Vertical cavity surface emitting laser, preparation method thereof and optical equipment

Abstract

The invention discloses a vertical cavity surface emitting laser, a preparation method thereof and optical equipment. The vertical cavity surface emitting laser comprises an active area and a distributed Bragg reflector located on at least one side of the active area. The distributed Bragg reflector comprises a plurality of first refractive index layers, a plurality of second refractive index layers and a plurality of aluminum component gradient layers; the first refractive index layers and the second refractive index layers are alternately stacked, and the refractive index of the first refractive index layers is greater than that of the second refractive index layers; the aluminum component gradient layer is located between the first refractive index layer and the second refractive index layer, and the aluminum component of the aluminum component gradient layer is increased nonlinearly in the first direction; the first direction is the direction in which the first refractive index layer points to the second refractive index layer. According to the vertical cavity surface emitting laser, the aluminum component gradient layer with the nonlinearly increased aluminum component is arranged between the first refractive index layer and the second refractive index layer which are alternately stacked, so that the resistance of the vertical cavity surface emitting laser can be reduced.

Description

Technical Field

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

[0002] In order for a vertical cavity surface-emitting laser to achieve lasing at a low threshold, the mirrors on both sides need to have high reflectivity.

[0003] A reflector is made of alternating stacks of different materials. To increase the reflectivity of a reflector, one can either increase the difference between the two materials with different refractive indices or increase the number of periods in the reflector.

[0004] However, both of these methods will increase the resistance of the device and generate a lot of heat, eventually leading to excessively high device temperature and reduced output power. Summary of the Invention

[0005] This invention provides a vertical cavity surface-emitting laser, its fabrication method, and optical equipment to solve the problem of high resistance in existing vertical cavity surface-emitting lasers with high-reflectivity mirrors.

[0006] In a first aspect, embodiments of the present invention provide a vertical cavity surface-emitting laser, including an active region and a distributed Bragg reflector located on at least one side of the active region;

[0007] The distributed Bragg reflector includes multiple first refractive index layers, multiple second refractive index layers, and multiple aluminum composition gradient layers; the first refractive index layers and the second refractive index layers are alternately stacked, and the refractive index of the first refractive index layer is greater than that of the second refractive index layer; the aluminum composition gradient layer is located between the first refractive index layers and the second refractive index layers, and the aluminum composition of the aluminum composition gradient layer increases nonlinearly along a first direction; the first direction is the direction from the first refractive index layer to the second refractive index layer.

[0008] Optionally, along the first direction, the rate of increase of the aluminum composition in the aluminum composition gradient layer decreases.

[0009] Optionally, the aluminum composition gradient layer includes Al (x) Ga (1-x) As;

[0010] The aluminum composition x at any position in the aluminum composition gradient layer satisfies the following correspondence:

[0011] x = -0.002 × z 2 +0.04×z+0.7;

[0012] Where z represents the distance between any position in the aluminum composition gradient layer and the reference position in the first direction, and the reference position is the center of the aluminum composition gradient layer; and z is positive when any position is located on the side of the reference position close to the second refractive index layer in contact with the aluminum composition gradient layer, and z is negative when any position is located on the side of the reference position close to the first refractive index layer in contact with the aluminum composition gradient layer.

[0013] Optionally, the first refractive index layer includes Al (a) Ga (1-a) As; the second refractive index layer includes Al (b) Ga (1-b) As;

[0014] The aluminum composition x at any position in the aluminum composition gradient layer satisfies: a≤x≤b;

[0015] Where a represents the aluminum composition of the first refractive index layer, b represents the aluminum composition of the second refractive index layer, a < b, a ≥ 0, b ≤ 1.

[0016] Optionally, the thickness w1 of the aluminum component gradient layer satisfies: 10nm ≤ w1 ≤ 30nm.

[0017] Optionally, the vertical-cavity surface-emitting laser further includes a substrate; the distributed Bragg reflector includes a first distributed Bragg reflector and a second distributed Bragg reflector; the first distributed Bragg reflector is located on the side of the active region closer to the substrate; the second distributed Bragg reflector is located on the side of the active region away from the substrate;

[0018] The first refractive index layer includes a first refractive index layer A and a first refractive index layer B, the second refractive index layer includes a second refractive index layer A and a second refractive index layer B, and the aluminum composition gradient layer includes a first aluminum composition gradient layer and a second aluminum composition gradient layer.

