Semiconductor laser and method of manufacturing the same

Abstract

The application discloses a semiconductor laser and a preparation method thereof. The semiconductor laser comprises a substrate layer, an echo wall microcavity arranged on one side of the substrate layer, and the echo wall microcavity comprises a first limiting layer, an active layer and a second limiting layer which are sequentially arranged on the substrate layer. The active layer is provided with N first through holes in a direction perpendicular to the substrate layer, N is a positive integer greater than or equal to 1, a geometric center point of a normal projection area of the active layer on the substrate layer is a first center point, a geometric center point of a normal projection area of the first through hole on the substrate layer is a second center point, the first center point and the second center point are not overlapped, and when N is greater than or equal to 2, the second center points corresponding to any two first through holes are asymmetrically arranged relative to the first center point. The semiconductor laser provided by the application can realize unidirectional laser emission.

Description

Technical Field

[0001] This invention relates to semiconductor The field of technology relates, in particular to a semiconductor laser and its fabrication method. Background Technology

[0002] A semiconductor microdisk laser is a microcavity laser based on the whispering-gallery mode. It typically consists of a disk-shaped dielectric material microdisk. The cavity is confined by total internal reflection at the curved interface of the microdisk. When light propagates within the microdisk, total internal reflection occurs at the edge of the microdisk, thus confining it within the microdisk. When the optical path length of the light propagating within the microdisk meets certain conditions, resonance occurs, generating laser light.

[0003] Existing semiconductor microdisk lasers, due to their total internal reflection whispering-gallery mode, confine most of the light field inside the microdisk. Furthermore, due to the isotropic nature of the microdisk, the emitted weak laser light is uniformly distributed in all directions, making it impossible for the light to be emitted in a directional manner. Summary of the Invention

[0004] This application provides a semiconductor laser and its fabrication method to solve the technical problem that existing microdisk lasers cannot emit laser light in a directional manner.

[0005] In view of the above problems, this application is made in order to provide a semiconductor laser and a method for fabricating the same that overcomes or at least partially solves the above problems.

[0006] In a first aspect, a semiconductor laser is provided, comprising: a substrate layer;

[0007] A whispering-gallery microcavity is disposed on one side of a substrate layer. The whispering-gallery microcavity includes a first confinement layer, an active layer, and a second confinement layer stacked sequentially on the substrate layer. The active layer is provided with N first vias along a direction perpendicular to the substrate layer, where N is a positive integer greater than or equal to 1. The geometric center point of the orthographic projection area of ​​the active layer on the substrate layer is the first center point, and the geometric center point of the orthographic projection area of ​​the first vias on the substrate layer is the second center point. The first center point and the second center point do not overlap with each other, and when N is greater than or equal to 2, the second center points corresponding to any two first vias are asymmetrically arranged with respect to the first center point.

[0008] The first electrode is disposed on the substrate layer and is in ohmic contact with the first confinement layer;

[0009] The second electrode is disposed on the side of the second confinement layer away from the active layer and is in ohmic contact with the second confinement layer.

[0010] Optionally, the first limiting layer is provided with N second through holes along a direction perpendicular to the substrate layer, each second through hole communicating with a first through hole, and / or, the second limiting layer is provided with N third through holes along a direction perpendicular to the substrate layer, each third through hole communicating with a first through hole.

[0011] Optionally, the first confinement layer includes a nanoporous layer and a first waveguide layer sequentially stacked on the substrate layer, wherein the refractive indices of the nanoporous layer, the first waveguide layer and the active layer increase sequentially.

[0012] The second confinement layer includes a second waveguide layer and a contact layer stacked sequentially on the active layer, with the refractive indices of the contact layer, the second waveguide layer and the active layer increasing sequentially.

[0013] The nanoporous layer is in ohmic contact with the first electrode;

[0014] The contact layer makes ohmic contact with the second electrode.

[0015] Optionally, the active layer includes M barrier layers and M-1 potential well layers stacked together, with the M barrier layers and M-1 potential well layers alternately arranged between the first waveguide layer and the second waveguide layer; the barrier layer includes Al x1 Ga (1-x1) N material, the potential well layer includes Al x2 Ga (1-x2) Material N, where M is a positive integer greater than or equal to 2, x1 and x2 are greater than zero and less than 1, and x1 is less than x2.

[0016] Optionally, the first electrode comprises a p-type doped electrode material;

[0017] The first waveguide layer consists of P-type doped Al. x3 Ga (1-x3) Material N, where x3 is greater than x1 and less than 1;

[0018] Nanoporous layers include p-type doped Al x4 Ga (1-x4) Material N, where x4 is greater than x3 and less than 1;

[0019] The second electrode comprises an N-type doped electrode material;

[0020] The second waveguide layer consists of N-type doped Al. x5 Ga (1-x5) Material N, where x5 is greater than x1 and less than 1;

[0021] The contact layer consists of N-type doped gallium nitride material.

[0022] Optionally, the first confinement layer may further include a current diffusion layer disposed between the nanoporous layer and the first waveguide layer.

[0023] Optionally, the current diffusion layer includes p-type doped Al. x6 Ga (1-x6) Material N, where x6 is greater than x3 and less than x4.

