DBR structure, light emitting diode and light emitting device

Abstract

The invention provides a DBR structure, a light-emitting diode and a light-emitting device, and the DBR structure sequentially comprises a first part which comprises a plurality of first material layers with the optical thickness larger than 0.1 lambda and at least one first material layer with the optical thickness smaller than 0.05 lambda; the optical thickness of the first material layer is between 0.3 lambda and 0.45 lambda; the optical thickness of the first material layer ranges from 0.3 lambda to 0.45 lambda, and the optical thickness difference value of the first material layer of the third part is larger than the optical thickness difference value of the first material layer of the second part. The module design provided by the invention can effectively resist the problem of wide-angle light transmission weakening caused by wavelength change, promote light rays of different wave bands to be emitted from the side surface and the back surface of the light emitting diode, and along with the change of an incident angle, the DBR structure can always keep stable and uniform light transmittance, so that the brightness of a chip is increased, and the light emitting efficiency is improved. And the light emitting uniformity is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a DBR structure, a light emitting diode and a light emitting device. Background Art

[0002] Light Emitting Diode (LED) is a semiconductor device whose basic structure includes a PN junction between a P-type semiconductor and an N-type semiconductor. When a forward voltage is applied to the LED, electrons and holes recombine at the junction of the PN junction to release energy, which is emitted in the form of photons to form light radiation.

[0003] In Mini backlight products, large-angle Mini LEDs are easier to achieve panel uniformity due to their large light-emitting angle. Compared with traditional LED chips, large-angle Mini LEDs are arranged more sparsely at the backlight application end and do not require additional lenses for secondary light distribution, greatly reducing production costs.

[0004] In order to ensure that the chip emits light at a large angle, the existing technology mainly relies on the vapor deposition of distributed Bragg reflectors (DBR) on the light-emitting surface of the LED chip. This structure can guide large-angle light to pass through and reflect small-angle light, effectively promoting the light to be emitted from the side and back to achieve the purpose of increasing the light-emitting angle. However, the existing solution has a significant technical bottleneck: the wavelength band in which the LED chip can maintain good large-angle light emission is limited. As the wavelength changes, the transmission of the LED chip to large-angle light is weakened, resulting in a decrease in the brightness of the chip. Therefore, it is necessary to provide a technical solution to solve or improve the above-mentioned difficult problems. Summary of the invention

[0005] In view of the defects and shortcomings of large-angle LED chips in the prior art as described above, the purpose of the present application is to provide a DBR structure, a light-emitting diode and a light-emitting device to effectively resist the weakening of large-angle light transmittance caused by wavelength changes and increase the brightness of the chip.

[0006] In order to achieve the above-mentioned object and other related objects, the present application provides a distributed Bragg reflection structure, comprising at least a first material layer and a second material layer stacked alternately, wherein the refractive index of the first material layer is less than the refractive index of the second material layer; along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially comprises:

[0007] The first part includes a plurality of first material layers and a plurality of second material layers, wherein the first material layer includes a plurality of first material layers with an optical thickness greater than 0.1λ and at least one first material layer with an optical thickness less than 0.05λ;

[0008] The second part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ;

[0009] The third part includes multiple first material layers and multiple second material layers, wherein the optical thickness of the first material layers is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layers in the third part is greater than the optical thickness difference of the first material layers in the second part.

[0010] According to one aspect of the present application, a distributed Bragg reflection structure is further provided, comprising at least a first material layer and a second material layer stacked alternately, wherein the refractive index of the first material layer is less than the refractive index of the second material layer; along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially comprises:

[0011] The first part includes a plurality of first material layers and a plurality of second material layers, wherein the first material layers include at least one first material layer with an optical thickness less than 0.1λ, and the second material layers include at least one second material layer with an optical thickness less than 0.1λ;

[0012] The second part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ;

[0013] The third part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layers is between 0.3λ and 0.45λ, and the second material layers include at least one first material layer with an optical thickness less than 0.1λ.

[0014] According to one aspect of the present application, a distributed Bragg reflection structure is also provided, comprising at least a first material layer and a second material layer stacked alternately, wherein the refractive index of the first material layer is smaller than the refractive index of the second material layer; wherein the first material layer comprises at least one first material layer whose optical thickness is smaller than the optical thickness of the second material layer.

[0015] According to one aspect of the present application, a distributed Bragg reflection structure is further provided, comprising at least a first material layer and a second material layer stacked alternately, wherein the refractive index of the first material layer is smaller than the refractive index of the second material layer; wherein

[0016] The first material layer includes several film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.1λ, and the optical thickness of the second material layer is less than 0.2λ; within the incident angle range of 30° to 60°, the transmittance of the distributed Bragg reflection structure to light is greater than or equal to 90%.

[0017] According to one aspect of the present application, there is also provided a light emitting diode, comprising at least:

[0018] a substrate having opposing first and second surfaces;

[0019] An epitaxial structure is formed on the first surface of the substrate, the epitaxial structure comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence;

[0020] A distributed Bragg reflection structure is located on a second surface of a substrate, the distributed Bragg reflection structure at least comprising a first material layer and a second material layer alternately stacked, wherein the refractive index of the first material layer is less than the refractive index of the second material layer; along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially comprises: a first part, comprising a plurality of first material layers with an optical thickness greater than 0.15λ, and at least one first material layer with an optical thickness less than 0.1λ; a second part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; and a third part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layer of the third part is greater than the optical thickness difference of the first material layer of the second part.

[0021] According to one aspect of the present application, there is also provided a light emitting diode, comprising at least:

[0022] a substrate having opposing first and second surfaces;

[0023] An epitaxial structure is formed on the first surface of the substrate, the epitaxial structure comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence;

[0024] A distributed Bragg reflection structure is located on the second surface of the substrate, the distributed Bragg reflection structure comprises at least a first material layer and a second material layer that are alternately stacked, the refractive index of the first material layer is less than the refractive index of the second material layer; wherein the first material layer comprises a plurality of film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.05λ, and the optical thickness of the second material layer is less than 0.2λ; within the incident angle range of 30° to 60°, the transmittance of the distributed Bragg reflection structure to light is greater than or equal to 90%.