[0019] The first distributed Bragg reflector includes multiple first α-refractive index layers, multiple second α-refractive index layers, and multiple first aluminum composition graded layers; the second distributed Bragg reflector includes multiple first β-refractive index layers, multiple second β-refractive index layers, and multiple second aluminum composition graded layers.

[0020] Optionally, the first distributed Bragg reflector includes an n-type distributed Bragg reflector;

[0021] The second distributed Bragg reflector includes a p-type distributed Bragg reflector.

[0022] Optionally, the active region includes a stacked quantum well, an oxide layer, and a tunnel junction; the vertical-cavity surface-emitting laser also includes a substrate;

[0023] The oxide layer is located on the side of the quantum well away from the substrate;

[0024] The tunnel junction is located on the side of the oxide layer away from the substrate.

[0025] In a second aspect, embodiments of the present invention provide a method for fabricating a vertical-cavity surface-emitting laser (VCSEL), used to fabricate the VCSEL as described in the first aspect, the fabrication method comprising:

[0026] Preparation of active regions;

[0027] A distributed Bragg reflector is fabricated on at least one side of the active region. The distributed Bragg reflector includes a plurality of first refractive index layers, a plurality of second refractive index layers, and a plurality of aluminum composition gradient layers. The first refractive index layers and the second refractive index layers are alternately stacked, and the refractive index of the first refractive index layer is greater than that of the second refractive index layer. The aluminum composition gradient layers are located between the first refractive index layers and the second refractive index layers, and the aluminum composition of the aluminum composition gradient layers increases nonlinearly along a first direction. The first direction is the direction from the first refractive index layer to the second refractive index layer.

[0028] Thirdly, embodiments of the present invention provide an optical device, characterized in that it includes the vertical cavity surface-emitting laser described in the first aspect.

[0029] The technical solution of this invention provides an aluminum composition gradient layer with a nonlinearly increasing aluminum composition between the alternatingly stacked first and second refractive index layers. This reduces the interface barrier between the first and second refractive index layers, thereby reducing the resistance of the vertical cavity surface-emitting laser (VCSEL), reducing the heat generation of the VCSEL, avoiding damage to the VCSEL due to excessive temperature, and improving the output power of the VCSEL.

[0030] 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

[0031] 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.

[0032] Figure 1 A schematic diagram of a vertical cavity surface-emitting laser provided in an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the aluminum composition distribution of a distributed Bragg reflector provided for the prior art;

[0034] Figure 3 A schematic diagram of aluminum composition distribution for a distributed Bragg reflector provided for reference in the prior art and embodiments of the present invention;

[0035] Figure 4 The diagram shows the conduction band energy level distribution of an existing n-type distributed Bragg reflector and the first distributed Bragg reflector in this embodiment of the invention.

[0036] Figure 5 The diagram shows the valence band energy level distribution of an existing p-type distributed Bragg reflector and the second distributed Bragg reflector in this embodiment of the invention.

[0037] Figure 6 A schematic diagram of another vertical cavity surface-emitting laser provided in an embodiment of the present invention;

[0038] Figure 7 A flowchart illustrating a method for fabricating a vertical-cavity surface-emitting laser (VCSEL) according to an embodiment of the present invention;

[0039] Figure 8 This is a schematic diagram of the structure of an optical device provided in an embodiment of the present invention. Detailed Implementation

[0040] 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.

[0041] 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 non-exclusive inclusion; for example, a process, method, system, product, or device 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 devices. The terms "upper," "lower," "left," "right," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings and are only used to describe the relative positional relationships between components or constituent parts, and do not specifically limit the specific installation orientation of each component or constituent part.

[0042] Figure 1 This is a schematic diagram of a vertical cavity surface-emitting laser provided in an embodiment of the present invention, with reference to... Figure 1 The vertical-cavity surface-emitting laser (VCSEL) in this embodiment of the invention includes an active region 10 and a distributed Bragg reflector 20 located on at least one side of the active region 10. The distributed Bragg reflector 20 includes a plurality of first refractive index layers 201, a plurality of second refractive index layers 202, and a plurality of aluminum composition graded layers 203. The first refractive index layers 201 and second refractive index layers 202 are alternately stacked, and the refractive index of the first refractive index layers 201 is greater than the refractive index of the second refractive index layers 202. The aluminum composition graded layers 203 are located between the first refractive index layers 201 and the second refractive index layers 202, and the aluminum composition of the aluminum composition graded layers 203 increases non-linearly along a first direction. The first direction is the direction from the first refractive index layers 201 to the second refractive index layers 202.

