Semiconductor laser and preparation method thereof

Abstract

The invention discloses a semiconductor laser and a preparation method thereof, and the semiconductor laser comprises a substrate layer; the echo wall microcavity is arranged on one side of the substrate layer, 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 in a stacked mode, the active layer is provided with N first through holes in the direction perpendicular to the substrate layer, N is a positive integer larger than or equal to 1, and N is a positive integer larger than or equal to 1; the geometric center point of the orthographic projection area of the active layer on the substrate layer is a first center point, the geometric center point of the orthographic projection area of the first through hole on the substrate layer is a second center point, and the first center point and the second center point are not overlapped with each other; 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 limiting layer; and the second electrode is in ohmic contact with the second limiting layer. The semiconductor laser provided by the invention can realize one-way laser emission.

Description

Technical Field

[0001] The present invention relates to semiconductor The technical field relates particularly to a semiconductor laser and a method for preparing the same. Background Art

[0002] A semiconductor microdisk laser is a microcavity laser based on the whispering gallery mode. It is usually composed of a disk-shaped dielectric material to form a microdisk. The cavity is confined by total reflection at the curved interface of the microdisk. When light propagates in the microdisk, it is totally reflected at the edge of the microdisk and is thus confined within the microdisk. When the optical path of light propagating within the microdisk meets certain conditions, resonance is formed and laser is generated.

[0003] Existing semiconductor microdisk lasers confine most of the light field inside the microdisk due to the whispering gallery mode of total internal reflection, and due to the isotropy of the microdisk, the emitted weak laser is evenly distributed in all directions, and the light cannot be emitted in a direction. Summary of the invention

[0004] The present application provides a semiconductor laser and a method for preparing the same, so as to solve the technical problem that the existing micro-disk laser cannot emit laser in a direction.

[0005] In view of the above problems, the present application is proposed to provide a semiconductor laser and a method for manufacturing the same that overcomes the above problems 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 arranged on one side of a substrate layer, the whispering gallery microcavity comprises a first restriction layer, an active layer and a second restriction layer which are sequentially stacked 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 orthographic projection area of ​​the active layer on the substrate layer is the first center point, the geometric center point of the orthographic projection area of ​​the first through hole on the substrate layer is the second center point, 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;

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

[0009] The second electrode is arranged on a 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 restriction layer is provided with N second through holes along a direction perpendicular to the substrate layer, each second through hole is connected to a first through hole, and / or the second restriction layer is provided with N third through holes along a direction perpendicular to the substrate layer, each third through hole is connected to a first through hole.

[0011] Optionally, the first confinement layer includes a nanoporous layer and a first waveguide layer stacked in sequence on the substrate layer, and the refractive indices of the nanoporous layer, the first waveguide layer and the active layer increase in sequence;

[0012] The second confinement layer comprises a second waveguide layer and a contact layer which are sequentially stacked on the active layer, and the refractive indexes of the contact layer, the second waveguide layer and the active layer are increased in sequence;

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

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

[0015] Optionally, the active layer includes M barrier layers and M-1 potential well layers stacked in layers, and the M barrier layers and the M-1 potential well layers are 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) 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.

[0016] Optionally, the first electrode includes a P-type doped electrode material;

[0017] 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;

[0018] The nanoporous layer includes P-type doped Al x4 Ga (1-x4) N material, wherein x4 is greater than x3 and less than 1;

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

[0020] The second waveguide layer includes N-type doped Al x5 Ga (1-x5) N material, wherein x5 is greater than x1 and less than 1;

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

[0022] Optionally, the first limiting layer further includes a current diffusion layer, and the current diffusion layer is arranged between the nanoporous layer and the first waveguide layer.

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

[0024] Optionally, the shape of the orthographic projection area of ​​the first through hole on the substrate layer is circular, elliptical or polygonal.

[0025] Optionally, the outer boundary shape of the orthographic projection area of ​​the whispering gallery microcavity on the substrate layer is an ellipse, and when N is equal to 1, the orthographic projection of the first through hole on the substrate layer covers one focus of the ellipse; or, the outer boundary shape of the orthographic projection area of ​​the whispering gallery microcavity on the substrate layer is a circle, and when N is equal to 1, the orthographic projection of the first through hole on the substrate layer is located inside the circle and has a gap with the center of the circular area.

