Vertical cavity surface emitting laser and method for manufacturing the same

Abstract

The embodiment of the application relates to a vertical cavity surface emitting laser and a preparation method thereof, and specifically comprises a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer which are sequentially stacked, and a current injection blocking layer is further stacked, and a current injection channel is formed in the current injection blocking layer; a second electrode contact part, a transparent conductive film and a heavily doped semiconductor material part are located on the upper surface side of the second conductive semiconductor layer; wherein, in the stacking direction, the projection of the heavily doped semiconductor material part falls within the range of the projection of the current injection channel, and the projection of the second electrode contact part does not coincide with the projection of the current injection channel; a part of the transparent conductive film is in conductive connection with the second electrode contact part, and another part is in conductive connection with the second conductive semiconductor layer through the heavily doped semiconductor material part. In this way, the control of current distribution is better realized, and the light emission divergence angle of the VCSEL is optimized.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a vertical cavity surface-emitting laser and its fabrication method. Background Technology

[0002] A vertical-cavity surface-emitting laser (VCSEL) is a semiconductor laser whose laser emission direction is perpendicular to the epitaxial plane. Unlike typical edge-emitting lasers, VCSELs have advantages such as small far-field divergence angle, easy fiber coupling, low threshold current, high bandwidth, and high testing efficiency.

[0003] However, in practical applications, the beam divergence angle of VCSEL chips has become a key technical indicator requiring close monitoring, especially in applications with stringent beam quality requirements, where controlling the divergence angle is crucial. To optimize the divergence angle, several effective techniques have been explored. For example, adding an optical lens to the emitting surface of the VCSEL can converge the emitted light, thereby reducing the divergence angle; alternatively, shallow etching of the epitaxial surface of the VCSEL can suppress light emission from unetched areas, further controlling the divergence angle. However, simply improving the VCSEL chip along the optical path is insufficient to meet the optimization requirements of the divergence angle. In a typical VCSEL structure, to avoid obstructing the center of the emitting aperture, the metal electrode can only be placed on the outer ring of the aperture. This means current can only be injected from the periphery of the aperture, resulting in a higher current density at the aperture edge than at the center. This non-uniform current distribution exacerbates beam divergence, further increasing the divergence angle and affecting the beam quality and application performance of the VCSEL.

[0004] Therefore, how to further optimize the beam divergence angle of VCSELs, especially to control the current distribution in the structural design, has become an important issue that urgently needs to be addressed in this field. Summary of the Invention

[0005] In view of this, the present application provides a vertical cavity surface-emitting laser and a method for fabricating the same, in order to solve at least one problem existing in the prior art.

[0006] In a first aspect, embodiments of this application provide a vertical-cavity surface-emitting laser, comprising:

[0007] A first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are stacked sequentially. A current injection barrier layer is also stacked between the first conductive semiconductor layer and the active layer and / or between the second conductive semiconductor layer and the active layer. A current injection channel is formed in the current injection barrier layer. The second conductive semiconductor layer has an upper surface that is away from the current injection barrier layer.

[0008] The second electrode contact, the transparent conductive film, and the heavily doped semiconductor material are located on the upper surface side of the second conductive semiconductor layer;

[0009] in,

[0010] Along the stacking direction, the projection of the heavily doped semiconductor material portion falls within the range of the projection of the current injection channel, and the projection of the second electrode contact portion does not coincide with the projection of the current injection channel;

[0011] A portion of the transparent conductive film is electrically connected to the second electrode contact portion, and another portion is electrically connected to the second conductive semiconductor layer through the heavily doped semiconductor material portion.

[0012] In conjunction with the first aspect of this application, in an optional embodiment, the heavily doped semiconductor material portion is in direct contact with the upper surface of the second conductive semiconductor layer; the transparent conductive film covers the heavily doped semiconductor material portion and the second conductive semiconductor layer; and the second electrode contact portion is located on the transparent conductive film.

[0013] In conjunction with the first aspect of this application, in an alternative embodiment, along the stacking direction,

[0014] The projection center of the heavily doped semiconductor material portion coincides with the projection center of the current injection channel; and / or,

[0015] The projection of the heavily doped semiconductor material portion is circular or annular.

[0016] In conjunction with the first aspect of this application, in an alternative embodiment, the material of the transparent conductive film includes ITO.

[0017] In conjunction with the first aspect of this application, in an optional embodiment, the transparent conductive film further includes at least one transparent material layer stacked on the side of the transparent conductive film away from the second conductive semiconductor layer, wherein the transparent conductive film satisfies:

[0018]

[0019] in, The refractive index of the transparent conductive film is... The thickness of the transparent conductive film is [missing information]. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The wavelength of the vertical cavity surface-emitting laser is denoted as λ.

[0020] Secondly, embodiments of this application provide a method for fabricating a vertical-cavity surface-emitting laser, the method comprising:

[0021] A first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are provided in sequence. A current injection barrier layer is further stacked between the first conductive semiconductor layer and the active layer and / or between the second conductive semiconductor layer and the active layer. The current injection barrier layer has a current injection channel forming position.

[0022] A second electrode contact, a transparent conductive film, and a heavily doped semiconductor material are formed on the second conductive semiconductor layer; wherein, along the stacking direction, the projection of the heavily doped semiconductor material falls within the range of the projection of the current injection channel formation position, and the projection of the second electrode contact does not coincide with the projection of the current injection channel formation position; a portion of the transparent conductive film is conductively connected to the second electrode contact, and another portion is conductively connected to the second conductive semiconductor layer through the heavily doped semiconductor material.

