A laser and a method of manufacturing the same

Abstract

A laser and a preparation method thereof are provided. The laser comprises: an epitaxial stack having a ridge waveguide arranged along a second direction, a first structure arranged on a front cavity surface and having a contact surface with the ridge waveguide, and a second structure arranged on both sides of the ridge waveguide along a third direction and having a height higher than or equal to a height of an active layer in the ridge waveguide along a first direction. The first structure arranged near the front cavity surface of the laser can enhance the heat dissipation capacity of the front cavity surface. The thinner second structure can make the upper electrode closer to the active layer, and better rely on the metal layer with higher thermal conductivity for heat dissipation, so that the thermal conductivity of the laser is greatly improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor chip technology, and in particular to a laser and a method for fabricating the same. Background Technology

[0002] The active region of a laser suffers from heat accumulation. To improve thermal conductivity, a deeply etched Fe-doped structure is typically used. However, existing structures have the following drawbacks: 1) Fe-doped structures are not completely insulating, resulting in leakage current; 2) Thicker structures require higher epitaxial growth quality. Poor growth can lead to reliability issues and reduced yield.

[0003] There is an urgent need to provide a laser that can effectively dissipate heat from the active region while avoiding leakage current and improving device reliability. Summary of the Invention

[0004] The purpose of this application is to provide a laser and a method for fabricating the same. The laser and method provided in this application form a first structure and a second structure, which can effectively dissipate heat from the active region while avoiding leakage current and improving device reliability.

[0005] This application provides a laser, comprising:

[0006] Substrate;

[0007] Epitaxial layers are sequentially stacked on the substrate along a first direction;

[0008] A ridge waveguide is formed in the epitaxial stack and extends along a second direction, which is the light emission direction of the laser.

[0009] The first structure is disposed on the front cavity surface of the laser and has a contact surface with the ridge waveguide;

[0010] The second structure is disposed on both sides of the ridge waveguide in a third direction, and the top surface of the second structure is higher than or equal to the top surface of the active layer in the ridge waveguide in the first direction. The third direction is perpendicular to the first direction and the second direction, respectively.

[0011] In one embodiment, the second structure has a plurality of cross-sections perpendicular to the first direction, and the area of ​​the cross-section containing the top surface of the second structure is smaller than the area of ​​the cross-section containing the bottom surface of the second structure.

[0012] In one embodiment, along the first direction, the area of ​​the cross section containing the bottom surface of the second structure gradually decreases to the area of ​​the cross section containing the top surface of the second structure.

[0013] In one embodiment, within the plane formed by the first direction and the third direction, the length of the bottom edge of the second structure is greater than the length of the top edge of the second structure.

[0014] In one embodiment, the top surface of the second structure is higher than the top surface of the active layer in the ridge waveguide in the first direction. In the plane formed by the first direction and the third direction, the region of the second structure above the active layer is a narrowing region, and the second structure located in the narrowing region is a quasi-insulating structure.

[0015] In one embodiment, the active layer has a length of A in the third direction, and the second structure located on one side of the ridge waveguide has a length of C in the third direction, where C / A > 5.

[0016] In one embodiment, within the plane formed by the second direction and the third direction, the base area of ​​the first structure is M, the base area of ​​the second structure is N, and 0.0025≤M / N≤0.06.

[0017] In one embodiment, the thickness of the first structure in the first direction is 1.5 to 3 times the thickness of the second structure in the first direction.

[0018] In one embodiment, the length of the first structure in the second direction is B, and the length of the active layer in the third direction is A.

[0019] In one embodiment, the top surface of the first structure is higher than the top surface of the active layer in the first direction;

[0020] And / or, the first structure includes a curved surface; the curved surface is disposed at the light-emitting position of the front cavity surface.

[0021] In one embodiment, the laser further includes:

[0022] An insulating layer, disposed along the first direction on the second structure, and covering a portion of the epitaxial stack; and,

[0023] The upper electrode is disposed on the insulating layer along the first direction and covers the remaining portion of the epitaxial stack.

[0024] In one embodiment, the laser has a first etched surface and a second etched surface, the first etched surface having a third angle between itself and the surface formed by the first direction and the second direction, wherein 0° < the third angle < 90°; and / or, the second etched surface having a fourth angle between itself and the surface formed by the first direction and the second direction, wherein 0° < the fourth angle < 90°.

[0025] ​This application also provides a method for fabricating a laser, including:

[0026] S1, an epitaxial stack is stacked on the substrate along a first direction, and a ridge waveguide region is defined on the epitaxial stack, wherein the extension direction of the ridge waveguide region is a second direction from the front cavity surface of the laser to the rear cavity surface;

[0027] S2, non-waveguide regions are formed on both sides of the ridge waveguide region in the third direction; the third direction is perpendicular to the first direction and the second direction, respectively.

[0028] S3 defines the cavity surface gap region through photolithography and forms the cavity surface region through etching.

[0029] S4, a protective layer is fabricated above the ridge waveguide region;

[0030] S5, perform selective growth to form a first structure in the cavity surface gap region and a second structure in the non-waveguide region;

[0031] S6, remove the protective layer and form an insulating layer on the second structure and a portion of the ridge waveguide region; and form an upper electrode on the insulating layer and on at least a portion of the ridge waveguide region not covered by the insulating layer.

[0032] In one embodiment, the selective growth step includes:

[0033] The growth temperature is 600℃-650℃, and the molar flow ratio of the group V element source gas to the group III element source gas introduced into the reaction chamber is greater than 50.

[0034] In one embodiment, the thickness of the first structure in the first direction is 1.5 to 3 times the thickness of the second structure in the first direction.

[0035] In one embodiment, the method further includes etching along an etch line to form a single laser.