[0026] In a second aspect, the present application provides a method for preparing a semiconductor laser, comprising:

[0027] Obtaining a substrate layer;

[0028] Based on the substrate layer, a first restriction layer, an active layer and a second restriction layer are stacked in sequence, 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, where N is a positive integer greater than or equal to 1, wherein 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 through hole on the substrate layer is the 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;

[0029] forming a first electrode on the substrate layer in ohmic contact with the first confinement layer;

[0030] 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.

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

[0032] The semiconductor laser and its preparation method provided by the present application, the present application arranges a first through hole in the active layer of the whispering gallery microcavity to destroy the isotropy of the active layer, thereby forming a resonant cavity structure with an asymmetric phase shift position, injects current into the whispering gallery microcavity through the first electrode and the second electrode, and the injected electrons and holes recombine in the active layer to release energy and generate spontaneous radiation. When the photons generated by the spontaneous radiation are reflected multiple times in the asymmetric resonant cavity, the asymmetry of the phase shift position will cause the loss, gain and other characteristics of the light field modes propagating in different directions in the cavity to differ, so that the light field mode in a certain direction is more likely to meet the conditions of laser oscillation, thereby realizing unidirectional laser emission.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0035] Figure 1 A partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of the present application;

[0036] Figure 2 A schematic projection diagram of a semiconductor laser provided in an embodiment of the present application;

[0037] Figure 3 A schematic projection diagram of a semiconductor laser provided in an embodiment of the present application;

[0038] Figure 4 A partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of the present application;

[0039] Figure 5 A partial cross-sectional schematic diagram of a semiconductor laser provided in an embodiment of the present application;

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

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

[0042] Figure 8This is a flow chart of the method for preparing a semiconductor laser in an embodiment of the present application;

[0043] Fig. 9 A cross-sectional view of a semiconductor laser provided in an embodiment of the present application;

[0044] Fig.10 A top cross-sectional view of a semiconductor laser provided in an embodiment of the present application;

[0045] Fig.11 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application;

[0046] Fig.12 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application;

[0047] Fig.13 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application;

[0048] Fig.14 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application;

[0049] Fig.15 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application;

[0050] Fig.16 A step diagram of a method for preparing a semiconductor laser provided in an embodiment of the present application. DETAILED DESCRIPTION

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

[0052] Various structural schematic diagrams according to embodiments of the present application are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0053] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. For example, the first value and the second value are only used to distinguish different values, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0054] It should be noted that, in this application, words such as "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 interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0055] In the present application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" or similar expressions refers 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, c can be single or multiple.

[0056] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intervening layer / element therebetween. Additionally, if a layer / element is "on" another layer / element in one orientation, the layer / element may be "below" the other layer / element when the orientation is reversed. In the context of the present disclosure, similar or identical components may be denoted by the same or similar reference numerals.

[0057] In order to better understand the above-mentioned technical scheme, the above-mentioned technical scheme will be described in detail below in combination with specific implementation methods. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical scheme of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present 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 is usually composed of a disk-shaped dielectric material. The microdisk mainly relies on the total reflection of the curved interface of the microdisk to form cavity confinement. When light propagates in the microdisk in the whispering gallery mode along the circumferential direction, it is totally reflected on the inner wall of the microdisk and thus confined in the microdisk. When the optical path of light propagating in the microdisk meets certain conditions, resonance is formed and laser is generated. Microdisk lasers have become a hot topic of research in recent years due to their small size and low threshold current.

[0059] The microdisk structure can effectively enhance the light field intensity of the laser resonant cavity, thereby improving the performance of the laser. However, microdisk lasers face two main problems:

[0060] First, due to the total internal reflection of the whispering gallery mode (WGM) microdisk cavity, most of the light field is confined inside the microdisk, and due to the isotropy of the microdisk, the emitted weak laser is evenly distributed in all directions, that is, the emission characteristics of the laser in all directions (such as intensity, frequency, etc.) are basically the same. This characteristic will limit 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 just adding electrical contact on the basis of optical pumping, the metal layer in the microdisk structure may introduce additional reflection and absorption, and the bottom cutting current of the traditional microdisk laser can only be injected from the narrow bottom pillar, the current is difficult to inject effectively and the heat dissipation becomes worse, so the difficulty of electrically injected laser emission increases sharply.

