A vertical cavity surface emitting laser

Abstract

A vertical cavity surface emitting laser (VCSEL) relates to the field of optoelectronics and includes a substrate and a bottom Bragg reflector layer, a multi-quantum well active layer, an oxide layer with a current-limiting aperture, and a top Bragg reflector layer stacked sequentially on the substrate. The top Bragg reflector layer includes a first Bragg reflector layer, an insertion layer, and a second Bragg reflector layer with a zinc diffusion region stacked sequentially. The insertion layer is used to block the zinc diffusion region from diffusing from the second Bragg reflector layer to the first Bragg reflector layer. The VCSEL's blocking effect, achieved by the insertion layer, helps precisely control the depth of zinc diffusion.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology, and in particular to a vertical cavity surface emitting laser. Background Art

[0002] A vertical-cavity surface-emitting laser (VCSEL), also known as a vertical-cavity surface-emitting laser, emits laser light perpendicular to the top surface, unlike edge-emitting lasers, which are typically manufactured using a cut-in-one chip process and emit laser light from the edge.

[0003] The vertical cavity surface emitting laser in the prior art generally achieves single-mode output by oxidizing the aperture during the preparation process. If you want to further optimize and limit the high-order transverse mode, you will generally add a zinc diffusion process during the preparation process. Specifically, on the top distributed Bragg reflector (DBR) of the oxidation-limited VCSEL, a zinc diffusion method is used to make a mode selection structure. By reducing the reflectivity of the DBR layer and increasing the absorption loss of free carriers, the high-order transverse mode is suppressed and the fundamental transverse mode lasing is achieved. At present, the above method has the following disadvantages: the depth (or concentration) of zinc diffusion depends on the temperature and time of the zinc diffusion process, and it cannot be precisely controlled. Summary of the Invention

[0004] The object of the present invention is to provide a vertical cavity surface emitting laser, which can play a blocking role through an insertion layer and help to accurately control the depth of zinc diffusion.

[0005] The embodiment of the present invention is achieved as follows:

[0006] An embodiment of the present invention provides a vertical cavity surface emitting laser, comprising a substrate and a bottom Bragg reflector layer, a multi-quantum well active layer, an oxide layer having a current limiting hole, and a top Bragg reflector layer stacked in sequence on the substrate, wherein the top Bragg reflector layer comprises a first Bragg reflector layer, an insertion layer, and a second Bragg reflector layer having a zinc diffusion region stacked in sequence, wherein the insertion layer is used to prevent the zinc diffusion region from diffusing along the direction from the second Bragg reflector layer to the first Bragg reflector layer.

[0007] As an implementable manner, the diffusion coefficient of the first Bragg reflector layer is the same as the diffusion coefficient of the second Bragg reflector layer, and the diffusion coefficient of the second Bragg reflector layer is different from the diffusion coefficient of the insertion layer.

[0008] As an practicable manner, the refractive index of light with a wavelength λ in the insertion layer is n, the thickness of the insertion layer is d, and the relationship is satisfied:

[0009] As an practicable manner, the material of the insertion layer is gallium arsenide, aluminum gallium arsenide, indium gallium phosphide, aluminum indium phosphide, aluminum gallium indium phosphide or indium gallium arsenide phosphide.

[0010] As an practicable manner, the second Bragg reflector layer has a light-through hole, the zinc diffusion region surrounds the outer edge of the light-through hole, and the current limiting hole corresponds to the light-through hole in a stacking direction.

[0011] As an implementable manner, the current limiting hole and the light-through hole are directly corresponding to each other in the stacking direction.

[0012] As an implementable manner, the aperture of the light-transmitting hole is smaller than the aperture of the current-limiting hole.

[0013] As an practicable manner, a first buffer layer is provided between the bottom Bragg reflector layer and the multi-quantum well active layer, a second buffer layer is provided between the multi-quantum well active layer and the oxide layer, and a third buffer layer is provided between the oxide layer and the first Bragg reflector layer.

[0014] As an practicable manner, a contact layer is provided on a side of the second Bragg reflector layer facing away from the insertion layer, and the bottom Bragg reflector layer and the multi-quantum well active layer form a step structure.