[0043] For example, the distributed Bragg reflector 20 can be fabricated using aluminum gallium arsenide or gallium arsenide semiconductor materials. In this embodiment, the active region 10 can be sandwiched between two distributed Bragg reflectors 20 to form a resonant cavity. Different types of charge carriers (electrons and holes) recombine in the active region 10 to generate photons. After being excited, the photons can be repeatedly amplified by reflection within the resonant cavity to form laser light. The alternately stacked first refractive index layer 201 and second refractive index layer 202 can be fabricated using aluminum gallium arsenide. In this embodiment, the aluminum composition of the first refractive index layer 201 is less than that of the second refractive index layer 202. It is understood that the aluminum composition of the refractive index layer is inversely proportional to the refractive index of the refractive index layer; therefore, the refractive index of the first refractive index layer 201 is greater than that of the second refractive index layer 202.

[0044] The series resistance of the distributed Bragg reflector 20 mainly comes from the barrier peak at the interface of the homo-heterojunction. The heterojunction is formed by the close contact of two semiconductor materials. In the homo-heterojunction, one side is generally the depletion layer, while the other side becomes the carrier accumulation layer.

[0045] In this embodiment of the invention, by setting an aluminum composition gradient layer 203 with a nonlinearly increasing aluminum composition between the alternatingly stacked first refractive index layer 201 and second refractive index layer 202, the interface barrier between the first refractive index layer 201 and the second refractive index layer 202 can be reduced. This helps to reduce the resistance of the vertical cavity surface-emitting laser 100, reduce the heat generation of the vertical cavity surface-emitting laser 100, avoid damage to the vertical cavity surface-emitting laser 100 due to excessive temperature, and also helps to improve the output power of the vertical cavity surface-emitting laser 100.

[0046] As one possible implementation, the vertical-cavity surface-emitting laser 100 further includes a substrate 30. The distributed Bragg reflector 20 includes a first distributed Bragg reflector 21 and a second distributed Bragg reflector 22. The first distributed Bragg reflector 21 is located on the side of the active region 10 closest to the substrate 30. The second distributed Bragg reflector 22 is located on the side of the active region 10 furthest from the substrate 30. The first refractive index layer 201 includes a first α refractive index layer 201A and a first β refractive index layer 201B; the second refractive index layer 202 includes a second α refractive index layer 202A and a second β refractive index layer 202B; and the aluminum composition graded layer 203 includes a first aluminum composition graded layer 203A and a second aluminum composition graded layer 203B. The first distributed Bragg reflector 21 includes a plurality of first α refractive index layers 201A, a plurality of second α refractive index layers 202A, and a plurality of first aluminum composition graded layers 203A. The second distributed Bragg reflector 22 includes multiple first ethyl refractive index layers 201B, multiple second ethyl refractive index layers 202B, and multiple second aluminum composition gradient layers 203B.

[0047] Specifically, the first distributed Bragg reflector 21 includes an n-type distributed Bragg reflector 20. The second distributed Bragg reflector 22 includes a p-type distributed Bragg reflector 20.

[0048] For example, the substrate 30 of the vertical-cavity surface-emitting laser 100 in this embodiment of the invention can be a conductive substrate, a semi-insulating substrate, or an insulating substrate. This embodiment of the invention does not limit the specific substrate, and those skilled in the art can make their own settings. The first distributed Bragg reflector 21 can be made of N-type doped aluminum gallium arsenide or gallium arsenide and other semiconductor materials, and the second distributed Bragg reflector 22 can be made of P-type doped aluminum gallium arsenide or gallium arsenide and other semiconductor materials.

