CN209912889U

CN209912889U - Composite DBR structure

Info

Publication number: CN209912889U
Application number: CN201920847995.3U
Authority: CN
Inventors: 张丽旸; 程凯
Original assignee: SUZHOU JINGZHAN SEMICONDUCTOR CO Ltd
Current assignee: SUZHOU JINGZHAN SEMICONDUCTOR CO Ltd
Priority date: 2019-06-06
Filing date: 2019-06-06
Publication date: 2020-01-07
Anticipated expiration: 2029-06-06

Abstract

The utility model discloses a compound DBR structure belongs to the microelectronics technology field. At least one periodic structure of the composite DBR structure, wherein the periodic structure comprises: a porous layer and a coating layer disposed on the porous layer. The utility model discloses a compound DBR structure cycle number is littleer, and geometric thickness is thinner, and the stress control effect is better, and crystal quality is higher. The DBR structure has more excellent reflection performance compared with the traditional DBR structure, and can be widely applied to LED devices.

Description

Composite DBR structure

Technical Field

The application relates to the technical field of microelectronics, in particular to a composite DBR structure.

Background

Distributed Bragg Reflectors (DBRs), which are periodic structures composed of materials with different refractive indexes grown on epitaxial layers of a semiconductor substrate, each having an optical thickness of 1/4 of a central reflection wavelength, have been widely used in semiconductor devices because of their high reflection property to reduce light absorption of the substrate and to improve the light efficiency of the semiconductor device. From the twenty-year process of DBR development, the following development features appear: (1) in the aspect of material selection of the DBR structure, a material with a thinner thickness is preferred; (2) increasing the reflectivity of DBRs is a major research direction in improving the light extraction efficiency of semiconductor devices. However, how to further improve the reflectivity of the DBR on this basis, continuously reduce the geometric thickness of the DBR, and manufacture a DBR structure with better performance and thinner thickness is still a difficult problem to be solved urgently in the DBR technical development process.

SUMMERY OF THE UTILITY MODEL

The application provides a composite DBR structure.

According to an embodiment of the application, the composite DBR structure comprises: at least one periodic structure, wherein the periodic structure comprises: a porous layer and a multilayer structure disposed over the porous layer.

In another embodiment of the present application, the porous layer is made of a GaN-based material.

In another embodiment of the present application, the porous layer is made of GaN.

In another embodiment of the present application, the multilayer structure comprises: periodically arranged GaN layer and Al formed on GaN layer_XIn_YGa_1-X-YAnd N layers, wherein x is more than or equal to 0 and less than l, y is more than or equal to 0 and less than l, and x + y is less than l.

In another embodiment of the present application, the multilayer structure is a superlattice structure.

In another embodiment of the present application, the porous layer has a thickness of 80-90 nm.

In another embodiment of the present application, the porosity of the porous layer in at least one periodic structure increases sequentially toward the direction of light emission.

The beneficial effects of the utility model reside in that: the utility model discloses a compound DBR structure has the porous layer to and the periodic multilayer structure that forms on the porous layer, the porous layer reduces the refracting index of self through the air bed that forms in the space, thereby realize high reflectivity and high light-emitting rate with its refractive index difference with multilayer structure, and as long as the porosity (the ratio of the air volume in the porous layer and the total volume of porous layer) increases, then can show the cycle number that reduces the DBR structure, reduce its geometric thickness. Because the utility model discloses a compound DBR structure has excellent reflectivity, need not to peel off the Si substrate that supplies the DBR structure to grow during consequently practical application, has simplified process flow, has improved the yield. Moreover, multilayer structure can further reduce overall structure's thickness among the compound DBR structure to strengthen its practicality, can grow the multilayer structure of different thickness simultaneously according to the demand of different incident lights, with the reflectance spectrum who improves compound DBR structure.

The above description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention clearer and can be implemented according to the content of the description, the following detailed description is made with reference to the preferred embodiments of the present invention and accompanying drawings.

Drawings

Fig. 1 is a schematic diagram of the composite DBR structure of the present invention.

Fig. 2a and 2b show white light reflectance spectra of four DBR structures.

Fig. 3 is a schematic diagram of overlapping of cutoff forbidden band widths of a plurality of periodic structures.

Detailed Description

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

Fig. 1 is a schematic diagram of a composite DBR structure according to an embodiment of the present invention, where the composite DBR structure includes at least one periodic structure 100, and the periodic structure 100 includes a porous layer 11 and a multilayer structure 20 disposed on the porous layer 11.

In the embodiment shown in fig. 1, a periodic structure 100 with two periods is shown, but the number of the periodic structures 100 in the present invention is not limited thereto,

the porous layer 11 may be made of a GaN-based material, i.e., a compound containing at least Ga atoms and N atoms, such as GaN, AlGaN, InGaN, AlInGaN, or the like. Thus, the porous layer 11 may be, for example, porous GaN or the like.

The multilayer structure 20 includes: periodically arranged GaN layer 21And Al formed on the GaN layer 21_XIn_YGa_1-X-YN layers 22 (x is more than or equal to 0 and less than or equal to l, y is more than or equal to 0 and less than or equal to l, and x + y is less than or equal to l). Preferably, the multilayer structure 20 is a superlattice layer. Al (Al)_XIn_YGa_1-X-YThe lattice height of N and GaN is matched, and stress can be released in time in the growth process so as to reduce the generation of cracks on the crystal layer, thereby growing the crystal layer with high quality. GaN layer 21 and Al_XIn_YGa_1-X-YThe number of cycles of the N layers 22 may be determined according to specific design requirements.