[0023] In conjunction with a second aspect of this application, in an optional embodiment, a second electrode contact, a transparent conductive film, and a heavily doped semiconductor material portion are formed on the second conductive semiconductor layer, including:

[0024] A heavily doped semiconductor material layer is formed on the upper surface of the second conductive semiconductor layer, which is in direct contact with the second conductive semiconductor layer;

[0025] The heavily doped semiconductor material layer is patterned to form the heavily doped semiconductor material portion;

[0026] A transparent conductive film is formed covering the heavily doped semiconductor material portion and the second conductive semiconductor layer;

[0027] The second electrode contact portion is formed on the transparent conductive film;

[0028] The method further includes:

[0029] A trench is formed to expose the current injection barrier layer, and the current injection barrier layer is oxidized through the trench. The unoxidized portion at the center of the current injection barrier layer forms the current injection channel.

[0030] In conjunction with a second aspect of this application, in an alternative embodiment, along the stacking direction,

[0031] The projection center of the heavily doped semiconductor material portion coincides with the projection center of the current injection channel; and / or,

[0032] The projection of the heavily doped semiconductor material portion is circular or annular.

[0033] In conjunction with a second aspect of this application, in an alternative embodiment, the material of the transparent conductive film includes ITO.

[0034] In conjunction with a second aspect of this application, in an optional embodiment, the method further includes:

[0035] At least one transparent material layer is formed on the upper surface of the transparent conductive film;

[0036] The transparent conductive film satisfies:

[0037]

[0038] in, The refractive index of the transparent conductive film is... The thickness of the transparent conductive film is [missing information]. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The wavelength of the vertical cavity surface-emitting laser is denoted as λ.

[0039] The vertical-cavity surface-emitting laser (VCSEL) and its fabrication method provided in this application involve forming a second electrode contact, a transparent conductive film, and a heavily doped semiconductor material on the upper surface of a second conductive semiconductor layer. Along the stacking direction, the projection of the heavily doped semiconductor material falls within the projection range of the current injection channel, while the projection of the second electrode contact does not coincide with the projection of the current injection channel. A portion of the transparent conductive film is conductively connected to the second electrode contact, and another portion is conductively connected to the second conductive semiconductor layer through the heavily doped semiconductor material. Thus, after current is injected through the second electrode contact, it flows through the transparent conductive film to the heavily doped semiconductor material, and then enters the second conductive semiconductor layer through the heavily doped semiconductor material. Because the projection of the heavily doped semiconductor material falls within the projection range of the current injection channel, the current can pass through the current injection channel more uniformly, thereby better controlling the current distribution and optimizing the emission divergence angle of the VCSEL.

[0040] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0042] Figure 1 This is a schematic diagram of the cross-sectional structure of a vertical cavity surface-emitting laser in related technologies;

[0043] Figure 2 This is a top view of a vertical-cavity surface-emitting laser (VCSEL) in related technologies.

[0044] Figure 3 A comparison of light distribution curves under two different current density distributions;

[0045] Figure 4 This is a cross-sectional structural diagram of a vertical cavity surface-emitting laser provided in an embodiment of this application;

[0046] Figure 5 A schematic flowchart illustrating the fabrication method of a vertical-cavity surface-emitting laser provided in this application embodiment;

[0047] Figures 6 to 14 A cross-sectional structural diagram of a vertical cavity surface-emitting laser provided in the embodiments of this application during its fabrication process;

[0048] Figure 15 A cross-sectional structural schematic diagram of a vertical cavity surface-emitting laser provided as a variation of this application;

[0049] Figure 16 A cross-sectional structural schematic diagram of a vertical cavity surface-emitting laser provided as another variation of this application. Detailed Implementation

[0050] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the disclosure of the present application to those skilled in the art.

[0051] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, to avoid confusion with this application, some technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0052] In the accompanying drawings, for clarity, the dimensions of layers, areas, and elements, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0053] When an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. Although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this application.

[0054] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship of one element or feature shown in the figure to other elements or features. In addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “under” the other element or feature will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0055] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0056] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solution of this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0057] Combination Figure 1 and Figure 2 As shown, in a vertical cavity surface-emitting laser, the metal electrode 170 is located on the outer ring of the light-emitting aperture. After the current flows into the second conductive semiconductor layer 140 through the electrode 170, it is blocked by the current injection barrier layer 130 and enters the active layer 120 only through the current injection channel 131 (the position of the light-emitting aperture). Figure 1 The direction of current flow is illustrated by arrowed lines. When flowing along the shortest path, charges tend to enter the active layer 120 through the edge of the current injection channel 131 (i.e., the edge of the light emission aperture), resulting in a higher current density injected at the edge and a relatively lower current density at the center. Since the light emission energy of a region is proportional to the current density of that region, the higher light emission energy at the edge and the lower light emission energy at the center directly leads to a larger divergence angle.

[0058] Figure 3The graph shows a comparison of light distribution curves under two different current density distributions. It can be seen from the graph that when the central current density is high, the light energy emitted from the central region is greater, the light shape is more concentrated, and the divergence angle is smaller. Conversely, when the central current density is low, the light energy emitted from the central region is lower, the light shape is more dispersed, and the divergence angle is larger.