[0049] In this embodiment of the invention, the first methyl methacrylate layer 201A and the second methyl methacrylate layer 202A in the first distributed Bragg reflector 21 are stacked alternately, and the refractive index of the first methyl methacrylate layer 201A is greater than that of the second methyl methacrylate layer 202A. The optical thickness of the first methyl methacrylate layer 201A and the second methyl methacrylate layer 202A is λ / 4, where λ refers to the target center wavelength of the first distributed Bragg reflector 21 (i.e., the specific wavelength that requires high reflectivity, usually consistent with the emission or operating wavelength of the vertical cavity surface-emitting laser 100). It can be understood that the series resistance of the first distributed Bragg reflector 21 mainly originates from the barrier peak at the interface of the homojunction. For the homojunction of the n-type first distributed Bragg reflector 21, the Fermi level of the second methylform refractive index layer 202A with a large bandgap (large Al composition) is higher than that of the first methylform refractive index layer 201A with a small bandgap (small Al composition). Electrons will flow from the former to the latter, resulting in the formation of an electron accumulation layer on the side with a small bandgap and an electron depletion layer on the side with a large bandgap, thus forming an electron barrier. By setting a first aluminum composition gradient layer 203A with a nonlinearly increasing aluminum composition between the first methylform refractive index layer 201A and the second methylform refractive index layer 202A, the interface barrier between the first methylform refractive index layer 201A and the second methylform refractive index layer 202A can be reduced, which is beneficial to reducing the series resistance of the first distributed Bragg reflector 21 and improving the photoelectric performance of the vertical cavity surface-emitting laser 100.

[0050] In this embodiment of the invention, the first ethyl refractive index layer 201B and the second ethyl refractive index layer 202B are alternately stacked in the second distributed Bragg reflector 22, and the refractive index of the first ethyl refractive index layer 201B is greater than the refractive index of the second ethyl refractive index layer 202B. The optical thickness of the first ethyl refractive index layer 201B and the second ethyl refractive index layer 202B is λ / 4, where λ refers to the target center wavelength of the second distributed Bragg reflector 22 (i.e., the specific wavelength that requires high reflectivity, usually consistent with the emission or operating wavelength of the vertical cavity surface-emitting laser 100). It can be understood that the series resistance of the second distributed Bragg reflector 22 mainly originates from the barrier peak at the interface of the homojunction. For the homojunction of the p-type second distributed Bragg reflector 22, the Fermi level of the second ethyl refractive index layer 202B, which has a large bandgap (large Al composition), is lower than that of the first ethyl refractive index layer 201B, which has a small bandgap (small Al composition). Holes will flow from the former to the latter, resulting in the formation of a hole accumulation layer on the side of the first ethyl refractive index layer 201B with a small bandgap, and a hole depletion layer on the side with a large bandgap, thus forming a hole barrier. By setting a second aluminum composition gradient layer 203B with a nonlinearly increasing aluminum composition between the first ethyl refractive index layer 201B and the second ethyl refractive index layer 202B, the interface barrier between the first ethyl refractive index layer 201B and the second ethyl refractive index layer 202B can be reduced, which is beneficial to reducing the series resistance of the second distributed Bragg reflector 22 and improving the photoelectric performance of the vertical cavity surface-emitting laser 100.

[0051] As a feasible implementation method, the rate of increase of aluminum composition in the aluminum composition gradient layer 203 decreases along the first direction.

[0052] For example, in the first distributed Bragg reflector 21, the aluminum composition of the first aluminum composition gradient layer 203A changes faster near the low aluminum composition layer (i.e., the first methyl refractive index layer 201A), and the aluminum composition of the first aluminum composition gradient layer 203A changes slower near the high aluminum composition layer (i.e., the second methyl refractive index layer 202A). It should be noted that the specific numerical value of the rate of change of the aluminum composition of the first aluminum composition gradient layer 203A in the first distributed Bragg reflector 21 is not limited in this embodiment of the invention; those skilled in the art can set it themselves.

[0053] In the second distributed Bragg reflector 22, the aluminum composition of the first aluminum composition gradient layer 203A changes faster near the low-aluminum composition layer (i.e., the first ethyl refractive index layer 201B), and slower near the high-aluminum composition layer (i.e., the second ethyl refractive index layer 202B). It should be noted that this embodiment of the invention does not limit the specific numerical value of the rate of change of the aluminum composition of the second aluminum composition gradient layer 203B in the second distributed Bragg reflector 22; those skilled in the art can set it themselves.

