阅读说明：本技术 一种分布式布拉格反射镜及其制作方法和设计方法 (Distributed Bragg reflector and manufacturing method and design method thereof ) 是由 曾磊 王肇中 于 2020-07-06 设计创作，主要内容包括：本申请涉及一种分布式布拉格反射镜及其制作方法和设计方法,所述分布式布拉格反射镜的制作方法包括步骤：通过非选择性干法刻蚀和选择性湿法腐蚀相结合的方式,在反射镜层内形成N组高折射率对比度的两层薄膜,其中,折射率对比度大于2。相对于现有的低折射率对比度分布式布拉格反射镜采用十组甚至更多组薄膜组合实现高反射率的技术,本申请提供的分布式布拉格反射镜的制作方法,采用少量组数的薄膜即可实现高反射率,使得制造成本较低、外延工艺控制难度小。(The application relates to a distributed Bragg reflector and a manufacturing method and a design method thereof, wherein the manufacturing method of the distributed Bragg reflector comprises the following steps: and N groups of two films with high refractive index contrast are formed in the reflector layer in a mode of combining non-selective dry etching and selective wet etching, wherein the refractive index contrast is more than 2. Compared with the technology that ten groups of films or even more groups of films are combined to realize high reflectivity of the existing low-refractive-index-contrast distributed Bragg reflector, the manufacturing method of the distributed Bragg reflector provided by the application can realize high reflectivity by adopting a small number of groups of films, so that the manufacturing cost is low, and the control difficulty of an epitaxial process is small.)

1. A method for manufacturing a distributed Bragg reflector is characterized by comprising the following steps: and N groups of two films with high refractive index contrast are formed in the reflector layer in a mode of combining non-selective dry etching and selective wet etching, wherein the refractive index contrast is more than 2.

2. A method of fabricating a distributed bragg reflector according to claim 1, further comprising the steps of:

alternately growing N sacrificial layers (2) and N reflecting layers (3) on a substrate (1) to form an epitaxial structure;

etching the epitaxial structure by adopting a non-selective dry etching process until the etching depth covers all the sacrificial layers (2) to form a corrosion window (4);

etching the sacrificial layer (2) in and around the etching window (4) by adopting a selective wet etching process to form a filling space (5);

n groups of two thin films with high refractive index contrast are formed between the filling space (5) and the reflecting layer (3).

3. A method of fabricating a distributed bragg reflector according to claim 2, wherein said step of forming N sets of two thin films having high refractive index contrast between said filled space (5) and said reflective layer (3) further comprises the steps of: filling one of air, liquid or gel in the filling space (5).

4. A method of fabricating a distributed bragg reflector according to claim 2, wherein the step of forming the etch window (4) by etching the epitaxial structure using a non-selective dry etching process until the etching depth covers all of the sacrificial layers (2) comprises:

and etching the epitaxial structure to the lowest sacrificial layer (2) from top to bottom by adopting photoetching and non-selective dry etching processes to form an etching window (4).

5. A method of fabricating a distributed bragg reflector according to claim 2, wherein the step of forming the etch window (4) by etching the epitaxial structure using a non-selective dry etching process until the etching depth covers all of the sacrificial layers (2) comprises:

removing the substrate (1) by adopting grinding and selective wet etching processes;

and etching the epitaxial structure to the uppermost sacrificial layer (2) from bottom to top by adopting photoetching and non-selective dry etching processes to form a corrosion window (4).

6. A method of fabricating a distributed bragg reflector according to claim 2 wherein the erosion window (4) includes a plurality of fan-shaped regions, and two adjacent fan-shaped regions are spaced apart by a predetermined distance.

7. A method of fabricating a distributed bragg reflector according to claim 2, wherein said forming N sets of two thin films with high refractive index contrast between said filled space and said reflective layer (3) is performed by:

the InP thin films are formed on the reflecting layers (3), the reverse lining films are formed in the filling spaces (5) between every two adjacent reflecting layers (3), and N groups of alternately laminated two thin films are formed by the N reflecting layers and all the filling spaces (5).

8. A distributed Bragg reflector manufactured by the method for manufacturing a distributed Bragg reflector according to any one of claims 1 to 7.