[0015] As an implementable manner, a first electrode is provided on a side of the contact layer facing away from the second Bragg reflector layer, and a second electrode is provided on a mesa of the bottom Bragg reflector layer close to the multi-quantum well active layer.

[0016] The beneficial effects of the embodiments of the present invention include:

[0017] The vertical cavity surface emitting laser (VCR) comprises a substrate, and a bottom Bragg reflector layer, a multi-quantum well active layer, an oxide layer having a current limiting aperture, and a top Bragg reflector layer stacked sequentially on the substrate. The top Bragg reflector layer comprises a first Bragg reflector layer, an insertion layer, and a second Bragg reflector layer having a zinc diffusion region. The insertion layer is configured to block the zinc diffusion region from diffusing from the second Bragg reflector layer to the first Bragg reflector layer. During zinc diffusion on the top Bragg reflector layer, zinc ions are first injected into the second Bragg reflector layer from the side of the second Bragg reflector layer facing away from the insertion layer at a specific diffusion rate, forming a zinc diffusion region. When the zinc ions reach the side of the insertion layer closer to the second Bragg reflector layer, the blocking effect of the insertion layer slows the zinc ion diffusion rate. This allows, in addition to controlling the temperature and time of the zinc diffusion process, the blocking effect of the insertion layer to control the zinc diffusion depth, thereby facilitating precise control of the zinc diffusion depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention 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 paying any creative work.

[0019] Figure 1 One of the structural schematic diagrams of the vertical cavity surface emitting laser provided by an embodiment of the present invention;

[0020] Figure 2 The second structural diagram of the vertical cavity surface emitting laser provided by an embodiment of the present invention;

[0021] Figure 3 This is the third structural schematic diagram of the vertical cavity surface emitting laser provided by an embodiment of the present invention.

[0022] Icon: 100-vertical cavity surface emitting laser; 110-substrate; 120-bottom Bragg reflector layer; 130-first buffer layer; 140-multi-quantum well active layer; 150-second buffer layer; 160-oxide layer; 161-current limiting hole; 170-third buffer layer; 180-top Bragg reflector layer; 181-first Bragg reflector layer; 182-insertion layer; 183-second Bragg reflector layer; 1831-zinc diffusion region; 1832-light-through hole; 190-contact layer; 200-first electrode; 210-second electrode. DETAILED DESCRIPTION

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 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.

[0029] Please refer to Figures 1 to 3 This embodiment provides a vertical cavity surface emitting laser (VCSEL) 100, comprising a substrate 110, and a bottom Bragg reflector layer 120, a multi-quantum well active layer 140, an oxide layer 160 having a current limiting aperture 161, and a top Bragg reflector layer 180, which are sequentially stacked on the substrate 110. The top Bragg reflector layer 180 comprises a first Bragg reflector layer 181, an insertion layer 182, and a second Bragg reflector layer 183 having a zinc diffusion region 1831, which are sequentially stacked. The insertion layer 182 is configured to block the diffusion of the zinc diffusion region 1831 from the second Bragg reflector layer 183 to the first Bragg reflector layer 181. The VCSEL 100 can precisely control the depth of zinc diffusion through the insertion layer 182, which acts as a barrier.

[0030] It should be noted that if Figure 1 As shown, the vertical cavity surface emitting laser 100 includes a substrate 110, a bottom Bragg reflector layer 120, a multi-quantum well active layer 140, an oxide layer 160 and a top Bragg reflector layer 180 stacked in sequence, wherein the oxide layer 160 has a current limiting hole 161 to guide and limit the flow of current through the current limiting hole 161, as shown in FIG. Figure 2 As shown, when the current flows through the oxide layer 160, it will be confined in the current limiting hole 161. In this way, a higher intracavity current density can be injected into the multi-quantum well active layer 140, thereby obtaining a higher internal quantum efficiency and realizing single-mode output.

