Laser epitaxial structure and vertical cavity surface emitting laser preparation method

Abstract

The present application provides a laser epitaxial structure and a method for preparing a vertical cavity surface emitting laser, which relate to the field of laser technology and include a substrate, and a bottom N-type distributed Bragg reflector, a quantum well, a P-type distributed Bragg reflector, a tunnel junction, and a top N-type distributed Bragg reflector stacked in sequence on the substrate, or a bottom N-type distributed Bragg reflector, a tunnel junction, a P-type distributed Bragg reflector, a quantum well, and a top N-type distributed Bragg reflector stacked in sequence on the substrate. Thus, by adding a tunnel junction to the laser epitaxial structure, a device structure of dual N-type distributed Bragg reflectors can be formed, and then a device structure of dual N-type metal layers can be formed, so that the performance of the device in terms of carrier mobility and overall electrical efficiency is improved, and at the same time, the heat dissipation of the device can be improved.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a laser epitaxial structure and a method for preparing a vertical cavity surface emitting laser. Background Art

[0002] A vertical-cavity surface-emitting laser (VCSEL) is a laser whose light emission direction is perpendicular to the surface of the resonant cavity. It has the advantages of low threshold current, small divergence angle, circular symmetry of the light spot, and easy two-dimensional integration. It is currently widely used in optical interconnection, optical storage, optical communication and other fields.

[0003] Existing VCSEL devices typically include an N-type Bragg reflector, a quantum well, and a P-type Bragg reflector stacked in sequence on a substrate. Since the top layer is a P-type Bragg reflector, only a P-type contact layer can be set on the P-type Bragg reflector. However, P-type materials are often inferior to N-type materials in terms of carrier mobility and overall electrical efficiency, thus limiting the performance of VCSEL devices. Summary of the Invention

[0004] The purpose of this application is to address the deficiencies in the above-mentioned prior art and provide a laser epitaxial structure and a method for preparing a vertical cavity surface emitting laser, so as to solve the problem that the performance of the existing laser is limited due to P-type materials.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows:

[0006] In one aspect of an embodiment of the present application, a laser epitaxial structure is provided, comprising a substrate, and a bottom N-type distributed Bragg reflector, a quantum well, a P-type distributed Bragg reflector, a tunnel junction, and a top N-type distributed Bragg reflector sequentially stacked on the substrate, or a bottom N-type distributed Bragg reflector, a tunnel junction, a P-type distributed Bragg reflector, a quantum well, and a top N-type distributed Bragg reflector sequentially stacked on the substrate;

[0007] An N-type contact layer and a top N-type metal layer are sequentially stacked on the side of the top N-type distributed Bragg reflector away from the quantum well, and a bottom N-type metal layer is arranged on the side of the substrate away from the quantum well.

[0008] Optionally, the top N-type metal layer is a Cr layer and an Ag layer sequentially stacked on the N-type contact layer.

[0009] Optionally, the bottom N-type metal layer is an Au layer and a Ge layer sequentially stacked on the substrate, or the bottom N-type metal layer is an Ag layer and a Ge layer sequentially stacked on the substrate.

[0010] Optionally, the tunnel junction includes a stacked P-type semiconductor layer and an N-type semiconductor layer, and the P-type semiconductor layer is located between the N-type semiconductor layer and the P-type distributed Bragg reflector.

[0011] Optionally, the N-type semiconductor layer is an AlGaAs layer doped with Te, and the P-type semiconductor layer is an AlGaAs layer doped with C.

[0012] Optionally, an oxidation confinement layer is further provided on a side of the quantum well close to the top N-type distributed Bragg reflector.

[0013] Optionally, a buffer layer is further provided between the substrate and the bottom N-type distributed Bragg reflector.

[0014] Optionally, the buffer layer is an N-type buffer layer.

[0015] Another aspect of the embodiments of the present application provides a method for preparing a vertical cavity surface emitting laser, which uses any of the above-mentioned laser epitaxial structures to prepare the vertical cavity surface emitting laser.

