickness of 115 nm and a doping concentration of 6×10 17 cm -3 );like Figure 3 As shown, based on the lower spacer layer 901 of P-type InGaAsP, a grating structure is further made on its surface. The grating pattern with a period of 244nm is transferred to the photoresist layer by holographic interference lithography. Then, the top of the lower spacer layer 901 is etched by reactive ion etching (RIE) technology to form a periodic grating groove with a thickness of 25nm. Then, the etched grating groove is filled with P-type InGaAsP material (doping concentration is 1×10 17 cm -3, the light fluorescence wavelength is 1250nm), forming a grating structure 902. Finally, a P-type indium phosphorus upper spacer layer 903 (thickness of 10nm, doping concentration of 1×10 18 cm -3 ) to cover and protect the grating structure. The grating layer 9 is manufactured by cleaning and treating the grating surface, removing the photoresist residue, and ensuring the quality of the grating surface to ensure the accuracy and performance of the grating structure.

[0060] On the P-type indium phosphorus upper spacer layer 903, a regrown layer 10 is continuously grown epitaxially. The regrown layer 10 is made of P-type indium phosphorus material (thickness of 400 nm, doping concentration of 1×10 18 cm -3 ) and P-type indium phosphorus material (thickness 800nm, doping concentration 1.5×10 18 cm -3 ). The regrown layer 10 has a greater thickness, and its functions include providing good electrical contact, improving thermal management and enhancing beam quality.

[0061] On the regrown layer 10, a contact layer 11 is epitaxially grown. The contact layer 11 is made of heavily doped P-type indium phosphorus material (thickness 10 nm, doping concentration 1×10 19 cm -3 ). The doping concentration of the P-type indium phosphorus contact layer 11 is relatively high to ensure good current transmission performance and low contact resistance.

[0062] In this embodiment, the cavity length of the tunnel junction cascade multi-active region distributed feedback semiconductor laser is 350 microns. The two end faces of the laser (i.e., cavity mirrors) are optically treated differently: one end is high reflection (HR) treated with a reflectivity of about 90%, which is used to form a stable resonance condition in the cavity; the other end is anti-reflection (AR) treated with a reflectivity of about 0.1%, which is used to minimize the loss of output light and ensure that the light can be efficiently coupled to the external optical system. The output light of the laser is effectively guided to the external optical system after being reflected by the front mirror of the anti-reflection end.

[0063] Regarding the design and setting of the ohmic contact electrode, the embodiment adopts two electrode structures, namely the top ohmic contact electrode 12 and the bottom ohmic contact electrode 0, and the setting method thereof is as follows:

[0064] The bottom ohmic contact electrode 0 is usually connected to the N-type indium phosphorus substrate 1 to provide a low resistance path. The electrode material can be a highly conductive metal such as gold (Au), silver (Ag) or aluminum (Al). In order to ensure good contact performance, it is first necessary to perform metallization on the surface of the N-type indium phosphorus substrate, and deposit a metal film on the surface of the substrate using sputtering or evaporation. Then, the metal film is processed into a predetermined shape by photolithography and etching techniques to form a bottom electrode contact area. Finally, the electrode is connected to the external circuit using metal welding or conductive glue.

[0065] The top ohmic contact electrode 12 is connected to the P-type indium phosphorus contact layer 11. In order to ensure uniform distribution of current, the top electrode design should try to avoid excessive contact resistance. The top electrode material usually uses materials such as gold, aluminum or molybdenum, which have good conductivity and chemical stability. First, the electrode material is deposited on the surface of the contact layer of the laser using evaporation or sputtering technology, and then the electrode shape is processed by photolithography and etching technology to ensure that the electrode geometry is compatible with the structure of the laser. The top electrode should be designed to be as thin as possible and large enough to reduce current density, improve uniformity, and reduce heat loss.