[0036] Wherein, in the plane formed by the second direction and the third direction, the etched line is set at a first angle with the extension direction of the ridge waveguide, where 0° < the first angle ≤ 30°;

[0037] And / or, the angle between the etched surface formed after etching along the etch line and the plane formed by the first direction and the second direction is the second angle, where 0° < the second angle ≤ 45°.

[0038] This application has at least the following advantages or beneficial effects:

[0039] In this embodiment of the laser, a thinner second structure located on both sides of the ridge waveguide in the third direction laterally covers the active layer. Specifically, in the first direction, the height of the top surface of the second structure is higher than or equal to the height of the top surface of the active layer, allowing for good conduction of heat accumulation in the active layer. Furthermore, the thinner second structure brings the upper electrode closer to the active layer, enabling the laser to better utilize the metal layer of the upper electrode, which has higher thermal conductivity, for heat dissipation. Therefore, the laser provided in this application has a better heat dissipation channel, significantly improving thermal conductivity.

[0040] In this embodiment, a first structure is epitaxially grown on the lower cladding layer near the front cavity surface of the laser. The first structure can be made of iron-doped indium phosphide. Adding this first structure near the front cavity surface of the laser has at least the following beneficial effects:

[0041] (1) It can enhance the heat dissipation capability of the front cavity facet (FF) and reduce cavity surface loss. Due to the high optical field density, the laser near the FF region of the front cavity facet suffers from severe heat accumulation. Filling the first structure can significantly improve the heat dissipation capability of the cavity surface. In the prior art, a non-injection region is generally set near the cavity surface, i.e., no current is applied, thereby reducing the heat generation of the cavity surface. However, this part will generate additional absorption loss for light. The laser provided in the embodiment of this application fills the area near the front cavity facet with iron-doped indium phosphide material as the first structure. This material has low light absorption loss. Therefore, compared with the laser structure of the prior art, it can improve the heat dissipation capability of the cavity surface without introducing additional loss and improve the output optical power.

[0042] (2) Improve the optical damage threshold of the cavity surface. The first structure is filled in the region near the front cavity surface of the laser as a transition region between the laser gain medium and the cavity surface film. This can buffer the emitted light field of the laser cavity surface, thereby protecting the cavity surface and improving the optical damage threshold of the cavity surface.

[0043] (3) Make the light spot on the end face more uniform. The vertical divergence angle of the laser in the prior art is larger than that in the horizontal direction. In the embodiment of this application, after the laser near the front cavity surface area is filled with the first structure, since the refractive index of the filling layer in the first direction and the third direction are the same, the difference between the divergence angle in the first direction and the third direction can be suppressed, thereby making the output light spot distribution more uniform.

[0044] (4) Protecting the ridge waveguide. After the first structure is filled in the area near the front cavity surface of the laser, it can provide some support for the ridge waveguide, reduce the stress on the ridge waveguide, and thus improve the reliability of the device. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 A perspective view of the laser provided in the embodiments of this application;

[0047] Figure 2 A cross-sectional schematic diagram of a laser provided in an embodiment of this application;

[0048] Figure 3 This is a partial cross-sectional schematic diagram of a laser provided in one embodiment of this application;

[0049] Figure 4 A partial cross-sectional schematic diagram of a laser provided in another embodiment of this application;

[0050] Figure 5 This is a top view and / or side view of a laser provided in one embodiment of this application;

[0051] Figure 6 This is a top view and / or side view of a laser provided in another embodiment of this application;

[0052] Figure 7 Top view of two lasers provided in an embodiment of this application;

[0053] Figure 8 A schematic diagram showing the included angles between the two etched surfaces of the laser provided in this application embodiment and the surfaces formed by the first and second directions;

[0054] Figure 9 A top view of two lasers provided in an embodiment of this application, illustrating an etched line;

[0055] Figure 10 This is a top view of a laser array provided in one embodiment of the present application, illustrating the cleavage lines and etching lines referenced during the formation of a single laser;

[0056] Figure 11 A top view of a laser array provided for another embodiment of this application, illustrating the cleavage lines and etch lines referenced during the formation of a single laser;

[0057] Figure 12 This is a top view of a laser array provided in another embodiment of the present application, illustrating the cleavage lines and etch lines referenced during the etching process to form a single laser.

[0058] Icon Description

[0059] Laser 100: Substrate 10, epitaxial stack 20, lower cladding 21, active layer 22, upper cladding 23, ridge waveguide 30, first structure 40, second structure 50, insulating layer 60, quasi-insulating structure 61, lower electrode 71, upper electrode 72, front cavity surface FF, rear cavity surface RF. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0061] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0062] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0063] Please see Figure 1 and Figure 2This application provides a laser 100. The laser 100 is a semiconductor laser, such as an edge-emitting laser (EEL), a Fabry-Perot laser (FP), a quantum well laser (QW), a quantum dot laser (QD), or a quantum cascade laser (QCL). The laser 100 includes a substrate 10 and an epitaxial stack 20 stacked along a first direction. The epitaxial stack 20 includes a lower cladding layer 21, an active layer 22, and an upper cladding layer 23 sequentially disposed along the first direction. The epitaxial stack 20 has a ridge waveguide 30 disposed along a second direction. The ridge waveguide 30 extends along the second direction and is formed by surface etching of the upper cladding layer 23, used for lateral light confinement and mode selection. The active layer 22 is typically a quantum well structure and is the region where electron-hole recombination generates photons. The lower cladding layer 21 and the upper cladding layer 23 form a symmetrical double heterojunction, confining carriers and the optical field within the active region. The width of the ridge waveguide 30 can be set to 2μm-10μm, and the depth is etched only to the upper cladding 23 (without damaging the active layer 22). The effective refractive index difference between the ridge waveguide 30 and the second structure 50 in the space on both sides forms lateral (parallel to the substrate) light confinement. In some embodiments, the epitaxial stack 20 includes a buffer layer (not shown), a lower cladding 21, a lower waveguide layer (not shown), an active layer 22, an upper waveguide layer (not shown), and an upper cladding 23 arranged sequentially along a first direction.