[0059] Based on this, this application provides a vertical-cavity surface-emitting laser (VCSEL). Please refer to [link / reference]. Figure 4 The vertical cavity surface-emitting laser includes: a first conductive semiconductor layer 110, an active layer 120, and a second conductive semiconductor layer 140 stacked sequentially. A current injection barrier layer 130 is also stacked between the first conductive semiconductor layer 110 and the active layer 120 and / or between the second conductive semiconductor layer 140 and the active layer 120 (the figure only shows an example where the current injection barrier layer 130 is located between the second conductive semiconductor layer 140 and the active layer 120). A current injection channel 131 is formed in the current injection barrier layer 130. The second conductive semiconductor layer 140 has an upper surface that is away from the current injection barrier layer 130. The vertical cavity surface-emitting laser further includes: a second electrode contact 171 located on the upper surface side of the second conductive semiconductor layer 140, a transparent conductive film 160, and a heavily doped semiconductor material portion 150; wherein, along the stacking direction, the projection of the heavily doped semiconductor material portion 150 falls within the projection range of the current injection channel 131, and the projection of the second electrode contact 171 does not coincide with the projection of the current injection channel 131; a portion of the transparent conductive film 160 is conductively connected to the second electrode contact 171, and another portion is conductively connected to the second conductive semiconductor layer 140 through the heavily doped semiconductor material portion 150.

[0060] contrast Figure 1 and Figure 4 The direction of the arrow in the middle indicates that, in this embodiment, although the projection of the second electrode contact 171 does not coincide with the projection of the current injection channel 131 (specifically, for example, located on the outer ring of the current injection channel 131 as in related technologies), after the current is injected through the second electrode contact 171, it no longer enters the second conductive semiconductor layer 140 from the location of the second electrode contact 171, but flows through the transparent conductive film 160 to the heavily doped semiconductor material 150, and then enters the second conductive semiconductor layer 140 through the heavily doped semiconductor material 150. Since the projection of the heavily doped semiconductor material 150 falls within the range of the projection of the current injection channel 131, the current can pass through the current injection channel 131 more evenly, thus better realizing the control of the current distribution and optimizing the light emission divergence angle of the VCSEL.

[0061] The first conductive semiconductor layer 110, the active layer 120, and the second conductive semiconductor layer 140 can be collectively referred to as an epitaxial structure layer. In practical applications, the first conductivity type is specifically, for example, N-type, and the second conductivity type is specifically, for example, P-type; thus, the first conductive semiconductor layer 110 is an N-type semiconductor layer, specifically, an N-type DBR (Distributed Bragg Reflection) layer; and the second conductive semiconductor layer 140 is a P-type semiconductor layer, specifically, a P-type DBR layer. The active layer 120 can specifically be a quantum well structure, used to generate the optical gain required to form a laser.

[0062] The epitaxial structure layer can be formed by epitaxial growth on a substrate; specifically, a substrate may also be included below the first conductive semiconductor layer 110. The substrate material may include III-V group semiconductor materials such as GaAs, InP, and GaSb, specifically selected according to the output wavelength.

[0063] The stacking direction of the material layers deposited on the substrate is also called the height direction of the device, or the direction perpendicular to the substrate and the plane where each material layer is located. For example, along the stacking direction, it can also be understood as along the direction perpendicular to the upper surface of the second conductive semiconductor layer 140; along the stacking direction, the projection of the heavily doped semiconductor material portion 150 falls within the range of the projection of the current injection channel 131, which can also be understood as the heavily doped semiconductor material portion 150 being located in the region directly above the current injection channel 131.

[0064] Combination Figures 12 to 13 As shown, the current-injected barrier layer 130 can be formed by oxidation of the initially deposited material layer. The material of the current-injected barrier layer 130 is typically a group III-V multi-component compound with a high Al content, specifically, Al... z Ga 1-z As (0.9 < z ≤ 1). In the actual preparation process, a wet oxidation process can be used to react the outer part in contact with the oxidant to form an insulating oxide (e.g., Al2O3). As the oxidation reaction continues, the current injection barrier layer 130 is gradually oxidized from the periphery to the center. Under certain reaction time, oxidation temperature and oxidant flow rate control, the final current injection barrier layer 130 includes an unoxidized part at the center, i.e., the current injection channel 131, through which charge can pass; the current injection barrier layer 130 also includes an oxidized part at the periphery, i.e., the oxide region 132, which blocks the flow of charge.

[0065] Although the accompanying drawings show the current injection barrier layer 130 located between the first conductive semiconductor layer 110 and the active layer 120, the current injection barrier layer 130 can obviously also be located between the second conductive semiconductor layer 140 and the active layer 120, and can also include both the portion located between the first conductive semiconductor layer 110 and the active layer 120 and the portion located between the second conductive semiconductor layer 140 and the active layer 120 (in some specific applications, the current injection barrier layer 130 can also be considered to be located within the active layer 120).

[0066] The heavily doped semiconductor material portion 150, also known as an ohmic contact portion, can be formed using processes well-known in the art, such as ion implantation. To reduce contact resistance when conducting the second conductive semiconductor layer 140, a heavily doped semiconductor material layer is often formed between the second conductive semiconductor layer 140 and the electrode. In this embodiment, the position and area of ​​the heavy doping are adjusted so that the projection of the heavily doped semiconductor material portion 150 falls within the projection range of the current injection channel 131 along the stacking direction. Therefore, the area of ​​the second conductive semiconductor layer 140 directly above the current injection channel 131 is used for external conductive connection. In embodiments where the second conductive semiconductor layer 140 is a P-type semiconductor layer, the heavily doped semiconductor material portion 150 is specifically a P-type heavily doped semiconductor material portion (P++).