[0031] In the prior art, to further optimize and limit high-order transverse modes, a zinc diffusion process is generally added to the manufacturing process. Specifically, a zinc diffusion method is used to create a mode-selective structure on the top distributed Bragg reflector. This method reduces the reflectivity of the DBR layer and increases the absorption loss of free carriers, thereby suppressing high-order transverse modes and achieving fundamental transverse mode lasing. However, in this manufacturing process, the depth (or concentration) of zinc diffusion depends solely on the temperature and time of the zinc diffusion process and cannot be precisely controlled.

[0032] In order to solve the above problems, Figure 1 As shown, in the present application, the top Bragg reflector layer 180 includes a first Bragg reflector layer 181, an insertion layer 182, and a second Bragg reflector layer 183, which are stacked in sequence. The insertion layer 182 is used to block the diffusion of a zinc diffusion region 1831 from the second Bragg reflector layer 183 to the first Bragg reflector layer 181. Consequently, when zinc diffusion is performed on the top Bragg reflector layer 180, zinc ions are first injected into the second Bragg reflector layer 183 from the side of the second Bragg reflector layer 183 facing away from the insertion layer 182 at a certain diffusion rate, forming the zinc diffusion region 1831. When the zinc ions reach the side of the insertion layer 182 closer to the second Bragg reflector layer 183, the blocking effect of the insertion layer 182 slows the diffusion rate of the zinc ions. This allows, in addition to controlling the temperature and time of the zinc diffusion process, the blocking effect of the insertion layer 182 to control the zinc diffusion depth, thereby facilitating precise control of the zinc diffusion depth.

[0033] like Figure 1 As shown, in the present application, the vertical cavity surface emitting laser 100 is manufactured by adding a zinc diffusion process during the preparation process, and its second Bragg reflector layer 183 has a zinc diffusion region 1831 to guide the flow of current through the zinc diffusion region 1831.

[0034] As an implementable manner, the diffusion coefficient of the first Bragg mirror layer 181 is the same as the diffusion coefficient of the second Bragg mirror layer 183 , and the diffusion coefficient of the second Bragg mirror layer 183 is different from the diffusion coefficient of the insertion layer 182 .

[0035] It should be noted that the first Bragg reflector layer 181 and the second Bragg reflector layer 183 are respectively located below and above the insertion layer 182 in the stacking direction. This distinction is only for ease of explanation and is not intended to limit the difference in the specific structures of the first Bragg reflector layer 181 and the second Bragg reflector layer 183. Optionally, the first Bragg reflector layer 181 and the second Bragg reflector layer 183 each include a plurality of component units stacked in sequence, each component unit including two AlGaAs layers with different refractive indices. For example, one of the AlGaAs layers has a higher Al content, for example, 90%, so that the AlGaAs layer has a higher refractive index, and the other AlGaAs layer has a lower Al content, for example, 20%, so that the AlGaAs layer has a lower refractive index. Since the actual composition of the first Bragg reflector layer 181 and the second Bragg reflector layer 183 is the same, the diffusion coefficient of the first Bragg reflector layer 181 and the diffusion coefficient of the second Bragg reflector layer 183 are the same. As a result, during the zinc diffusion process, the diffusion rate of zinc ions injected into the first Bragg reflector layer 181 and the diffusion rate of zinc ions injected into the second Bragg reflector layer 183 are also the same.

[0036] In the prior art, no insertion layer 182 is provided between the first Bragg reflector layer 181 and the second Bragg reflector layer 183. The depth of the zinc diffusion region 1831 is controlled only by the temperature and time of the zinc diffusion process. This can easily cause the depth of the zinc diffusion region 1831 to exceed a preset depth. In the present application, an insertion layer 182 is provided between the first Bragg reflector layer 181 and the second Bragg reflector layer 183. Since the actual composition of the insertion layer 182 is different from that of the first Bragg reflector layer 181 and the second Bragg reflector layer 183, the diffusion coefficient of the insertion layer 182 is different from that of the first Bragg reflector layer 181 and the second Bragg reflector layer 183. The diffusion coefficient of the second Bragg reflector layer 183 is different. As a result, during the zinc diffusion process, the diffusion rate of zinc ions injected into the insertion layer 182 is different from the diffusion rate of zinc ions injected into the first Bragg reflector layer 181 and the diffusion rate of zinc ions injected into the second Bragg reflector layer 183. This allows the insertion layer 182 to block the diffusion of zinc ions from the second Bragg reflector layer 183 to the first Bragg reflector layer 181. In addition to controlling the temperature and time of the zinc diffusion process, the depth of zinc diffusion can also be controlled by the blocking effect of the insertion layer 182, which helps to accurately control the depth of zinc diffusion.