[0025] According to one aspect of the present application, a light emitting device is also provided, the light emitting device comprising:

[0026] Package substrate;

[0027] At least one light emitting diode is arranged on the surface of the packaging substrate, and the packaging substrate is electrically connected to the electrode structure of the light emitting diode; the light emitting diode is the light emitting diode described in any one of the above technical solutions.

[0028] Compared with the prior art, the DBR structure, light emitting diode and light emitting device provided by the present application have at least the following advantages:

[0029] Beneficial effects:

[0030] The technical solution of the present application optimizes the module optical thickness of the distributed Bragg reflector structure, and the distributed Bragg reflector structure includes: a first part, including a plurality of first material layers with an optical thickness greater than 0.1λ, and at least one first material layer with an optical thickness less than 0.05λ; a second part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; a third part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layer of the third part is greater than the optical thickness difference of the first material layer of the second part. The above module design can effectively resist the problem of large-angle light transmission reduction caused by wavelength change, promote light of different wavelength bands to be emitted from the side and back of the light-emitting diode, thereby increasing the brightness of the chip and improving the uniformity of light output. Within the incident angle range of 30° to 60°, the transmittance of the DBR structure to light is greater than or equal to 90%, and within the incident angle range, as the incident angle changes, the DBR structure can always maintain a stable and uniform transmittance to light.

[0031] In addition, the light-emitting device provided in the present application includes the DBR structure and the light-emitting diode provided by the above technical solution. Therefore, the light-emitting device also has the above good technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the light reflection principle of a large-angle LED chip in the prior art;

[0033] Figure 2 A schematic diagram of the structure of a light emitting diode provided in this application;

[0034] Figure 3 A schematic diagram of a distributed Bragg reflection structure provided for this application;

[0035] Figure 4 A schematic diagram of the film system composition of the distributed Bragg reflection structure provided in this application;

[0036] Figure 5 A curve showing the variation of the reflectivity of the distributed Bragg reflection structure provided in the present application with the incident angle;

[0037] Figure 6 This is a schematic diagram of the structure of the light-emitting device provided in this application.

[0038] List of reference numerals:

[0039] 1. 100 Distributed Bragg Reflection Structure

[0040] 110 Part 1

[0041] 120 Part 2

[0042] 130 Part 3

[0043] 1001 First Material Layer

[0044] 1002 Second material layer

[0045] 200 Substrate

[0046] 300 Buffer layer

[0047] 4.400 epitaxial structure

[0048] 410 first semiconductor layer

[0049] 420 Active layer

[0050] 430 Second semiconductor layer

[0051] 5.500 insulation protection layer

[0052] 610 First Electrode

[0053] 620 Second Electrode

[0054] 10 Lighting device

[0055] 101 Package substrate

[0056] 102 Light-emitting element DETAILED DESCRIPTION

[0057] The following specific embodiments illustrate the implementation of the present application, and those familiar with the technology can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0058] It should be noted that the diagrams provided in the embodiments of the present application are only schematic illustrations of the basic concept of the present application. Although the diagrams only show the components related to the present application rather than the number, shape and size of the components in the actual implementation, the form, quantity and proportion of each component can be changed at will during the actual implementation, and the component layout form may also be more complex. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the restrictive conditions that can be implemented in the present application, so they have no technical substantive significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present application without affecting the effects and purposes that can be achieved by the present application.

[0059] See also Figure 1 In a conventional flip-chip LED chip, a reflective layer is provided on the back of the epitaxial structure (or substrate) and the front of the epitaxial structure. The reflective layer may include a distributed Bragg reflector (DBR) structure and a metal layer to reflect and / or transmit the light emitted by the epitaxial structure. It is worth noting that the angles of the light emitted by the epitaxial structure are different, for example, the angle between the small-angle light L1 and the large-angle light L2, the angle between the light L1 and the normal is between 0° and 30°, and the angle between the light L2 and the normal is between 30° and 60°. In order to ensure the large-angle light emission of the LED chip, the insulating protective layer 5 can fully reflect both the small-angle and large-angle light, while the distributed Bragg reflector structure 1 reflects the small-angle light, allows the large-angle light to pass through, and promotes the light to be emitted from the side and back to achieve the purpose of increasing the light emission angle. However, the wavelength band in which the LED chip can maintain a good large-angle light emission is limited. As the wavelength changes, the reflectivity and transmittance of the LED chip to the large-angle light also change, resulting in poor chip light emission uniformity, increased light loss, and reduced chip brightness. Based on the background technology and the above technical defects, the present application provides a DBR structure, a light emitting diode and a light emitting device to effectively solve or improve the above technical problems. The technical solution of the present application is described in detail below through embodiments.

[0060] For ease of description, the direction from the substrate to the epitaxial structure is defined as upward, and the opposite direction is defined as downward; the insulating protection layer is located above the epitaxial structure (front side); and the distributed Bragg reflection structure is located below the epitaxial structure (back side).

[0061] like Figure 2-3 As shown, this embodiment provides a light emitting diode, which at least includes a distributed Bragg reflection structure 100, a substrate 200, an epitaxial structure 400 and an insulating protection layer 500, specifically:

[0062] See also Figure 2 to Figure 4The distributed Bragg reflection structure 100 includes at least a first material layer 1001 and a second material layer 1002 that are alternately stacked, and the refractive index of the first material layer 1001 is less than the refractive index of the second material layer 1002. The first material layer 1001 and the second material layer 1002 can be oxides of different materials, which have different refractive indices and are optically transparent, such as SiO2, SiN, SiO x N y , TiO2, Si3N4, Al2O3, TiN, AlN, ZrO2, TiAlN or TiSiN oxides or nitrides. Since SiO2 material and TiO2 material have high light transmittance, easy deposition and relatively large refractive index difference, in this embodiment, the first material layer is preferably SiO2, whose refractive index is about 1.47, and the second material layer is preferably TiO2, whose refractive index is about 2.55. It can be understood that the first material layer 1001 and the second material layer 1002 are not limited to the above-mentioned SiO2 layer and TiO2 layer.