[0054] Specifically, the aluminum composition gradient layer 203 (first aluminum composition gradient layer 203A or second aluminum composition gradient layer 203B) in this embodiment of the invention includes Al (x) Ga (1-x) As. The aluminum composition x at any position in the aluminum composition gradient layer 203 satisfies the following correspondence:

[0055] x = -0.002 × z 2 +0.04×z+0.7.

[0056] Here, z represents the distance between any position in the aluminum composition gradient layer 203 and the reference position in the first direction, where the reference position is the center of the aluminum composition gradient layer 203. Furthermore, z is positive when any position is located near the reference position on the side close to the second refractive index layer 202 that contacts the aluminum composition gradient layer 203, and negative when any position is located near the reference position on the side close to the first refractive index layer 201 that contacts the aluminum composition gradient layer 203.

[0057] It should be noted that the first refractive index layer 201 includes Al (a) Ga (1-a) As. The second refractive index layer 202 includes Al. (b) Ga (1-b) As. The aluminum composition x at any position in the aluminum composition gradient layer 203 satisfies: a≤x≤b; where a represents the aluminum composition of the first refractive index layer 201, b represents the aluminum composition of the second refractive index layer 202, a<b, a≥0, b≤1.

[0058] For example, in the embodiments of the present invention, the aluminum composition of the first refractive index layer 201 can be 0.1, the aluminum composition of the second refractive index layer 202 can be 0.9, and the aluminum composition x at any position in the aluminum composition gradient layer 203 satisfies: 0.1≤x≤0.9.

[0059] refer to Figure 1 In this embodiment of the invention, the thickness w1 of the aluminum component gradient layer 203 satisfies: 10nm≤w1≤30nm.

[0060] It should be noted that the thickness range of the aluminum composition gradient layer 203 is not limited in the embodiments of the present invention. It can also be other ranges other than 10nm to 30nm. Those skilled in the art can set it according to the actual situation.

[0061] Figure 2 A schematic diagram of the aluminum composition distribution of a distributed Bragg reflector provided for the prior art is shown in Figure 2. The existing distributed Bragg reflector includes alternating stacked high refractive index layers and low refractive index layers, and an aluminum composition gradient layer 203 with linearly varying aluminum composition located between the high refractive index layers and the low refractive index layers.

[0062] Figure 3 A schematic diagram of the aluminum composition distribution of a distributed Bragg reflector provided for the prior art and embodiments of the present invention should be noted. Figure 3 S1 in the text refers to the distributed Bragg reflector in the prior art (i.e., Figure 2 The aluminum composition variation curve of the distributed Bragg reflector shown in Figure 1 shows that the aluminum composition gradient layer satisfies the following relationship: x = 0.1 + 0.04 × (z + 10); S2 represents the aluminum composition variation curve of another distributed Bragg reflector in the prior art, whose aluminum composition gradient layer satisfies the following relationship: x = 0.002 × z 2 +0.04×z+0.3; S2 represents the distributed Bragg reflector 20 in this embodiment of the invention (i.e. Figure 1 The aluminum composition variation curve of the distributed Bragg reflector 20) shown shows that its aluminum composition gradient layer 203 satisfies the following correspondence: x = -0.002 × z 2 +0.04×z+0.7. It should be noted that, in this embodiment of the invention, taking the center of the aluminum composition gradient layer 203 as the origin z=0 position and the thickness of the aluminum composition gradient layer 203 as 20nm, the position of the aluminum composition gradient layer 203 satisfies -10≤z≤10, the position of the low aluminum composition layer (i.e., the first refractive index layer 201) satisfies z≤-10, and the position of the high aluminum composition layer (i.e., the second refractive index layer 202) satisfies z≥10.

[0063] refer to Figure 3By combining the function with the image, the relationship between aluminum composition and position (dx / dz) can be clearly understood. In the prior art, the slope of the function corresponding to the aluminum composition gradient layer in the distributed Bragg reflector is always 0.4, which is independent of position. In another prior art, the slope of the function corresponding to the aluminum composition gradient layer in the distributed Bragg reflector is 0.004×z+0.004. In the embodiment of this invention, the slope of the function corresponding to the aluminum composition gradient layer 203 of the distributed Bragg reflector 20 is -0.004×z+0.004. The aluminum composition increase rate (dx / dz) is large on the side closer to the low aluminum composition layer (i.e., the first refractive index layer 201), while the aluminum composition increase rate (dx / dz) is small on the side closer to the high aluminum composition layer (i.e., the second refractive index layer 202).