[0037] As an practicable manner, the refractive index of light with a wavelength of λ in the insertion layer 182 is n, the thickness of the insertion layer 182 is d, and the relationship is satisfied: This allows the refractive index of the top Bragg reflector layer 180 to reach the refractive index of the VCSEL 100 .

[0038] As an illustrative embodiment, the material of the insertion layer 182 is gallium arsenide, aluminum gallium arsenide, indium gallium phosphide, aluminum indium phosphide, aluminum gallium indium phosphide, or indium gallium arsenide phosphide. When the material of the insertion layer 182 is aluminum gallium arsenide (i.e., AlGaAs), the higher the Al content, the greater the diffusion coefficient of the insertion layer 182, making it easier for zinc ions to be injected. Conversely, the lower the Al content, the smaller the diffusion coefficient of the insertion layer 182, making it more difficult for zinc ions to be injected.

[0039] For example, each constituent unit of the first Bragg reflector layer 181 and the second Bragg reflector layer 183 includes Al 0.9 Ga 0.1 As and Al 0.2 Ga 0.8 As, the wavelength λ of light is 850nm, and Al can be calculated 0.9 Ga 0.1 The refractive index n of As is 3.06, and Al 0.2 Ga 0.8 The refractive index n of As is 3.49. Substituting it into the above relationship, we can calculate Al 0.9 Ga 0.1 The thickness of As should be 69.4nm, Al 0.2 Ga 0.8 The thickness of As should be 60.9 nm.

[0040] When the material of the insertion layer 182 is gallium arsenide (i.e., GaAs), its refractive index n is 3.655, and the wavelength λ of light is 850 nm. Substituting the above relationship into the above relationship, it can be calculated that the thickness of the insertion layer 182 is 58.1 nm; when the material of the insertion layer 182 is aluminum gallium arsenide (i.e., AlGaAs), the Al content contained therein is 50%, i.e., Al 0.5 Ga 0.5 As, the wavelength λ of light is 850nm, and Al can be calculated 0.5 Ga 0.5 The refractive index n of As is 3.3. Substituting it into the above relationship, we can get Al 0.5 Ga 0.5 The thickness of As should be 64.4 nm.

[0041] like Figure 2 As shown in FIG. 1 , as an operative embodiment, the second Bragg reflector layer 183 has a light-through hole 1832 , a zinc diffusion region 1831 surrounding the outer edge of the light-through hole 1832 , and the current limiting hole 161 corresponds to the light-through hole 1832 in the stacking direction, so as to guide the flow of current through the zinc diffusion region 1831 . Figure 2 As shown, when the current flows through the second Bragg reflector layer 183, it will be injected into the current limiting hole 161 through the zinc diffusion region 1831. In this way, a higher intracavity current density can be injected into the multi-quantum well active layer 140, thereby obtaining a higher internal quantum efficiency and realizing single-mode output.

[0042] like Figure 1 As shown, as an implementable method, the current limiting hole 161 and the light-through hole 1832 are in positive correspondence in the stacking direction, so that the equivalent resistance R in the region is lower than the equivalent resistance of a single oxidation aperture in the prior art, thereby helping to improve device performance.

[0043] like Figure 1 and Figure 3 As shown, as an implementable manner, the aperture D2 of the light-through hole 1832 is smaller than the aperture D1 of the current-limiting hole 161 , so that the high-order transverse modes at the edge of the current-limiting hole 161 can be filtered out again through the light-through hole 1832 .