[0064] Preferably, such as Figure 1 As shown, the side of the ridge waveguide 30 that contacts the second structure 50 includes a curved surface, which on the one hand increases the contact area between the two to improve the heat conduction efficiency of the laser 100, and on the other hand further reduces the contact stress between the second structure 50 and the ridge waveguide 30.

[0065] like Figure 2 As shown, the frontmost point of the laser 100 in the light-emitting direction is the front facet (FF), and the rearmost point in the light-emitting direction is the rear facet (RF). A first structure 40 is positioned close to the front facet FF and has a contact surface with the ridge waveguide 30. The first structure 40 is disposed on the surface of the lower cladding 21 in the first direction. A second structure 50 is disposed on both sides of the ridge waveguide 30 in the third direction, and the height of the second structure 50 in the first direction is higher than or equal to the height of the active layer 22 in the ridge waveguide 30. Figure 3 As shown, in the first direction, the height of the second structure 50 is equal to the height of the active layer 22 in the ridge waveguide 30. Figure 4 As shown, in the first direction, the height of the second structure 50 is higher than the height of the active layer 22 in the ridge waveguide 30.

[0066] The insulating layer 60 covers the second structure 50 and also partially covers the top surface of the ridge waveguide 30. The top of the exposed area of ​​the ridge mesa serves as a current injection window. When current is injected through the top electrode, the insulating layer 60 blocks the lateral diffusion of current, forcing charge carriers to be injected vertically into the active layer 22, improving injection efficiency and reducing the threshold current. The lower electrode 71 is disposed below the substrate 10, and the upper electrode 72 is disposed above the insulating layer 60 and the ridge waveguide 30 exposed outside the insulating layer 60. The upper electrode 72 can be a Ti layer and / or an Au layer. The lower electrode 71 can be any one or more layers of Ge, Au, Ni, or Au. The first direction is the stacking direction of the epitaxial stack 20, which is also the fast axis direction of the laser 100. The second direction is the extension direction of the ridge waveguide 30, and the third direction is the slow axis direction of the laser 100. The third direction is perpendicular to the first and second directions, respectively.

[0067] During the fabrication of the laser 100, the first structure 40 and the second structure 50 can be formed simultaneously through secondary epitaxial growth. The first structure 40 and the second structure 50 can be made of iron-doped indium phosphide material.

[0068] In this embodiment, in the provided laser 100 structure, the second structure 50 (thinner) located on both sides of the ridge waveguide 30 in the third direction laterally covers the active layer 22 (in the first direction, the height of the top surface of the second structure 50 is higher than or equal to the height of the top surface of the active layer 22), allowing for good conduction of heat accumulation in the active layer 22. Furthermore, the thinner second structure 50 brings the upper electrode 72 (thicker gold layer) closer to the active layer 22, allowing the laser 100 to better rely on the metal layer of the upper electrode 72, which has higher thermal conductivity, for heat dissipation. Therefore, the laser 100 provided in this application has a better heat dissipation channel, and its thermal conductivity is greatly improved.

[0069] In this embodiment, as Figure 2The diagram shows the structure of the laser 100 closer to the light-emitting side (excluding the upper electrode 71). Near the front cavity surface FF of the laser 100, a first structure 40 is grown on the lower cladding 21 via secondary epitaxy. The first structure 40 can be made of iron-doped indium phosphide (InP:Fe). Adding the first structure 40 near the front cavity surface FF of the laser 100 has at least the following beneficial effects: (1) It can enhance the heat dissipation capacity of the front cavity surface FF and reduce cavity surface loss. Due to the high light field density, the laser near the front cavity surface FF experiences severe heat accumulation. Filling the area with the first structure 40 (InP:Fe) can significantly improve the heat dissipation capacity of the cavity surface. In the prior art, a non-injection region is generally set near the cavity surface, i.e., no current is applied, thereby reducing the heat generation of the cavity surface. However, this part will generate additional absorption loss for light. The laser 100 provided in this embodiment fills the area near the front cavity surface FF with iron-doped indium phosphide material as the first structure 40. This material has low light absorption loss. Therefore, compared with the laser structure of the prior art, it can improve the heat dissipation capacity of the cavity surface without introducing additional loss and improve the output optical power. (2) Improve the optical damage threshold of the cavity surface. The first structure 40 (InP:Fe) is filled in the area near the front cavity surface FF of the laser 100 as the transition area between the laser gain medium and the cavity surface film layer. It can buffer the output light field of the laser cavity surface, thereby protecting the cavity surface and improving the optical damage threshold of the cavity surface. (3) Make the light spot of the end face more uniform. The vertical divergence angle of the laser in the prior art is larger than that in the horizontal direction. After the laser 100 near the front cavity surface FF is filled with the first structure 40 (InP:Fe) in this embodiment, since the refractive index of the first direction and the third direction of the filling layer are the same, the difference between the divergence angle of the first direction and the third direction can be suppressed, thereby making the output light spot distribution more uniform. (4) Protecting the ridge waveguide 30. After the laser 100 is filled with the first structure 40 (InP:Fe) in the FF region near the front cavity surface, it can provide a certain support for the ridge waveguide 30, reduce the stress on the ridge waveguide 30, and thus improve the reliability of the device.

[0070] In one embodiment, the second structure 50 has multiple cross-sections perpendicular to the first direction, and the area of ​​the cross-section containing the top surface of the second structure 50 is smaller than the area of ​​the cross-section containing the bottom surface of the second structure 50.

[0071] In this embodiment, the area of ​​other cross-sections of the second structure 50 between the top and bottom cross-sections can vary, and the variation can take many forms. For example, the area of ​​other cross-sections of the second structure 50 between the top and bottom cross-sections can vary in a stepped manner. The area of ​​the top cross-section and its vicinity is the smallest, the area of ​​the bottom cross-section and its vicinity is the largest, and the area of ​​the middle cross-section and its vicinity is in the middle.

