A vertical-cavity surface-emitting laser and its fabrication method

Abstract

This invention discloses a vertical-cavity surface-emitting laser (VCSEL) and its fabrication method. The VCSEL comprises: a substrate; an epitaxial basic structure located on one side of the substrate; the epitaxial basic structure including multiple active regions stacked along the epitaxial growth direction; adjacent active regions connected by tunnel junctions; a dielectric layer located on the side of the epitaxial basic structure away from the substrate; and a standing-wave modulation layer interspersed within the epitaxial basic structure and disposed close to the dielectric layer. The standing-wave modulation layer is used to adjust the standing-wave distribution of the laser, so that the peaks in the standing-wave optical field deviate from the output cavity surface of the epitaxial basic structure; wherein the output cavity surface is the surface of the epitaxial basic structure away from the substrate. This reduces the absorption of photons by interface states, thereby achieving a higher COD threshold and ensuring that the device has a higher power density output.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a vertical cavity surface-emitting laser and its fabrication method. Background Technology

[0002] Vertical cavity surface-emitting lasers (VCSELs) are developed based on gallium arsenide semiconductor materials. Unlike other light sources such as light-emitting diodes (LEDs) and laser diodes (LDs), they have advantages such as small size, circular output spot, single longitudinal mode output, low threshold current, low cost, and easy integration into large-area arrays, making them an ideal light source for next-generation lidar.

[0003] Currently, to achieve higher power density output in VCSELs, the industry is gradually adopting multi-junction structure designs. This involves connecting multiple active regions in series via tunnel junctions to significantly increase the output power. To date, VCSEL structures with eight or more junctions have been developed. Through this multi-junction design, VCSEL power density has reached a level similar to that of edge-emitting devices. However, this also presents VCSELs with the same challenges as edge-emitting devices: under high power density, the laser cavity surface temperature rises rapidly, inducing bandgap contraction at the cavity surface, exacerbating photon absorption, and causing cavity surface burn-out, resulting in catastrophic optical damage (COD). Summary of the Invention

[0004] This invention provides a vertical cavity surface-emitting laser and its fabrication method to improve the COD resistance of the vertical cavity surface-emitting laser and achieve higher power density output of the device.

[0005] According to one aspect of the present invention, a vertical-cavity surface-emitting laser is provided, comprising:

[0006] Substrate;

[0007] An epitaxial basic structure is located on one side of the substrate; the epitaxial basic structure includes multiple active regions, which are stacked along the epitaxial growth direction; the active regions of adjacent layers are connected by tunnel junctions;

[0008] A dielectric layer is located on the side of the epitaxial basic structure away from the substrate;

[0009] A standing wave adjustment layer is interspersed within the epitaxial basic structure and disposed close to the dielectric layer; the standing wave adjustment layer is used to adjust the standing wave distribution of the laser so that the wave peak in the standing wave light field deviates from the light-emitting cavity surface of the epitaxial basic structure; the light-emitting cavity surface is the surface of the epitaxial basic structure away from the substrate.

[0010] Optionally, the epitaxial basic structure further includes:

[0011] A first Bragg reflector layer is located on one side of the substrate; the plurality of active regions are all located on the side of the first Bragg reflector layer away from the substrate;

[0012] The second Bragg reflector layer is located on the side of the active region furthest from the substrate.

[0013] A current diffusion layer is located on the side of the second Bragg reflector layer away from the substrate;

[0014] A contact layer is located on the side of the current diffusion layer away from the substrate;

[0015] The standing wave modulation layer is located between the current diffusion layer and the second Bragg reflection layer, within the current diffusion layer, or between the current diffusion layer and the contact layer.

[0016] Optionally, the material of the standing wave modulation layer includes ALGa. 1-x As x The component X of As is adjusted based on the wavelength of the laser.

[0017] Optionally, the component X of As is greater than 0 and less than or equal to 0.45.

[0018] Optionally, the optical thickness of the standing wave modulation layer is greater than half the lasing wavelength and less than the lasing wavelength;

[0019] The material of the standing wave modulation layer is the same as that of the current diffusion layer.

[0020] Optionally, the active region includes:

[0021] An active layer and an upper space layer and a lower space layer located on opposite sides of the active layer; the lower space layer is closer to the substrate than the upper space layer;

[0022] The types of doped ions in the upper space layer are opposite to those in the lower space layer.