[0024] Optionally, the shape of the orthographic projection area of ​​the first via on the substrate layer can be circular, elliptical, or polygonal.

[0025] Optionally, the outer boundary shape of the orthographic projection region of the whispering microcavity on the substrate is elliptical, and when N equals 1, the orthographic projection of the first via on the substrate covers one focal point of the ellipse; or, the outer boundary shape of the orthographic projection region of the whispering microcavity on the substrate is circular, and when N equals 1, the orthographic projection of the first via on the substrate is located inside the circle and has a gap with the center of the circular region.

[0026] Secondly, this application provides a method for fabricating a semiconductor laser, comprising:

[0027] Obtain the substrate layer;

[0028] Based on the substrate, a first confinement layer, an active layer, and a second confinement layer are sequentially stacked. N first vias are formed on the active layer along a direction perpendicular to the substrate to obtain a whispering galvanic microcavity. N is a positive integer greater than or equal to 1. The geometric center point of the orthographic projection area of ​​the active layer on the substrate is the first center point, and the geometric center point of the orthographic projection area of ​​the first via on the substrate is the second center point. When N equals 1, the first center point and the second center point do not overlap. When N is greater than or equal to 2, the second center points corresponding to any two first vias are asymmetrically set with respect to the first center point.

[0029] A first electrode is formed on the substrate layer to make ohmic contact with the first confinement layer;

[0030] A second electrode is formed on the side of the second confinement layer away from the active layer, making ohmic contact with the second confinement layer, thus obtaining a semiconductor laser.

[0031] The technical solution provided in this application has at least the following technical effects or advantages:

[0032] The semiconductor laser and its fabrication method provided in this application involve arranging a first via in the active layer of a whispering-gallery microcavity to disrupt the isotropy of the active layer, thereby forming a resonant cavity structure with an asymmetric phase shift. Current is injected into the whispering-gallery microcavity through a first electrode and a second electrode. The injected electrons and holes recombine in the active layer, releasing energy and generating spontaneous emission. When the photons generated by spontaneous emission are reflected multiple times in the asymmetric resonant cavity, the asymmetry of the phase shift will cause differences in the loss, gain, and other characteristics of the light field modes propagating in different directions within the cavity, making it easier for the light field mode in a certain direction to meet the conditions for laser oscillation, thereby achieving unidirectional laser emission.

[0033] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 This is a partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of this application;

[0036] Figure 2 This is a projection diagram of a semiconductor laser provided in an embodiment of this application;

[0037] Figure 3 This is a projection diagram of a semiconductor laser provided in an embodiment of this application;

[0038] Figure 4 This is a partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of this application;

[0039] Figure 5 This is a partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of this application;

[0040] Figure 6 A schematic cross-sectional view of a semiconductor laser provided in an embodiment of this application;

[0041] Figure 7 A schematic cross-sectional view of a semiconductor laser provided in an embodiment of this application;

[0042] Figure 8This is a flowchart of the semiconductor laser fabrication method in the embodiments of this application;

[0043] Figure 9 A cross-sectional view of a semiconductor laser provided in an embodiment of this application;

[0044] Figure 10 A top cross-sectional view of a semiconductor laser provided in an embodiment of this application;

[0045] Figure 11 This application provides a step diagram illustrating a method for fabricating a semiconductor laser.

[0046] Figure 12 This application provides a step diagram illustrating a method for fabricating a semiconductor laser.

[0047] Figure 13 This application provides a step diagram illustrating a method for fabricating a semiconductor laser.

[0048] Figure 14 This application provides a step diagram illustrating a method for fabricating a semiconductor laser.

[0049] Figure 15 This application provides a step diagram illustrating a method for fabricating a semiconductor laser.

[0050] Figure 16 This is a step diagram illustrating a method for fabricating a semiconductor laser, as provided in an embodiment of this application. Detailed Implementation

[0051] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings.

[0052] The accompanying drawings illustrate various structural schematics according to embodiments of this application. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0053] To facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with essentially the same function and effect. For example, the first value and the second value are only used to distinguish different values ​​and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0054] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0055] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0056] In the context of this disclosure, when a layer / component is referred to as being "above" another layer / component, that layer / component may be directly above the other layer / component, or there may be an intermediate layer / component between them. Additionally, if a layer / component is "above" another layer / component in one orientation, then when the orientation is reversed, that layer / component may be "below" the other layer / component. In the context of this disclosure, similar or identical components may be denoted by the same or similar reference numerals.

[0057] To better understand the above technical solutions, the following will describe the above technical solutions in detail with reference to specific implementation methods. It should be understood that the embodiments of this disclosure and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0058] A microdisk laser is a microcavity laser based on the whispering-gallery mode. It typically consists of a disk-shaped dielectric material. The cavity confinement relies primarily on total internal reflection at the curved interface of the disk. When light propagates along the circumference of the disk in whispering-gallery mode, total internal reflection occurs on the inner wall of the disk, confining it within the disk. When the optical path length of the light within the disk meets certain conditions, resonance occurs, generating laser light. Due to its small size and low threshold current, microdisk lasers have become a research hotspot in recent years.