[0044] As an practicable manner, a first buffer layer 130 is arranged between the bottom Bragg reflector layer 120 and the multi-quantum well active layer 140, a second buffer layer 150 is arranged between the multi-quantum well active layer 140 and the oxide layer 160, and a third buffer layer 170 is arranged between the oxide layer 160 and the first Bragg reflector layer 181, so as to improve device performance through the first buffer layer 130, the second buffer layer 150 and the third buffer layer 170.

[0045] As an implementable method, a contact layer 190 is provided on the side of the second Bragg reflector layer 183 facing away from the insertion layer 182, so that when the device is turned on, current is injected through the contact layer 190, and the bottom Bragg reflector layer 120 and the multi-quantum well active layer 140 form a step structure, so as to achieve lateral oxidation of the device through the step structure.

[0046] As an practicable manner, a first electrode 200 is provided on the side of the contact layer 190 facing away from the second Bragg reflector layer 183 , and a second electrode 210 is provided on the table of the bottom Bragg reflector layer 120 close to the multi-quantum well active layer 140 , so as to facilitate electrical connection of the device through the first electrode 200 and the second electrode 210 .

[0047] Optionally, the first electrode 200 is a P-type electrode and the second electrode 210 is an N-type electrode. Correspondingly, the first Bragg reflector layer 181 and the second Bragg reflector layer 183 are both P-type Bragg reflector layers, and the bottom Bragg reflector layer 120 is an N-type Bragg reflector layer.

[0048] The foregoing description is merely an optional embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A vertical cavity surface emitting laser, characterized in that: The invention comprises a substrate and a bottom Bragg reflector layer, a multi-quantum well active layer, an oxide layer with a current limiting hole and a top Bragg reflector layer stacked in sequence on the substrate. The top Bragg reflector layer comprises a first Bragg reflector layer, an insertion layer and a second Bragg reflector layer with a zinc diffusion region stacked in sequence. The insertion layer is used to block the zinc diffusion region from diffusing from the second Bragg reflector layer to the first Bragg reflector layer. The diffusion coefficient of the first Bragg reflector layer is the same as the diffusion coefficient of the second Bragg reflector layer, and the diffusion coefficient of the second Bragg reflector layer is different from the diffusion coefficient of the insertion layer.

2. The vertical cavity surface emitting laser according to claim 1, wherein: The refractive index of light with a wavelength of λ in the insertion layer is n, the thickness of the insertion layer is d, and the relationship is satisfied: .

3. The vertical cavity surface emitting laser according to claim 1, wherein: The material of the insertion layer is gallium arsenide, aluminum gallium arsenide, indium gallium phosphide, aluminum indium phosphide, aluminum gallium indium phosphide or indium gallium arsenide phosphide.

4. The vertical cavity surface emitting laser according to claim 1, wherein: The second Bragg reflector layer has a light-through hole, the zinc diffusion region surrounds the outer edge of the light-through hole, and the current limiting hole corresponds to the light-through hole in a stacking direction.

5. The vertical cavity surface emitting laser according to claim 4, characterized in that: The current limiting hole and the light passing hole are aligned with each other in a stacking direction.

6. The vertical cavity surface emitting laser according to claim 4, characterized in that The aperture of the light-transmitting hole is smaller than the aperture of the current-limiting hole.

7. The vertical cavity surface emitting laser according to claim 1, wherein: A first buffer layer is provided between the bottom Bragg reflector layer and the multi-quantum well active layer, a second buffer layer is provided between the multi-quantum well active layer and the oxide layer, and a third buffer layer is provided between the oxide layer and the first Bragg reflector layer.

8. The vertical cavity surface emitting laser according to claim 1, wherein: A contact layer is provided on a side of the second Bragg reflector layer facing away from the insertion layer, and the bottom Bragg reflector layer and the multi-quantum well active layer form a step structure.

9. The vertical cavity surface emitting laser according to claim 8, characterized in that: A first electrode is provided on a side of the contact layer facing away from the second Bragg reflector layer, and a second electrode is provided on a mesa of the bottom Bragg reflector layer close to the multi-quantum well active layer.

Images