[0067] Please combine Figure 4 , Figure 7 and Figure 8 The heavily doped semiconductor material portion 150 can be located on the upper surface of the second conductive semiconductor layer 140. In the actual fabrication process, a heavily doped semiconductor material layer 1500 (or Cap layer) can first be formed on the upper surface of the second conductive semiconductor layer 140, and then patterned so that only the portion directly above the current injection channel 131 is retained, thereby forming the desired heavily doped semiconductor material portion 150. The heavily doped semiconductor material portion 150 can be cylindrical. The material of the heavily doped semiconductor material portion 150 can be the same as the material of the second conductive semiconductor layer 140.

[0068] However, the location of the heavily doped semiconductor material portion 150 on the upper surface side of the second conductive semiconductor layer 140 is not limited to this; as a variation, please refer to Figure 15 The heavily doped semiconductor material portion 150 may also be located on the surface of the second conductive semiconductor layer 140, specifically formed by heavily doping a portion of the upper surface side of the second conductive semiconductor layer 140.

[0069] The projection of the heavily doped semiconductor material section 150 falls within the projection area of ​​the current injection channel 131. This includes cases where the projected area of ​​the heavily doped semiconductor material section 150 is smaller than the projected area of ​​the current injection channel 131, and also excludes cases where their projections overlap. Please refer to... Figure 4 Considering that after current injection, in addition to injecting the active layer 120 in the vertically downward direction, there will also be some lateral diffusion, in order to further reduce the divergence angle, the projection of the heavily doped semiconductor material section 150 falls within the projection range of the current injection channel 131, and the projected area of ​​the heavily doped semiconductor material section 150 is smaller than the projected area of ​​the current injection channel 131.

[0070] Optionally, along the stacking direction, the projection center of the heavily doped semiconductor material section 150 coincides with the projection center of the current injection channel 131; thereby making the current distribution more centrally symmetrical relative to the light exit aperture. However, it should be understood that this application does not exclude the possibility that the projection centers of the heavily doped semiconductor material section 150 and the current injection channel 131 may not coincide for other design considerations. Based on the improved concept proposed in this application, by adjusting the position of the heavily doped semiconductor material section 150, current can be injected into the second conductive semiconductor layer 140 from a specific region, thereby improving the controllability of the current distribution.

[0071] Optionally, the projection of the heavily doped semiconductor material section 150 along the stacking direction is circular or annular. Understandably, a circular projection of the heavily doped semiconductor material section 150 allows for a more uniform distribution of charge flowing into the second conductive semiconductor layer 140, and makes it easier for current to concentrate in the central region. This significantly increases the current density at the center of the light-emitting aperture, while correspondingly reducing the current density at the aperture's edge, thereby effectively reducing the light emission divergence angle. Furthermore, in some applications where a larger divergence angle at the aperture's edge is required, the projection shape of the heavily doped semiconductor material section 150 can be designed as annular to meet practical needs.

[0072] As an optional specific implementation, the projection of the heavily doped semiconductor material section 150 is circular along the stacking direction, and the projection center of the heavily doped semiconductor material section 150 coincides with the projection center of the current injection channel 131. The projection area of ​​the heavily doped semiconductor material section 150 is smaller than the projection area of ​​the current injection channel 131. In this way, the current density at the center of the light emission aperture is greatly increased, and the light emission divergence angle is reduced.

[0073] In some embodiments, the projection radius of the heavily doped semiconductor material portion 150 can be less than 70% of the projection radius of the current injection channel 131; further, it can be less than 50%.

[0074] Furthermore, the projection of the second electrode contact 171 does not coincide with the projection of the current injection channel 131, thereby preventing the second electrode contact 171 from blocking the light emitted by the device. The projection of the second electrode contact 171 can surround the projection of the current injection channel 131 (which can be combined with...). Figure 2 (Understanding); the projection center of the second electrode contact 171 may coincide with the projection center of the current injection channel 131. In practical applications, the second electrode contact 171 may include a metal stack structure, specifically using VCSEL P-plane ohmic contact materials commonly used in the art, such as Ti / Pt / Au or other suitable metal materials, etc., which are not specifically limited in this application.

[0075] The material of the transparent conductive film 160 may include ITO (indium tin oxide). Alternatively, AZO (aluminum-doped zinc oxide) conductive film, silver nanowire conductive film, or other suitable transparent conductive film materials may also be used.

[0076] A portion of the transparent conductive film 160 is electrically connected to the second electrode contact 171, and another portion is electrically connected to the second conductive semiconductor layer 140 through the heavily doped semiconductor material portion 150. Thus, the lateral span of the transparent conductive film 160 lies between directly above and to the side above the current injection channel 131. As an optional embodiment, the transparent conductive film 160 covers the upper surface of the second conductive semiconductor layer 140, and simultaneously covers the upper surface and sidewalls of the heavily doped semiconductor material portion 150. Since there is no heavily doped portion in the area where the transparent conductive film 160 and the second conductive semiconductor layer 140 are in direct contact, the contact between them is high-resistance. In the area where the heavily doped semiconductor material portion 150 is located, that is, the area directly above the light-emitting aperture, the contact is low-resistance. Therefore, after the current is injected through the second electrode contact portion 171, it expands laterally through the transparent conductive film 160 (expands within the plane of the transparent conductive film 160), and finally can only flow into the second conductive semiconductor layer 140 through the area directly above the light-emitting aperture with low resistance. This makes the current distribution more uniform and controllable, and the current density at the center of the light-emitting aperture is greatly improved.

[0077] Optionally, the heavily doped semiconductor material portion 150 is in direct contact with the upper surface of the second conductive semiconductor layer 140; a transparent conductive film 160 covers the heavily doped semiconductor material portion 150 and the second conductive semiconductor layer 140; and the second electrode contact portion 171 is located on the transparent conductive film 160. This optimizes the device structure design and simplifies the fabrication process.