[0063] This embodiment provides a distributed Bragg reflection structure. Figure 3 Along the thickness direction of the distributed Bragg reflection structure, that is, from bottom to top, the distributed Bragg reflection structure 100 is divided into a first part 110, a second part 120 and a third part 130 in sequence. By improving the design of the film system of the distributed Bragg reflection structure 100, the structure optimizes the reflection angle range and the transmission angle range under the premise of having small-angle reflection and large-angle transmission, and is suitable for reflection and transmission light of different wavelengths at the same time. The optimized film system can effectively resist the problems of large-angle transmittance fluctuation and transmittance weakening caused by wavelength changes.

[0064] The first material layer 1001 and the second material layer 1002 of the distributed Bragg reflection structure 100 are described in detail below.

[0065] See also Figure 3-4, the first part 110 includes a plurality of first material layers 1001 with an optical thickness greater than 0.25λ and a plurality of first material layers 1001 with an optical thickness less than 0.25λ. Specifically, the first part 110 includes a plurality of first material layers with an optical thickness greater than 0.1λ and at least one first material layer with an optical thickness less than 0.05λ. Further, the first part 110 includes a plurality of first material layers with an optical thickness greater than 0.15λ and at least one first material layer with an optical thickness less than 0.05λ. The first material layer with the smallest optical thickness in the first part 110 (the first minimum thickness layer) can be any middle layer of the first part 110, rather than being located at the starting layer or the last layer of the first part 110. Further, the two first material layers above and below the first material layer with the smallest optical thickness both have a large optical thickness, for example, greater than 0.30λ or greater than 0.35λ, that is, the first material layer 1001 of the first part 110 is configured as a film group with a large optical thickness difference and fluctuation, so that the maximum difference in the optical thickness of the first material layer in the first part 110 is greater than or equal to 0.3λ. By changing the thickness of certain layers in the middle of the first part 110, the phase of the reflected light can be adjusted, so as to achieve constructive interference at a specific wavelength and enhance the reflectivity. Adjust the position or intensity of the defect mode, and the specific reflection or transmission characteristics to meet specific application requirements. The reflection bandwidth of the DBR structure depends on multiple factors such as the refractive index difference, thickness and number of periods of each layer of material. By adjusting the thickness difference of the first material layer in the first part 110, for example, making the thickness of certain layers thinner or thicker, it is also possible to compensate for the error caused by process fluctuations, and achieve precise control of the reflection bandwidth to ensure that the performance of the overall DBR structure 100 meets the design requirements. Further, the first material layers adjacent to the first minimum thickness layer above and below are the two first material layers with the largest optical thickness in the first portion 110. Specifically, the two first material layers with the largest optical thickness are both greater than 0.30λ or greater than 0.35λ. Further, the difference between the optical thickness of the minimum first thickness layer and the optical thickness of the first material layers adjacent to it on both sides is greater than 0.3λ.

[0066] In some embodiments, the number of membrane groups alternately stacked in the first portion 110 is between 3 and 8 pairs, for example, 4, 5, 6 or 7 pairs. Further, the number of membrane groups alternately stacked in the first portion 110 is between 4 and 6 pairs. Figure 4 In the DBR structure provided in this embodiment, the first part 110 includes 10 material layers from the 1st layer to the 10th layer from bottom to top, that is, 5 pairs of membrane groups.

[0067] In some embodiments, the first portion 110 includes a plurality of film groups, each of which includes adjacent first material layers 1001 and second material layers 1002, wherein the optical thickness of the first material layer in at least one film group is less than the optical thickness of the second material layer. It can be understood that the number of film groups having the above characteristics increases or decreases according to the number of material layers in the first portion 110. Figure 4 In the DBR structure provided in this embodiment, only one pair of film groups has an optical thickness of the first material layer that is smaller than the optical thickness of the second material layer. The film group is located in the fourth pair arranged from bottom to top in the first part 110 .

[0068] In the above embodiment, the optical thickness of the second material layer 1002 is less than or equal to 0.2λ, and the optical thickness of the second material layer 1002 is gradually distributed in a "V" shape from bottom to top, that is, the optical thickness of the second material layer 1002 shows a trend of first decreasing and then increasing. Further, the optical thickness of the second material layer 1002 is less than or equal to 0.15λ. For all layers other than the first material layer with the smallest optical thickness in the first part 110, the optical thickness of the first material layer 1001 in the first part 110 is greater than the optical thickness of the second material layer 1002 in the first part 110. Further, in each DBR material layer pair, for all layers other than the first minimum thickness layer, the optical thickness of the first material layer 1001 in each layer pair is greater than the optical thickness of the second material layer 1002 in the same layer pair. Further, the optical thickness of the second material layer 1002 of the first part 110 is distributed in a "V" shape from bottom to top, the first material layer with the smallest optical thickness in the first part 110 is in contact with the second material layer with the smallest optical thickness, and the second material layers in contact with the first minimum thickness layer above and below are the two minimum thickness layers of the first part 110, that is, the three smallest material layers in the first part 110 are the second material layer / first material layer / second material layer in sequence, and the optical thickness of the first material layer located in the middle of the interlayer is smaller than the optical thickness of the second material layers on both sides. Further, the optical thickness of the three interlayers is less than 0.1λ. Further, among the second material layers in contact with the smallest first thickness layer, at least one layer has an optical thickness less than 0.05λ.