[0062] In view of this, the present application provides a semiconductor laser, please refer to Figure 1 , Figure 1 1 is a schematic diagram of the structure of a semiconductor laser in an embodiment of the present 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. 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 which are sequentially stacked on the 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 lower than that of the active layer 1022. The first confinement layer 1021 and the second confinement layer 1023 have lower refractive indices than the active layer 1022, which is conducive to confining light in the active layer 1022.

[0064] The active layer 1022 is provided with N first through holes 1024 along a direction perpendicular to the substrate layer 101, 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 through hole 1024 on the substrate layer 101 is the second center point. When N is equal to 1, the first center point and the second center point do not overlap each other. When N is greater than or equal to 2, the second center points corresponding to any two first through holes 1024 are asymmetrically arranged relative to the first center point. The first electrode 103 is arranged on the substrate layer 101 and is in ohmic contact with the first confinement layer 1021; the second electrode 104 is arranged on a 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 the embodiment of the present application, by setting N asymmetric first through holes 1024 in the active layer 1022 of the whispering gallery microcavity 102, destroys the rotational symmetry of the active layer 1022, so that the whispering gallery microcavity 102 as a whole forms 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, and the injected electrons and holes recombine in the active layer 1022 to release energy and generate spontaneous radiation. When the photons generated by the spontaneous radiation are reflected multiple times in the asymmetric resonant cavity, the asymmetry of the phase shift position will cause the light field modes propagating in different directions to have differences in the loss, gain and other characteristics in the cavity, so that the light field mode in a certain direction is more likely to meet the conditions for laser oscillation, thereby realizing unidirectional laser emission.

[0066] In the semiconductor laser provided in the embodiment of the present application, the whispering gallery microcavity 102 may adopt a cylindrical structure, an elliptical columnar structure or a square columnar structure. In an example provided in the present application, the whispering gallery microcavity 102 adopts a cylindrical structure, and the outer boundary shape of the orthographic projection area of ​​the whispering gallery microcavity 102 on the substrate layer 101 is a circle. When N is equal to 1, the orthographic projection of the first through hole 1024 on the substrate layer 101 is located in the circle and has a gap with the center of the circle.

[0067] The whispering gallery microcavity 102 is a multi-layer 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 columnar 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 columnar 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, the whispering gallery microcavity 102 adopts a cylindrical structure. Figure 2 As shown, the first outer boundary 201 of the orthographic projection of the whispering gallery microcavity 102 on the substrate layer 101 forms a circle as shown in FIG. a, FIG. b, FIG. c and FIG. d, and the circular area enclosed by the first outer boundary 201 has a first center 202. The second outer boundary 203 of the orthographic projection of the first through hole 1024 on the substrate layer 101 forms a circle as shown in FIG. a, FIG. b or FIG. c, and the circular area enclosed by the second outer boundary 203 has a second center 204. When N is equal to 1, there is a gap h between the first center 202 and the second center 204 as shown in FIG. a.

[0069] When N is greater than or equal to 2, for example, when N is equal to 2, the circular area surrounded by the two second outer boundaries 203 is asymmetrically arranged relative to the first circle center 202 as shown in FIG. Figure 2 As shown, when the first through holes 1024 are 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 can be understood that when the two first through holes 1024 are circular holes with different diameters, the diameters of the circular areas enclosed by the two second outer boundaries 203 are also different, and the corresponding two second circle centers 204 can be symmetrically arranged relative to the first circle center 202. This is because, when the diameters of the circular areas enclosed by the two second outer boundaries 203 are different, even if the corresponding two second circle centers 204 are symmetrically arranged relative to the first circle center 202, the orthographic projection of the active layer 1022 on the substrate layer 101 is non-centrally symmetrical, so that the whispering gallery microcavity 102 is a resonant cavity structure with an asymmetric phase shift position, which can achieve unidirectional laser emission.

[0071] For example, N is equal to 3, and Figure 2 As shown, when the sizes of the three first through holes 1024 are different, the three second circles 203 with different diameters can be arranged unevenly in the circumferential direction relative to the first circle center 202 as shown in Figure c, or can be arranged evenly in the circumferential direction relative to the first circle center 202.