[0078] Furthermore, this application is not limited to this, and other arrangements can obviously be used to achieve conductive connection between the heavily doped semiconductor material portion 150, the transparent conductive film 160, and the second electrode contact portion 171. For example, the sidewall of the heavily doped semiconductor material portion 150 may not be covered by the transparent conductive film 160, but a transparent dielectric layer may be formed on the upper surface of the second conductive semiconductor layer 140, except for the area where the heavily doped semiconductor material portion 150 is located, and the transparent conductive film 160 may cover the heavily doped semiconductor material portion 150 and the transparent dielectric layer; or, for example, the second electrode contact portion 171 may not be located on the transparent conductive film 160, but may be partially embedded in the transparent conductive film 160.

[0079] Please continue to refer to this. Figure 4 The vertical-cavity surface-emitting laser further includes at least one transparent material layer (refer to the first transparent material layer 181 and the second transparent material layer 182 shown in the figure) stacked on the side of the transparent conductive film 160 away from the second conductive semiconductor layer 140. The transparent conductive film 160 satisfies the following conditions:

[0080]

[0081] in, The refractive index of the transparent conductive film is 160. The thickness of the transparent conductive film is 160. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The emission wavelength of a vertical cavity surface-emitting laser.

[0082] Thus, based on the thickness and refractive index of each transparent material layer stacked on the transparent conductive film 160, and combined with the refractive index of the transparent conductive film 160 itself, the thickness of the transparent conductive film 160 can be determined. The transparent conductive film 160 can then be set according to the determined thickness to improve transmittance, reduce light loss, and optimize optical performance.

[0083] Specifically, taking a transparent material layer comprising only a first transparent material layer 181 and a second transparent material layer 182 as an example, the refractive index of the first transparent material layer 181 is... Thickness is The refractive index of the second transparent material layer 182 is Thickness is Then the transparent conductive film 160 and each transparent material layer satisfy the following:

[0084]

[0085] That is, the transparent conductive film 160 satisfies:

[0086]

[0087] Therefore, given the selected transparent conductive film 160 material, the thickness of the transparent conductive film 160 can be calculated based on its refractive index.

[0088] Next, please refer to Figure 16 Based on the foregoing embodiments, the vertical-cavity surface-emitting laser (VCSEL) may further include an optical path converging element 200. The optical path converging element 200 is disposed on the emitting surface side of the VCSEL, specifically, for example, an optical lens, to converge the emitted light. The technical solution provided in this application can not only directly alter the emitted light itself by changing the current density distribution; it can also be used in conjunction with optical path converging schemes (such as adding a lens to the surface) to further reduce the divergence angle.

[0089] Based on this, the embodiments of this application also provide a method for fabricating a vertical-cavity surface-emitting laser, please refer to... Figure 5 The method includes:

[0090] Step S501: A first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are provided in sequence. A current injection barrier layer is also stacked between the first conductive semiconductor layer and the active layer and / or between the second conductive semiconductor layer and the active layer. The current injection barrier layer has a current injection channel forming position.

[0091] In step S502, a second electrode contact, a transparent conductive film, and a heavily doped semiconductor material are formed on the second conductive semiconductor layer; wherein, along the stacking direction, the projection of the heavily doped semiconductor material falls within the range of the projection of the current injection channel formation position, and the projection of the second electrode contact does not coincide with the projection of the current injection channel formation position; a portion of the transparent conductive film is conductively connected to the second electrode contact, and another portion is conductively connected to the second conductive semiconductor layer through the heavily doped semiconductor material.

[0092] In this way, after the current is injected through the second electrode contact, it flows through the transparent conductive film to the heavily doped semiconductor material part, and then enters the second conductive semiconductor layer through the heavily doped semiconductor material part. Since the projection of the heavily doped semiconductor material part falls within the projection range of the current injection channel, the current can pass through the current injection channel more evenly, thereby better controlling the current distribution and optimizing the light emission divergence angle of the VCSEL.

[0093] Below, in conjunction with Figures 6 to 14The vertical cavity surface-emitting laser and its fabrication method provided in the embodiments of this application will be further described in detail.

[0094] First, please refer to Figure 6 A first conductive semiconductor layer 110, an active layer 120, and a second conductive semiconductor layer 140 are provided in sequence. A current injection barrier layer 130 is also stacked between the first conductive semiconductor layer 110 and the active layer 120 and / or between the second conductive semiconductor layer 140 and the active layer 120 (the figure only shows an example where the current injection barrier layer 130 is located between the second conductive semiconductor layer 140 and the active layer 120). The current injection barrier layer 130 has a current injection channel formation location.

[0095] The first conductive semiconductor layer 110, the active layer 120, and the second conductive semiconductor layer 140 can be formed using epitaxial growth processes commonly used in the art. Specifically, although not explicitly shown in the figures, in actual fabrication, a substrate can be provided first, and then the aforementioned epitaxial layers can be sequentially grown on the substrate.

[0096] The substrate material can include III-V group semiconductor materials such as GaAs, InP, and GaSb, and the specific material is selected according to the output wavelength.

[0097] The first conductive semiconductor layer 110 can be an N-type semiconductor layer, specifically an N-type DBR layer; the second conductive semiconductor layer 140 can be a P-type semiconductor layer, specifically a P-type DBR layer.

[0098] The active layer 120 can be a quantum well structure, used to generate the optical gain required to form a laser.