9. A distributed bragg reflector, comprising: the reflective mirror comprises a reflective mirror layer, wherein N groups of two thin films with high refractive index contrast are formed in the reflective mirror layer, and the refractive index contrast is greater than 2.

10. A distributed Bragg reflector according to claim 9, wherein the reflector layer comprises N sacrificial layers (2) and N reflecting layers (3) which are alternately stacked, a filling space (5) is formed between two adjacent reflecting layers (3), the filling space (5) is filled with a medium, and the reflecting layers (3) and the medium form N groups of two thin films with high refractive index contrast.

11. A distributed bragg reflector according to claim 10, wherein: the filling space (5) is formed by combining non-selective dry etching and selective wet etching of the epitaxial structure of the distributed Bragg reflector.

12. A distributed Bragg reflector according to claim 9, wherein the two films are an InP film and a counter film, respectively.

13. A distributed bragg reflector according to claim 12, wherein: the reverse lining film is one of air, liquid or gel.

14. A distributed bragg reflector according to claim 10, wherein: the reflective mirror is characterized by further comprising a substrate (1) and a functional layer (6), wherein the reflective mirror layer is arranged between the substrate (1) and the functional layer (6), and an inlet of the filling space (5) is arranged on one side close to the functional layer (6).

15. A distributed bragg reflector according to claim 10, wherein: the reflector structure is characterized by further comprising a functional layer (6), wherein the functional layer (6) is arranged on the reflector layer, and the inlet of the filling space (5) is arranged on one side far away from the functional layer (6).

16. A method of designing a distributed bragg reflector according to any one of claims 10 to 15, comprising the steps of:

determining the central wavelength lambda of the distributed Bragg reflector according to the application scene and the design requirements of the device_cAnd the refractive indices of the two films at the center wavelength;

according to the central wavelength lambda_cAnd the refractive index of the two films at the central wavelength determines the thickness of the two films;

and calculating the relation between the group number of the two layers of films and the reflectivity by a transfer function method, and obtaining the group number of the corresponding two layers of films according to the requirement of the reflectivity.

Technical Field

The present disclosure relates to the field of semiconductor technologies, and in particular, to a distributed bragg reflector and a method for manufacturing and designing the same.

Background

A Distributed Bragg Reflector (DBR) is a periodic structure of two materials of different refractive index alternately arranged in an ABAB fashion, each layer of material having an optical thickness of 1/4 times the central reflection wavelength.

In a planar type photoelectric device, a DBR mirror formed by alternately forming two thin films having different refractive indexes is a common structure, and the DBR mirror is formed of two materials having different refractive indexes, and is generally manufactured by epitaxial growth, and a material lattice-matched to a substrate is used, for example, for an indium phosphide (InP) substrate, InGaAsP, inalgaa, or the like is used as a material.

However, the difference of the refractive index coefficients of the InP material system is small, i.e. the refractive index contrast is low, so that it is usually necessary to use more than tens of sets of periodic quarter-wavelength thin films when manufacturing the DBR mirror, and the high-reflectivity thin film and the low-reflectivity thin film are alternated to obtain the high-reflectivity DBR mirror, which results in high manufacturing cost and difficult control of the epitaxial process.

In is formed by_0.624Ga_0.376As_0.8P_0.2DBR of/InP composition, for example, requires 30 In groups to achieve 90% reflectivity due to low refractive index contrast, about 0.3_0.624Ga_0.376As_0.8P_0.2The total thickness of the/InP thin film is about 7 mu m, the manufacturing cost is high, the difficulty is high, and the method is one of the main bottlenecks of the InP-based VCSEL laser with the 1550nm waveband.

Disclosure of Invention

The embodiment of the application provides a manufacturing method of a distributed Bragg reflector, which aims to solve the technical problem that high reflectivity can be achieved only by adopting more than dozens of groups of periodic quarter-wavelength films in the related technology.

In a first aspect, the present application provides a method for manufacturing a distributed bragg reflector, which includes the steps of: and N groups of two films with high refractive index contrast are formed in the reflector layer in a mode of combining non-selective dry etching and selective wet etching, wherein the refractive index contrast is more than 2.