[0069] Continue to see Figure 3-4, the optical thickness of the first material layer 1001 in the second portion 120 is between 0.3λ and 0.45λ, and the optical thickness of the second material layer 1002 in the second portion 120 is between 0.1λ and 0.2λ. It can be understood that the light absorption rate of the material layer with a high refractive index is higher than that of the material layer with a low refractive index. Therefore, the optical thickness of the first material layer 1001 with a low refractive index is designed to be greater than the optical thickness of the second material layer 1002 with a high refractive index. Further, the optical thickness of the first material layer 1001 in the second portion 120 is between 0.35λ and 0.45λ, and the optical thickness of the second material layer 1002 in the second portion 120 is between 0.1λ and 0.15λ. Specifically, in the second region 120 with a relatively large optical thickness and a relatively large number of film groups, the thickness of the second material layer 1002 can be relatively reduced to reduce the brightness loss caused by the second material layer 1002 absorbing light. The optical thickness of the first material layer 1001 in the second part 120 can be set in alternating thickness of "thick-thin-thick" in sequence, or can be set in irregular thickness, as long as the optical thickness is between 0.30λ and 0.45λ, any thickness can be used, and the thickness of the first material layer in the second part 120 can be adjusted according to actual applications to achieve a stable reflectivity and reflection band of the DBR structure to light. Further, the optical thickness of the first material layer 1001 in the second part 120 is between 0.37λ and 0.42λ. The thickness setting of the second material layer 1002 in the second part 120 is similar, and will not be repeated here.

[0070] In some embodiments, the maximum difference in optical thickness of the first material layer 1001 in the second portion 120 is less than or equal to 0.05λ, that is, the thickness of the first material layer in the second portion 120 is relatively uniform to maintain a relatively stable reflection characteristic. Similarly, the thickness of the second material layer in the second portion 120 is also relatively uniform, and the maximum difference in optical thickness is also less than or equal to 0.05λ to match the optical thickness of the first material layer in the portion. Further, the maximum difference in optical thickness of the first material layer 1001 in the second portion 120 is less than or equal to 0.03λ, and the maximum difference in optical thickness of the second material layer 1002 is less than or equal to 0.03λ.

[0071] In some embodiments, the optical thickness of the first first material layer in the second portion 120 is the same as the optical thickness of the last first material layer in the first portion 110, or the difference in optical thickness is less than 0.01λ. Further, the last first material layer in the first portion 110 may be the material layer with the largest optical thickness in the first portion 110 adjacent to the layer with the smallest first thickness.

[0072] In some embodiments, the optical thickness of the first second material layer in the second portion 120 is the same as the optical thickness of the last second material layer in the first portion 110, or the difference in optical thickness is less than 0.01λ. Further, the two second material layers with the largest optical thickness in the first portion 110 are the starting layer and the ending layer of the first portion 110, respectively, the first second material layer in the second portion 120 is in contact with the ending layer of the first portion 110, and the optical thickness of the ending layer is between 0.11λ and 0.14λ.

[0073] In some embodiments, the number of film groups alternately stacked in the second part 120 is between 4 and 10 pairs, for example, 5 pairs, 6 pairs, 8 pairs or 9 pairs. Further, the number of film groups alternately stacked in the second part 120 is between 5 and 7 pairs. Further, the number of film groups alternately stacked in the second part 120 is greater than the number of film groups alternately stacked in the first part 120 to ensure that the DBR structure has more stable reflection characteristics. It is understandable that the number of film groups alternately stacked in the second part should not be too large, for example, more than 10 pairs, which may have a negative impact on the light absorption of the material layer and increase the difficulty of the process. See Figure 4 In the DBR structure provided in this embodiment, the second part 120 includes 12 material layers from the 11th layer to the 22nd layer from bottom to top, that is, 6 pairs of membrane groups, which is greater than the 5 pairs of membrane groups in the first part 110.

[0074] Continue to see Figure 3-4 , the optical thickness of the first material layer 1001 in the third part 130 is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layer 1001 in the third part 130 is greater than the optical thickness difference of the first material layer 1001 in the second part 120, that is, the thickness fluctuation of the first material layer in the third part 130 is greater than that of the first material layer in the second part 120, but it is still within a relatively uniform optical thickness range, and the thickness of one or several layers is not designed to increase or decrease sharply. Further, the optical thickness of the first material layer 1001 in the third part 130 is between 0.35λ and 0.45λ.

[0075] In some embodiments, the third part 130 includes a first group and a second group of cross-stacked first material layers 1001, and the optical thickness of the first material layer of the first group is greater than the optical thickness of the first material layer of the second group adjacent to it, wherein the optical thickness of the first material layer of the first group is between 0.4λ±10%; the optical thickness of the first material layer of the second group is between 0.37λ±10%. The above optical thickness setting can increase the reflectivity of the DBR structure in a wavelength range longer than the central wavelength.

[0076] In some embodiments, the optical thickness of the second material layer 1002 of the third portion 130 is set to decrease from bottom to top, and the first second material layer 1002 in the third portion 130 adjacent to the last second material layer in the second portion 120 has the maximum optical thickness, and the optical thickness of the layer is between 0.10λ and 0.15λ. Further, the optical thickness of the first second material layer in the third portion 130 is between 0.11λ and 0.14λ. Further, the average optical thickness of the second material layer 1002 of the second portion 120 is greater than the average optical thickness of the second material layer 1002 of the third portion 130.

[0077] In some embodiments, the number of film groups alternately stacked in the third part 130 is between 2 and 6 pairs, such as 3 pairs, 4 pairs, or 5 pairs. For the DBR structure as a whole, the more layers of the DBR, the higher the reflectivity in theory, but it will also increase the manufacturing complexity and cost. The number of film groups alternately stacked in the third part 130 is less than the number of film groups alternately stacked in the second part 120, so as to ensure that the DBR structure has more stable reflection characteristics and the cost and process difficulty are controllable. Figure 4 In the DBR structure provided in this embodiment, the third part 130 includes 8 material layers from the 23rd layer to the 30th layer from bottom to top, that is, 4 pairs of membrane groups, which is less than the 6 pairs of membrane groups in the second part 120.