[0072] In one embodiment, along the first direction, the area of ​​the cross section containing the bottom surface of the second structure 50 gradually decreases to the area of ​​the cross section containing the top surface of the second structure 50.

[0073] In this embodiment, along the first direction, the cross-sectional area of ​​the second structure 50 gradually decreases. This facilitates secondary epitaxial growth together with the first structure 40, and also facilitates the formation of an insulating-like structure 61 that suppresses current leakage through the upper cladding 23 (the specific structure of the insulating-like structure 61 can be found in [reference]). Figure 4 and Figure 8 ).

[0074] In one embodiment, during the generation of the first structure 40 and the second structure 50, due to the gap area between the end faces of adjacent lasers 100 (e.g., Figure 7 The area of ​​the first structure 40 shown is greater than the area on both sides of the ridge waveguide 30 (e.g., Figure 7 The area of ​​the second structure 50 (as shown) is smaller, and the growth rate of the first structure 40 is faster. Therefore, the thickness of the first structure 40 is greater than the thickness of the second structure 50 on both sides of the ridge waveguide 30. This enhances the heat dissipation capability of the front cavity surface (FF) and makes the light spot emitted to the FF more uniform. Furthermore, since the gap area between adjacent laser 100 end faces is smaller than the area on both sides of the ridge waveguide 30, the first structure 40 and the second structure 50 can still be distinguished even in the same growth process and under the same process parameters. Specifically, in the same secondary epitaxial growth process and under the same process parameters, because the gap area between adjacent laser 100 end faces is smaller than the area on both sides of the ridge waveguide 30, the thickness of the first structure 40 between adjacent laser end faces is greater than the thickness of the second structure 50 on both sides of the ridge waveguide 30. The thicker first structure 40 enhances the heat dissipation capability of the front cavity surface (FF) and makes the light spot emitted to the FF more uniform.

[0075] In one embodiment, within the plane formed by the first direction and the third direction, the length of the bottom edge of the second structure 50 is greater than the length of the top edge of the second structure 50. In a cross-sectional view obtained along a plane parallel to the first direction and the third direction, as shown... Figure 3 and Figure 4 As shown, the cross-sectional view of the second structure 50 can be trapezoidal. In some other embodiments, the cross-sectional view of the second structure 50 can be a series of steps. Alternatively, in some other embodiments, in the cross-sectional view of the second structure 50, the length of the bottom edge gradually decreases from the top edge to the bottom edge.

[0076] In this embodiment, the second structure 50 is formed through secondary epitaxial growth, and the length of the bottom edge of the second structure 50 is greater than the length of the top edge, exhibiting a shape that is wider at the bottom and narrower at the top. Within the plane formed by the first direction and the third direction, the length of the bottom edge of the second structure 50 is greater than the length of the top edge. Therefore, within the cross-section formed by the second direction and the third direction, the area of ​​the multiple cross-sections of the second structure 50 from bottom to top in the first direction gradually decreases. During the secondary epitaxial growth process, if the area to be grown is larger, the gas consumption rate is faster, and the concentration is lower, the insulation is worse; conversely, if the area to be grown is smaller, the gas consumption rate is slower, and the concentration is higher, the insulation is better. Therefore, the area of ​​the multiple cross-sections of the second structure 50 from bottom to top in the first direction gradually decreases, the gas consumption rate becomes slower, the concentration becomes higher, and the insulation becomes better, with the cross-section of the top-layer second structure 50 exhibiting the best insulation.

[0077] In one embodiment, the height of the second structure 50 in the first direction is higher than the height of the active layer 22 in the ridge waveguide 30. In the plane formed by the first direction and the third direction, the region of the second structure 50 above the active layer 22 is a narrowing region, and the second structure 50 located in the narrowing region is an insulating-like structure 61.

[0078] In this embodiment, the second structure 50 is wider at the bottom and narrower at the top, and the region of the second structure 50 above the active layer 22 is a narrowing region. The second structure 50 located in the narrowing region has the best insulation performance and the best effect in restricting the current flow path, preventing current through the upper cladding layer 23 from entering the second structure 50, approximately forming an insulating-like structure 61 on the top of the second structure 50. Specifically, as shown... Figure 4 As shown, the narrowed region of the second structure 50 is located above the horizontal plane (the plane formed by the second direction and the third direction) of the upper top surface of the active layer 22, forming a quasi-insulating structure 61. The laser 100 provided in this embodiment forms a quasi-insulating structure 61, which suppresses leakage current paths that might occur through the upper cladding 23 in conventional laser structures. The quasi-insulating structure 61 achieves insulation, thus reducing the operating current of the laser 100 involved in this application. The thinner second structure 50 reduces the difficulty of secondary epitaxy, lowering costs and improving epitaxial yield. In this embodiment, the characteristics of the second structure 50 are adjusted by changing the structural shape of the laser 100 while keeping the process parameters unchanged.

[0079] In one embodiment, the height by which the top surface of the second structure 50 is higher than the top surface of the active layer 22 in the first direction is 0 μm - 2 μm. In one embodiment, the height by which the top surface of the second structure 50 is higher than the top surface of the active layer 22 in the first direction is 100 nm to 2 μm. For example, the height by which the top surface of the second structure 50 is higher than the top surface of the active layer 22 in the first direction is 200 nm, 350 nm, 420 nm, 560 nm, 740 nm, 860 nm, 900 nm. In this embodiment, the thinner second structure 50 reduces the difficulty of secondary epitaxy, can reduce costs, and improve the epitaxy yield.

[0080] In this embodiment, the top surface of the second structure 50 is at least flush with the top surface of the active layer 22, and the heat accumulation of the active layer 22 in the ridge waveguide 30 can be well conducted. At the same time, with thick gold as the upper electrode 72, the upper electrode 72 is closer to the active region, and the laser 100 can also rely better on the metal layer with higher thermal conductivity for heat dissipation. Therefore, the laser 100 involved in this embodiment has a better heat dissipation channel and the thermal conductivity is improved.