In some embodiments, the method for manufacturing a distributed bragg reflector specifically includes the steps of:

alternately growing N sacrificial layers and N reflecting layers on a substrate to form an epitaxial structure;

etching the epitaxial structure by adopting a non-selective dry etching process until the etching depth covers all the sacrificial layers to form an etching window;

etching the sacrificial layer in and around the etching window by adopting a selective wet etching process to form a filling space;

and forming N groups of two films with high refractive index contrast between the filling space and the reflecting layer.

In some embodiments, before forming the N sets of high-refractive-index-contrast two films between the filled space and the reflective layer, the method further comprises: filling one of air, liquid or gel in the filling space.

In some embodiments, the etching the epitaxial structure by using a non-selective dry etching process until the etching depth covers all the sacrificial layers, and the specific step of forming the etching window includes:

and etching the epitaxial structure to the lowest sacrificial layer from top to bottom by adopting photoetching and non-selective dry etching processes to form an etching window.

In some embodiments, the etching the epitaxial structure by using a non-selective dry etching process until the etching depth covers all the sacrificial layers, and the specific step of forming the etching window includes:

removing the substrate by adopting a grinding and selective wet etching process;

and etching the epitaxial structure to the uppermost sacrificial layer from bottom to top by adopting photoetching and non-selective dry etching processes to form a corrosion window.

In some embodiments, the erosion window includes a plurality of sectors, and two adjacent sectors are spaced apart by a distance.

In some embodiments, the specific process of forming N sets of two films with high refractive index contrast between the filled space and the reflective layer is:

the reflecting layers form InP thin films, a reverse lining film is formed in a filling space between every two adjacent reflecting layers, and N groups of alternately laminated two thin films are formed by the N reflecting layers and all the filling spaces.

In a second aspect, the present application provides a distributed bragg reflector fabricated by the above method for fabricating a distributed bragg reflector.

In a third aspect, the present application provides a distributed bragg reflector comprising a reflector layer having N sets of two thin films of high refractive index contrast formed therein, wherein the high refractive index contrast is greater than 2.

In some embodiments, the mirror layer includes N sacrificial layers and N reflective layers alternately stacked, a filling space is formed between two adjacent reflective layers, the filling space is filled with a medium, and the reflective layers and the medium form N groups of two thin films with high refractive index contrast.

In some embodiments, the filling space is formed by combining non-selective dry etching and selective wet etching for the epitaxial structure of the distributed bragg reflector.

In some embodiments, the two films are an InP film and a counter film, respectively.

In some embodiments, the backing film is one of air, liquid, or gel.

In some embodiments, the dbr further comprises a substrate and a functional layer, the mirror layer is disposed between the substrate and the functional layer, and the entrance of the fill space is on a side adjacent to the functional layer.

In some embodiments, the dbr further comprises a functional layer disposed on the mirror layer, and the inlet of the filling space is on a side away from the functional layer.

In a fourth aspect, the present application further provides a method for designing the distributed bragg reflector, including the steps of:

determining the central wavelength lambda of the distributed Bragg reflector according to the application scene and the design requirements of the device_cAnd the refractive indices of the two films at the center wavelength;

according to the central wavelength lambda_cAnd the refractive index of the two films at the central wavelength determines the thickness of the two films;

and calculating the relation between the group number of the two layers of films and the reflectivity by a transfer function method, and obtaining the group number of the corresponding two layers of films according to the requirement of the reflectivity.

The beneficial effect that technical scheme that this application provided brought includes: the high reflectivity can be realized by adopting a small number of groups of films, so that the manufacturing cost is lower, and the control difficulty of the epitaxial process is small.

The embodiment of the application provides a manufacturing method of a distributed Bragg reflector, N groups of thin film combinations with high refractive index contrast are formed in a reflector layer in a mode of combining non-selective dry etching and selective wet etching, and the numerical value of N is small, namely, the high reflectivity can be realized by adopting a small number of groups of thin films, so that the manufacturing cost is low, and the control difficulty of an epitaxial process is small.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a flowchart of a method for manufacturing a distributed bragg reflector according to an embodiment of the present disclosure;

fig. 2 is a flowchart of a method for manufacturing a first distributed bragg reflector according to an embodiment of the present disclosure;

fig. 3 is a schematic view of an epitaxial structure in a first method for fabricating a distributed bragg reflector according to an embodiment of the present disclosure;

fig. 4 is a schematic diagram of a functional layer after etching in a method for manufacturing a first distributed bragg reflector according to an embodiment of the present disclosure;

fig. 5 is a schematic view of a protective film in a first method for manufacturing a distributed bragg reflector according to an embodiment of the present disclosure;