[0059] Microdisk structures can effectively enhance the optical field intensity of a laser resonant cavity, thereby improving laser performance. However, microdisk lasers face two main problems:

[0060] First, because the Whispering Gallery Mode (WGM) micro-cavity with total internal reflection confines most of the optical field inside the micro-disk, and because of the isotropic nature of the micro-disk, the emitted weak laser is uniformly distributed in all directions, meaning that the emission characteristics (such as intensity and frequency) of the laser are basically the same in all directions. This characteristic limits its application in many fields.

[0061] Second, as an electrically injected laser, the transition from optical pumping to electrical injection still faces challenges. Although it is simply adding electrical contact on the basis of optical pumping, the metal layer in the microdisk structure may introduce additional reflection and absorption. Furthermore, the bottom current of the traditional microdisk laser can only be injected from the narrow bottom support, making it difficult to inject current effectively and resulting in poor heat dissipation. This significantly increases the difficulty of electrically injected laser emission.

[0062] In view of this, this application provides a semiconductor laser, please refer to... Figure 1 , Figure 1 This is a simplified schematic diagram of the structure of a semiconductor laser in an embodiment of this application. The semiconductor laser includes: a substrate layer 101, a whispering-gallery microcavity 102, a first electrode 103, and a second electrode 104.

[0063] The whispering-gallery microcavity 102 is disposed on one side of the substrate layer 101, such as Figure 1 As shown, the whispering-gallery microcavity 102 includes a first confinement layer 1021, an active layer 1022, and a second confinement layer 1023 sequentially stacked on a substrate layer 101. The refractive index of the first confinement layer 1021 is lower than that of the active layer 1022, and the refractive index of the second confinement layer 1023 is also lower than that of the active layer 1022. The lower refractive indices of the first and second confinement layers 1021 compared to the active layer 1022 are beneficial for confining light within the active layer 1022.

[0064] The active layer 1022 is provided with N first vias 1024 along a direction perpendicular to the substrate layer 101, where N is a positive integer greater than or equal to 1. The geometric center point of the orthographic projection area of ​​the active layer 1022 onto the substrate layer 101 is the first center point, and the geometric center point of the orthographic projection area of ​​the first via 1024 onto the substrate layer 101 is the second center point. When N equals 1, the first center point and the second center point do not overlap. When N is greater than or equal to 2, the second center points corresponding to any two first vias 1024 are asymmetrically arranged relative to the first center point. The first electrode 103 is disposed on the substrate layer 101 and is in ohmic contact with the first confinement layer 1021; the second electrode 104 is disposed on the side of the second confinement layer 1023 away from the active layer 1022 and is in ohmic contact with the second confinement layer 1023.

[0065] The semiconductor laser provided in this application embodiment, by setting N asymmetric first vias 1024 in the active layer 1022 of the whispering-gallery microcavity 102, disrupts the rotational symmetry of the active layer 1022, making the whispering-gallery microcavity 102 as a whole form a resonant cavity structure with an asymmetric phase shift position. During operation, current is injected into the whispering-gallery microcavity 102 through the first electrode 103 and the second electrode 104. The injected electrons and holes recombine in the active layer 1022, releasing energy and generating spontaneous emission. When the photons generated by spontaneous emission are reflected multiple times in the asymmetric resonant cavity, the asymmetry of the phase shift position will cause differences in the loss, gain and other characteristics of the light field modes propagating in different directions in the cavity, making it easier for the light field mode in a certain direction to meet the conditions for laser oscillation, thereby realizing unidirectional laser emission.

[0066] The semiconductor laser provided in this application embodiment can adopt a cylindrical structure, an elliptical cylindrical structure, or a square cylindrical structure for the whispering microcavity 102. In one example provided in this application, the whispering microcavity 102 adopts a cylindrical structure, and the outer boundary shape of the orthographic projection area of ​​the whispering microcavity 102 on the substrate layer 101 is circular. When N equals 1, the orthographic projection of the first via 1024 on the substrate layer 101 is located inside the circle and has a gap with the center of the circle.

[0067] The whispering-gallery microcavity 102 has a multi-layered structure. When the whispering-gallery microcavity 102 adopts a cylindrical structure, the active layer 1022 corresponds to a structural layer with a circular boundary, and the outer boundary shape of the orthographic projection area of ​​the active layer 1022 on the substrate layer 101 is circular. When the whispering-gallery microcavity 102 adopts an elliptical cylindrical structure, the active layer 1022 corresponds to a structural layer with an elliptical boundary, and the outer boundary shape of the orthographic projection area of ​​the active layer 1022 on the substrate layer 101 is elliptical. When the whispering-gallery microcavity 102 adopts a square cylindrical structure, the active layer 1022 corresponds to a structural layer with a square boundary, and the outer boundary shape of the orthographic projection area of ​​the active layer 1022 on the substrate layer 101 is square.