[0081] In one embodiment, as Figure 1 shown, the length of the active layer 22 in the third direction is A, and the length of the second structure 50 on one side of the ridge waveguide 30 in the third direction is C, and C / A > 5. In the laser 100, the narrower the ridge waveguide 30 / active layer 22, the worse the heat dissipation effect. In this embodiment, by setting the length C of the second structure 50 in the third direction according to the length A of the active layer 22 in the third direction (or the length of the ridge waveguide 30 in the third direction), the heat dissipation effect can be improved. The length of the first structure 40 in the second direction is B, the length of the first structure 40 in the third direction is D, and the length of the second structure 50 in the second direction is E. In one embodiment, C / B > 10 is used to limit the length of the first structure 40 in the second direction of the front cavity surface FF, facilitating heat dissipation of the front cavity surface FF. In one embodiment, 1000 μm < E < 4000 μm, and in one embodiment, 5 μm < A < 15 μm. In one embodiment, the length of the first structure 40 in the second direction is B, the length of the active layer 22 in the third direction is A, and 1 < B / A ≤ 2. In this embodiment, the spot emitted by the laser is homogenized, and the spot homogenization effect is good.

[0082] In one embodiment, within the plane formed by the second and third directions, the bottom area of ​​the first structure 40 is M, and the bottom area of ​​the second structure 50 located on one side of the ridge waveguide 30 is N, where 0.0025 ≤ M / N ≤ 0.06. In a specific embodiment, M / N is 0.005; in another specific embodiment, M / N is 0.013; in yet another specific embodiment, M / N is 0.025; in a specific embodiment, M / N is 0.038; in a specific embodiment, M / N is 0.042; and in yet another specific embodiment, M / N is 0.055.

[0083] In this embodiment, the fabrication process of the first structure 40 and the second structure 50 can involve simultaneously depositing target structures of different thicknesses on both sides of the front cavity surface FF and the ridge waveguide 30. The first structure 40 and the second structure 50 have different bottom areas, and are designed according to the aforementioned special M / N ratio to facilitate simultaneous secondary epitaxial growth.

[0084] In one embodiment, the thickness of the first structure 40 in the first direction is 1.5 to 3 times the thickness of the second structure 50 in the first direction. In a specific embodiment, the thickness of the first structure 40 in the first direction is 1.8 times the thickness of the second structure 50 in the first direction. In another specific embodiment, the thickness of the first structure 40 in the first direction is 2.6 times the thickness of the second structure 50 in the first direction. In this embodiment, the thickness of the first structure 40 in the first direction is 1.5 to 3 times the thickness of the second structure 50. On the one hand, the thicker first structure 40 can enhance the heat dissipation capacity of the front cavity surface FF. On the other hand, the thinner second structure 50 allows the upper electrode to be closer to the active layer 22, making better use of the metal layer with higher thermal conductivity for heat dissipation, thus greatly improving the thermal conductivity of the laser 100.

[0085] In one embodiment, the top surface of the first structure 40 is higher than the top surface of the active layer in the first direction. And / or, the first structure 40 includes a curved surface. The curved surface is disposed at the light-emitting position of the front cavity surface FF. The curved surface may include a convex curved surface or a concave curved surface. The surface of the first structure 40 closer to the front cavity surface FF may also be a plane, such as a concave plane or a convex plane.

[0086] In this embodiment, the surface of the first structure 40 closer to the front cavity surface FF has a special structure, which can achieve spot reshaping while increasing heat dissipation. Specifically, if the surface of the first structure 40 closer to the front cavity surface FF is convex, it can achieve a focusing effect and reduce the spot size; if the surface of the first structure 40 closer to the front cavity surface FF is concave, it can achieve a uniform spot size.

[0087] like Figure 5 The diagram can represent Figure 1 The top view formed by looking down from the top of the ridge waveguide 30. Figure 5 It can also represent Figure 1 A side view formed by looking from both sides of the ridge waveguide 30 in the third direction towards the middle. Figure 5 It can also both represent Figure 1 A top view formed by looking down from the top surface of the ridge waveguide 30, and also represent Figure 1 A side view formed by looking from both sides of the ridge waveguide 30 in the third direction towards the middle.

[0088] As described above, if Figure 5 It only represents the top view, then the effect of the first structure 40 is to adjust the light spot in the horizontal direction; if Figure 5 It only represents the side view, then the effect of the first structure 40 is to adjust the light spot in the vertical direction; if Figure 5 It both represents the top view and the side view, then the first structure 40 is similar to a spherical surface, and the effect is to control the complete light spot emitted from the front cavity surface FF. In this embodiment, setting the first structure 40 on the front cavity surface FF can increase heat dissipation, and setting a special concave or convex surface structure on the front cavity surface FF can achieve light spot processing (specifically: the convex surface can focus and reduce the light spot; the concave surface can homogenize the light spot).

[0089] In one embodiment, the length of the first structure 40 near the front cavity surface FF in the third direction is greater than the length of the first structure 40 in other parts in the third direction. For example, the length of the first structure 40 near the front cavity surface FF in the third direction is greater than the length of the first structure 40 near the rear cavity surface RF in the third direction. In this embodiment, while not affecting the overall heat dissipation of the laser 100, the heat dissipation of the front cavity surface FF is improved.

[0090] In one embodiment, it further includes: an insulating layer 60 and an upper electrode 72. The insulating layer 60 is disposed on the second structure 50 along the first direction and covers a part of the epitaxial stack 20. The upper electrode 72 is disposed on the insulating layer 60 along the first direction and covers the remaining part of the epitaxial stack 20.