[0023] Optionally, the vertical cavity surface-emitting laser further includes a current-limiting layer located in the second Bragg reflector layer, or in an upper space layer adjacent to the second Bragg reflector layer; the current-limiting layer has an opening for defining the emission region.

[0024] Optionally, the vertical cavity surface-emitting laser further includes multiple current-limiting layers, each corresponding to one of the active regions; the multiple current-limiting layers are respectively located in the upper space layer of the corresponding active regions; each current-limiting layer has an opening for defining the emitting region.

[0025] Optionally, the current limiting layer includes an oxide layer; the oxide layer is an epitaxially grown AlGaAs with a high Al content, and the oxidized region on its outer side forms an insulating aluminum oxide film layer; wherein the unoxidized region forms a light-emitting region for effective current injection.

[0026] According to another aspect of the present invention, a method for fabricating a vertical-cavity surface-emitting laser is provided, for forming a vertical-cavity surface-emitting laser as described in any embodiment of the present invention, comprising:

[0027] Provide substrate;

[0028] An epitaxial basic structure is formed on one side of the substrate, and a standing wave modulation layer is formed in the epitaxial basic structure. The epitaxial basic structure includes multiple active regions, which are stacked along the epitaxial growth direction. The active regions of adjacent layers are connected by tunnel junctions. The standing wave modulation layer is located close to the light-emitting cavity surface of the epitaxial basic structure. The standing wave modulation layer is used to adjust the standing wave distribution of the laser so that the strongest wave peak in the standing wave light field deviates from the light-emitting cavity surface of the epitaxial basic structure.

[0029] A dielectric layer is formed; the dielectric layer is located on the side of the epitaxial basic structure away from the substrate.

[0030] The technical solution provided by this invention introduces a standing wave modulation layer into the structure of a vertical cavity surface-emitting laser. By adjusting the standing wave distribution inside the laser through the standing wave modulation layer, the coupling position between the standing wave and the crystal structure in the device structure is changed. The wave peak between the epitaxial basic structure and the dielectric layer is shifted to the dielectric layer with better tolerance strength, reducing the absorption of photons by the interface state of the epitaxial basic structure, thereby achieving a higher COD threshold and ensuring that the device has a higher power density output.

[0031] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of a vertical cavity surface-emitting laser provided in an embodiment of the present invention;

[0034] Figure 2 This is a partial optical field intensity distribution diagram of a vertical cavity surface-emitting laser provided in the prior art;

[0035] Figure 3 yes Figure 1 Partial optical field intensity distribution diagram of the structure shown;

[0036] Figure 4 This is a schematic diagram of another vertical cavity surface-emitting laser provided in an embodiment of the present invention;

[0037] Figure 5 This is a flowchart of a method for fabricating a vertical cavity surface-emitting laser provided in an embodiment of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0040] As mentioned in the background technology, to achieve higher power density output in VCSELs, the industry has gradually adopted multi-junction structure designs, which connect multiple active regions in series through tunnel junctions to achieve a significant increase in output power. To date, eight-junction and higher VCSEL structures have been developed. However, this also presents VCSELs with the same challenge as edge-emitting devices for the first time: catastrophic optical damage at the cavity surface. For traditional multi-junction VCSEL devices, after the epitaxial growth of the basic structure, due to the interruption of physical materials, there are unbonded dangling bonds on the surface of the basic structure, generating intrinsic defects, i.e., surface states. These states can react with air for oxidation or adsorb other impurities, further increasing the surface state density. This density of states introduces additional energy levels into the bandgap, forming carrier trapping centers. If these centers absorb high levels of light radiation from inside the resonant cavity, the temperature at that point will exceed the melting point of III-V group materials, leading to cavity surface melting. Furthermore, the rapid increase in the laser cavity surface temperature induces bandgap contraction at the cavity surface, promoting photon absorption, exacerbating cavity surface burn-out, and causing catastrophic optical mirror damage, significantly impacting the device's lifespan. Although other dielectric insulating layers can be grown on the surface of the epitaxial base structure during device fabrication to prevent air from contacting the epitaxial base structure, these surface states cannot be completely removed because the epitaxial base structure is already exposed to air. Therefore, surface melting of the device can still occur between the epitaxial base structure and the dielectric layer.