[0099] The material of the current-injected barrier layer 130 is typically a group III-V multi-component compound with a high Al content, specifically, Al... z Ga 1-z As (0.9 < z ≤ 1).

[0100] Next, please refer to Figure 7 and Figure 8 A heavily doped semiconductor material layer 1500 is formed on the upper surface of the second conductive semiconductor layer 140, which is in direct contact with the second conductive semiconductor layer 140; then, the heavily doped semiconductor material layer 1500 is patterned to form the heavily doped semiconductor material portion 150.

[0101] The heavily doped semiconductor material layer 1500 can be formed using a deposition process combined with an ion implantation process. The material of the heavily doped semiconductor material layer 1500 (heavily doped semiconductor material section 150) can be the same as the material of the second conductive semiconductor layer 140. In an embodiment where the second conductive semiconductor layer 140 is a P-type semiconductor layer, the heavily doped semiconductor material section 150 is specifically a P-type heavily doped semiconductor material section (P++).

[0102] The patterning of the heavily doped semiconductor material layer 1500 can be specifically performed using photolithography. First, a photoresist layer is coated on the heavily doped semiconductor material layer 1500; then, the photoresist layer is patterned through exposure, development, and other steps; next, the heavily doped semiconductor material layer 1500 is etched using the patterned photoresist layer as a mask. The etching process can specifically be performed using a dry etching process, which is not specifically limited in this application; after etching, the remaining photoresist layer is removed to form the desired heavily doped semiconductor material portion 150.

[0103] It should be noted that this application is not limited to this; please refer to [reference needed]. Figure 15 The heavily doped semiconductor material portion 150 may also be located on the surface of the second conductive semiconductor layer 140, specifically formed by heavily doping a specific region on the upper surface side of the second conductive semiconductor layer 140.

[0104] Whether the heavily doped semiconductor material layer 150 is patterned to form the heavily doped semiconductor material portion 150 by retaining a portion of the material, or the heavily doped semiconductor material portion 150 is formed by heavily doping a specific area on the upper surface of the second conductive semiconductor layer 140, the projection of the heavily doped semiconductor material portion 150 must fall within the projection range of the current injection channel 131 to be formed in the subsequent process. The projected area of ​​the heavily doped semiconductor material portion 150 is usually smaller than the projected area of ​​the current injection channel 131, but the possibility of overlapping projections cannot be ruled out.

[0105] In some alternative embodiments, the projection center of the heavily doped semiconductor material portion 150 coincides with the projection center of the current injection channel 131 along the stacking direction; thereby making the current distribution more centrally symmetrical relative to the light exit aperture. However, it should be understood that this application does not exclude the possibility that the projection centers of the heavily doped semiconductor material portion 150 and the current injection channel 131 may not coincide for other design considerations. Based on the improved concept proposed in this application, by adjusting the position of the heavily doped semiconductor material portion 150, current can be injected into the second conductive semiconductor layer 140 from a specific region, thereby improving the controllability of the current distribution.

[0106] In some alternative embodiments, the projection of the heavily doped semiconductor material portion 150 along the stacking direction is circular or annular. Understandably, a circular projection of the heavily doped semiconductor material portion 150 (the heavily doped semiconductor material portion 150 is generally cylindrical) allows for a more uniform distribution of charge flowing into the second conductive semiconductor layer 140, and makes it easier for current to concentrate in the central region. This significantly increases the current density at the center of the light-emitting aperture, while correspondingly reducing the current density at the edge of the aperture, thereby effectively reducing the light emission divergence angle. Furthermore, in some applications where a larger divergence angle at the edge of the aperture is required, the projection shape of the heavily doped semiconductor material portion 150 can also be designed as annular to meet practical needs.

[0107] As an optional specific implementation, the projection of the heavily doped semiconductor material section 150 is circular along the stacking direction, and the projection center of the heavily doped semiconductor material section 150 coincides with the projection center of the current injection channel 131. The projection area of ​​the heavily doped semiconductor material section 150 is smaller than the projection area of ​​the current injection channel 131. In this way, the current density at the center of the light emission aperture is greatly increased, and the light emission divergence angle is reduced.

[0108] In some embodiments, the projection radius of the heavily doped semiconductor material portion 150 can be less than 70% of the projection radius of the current injection channel 131; further, it can be less than 50%.

[0109] In practical applications, those skilled in the art can adjust the position, shape, and size of the heavily doped semiconductor material section 150 according to actual needs.

[0110] Next, please refer to Figure 9 A transparent conductive film 160 is formed covering the heavily doped semiconductor material portion 150 and the second conductive semiconductor layer 140.

[0111] The transparent conductive film 160 can be formed by a deposition process. The material of the transparent conductive film 160 may include ITO (indium tin oxide). Alternatively, AZO (aluminum-doped zinc oxide) conductive film, silver nanowire conductive film, or other suitable transparent conductive film materials may also be used.

[0112] The thickness of the transparent conductive film 160 is greater than the thickness of the heavily doped semiconductor material portion 150, so that the heavily doped semiconductor material portion 150 is in direct contact with the upper surface and sidewall of the heavily doped semiconductor material portion 150.

[0113] Next, please refer to Figure 10 A second electrode contact 171 is formed on the transparent conductive film 160.

[0114] The second electrode contact 171 can be formed on the upper surface of the transparent conductive film 160 by photolithography, vapor deposition, and metal lift-off processes. In practical applications, the second electrode contact 171 may include a metal stack structure, specifically using VCSEL P-plane ohmic contact materials commonly used in the art, such as Ti / Pt / Au or other suitable metal materials, etc., which are not specifically limited in this application.