[0091] In this embodiment, the material of the insulating layer 60 can be selected as silicon oxide, silicon nitride or other materials. The thickness of the insulating layer 60 is H, and 50nm < H < 100nm can be set. A thick gold layer is deposited on the top of the insulating layer 60 as the upper electrode 72. The material of the upper electrode 72 can be selected as gold, and the thickness of the upper electrode 72 can be selected as 3 micrometers - 5 micrometers. In this embodiment, the insulating layer 60 has insulating properties, and the upper electrode 72 is closer to the active layer 22, improving the heat dissipation efficiency.

[0092] Please refer to Figure 8A schematic diagram of the angles between two etched surfaces of a laser and the surfaces formed by a first direction and a second direction is provided. The laser 100 has a top surface, a bottom surface, a front cavity surface FF, a rear cavity surface RF, a first etched surface, and a second etched surface. In some embodiments of this application, the top and bottom surfaces are parallel, the front cavity surface FF and the rear cavity surface RF are parallel, and the first and second etched surfaces are not parallel. A third angle, 0° < third angle < 90°, is formed between the first etched surface and the surfaces formed by the first and second directions. And / or, a fourth angle, 0° < fourth angle < 90°, is formed between the second etched surface and the surfaces formed by the first and second directions.

[0093] In this embodiment, the etched surfaces in contact with the second structure 50 are the first etched surface and the second etched surface. The angle between the two etched surfaces and the surfaces formed by the first and second directions is between 0° and 90°, meaning the area of ​​the second structure 50 gradually decreases, and the second structure 50 is generally wider at the bottom and narrower at the top. Within the cross-sections formed by the second and third directions, the areas of the multiple cross-sections of the second structure 50 from bottom to top in the first direction decrease progressively. The second structure 50 can be formed through secondary epitaxial growth. During the secondary epitaxial growth process, if the area to be grown is larger, the gas consumption rate is faster, and the concentration is lower, the insulation is worse; conversely, if the area to be grown is smaller, the gas consumption rate is slower, and the concentration is higher, the insulation is better. Therefore, the areas of the multiple cross-sections of the second structure 50 from bottom to top in the first direction decrease progressively, the gas consumption rate decreases progressively, the concentration increases progressively, and the insulation becomes better and better. The cross-section of the second structure 50 located at the top layer has the best insulation.

[0094] This application also provides a method for fabricating a laser, including:

[0095] S1, an epitaxial stack 20 is stacked on the substrate 10 along a first direction, and a ridge waveguide region is defined on the epitaxial stack 20 by photolithography. The extension direction of the ridge waveguide region is a second direction from the front cavity surface FF of the laser 100 to the rear cavity surface RF.

[0096] S2, through wet etching, forms the target space on both sides of the third-direction upward ridge waveguide region. The third direction is perpendicular to the first and second directions, respectively.

[0097] S3. The cavity surface gap region is defined by photolithography and formed by dry etching. In this step, the purpose of dry etching is to make the etched edge perpendicular to the cavity surface, so that the laser can be emitted perpendicular to the cavity surface without refraction loss caused by additional angle.

[0098] S4. A protective layer is fabricated above the ridge waveguide region. The protective layer is typically an insulating layer.

[0099] S5, selective growth is performed using MOCVD to form a first structure 40 in the cavity surface gap region and a second structure 50 in the ridge waveguide region. In this step, iron-doped indium phosphide is used to cover the ridge waveguide region and the cavity surface gap region. At the same time, the overall growth rate is controlled by temperature regulation, so that the thickness of the first structure 40 grown in the cavity surface gap region of the laser 100 is 1.5 to 3 times the thickness of the second structure 50 grown in the ridge waveguide region. The cavity surface gap region can be completely covered by the second epitaxially grown first structure 40, while the ridge waveguide regions on both sides of the ridge waveguide 30 can be covered by the second epitaxially grown second structure 50 up to the upper cladding 23.

[0100] S6, remove the protective layer and form an insulating layer 60 in the second structure 50 and a portion of the ridge waveguide region. An upper electrode 72 is formed on the insulating layer 60 and on at least a portion of the ridge waveguide region not covered by the insulating layer 60.

[0101] In this embodiment, a method for fabricating a laser is provided. This method can simultaneously form a first structure 40 and a second structure 50. During the formation of the first structure 40 and the second structure 50, since the gap area between the laser 100 and the laser 100 end face is smaller than the area on both sides of the ridge waveguide 30, the growth rate of the two target structures (InP:Fe) is faster. Therefore, the thickness of the first structure 40 is thicker than the thickness of the second structure 50 on both sides of the ridge waveguide 30. This feature can enhance the heat dissipation capability of the front cavity surface FF and make the light spot emitted to the front cavity surface FF more uniform. Figure 7 The image shows a top view of the laser 100 before etching (the laser 100 is arranged in an array, and only two lasers 100 are shown in the image). The laser 100 is filled with InP:Fe on both sides and between the end faces of the ridge waveguide 30 structure.

[0102] In one embodiment, the selective growth step using MOCVD includes: a growth temperature of 600℃-650℃, and a molar flow rate ratio of group V source gas to group III source gas introduced into the reaction chamber greater than 50.

[0103] In this embodiment, MOCVD (Metal-Organic Chemical Vapor Deposition) is used to achieve secondary epitaxial growth of the first structure 40 and the second structure 50. Specifically, a Group III source gas can be a metal-organic compound (such as TMGa, TMAl), and a Group V source gas can be a hydride (such as AsH3, PH3, NH3). The target structure formed using the growth temperature and gas ratio relationship involved in this embodiment has better heat dissipation and better spot uniformity.

[0104] In one embodiment, the thickness of the first structure 40 in the first direction is 1.5 to 3 times the thickness of the second structure 50 in the first direction.