The geometrical thickness D of the porous layer 11 or the multilayer structure 20 can be calculated by the following formula: d ═ λ/4/N, (where λ is the central reflection wavelength, λ/4 is the optical thickness of the porous layer or multilayer structure, and N is the refractive index of the porous layer or multilayer structure). The porous layer 11 has a thickness of 30-200nm, preferably 70-175nm, and more preferably 80-90 nm.

As can be seen from the optical thin film theory, the spectral reflectance and the full width at half maximum of the DBR increase with the increase of the refractive index difference of the material, so to obtain a good DBR reflection spectrum, the refractive index difference of the material should be as large as possible. The utility model discloses in, porous layer 11 is the low refracting index rete, and multilayer structure 20 is the high refracting index rete.

The porous structure in porous layer 11 introduces air, and thus porous layer 11 has a lower refractive index than a normal semiconductor layer. Because according to empirical formulas: the refractive index of porous GaN is equal to the refractive index x porosity of air + the refractive index x (1-porosity) of GaN, where porosity refers to the ratio of the volume of air in the porous layer to the total volume of the porous layer, the refractive index of GaN is about 2.5, and the refractive index of air is about 1.

As the porosity (the ratio of the volume of air in the porous layer to the total volume of the porous layer) increases, the refractive index of the porous layer decreases, and thus the difference in refractive index from the adjacent multilayer structure can be further increased to achieve high reflectivity, so that the number of periods of the DBR structure is significantly reduced, reducing the overall thickness of the DBR structure.

In the conventional DBR structure, since the Si substrate for the DBR structure growth has a strong light absorption characteristic, the reflectivity of the DBR structure is reduced, and the light extraction rate of the semiconductor device is affected, so that the Si substrate is usually peeled off in the semiconductor device in which the DBR is embedded. And the utility model discloses a compound DBR structure is owing to have excellent reflection performance, need not to peel off the Si substrate that supplies the DBR structure to grow during consequently practical application, has simplified process flow, has improved the yield.

Table 1 shows the white light reflectance spectra of four DBR structures tested at room temperature when the reflection wavelength is 460nm, wherein 1-porous GaN layer + GaN/Al_XIn_YGa_1-X-YThe N-multilayer DBR structure is a composite DBR structure in an embodiment of the present application; the 2-AlN/GaN DBR, the 3-AlInN/GaN DBR and the 4-AlGaN/GaN DBR are other DBR structures in the prior art, and the following table is obtained through comparison:

TABLE 1

From the above table, it can be seen that the porous GaN layer + GaN/Al in one embodiment of the present application_XIn_YGa_1-X-YThe DBR with the N multi-layer structure can achieve the reflection effect with the reflectivity of 1 after 5 periods, and other DBR structures respectively need 16 periods, 20 periods and 32 periods to achieve the same reflection effect; the utility model discloses a cycle number that compound DBR structure needs is minimum, and the geometric thickness that corresponds is thinnest, and the forbidden band width that obtains is the biggest, has shown more excellent reflectance properties for other three kinds of traditional DBR structures.

Fig. 2a shows an embodiment of applying the DBR structure of the present application to an LED device, which includes a substrate 1, a nucleation layer 2, a buffer layer 3, an n-type doped DBR structure 4, an active region 5, a p-type doped DBR structure 6, a positive electrode 7/8, and a negative electrode 9, as shown in fig. 2 a.

Fig. 2b shows an embodiment of applying the DBR structure of the present application to an LED device, which includes a substrate 1, a nucleation layer 2, a buffer layer 3, an n-doped DBR structure 4, an active region 5, a p-doped DBR structure 6, a positive electrode 7, and a negative electrode 9, as shown in fig. 2 b. Fig. 2b differs from fig. 2a in that the light-emitting position is different due to the difference in the device structure design.

In another embodiment of the present invention, the porosity of the porous layer 11 in the plurality of periodic structures 100 in the DBR structure gradually increases toward a certain direction, and different porosities correspond to different cut-off forbidden band widths, and the wider cut-off forbidden band width is realized by stacking the plurality of periodic structures 100 with different porosities, thereby realizing that the DBR structure as a whole has a wider cut-off forbidden band width. As shown in fig. 3, fig. 3 is a schematic diagram of overlapping of the cut-off forbidden bandwidths of the plurality of periodic structures 100.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A composite DBR structure, comprising:

at least one periodic structure, wherein the periodic structure comprises:

a porous layer; and

a multilayer structure disposed over the porous layer, wherein the multilayer structure comprises: periodically arranged GaN layer and Al formed on GaN layer_XIn_YGa_1-X-YAnd N layers, wherein x is more than or equal to 0 and less than or equal to l, y is more than or equal to 0 and less than or equal to l, and x + y is less than or equal to l.

2. The composite DBR structure of claim 1 wherein the porous layer is made of a GaN based material.

3. The composite DBR structure of claim 2, wherein the porous layer is made of GaN.

4. The composite DBR structure of claim 1, wherein the multilayer structure is a superlattice structure.

5. The composite DBR structure of claim 1, wherein the porous layer has a thickness of 30-200 nm.