Tunnel junction cascaded multi-active region semiconductor laser and preparation method thereof

Abstract

This disclosure provides a method for fabricating a tunnel-cascaded multi-active-region semiconductor laser, comprising: growing a buffer layer on a substrate; growing a first light-emitting region on the buffer layer; growing a first reverse-biased PN structure on the first light-emitting region; growing a second light-emitting region on the first reverse-biased PN structure; growing a second reverse-biased PN structure on the second light-emitting region; growing a third light-emitting region on the second reverse-biased PN structure; and fabricating an ohmic contact layer on the third light-emitting region, and fabricating electrodes on the ohmic contact layer and the substrate surface, thereby completing the fabrication of the tunnel-cascaded multi-active-region semiconductor laser. This disclosure also provides a tunnel-cascaded multi-active-region semiconductor laser.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor laser technology, and in particular to a tunnel cascaded multi-active region semiconductor laser with high output power and low vertical divergence angle for lidar and its fabrication method. Background Technology

[0002] High-power semiconductor pulsed lasers, with their advantages of high reliability, small size, and low cost, have been widely used in a range of fields, including laser ranging, traffic monitoring, intelligent sensing, medical devices, surveying and remote sensing, and lidar. As a typical application of pulsed semiconductor lasers, lidar for autonomous vehicles has rapidly emerged in recent years, attracting widespread attention for its high detection accuracy, wide range, and fast 3D perception capabilities. As a key component of lidar, high-power pulsed semiconductor lasers emitting at 905nm have become the primary detection light source to meet Class 1 human eye safety standards. In practical applications, autonomous vehicles are required to accurately identify surrounding objects while moving at high speeds, constructing a 3D map with a detection accuracy of up to 2cm within a very short time, and creating high angular resolution images at distances up to 250m. This necessitates that lidar imaging and ranging systems have greater compactness and longer detection ranges, thus placing higher demands on the output power and beam quality of the lidar detection light source.

[0003] Compared to continuous or quasi-continuous semiconductor lasers, pulsed semiconductor lasers generate significantly less Joule heat due to their low duty cycle (as low as 0.1%). This substantial reduction in waste heat facilitates higher power output and allows for the design of more compact epitaxial structures, achieving maximum peak pulse power with minimal epitaxial material and reducing manufacturing costs. Traditional laser structures have only one emission region along the epitaxial direction within the same wafer. The limited emission area of ​​a single region can lead to catastrophic optical damage (COD) at high pulsed laser power outputs, causing device failure. To achieve even higher peak pulse power, multiple discrete devices must be vertically soldered, introducing additional soldering steps and consuming more epitaxial material. Another approach is to use a horizontal array of mini-bars, requiring beam shaping and combining to achieve higher peak pulse power. However, this also presents challenges due to complex manufacturing processes (due to the "smile effect") and the need for additional optical lenses, increasing costs unnecessarily.

[0004] Therefore, how to provide a laser with greater performance, process advantages, and cost advantages is a technical issue that urgently needs to be addressed. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the aforementioned issues, this disclosure provides a tunnel-cascaded multi-active-region semiconductor laser and its fabrication method, thereby alleviating the technical problems of complex laser processes and high costs in the prior art.

[0007] (II) Technical Solution

[0008] One aspect of this disclosure provides a method for fabricating a tunnel-cascaded multi-active-region semiconductor laser, comprising: growing a buffer layer on a substrate; growing a first light-emitting region on the buffer layer; growing a first reverse-biased PN structure on the first light-emitting region; growing a second light-emitting region on the first reverse-biased PN structure; growing a second reverse-biased PN structure on the second light-emitting region; growing a third light-emitting region on the second reverse-biased PN structure; and fabricating an ohmic contact layer on the third light-emitting region, and fabricating electrodes on the ohmic contact layer and the substrate surface, thereby completing the fabrication of the tunnel-cascaded multi-active-region semiconductor laser.

[0009] According to an embodiment of this disclosure, the substrate is an N-type offset substrate with a (100) plane offset from the (111) direction of 2° or 15°; the buffer layer is an N-type buffer layer.

[0010] According to an embodiment of this disclosure, growing a first light-emitting region on the buffer layer includes: sequentially growing an N-type lower confinement layer, an N-type lower waveguide layer, a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, and a first P-type inner waveguide layer on the buffer layer to form a first light-emitting region.

[0011] According to an embodiment of this disclosure, growing a first reverse-biased PN structure on the first light-emitting region includes: sequentially epitaxially growing a first P-type tunnel junction layer and a first N-type tunnel junction layer on the first light-emitting region to form a first reverse-biased PN structure.