[0041] Therefore, embodiments of the present invention provide a vertical-cavity surface-emitting laser. Figure 1 This is a schematic diagram of a vertical cavity surface-emitting laser provided in an embodiment of the present invention. (Refer to...) Figure 1 Vertical-cavity surface-emitting lasers include:

[0042] Substrate 10;

[0043] The epitaxial basic structure 20 is located on one side of the substrate 10; the epitaxial basic structure 20 includes a plurality of active regions 24, which are stacked along the epitaxial growth direction X; the active regions 24 of adjacent layers are connected by tunnel junctions 23.

[0044] The dielectric layer 30 is located on the side of the epitaxial basic structure 20 away from the substrate 10;

[0045] The standing wave adjustment layer 27 is interspersed in the epitaxial basic structure 20 and disposed close to the dielectric layer 30. The standing wave adjustment layer 27 is used to adjust the standing wave distribution of the laser so that the wave peak in the standing wave light field deviates from the light-emitting cavity surface of the epitaxial basic structure 20. The light-emitting cavity surface is the surface of the epitaxial basic structure 20 away from the substrate 10.

[0046] Specifically, substrate 10 forms the basis for constructing the epitaxial basic structure 20. Substrate 10 can be an N-type doped semiconductor substrate 10 or a P-type doped semiconductor substrate 10. In this embodiment, substrate 10 is an N-type doped semiconductor substrate 10. The material of substrate 10 can be any material suitable for forming a laser, such as gallium arsenide (GaAs). The epitaxial basic structure 20 is located on one side of substrate 10. The semi-epitaxy basic structure 20 includes multiple active regions 24 stacked along the epitaxial growth direction X, and adjacent active regions 24 are connected by tunnel junctions 23. The multiple active regions 24 are connected in series through the tunnel junctions 23 to achieve a significant increase in the output power of the vertical cavity surface-emitting laser. Figure 1 Three active regions 24 are illustrated in the example.

[0047] Each active region 24 may include an active layer 243 and an upper space layer 242 and a lower space layer 241 located on opposite sides of the active layer 243; the lower space layer 241 is closer to the substrate 10 than the upper space layer 242. The dopant ions in the upper space layer 242 are of the opposite type to those in the lower space layer 241. The dopant ions in the lower space layer 241 are of the same type as those in the substrate 10. The active layer 243 is the core of the device and can employ a quantum well structure to convert electrical energy into light energy. The space layers are used to confine the light field, allowing photons and electrons to be simultaneously confined within the quantum well light-emitting region, achieving high quantum efficiency.

[0048] The dielectric layer 30 is located on the side of the epitaxial basic structure 20 away from the substrate 10. Growing the dielectric layer 30 on the surface of the epitaxial basic structure 20 can prevent air from contacting the epitaxial structure and improve the problem of oxidation reaction or adsorption of other impurities on the surface of the epitaxial structure, which increases the surface state density. However, since the epitaxial wafer is already exposed to air, these surface states cannot be completely removed. Therefore, surface melting of the device can still occur between the epitaxial basic structure 20 and the dielectric layer 30.

[0049] Based on this, a standing wave modulation layer 27 is introduced into the epitaxial basic structure 20, and the standing wave modulation layer 27 is disposed close to the dielectric layer 30. By adjusting the thickness of the standing wave modulation layer 27, the wave peaks in the standing wave optical field can be deviated from the light-emitting cavity surface of the epitaxial basic structure 20, reducing the absorption of photons by interface states, thereby improving the device's COD resistance and achieving high power density output. In addition, by adjusting the thickness of the standing wave modulation layer 27, the strongest part of the standing wave can be moved from the interface between the epitaxial basic structure 20 and the dielectric layer 30 to the dielectric layer 30, which has better resistance, preventing melting of other film layer interfaces, thereby achieving a higher COD threshold and higher power density output of the device.