[0064] The present invention example calculates based on the Poisson equation. Figure 3 The energy level distributions of the conduction and valence bands at the interface of three different distributed Bragg reflector structures in an n-type distributed Bragg reflector are shown below. Figure 4 The diagram shows the conduction band energy level distribution. Figure 4 The diagram shows the conduction band energy level distribution of an existing n-type distributed Bragg reflector and the first distributed Bragg reflector in this embodiment of the invention. Figure 4 S4 in the text refers to an n-type distributed Bragg reflector in the prior art (i.e., such as...). Figure 2 and Figure 3 The conduction band energy level distribution curve of the distributed Bragg reflector shown in S1 is shown in Figure 5. S5 represents another prior art n-type distributed Bragg reflector (i.e., as shown in Figure 6). Figure 3 The conduction band energy level distribution curve of the distributed Bragg reflector shown in S2 is shown in Figure 2. S6 represents the n-type first distributed Bragg reflector 21 in this embodiment of the invention (i.e., as shown in Figure 2). Figure 3 The conduction band energy level distribution curve of the distributed Bragg reflector 20 shown in S3.

[0065] refer to Figure 3 and Figure 4 As can be seen, for an n-type distributed Bragg reflector with an aluminum composition graded layer satisfying the following correspondence: x = 0.1 + 0.04 × (z + 10), there is a significant barrier peak at the boundary z = ±10 nm of the aluminum composition graded layer, and its position is symmetrical about the midpoint. For the aluminum composition graded layer satisfying the following correspondence: x = 0.002 × z 2 For an n-type distributed Bragg reflector with +0.04×z+0.3, the downward potential barrier peak is flattened because the aluminum composition gradient layer changes slowly near the lower aluminum composition layer. The aluminum composition gradient layer 203 satisfies the following correspondence: x=-0.002×z 2For the n-type distributed Bragg reflector 20 with +0.04×z+0.7, the aluminum composition changes slowly on the high-aluminum composition layer (i.e., the second refractive index layer 202), causing the upward potential barrier peak on that side to be flattened. This results in the following correspondence with the aluminum composition graded layer: x=0.002×z 2 For an n-type distributed Bragg reflector with a potential of +0.04×z+0.3, there will be a significant reduction. For electrons, the energy decreases further down the conduction band. Therefore, downward potential barrier peaks represent low-energy electron regions, where electron accumulation is more likely, resulting in less resistance to electron migration. Conversely, upward potential barrier peaks represent electron depletion regions, significantly hindering electron migration. The n-type first distributed Bragg reflector 21 in this embodiment can effectively reduce upward potential barrier peaks in the conduction band. Figure 4 As shown, among these three different n-type distributed Bragg reflectors, the first n-type distributed Bragg reflector 21 in this embodiment of the invention has the lowest conduction band depletion region barrier peak, and the resulting series resistance is the lowest.

[0066] The present invention example calculates based on the Poisson equation. Figure 3 The energy level distributions of the conduction and valence bands at the interface of three different distributed Bragg reflector structures in an n-type distributed Bragg reflector are shown below. Figure 5 The diagram shows the valence band energy level distribution. Figure 5 The diagram illustrates the valence band energy level distribution of an existing p-type distributed Bragg reflector and the second distributed Bragg reflector in this embodiment of the invention. Figure 5 S7 in the text refers to an n-type distributed Bragg reflector in the prior art (i.e., such as...). Figure 2 and Figure 3 The valence band energy level distribution curve of the distributed Bragg reflector shown in S1 is shown in Figure 8. S8 represents another prior art n-type distributed Bragg reflector (i.e., as shown in Figure 9). Figure 3 The valence band energy level distribution curve of the distributed Bragg reflector (S2 shown in the figure) is shown in Figure 2. S9 represents the p-type second distributed Bragg reflector 22 (i.e., as shown in the figure 2) in the embodiment of the present invention. Figure 3 The valence band energy level distribution curve of the distributed Bragg reflector 20 shown in S3.