[0078] In some embodiments, the starting layer of the first part 110, that is, the first material layer of the bottom layer, can be the first material layer 1001 or the second material layer 1002. Generally, since the bonding strength of SiO2 is higher than that of TiO2, the last layer of the distributed Bragg reflection structure 100 in contact with the substrate 200, that is, the top material layer, is preferably the first material layer 1001 of SiO2 material, and the optical thickness design of the layer can meet the film system design requirements of the third part 130.

[0079] See also Figure 3 This embodiment also provides a distributed Bragg reflection structure. In the DBR structure, the multiple first material layers include at least one first material layer whose optical thickness is smaller than the optical thickness of the second material layer.

[0080] In an optional implementation manner, the optical thickness of the first material layer 1001 with the minimum optical thickness is less than 0.05λ, and the optical thicknesses of the first material layers 1001 adjacent to the first material layer 1001 on both sides are greater than 0.3λ. Further, along the thickness direction of the distributed Bragg reflector structure, it includes a first portion 110, a second portion 120 and a third portion 130 in sequence:

[0081] The first part 110 includes a plurality of first material layers 1001 and a plurality of second material layers 1002 , wherein the first material layer 1001 includes a plurality of first material layers with an optical thickness greater than 0.1λ and at least one first material layer with an optical thickness less than 0.05λ;

[0082] The second portion 120 and the third portion 130 each include a plurality of first material layers 1001 and a plurality of second material layers 1002 , wherein the optical thickness of the first material layer 1001 is between 0.3λ and 0.45λ;

[0083] The first material layer having the smallest optical thickness is located in the plurality of first material layers of the first portion 110 .

[0084] In an optional implementation manner, the optical thickness of the second material layer 1002 is less than 0.2λ. Further, the optical thickness of the second material layer 1002 is less than 0.15λ.

[0085] In an optional embodiment, the first portion 110 includes a plurality of film groups, each film group includes adjacent first material layers 1001 and second material layers 1002, wherein the optical thickness of the first material layer in at least one film group is less than the optical thickness of the second material layer.

[0086] This embodiment also provides a distributed Bragg reflection structure having the following characteristics:

[0087] The first part 110 includes a plurality of first material layers and a plurality of second material layers, wherein the first material layers include at least one first material layer having an optical thickness less than 0.1λ, and the second material layers include at least one second material layer having an optical thickness less than 0.1λ;

[0088] The second portion 120 includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ;

[0089] The third portion 130 includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layers is between 0.3λ and 0.45λ, and the second material layers include at least one first material layer with an optical thickness less than 0.1λ;

[0090] Among them, λ is 444nm.

[0091] When the layer thickness meets specific phase conditions, the DBR structure may exhibit a transmission window at certain wavelengths, thereby increasing the transmittance. As the incident angle increases, the optical path difference of each film layer decreases, and the reflection spectrum of the DBR structure moves toward the short wavelength direction. When the angle of the incident light is large, the propagation path of the light in the DBR layer increases, resulting in a phase change, which may cause the reflected light to no longer match the phase of the incident light, thereby reducing the reflectivity and allowing more light to pass through. In contrast, the phase change of small-angle incident light is small, so the reflectivity is higher. The above-mentioned module design can effectively resist the problem of large-angle light transmittance reduction caused by wavelength changes, promote large-angle incident light of different bands to be emitted from the side and back of the light-emitting diode, and improve the uniformity of the light output. Within a large range of incident angles, as the incident angle changes, the DBR structure configured with the above-mentioned film system can always maintain a stable and uniform transmittance for light.

[0092] Continue to see Figure 2 , substrate 200 is located on the DBR structure 100, and substrate 100 can be any transparent substrate including a sapphire substrate or a SiC substrate but is not limited thereto. Further, substrate 200 may have a predetermined pattern formed on its upper surface, such as a patterned sapphire substrate (PSS). Since the patterned sapphire substrate has a better transmittance for light with an incident angle range of 20° to 50°, it can more effectively exhibit favorable effects in conjunction with the large-angle DBR structure provided in the present application. The thickness of substrate 100 is between 100μm and 500μm.

[0093] Continue to see Figure 2 The buffer layer 300 is located on the substrate 200, specifically between the substrate 200 and the epitaxial structure 300. The buffer layer 300 is an n-type material layer made of GaN-based III-V nitride semiconductor, or an undoped material layer, or a combination of multiple layers with gradient components, which is used to adjust the warping of the substrate 200 to improve the wavelength uniformity.

[0094] Continue to see Figure 2, the epitaxial structure 400 is located on the buffer layer 300, and includes a first semiconductor layer 410, an active layer 420, and a second semiconductor layer 430 stacked in sequence. Among them, the first semiconductor layer 410 is composed of a III-V group or a II-VI group compound semiconductor, doped with an N-type dopant such as Si, Ge, Sn, Se, or Te, and is an N-type semiconductor layer; the second semiconductor layer 430 is composed of a III-V group or a II-VI group compound semiconductor, doped with a P-type dopant such as Mg, Zn, Ca, Sr, or Ba, and is a P-type semiconductor layer. At this time, the first semiconductor layer 410 is used to provide electrons for composite luminescence, and the second semiconductor layer 430 is used to provide holes for composite luminescence. The active layer 420 may have, but is not limited to, any one of a single well structure, a multi-well structure, a single quantum well structure, or a multi-quantum well structure, and is used for composite luminescence of electrons and holes. The wavelength of light emitted from the active layer 420 may vary depending on the material of the active layer 420. Therefore, the DBR structure can be made with reference to the central wavelength λ and the first wavelength λ1 and the second wavelength λ2. The central wavelength λ of this embodiment is 444nm, the first wavelength λ1 is 410nm, and the second wavelength λ2 is 480nm, so as to achieve effective reflection of the light emitted from the active layer, while maintaining a high reflectivity relative to the light entering the DBR at various small-angle incident angles of the DBR structure. When the light rays of various angles emitted from the active layer 420 reach the DBR structure on the back of the substrate 200, the small-angle light rays are reflected back to the inside of the LED by the DBR structure 100, and a part of the small-angle light rays are reflected multiple times by the insulating protective layer 500 and the DBR structure 100 on the front of the LED to form large-angle light rays, which are emitted from the back of the LED chip, and another part of the small-angle light rays are converted into heat loss during the multiple reflection process inside the LED chip. The large-angle light rays are emitted directly through the DBR structure 100 on the back of the LED chip, thereby ensuring the large-angle light emission of the chip.