[0072] It is understandable that the first through hole 1024 may also be an elliptical hole, a polygonal hole, such as a pentagonal hole. Figure 2 As shown in FIG. 2 , the orthographic projection 205 of the first through hole 1024 on the substrate layer 101 is an ellipse or a polygon as shown in FIG.

[0073] In some examples, the whispering gallery microcavity 102 has an elliptical columnar structure, such as Figure 3 As shown, the shape of the outer boundary of the orthographic projection area 301 of the whispering gallery microcavity 102 on the substrate layer 101 is an ellipse as shown in Figure a or Figure b, and the ellipse has a first focus 302 and a second focus 303. The orthographic projection 304 of the first through hole 1024 on the substrate layer 101 covers the first focus 302 of the ellipse as shown in Figure a, or covers the second focus 303 of the ellipse as shown in Figure b. It can be understood that the orthographic projection area of ​​the active layer 1022 on the substrate layer 101 is an elliptical area whose outer boundary coincides with the outer boundary of the orthographic projection area 301 of the whispering gallery microcavity 102 on the substrate layer 101.

[0074] Still Figure 3 As shown, when the orthographic projection 304 of the first through hole 1024 on the substrate layer 101 is a circle as shown in FIG. a, the value interval of the diameter D1 of the circle is [0.1H, H); or when the orthographic projection 304 of the first through hole 1024 on the substrate layer 101 is a regular polygon as shown in FIG. b, the value interval of the diameter D2 of the circumscribed circle of the regular polygon is [0.1H, H), wherein H is the length value of the major axis of the ellipse formed by the outer boundary of the orthographic projection area 301 of the whispering gallery microcavity 102 on the substrate layer 101.

[0075] The example of the above-mentioned semiconductor laser provided in the embodiment of the present application can suppress the high-order modes of the semiconductor laser, reduce the laser threshold of the fundamental mode, increase the loss of the high-order mode, and effectively regulate the number of modes by introducing a focal single-point hole and an asymmetric central multi-point hole. At the same time, the asymmetric hole design destroys the isotropy of the whispering gallery microcavity 102, and the direction of the emitted laser is no longer uniform in all directions. The laser intensity is maximum only at a specific angle, thereby realizing the directional emission of laser by the whispering gallery microcavity 102, thereby improving the light collection efficiency, which is crucial for promoting the coupling of optoelectronic devices.

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

[0077] It can be understood that when the third through hole 501, the first through hole 1024 and the second through hole 401 are connected in sequence, a microhole penetrating the whispering gallery microcavity 102 is formed. Theoretically, the active layer 1022, as the main structural layer of the semiconductor laser, only needs to set the first through hole 1024 to destroy the isotropy of the active layer 1022 to achieve unidirectional output of the laser. From the processing technology point of view, the cost of processing only the first through hole 1024 is relatively higher and the process is relatively complicated. The process of processing the microhole penetrating the whispering gallery microcavity 102 at one time is relatively simple, the easiest to achieve, and the cost is lower.

[0078] In some optional embodiments, such as Figure 6 As shown, the first limiting layer 1021 includes a nanoporous layer 601 and a first waveguide layer 602 which are sequentially stacked on the substrate layer 101, and the refractive indexes of the nanoporous layer 601, the first waveguide layer 602 and the active layer 1022 are increased in sequence; 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, and can limit the light field generated by the active layer 1022 to propagate in a specific direction, thereby reducing the scattering and loss of light in other areas, thereby improving the light utilization efficiency and output power.

[0079] The second limiting layer 1023 includes a second waveguide layer 603 and a contact layer 604 which are sequentially stacked on the active layer 1022, and the refractive indexes 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 is the main light-emitting structure of the whispering gallery microcavity 102, and can adopt a quantum well structure or a quantum dot structure. For example, the active layer 1022 adopting the quantum well structure includes M barrier layers and M-1 potential well layers stacked in layers, and the M barrier layers and the M-1 potential well layers are alternately arranged between the first waveguide layer 602 and the second waveguide layer 603; the barrier layer includes Al x1 Ga (1-x1) N material, the potential well layer includes 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. 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 in sequence. 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 increase in sequence.

[0081] In some optional implementations, the value range of x1 is 0.1 to 0.5 nanometers. For example, the value of x1 may be 0.3 nanometers, 0.35 nanometers, 0.4 nanometers, 0.45 nanometers or 0.5 nanometers.