[0068] For example, if the whispering-gallery microcavity 102 adopts a cylindrical structure, then as Figure 2 As shown, the first outer boundary 201 of the orthographic projection of the whispering glide microcavity 102 onto the substrate 101 forms a circle as shown in Figures a, b, c, and d. The circular region enclosed by the first outer boundary 201 has a first center 202. The second outer boundary 203 of the orthographic projection of the first via 1024 onto the substrate 101 forms a circle as shown in Figures a, b, or c. The circular region enclosed by the second outer boundary 203 has a second center 204. When N equals 1, there is a gap h between the first center 202 and the second center 204 as shown in Figure a.

[0069] When N is greater than or equal to 2, for example, when N equals 2, the circular region enclosed by the two second outer boundaries 203 is asymmetrically set relative to the first center 202, as shown in Figure b. Still as... Figure 2 As shown, when the first through hole 1024 is two circular holes, when the diameters of the two first through holes 1024 are the same, the diameters of the circular areas enclosed by the two second outer boundaries 203 are also the same, and the corresponding two second circle centers 204 are asymmetrically arranged relative to the first circle center 202 as shown in Figure b.

[0070] It is understandable that when the two first through holes 1024 are circular holes with different diameters, the diameters of the circular regions enclosed by the two second outer boundaries 203 are also different, and the corresponding two second center 204 can be symmetrically arranged relative to the first center 202. This is because when the diameters of the circular regions enclosed by the two second outer boundaries 203 are different, even if the corresponding two second center 204 are symmetrically arranged relative to the first center 202, the orthographic projection of the active layer 1022 onto the substrate layer 101 is non-centrally symmetrical. Thus, the whispering-gallery microcavity 102 is a resonant cavity structure with asymmetrical phase shift positions, which can realize unidirectional laser emission.

[0071] For example, if N equals 3, then... Figure 2 As shown in Figure c, when the three first through holes 1024 have different sizes, the three second circles 203 with different diameters can be arranged unevenly around the first circle center 202 as shown in Figure c, or they can be arranged evenly around the first circle center 202.

[0072] It is understandable that the first through hole 1024 can also be an elliptical hole, a polygonal hole, such as a pentagonal hole, and so on. Figure 2 As shown, the orthographic projection 205 of the first via 1024 onto the substrate 101 is an ellipse or a polygon as shown in Figure d. This application does not limit the shape, size, number, etc. of the first via 1024.

[0073] In some examples, the whispering-gallery microcavity 102 adopts an elliptical cylindrical structure, such as Figure 3 As shown, the outer boundary of the orthographic projection region 301 of the whispering glide microcavity 102 on the substrate 101 is an ellipse as shown in Figure a or Figure b. This ellipse has a first focal point 302 and a second focal point 303. The orthographic projection 304 of the first via 1024 on the substrate 101 covers the first focal point 302 of the ellipse as shown in Figure a, or covers the second focal point 303 of the ellipse as shown in Figure b. It can be understood that the orthographic projection region of the active layer 1022 on the substrate 101 is an elliptical region whose outer boundary coincides with the outer boundary of the orthographic projection region 301 of the whispering glide microcavity 102 on the substrate 101.

[0074] Still Figure 3 As shown, when the orthographic projection 304 of the first via 1024 on the substrate 101 is a circle as shown in Figure a, the diameter D1 of the circle is in the range of [0.1H, H). Or when the orthographic projection 304 of the first via 1024 on the substrate 101 is a regular polygon as shown in Figure b, the diameter D2 of the circumcircle of the regular polygon is in the range of [0.1H, H). Where H is the length of the major axis of the ellipse formed by the outer boundary of the orthographic projection region 301 of the whispering gable microcavity 102 on the substrate 101.

[0075] The semiconductor laser examples provided in this application, by introducing a single-point focal hole and an asymmetric multi-point focal hole, can suppress higher-order modes of the semiconductor laser, reduce the laser threshold of the fundamental mode, increase the loss of higher-order modes, and effectively control the number of modes. At the same time, the asymmetric hole design destroys the isotropy of the whispering-gallery microcavity 102, and the emitted laser direction is not uniform in all directions. The laser intensity is only maximum at a certain specific angle, realizing the directional emission of laser by the whispering-gallery microcavity 102, improving the light collection efficiency, which is crucial for promoting the coupling of optoelectronic devices.

[0076] In some alternative implementations, such as Figure 4 As shown, the first limiting layer 1021 is provided with N second through holes 401 along a direction perpendicular to the substrate layer 101, each second through hole 401 communicating with a first through hole 1024, and / or as shown in the figure. Figure 5 As shown, the second limiting layer 1023 is provided with N third through holes 501 along the direction perpendicular to the substrate layer 101, and each third through hole 501 is connected to a first through hole 1024.

[0077] It is understandable that when the third through-hole 501, the first through-hole 1024, and the second through-hole 401 are connected in sequence, a micro-hole is formed that penetrates the whispering-gallery microcavity 102. Theoretically, as the main structural layer of the semiconductor laser, the active layer 1022 only needs to be set with the first through-hole 1024 to break the isotropy of the active layer 1022 to achieve unidirectional laser output. However, from the perspective of processing technology, processing only the first through-hole 1024 is relatively more expensive and the process is relatively more complicated. On the other hand, processing the micro-hole that penetrates the whispering-gallery microcavity 102 in one go is relatively simple, the easiest to achieve, and the lower cost.