[0012] According to an embodiment of this disclosure, growing a second light-emitting region on the first reverse-biased PN structure includes: sequentially epitaxially growing a first N-type inner waveguide layer, a third quantum barrier layer, a second quantum well layer, a fourth quantum barrier layer, and a second P-type inner waveguide layer on the first reverse-biased PN structure to form a second light-emitting region.

[0013] According to an embodiment of this disclosure, growing a second reverse-biased PN structure on the second light-emitting region includes: sequentially epitaxially growing a second P-type tunnel junction layer and a second N-type tunnel junction layer on the second light-emitting region to form a second reverse-biased PN structure.

[0014] According to an embodiment of this disclosure, growing a third light-emitting region on the second reverse-biased PN structure includes: sequentially epitaxially growing a second N-type inner waveguide layer, a fifth quantum barrier layer, a third quantum well layer, a sixth quantum barrier layer, a P-type upper waveguide layer, and a P-type upper confinement layer on the second reverse-biased PN structure to form the third light-emitting region.

[0015] According to the embodiments of this disclosure, the N-type lower confinement layer, the N-type lower waveguide layer, and the first P-type inner waveguide layer are all made of aluminum gallium arsenide, and the aluminum content in the N-type lower confinement layer is higher than that in the N-type lower waveguide layer and the first P-type inner waveguide layer; the first quantum barrier layer and the second quantum barrier layer are made of gallium arsenide, and the first quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

[0016] According to the embodiments of this disclosure, the first N-type inner waveguide layer and the second P-type inner waveguide layer are both made of aluminum gallium arsenide, and the aluminum composition in the first N-type inner waveguide layer and the second P-type inner waveguide layer is the same; the third quantum barrier layer and the fourth quantum barrier layer are made of gallium arsenide, and the second quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

[0017] According to the embodiments of this disclosure, the second N-type inner waveguide layer, the P-type upper waveguide layer, and the P-type upper confinement layer are all made of aluminum gallium arsenide, and the aluminum content in the P-type upper confinement layer is higher than that in the second N-type inner waveguide layer and the P-type upper waveguide layer; the fifth quantum barrier layer and the sixth quantum barrier layer are made of gallium arsenide, and the third quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

[0018] In another aspect, this disclosure provides a tunnel-cascaded multi-active-region semiconductor laser, fabricated using any of the methods described above. The tunnel-cascaded multi-active-region semiconductor laser comprises: a substrate; a buffer layer fabricated on the substrate; a first emitting region fabricated on the buffer layer, comprising: an N-type lower confinement layer fabricated on the buffer layer; an N-type lower waveguide layer fabricated on the N-type lower confinement layer; a first quantum barrier layer fabricated on the N-type lower waveguide layer; a first quantum well layer fabricated on the first quantum barrier layer; a second quantum barrier layer fabricated on the first quantum well layer; and a first P-type inner waveguide layer fabricated on the second quantum barrier layer; a first reverse-biased PN structure fabricated on the first emitting region, comprising: a first P-type tunnel junction layer fabricated on the first P-type inner waveguide layer; a first N-type tunnel junction layer fabricated on the first P-type tunnel junction layer; a second emitting region fabricated on the first reverse-biased PN structure, comprising: a first N-type inner waveguide layer fabricated on the first N-type tunnel junction layer; a third quantum... A third quantum barrier layer is fabricated on the second quantum well layer; a second quantum well layer is fabricated on the third quantum barrier layer; and a fourth quantum barrier layer is fabricated on the second quantum well layer; a second P-type inner waveguide layer is fabricated on the fourth quantum barrier layer; a second reverse-biased PN structure is fabricated on the second light-emitting region, comprising: a second P-type tunnel junction layer fabricated on the second P-type inner waveguide layer; a second N-type tunnel junction layer fabricated on the second P-type tunnel junction layer; and a third light-emitting region fabricated on the second reverse-biased PN structure, including: Includes: a second N-type inner waveguide layer, fabricated on the second N-type tunnel junction layer; a fifth quantum barrier layer, fabricated on the second N-type inner waveguide layer; a third quantum well layer, fabricated on the fifth quantum barrier layer; a sixth quantum barrier layer, fabricated on the third quantum well layer; a P-type upper waveguide layer, fabricated on the sixth quantum barrier layer; a P-type upper confinement layer, fabricated on the P-type upper waveguide layer; an ohmic contact layer, fabricated on the P-type upper confinement layer; a P-side electrode, fabricated on the ohmic contact layer; and an N-side electrode, fabricated on the substrate surface.