[0105] In this embodiment, selective growth is performed using MOCVD to cover the regions on both sides of the ridge waveguide 30 (forming the second structure 50) and the cavity surface gap region (forming the first structure 40) with iron-doped indium phosphide material. At the same time, the overall growth rate is controlled by temperature regulation. Finally, the secondary epitaxial thickness between the device end faces is 1.5 to 3 times the thickness on both sides of the ridge. The cavity surface can be completely covered by the secondary epitaxial layer, while the secondary epitaxial layer on both sides of the ridge covers the upper cladding.

[0106] In one embodiment, the method for fabricating the laser further includes etching the area to be etched and cleaving along cleavage lines to form a single laser 100.

[0107] Wherein, within the plane formed by the second direction and the third direction, the etch boundary line of the area to be etched is set at a first angle with the extension direction of the ridge waveguide, 0° < first angle ≤ 30°; and / or, the etched surface formed after etching the area to be etched is at a second angle with the plane formed by the first direction and the second direction, 0° < second angle ≤ 45°.

[0108] The etching boundary line described in this application is the boundary line of the second structure 50 after the area to be etched is etched.

[0109] In this embodiment, the size of the first angle defines the difference between the front cavity surface FF and the rear cavity surface RF (length along the second direction, or, the area of ​​both). This step defines, as follows: Figure 2 In the top view shown (within the plane formed by the second and third directions), the length of the front cavity surface FF of the laser 100 in the third direction is greater than the length of the rear cavity surface RF in the third direction. That is, the area of ​​the actual laser 100 near the front cavity surface FF is larger than the area near the rear cavity surface RF, which helps to improve heat dissipation and reduce heat accumulation near the front cavity surface FF.

[0110] In this embodiment, a second angle is defined during etching to limit the length of the bottom edge of the second structure 50 to be greater than the length of its top edge within the plane formed by the first and third directions. The bottom edge of the second structure 50 is the edge closest to the lower electrode 71. In this step, setting the second angle from 0° to 45° can form... Figure 3 or Figure 4 The trapezoidal or stepped second structure 50 shown narrows from the bottom to the top. In the laser 100, the area of ​​the second structure 50 decreases along the first direction (fast axis direction). The smaller the area, the slower the gas consumption rate during the fabrication process, the higher the gas concentration, and the better the insulation. This restricts the current flow path and prevents the current passing through the upper cladding from entering the second structure 50 on both sides of the ridge waveguide 30.

[0111] In this embodiment, the structural shape of the second structure 50 on both sides of the ridge waveguide 30 can be changed by adjusting the size of the first angle and the second angle, that is, the characteristics of the second structure 50 can be adjusted without changing the process parameters.

[0112] In one embodiment, the laser fabrication method further includes: structuring the first structure 40 so that the first structure 40 is closer to the surface of the front cavity surface FF. Figure 5 The convex surface shown or as Figure 6 The concave surface is shown above. Its technical effect is as described above.

[0113] Please see Figure 9 It indicates two lasers, 100, according to Figure 9 Etching the etching lines shown in the figure will form a laser 100 structure in which the length of the first structure 40 near the front cavity surface FF along the third direction is greater than the length of the first structure 40 along the third direction in other regions.

[0114] In one embodiment, the line width of the etched line along a third direction is not less than 10 μm.

[0115] Please see Figure 10 and Figure 11 , Figure 10 This is a top view of a laser array provided in one embodiment of the present application, illustrating the cleavage lines and etching lines referenced during the formation of the laser 100. Figure 11 This is a top view of a laser array provided for another embodiment of this application, illustrating the cleavage lines and etching lines referenced during the formation of the laser 100. A laser array includes: a plurality of lasers 100, a plurality of first-type cleavage lines, and a plurality of second-type etching lines.

[0116] Multiple first-type cleavage lines are located between adjacent lasers 100 on arbitrary cavity surfaces. The first-type cleavage lines are perpendicular to the plane formed by the second and third directions.

[0117] Multiple second-type etching lines include second-type first-side etching lines and second-type second-side etching lines. Multiple second-type first-side etching lines and second-type second-side etching lines define the area to be etched; the second-type first-side etching lines are used to form a first etched surface after etching, and the second-type second-side etching lines are used to form a second etched surface after etching. Any laser's second-type first-side etching lines and second-type second-side etching lines intersect at a point, or an extension of a second-type first-side etching line intersects with an extension of a second-type second-side etching line. The first etched surface has a third angle with the surface formed by the first direction and the second direction, where 0° < third angle < 90°. And / or, the second etched surface has a fourth angle with the surface formed by the first direction and the second direction, where 0° < fourth angle < 90°. The first direction is the bottom-up stacking direction, and the second direction is the laser's light emission direction. The third direction is perpendicular to both the first and second directions.

[0118] This embodiment provides reference cleavage lines and etching lines when a laser array is formed into multiple lasers 100. During the etching process, it can be done according to... Figure 10 or Figure 11 The etched lines shown are etched, and during the cleavage process, they can be etched according to... Figure 10 or Figure 11 The cleavage lines shown are used for cleavage. Specifically, Figure 10 and Figure 11 The laser array shown can also be rotated 90 degrees. Figure 10 and Figure 11 The process sequence of the cleavage lines and etching lines shown can be varied. For example, cleavage can be performed first using the first type of cleavage lines, followed by etching using the second type of first-side etching lines and the second type of second-side etching lines. Alternatively, etching can be performed first using the second type of first-side etching lines and the second type of second-side etching lines, followed by cleavage using the first type of cleavage lines. Furthermore, since the multiple lasers 100 can be arranged in different ways, the cleavage lines and etching lines can also be designed in other ways.

[0119] Similarly, please see Figure 12 , Figure 12 This is a top view of a laser array provided in one embodiment of this application, illustrating the cleavage lines and etching lines referenced during the etching process. A laser array includes: a plurality of lasers 100 to be etched, a plurality of first-type cleavage lines, and a plurality of second-type etching lines. The second-type etching lines described in this application are the boundary lines of a second structure 50 (which will be formed upon completion of etching of the area to be etched), or can be understood as the boundary lines of the area to be etched.