[0115] Patterning is achieved through photolithography to ensure that the projection of the second electrode contact 171 does not coincide with the projection of the current injection channel 131, thereby preventing the second electrode contact 171 from blocking light emission from the device. The projection of the second electrode contact 171 can surround the projection of the current injection channel 131; the center of the projection of the second electrode contact 171 can coincide with the center of the projection of the current injection channel 131.

[0116] Next, please refer to Figure 11 A first transparent material layer 181 is formed on the upper surface of the transparent conductive film 160. Specifically, the first transparent material layer 181 can cover the second electrode contact portion 171 and the transparent conductive film 160. The thickness of the first transparent material layer 181 can be greater than the thickness of the second electrode contact portion 171.

[0117] The first transparent material layer 181 can be formed by a deposition process. The material of the first transparent material layer 181 can be a transparent insulating material, specifically including SiN.

[0118] Next, please refer to Figure 12 This forms trenches that expose the current injection barrier layer 130.

[0119] Specifically, a photoresist layer can be formed on the first transparent material layer 181, and then the photoresist layer can be patterned through exposure, development and other steps. Then, the patterned photoresist layer is used as a mask for etching, and the etching depth extends beyond the current injection barrier layer 130. The etching process can be performed using a dry etching process, which is not specifically limited in this application. In this way, the formed trench penetrates the first transparent material layer 181, the transparent conductive film 160 and the second conductive semiconductor layer 140, and can further penetrate the current injection barrier layer 130, and may even extend into the first conductive semiconductor layer 110.

[0120] Next, please refer to Figure 13 The current injection barrier layer 130 is oxidized by trenching, and the unoxidized part in the center of the current injection barrier layer 130 forms the current injection channel 131.

[0121] Specifically, the current injection barrier layer 130 can be oxidized using a wet oxidation process, causing the outer portion in contact with the oxidant to react and transform into an insulating oxide (e.g., Al2O3). As the oxidation reaction continues, the current injection barrier layer 130 is gradually oxidized from the periphery to the center. Under controlled oxidation time, oxidation temperature, and oxidant flow rate, the final current injection barrier layer 130 includes an unoxidized portion at the center, i.e., the current injection channel 131 (or conductive via), through which charge can pass. The current injection barrier layer 130 also includes an oxidized portion at the periphery, i.e., the oxide region 132, which blocks charge flow.

[0122] Furthermore, a second transparent material layer 182 is formed on the first transparent material layer 181.

[0123] The second transparent material layer 182 can be formed using a deposition process. The material of the second transparent material layer 182 is a transparent insulating material, specifically including, for example, SiN. The second transparent material layer 182 not only covers the upper surface of the first transparent material layer 181, but can also further cover the sidewalls and bottom wall of the trench.

[0124] It should be noted that although the embodiments of this application describe the formation of a first transparent material layer 181 and a second transparent material layer 182, in specific applications, one or more transparent material layers may be formed according to actual needs, and this application does not make specific limitations in this regard.

[0125] At least one transparent material layer is formed on the upper surface of the transparent conductive film 160, and the transparent conductive film 160 satisfies the following:

[0126]

[0127] in, The refractive index of the transparent conductive film is 160. The thickness of the transparent conductive film is 160. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The wavelength of the vertical-cavity surface-emitting laser (VCSEL) is defined as the emission wavelength. Thus, based on the thickness and refractive index of each transparent material layer stacked on the transparent conductive film 160, and combined with the refractive index of the transparent conductive film 160 itself, the thickness of the transparent conductive film 160 can be determined. Therefore, the transparent conductive film 160 is set according to the determined thickness to improve transmittance, reduce light loss, and optimize optical performance. The transparent conductive film 160 and each transparent material layer refer to all conductive or non-conductive transparent film layers on the light-emitting surface side of the VCSEL (specifically, covering the light-emitting aperture).

[0128] Finally, please refer to Figure 14 The subsequent process steps are then executed to complete the fabrication of the VCSEL.

[0129] Specifically, an etching process can be performed to form a through-hole exposing the second electrode contact 171; the through-hole is then filled with conductive material to form an electrode path 172. Next, a wire bonding electrode 173 is fabricated on a transparent material layer, which is conductively connected to the electrode path 172 (specifically, through the electrode path 172 and the second electrode contact 171). The wire bonding electrode 173 is specifically the p-side electrode of the VCSEL. Next, the back side of the device structure can be thinned to fabricate a back electrode 190. The back electrode 190 is specifically the n-side electrode of the VCSEL. Finally, the structure is cut into cores. All of the above processes can be completed using conventional VCSEL fabrication processes, and will not be elaborated upon here.

[0130] Understandably, compared to converging the light-emitting path to improve the divergence angle, this embodiment retains a highly doped Cap layer (i.e., heavily doped semiconductor material portion 150) in a specific region on the surface of the epitaxial layer through an etching process, and grows a transparent conductive film 160 on the surface of the light-emitting aperture. The combination of these two methods ensures that current can only be injected into the epitaxial layer from the specific region where the highly doped Cap layer is retained (specifically, it first flows into the second conductive semiconductor layer 140), significantly increasing the current density in the specific region and thus changing the divergence angle. The specific region can be a region aligned with the center of the light-emitting aperture and smaller than the area of ​​the aperture, or it can be a non-central region selected according to actual needs. According to the embodiments of this application, the current distribution can be controlled to optimize the specific desired light-emitting divergence angle.