[0019] As can be seen from the above technical solution, the tunnel-cascaded multi-active-region semiconductor laser and its fabrication method disclosed herein have at least one or a portion of the following beneficial effects:

[0020] (1) In this structure, since there is only an inner waveguide layer and no inner confinement layer between the three active regions on the chip, the distance between the three light-emitting regions in the epitaxial direction is very close, and the super-large optical cavity formed by coupling can reach a size of 2.5 to 4.5 μm in the epitaxial direction; the expansion of the near-field optical field distribution effectively reduces the power density at the cavity surface, which is beneficial to improving the cavity surface damage threshold power, and ultimately enables high-power semiconductor lasers to operate at a larger power output level;

[0021] (2) The expansion of the near-field optical field distribution can effectively reduce the diffraction effect, which can greatly reduce the far-field vertical divergence angle, and the obtained high beam quality spot can be more easily coupled into the optical fiber. In addition, it is also beneficial for the subsequent focusing, collimation and shaping of the beam by the lidar;

[0022] (3) Compared with traditional semiconductor lasers, the efficiency can be increased by nearly 3 times for the number of active regions;

[0023] (4) Since the multi-active-region structure is integrated on-chip, it only requires one epitaxy. However, the traditional stacked array connects the two active regions through electrodes, which not only introduces additional fabrication processes, but also generates additional heat due to contact resistance, thus increasing the heat dissipation burden of the device;

[0024] (5) Due to the reduced spacing between the three active regions, the thickness of the epitaxial material of the entire device can be significantly reduced, the series resistance of the device can be reduced, and the power consumption level of the lidar can be reduced.

[0025] (6) Simultaneous lasing of different wavelengths between multiple active regions can be achieved on a single chip, which is expected to be applied to some special occasions. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the fabrication method of a tunnel-cascaded multi-active-region semiconductor laser according to an embodiment of this disclosure;

[0027] Figure 2 This is a schematic diagram of the structure of a tunnel-cascaded multi-active-region semiconductor laser according to an embodiment of the present disclosure;

[0028] Figure 3 This is a far-field distribution diagram of a tunnel-cascaded multi-active-region semiconductor laser according to an embodiment of this disclosure;

[0029] Figure 4 This is a diagram showing the near-field light and refractive index distribution of the epitaxial material along the growth direction of the tunnel-cascaded multi-active region semiconductor laser according to an embodiment of this disclosure.

[0030] Figure 5 This is a PI curve diagram of a tunnel-cascaded multi-active-region semiconductor laser according to an embodiment of this disclosure.

[0031] [Explanation of key component symbols in the accompanying drawings of this disclosure embodiment]

[0032] 1-N-type gallium arsenide substrate; 2-N-type gallium arsenide buffer layer; 3-N-type aluminum gallium arsenide lower confinement layer; 4-N-type aluminum gallium arsenide lower waveguide layer; 5-gallium arsenide quantum barrier layer; 6-indium gallium arsenide quantum well; 7-gallium arsenide quantum barrier layer; 8-P-type aluminum gallium arsenide inner waveguide layer; 9-P-type gallium arsenide layer; 10-N-type gallium arsenide layer; 11-N-type aluminum gallium arsenide inner waveguide layer; 12-gallium arsenide quantum barrier layer; 13-indium gallium arsenide quantum well; 14-gallium arsenide quantum barrier layer; 15-P-type aluminum gallium arsenide inner waveguide layer; 16-P-type gallium arsenide layer; 17-N-type gallium arsenide layer; 18-N-type aluminum gallium arsenide inner waveguide layer; 19-gallium arsenide quantum barrier layer; 20-indium gallium arsenide quantum well; 21-gallium arsenide quantum barrier layer; 22-P-type aluminum gallium arsenide upper waveguide layer; 23-P-type aluminum gallium arsenide upper confinement layer; 24-P-type gallium arsenide ohmic contact layer. Detailed Implementation

[0033] This disclosure provides a tunnel-cascaded multi-active-region semiconductor laser and its fabrication method. Multiple active regions are sequentially grown along the epitaxial direction and connected by reverse-direction PN junctions. This novel tunnel-cascaded multi-active-region structure significantly improves the device's slope efficiency. Furthermore, because there is no internal confinement layer between the multiple active regions, their close proximity allows for coupling to form a large optical cavity, reducing optical power density, increasing output power, and greatly decreasing the vertical divergence angle.

[0034] Semiconductor lasers operating in pulsed mode do not require much concern about waste heat from the device. Therefore, tunnel-cascaded multi-active-region lasers can better solve the technical problems existing in traditional lasers compared to traditional semiconductor laser structures.