[0067] For holes, the energy decreases as the valence band moves upwards. Therefore, upward potential barrier peaks represent low-energy areas where holes easily accumulate, offering less resistance to their migration. Conversely, downward potential barrier peaks represent depletion zones, significantly hindering hole migration. The p-type second distributed Bragg reflector 22 in this embodiment effectively reduces downward hole potential barrier peaks within the valence band. Figure 5As shown, among these three different p-type distributed Bragg reflectors, the second p-type distributed Bragg reflector 22 in this embodiment of the invention has the lowest valence band depletion region barrier peak, and the resulting series resistance is the lowest.

[0068] Figure 6 This is a schematic diagram of another vertical-cavity surface-emitting laser provided in an embodiment of the present invention, with reference to... Figure 6 In this embodiment of the invention, the active region 10 includes a quantum well 11, an oxide layer 12, and a tunnel junction 13 stacked together. The vertical-cavity surface-emitting laser 100 also includes a substrate 30. The oxide layer 12 is located on the side of the quantum well 11 away from the substrate 30. The tunnel junction 13 is located on the side of the oxide layer 12 away from the substrate 30.

[0069] For example, a quantum well 11 fabricated using at least one semiconductor material selected from InGaAs, GaAs, AlGaA, and GaAs can significantly improve radiative recombination efficiency and reduce laser threshold current by confining charge carriers (electrons and holes) within a nanoscale potential well. This can be achieved by selectively oxidizing a high-aluminum AlGaAs layer (such as Al...). 0.9 8Ga 0.02 As), an insulating oxide layer 12 (Al2O3) can be formed, confining the current and optical field within a small aperture (2 μm to 10 μm in diameter), which can reduce the threshold current and improve beam quality. Highly doped (>10) 19 cm -3 p) ++ / n ++ The structure is composed of a semiconductor layer (such as GaAs or AlGaAs), which achieves hole-electron conversion through tunneling effect, replacing the traditional p-type contact layer, and can further reduce the series resistance of the vertical cavity surface-emitting laser 100.

[0070] This invention also provides a method for fabricating a vertical-cavity surface-emitting laser (VCSEL), used to manufacture the VCSEL 100 shown in any of the above embodiments of this invention. Figure 7 A flowchart illustrating a method for fabricating a vertical-cavity surface-emitting laser (VCSEL) according to an embodiment of the present invention is provided, with reference to... Figure 7 The fabrication method of the vertical-cavity surface-emitting laser in this embodiment of the invention includes:

[0071] S110, Prepare the active region.

[0072] S120. A distributed Bragg reflector is fabricated on at least one side of the active region. The distributed Bragg reflector includes multiple first refractive index layers, multiple second refractive index layers, and multiple aluminum composition gradient layers. The first refractive index layers and the second refractive index layers are stacked alternately, and the refractive index of the first refractive index layer is greater than that of the second refractive index layer. The aluminum composition gradient layers are located between the first refractive index layers and the second refractive index layers, and the aluminum composition of the aluminum composition gradient layers increases nonlinearly along a first direction, where the first direction is the direction from the first refractive index layer to the second refractive index layer.

[0073] For example, refer to Figure 1 and Figure 6 The first distributed Bragg mirror 21 of type n, the active region 10 and the second distributed Bragg mirror 22 of type p can be grown sequentially on the substrate 30 using a metal-organic chemical vapor deposition (MOCVD) process.

[0074] Optionally, after fabricating the first distributed Bragg reflector 21, the active region 10, and the second distributed Bragg reflector 22, the fabrication method in this embodiment of the invention further includes: performing mesa etching to form a mesa between the second distributed Bragg reflector 22 and the active region 10; fabricating an oxide confinement layer; fabricating a P-type metal electrode on the side of the second distributed Bragg reflector 22 away from the substrate 30; sequentially fabricating a passivation layer and an antireflection film on the side of the P-type metal electrode away from the substrate 30; thinning and polishing the substrate; and fabricating an n-type metal electrode on the side of the substrate 30 away from the first distributed Bragg reflector 21.

[0075] Based on the same inventive concept, embodiments of the present invention also provide an optical device. Figure 8 This is a schematic diagram of the structure of an optical device provided in an embodiment of the present invention, with reference to... Figure 8 The optical device 200 in this embodiment of the invention includes the vertical-cavity surface-emitting laser 100 provided in any of the above embodiments of the invention. Therefore, the optical device 200 includes the technical features of the vertical-cavity surface-emitting laser 100 and has the beneficial effects of the vertical-cavity surface-emitting laser 100. The similarities can be referred to the description above.