[0016] The beneficial effects of this application include:

[0017] The present application provides a laser epitaxial structure and a method for preparing a vertical cavity surface emitting laser, comprising a substrate, and a bottom N-type distributed Bragg reflector, a quantum well, a P-type distributed Bragg reflector, a tunnel junction, and a top N-type distributed Bragg reflector stacked in sequence on the substrate, or a bottom N-type distributed Bragg reflector, a tunnel junction, a P-type distributed Bragg reflector, a quantum well, and a top N-type distributed Bragg reflector stacked in sequence on the substrate; an N-type contact layer and a top N-type metal layer are stacked in sequence on the side of the top N-type distributed Bragg reflector facing away from the quantum well, and a bottom N-type metal layer is provided on the side of the substrate facing away from the quantum well. Thus, by adding a tunnel junction to the laser epitaxial structure, a device structure with dual N-type distributed Bragg reflectors can be formed, and then a device structure with dual N-type metal layers can be formed, so that the device performance in terms of carrier mobility and overall electrical efficiency is improved, while also improving the heat dissipation of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0019] Figure 1A schematic structural diagram of a laser epitaxial structure provided in an embodiment of the present application;

[0020] Figure 2 A schematic structural diagram of another laser epitaxial structure provided in an embodiment of the present application;

[0021] Figure 3 A schematic structural diagram of a top metal layer provided in an embodiment of the present application;

[0022] Figure 4 This is one of the structural schematic diagrams of a bottom metal layer provided in an embodiment of the present application;

[0023] Figure 5 This is a second structural schematic diagram of a bottom metal layer provided in an embodiment of the present application.

[0024] Icon: 110 - substrate; 120 - buffer layer; 130 - bottom N-DBR; 140 - MQW; 150 - oxidation restriction layer; 160 - P-DBR; 170 - tunnel junction; 180 - top N-DBR; 190 - N-type contact layer; 200 - top N-type metal layer; 210 - bottom N-type metal layer. DETAILED DESCRIPTION

[0025] The embodiments set forth below represent the information necessary to enable those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically set forth herein. It should be understood that these concepts and applications fall within the scope of the present disclosure and the appended claims.

[0026] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of this disclosure, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0027] It should be understood that when an element (such as a layer, region or substrate) is referred to as being "on another element" or "extending onto another element", it may be directly on the other element or directly extending onto the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly on another element" or "extending directly onto another element", there are no intervening elements. Similarly, it should be understood that when an element (such as a layer, region or substrate) is referred to as being "above another element" or "extending over another element", it may be directly on the other element or directly extending over the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly on another element" or "extending directly over another element", there are no intervening elements. It should also be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0028] Relative terms, such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical", may be used herein to describe the relationship of one element, layer or region to another element, layer or region, as illustrated in the figures. It should be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0029] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It should also be understood that when used herein, the term "comprising" indicates the presence of the recited features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. It should also be understood that the terms used herein should be interpreted as having the same meaning as they have in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense unless otherwise explicitly defined herein.

[0031] In one aspect of an embodiment of the present application, a laser epitaxial structure is provided. By adding a tunnel junction to the laser epitaxial structure, an N-type distributed Bragg reflector can be set on the P-type distributed Bragg reflector, and then an N-type contact layer and an N-type metal layer are set on the N-type distributed Bragg reflector. Ohmic contact can be formed in the process, thereby improving the performance of the device in terms of carrier mobility and overall electrical efficiency, and at the same time, improving the heat dissipation of the device.

[0032] When introducing the tunnel junction into the laser epitaxial structure, the tunnel junction can be set accordingly according to the position of the P-type distributed Bragg reflector, thereby forming different device structures respectively. The embodiments of the present application will be further described below in conjunction with the accompanying drawings.

[0033] In one embodiment, see Figure 1 As shown, a laser epitaxial structure is provided, which specifically includes a substrate 110, a bottom N-type metal layer 210 is set on the back side of the substrate 110, a bottom N-type distributed Bragg reflector (bottom N-DBR130) is set on the front side of the substrate 110, a quantum well (MQW140) is set on the bottom N-type distributed Bragg reflector, and then a P-type distributed Bragg reflector (P-DBR160) is set on the quantum well, and a stacked tunnel junction 170 and a top N-type distributed Bragg reflector (top N-DBR180) are sequentially set on the P-type distributed Bragg reflector. In this way, the tunnel junction 170 can be used to form a top N-DBR180 on the P-DBR160. On the one hand, after the top N-DBR180 is formed, the doping concentration of the top N-DBR180 is lower than that of the P-DBR160 (the doping concentration of the P-DBR160 is difficult to reach high doping, for example, it is difficult to reach 3-5E19cm -3 ) has better concentration control and electron mobility; on the other hand, an N-type contact layer 190 and a top N-type metal layer 200 can be formed on the top N-DBR 180, thereby facilitating the laser epitaxial structure to form an ohmic contact by using the top N-type metal layer 200 in conjunction with the N-type contact layer 190 during the manufacturing process, thereby improving the performance of the device in terms of carrier mobility and overall electrical efficiency, and at the same time, improving the heat dissipation of the device.