[0082] In the semiconductor laser provided in the embodiment of the present application, the first electrode 103 comprises a P-type doped electrode material; the first waveguide layer 602 comprises 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) N material, wherein x4 is greater than x3 and less than 1.

[0083] The nanoporous layer 601 may be made of P-type doped Al x4 Ga (1-x4) The nanoporous layer 601 is made by introducing nanopores into the N material through electrochemical corrosion. The nanoporous layer 601 can increase the interface and channel inside the semiconductor material, provide more transmission paths for carriers (electrons and holes), reduce the transmission resistance of carriers, and thus improve the injection efficiency and mobility of carriers. Since x1, x2, x3 and x4 increase successively, the proportion of aluminum in the materials of the nanoporous layer 601, the first waveguide layer 602 and the barrier layer decreases successively, and thus the refractive index decreases successively, which is conducive to sending light into the active layer 1022. The porous structure of the nanoporous layer 601 further reduces the effective refractive index by introducing nanopores, thereby forming a larger refractive index difference with the active layer 1022, helping electrons and holes to be more effectively injected into the active layer 1022, increasing the carrier concentration in the active layer 1022, and thus improving the luminous efficiency of the semiconductor laser. The nanoporous layer 601 can also limit the light field mode near the active layer 1022, and since no undercut is required, the heat dissipation efficiency is higher.

[0084] The porous structure of the nanoporous layer 601 cooperates with the structure of the first through hole 1024 to further confine the light field to the active layer 1022, increase the overlap coefficient, suppress the high-order mode, and destroy the symmetry, thereby achieving low-threshold electrical injection and unidirectional high-power laser output. Compared with the traditional laser solution, it has a simple system, high stability, and does not require secondary epitaxy and complex active and passive integration technology, and has important application value in optical communication, optical sensing, photoelectric detection, and photon computing.

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

[0086] The contact layer 604 is used to stably, evenly and efficiently inject current into the active layer 1022 of the whispering gallery microcavity 102, reduce the resistance loss at the interface between the second electrode 104 and the whispering gallery microcavity 102, improve the current transmission efficiency, and thus improve the overall performance and photoelectric conversion efficiency of the semiconductor laser, and ensure the normal operation and consistency of the output characteristics of the semiconductor laser. On the other hand, the contact layer 604 can also protect the internal structure of the whispering gallery microcavity 102: prevent the semiconductor material inside the semiconductor laser from coming into contact with the external environment and undergoing chemical reactions such as oxidation, thereby improving the stability and service life 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, which limits 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 utilization efficiency and output power of light, and further improving the luminous efficiency of the semiconductor laser.

[0088] In some optional embodiments, 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) N material, where x6 is greater than x3 and less than x4. x6 is between x3 and x4, so the refractive index of the current diffusion layer 701 is greater than the nanoporous layer 601 and less than the first waveguide layer 602, ensuring that light is sent 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 can make the current diffuse evenly in the active layer 1022 laterally, avoid the current concentration in the local area, thereby improving the overall luminous efficiency of the active layer 1022 and reducing the light power loss and uneven light spot caused by uneven current.

[0090] Based on the same inventive concept, the present application also provides a method for preparing a semiconductor laser. Figure 8 As shown, the method includes:

[0091] S801, obtaining a 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 stacked in sequence, and N first through holes 1024 are formed on the active layer 1022 along a direction perpendicular to the substrate layer 101 to obtain a whispering gallery microcavity 102, where N is a positive integer greater than or equal to 1, wherein 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 through hole 1024 on the substrate layer 101 is the 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 1024 are asymmetrically arranged relative to the first center point;

[0093] S803, forming a first electrode 103 on the substrate layer 101 in ohmic contact with the first restriction layer 1021;

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

[0095] The method for preparing a semiconductor laser provided in the embodiment of the present application destroys the isotropy of the whispering gallery microcavity 102 through an asymmetric hole (i.e., the first through hole 1024) design, so that the direction of the emitted laser is not uniform in all directions, and the laser intensity is only maximum at a certain angle, which solves the problem that the laser of the whispering gallery microcavity 102 cannot be emitted in a directional manner. The refractive index of the first confinement layer 1021 is less than the refractive index of the active layer 1022, and the refractive index of the second confinement layer 1023 is less than the refractive index of the active layer 1022. The first confinement layer 1021 and the second confinement layer 1023 have a lower refractive index than the active layer 1022, which is conducive to confining light to the active layer 1022.