[0120] It is important to understand that during the formation of laser 100, the front cavity surface (FF) and rear cavity surface (RF) of the laser can be treated interchangeably. After a single laser 100 is formed, an antireflection coating is deposited on one end of the laser 100 cavity surface; this end is the front cavity surface (FF). A high-reflection coating is deposited on the other end of the laser 100 cavity surface; this end is the rear cavity surface (RF). Based on... Figure 12 The first and second type of etching lines are used to etch the laser array to improve etching efficiency and reduce costs.

[0121] In one embodiment, a single laser 100 is formed by etching the laser array based on etch lines using gaseous chemical reagents and / or physical bombardment processes to provide higher resolution, better anisotropy and controllability, while reducing environmental pollution and process complexity, thereby improving the yield of the laser 100.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A laser, characterized in that, include: Substrate; The epitaxial stack includes a lower cladding layer, an active layer, and an upper cladding layer sequentially stacked on the substrate along a first direction; A ridge waveguide is formed in the epitaxial stack and extends along a second direction, which is the light emission direction of the laser. The first structure is disposed on the front cavity surface of the laser and has a contact surface with the ridge waveguide; The second structure is disposed on both sides of the ridge waveguide in a third direction, and the top surface of the second structure is higher than or equal to the top surface of the active layer in the ridge waveguide in the first direction. The third direction is perpendicular to the first direction and the second direction, respectively. The first structure and the second structure are simultaneously formed on the lower cladding layer through secondary epitaxial growth; The second structure has multiple cross-sections perpendicular to the first direction, and the area of ​​the cross-section containing the top surface of the second structure is smaller than the area of ​​the cross-section containing the bottom surface of the second structure. Within the plane formed by the first direction and the third direction, the region of the second structure above the active layer is a narrowing region, and the second structure located in the narrowing region is a quasi-insulating structure.

2. The laser according to claim 1, characterized in that, Along the first direction, the area of ​​the cross section containing the bottom surface of the second structure gradually decreases to the area of ​​the cross section containing the top surface of the second structure.

3. The laser according to claim 2, characterized in that, Within the plane formed by the first direction and the third direction, the length of the bottom edge of the second structure is greater than the length of the top edge of the second structure; And / or, in the first direction, the top surface of the second structure is higher than the top surface of the active layer in the ridge waveguide.

4. The laser according to any one of claims 1-3, characterized in that, The active layer has a length of A in the third direction, and the second structure located on one side of the ridge waveguide has a length of C in the third direction, where C / A > 5; And / or, the thickness of the first structure in the first direction is 1.5 to 3 times the thickness of the second structure in the first direction.

5. The laser according to any one of claims 1-3, characterized in that, Within the plane formed by the second direction and the third direction, the base area of ​​the first structure is M, the base area of ​​the second structure is N, and 0.0025≤M / N≤0.06; And / or, the length of the first structure in the second direction is B, the length of the active layer in the third direction is A, and the top surface of the first structure in the first direction is higher than the top surface of the active layer.

6. The laser according to claim 1, characterized in that, And / or, the first structure includes a curved surface; the curved surface is disposed at the light-emitting position of the front cavity surface FF. Also includes:

7. The laser according to any one of claims 1-3, characterized in that, An insulating layer is disposed on the second structure along the first direction and covers a portion of the epitaxial stack; And an upper electrode, disposed on the insulating layer along the first direction, and covering the remaining portion of the epitaxial stack. The laser has a first etched surface and a second etched surface, and the first etched surface has a third angle between it and the surface formed by the first direction and the second direction, wherein 0° < the third angle < 90°; 8. The laser according to claim 7, characterized in that, And / or, the second etched surface has a fourth angle with the surface formed by the first direction and the second direction, where 0° < the fourth angle < 90°. include:

9. A method for fabricating a laser, characterized in that, ​ S1, an epitaxial stack is stacked on a substrate along a first direction, and a ridge waveguide region is defined on the epitaxial stack. The extension direction of the ridge waveguide region is a second direction from the front cavity surface of the laser to the rear cavity surface. The epitaxial stack includes a lower cladding layer, an active layer and an upper cladding layer. S2, non-waveguide regions are formed on both sides of the ridge waveguide region in the third direction; the third direction is perpendicular to the first direction and the second direction, respectively. S3 defines the cavity surface gap region through photolithography and forms the cavity surface region through etching. S4, a protective layer is fabricated above the ridge waveguide region; S5, selective growth is performed to form a first structure in the cavity surface gap region and a second structure in the non-waveguide region; the first structure and the second structure are simultaneously formed on the lower cladding layer through secondary epitaxial growth; the second structure has multiple cross-sections perpendicular to the first direction, and the area of ​​the cross-section containing the top surface of the second structure is smaller than the area of ​​the cross-section containing the bottom surface of the second structure; in the plane formed by the first direction and the third direction, the region of the second structure above the active layer is a narrowing region, and the second structure located in the narrowing region is a quasi-insulating structure; S6, remove the protective layer and form an insulating layer on the second structure and a portion of the ridge waveguide region; and form an upper electrode on the insulating layer and on at least a portion of the ridge waveguide region not covered by the insulating layer.

10. The method for fabricating a laser according to claim 9, characterized in that, The selective growth step includes: The growth temperature is 600℃-650℃, and the molar flow ratio of the group V element source gas to the group III element source gas introduced into the reaction chamber is greater than 50.

11. The method for fabricating a laser according to claim 9, characterized in that, Also includes: Etching is performed along the etching lines to form individual lasers; Wherein, in the plane formed by the second direction and the third direction, the etched line is set at a first angle with the extension direction of the ridge waveguide, where 0° < the first angle ≤ 30°; And / or, the angle between the etched surface formed after etching along the etch line and the plane formed by the first direction and the second direction is the second angle, where 0° < the second angle ≤ 45°.

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