[0035] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0036] In this embodiment of the disclosure, a method for fabricating a tunnel-cascaded multi-active-region semiconductor laser is provided, combined with Figure 1 and Figure 2 The preparation method includes:

[0037] Operation S1: Grow a buffer layer on the substrate;

[0038] Operation S2: Grow a first light-emitting region on the buffer layer;

[0039] Operation S3: Grow a first reverse-biased PN structure on the first light-emitting region;

[0040] Operation S4: Grow a second light-emitting region on the first reverse-biased PN structure;

[0041] Operation S5: Grow a second reverse-biased PN structure on the second light-emitting region;

[0042] Operation S6: Growing a third light-emitting region on the second reverse-biased PN structure; and

[0043] Operation S7: An ohmic contact layer is fabricated on the third light-emitting region, and electrodes are fabricated on the ohmic contact layer and the substrate surface, thereby completing the fabrication of the tunnel cascaded multi-active region semiconductor laser.

[0044] In operation S1 above, the substrate is an N-type gallium arsenide substrate, more specifically, the N-type gallium arsenide substrate is an N-type gallium arsenide substrate with an offset of 2° or 15° from the (111) direction on the (100) plane. The buffer layer is an N-type gallium arsenide buffer layer; more specifically, in operation S1: an N-type gallium arsenide substrate with an offset of 2° or 15° from the (111) direction on the (100) plane is selected, and an N-type gallium arsenide buffer layer 2 is epitaxially grown on the selected N-type gallium arsenide substrate 1 using metal-organic chemical vapor deposition. Selecting a substrate with an offset angle can suppress the formation of metastable ordered structures during the growth process, and the gallium arsenide buffer layer is used to improve the growth quality of subsequent epitaxial layers.

[0045] In operation S2 above, an N-type lower confinement layer, an N-type lower waveguide layer, a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, and a first P-type inner waveguide layer are sequentially grown on the buffer layer to form a first light-emitting region. More specifically, the N-type lower confinement layer, the N-type lower waveguide layer, and the first P-type inner waveguide layer are all made of aluminum gallium arsenide, and the aluminum content in the N-type lower confinement layer is higher than that in the N-type lower waveguide layer and the first P-type inner waveguide layer, to form separate confinement heterostructures, such as... Figure 2 As shown, an N-type aluminum gallium arsenide (AGaAs) lower confinement layer 3, an N-type AGaAs lower waveguide layer 4, a gallium arsenide (GaAs) quantum barrier layer 5, an indium gallium arsenide (InGaAs) quantum well (active layer) 6, a gallium arsenide (GaAs) quantum barrier layer 7, and a P-type AGaAs inner waveguide layer 8 are epitaxially grown sequentially on an N-type gallium arsenide (GaAs) buffer layer 2. The first and second quantum barrier layers are made of gallium arsenide, and the first quantum well layer is made of Indium gallium arsenide, forming a compressive strain quantum well structure. Figure 2 As shown. Quantum barrier layers 5 and 7 are made of gallium arsenide, and quantum well (active layer) 6 is made of indium gallium arsenide.

[0046] In the above operation S3, a first P-type tunnel junction layer and a first N-type tunnel junction layer are epitaxially grown sequentially on the first luminescent region to form a first reverse-biased PN structure. More specifically, combined with... Figure 2 As shown, a P-type gallium arsenide layer 9 and an N-type gallium arsenide layer 10 are epitaxially grown sequentially on the P-type aluminum gallium arsenide inner waveguide layer 8. Both the P-type gallium arsenide layer 9 and the N-type gallium arsenide layer 10 are highly doped layers, used to form an effective tunnel junction under reverse bias, greatly increasing the probability of carrier tunneling through the reverse-biased PN junction while bearing a relatively small bias voltage. It should be noted that increasing the doping concentration of the tunnel junction is beneficial for obtaining a large tunneling probability, but excessively high doping concentration will cause unnecessary free carrier absorption, leading to optical absorption loss.

[0047] In operation S4 above, a first N-type inner waveguide layer, a third quantum barrier layer, a second quantum well layer, a fourth quantum barrier layer, and a second P-type inner waveguide layer are sequentially epitaxially grown on the first reverse-biased PN structure to form the second light-emitting region. More specifically, the first N-type inner waveguide layer and the second P-type inner waveguide layer are both made of aluminum gallium arsenide, and the aluminum composition in the first N-type inner waveguide layer and the second P-type inner waveguide layer is the same; the third quantum barrier layer and the fourth quantum barrier layer are made of gallium arsenide, and the second quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure. Figure 2 As shown, an N-type aluminum gallium arsenide inner waveguide layer 11, a gallium arsenide quantum barrier layer 12, an indium gallium arsenide quantum well (active layer) 13, a gallium arsenide quantum barrier layer 14, and a P-type aluminum gallium arsenide inner waveguide layer 15 are epitaxially grown on an N-type gallium arsenide layer 10.