[0096] The following specific embodiments are used to describe in detail the technical solution of the present application and how the technical solution of the present application solves the above technical problems. The following specific embodiments can be implemented independently or in combination with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

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

[0098] The whispering gallery microcavity epitaxially grown on the substrate 901, the P-type electrode 902 and the N-type electrode 903 for introducing current, the outer contour of the whispering gallery microcavity is a cylindrical structure, such as Fig. 9As shown, the materials of the epitaxial structure layer include a 700nm NP-AlGaN nanoporous layer 904, a 350nm p-Al 0.6 Ga 0.4 N material current diffusion layer 905, 150nm p-Al 0.55 Ga 0.45 The first waveguide layer 906 is made of N, 4 layers of 9nm Al 0.45 Ga 0.55 The barrier layer 907 made of N material and 3 layers of 2nm Al 0.55 Ga 0.45 The active layer is composed of the potential well layer 908 of N material and the 100nm n-Al 0.55 Ga 0.45 N second waveguide layer 909 and a contact layer 910 made of 100nm n-GaN material.

[0099] It should be noted that the full name of NP-AlGaN is nanoporous Aluminum Gallium Nitride, and its Chinese name is nanoporous aluminum gallium nitride. 700nmNP-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 parameters of Al and Ga. The NP-AlGaN used in the nanoporous layer 904 of the present application embodiment can adopt P-type doped nanoporous aluminum gallium nitride, for example, it can be 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 Fig.10 As shown, a hole 1001 is etched inside the whispering gallery microcavity, and the hole 1001 is used to destroy the rotational symmetry of the whispering gallery microcavity to achieve directional emission of the laser. A P-type electrode 902 is disposed on a substrate 901 and surrounds a nanoporous layer 904 of the whispering gallery microcavity, and an N-type electrode 903 is disposed on a 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, only a cylindrical whispering gallery microcavity with an eccentrically set hole 1001 is used as an example for explanation. Fig. 9 The arrangement relationship between the epitaxial structure layers of the whispering gallery microcavity is merely an example, and the specific thickness of each epitaxial structure layer is not limited.

[0102] In order to prepare the single-mode unidirectional ultraviolet microcavity laser in this embodiment, this embodiment provides a method for preparing a single-mode laser microcavity laser, comprising the following steps:

[0103] S1, such as Fig.11 As shown, an AlN (aluminum nitride) substrate 1101 is obtained, and an epitaxial structure layer 1102 of a whispering gallery microcavity is 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, and photoresist is spin-coated on the semiconductor material and baked at a high temperature to obtain the first photoresist layer 1103 shown in Figure b.

[0104] S2, such as Fig.12 As shown, a laser is used to expose a predetermined shape of the first photoresist layer 1103, and the exposed part is washed away to form a first window 1201 as shown in Figure a and Figure b, and the epitaxial structure layer 1102 is exposed to the first window 1201. The figure enclosed by the outer boundary of the first window 1201 is a first circle, and the figure enclosed by the inner boundary of the first window 1201 is 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 first circle.

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

[0106] S4, such as Fig.14 As shown, acetone is used to clean and remove the unexposed portion of the first photoresist layer 1103. The metal of the evaporated 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, and the portion of the epitaxial structure layer 1102 not covered by the metal mask layer 1401 is exposed.

[0107] S5, such as Fig.15As shown, the portion of the epitaxial structure layer 1102 not covered by the metal mask layer 1401 is etched through an etching process to form a whispering gallery microcavity 1501 as shown in FIG. The whispering gallery microcavity 1501 has a microhole 1502 penetrating the whispering gallery microcavity 1501 in a direction perpendicular to the substrate 1101, and the substrate is exposed in the microhole 1502. The portion of the epitaxial structure layer 1102 that is removed is etched because it is not protected by the metal mask layer 1401.