[0050] The vertical-cavity surface-emitting laser (VCSEL) provided in this invention includes: a substrate; an epitaxial basic structure located on one side of the substrate; the epitaxial basic structure includes multiple active regions stacked along the epitaxial growth direction; adjacent active regions are connected by tunnel junctions; a dielectric layer located on the side of the epitaxial basic structure away from the substrate; and a standing-wave modulation layer interspersed within the epitaxial basic structure and disposed close to the dielectric layer. The standing-wave modulation layer is used to adjust the standing-wave distribution of the laser so that the strongest peak in the standing-wave field deviates from the output cavity surface of the epitaxial basic structure; the output cavity surface is the surface of the epitaxial basic structure away from the substrate. By introducing a standing-wave modulation layer into the epitaxial basic structure, the coupling position between the standing wave and the crystal structure in the device structure is changed. The peak between the epitaxial basic structure layer and the dielectric layer can be shifted to the dielectric layer with better tolerance, reducing the absorption of interface states, thereby achieving a higher COD threshold and realizing a higher power density output of the device.

[0051] In one embodiment of the present invention, reference is made to... Figure 1 The basic extensional structure 20 also includes:

[0052] The first Bragg reflector layer 21 is located on one side of the substrate 10; multiple active regions 24 are located on the side of the first Bragg reflector layer 21 away from the substrate 10 and are stacked along the direction perpendicular to the substrate 10.

[0053] The second Bragg reflector layer 22 is located on the side of the active region 24 furthest from the substrate 10.

[0054] The current diffusion layer 26 is located on the side of the second Bragg reflector layer 22 away from the substrate 10;

[0055] Contact layer 28 is located on the side of current diffusion layer 26 away from substrate 10;

[0056] The standing wave conditioning layer 27 is located between the current diffusion layer 26 and the second Bragg reflection layer 22, within the current diffusion layer 26, or between the current diffusion layer 26 and the contact layer 28.

[0057] It can be understood that both the first Bragg reflector layer 21 and the second Bragg reflector layer 22 comprise a series of alternating layers of materials with different refractive indices. Reflection of light is achieved by alternately growing materials with a certain refractive index difference, resulting in a reflectivity of over 99%. The first Bragg reflector layer 21 and the second Bragg reflector layer 22 are used to enhance the reflection of light generated by the active layer 243 in the middle, which is then emitted from the surface of the second Bragg reflector layer 22 to form a laser. For example, both the first Bragg reflector layer 21 and the second Bragg reflector layer 22 are composed of stacked layers of materials with different refractive indices, including aluminum gallium arsenide (AGaAs) and gallium arsenide (GaAs), or stacked layers of materials with different refractive indices, including AGaAs with a high aluminum content and AGaAs with a low aluminum content. In some embodiments, the first Bragg reflector layer 21 and the second Bragg reflector layer 22 may also be formed of other materials.

[0058] Wherein, if the first Bragg reflector layer 21 is an N-type Bragg reflector, then the second Bragg reflector layer 22 is a P-type Bragg reflector. If the first Bragg reflector layer 21 is a P-type Bragg reflector, then the second Bragg reflector layer 22 is an N-type Bragg reflector. The doping type of the first Bragg reflector layer 21 is the same as the doping type of the substrate 10. The elements doped in the P-type Bragg reflector include carbon, and the elements doped in the N-type Bragg reflector include at least one of tellurium, silicon, and germanium. The effective optical thickness of each alternating layer (the layer thickness multiplied by the layer refractive index) is an odd integer multiple of one-quarter of the operating wavelength of the vertical-cavity surface-emitting laser, that is, the effective optical thickness of each alternating layer is one-quarter of an odd integer multiple of the operating wavelength of the vertical-cavity surface-emitting laser.

[0059] The current diffusion layer 26 is located on the side of the second Bragg reflector layer 22 away from the substrate 10. The diffusion direction of the current in the current diffusion layer 26 is parallel to the substrate 10, and high doping is used to achieve uniform dispersion of the injected current at various locations of the device. The main function of the current diffusion layer 26 is to provide lateral conductivity. The current diffusion layer 26 is exposed during the laser device manufacturing process and connected to the electrodes. The lateral conductivity of the current diffusion layer 26 is crucial, affecting not only the performance indicators of the laser device but also the luminous uniformity, heat generation, and reliability of the laser array. If the conductivity of the current diffusion layer 26 is poor, not only will the luminous efficiency of the laser device decrease, but the luminous uniformity of the laser array will also deteriorate. Therefore, it is necessary to ensure the conductivity of the current diffusion layer 26. The conductivity of the current diffusion layer 26 can be improved by increasing its thickness or increasing the doping concentration.