[0048] Among them, the N-type aluminum gallium arsenide inner waveguide layer 11 and the P-type aluminum gallium arsenide inner waveguide layer 15 are both made of aluminum gallium arsenide material, and the aluminum composition in the N-type aluminum gallium arsenide inner waveguide layer 11 and the P-type aluminum gallium arsenide inner waveguide layer 15 is the same, which is used for optical field coupling; the quantum barrier layers 12 and 14 are made of gallium arsenide material, and the quantum well (active layer) 13 is made of indium gallium arsenide material, forming a compressive strain quantum well structure.

[0049] In operation S5 above, a second P-type tunnel junction layer and a second N-type tunnel junction layer are sequentially epitaxially grown on the second luminescent region to form a second reverse-biased PN structure. More specifically, combined with Figure 2 As shown, a P-type gallium arsenide layer 16 and an N-type gallium arsenide layer 17 are epitaxially grown sequentially on a P-type aluminum gallium arsenide inner waveguide layer 15. Both the P-type gallium arsenide layer 16 and the N-type gallium arsenide layer 17 are highly doped layers used to form an effective tunnel junction under reverse bias.

[0050] In operation S6 above, a second N-type inner waveguide layer, a fifth quantum barrier layer, a third quantum well layer, a sixth quantum barrier layer, a P-type upper waveguide layer, and a P-type upper confinement layer are epitaxially grown sequentially on the second reverse-biased PN structure to form the third light-emitting region. The second N-type inner waveguide layer, the P-type upper waveguide layer, and the P-type upper confinement layer are all made of aluminum gallium arsenide (AlGaAs), and the aluminum content in the P-type upper confinement layer is higher than that in the second N-type inner waveguide layer and the P-type upper waveguide layer. The fifth and sixth quantum barrier layers are made of gallium arsenide (GaAs), and the third quantum well layer is made of indium gallium arsenide (InGaAs), forming a compressive strain quantum well structure. More specifically, combined with... Figure 2As shown, an N-type aluminum gallium arsenide (AGaAs) inner waveguide layer 18, a gallium arsenide (GaAs) quantum barrier layer 19, an indium gallium arsenide (InGaAs) quantum well (active layer) 20, a GaAs quantum barrier layer 21, a P-type AGaAs upper waveguide layer 22, and a P-type AGaAs upper confinement layer 23 are epitaxially grown on an N-type gallium arsenide (GaAs) layer 17. The N-type AGaAs inner waveguide layer 17, the P-type AGaAs upper waveguide layer 22, and the P-type AGaAs upper confinement layer 23 are all made of aluminum gallium arsenide (AGaAs) material, and the aluminum content in the P-type AGaAs upper confinement layer 23 is higher than that in the N-type AGaAs inner waveguide layer 17 and the P-type AGaAs upper waveguide layer 22, respectively, to form confinement heterostructures. The quantum barrier layers 19 and 21 are made of gallium arsenide (GaAs), and the quantum well (active layer) 20 is made of Indium gallium arsenide (InGaAs), forming a compressive strain quantum well structure.

[0051] In the above operation S7, an ohmic contact layer is formed on the third light-emitting region, combined with... Figure 2 As shown, a P-type gallium arsenide ohmic contact layer 24 is epitaxially grown on a P-type aluminum gallium arsenide (AlGaAs) confinement layer 23. The P-type gallium arsenide ohmic contact layer 24 is a heavily doped layer. Its purpose is to achieve good ohmic contact, reduce series resistance, and improve the conversion efficiency of the device. Further, a strip structure with a wide surface contact is first photolithographically etched on the epitaxial chip, a silicon dioxide electrically insulating film is deposited, and then a wide surface contact region is etched on the electrically insulating film. On the gallium arsenide ohmic contact layer 24, a wide mesa electrode contact region with a width of about 200 μm is etched by photolithography, wherein the etching depth extends below the active region 6 to better confine current propagation, reduce the threshold current, and improve the conversion efficiency of the device. A second electrode overlay is performed, etching away the silicon dioxide film in the wide mesa region to expose the gallium arsenide ohmic contact layer 24 so that the current injection region can be defined in subsequent processes. The above operation S7 includes the preparation of the P-side electrode and the preparation of the N-side electrode after grinding, polishing, thinning, and polishing the N-side substrate. The P-side electrode, made of titanium-platinum, is fabricated on a wide mesa electrode contact layer to facilitate the routing of electrode leads. The N-type gallium arsenide substrate 1 is then thinned to approximately 130 μm by grinding and polishing, followed by further polishing. The N-side electrode is then fabricated beneath the N-type gallium arsenide substrate 1. The N-side electrode is made of gold-germanium-nickel to form a good ohmic contact with the substrate, reducing contact resistance and facilitating the routing of electrode leads.