[0095] Continue to see Figure 2 , an insulating protective layer 500 is formed on the epitaxial structure 400 to reflect the light reflected from the epitaxial structure 400 and the distributed Bragg reflector structure 100. In an optional embodiment, the insulating protective layer 500 can be set as a DBR layer, which includes alternately stacking a first material layer and a second material layer, the first material layer has a first refractive index, such as a SiO2 layer, whose refractive index is about 1.47, and the second material layer has a second refractive index, such as a TiO2 layer, whose refractive index is about 2.55. The insulating protective layer 500 can reflect almost all the light from the inside of the chip back to the chip, and promote the light to be emitted at a large angle at the back of the chip.

[0096] In some embodiments, the light emitting diode chip may further include an intermediate layer, which is disposed between the substrate 200 and the DBR structure 200 and has the same material composition as the first material layer 100 in the DBR structure 200, wherein the intermediate layer has a greater thickness than the first material layer 1001. The insertion of the intermediate layer reduces the influence of the rough bottom surface of the substrate 200 on the DBR formed on the bottom and back sides of the substrate.

[0097] In some embodiments, the light-emitting diode chip may further include a surface layer disposed on the DBR, the surface layer being formed of the same material as the first material layer in the DBR, such as SiO2, and having a thickness greater than the first material layer. The surface layer may prevent the DBR structure from being damaged by the rough surface of the light-emitting diode mounting plane during packaging.

[0098] The light-emitting diode provided in this embodiment is a flip-chip light-emitting diode that emits blue light, and the emission wavelength is between 410nm and 480nm. The flip-chip light-emitting diode is a small-sized flip-chip light-emitting diode, such as a mini flip-chip light-emitting diode or a micro flip-chip light-emitting diode.

[0099] This embodiment also provides a distributed Bragg reflection structure. Figure 2 to Figure 5 , at least comprising alternately stacked first material layers 1001 and second material layers 1002, the refractive index of the first material layer 1001 being less than the refractive index of the second material layer 1002, the first material layer is preferably SiO2, whose refractive index is about 1.47, and the second material layer is preferably TiO2, whose refractive index is about 2.55. The first material layer 1001 comprises several film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.1λ, and the optical thickness of the second material layer 1002 is less than 0.2λ. The peak wavelength of the light radiated by the light-emitting diode provided in this embodiment is between 410nm and 480nm, and within the incident angle range of 30° to 60°, the transmittance of the distributed Bragg reflection structure 100 to light is greater than or equal to 90%. Furthermore, in the distributed Bragg reflection structure provided in this embodiment, the first material layer 1001 includes several film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.05λ, and the optical thickness of the second material layer 1002 is less than 0.15λ, where λ is 444nm.

[0100] See also Figure 5 In some embodiments, the reflectivity of the distributed Bragg reflection structure 100 to light forms a reflection curve as the incident angle increases. The reflection curve includes a first reflection segment, a platform segment, a second reflection segment, and a light-transmitting segment connected in sequence.

[0101] The following is a detailed description of the changes in each segment of the light reflection curve. Figure 5 This embodiment provides three "incident angle-reflectivity" curves with a central wavelength λ of 444nm, a first wavelength λ1 of 410nm and a second wavelength λ2 of 480nm, corresponding to the central curve C, the first curve C1 and the second curve C2 respectively.

[0102] First, as the incident angle increases from 0 degrees to a certain angle, the reflectivity of the DBR structure for light of each wavelength is close to 100%, that is, all small-angle light can be reflected back into the LED. This curve is the starting section. Figure 5 It can be seen that the initial reflection curves of the three curves are basically overlapped, and the reflectivity of the second curve C2 in the incident angle range of 0 to 15 degrees, the central curve C in the incident angle range of 0 to 25 degrees, and the first curve in the incident angle range of 0 to 30 degrees are all close to 100%.

[0103] As the incident angle continues to increase, the reflectivity of the light in the initial section reaches the first steep drop inflection point and then drops rapidly until it reaches the platform section. The curve section where the reflectivity drops sharply is the first reflection section. The incident angle range corresponding to the first reflection section is narrow, and the reflectivity changes greatly, usually dropping from a reflectivity close to 100% to about 50%. For light of different wavelengths, the angle span of the first reflection section is basically the same, and the angle span does not change with the change of wavelength. Furthermore, the starting angle of the first reflection section changes with the change of wavelength. The shorter the wavelength, the larger the steep drop starting angle of the first reflection section; the longer the wavelength, the smaller the steep drop starting angle of the first reflection section.