[0078] In some alternative implementations, such as Figure 6 As shown, the first confinement layer 1021 includes a nanoporous layer 601 and a first waveguide layer 602 sequentially stacked on the substrate layer 101. The refractive indices of the nanoporous layer 601, the first waveguide layer 602, and the active layer 1022 increase sequentially. The refractive index of the first waveguide layer 602 is higher than that of the nanoporous layer 601 and lower than that of the active layer 1022. It can confine the light field generated by the active layer 1022, causing it to propagate along a specific direction, reducing light scattering and loss in other areas, thereby improving the light utilization efficiency and output power.

[0079] The second confinement layer 1023 includes a second waveguide layer 603 and a contact layer 604 sequentially stacked on the active layer 1022, wherein the refractive indices of the contact layer 604, the second waveguide layer 603 and the active layer 1022 increase sequentially; the nanoporous layer 601 is in ohmic contact with the first electrode 103; and the contact layer 604 is in ohmic contact with the second electrode 104.

[0080] The active layer 1022, as the primary light-emitting structure of the whispering-gallery microcavity 102, can employ a quantum well structure or a quantum dot structure. For example, the active layer 1022 employing a quantum well structure includes M stacked barrier layers and M-1 potential well layers, with the M barrier layers and M-1 potential well layers alternately arranged between the first waveguide layer 602 and the second waveguide layer 603; the barrier layers include Al... x1 Ga (1-x1) N material, the potential well layer includes Al x2 Ga (1-x2) Material N, where M is a positive integer greater than or equal to 2, x1 and x2 are greater than zero and less than 1, and x1 is less than x2. The refractive indices of the nanoporous layer 601, the first waveguide layer 602, and the barrier layer on the side of the first waveguide layer 602 away from the nanoporous layer 601 increase sequentially. The refractive indices of the contact layer 604, the second waveguide layer 603, and the barrier layer on the side of the second waveguide layer 603 away from the contact layer 604 also increase sequentially.

[0081] In some alternative implementations, the value of x1 ranges from 0.1 to 0.5 nanometers. For example, the value of x1 can be 0.3 nanometers, 0.35 nanometers, 0.4 nanometers, 0.45 nanometers, or 0.5 nanometers.

[0082] The semiconductor laser provided in this application embodiment includes a first electrode 103 comprising a p-type doped electrode material; and a first waveguide layer 602 comprising a p-type doped Al. x3 Ga (1-x3) N material, wherein x3 is greater than x1 and less than 1; the nanoporous layer 601 includes p-type doped Al. x4 Ga (1-x4) Material N, where x4 is greater than x3 and less than 1.

[0083] The nanoporous layer 601 can be made from p-type doped Al x4 Ga (1-x4) The nanoporous layer 601 is fabricated by introducing nanopores through electrochemical etching on N-material. This nanoporous layer increases the interfaces and channels within the semiconductor material, providing more transport paths for charge carriers (electrons and holes), reducing carrier transport resistance, and thus improving carrier injection efficiency and mobility. Since x1, x2, x3, and x4 increase sequentially, the proportion of aluminum in the materials of the nanoporous layer 601, the first waveguide layer 602, and the barrier layer decreases sequentially, resulting in a sequential decrease in refractive index, which is beneficial for delivering light into the active layer 1022. The porous structure of the nanoporous layer 601 further reduces the effective refractive index by introducing nanopores, thus creating a larger refractive index difference with the active layer 1022. This helps electrons and holes to be injected more effectively into the active layer 1022, increasing the carrier concentration in the active layer 1022 and thereby improving the luminous efficiency of the semiconductor laser. The nanoporous layer 601 can also confine the light field mode to the vicinity of the active layer 1022, and since it does not require undercutting, it has higher heat dissipation efficiency.

[0084] The porous structure of the nanoporous layer 601, in conjunction with the structure of the first through-hole 1024, further confines the light field to the active layer 1022, improving the overlap coefficient, suppressing higher-order modes, and disrupting symmetry, thereby achieving low-threshold electrically injected unidirectional high-power laser output. Compared with traditional laser solutions, this approach offers advantages such as system simplicity, high stability, and the elimination of the need for secondary epitaxy and complex active / passive integration technologies. It holds significant application value in optical communication, optical sensing, photoelectric detection, and photonic computing.

[0085] The semiconductor laser provided in this application embodiment has a second electrode 104 comprising an N-type doped electrode material. The second waveguide layer 603 comprises N-type doped Al. x5 Ga (1-x5) The material is N-type doped gallium nitride, wherein x5 is greater than x1 and less than 1. The contact layer 604 comprises N-type doped gallium nitride material.

[0086] The contact layer 604 is used to inject current stably, uniformly, and efficiently into the active layer 1022 of the whispering-gallery microcavity 102, reducing resistance loss at the interface between the second electrode 104 and the whispering-gallery microcavity 102, improving current transmission efficiency, and thus enhancing the overall performance and photoelectric conversion efficiency of the semiconductor laser, ensuring the normal operation and consistent output characteristics of the semiconductor laser. On the other hand, the contact layer 604 also protects the internal structure of the whispering-gallery microcavity 102: preventing the semiconductor materials inside the semiconductor laser from contacting the external environment and undergoing oxidation or other chemical reactions, thereby improving the stability and lifespan of the semiconductor laser.