[0108] S6, such as Fig.16 As shown, the metal mask layer 1401 is washed away, so that the side of the whispering gallery microcavity 1501 away from the substrate 1101 is exposed as shown in Figure a, and the P-type electrode 1601 shown in Figures b and c is formed on the substrate 1101, and the N-type electrode 1602 shown in Figures b and c is formed on the side of the whispering gallery microcavity 1501 away from the substrate 1101, that is, a unidirectional ultraviolet microcavity laser is obtained. 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 embodiment aims at the high threshold problem of the existing microcavity laser. By forming microholes, the cross section of the whispering gallery microcavity is made non-rotationally symmetrical. The isotropy of the whispering gallery microcavity is destroyed, the direction of the emitted laser is no longer uniform in all directions, and the laser intensity is only maximum at a certain angle, so that the waveguide laser mode can be emitted more efficiently in the whispering gallery cavity, which is conducive to improving the coupling output efficiency and the output optical power. Its preparation process is simple, the cost is low, and it has a small size and high power. The whispering gallery microcavity structure enables the laser to work efficiently at a smaller size, which is convenient for integration and miniaturization and can be adapted to a variety of application scenarios.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0111] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Claims

1. A semiconductor laser, characterized in that: include: substrate layer; A whispering gallery microcavity is arranged on one side of the substrate layer, the whispering gallery microcavity comprises a first restriction layer, an active layer and a second restriction layer which are sequentially stacked on the substrate layer, the active layer is provided with N first through holes along a direction perpendicular to the substrate layer, 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, the geometric center point of the orthographic projection area of ​​the first through hole on the substrate layer is the second center point, 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 of the first through holes are asymmetrically arranged relative to the first center point; A first electrode, disposed on the substrate layer and in ohmic contact with the first confinement layer; The second electrode is disposed on a side of the second confinement layer away from the active layer and is in ohmic contact with the second confinement layer.

2. The semiconductor laser according to claim 1, characterized in that The first restriction layer is provided with N second through holes along a direction perpendicular to the substrate layer, each of the second through holes is connected to one of the first through holes, and / or the second restriction layer is provided with N third through holes along a direction perpendicular to the substrate layer, each of the third through holes is connected to one of the first through holes.

3. The semiconductor laser according to claim 1, characterized in that The first confinement layer comprises a nanoporous layer and a first waveguide layer stacked in sequence on the substrate layer, and the refractive indexes of the nanoporous layer, the first waveguide layer and the active layer increase in sequence; The second confinement layer comprises a second waveguide layer and a contact layer which are sequentially stacked on the active layer, and the refractive indexes of the contact layer, the second waveguide layer and the active layer are increased in sequence; 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 according to claim 3, characterized in that The active layer includes M barrier layers and M-1 potential well layers stacked in layers, wherein the M barrier layers and the M-1 potential well layers are 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) 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 according to claim 4, characterized in that The first electrode comprises a P-type 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 includes 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-type doped electrode material; The second waveguide layer includes N-type doped Al x5 Ga (1-x5) N material, wherein x5 is greater than x1 and less than 1; The contact layer includes N-type doped gallium nitride material.

6. The semiconductor laser according to claim 5, characterized in that The first confinement layer further includes a current diffusion layer disposed between the nanoporous layer and the first waveguide layer.

7. The semiconductor laser according to claim 6, characterized in that The current diffusion layer includes P-type doped Al x6 Ga (1-x6) N material, wherein x6 is greater than x3 and less than x4.

8. The semiconductor laser according to claim 1, wherein The shape of the orthographic projection area of ​​the first through hole on the substrate layer is circular, elliptical or polygonal.

9. The semiconductor laser according to claim 1, characterized in that The outer boundary shape of the orthographic projection area of ​​the whispering gallery microcavity on the substrate layer is an ellipse, and when N is equal to 1, the orthographic projection of the first through hole on the substrate layer covers a focus of the ellipse; or, the outer boundary shape of the orthographic projection area of ​​the whispering gallery microcavity on the substrate layer is a circle, and when N is equal to 1, the orthographic projection of the first through hole on the substrate layer is located within the circle and has a gap with the center of the circular area.

10. A method for preparing a semiconductor laser, characterized in that: include: Obtaining a substrate layer; Based on the substrate layer, a first restriction layer, an active layer and a second restriction layer are stacked in sequence, 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, where N is a positive integer greater than or equal to 1, wherein 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 through hole on the substrate layer is the 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 of the first through holes are asymmetrically arranged relative to the first center point; forming a first electrode on the substrate layer in ohmic contact with the first confinement 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.

Images