[0104] As the incident angle continues to increase, the reflectivity of the first reflection segment reaches the platform segment and then becomes stable. The light reflectivity of the platform segment is between 40% and 60%. Furthermore, the angle range of the platform segment is between 5 and 15 degrees. Depending on the wavelength of the emitted light, the curve characteristics of the platform segment are also different. The shorter the wavelength, the longer the platform segment; the longer the wavelength, the shorter the platform segment. For light of different wavelength bands, the light reflectivity range of the platform segment is the same, and this value does not change with the change of wavelength. Furthermore, the light emissivity of the platform segment is between 50% and 55%. Figure 5 It can be seen that the reflectivity of the platform segments of the three curves is about 50%, among which the incident angle range of the platform segment of the second curve C2 is smaller, between 20 degrees and 25 degrees; the incident angle range of the platform segment of the center curve C increases, between 25 degrees and 35 degrees; the incident angle range of the platform segment of the first curve C1 continues to increase, between 35 degrees and 45 degrees.

[0105] As the incident angle continues to increase, the light reflectivity of the platform segment reaches the second steep drop inflection point and then continues to drop rapidly to form the second reflection segment. The light reflectivity of the second reflection segment also shows a downward trend until it reaches the light transmission segment. Similar to the first reflection segment, the incident angle range corresponding to the second reflection segment is also narrow, and the reflectivity changes greatly, usually dropping from a reflectivity of nearly 50% to below 10%. For light of different wavelengths, the angle span of the second reflection segment is basically the same, and the angle span does not change with the change of wavelength. Furthermore, the starting angle of the second reflection segment changes with the change of wavelength. The shorter the wavelength, the smaller the steep drop starting angle of the second reflection segment; the longer the wavelength, the larger the steep drop starting angle of the second reflection segment.

[0106] As the incident angle continues to increase, the reflectivity of the second reflective section reaches the light-transmitting section and then becomes stable again, and the light reflectivity of the light-transmitting section is less than 10%. Furthermore, the average reflectivity of the light-transmitting section is less than 5%. Figure 5 It can be seen that the reflectivity of the light-transmitting sections of the three curves is below 10%, or less than 5%. Among them, the light-transmitting section of the second curve C2 has the largest incident angle range, between 25 degrees and 60 degrees, and the reflectivity is less than 5%; the incident angle range of the light-transmitting section of the central curve C becomes smaller, between 35 degrees and 60 degrees, and the reflectivity is also less than 5%; the incident angle range of the light-transmitting section of the first curve C1 becomes further smaller, between 45 degrees and 60 degrees, and the average reflectivity is still less than 5%.

[0107] By precisely controlling the thickness and material properties of each layer of material, light can be caused to interfere constructively multiple times in the DBR structure, thereby significantly changing the reflectivity of the light, and making the DBR structure have a very high or very low reflectivity within a specific wavelength range, even close to 100% or 0%. By adjusting the thickness and refractive index difference of the DBR layer, the DBR can be designed to reflect or transmit light within a specific wavelength range, thereby achieving control of the LED emission spectrum. Figure 5 It can be seen that within the incident angle range of 30° to 60°, as the wavelength of the incident light becomes shorter, the platform section of the reflection curve becomes longer, and the length of the light-transmitting section becomes shorter, and the length of the platform section and the light-transmitting section are complementary. As the wavelength changes, the reflection curve only shifts, and the light transmission does not weaken, which effectively resists the reflectivity fluctuations and severe deformation of the reflection curve caused by wavelength changes.

[0108] Embodiment 2:

[0109] See also Figure 6, this embodiment also provides a light-emitting device 10, which is a flip-chip LED product, including a packaging substrate 101; at least one light-emitting diode is arranged on the surface of the packaging substrate 101, and the packaging substrate 101 is electrically connected to the electrode structure of the light-emitting diode. The light-emitting element 102 is the light-emitting diode provided in the first embodiment of the present application, and the light-emitting diode is electrically connected to the packaging substrate 101 through the first electrode 610 and the second electrode 620. The light-emitting diode provided in the first embodiment can effectively resist the problem of weakened light transmission at large angles caused by wavelength changes by optimizing the film system composition of the distributed Bragg reflection structure, and promotes light of different wavelength bands to be emitted from the side and back of the light-emitting diode, thereby increasing the brightness of the chip and improving the uniformity of light output. Therefore, the light-emitting device 10 also has the above-mentioned excellent effects.

[0110] In summary, the DBR structure, light emitting diode and light emitting device provided by the present application effectively overcome various shortcomings in the prior art and have high industrial utilization value.

[0111] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A distributed Bragg reflection structure, characterized in that: At least comprises a first material layer and a second material layer which are alternately stacked, wherein the refractive index of the first material layer is smaller than the refractive index of the second material layer; Along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially comprises: The first part includes a plurality of first material layers and a plurality of second material layers, wherein the first material layer includes a plurality of first material layers with an optical thickness greater than 0.1λ and at least one first material layer with an optical thickness less than 0.05λ; The second part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; The third part includes multiple first material layers and multiple second material layers, wherein the optical thickness of the first material layers is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layers in the third part is greater than the optical thickness difference of the first material layers in the second part.

2. A distributed Bragg reflection structure, characterized in that: At least comprises a first material layer and a second material layer which are alternately stacked, wherein the refractive index of the first material layer is smaller than the refractive index of the second material layer; Along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially comprises: The first part includes a plurality of first material layers and a plurality of second material layers, wherein the first material layers include at least one first material layer with an optical thickness less than 0.1λ, and the second material layers include at least one second material layer with an optical thickness less than 0.1λ; The second part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; The third part includes a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layers is between 0.3λ and 0.45λ, and the second material layers include at least one first material layer with an optical thickness less than 0.1λ.

3. A distributed Bragg reflection structure, characterized in that: At least comprises a first material layer and a second material layer which are alternately stacked, wherein the refractive index of the first material layer is smaller than the refractive index of the second material layer; The first material layer includes at least one first material layer whose optical thickness is smaller than the optical thickness of the second material layer.

4. The distributed Bragg reflection structure according to claim 3, characterized in that: The optical thickness of the first material layer with the minimum optical thickness is less than 0.05λ, and the optical thicknesses of the first material layers adjacent to the first material layer on both sides are greater than 0.3λ.