[0034] In another embodiment, see Figure 2As shown, a laser epitaxial structure is provided, specifically including a substrate 110. A P-type distributed Bragg reflector (P-DBR160), a quantum well (MQW140), and a top N-type distributed Bragg reflector (top N-DBR180) are sequentially arranged above the front surface of the substrate 110. Then, an N-type contact layer 190 and a top N-type metal layer 200 are sequentially arranged on the top N-DBR180. In order to convert the P-DBR160 to N-type, a tunnel junction 170 can be introduced between the P-DBR160 and the substrate 110. Then, a bottom N-DBR130 is arranged between the tunnel junction 170 and the substrate 110, so that an N-type metal layer can be arranged on the back surface of the substrate 110. In this way, on the one hand, the bottom N-DBR130 is more doped than the P-DBR160 (the doping concentration of the P-DBR160 is difficult to reach a high level, for example, it is difficult to reach 3-5E19cm -3 ) has better concentration control and electron mobility; on the other hand, the bottom N-DBR 130 can be used to form a bottom N-type metal layer 210 on the back side of the substrate 110, thereby improving the performance of the device in terms of carrier mobility and overall electrical efficiency, and at the same time, it can also improve the heat dissipation of the device.

[0035] In summary, the present application forms a dual N-DBR structure by introducing a tunnel junction 170. Since N-DBRs are easier to control doping concentrations and have better electron mobility than P-DBRs 160, device performance can be effectively improved. Furthermore, N-type electrodes can be formed at both the top and bottom of the device. This makes it easier to fabricate N-type electrodes than P-type electrodes, which can help improve device yield and reduce costs. Furthermore, the dual N-type electrodes enable the top N-type metal layer 200 and the bottom N-type metal layer 210 of the device to be fabricated in the same process step, simplifying the process and reducing costs.

[0036] In addition, the laser epitaxial structure in this application can be epitaxially grown only once, and after the epitaxial growth is completed, it can be directly transferred to the manufacturing process to obtain the corresponding laser structure, such as a VCSEL device. For example:

[0037] See also Figure 1 , providing a substrate 110, and then sequentially epitaxially growing on the substrate 110 to obtain a stacked bottom N-DBR 130, MQW 140, P-DBR 160, tunnel junction 170, top N-DBR 180 and N-type contact layer 190, and then depositing a bottom N-type metal layer 210 and a top N-type metal layer 200 on the back side of the substrate 110 and the N-type contact layer 190, respectively.

[0038] See also Figure 2, providing a substrate 110, and then sequentially epitaxially growing on the substrate 110 to obtain a stacked bottom N-DBR 130, a tunnel junction 170, a P-DBR 160, an MQW 140, a top N-DBR 180 and an N-type contact layer 190, and then depositing a bottom N-type metal layer 210 and a top N-type metal layer 200 on the back side of the substrate 110 and the N-type contact layer 190, respectively.

[0039] In some embodiments, as Figure 3 As shown, the top N-type metal layer 200 is a Cr layer and an Ag layer sequentially stacked on the N-type contact layer 190 .

[0040] In some embodiments, as Figure 4 As shown, the bottom N-type metal layer 210 is an Au layer and a Ge layer sequentially stacked on the substrate 110. In some embodiments, the Au layer can be replaced with an Ag layer to form a Figure 5 As shown, the bottom N-type metal layer 210 is an Ag layer and a Ge layer sequentially stacked on the substrate 110. Thus, the Ag layer can achieve better electrical conductivity and heat dissipation capabilities while reducing costs. In some embodiments, the Ge layer can also be replaced by a Cr layer.

[0041] In some embodiments, the tunnel junction 170 may include a stacked P-type semiconductor layer and an N-type semiconductor layer. When applied to the above embodiment: Figure 1 As shown, the P-type semiconductor layer and the N-type semiconductor layer are located between the P-DBR 160 and the top N-DBR 180, and the P-type semiconductor layer is arranged close to one side of the P-DBR 160, and the N-type semiconductor layer is arranged close to one side of the top N-DBR 180. Thus, the purpose of forming the top N-DBR 180 on the P-DBR 160 can be achieved; Figure 2 As shown, the P-type semiconductor layer and the N-type semiconductor layer are located between the P-DBR 160 and the bottom N-DBR 130, and the P-type semiconductor layer is arranged close to one side of the P-DBR 160, and the N-type semiconductor layer is arranged close to one side of the bottom N-DBR 130. Thus, the purpose of converting the P-DBR 160 into the bottom N-DBR 130 can be achieved.