FIG. 6 is a side view of an etching window in a first method for fabricating a distributed Bragg reflector according to an embodiment of the present disclosure;

FIG. 7 is a top view of an etching window in a first method for fabricating a distributed Bragg reflector according to an embodiment of the present disclosure;

fig. 8 is a schematic view of a filling space in a first method for manufacturing a distributed bragg reflector according to an embodiment of the present disclosure;

fig. 9 is a schematic diagram of a filling medium in a manufacturing method of a first distributed bragg reflector according to an embodiment of the present disclosure;

fig. 10 is a flowchart of a method for manufacturing a second distributed bragg reflector according to an embodiment of the present disclosure;

fig. 11 is a schematic view of an epitaxial structure after a substrate is removed in a second method for manufacturing a distributed bragg reflector according to an embodiment of the present disclosure;

fig. 12 is a schematic view of an etching window in a method for manufacturing a second distributed bragg reflector according to an embodiment of the present disclosure;

fig. 13 is a schematic view illustrating a filling space in a manufacturing method of a second distributed bragg reflector according to an embodiment of the present disclosure;

fig. 14 is a schematic diagram of a filling medium in a manufacturing method of a second distributed bragg reflector according to an embodiment of the present disclosure;

fig. 15 is a flowchart of a method for designing a distributed bragg reflector according to an embodiment of the present disclosure;

FIG. 16 is a schematic diagram of the reflection spectrum of an InP/air combination provided in the examples of the present application.

In the figure: 1. a substrate; 2. a sacrificial layer; 3. a reflective layer; 4. corroding the window; 5. filling the space; 6. a functional layer; 61. and (5) protecting the film.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a manufacturing method of a distributed Bragg reflector, which comprises the following steps: and N groups of two films with high refractive index contrast are formed in the reflector layer in a mode of combining non-selective dry etching and selective wet etching, wherein the refractive index contrast is more than 2. In the embodiment of the application, the refractive index contrast is greater than 2, and N is less than or equal to 3, so that the reflectivity of the distributed Bragg reflector is not lower than 90%.

Specifically, in the embodiment of the present application, the two thin films with high refractive index contrast are formed by a semiconductor material with a refractive index greater than 1 and air with a refractive index of 1, the refractive index contrast of the two thin films is close to the upper limit of the distributed mirror film group, taking InP/air as an example, the refractive index is 3.2/1, and the refractive index contrast Δ n is 2.2; in the conventional semiconductor distributed mirror, the refractive index contrast of the film group is low, and for example, in the InP/InGaAs combination, the refractive index is 3.2/3.6, and the refractive index contrast Δ n is 0.4, so that it is necessary to combine several tens of thin films to achieve a high reflectance of 90% or more.

Therefore, in the embodiment of the application, N groups of thin film combinations with high refractive index contrast are formed in the reflector layer in a mode of combining non-selective dry etching and selective wet etching, and the numerical value of N is small, that is, a small number of groups of thin films are adopted to realize high reflectivity, so that the manufacturing cost is low, and the control difficulty of the epitaxial process is small.

Referring to fig. 1, the method for manufacturing a distributed bragg reflector specifically includes the steps of:

s1: alternately growing N sacrificial layers 2 and N reflecting layers 3 on a substrate 1 to form an epitaxial structure;

s2: etching the epitaxial structure by adopting a non-selective dry etching process until the etching depth covers all the sacrificial layers 2 to form an etching window 4;

s3: etching the sacrificial layer 2 in and around the etching window 4 by adopting a selective wet etching process to form a filling space 5;

s4: two films of N sets of high refractive index contrast are formed between the filled space 5 and the reflective layer 3.

In the embodiment of the present application, only two films with N groups of high refractive index contrasts need to be formed in the mirror layer, and the etching windows 4 and the filling spaces 5 may be formed in various manners in the steps S1 to S4, and may be selected according to actual conditions.