5. The distributed Bragg reflection structure according to claim 3, characterized in that: Along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure includes a first part, a second part and a third part in sequence: The first part includes a plurality of first material layers and a plurality of second material layers, the first material layers include a plurality of first material layers with an optical thickness greater than 0.1λ, and at least one first material layer with an optical thickness less than 0.05λ; The second part and the third part each include a plurality of first material layers and a plurality of second material layers, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; The first material layer having the smallest optical thickness is located in the first material layer of the first portion.

6. The distributed Bragg reflection structure according to claim 4 or 5, characterized in that: The optical thickness of the second material layer is less than 0.2λ.

7. The distributed Bragg reflection structure according to claim 4 or 5, characterized in that: The first part includes a plurality of film groups, each of the film groups includes adjacent first material layers and second material layers, wherein the optical thickness of the first material layer in at least one film group is smaller than the optical thickness of the second material layer.

8. The distributed Bragg reflection structure according to claim 1 or 2, characterized in that: The distributed Bragg reflection structure includes at least one first material layer whose optical thickness is smaller than the optical thickness of the second material layer.

9. The distributed Bragg reflection structure according to any one of claims 1 to 3, characterized in that: The maximum difference in optical thickness of the first material layer in the first portion is greater than or equal to 0.3λ.

10. The distributed Bragg reflection structure according to any one of claims 1 to 3, characterized in that: The maximum difference in optical thickness of the first material layer in the second portion is less than or equal to 0.05λ.

11. The distributed Bragg reflection structure according to any one of claims 1 to 3, characterized in that: The number of membrane groups alternately stacked in the second part is greater than the number of membrane groups alternately stacked in the first part; the number of membrane groups alternately stacked in the second part is greater than the number of membrane groups alternately stacked in the third part.

12. The distributed Bragg reflection structure according to claim 11, characterized in that: The number of membrane groups alternately stacked in the first part is between 3 and 8 pairs; The number of membrane groups alternately stacked in the second part is between 4 and 10 pairs; The number of the alternately stacked membrane groups in the first part is between 2 and 6 pairs.

13. The distributed Bragg reflection structure according to any one of claims 1 to 3, characterized in that: The optical thickness of the second material layer is less than or equal to 0.2λ.

14. The distributed Bragg reflection structure according to any one of claims 1 to 3, characterized in that: The first material layer having the minimum optical thickness is in contact with the second material layer having the minimum optical thickness.

15. The distributed Bragg reflection structure according to claim 1 or 2, characterized in that: The first part includes a plurality of film groups, each of the film groups includes adjacent first material layers and second material layers, wherein the optical thickness of the first material layer in at least one film group is smaller than the optical thickness of the second material layer.

16. A distributed Bragg reflection structure, characterized in that: At least includes a first material layer and a second material layer alternately stacked, the refractive index of the first material layer is less than the refractive index of the second material layer; wherein the first material layer includes a plurality of film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.1λ, and the optical thickness of the second material layer is less than 0.2λ; within the incident angle range of 30° to 60°, the transmittance of the distributed Bragg reflection structure to light is greater than or equal to 90%.

17. The distributed Bragg reflection structure according to claim 16, characterized in that: The first part includes a plurality of film groups, each of the film groups includes adjacent first material layers and second material layers, wherein the optical thickness of the first material layer in at least one film group is smaller than the optical thickness of the second material layer.

18. The distributed Bragg reflection structure according to claim 1, 2, 3 or 16, characterized in that: The first material layer is SiO2, and the second material layer is TiO2.

19. A light emitting diode, characterized in that: At least: a substrate having opposing first and second surfaces; An epitaxial structure is formed on the first surface of the substrate, the epitaxial structure comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; A distributed Bragg reflection structure, located on the second surface of the substrate, the distributed Bragg reflection structure at least comprising a first material layer and a second material layer stacked alternately, the refractive index of the first material layer being less than the refractive index of the second material layer; Along the thickness direction of the distributed Bragg reflection structure, the distributed Bragg reflection structure sequentially includes: a first part, including a plurality of first material layers with an optical thickness greater than 0.15λ, and at least one first material layer with an optical thickness less than 0.1λ; The second part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ; the third part, wherein the optical thickness of the first material layer is between 0.3λ and 0.45λ, and the optical thickness difference of the first material layer of the third part is greater than the optical thickness difference of the first material layer of the second part.

20. A light emitting diode, characterized in that: At least: a substrate having opposing first and second surfaces; An epitaxial structure is formed on the first surface of the substrate, the epitaxial structure comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; A distributed Bragg reflection structure is located on the second surface of the substrate, the distributed Bragg reflection structure comprises at least a first material layer and a second material layer that are alternately stacked, the refractive index of the first material layer is less than the refractive index of the second material layer; wherein the first material layer comprises a plurality of film layers with an optical thickness greater than 0.35λ and at least one film layer with an optical thickness less than 0.05λ, and the optical thickness of the second material layer is less than 0.2λ; within the incident angle range of 30° to 60°, the transmittance of the distributed Bragg reflection structure to light is greater than or equal to 90%.

21. The light emitting diode according to claim 19 or 20, characterized in that: The substrate is a patterned sapphire substrate.

22. The light emitting diode according to claim 19 or 20, characterized in that: Also includes: The insulating reflective layer is located on the second surface of the epitaxial structure to reflect the light reflected from the epitaxial structure and the distributed Bragg reflective structure.

23. The light emitting diode according to claim 19 or 20, characterized in that: The peak wavelength of the light radiated by the light emitting diode is 444 nm.

24. A light emitting device, characterized in that: The light emitting device comprises: Package substrate; At least one light emitting diode is arranged on the surface of the packaging substrate, and the packaging substrate is electrically connected to the electrode structure of the light emitting diode; the light emitting diode is the light emitting diode according to any one of claims 19 to 23.

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