[0066] The tunnel junction cascade multi-active region distributed feedback semiconductor laser of the embodiment has multiple active regions grown in sequence in the epitaxial direction, and the multiple active regions are cascaded through tunnel junctions. This new distributed feedback semiconductor laser structure can greatly improve the slope efficiency, wherein the slope efficiency of the three-active region distributed feedback semiconductor laser with three light-emitting units is higher than 2.03W / A. Figure 4 This structure and the reasonable design of the grating layer can achieve a larger side mode suppression ratio, and as the number of active regions increases, it can maintain a single longitudinal mode output while having little effect on the wavelength shift. The main mode lasing wavelength of the three-active region distributed feedback semiconductor laser is 1551nm, as shown in Figure 5 shown.

[0067] The above description is only a preferred embodiment of the technical solution of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement or improvement (such as adjustment of the number of active areas, doping concentration, thickness of each layer, epitaxial material, etc.) made to the embodiment based on the technical essence without departing from the essential content of the technical solution of the present invention shall be deemed to be within the protection scope of the present invention.

Claims

1. A tunnel junction cascade multi-active region distributed feedback semiconductor laser, characterized in that: Its epitaxial structure includes, from bottom to top, a substrate, a buffer layer, a light-emitting region, a grating layer, a regrown layer and a contact layer; the light-emitting region includes at least two light-emitting units stacked up and down, wherein each light-emitting unit includes an active region and respectively confined heterostructure layers arranged on the upper and lower sides of the active region, tunnel junctions are arranged between adjacent light-emitting units, and are electrically connected through the tunnel junctions to form a cascade structure; the grating layer includes, from bottom to top, a lower spacer layer, a grating structure and an upper spacer layer; the upper spacer layer, the regrown layer and the contact layer are homogeneous materials, and the doping concentration of the upper spacer layer is ≤ the doping concentration of the regrown layer < the doping concentration of the contact layer.

2. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The tunnel junction is a reverse biased PN junction, comprising a P-type material layer and an N-type material layer, wherein the thickness of the P-type material layer is 8nm-13nm, and the thickness of the N-type material layer is 8nm-13nm.

3. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 2, characterized in that: The P-type material layer is heavily doped P-type indium phosphide or heavily doped P-type indium gallium arsenide, and the N-type material layer is heavily doped N-type indium phosphide.

4. The tunnel junction cascade multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The active region includes multiple quantum wells; the multiple quantum wells include quantum wells and potential barriers, the quantum wells are compressive strain quantum wells, and the potential barriers are tensile strain potential barriers; the number of periods of the multiple quantum wells is 5 to 9.

5. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The grating structure is composed of a combination of P-type lightly doped InGaAsP and P-type lightly doped InP to form a periodically arranged structure in the light emitting direction of the laser; the material of the lower spacer layer and the upper spacer layer is P-type lightly doped InP.

6. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The thickness of the upper spacer layer is 8 to 15 nm; the thickness of the regrown layer is 1000 to 1400 nm; the thickness of the contact layer is 8 to 15 nm; and the number of the light-emitting units is 2 to 5.

7. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The regrown layer includes at least two stacked doping concentration layers, and the doping concentration of the upper doping concentration layer is greater than the doping concentration of the lower doping concentration layer.

8. The tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 1, characterized in that: The substrate is an N-type indium phosphorus substrate, and the buffer layer is an N-type indium phosphorus buffer layer; the laser also includes a top ohmic contact electrode and a bottom ohmic contact electrode arranged at the upper and lower ends of the epitaxial structure.

9. A method for manufacturing a tunnel junction cascade multi-active region distributed feedback semiconductor laser according to any one of claims 1 to 8, characterized in that: include: Using an epitaxial growth process, a buffer layer and a light-emitting region are sequentially grown on a substrate, wherein the light-emitting region includes light-emitting units and tunnel junctions that are alternately grown; A grating layer is fabricated on the last light-emitting unit, wherein a grating structure is formed by an etching process; A regrown layer and a contact layer are sequentially grown on the grating layer.

10. The method for manufacturing a tunnel junction cascaded multi-active region distributed feedback semiconductor laser according to claim 9, characterized in that: The production of the grating layer includes: (1) growing a P-type indium phosphorus material on the last light-emitting unit to form a lower spacer layer; (2) etching the lower spacer layer to form periodic grating grooves; (3) filling the grating groove with a P-type indium gallium arsenic phosphide material to form a grating structure; (4) Grow another layer of P-type indium phosphorus material on the grating structure to form an upper spacer layer.

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