[0060] Contact layer 28 is located on the side of current diffusion layer 26 away from substrate 10; contact layer 28 is used to form a contact ohmic contact with the metal electrode. The surface of contact layer 28 away from the substrate is the light-emitting cavity surface of the epitaxial basic structure 20. After the growth of contact layer 28 is completed, due to the interruption of physical materials, there are dangling bonds that have not yet formed on the surface of contact layer 28, generating intrinsic defects, i.e., surface states. These states will undergo oxidation reactions with air or adsorb other impurities to further increase the surface state density. These state densities will introduce additional energy levels in the band gap, forming carrier trapping centers. If they absorb high light radiation from inside the resonant cavity, the temperature at that point will exceed the melting point of group III-V materials, resulting in cavity surface melting.

[0061] For vertical-cavity surface-emitting semiconductor lasers (VCSELs), after sufficient injection current is applied, a stable standing wave is formed inside the device cavity, thus achieving lasing. The intensity of the formed standing wave is not uniformly distributed within the cavity, resulting in different electric field intensities at different locations. Therefore, by adjusting the standing wave distribution, the peak with the strongest energy distribution can be shifted away from the material interface, preventing the interface from excessively absorbing high-level light radiation within the resonant cavity, thereby improving the device's COD performance. In this embodiment, a standing wave adjustment layer 27 is provided between the current diffusion layer 26 and the second Bragg reflector layer 22, within the current diffusion layer 26, or between the current diffusion layer 26 and the contact layer 28. By adjusting the thickness of the standing wave adjustment layer 27, the strongest portion of the standing wave can be shifted from the interface between the epitaxial basic structure 20 and the dielectric layer 30 to the dielectric layer 30, which has better resistance, preventing melting of other film interfaces and achieving a higher COD threshold, resulting in higher power density output of the device. Figure 1 An example is drawn showing the standing wave modulation layer 27 located between the current diffusion layer 26 and the contact layer 28.

[0062] Figure 2 This is a partial optical field intensity distribution diagram of a vertical-cavity surface-emitting laser provided in the prior art, for reference. Figure 2 Curve 11 represents the standing wave distribution, while film layer 1 and film layer 2 represent alternating layers of high and low refractive indices in the second Bragg reflector layer of the VCSEL. For example... Figure 2 As shown, the standing wave intensity between contact layer 28 and dielectric layer 30 is equal to the standing wave intensity between dielectric layer 30 and air, indicating that the electromagnetic field intensity at the interface between contact layer 28 and dielectric layer 30 is consistent with that at the interface between dielectric layer 30 and air. However, when surface dangling bonds exist at the interface between contact layer 28 and dielectric layer 30, COD will first occur at this point, ultimately limiting further improvement in the device's COD threshold. Figure 3 yes Figure 1 Partial light field intensity distribution of the structure shown, compared with Figure 3 and Figure 2A standing wave modulation layer 27 was incorporated as an anti-COD structure during the epitaxial growth process. By adjusting the thickness of this layer 27, the strongest portion of the standing wave can be shifted from the interface between the contact layer 28 and the dielectric layer 30 to the dielectric layer 30. The optical field intensity at the interface between the contact layer 28 and the dielectric layer 30 is much lower than that in the dielectric layer 30 and at the interface between the dielectric layer 30 and air. Therefore, under the same output power conditions, applying the strongest electric field peak to the more resilient dielectric layer 30 can significantly improve the COD threshold of the laser.

[0063] The material of the standing wave modulation layer 27 may include ALGa 1-x As x The composition X of As is adjusted based on the laser wavelength. The composition X of As is greater than 0 and less than or equal to 0.45. The optical thickness of the standing wave conditioning layer 27 is greater than half the lasing wavelength and less than the lasing wavelength. The material of the current diffusion layer 26 can be the same as the material of the standing wave conditioning layer 27.

[0064] In one embodiment of the present invention, reference is made to... Figure 1 The epitaxial basic structure 20 also includes a current confinement layer 25, which is located in the second Bragg reflector layer 22, or in the upper space layer 242 adjacent to the second Bragg reflector layer 22. Figure 1 An example is drawn where the current limiting layer 25 is located in the second Bragg reflector layer 22.