[0052] This disclosure also provides a tunnel-cascaded multi-active-region semiconductor laser, fabricated using any of the above-described methods, wherein the tunnel-cascaded multi-active-region semiconductor laser comprises:

[0053] A substrate; a buffer layer fabricated on the substrate; a first light-emitting region fabricated on the buffer layer, comprising: an N-type lower confinement layer fabricated on the buffer layer; an N-type lower waveguide layer fabricated on the N-type lower confinement layer; a first quantum barrier layer fabricated on the N-type lower waveguide layer; a first quantum well layer fabricated on the first quantum barrier layer; a second quantum barrier layer fabricated on the first quantum well layer; and a first P-type inner waveguide layer fabricated on the second quantum barrier layer; a first reverse-biased PN structure fabricated on the first light-emitting region, comprising: a first P-type tunnel junction layer fabricated on the first P-type inner waveguide layer; a first N-type tunnel junction layer fabricated on the first P-type tunnel junction layer; a second light-emitting region fabricated on the first reverse-biased PN structure, comprising: a first N-type inner waveguide layer fabricated on the first N-type tunnel junction layer; a third quantum barrier layer fabricated on the first N-type inner waveguide layer; and a second quantum well layer fabricated on the third quantum barrier layer. The second light-emitting region comprises: a fourth quantum barrier layer fabricated on the second quantum well layer; a second P-type inner waveguide layer fabricated on the fourth quantum barrier layer; a second reverse-biased PN structure fabricated on the second light-emitting region, comprising: a second P-type tunnel junction layer fabricated on the second P-type inner waveguide layer; a second N-type tunnel junction layer fabricated on the second P-type tunnel junction layer; a third light-emitting region fabricated on the second reverse-biased PN structure, comprising: a second N-type inner waveguide layer fabricated on the second N-type tunnel junction layer; a fifth quantum barrier layer fabricated on the second N-type inner waveguide layer; a third quantum well layer fabricated on the fifth quantum barrier layer; a sixth quantum barrier layer fabricated on the third quantum well layer; a P-type upper waveguide layer fabricated on the sixth quantum barrier layer; a P-type upper confinement layer fabricated on the P-type upper waveguide layer; an ohmic contact layer fabricated on the P-type upper confinement layer; a P-side electrode fabricated on the ohmic contact layer; and an N-side electrode fabricated on the substrate surface.

[0054] The N-type lower confinement layer is made of N-type aluminum gallium arsenide material with an aluminum content of 0.5% and a thickness of 1.5-1.9 μm. The lower N-type lower waveguide layer is also made of N-type aluminum gallium arsenide material with an aluminum content of 0.45% and a thickness of 0.4-0.6 μm.

[0055] Among them, the first quantum well layer, the second quantum well layer, and the third quantum well layer are single quantum well structures made of indium gallium arsenide.

[0056] Among them, the first P-type inner waveguide layer and the second P-type inner waveguide layer are made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm.

[0057] Among them, the first N-type inner waveguide layer and the second N-type inner waveguide layer are N-type aluminum gallium arsenide materials with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm.

[0058] Among them, the first P-type tunnel junction layer and the second P-type tunnel junction layer are made of P-type gallium arsenide material with a thickness of 10-20 nm.

[0059] Among them, the first N-type tunnel junction layer and the second N-type tunnel junction layer are N-type gallium arsenide materials with a thickness of 10-20 nm.

[0060] The P-type upper waveguide layer is made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.4-0.6 μm.

[0061] The P-type upper confinement layer is made of P-type aluminum gallium arsenide material with an aluminum content of 0.5 and a thickness of 0.6-0.8 μm.

[0062] The semiconductor laser disclosed herein has multiple active regions sequentially grown along the epitaxial direction, and these active regions are interconnected by reverse-biased PN junctions. For example... Figure 5 As shown, this novel tunnel-cascaded multi-active-region laser can greatly improve slope efficiency. The slope efficiency of the three-active-region laser is higher than 3.5W / A, and it can achieve a peak power output of 220W under pulse conditions of 150ns and 10KHz.