[0042] In some embodiments, the N-type semiconductor layer is an AlGaAs layer doped with Te, and the P-type semiconductor layer is an AlGaAs layer doped with C.

[0043] In some embodiments, in order to ensure that the laser produced by the laser epitaxial structure has a higher light output quality, an oxidation restriction layer 150 may be introduced into the laser epitaxial structure. Specifically:

[0044] See also Figure 1As shown, an oxidation restriction layer 150 with a high aluminum content is provided on the side of the quantum well facing away from the substrate 110. In other words, an oxidation restriction layer 150 with a high aluminum content is provided between the quantum well and the P-DBR 160. Therefore, during the manufacturing process, an oxidation aperture can be formed by lateral oxidation of the oxidation restriction layer 150, thereby limiting the distribution area of ​​the current and concentrating the current in the area of ​​the oxidation aperture. As a result, the threshold current of the device can be effectively reduced and the electro-optical conversion efficiency of the device can be improved.

[0045] In some embodiments, a buffer layer 120 is further provided between the substrate 110 and the bottom N-DBR 130. The buffer layer 120 can improve the matching defects between the substrate 110 and the bottom N-DBR 130 and improve the epitaxial quality of the bottom N-DBR 130. The buffer layer 120 may be an N-type buffer layer 120.

[0046] In some embodiments, both the bottom N-DBR 130 and the top N-DBR 180 can be a periodic structure composed of two materials with different refractive indices arranged alternately in an ABAB pattern, with the optical thickness of each layer being 1 / 4 of the central reflection wavelength. Similarly, the P-DBR 160 can also be configured appropriately based on this configuration, which will not be further described here.

[0047] In some embodiments, a quantum well can be used to generate a light beam by stimulated emission of radiation, which is then emitted as a high-brightness light beam through the high reflectivity of a distributed Bragg reflector, thereby forming a light spot in a target area. The quantum well can be a single quantum well or a multiple quantum well, which is not specifically limited in this application. It can enable the device to have a lower threshold, higher quantum efficiency, excellent temperature characteristics, and extremely narrow linewidth.

[0048] Another aspect of the present invention provides a method for fabricating a vertical cavity surface emitting laser (VCSEL), using any of the aforementioned laser epitaxial structures to fabricate a VCSEL. The resulting VCSEL device can achieve improved performance in terms of carrier mobility and overall electrical efficiency, while also improving heat dissipation.

[0049] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A laser epitaxial structure, characterized in that: The invention comprises a substrate, and a bottom N-type distributed Bragg reflector, a quantum well, a P-type distributed Bragg reflector, a tunnel junction and a top N-type distributed Bragg reflector sequentially stacked on the substrate, or a bottom N-type distributed Bragg reflector, a tunnel junction, a P-type distributed Bragg reflector, a quantum well and a top N-type distributed Bragg reflector sequentially stacked on the substrate; An N-type contact layer and a top N-type metal layer are sequentially stacked on the side of the top N-type distributed Bragg reflector away from the quantum well, and a bottom N-type metal layer is provided on the side of the substrate away from the quantum well.

2. The laser epitaxial structure according to claim 1, wherein: The top N-type metal layer is a Cr layer and an Ag layer sequentially stacked on the N-type contact layer.

3. The laser epitaxial structure according to claim 1, wherein: The bottom N-type metal layer is an Au layer and a Ge layer sequentially stacked on the substrate.

4. The laser epitaxial structure according to claim 1, wherein: The bottom N-type metal layer is an Ag layer and a Ge layer sequentially stacked on the substrate.

5. The laser epitaxial structure according to claim 1, wherein: The tunnel junction includes a stacked P-type semiconductor layer and an N-type semiconductor layer, and the P-type semiconductor layer is located between the N-type semiconductor layer and the P-type distributed Bragg reflector.

6. The laser epitaxial structure according to claim 5, wherein: The N-type semiconductor layer is an AlGaAs layer doped with Te, and the P-type semiconductor layer is an AlGaAs layer doped with C.

7. The laser epitaxial structure according to any one of claims 1 to 6, characterized in that: An oxidation confinement layer is further provided on a side of the quantum well close to the top N-type distributed Bragg reflector.

8. The laser epitaxial structure according to claim 1, wherein: A buffer layer is further provided between the substrate and the bottom N-type distributed Bragg reflector.

9. The laser epitaxial structure according to claim 8, wherein: The buffer layer is an N-type buffer layer.

10. A method for preparing a vertical cavity surface emitting laser, characterized in that: A vertical cavity surface emitting laser is prepared by using the laser epitaxial structure according to any one of claims 1 to 9.

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