[0065] This can be understood as follows: the current-limiting layer includes an oxide layer; the oxide layer is epitaxially grown high-Al content AlGaAs, and the oxidized region on its outer side forms an insulating aluminum oxide film; the unoxidized region forms the light-emitting region for effective current injection. The sidewalls of the epitaxial basic structure 20 are oxidized by wet oxidation of highly aluminum-doped material under certain temperature conditions, forming a current-limiting layer 25 in the second Bragg reflector layer 22. The current-limiting layer 25 has an opening 251, which is the unoxidized region. The oxidized aluminum oxide has high impedance, and the opening 251 of the current-limiting layer 25 is still a highly aluminum-doped AlGaAs material. The incoming current flows through the opening 251 to the active layer 243. The current-limiting layer 25 can limit the direction of current flow, reducing power loss. Additionally, the opening 251 also defines the light-emitting region of the laser, from which the laser emits light. The opening 251 of the current-limiting layer 25 can be circular or rectangular.

[0066] In another embodiment of the invention, reference is made to... Figure 4The epitaxial basic structure 20 may include multiple current limiting layers 25, each of which is configured in a one-to-one correspondence with an active region 24. The multiple current limiting layers 25 are located in the upper space layer 242 of the corresponding active region 24, thereby further limiting the current and reducing power loss.

[0067] This invention also provides a method for fabricating a vertical-cavity surface-emitting laser (VCSEL), used to form the VCSEL described in any of the above embodiments. Figure 5 This is a flowchart illustrating a method for fabricating a vertical-cavity surface-emitting laser according to an embodiment of the present invention. (Refer to...) Figure 5 Methods for fabricating vertical-cavity surface-emitting lasers include:

[0068] S110 provides a substrate.

[0069] Specifically, the substrate is the basis for constructing the basic epitaxial structure. The substrate can be an N-type doped semiconductor substrate or a P-type doped semiconductor substrate. In this embodiment, the substrate is an N-type doped semiconductor substrate. The substrate material can be any material suitable for forming a laser, such as gallium arsenide.

[0070] S120. An epitaxial basic structure is formed on one side of the substrate, and a standing wave adjustment layer is formed in the epitaxial basic structure. The epitaxial basic structure includes multiple active regions, which are stacked along the epitaxial growth direction. The active regions of adjacent layers are connected by a tunnel junction. The standing wave adjustment layer is located close to the light output cavity surface of the epitaxial basic structure. The standing wave adjustment layer is used to adjust the standing wave distribution of the laser so that the strongest wave peak in the standing wave light field deviates from the light output cavity surface of the epitaxial basic structure.

[0071] Specifically, the epitaxial basic structure is located on one side of the substrate. The semi-epitaxy basic structure includes multiple active regions stacked along the epitaxial growth direction, and the active regions of adjacent layers are connected by tunnel junctions. The multiple active regions are connected in series through the tunnel junctions to achieve a significant increase in the output power of the vertical cavity surface-emitting laser. Each active region may include an active layer and an upper space layer and a lower space layer located on opposite sides of the active layer; the lower space layer is closer to the substrate than the upper space layer.

[0072] The basic epitaxial structure also includes: a first Bragg reflector layer located on one side of the substrate; multiple active regions located on the side of the first Bragg reflector layer away from the substrate and stacked along the direction perpendicular to the substrate; a second Bragg reflector layer located on the side of the active region furthest from the substrate; a current diffusion layer located on the side of the second Bragg reflector layer away from the substrate; a contact layer located on the side of the current diffusion layer away from the substrate; wherein, the standing wave modulation layer is located between the current diffusion layer and the second Bragg reflector layer, within the current diffusion layer, or between the current diffusion layer and the contact layer.

[0073] Taking an epitaxial basic structure comprising three active regions and a standing wave modulation layer located between the current diffusion layer and the contact layer as an example, during the fabrication of the epitaxial basic structure, a first Bragg reflection layer, a first active region, a first tunnel layer, a second active region, a second tunnel layer, a third active region, a second Bragg reflection layer, a current diffusion layer, a standing wave modulation layer, and a contact layer are sequentially formed on the substrate along a direction perpendicular to the substrate.

[0074] S130, Form a dielectric layer, which is located on the side of the epitaxial basic structure away from the substrate.