Further, before forming N sets of two films with high refractive index contrast between the filling space 5 and the reflective layer 3 in step S6, the method further includes the steps of: the filling space 5 is filled with one of air, liquid or gel. Filling the voids with a liquid or gel can improve the thermal conductivity and mechanical strength, and can improve the robustness of the DBR compared to air.

Further, in the embodiment of the present application, the etching the epitaxial structure by using the non-selective dry etching process until the etching depth covers all the sacrificial layers 2, and the specific step of forming the etching window 4 includes:

and etching the epitaxial structure to the lowermost sacrificial layer 2 from top to bottom by adopting photoetching and non-selective dry etching processes to form an etching window 4.

Correspondingly, referring to fig. 2, an embodiment of the present application provides a method for manufacturing a first distributed bragg reflector, which is a front surface process and specifically includes the steps of:

s101: alternately growing N sacrificial layers 2 and N reflective layers 3 on a substrate 1, and growing a functional layer 6 on the uppermost reflective layer 3 to form an epitaxial structure, as shown in fig. 3, where N is 3;

s102: etching the functional layer 6 of the epitaxial structure by using a non-selective dry etching process, as shown in fig. 4;

s103: plating a protective film 61 on the etched functional layer 6, as shown in fig. 5; specifically, a layer of SiO2 is deposited on the side wall and the top of the functional layer 6 by adopting a PECVD technology to form a protective film 61;

s104: vertically etching the epitaxial structure by using a non-selective dry etching process until the etching depth covers all the sacrificial layers 2 to form a corrosion window 4, as shown in fig. 6 and 7; the adopted non-selective dry etching process can be ICP;

s105: etching the sacrificial layer 2 in and around the etching window 4 by using a selective wet etching process to form a filling space 5, as shown in fig. 8; and N groups of two thin films with high refractive index contrast are formed between the filling space 5 and the reflecting layer 3;

and S106, filling a medium in the filling space 5, wherein the medium is one of air, liquid or gel, as shown in figure 9.

Specifically, in step S105, the selective wet etching process may be H₃PO₃：H₂O₂Solutions or H₂SO₄：H₂O₂The solution selectively etches InGaAs, but not InP.

Referring to fig. 7, in the embodiment of the present invention, the erosion window 4 includes a plurality of sectors, and two adjacent sectors are spaced apart from each other. The area corresponding to the corrosion window 4 is a to-be-corroded area, a non-corroded area is arranged between two adjacent fan-shaped areas, and the non-corroded area is a suspended supporting area.

The number of the sector areas may be three as shown in fig. 7, or may be multiple, and the mechanical strength may be improved, and the number is not limited herein.

Further, in the embodiment of the present application, the specific steps of etching the epitaxial structure by using the non-selective dry etching process until all the sacrificial layers 2 are etched to form the etching window 4 include:

removing the substrate 1 by adopting grinding and selective wet etching processes;

and etching the epitaxial structure to the uppermost sacrificial layer 2 from bottom to top by adopting photoetching and non-selective dry etching processes to form a corrosion window 4.

Correspondingly, referring to fig. 10, an embodiment of the present application provides a method for manufacturing a second distributed bragg reflector, which is a backside process and specifically includes the steps of:

s201: alternately growing N low-refractive-index sacrificial layers 2 and N high-refractive-index reflective layers 3 on a substrate 1, and growing a functional layer 6 on the uppermost reflective layer 3 to form an epitaxial structure, as shown in fig. 3, where N is 3;

s202: removing the substrate 1 by using a grinding and selective wet etching process, as shown in fig. 11; specifically, the thickness of the substrate 1 is reduced to be less than 100 μm by a grinding process, and then a selective wet etching process, such as hydrochloric acid, is adopted to rapidly etch InP without etching InGaAs, so as to remove the substrate 1;

s203: vertically etching the epitaxial structure to the uppermost sacrificial layer 2 from bottom to top by adopting photoetching and non-selective dry etching processes to form a corrosion window 4 as shown in FIG. 12;

s204: etching the sacrificial layer 2 in and around the etching window 4 by using a selective wet etching process to form a filling space 5, as shown in fig. 13; and N groups of two-layer film combination with high refractive index contrast are formed between the filling space 5 and the reflecting layer 3;

and S205, filling a medium in the filling space 5, wherein the medium is one of air, liquid or gel, as shown in FIG. 14.