[0087] The refractive index of the second waveguide layer 603 is higher than that of the contact layer 604 and lower than that of the active layer 1022. This confines the light field generated by the active layer 1022, increases the recombination probability of electrons and holes in the active layer 1022 of the quantum well structure, and reduces the scattering and loss of light in other areas, thereby improving the light utilization efficiency and output power, and thus improving the luminous efficiency of the semiconductor laser.

[0088] In some alternative implementations, such as Figure 7 As shown, the first confinement layer 1021 further includes a current diffusion layer 701, which is disposed between the nanoporous layer 601 and the first waveguide layer 602. The current diffusion layer 701 is used to uniformly inject the current introduced by the first electrode 103 into the active layer 1022 to achieve efficient and stable laser emission and improve the output power and beam quality of the semiconductor laser.

[0089] The current diffusion layer 701 includes p-type doped Al x6 Ga (1-x6) The material is N, where x6 is greater than x3 and less than x4. Since x6 is between x3 and x4, the refractive index of the current diffusion layer 701 is greater than that of the nanoporous layer 601 and less than that of the first waveguide layer 602, ensuring that light is delivered into the active layer 1022. P-type doped Al x6 Ga (1-x6) The current diffusion layer 701 of N has high conductivity and suitable carrier mobility, which enables the current to diffuse uniformly in the active layer 1022 laterally, avoiding current concentration in local areas, thereby improving the overall luminous efficiency of the active layer 1022 and reducing the optical power loss and light spot unevenness caused by uneven current.

[0090] Based on the same inventive concept, embodiments of this application also provide a method for fabricating a semiconductor laser, such as... Figure 8 As shown, the method includes:

[0091] S801, Obtain substrate layer 101;

[0092] S802. Based on the substrate layer 101, a first confinement layer 1021, an active layer 1022, and a second confinement layer 1023 are sequentially stacked. N first vias 1024 are formed on the active layer 1022 along a direction perpendicular to the substrate layer 101 to obtain a whispering-gallery microcavity 102. N is a positive integer greater than or equal to 1. The geometric center point of the orthographic projection area of ​​the active layer 1022 on the substrate layer 101 is the first center point, and the geometric center point of the orthographic projection area of ​​the first via 1024 on the substrate layer 101 is the second center point. When N equals 1, the first center point and the second center point do not overlap. When N is greater than or equal to 2, the second center points corresponding to any two first vias 1024 are asymmetrically set with respect to the first center point.

[0093] S803, A first electrode 103 is formed on the substrate 101 to make ohmic contact with the first confinement layer 1021;

[0094] S804. On the side of the second confinement layer 1023 away from the active layer 1022, a second electrode 104 is formed in ohmic contact with the second confinement layer 1023 to obtain a semiconductor laser.

[0095] The semiconductor laser fabrication method provided in this application, through an asymmetric via (i.e., first through-hole 1024) design, disrupts the isotropy of the whispering-gallery microcavity 102, causing the emitted laser direction to be non-uniform in all directions, with the laser intensity maximizing only at a specific angle. This solves the problem of the whispering-gallery microcavity 102's inability to emit lasers in a directional manner. The refractive index of the first confinement layer 1021 is lower than that of the active layer 1022, and the refractive index of the second confinement layer 1023 is also lower than that of the active layer 1022. The lower refractive indices of the first and second confinement layers 1021 and 1023 compared to the active layer 1022 are beneficial for confining light within the active layer 1022.

[0096] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be implemented independently or in combination with each other. The same or similar concepts or processes may not be described again in some embodiments.

[0097] Taking the semiconductor laser provided in the above embodiments as an example, applied to an AlGaN-based single-mode unidirectional ultraviolet microcavity laser, the AlGaN-based single-mode unidirectional ultraviolet microcavity laser includes:

[0098] The whispering-gallery microcavity, P-type electrode 902, and N-type electrode 903 are epitaxially grown on the substrate 901. The outer contour of the whispering-gallery microcavity is a cylindrical structure, such as... Figure 9As shown, the epitaxial structure layer consists of a 700nm NP-AlGaN nanoporous layer 904 and a 350nm p-Al layer stacked on a substrate 901. 0.6 Ga 0.4 The current diffusion layer of N material is 905 nm, 150 nm p-Al. 0.55 Ga 0.45 The first waveguide layer of N material is 906, and the four layers are 9nm Al. 0.45 Ga 0.55 The barrier layer 907 of N material and 3 layers of 2nm Al 0.55 Ga 0.45 The active layer is composed of alternating 908 N-material potential well layers and 100nm n-Al. 0.55 Ga 0.45 The second waveguide layer 909 of N and the contact layer 910 of 100nm n-GaN material.