[0076] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, Includes an active region and a distributed Bragg reflector located on at least one side of the active region; The distributed Bragg reflector includes multiple first refractive index layers, multiple second refractive index layers, and multiple aluminum composition gradient layers; the first refractive index layers and the second refractive index layers are alternately stacked, and the refractive index of the first refractive index layer is greater than that of the second refractive index layer; the aluminum composition gradient layer is located between the first refractive index layers and the second refractive index layers, and the aluminum composition of the aluminum composition gradient layer increases nonlinearly along a first direction; the first direction is the direction from the first refractive index layer to the second refractive index layer.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, Along the first direction, the rate of increase of the aluminum composition in the aluminum composition gradient layer decreases.

3. The vertical-cavity surface-emitting laser according to claim 2, characterized in that, The aluminum component gradient layer includes Al (x) Ga (1-x) As; The aluminum composition x at any position in the aluminum composition gradient layer satisfies the following correspondence: x=-0.002×z 2 +0.04×z+0.7; Where z represents the distance between any position in the aluminum composition gradient layer and the reference position in the first direction, and the reference position is the center of the aluminum composition gradient layer; and z is positive when any position is located on the side of the reference position close to the second refractive index layer in contact with the aluminum composition gradient layer, and z is negative when any position is located on the side of the reference position close to the first refractive index layer in contact with the aluminum composition gradient layer.

4. The vertical-cavity surface-emitting laser according to claim 3, characterized in that, The first refractive index layer includes Al (a) Ga (1-a) As; the second refractive index layer includes Al (b) Ga (1-b) As; The aluminum composition x at any position in the aluminum composition gradient layer satisfies: a≤x≤b; Where a represents the aluminum composition of the first refractive index layer, b represents the aluminum composition of the second refractive index layer, a < b, a ≥ 0, b ≤ 1.

5. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The thickness w1 of the aluminum component gradient layer satisfies: 10nm≤w1≤30nm.

6. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The vertical cavity surface-emitting laser further includes a substrate; the distributed Bragg reflector includes a first distributed Bragg reflector and a second distributed Bragg reflector; the first distributed Bragg reflector is located on the side of the active region closer to the substrate; the second distributed Bragg reflector is located on the side of the active region away from the substrate; The first refractive index layer includes a first refractive index layer A and a first refractive index layer B, the second refractive index layer includes a second refractive index layer A and a second refractive index layer B, and the aluminum composition gradient layer includes a first aluminum composition gradient layer and a second aluminum composition gradient layer. The first distributed Bragg reflector includes multiple first α-refractive index layers, multiple second α-refractive index layers, and multiple first aluminum composition graded layers; the second distributed Bragg reflector includes multiple first β-refractive index layers, multiple second β-refractive index layers, and multiple second aluminum composition graded layers.

7. The vertical-cavity surface-emitting laser according to claim 6, characterized in that, The first distributed Bragg reflector includes an n-type distributed Bragg reflector; The second distributed Bragg reflector includes a p-type distributed Bragg reflector.

8. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The active region includes a stacked quantum well, an oxide layer, and a tunnel junction; the vertical cavity surface-emitting laser also includes a substrate. The oxide layer is located on the side of the quantum well away from the substrate; The tunnel junction is located on the side of the oxide layer away from the substrate.

9. A method for fabricating a vertical-cavity surface-emitting laser, used to manufacture the vertical-cavity surface-emitting laser as described in any one of claims 1-8, characterized in that, The preparation method includes: Preparation of active regions; A distributed Bragg reflector is fabricated on at least one side of the active region. The distributed Bragg reflector includes a plurality of first refractive index layers, a plurality of second refractive index layers, and a plurality of aluminum composition gradient layers. The first refractive index layers and the second refractive index layers are alternately stacked, and the refractive index of the first refractive index layer is greater than that of the second refractive index layer. The aluminum composition gradient layers are located between the first refractive index layers and the second refractive index layers, and the aluminum composition of the aluminum composition gradient layers increases nonlinearly along a first direction. The first direction is the direction from the first refractive index layer to the second refractive index layer.

10. An optical device, characterized in that, Includes the vertical cavity surface-emitting laser according to any one of claims 1-8.

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