Further, in the embodiment of the present application, a specific process of forming N sets of two thin films with high refractive index contrast between the filling space and the reflective layer 3 is as follows:

the reflective layers 3 form an InP film, the filling spaces 5 between two adjacent reflective layers 3 form a reverse lining film, and N groups of alternately laminated two films are formed by N reflective layers and all the filling spaces 5.

The embodiment of the application also provides a distributed Bragg reflector which is manufactured by using the manufacturing method of the distributed Bragg reflector.

The embodiment of the application also provides a distributed Bragg reflector, which comprises a reflector layer, wherein N groups of two layers of films with high refractive index contrast are formed in the reflector layer, N is less than or equal to 3, and the reflectivity of the distributed Bragg reflector is not less than 90%.

Furthermore, in the embodiment of the present application, the mirror layer includes N sacrificial layers 2 and N reflective layers 3 that are alternately stacked, a filling space 5 is formed between two adjacent reflective layers 3, the filling space 5 is filled with a medium, and the reflective layers 3 and the medium form N groups of two thin films with high refractive index contrast.

Furthermore, in the embodiment of the present application, the filling space 5 is formed by combining a non-selective dry etching and a selective wet etching for the epitaxial structure of the dbr.

In some embodiments, the two films are an InP film and a counter film, respectively. The reverse lining film is one of air, liquid or gel.

Referring to fig. 9, in the embodiment of the present application, the dbr further includes a substrate 1 and a functional layer 6, the mirror layer is disposed between the substrate 1 and the functional layer 6, and the entrance of the filling space 5 is on the side close to the functional layer 6.

Referring to fig. 14, in an embodiment of the present application, the dbr is further characterized in that: the reflective mirror further comprises a functional layer 6, wherein the functional layer 6 is arranged on the reflective mirror layer, and the inlet of the filling space 5 is arranged on one side far away from the functional layer 6.

The distributed Bragg reflector provided by the embodiment of the application forms N groups of two layers of films with high refractive index contrast in the reflector layer, and the numerical value of N is small, namely the high reflectivity can be realized by adopting a small number of groups of films, so that the manufacturing cost is low, and the control difficulty of the epitaxial process is small.

Referring to fig. 15, an embodiment of the present application further provides a method for designing a distributed bragg reflector, which includes the steps of:

a1: determining the central wavelength lambada c of the distributed Bragg reflector and the refractive indexes of the two layers of thin films at the central wavelength according to application scenes and device design requirements, and respectively recording the refractive indexes of the two layers of thin films at the central wavelength as n_InPAnd n_Ref(ii) a In the embodiment of the present application, the reflective layer 3 is InP, and the sacrificial layer 2 is InGaAs;

a2: determining the thickness of two layers of film according to the central wavelength lambdacThe thickness of the film was 0.25 lambda each_c/n_InP、0.25λ_c/n_Ref(ii) a The two films are InP film and reverse liner film, respectively, and the thickness of InP film is 0.25 lambda_c/n_InPThe thickness of the reverse lining film is 0.25 lambda_c/n_Ref(ii) a The thickness of the sacrificial layer 2 is the same as that of the contrast film, and the thickness of the sacrificial layer 2 can be obtained;

a3: and calculating by a transfer function method to obtain the relationship between the group number and the reflectivity of the two layers of films, and obtaining the group number of the corresponding two layers of films according to the requirement of the reflectivity, namely obtaining the parameter value of N.

In the present example, taking InP and air as the two films, respectively, as an example, the center wavelength is set to 1.55 μm, and the relationship between the number of sets of two films and the reflectance calculated in step a3 is shown in fig. 16.

Referring to the results of the reflection spectrum calculation for the group 1, group 3, or group 5 InP/air combinations shown in fig. 16, a high reflectance of 90% or more can be achieved using only 3 InP/air combinations.

According to the design method of the distributed Bragg reflector, all parameters of the distributed Bragg reflector can be determined according to practical application scenes and device design requirements, wherein the related parameters comprise the thicknesses of two layers of films and the number of groups of the two layers of films, the design method is simple, and high reflectivity can be achieved by adopting a small number of groups of films.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.