[0099] It should be noted that NP-AlGaN stands for nanoporous aluminum gallium nitride. 700nm NP-AlGaN refers to nanoporous aluminum gallium nitride with a thickness of 700nm. The AlGaN in NP-AlGaN refers to the aluminum gallium nitride material system and does not limit the specific ratio of Al to Ga. In this application, the NP-AlGaN applied to the nanoporous layer 904 can be p-type doped nanoporous aluminum gallium nitride, such as p-Al. 0.95 Ga 0.05 N, p-Al 0.9 Ga 0.1 N, p-Al 0.85 Ga 0.15 N, p-Al 08 Ga 0.2 N, p-Al 0.75 Ga 0.25 N or p-Al 0.7 Ga 0.3 N.

[0100] like Figure 10 As shown, the whispering-gallery microcavity has etched holes 1001 inside. The holes 1001 are used to disrupt the rotational symmetry of the whispering-gallery microcavity in order to achieve directional laser emission. A P-type electrode 902 is disposed on the substrate 901 and surrounds the nanoporous layer 904 of the whispering-gallery microcavity, and an N-type electrode 903 is disposed on the contact layer 910 at the top of the whispering-gallery microcavity.

[0101] It is understandable that the size, position, and shape of the hole 1001 are not limited, and can be set according to the direction and intensity of the laser to be generated. Here, we only use a cylindrical whispering wall microcavity with an eccentrically set hole 1001 as an example for illustration. Figure 9 This example only shows the arrangement of the epitaxial structural layers of the whispering galvanic microcavity and does not limit the specific thickness of each epitaxial structural layer.

[0102] To fabricate the single-mode unidirectional ultraviolet microcavity laser in this embodiment, this embodiment provides a method for fabricating a single-mode lasing microcavity laser, including the following steps:

[0103] S1, as Figure 11 As shown, an AlN (aluminum nitride) substrate 1101 was obtained, and an epitaxial structure layer 1102 of a whispering galvanic microcavity was epitaxially grown on the AlN (aluminum nitride) substrate 1101 using a metal-organic chemical vapor deposition (MOCVD) system to obtain the semiconductor material shown in Figure a. Photoresist was spin-coated onto the semiconductor material and baked at high temperature to obtain the first photoresist layer 1103 shown in Figure b.

[0104] S2, as Figure 12 As shown, a laser is used to expose the first photoresist layer 1103 to a predetermined shape, and the exposed portion is washed away to form the first window 1201 shown in Figures a and b. The epitaxial structure layer 1102 is exposed to the first window 1201. The outer boundary of the first window 1201 forms a first circle, and the inner boundary of the first window 1201 forms a second circle. The diameter of the second circle is smaller than the radius of the first circle, and there is a gap between the center point of the second circle and the center point of the first circle.

[0105] S3, as Figure 13 As shown, a metal, such as Cr, is deposited on the semiconductor material below the first window 1201 by thermal evaporation to form an evaporated metal layer 1301. It can be understood that the evaporated metal layer 1301 will also cover the unexposed portion of the first photoresist layer 1103.

[0106] S4, as Figure 14 As shown, acetone is used to clean and remove the unexposed portion of the first photoresist layer 1103. The metal of the vapor-deposited metal layer 1301 on the unexposed portion of the first photoresist layer 1103 will be removed along with the first photoresist layer 1103. The unremoved metal forms the metal mask layer 1401 shown in Figures a and b. The portion of the epitaxial structure layer 1102 not covered by the metal mask layer 1401 is exposed.

[0107] S5, such as Figure 15As shown, through an etching process, the portion of the epitaxial structure layer 1102 not covered by the metal mask layer 1401 is etched to form the whispering-gallery microcavity 1501 shown in Figure a. The whispering-gallery microcavity 1501 has a micro-hole 1502 penetrating through it in a direction perpendicular to the substrate 1101, exposing the substrate in the micro-hole 1502. The portion of the epitaxial structure layer 1102 that is removed is etched because it lacks the protection of the metal mask layer 1401.

[0108] S6, such as Figure 16 As shown in Figure a, the metal mask layer 1401 is washed away, exposing the side of the whispering-gallery microcavity 1501 away from the substrate 1101 as shown in Figure b. A P-type electrode 1601, as shown in Figures b and c, is formed on the substrate 1101, and an N-type electrode 1602, as shown in Figures b and c, is formed on the side of the whispering-gallery microcavity 1501 away from the substrate 1101, thus obtaining a unidirectional ultraviolet microcavity laser. It can be understood that the P-type electrode 1601 is in ohmic contact with the nanoporous layer at the bottom of the whispering-gallery microcavity 1501, and the N-type electrode 1602 is in ohmic contact with the contact layer at the top of the whispering-gallery microcavity 1501.

[0109] The unidirectional ultraviolet microcavity laser obtained in the above embodiments addresses the high threshold problem of existing microcavity lasers by forming micro-holes to make the cross-section of the whispering-gallery microcavity non-rotationally symmetric. This disrupts the isotropy of the whispering-gallery microcavity, resulting in a non-uniform emission laser direction and maximum laser intensity only at a specific angle. This enables more efficient unidirectional emission of the waveguide laser mode within the whispering-gallery cavity, improving coupling output efficiency and output optical power. Its fabrication process is simple, low-cost, and offers high power in a small size. The whispering-gallery microcavity structure allows the laser to operate efficiently even at a relatively small size, facilitating integration and miniaturization, and adapting to various application scenarios.