[0063] Figure 4 This diagram illustrates the near-field light distribution and refractive index distribution of the epitaxial material along the growth direction of a tunnel-cascaded multi-active-region semiconductor laser according to an embodiment of this disclosure. The dashed line diagram represents the near-field light distribution of the laser along the epitaxial material direction, with the dashed vertical axis pointing to the left (as indicated by the circled arrow). The solid line diagram represents the refractive index distribution of the epitaxial material, with the solid vertical axis pointing to the right (as indicated by the circled arrow). Figure 4 As shown, this structure, with only an inner waveguide layer and no inner confinement layer between the three active regions on the wafer, results in very close proximity between the three emitting regions in the epitaxial direction. The resulting ultra-large optical cavity can achieve a size of 2.5–4.5 μm in the epitaxial direction. This significantly reduces the optical power density at the cavity surface, improving the cavity surface damage threshold power and allowing high-power semiconductor lasers to operate at a higher power output level. Furthermore, the expanded near-field optical distribution effectively reduces diffraction effects, thereby greatly reducing the vertical divergence angle and making it easier to couple a high-beam-quality spot into an optical fiber. Additionally, it facilitates subsequent beam focusing, collimation, and shaping by the lidar.

[0064] like Figure 3 As shown in the simulation, the tunnel-cascaded three-active-region semiconductor laser can achieve a divergence angle of 4.98°*15.3° (e.g., Figure 3 As shown, θ / / θ is the horizontal divergence angle. ⊥ (Vertical divergence angle).

[0065] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the various elements and methods described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0066] Based on the above description, those skilled in the art should have a clear understanding of the tunnel-cascaded multi-active-region semiconductor laser and its fabrication method disclosed herein.

[0067] In summary, this disclosure provides a tunnel-cascaded multi-active-region semiconductor laser and its fabrication method. Multiple active regions are sequentially grown along the epitaxial direction and connected by reverse-direction PN junctions. This novel tunnel-cascaded multi-active-region structure significantly improves the device's slope efficiency. Furthermore, because there is no internal confinement layer between the multiple active regions, their close proximity allows for coupling to form a large optical cavity, reducing optical power density, increasing output power, and significantly decreasing the vertical divergence angle. This structure can improve the laser's output power and slope efficiency, reduce the device's vertical divergence angle and series resistance, which is beneficial for improving the accuracy of lidar and reducing its power consumption. The number of emitting regions in the epitaxial structure can be adjusted between 2 and 4 as needed. The fabricated wide-strip laser reduces optical power density, increases output power and slope efficiency, and significantly reduces the vertical divergence angle.

[0068] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure. Furthermore, the shapes and dimensions of the components in the drawings do not reflect actual size and proportion, but are only schematic representations of the embodiments of this disclosure.

[0069] The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify the corresponding elements does not imply that the element has any ordinal number, nor does it represent the order of one element with another element, or the order of manufacturing methods. The use of these ordinal numbers is only to enable a named element to be clearly distinguished from another element with the same name.

[0070] Furthermore, unless specifically described or required to occur in a specific order, the order of the above steps is not limited to those listed above and can be varied or rearranged according to the desired design. Moreover, the above embodiments can be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments.

[0071] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for fabricating a tunnel-cascaded multi-active-region semiconductor laser, comprising: A buffer layer is grown on the substrate; An N-type lower confinement layer, an N-type lower waveguide layer, a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, and a first P-type inner waveguide layer are sequentially grown on the buffer layer to form a first light-emitting region. A first P-type tunnel junction layer and a first N-type tunnel junction layer are grown on the first light-emitting region to form a first reverse-biased PN structure; A first N-type inner waveguide layer, a third quantum barrier layer, a second quantum well layer, a fourth quantum barrier layer, and a second P-type inner waveguide layer are sequentially grown on the first anti-biased PN structure to form a second light-emitting region. A second P-type tunnel junction layer and a second N-type tunnel junction layer are grown on the second light-emitting region to form a second reverse-biased PN structure; A second N-type inner waveguide layer, a fifth quantum barrier layer, a third quantum well layer, a sixth quantum barrier layer, a P-type upper waveguide layer, and a P-type upper confinement layer are sequentially grown on the second reverse-biased PN structure to form the third light-emitting region; as well as An ohmic contact layer is fabricated on the third light-emitting region, and electrodes are fabricated on the ohmic contact layer and the substrate surface, thereby completing the fabrication of a tunnel cascaded multi-active region semiconductor laser. The fabricated semiconductor laser can achieve a peak power output of 220W under pulse conditions of 150ns and 10KHz. Among them, the N-type lower confinement layer is made of N-type aluminum gallium arsenide material with an aluminum composition of 0.5 and a thickness of 1.5-1.9 μm; the N-type lower waveguide layer is made of N-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.4-0.6 μm; the first P-type inner waveguide layer and the second P-type inner waveguide layer are made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm; the first N-type inner waveguide layer and the second N-type inner waveguide layer are made of N-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm; the first P... The first and second N-type tunnel junctions are made of P-type gallium arsenide material with a thickness of 10-20 nm; the first and second N-type tunnel junctions are made of N-type gallium arsenide material with a thickness of 10-20 nm; the P-type upper waveguide layer is made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.4-0.6 μm; the P-type upper confinement layer is made of P-type aluminum gallium arsenide material with an aluminum composition of 0.5 and a thickness of 0.6-0.8 μm.

2. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein the substrate is an N-type substrate with an offset angle of 2° or 15° in the (100) plane offset from the (111) direction; and the buffer layer is an N-type buffer layer.

3. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein a first reverse-biased PN structure is grown on the first emitting region, comprising: A first P-type tunnel junction layer and a first N-type tunnel junction layer are epitaxially grown sequentially on the first luminescent region to form a first reverse-biased PN structure.

4. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein a second reverse-biased PN structure is grown on the second emitting region, comprising: A second P-type tunnel junction layer and a second N-type tunnel junction layer are epitaxially grown sequentially on the second luminescent region to form a second reverse-biased PN structure.

5. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein: The first and second quantum barrier layers are made of gallium arsenide, and the first quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

6. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein: The third and fourth quantum barrier layers are made of gallium arsenide, and the second quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

7. The method for fabricating a tunnel-cascaded multi-active-region semiconductor laser according to claim 1, wherein: The fifth and sixth quantum barrier layers are made of gallium arsenide, and the third quantum well layer is made of indium gallium arsenide, forming a compressive strain quantum well structure.

8. A tunnel-cascaded multi-active-region semiconductor laser, fabricated using the method described in any one of claims 1-7, wherein the tunnel-cascaded multi-active-region semiconductor laser can achieve a peak power output of 220W under pulse conditions of 150ns and 10kHz, the laser comprising: Substrate; A buffer layer, which is fabricated on the substrate; The first light-emitting region, formed on the buffer layer, includes: The N-type lower confinement layer is fabricated on the buffer layer; The N-type lower waveguide layer is fabricated on the N-type lower confinement layer; The first quantum barrier layer is fabricated on the N-type lower waveguide layer; The first quantum well layer is fabricated on the first quantum barrier layer; The second quantum barrier layer is fabricated on the first quantum well layer; and The first P-type inner waveguide layer is fabricated on the second quantum barrier layer; The first reverse-biased PN structure is fabricated on the first light-emitting region, comprising: The first P-type tunnel junction is fabricated on the first P-type inner waveguide layer; The first N-type tunnel layer is fabricated on the first P-type tunnel layer; The second light-emitting region, fabricated on the first reverse-biased PN structure, includes: The first N-type inner waveguide layer is fabricated on the first N-type tunnel junction layer; The third quantum barrier layer is fabricated on the first N-type inner waveguide layer; The second quantum well layer is fabricated on top of the third quantum barrier layer; and The fourth quantum barrier layer is fabricated on the second quantum well layer; The second P-type inner waveguide layer is fabricated on the fourth quantum barrier layer; The second reverse-biased PN structure is fabricated on the second light-emitting region, comprising: The second P-type tunnel junction is fabricated on the second P-type inner waveguide layer; The second type N tunnel layer is fabricated on the second type P tunnel layer; The third light-emitting region, fabricated on the second reverse-biased PN structure, includes: The second type N inner waveguide layer is fabricated on the second type N tunnel junction layer; The fifth quantum barrier layer is fabricated on the second N-type inner waveguide layer; The third quantum well layer is fabricated on the fifth quantum barrier layer; The sixth quantum barrier layer is fabricated on the third quantum well layer; A P-type upper waveguide layer, fabricated on the sixth quantum barrier layer; and The P-type upper confinement layer is fabricated on the P-type upper waveguide layer; An ohmic contact layer is fabricated on the P-type upper confinement layer; The P-side electrode is fabricated on the ohmic contact layer; and N-face electrodes are fabricated on the substrate surface; Among them, the N-type lower confinement layer is made of N-type aluminum gallium arsenide material with an aluminum composition of 0.5 and a thickness of 1.5-1.9 μm; the N-type lower waveguide layer is made of N-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.4-0.6 μm; the first P-type inner waveguide layer and the second P-type inner waveguide layer are made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm; the first N-type inner waveguide layer and the second N-type inner waveguide layer are made of N-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.5-0.9 μm; the first P... The first and second N-type tunnel junctions are made of P-type gallium arsenide material with a thickness of 10-20 nm; the first and second N-type tunnel junctions are made of N-type gallium arsenide material with a thickness of 10-20 nm; the P-type upper waveguide layer is made of P-type aluminum gallium arsenide material with an aluminum composition of 0.45 and a thickness of 0.4-0.6 μm; the P-type upper confinement layer is made of P-type aluminum gallium arsenide material with an aluminum composition of 0.5 and a thickness of 0.6-0.8 μm.

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