[0075] Specifically, growing a dielectric layer on the surface of the epitaxial base structure can block contact between air and the epitaxial structure, mitigating the problem of oxidation reactions or adsorption of other impurities that increase surface state density. Furthermore, by introducing a standing wave modulation layer into the epitaxial base structure, the coupling position between the standing wave and the crystal structure is altered. This shifts the wave peak between the epitaxial base structure layer and the dielectric layer to the dielectric layer, which has better resistance, reducing interface state absorption and thus achieving a higher COD threshold, resulting in higher power density output from the device.

[0076] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, include: Substrate; An epitaxial basic structure is located on one side of the substrate; the epitaxial basic structure includes multiple active regions, which are stacked along the epitaxial growth direction; the active regions of adjacent layers are connected by tunnel junctions; A dielectric layer is located on the side of the epitaxial basic structure away from the substrate; A standing wave adjustment layer is interspersed in the epitaxial basic structure and disposed close to the dielectric layer; the standing wave adjustment layer is used to adjust the standing wave distribution in the vertical cavity surface-emitting laser so that the wave peaks in the standing wave light field deviate from the light-emitting cavity surface of the epitaxial basic structure; wherein the light-emitting cavity surface is the surface of the epitaxial basic structure away from the substrate.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The basic epitaxial structure also includes: A first Bragg reflector layer is located on one side of the substrate; the plurality of active regions are all located on the side of the first Bragg reflector layer away from the substrate; The second Bragg reflector layer is located on the side of the active region furthest from the substrate. A current diffusion layer is located on the side of the second Bragg reflector layer away from the substrate; A contact layer is located on the side of the current diffusion layer away from the substrate; The standing wave modulation layer is located between the current diffusion layer and the second Bragg reflection layer, within the current diffusion layer, or between the current diffusion layer and the contact layer.

3. The vertical-cavity surface-emitting laser according to claim 2, characterized in that, The material of the standing wave modulation layer includes AlGa. 1-x As x The component X of As is adjusted based on the wavelength of the laser.

4. The vertical-cavity surface-emitting laser according to claim 3, characterized in that, The component X of As is greater than 0 and less than or equal to 0.

45.

5. The vertical-cavity surface-emitting laser according to claim 3, characterized in that, The optical thickness of the standing wave modulation layer is greater than half the lasing wavelength and less than the lasing wavelength. The material of the standing wave modulation layer is the same as that of the current diffusion layer.

6. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The active region includes: An active layer and an upper space layer and a lower space layer located on opposite sides of the active layer; the lower space layer is closer to the substrate than the upper space layer; The types of doped ions in the upper space layer are opposite to those in the lower space layer.

7. The vertical-cavity surface-emitting laser according to claim 6, characterized in that, It also includes a current-limiting layer; the current-limiting layer is located in the second Bragg reflector layer, or in the upper space layer adjacent to the second Bragg reflector layer; the current-limiting layer has an opening for defining the light-emitting area.

8. The vertical-cavity surface-emitting laser according to claim 6, characterized in that, It also includes multiple current-limiting layers; each current-limiting layer corresponds one-to-one with the active region; each current-limiting layer is located in the upper space layer of the corresponding active region; each current-limiting layer has an opening, which is used to define the light-emitting region.

9. The vertical-cavity surface-emitting laser according to claim 7 or 8, characterized in that, The current limiting layer includes an oxide layer; the oxide layer is an epitaxially grown AlGaAs with a high Al content, and the outer oxidized region forms an insulating aluminum oxide film layer; wherein, the unoxidized region forms a light-emitting region for effective current injection.

10. A method for fabricating a vertical-cavity surface-emitting laser, characterized in that, For forming a vertical cavity surface-emitting laser according to any one of claims 1 to 9, comprising: Provide substrate; An epitaxial basic structure is formed on one side of the substrate, and a standing wave modulation layer is formed in the epitaxial basic structure. The epitaxial basic structure includes multiple active regions, which are stacked along the epitaxial growth direction. The active regions of adjacent layers are connected by tunnel junctions. The standing wave modulation layer is located close to the light-emitting cavity surface of the epitaxial basic structure. The standing wave modulation layer is used to adjust the standing wave distribution of the laser so that the strongest wave peak in the standing wave light field deviates from the light-emitting cavity surface of the epitaxial basic structure. A dielectric layer is formed on the side of the epitaxial basic structure away from the substrate.

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