[0110] 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.

[0111] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

Claims

1. A semiconductor laser, characterized by, The application relates to a back-wall micro-cavity structure, which comprises the following parts: a substrate layer; a back-wall micro-cavity arranged on one side of the substrate layer, wherein the back-wall micro-cavity comprises a first limiting layer, an active layer and a second limiting layer which are sequentially arranged on the substrate layer, the active layer is provided with N first through holes in a direction perpendicular to the substrate layer, N is a positive integer greater than or equal to 1, the geometric center point of the normal projection area of the active layer on the substrate layer is a first center point, the geometric center point of the normal projection area of the first through hole on the substrate layer is a second center point, the first center point and the second center point are not overlapped, and when N is greater than or equal to 2, the second center points corresponding to any two first through holes are asymmetrically arranged relative to the first center point; a first electrode arranged on the substrate layer and in ohmic contact with the first limiting layer; a second electrode arranged on the side of the second limiting layer away from the active layer and in ohmic contact with the second limiting layer.

2. The semiconductor laser of claim 1, wherein The first limiting layer is provided with N second through holes in a direction perpendicular to the substrate layer, each second through hole is in communication with one first through hole, and / or the second limiting layer is provided with N third through holes in a direction perpendicular to the substrate layer, each third through hole is in communication with one first through hole.

3. The semiconductor laser of claim 1, wherein, The first limiting layer comprises a nanoporous layer and a first waveguide layer which are sequentially arranged on the substrate layer, and the refractive indexes of the nanoporous layer, the first waveguide layer and the active layer sequentially increase; The second limiting layer comprises a second waveguide layer and a contact layer which are sequentially arranged on the active layer, and the refractive indexes of the contact layer, the second waveguide layer and the active layer sequentially increase; The nanoporous layer is in ohmic contact with the first electrode; The contact layer is in ohmic contact with the second electrode.

4. The semiconductor laser of claim 3, wherein the first and second waveguides are formed by a first and second ridge, respectively. The active layer comprises M barrier layers and M-1 well layers arranged in a stack, the M barrier layers and the M-1 well layers are arranged alternately between the first waveguide layer and the second waveguide layer; the barrier layer comprises Al x1 Ga (1-x1) N material, the well layer comprises Al x2 Ga (1-x2) N material, wherein M is a positive integer greater than or equal to 2, x1 and x2 are greater than zero and less than 1, and x1 is less than x2.

5. The semiconductor laser of claim 4, wherein the first and second waveguides are formed by a first and second etch, respectively. The first electrode comprises a P-doped electrode material; The first waveguide layer includes P-type doped Al x3 Ga (1-x3) N material, where x3 is greater than x1 and less than 1. The nanoporous layer comprises P-type doped Al x4 Ga (1-x4) N material, wherein x4 is greater than x3 and less than 1. The second electrode comprises an N-doped electrode material; The second waveguide layer includes N-type doped Al x5 Ga (1-x5) N material, where x5 is greater than x1 and less than 1. The contact layer comprises an N-doped gallium nitride material.

6. The semiconductor laser of claim 5, wherein, The first limiting layer further comprises a current diffusion layer arranged between the nanoporous layer and the first waveguide layer.

7. The semiconductor laser of claim 6, wherein the first and second waveguides are formed by a first and second etch, respectively. The current spreading layer includes P-type doped Al x6 Ga (1-x6) N material, where x6 is greater than x3 and less than x4.

8. The semiconductor laser of claim 1, wherein, The normal projection area of the first through hole on the substrate layer is in a shape of a circle, an ellipse or a polygon.

9. The semiconductor laser of claim 1, wherein, The outer boundary shape of the normal projection area of the back-wall micro-cavity on the substrate layer is an ellipse, when N is equal to 1, the normal projection of the first through hole on the substrate layer covers one focus point of the ellipse; or the outer boundary shape of the normal projection area of the back-wall micro-cavity on the substrate layer is a circle, when N is equal to 1, the normal projection of the first through hole on the substrate layer is located in the circle and has a gap with the center of the circle.

10. A method of manufacturing a semiconductor laser, characterized by, The application further relates to a preparation method of the back-wall micro-cavity structure, which comprises the following steps: obtaining a substrate layer; Based on the substrate layer, a first confinement layer, an active layer and a second confinement layer are sequentially stacked, and N first through holes are formed on the active layer in a direction perpendicular to the substrate layer to obtain a whispering gallery microcavity, N being a positive integer greater than or equal to 1, wherein a geometric center point of a projection area of the active layer on the substrate layer is a first center point, a geometric center point of a projection area of the first through hole on the substrate layer is a second center point, when N is equal to 1, the first center point and the second center point do not overlap each other, and when N is greater than or equal to 2, the second center points corresponding to any two first through holes are asymmetrically arranged relative to the first center point; a first electrode in ohmic contact with the first confinement layer is formed on the substrate layer; a second electrode in ohmic contact with the second confinement layer is formed on a side of the second confinement layer away from the active layer to obtain a semiconductor laser.

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