[0131] Furthermore, the above method may also include forming an optical path converging element 200 on the emitting surface side of the vertical cavity surface-emitting laser. Specifically, the optical path converging element 200 may be an optical lens, used to converge the emitted light. The technical solution provided in this application can not only directly alter the emitted light itself by changing the current density distribution; it can also be used in conjunction with optical path converging schemes (such as adding a lens to the surface) to further reduce the divergence angle.

[0132] It should be noted that the vertical-cavity surface-emitting laser (VCSEL) embodiments and the fabrication method embodiments of VCSELs provided in this application belong to the same concept; the technical features in the technical solutions described in each embodiment can be arbitrarily combined without conflict. However, it should be further noted that the combination of technical features of the VCSELs provided in the embodiments of this application can already solve the technical problems to be solved by this application; therefore, the VCSELs provided in the embodiments of this application are not limited to the fabrication method of the VCSELs provided in the embodiments of this application, and any VCSELs prepared by a fabrication method that can form the structure of the VCSELs provided in the embodiments of this application are within the scope of protection of this application.

[0133] It should be understood that the above embodiments are exemplary and not intended to encompass all possible implementations. Various modifications and changes can be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of this application that may not be explicitly described. Therefore, the above embodiments only illustrate several implementations of this application and do not limit the scope of protection of this patent application.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, include: A first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are stacked sequentially. A current injection barrier layer is also stacked between the first conductive semiconductor layer and the active layer and / or between the second conductive semiconductor layer and the active layer. A current injection channel is formed in the current injection barrier layer. The second conductive semiconductor layer has an upper surface that is away from the current injection barrier layer. The second electrode contact, the transparent conductive film, and the heavily doped semiconductor material are located on the upper surface side of the second conductive semiconductor layer; in, Along the stacking direction, the projection of the heavily doped semiconductor material portion falls within the range of the projection of the current injection channel, and the projection of the second electrode contact portion does not coincide with the projection of the current injection channel; A portion of the transparent conductive film is conductively connected to the second electrode contact portion, and another portion is conductively connected to the second conductive semiconductor layer through the heavily doped semiconductor material portion; The current flowing into the second conductive semiconductor layer enters the active layer through the current injection channel.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The heavily doped semiconductor material portion is in direct contact with the upper surface of the second conductive semiconductor layer; the transparent conductive film covers the heavily doped semiconductor material portion and the second conductive semiconductor layer; the second electrode contact portion is located on the transparent conductive film.

3. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, Along the stacking direction, The projection center of the heavily doped semiconductor material portion coincides with the projection center of the current injection channel; and / or, The projection of the heavily doped semiconductor material portion is circular or annular.

4. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The material of the transparent conductive film includes ITO.

5. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, It also includes at least one transparent material layer stacked on the side of the transparent conductive film away from the second conductive semiconductor layer, wherein the transparent conductive film satisfies: ， in, The refractive index of the transparent conductive film is... The thickness of the transparent conductive film is [missing information]. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The wavelength of the vertical cavity surface-emitting laser is denoted as λ.

6. A method for fabricating a vertical-cavity surface-emitting laser, characterized in that, The method includes: A first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer are provided in sequence. A current injection barrier layer is further stacked between the first conductive semiconductor layer and the active layer and / or between the second conductive semiconductor layer and the active layer. The current injection barrier layer has a current injection channel forming position. A second electrode contact, a transparent conductive film, and a heavily doped semiconductor material are formed on the second conductive semiconductor layer; wherein, along the stacking direction, the projection of the heavily doped semiconductor material falls within the range of the projection of the current injection channel formation position, and the projection of the second electrode contact does not coincide with the projection of the current injection channel formation position; a portion of the transparent conductive film is conductively connected to the second electrode contact, and another portion is conductively connected to the second conductive semiconductor layer through the heavily doped semiconductor material.

7. The method for fabricating a vertical-cavity surface-emitting laser according to claim 6, characterized in that, A second electrode contact, a transparent conductive film, and a heavily doped semiconductor material portion are formed on the second conductive semiconductor layer, including: A heavily doped semiconductor material layer is formed on the upper surface of the second conductive semiconductor layer, which is in direct contact with the second conductive semiconductor layer; The heavily doped semiconductor material layer is patterned to form the heavily doped semiconductor material portion; A transparent conductive film is formed covering the heavily doped semiconductor material portion and the second conductive semiconductor layer; The second electrode contact portion is formed on the transparent conductive film; The method further includes: A trench is formed to expose the current injection barrier layer, and the current injection barrier layer is oxidized through the trench. The unoxidized portion at the center of the current injection barrier layer forms the current injection channel.

8. The method for fabricating a vertical-cavity surface-emitting laser according to claim 6, characterized in that, Along the stacking direction, The projection center of the heavily doped semiconductor material portion coincides with the projection center of the current injection channel; and / or, The projection of the heavily doped semiconductor material portion is circular or annular.

9. The method for fabricating a vertical-cavity surface-emitting laser according to claim 6, characterized in that, The material of the transparent conductive film includes ITO.

10. The method for fabricating a vertical-cavity surface-emitting laser according to claim 6, characterized in that, The method further includes: At least one transparent material layer is formed on the upper surface of the transparent conductive film; The transparent conductive film satisfies: ， in, The refractive index of the transparent conductive film is... The thickness of the transparent conductive film is [missing information]. For the first The refractive index of the transparent material layer, For the first The thickness of the transparent material layer, It is a positive integer. This represents the total number of transparent material layers. It is a positive integer. The wavelength of the vertical cavity surface-emitting laser is denoted as λ.

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