CN114551666A - LED epitaxial wafer, epitaxial growth method and LED chip - Google Patents

Abstract

The invention provides an LED epitaxial wafer, an epitaxial growth method and an LED chip₃Superlattice layer and deposition on Al/AlN/NH₃Al/AlN/H on superlattice layer₂A superlattice layer, wherein Al/AlN/NH₃The superlattice layer is composed of an Al sublayer, an AlN sublayer and NH₃Periodic structure of Al/AlN/H with sub-layers alternately and cyclically grown₂The superlattice layer is composed of an Al sublayer, an AlN sublayer and H₂The sub-layers are cyclically and alternately grown to form a periodic structure. Due to Al/AlN/NH₃The superlattice layer grows in a three-dimensional mode, Al/AlN/H₂The superlattice layer grows in a two-dimensional mode, and a relatively flat epitaxial layer can be obtained by covering the grown three-dimensional Al/AlN superlattice layer, so that the problem that crystal quality of epitaxial growth in the existing ultraviolet light-emitting diode is poor is solved.

Description

A kind of LED epitaxial wafer, epitaxial growth method and LED chip

technical field

The invention relates to the technical field of LEDs, in particular to an LED epitaxial wafer, an epitaxial growth method and an LED chip.

Background technique

In the past ten years, AlGaN materials have attracted much attention due to their huge application potential in ultraviolet optoelectronic devices. Ultraviolet LEDs have the characteristics of high photon energy, short wavelength, small size, low power consumption, long life, and environmental friendliness. Color rendering index white light lighting, high-density optical data storage, sensors, lithography, air purification, environmental protection and other fields have a wide range of applications.

The development of AlGaN-based UV LEDs faces many technical difficulties. First, the electrons themselves have small effective mass and high mobility, so that many electrons can easily pass through the quantum well and overflow to the P layer; second, with the increase of Al composition It is easy to cause problems such as high defect density and uneven surface of epitaxially grown AlGaN films, and it is difficult to obtain AlGaN materials with high crystal quality. For GaN materials, AlGaN materials are much more difficult, especially the doping of P-AlGaN is particularly difficult, the activation efficiency of the dopant Mg is low, resulting in insufficient holes and reduced radiation recombination efficiency; Oxygen atoms decomposed by the oxides of the epitaxial growth at high temperature will diffuse upward with the growth of the epitaxial layer. Due to the high Al composition in the epitaxial layer of the UV LED, the Al atoms have a strong adsorption to the oxygen atoms. Therefore, the content of oxygen atoms in the epitaxial layer is high, the background carrier concentration is high, and the crystal quality will decrease, and the luminous efficiency of UV LED is closely related to its crystal quality. The higher the efficiency. In order to improve the photoelectric capability of UV LEDs, it is necessary to prepare UV LED epitaxial layer structures with high crystal quality.

At present, the growth of UV LED epitaxial layers generally first prepares the AlN (or AlGaN) buffer layer by MOCVD method or PVD method or a combination of the two methods, and then continues to epitaxially grow the subsequent epitaxial structure in MOCVD. Although the AlN (or AlGaN) buffer layer can be To a certain extent, the lattice mismatch between the substrate and the AlGaN epitaxial layer can be alleviated to meet the requirements of epitaxial growth. However, it is not enough for ultraviolet light emitting diodes (UV LEDs) with higher crystal quality requirements, and it is necessary to further improve the crystal quality of epitaxial growth. .

SUMMARY OF THE INVENTION

Based on this, the purpose of the present invention is to provide an LED epitaxial wafer, an epitaxial growth method and an LED chip, aiming at solving the problem of poor quality of epitaxially grown crystals in the existing ultraviolet light emitting diodes.

An LED epitaxial wafer according to an embodiment of the present invention includes a buffer layer, the buffer layer is composed of an Al/AlN/NH ₃ superlattice layer and an Al/AlN/H ₂ superlattice layer, and the Al/AlN/H 2 superlattice layer An AlN/H ₂ superlattice layer is deposited on the Al/AlN/NH ₃ superlattice layer;

Wherein, the Al/AlN/NH ₃ superlattice layer is a periodic structure formed by alternate growth of Al sublayer, AlN sublayer, and NH ₃ sublayer, and the Al/AlN/H ₂ superlattice layer It is a periodic structure formed by the Al sublayer, the AlN sublayer, and the _H2 sublayer cyclically alternately grown.

Preferably, the LED epitaxial wafer further comprises a sapphire substrate, an undoped AlGaN layer, an N-type doped AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type doped GaN layer and an AlGaN contact layer;

the buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multiple quantum well layer, the electron blocking layer, the P-type doped GaN layer, and the AlGaN contact layer Sequentially epitaxially grown on the sapphire substrate.

Preferably, the total thickness of the Al/AlN/NH ₃ superlattice layer is 50 nm to 100 nm, the thickness of the Al sublayer in a single cycle is 1 nm to 2 nm, and the thickness of the AlN sublayer in a single cycle is 5 nm to 10 nm , the total thickness of the Al/AlN/H2 superlattice layer is 100 nm to 200 nm, the thickness of the Al sublayer in a single cycle is 1 nm to 2 nm, the thickness of the AlN sublayer in a single cycle is 10 nm to 20 nm, and the thickness of the Al sublayer in a single cycle is 10 nm to 20 nm. The thickness of the doped AlGaN layer is 1 μm to 3 μm, the thickness of the N-type doped AlGaN layer is 1 μm to 3 μm, the thickness of the multiple quantum well layer is 50 nm to 288 nm, and the thickness of the electron blocking layer is 20 nm to 20 nm. 100 nm, the thickness of the P-type doped GaN layer is 30 nm to 200 nm, and the thickness of the AlGaN contact layer is 10 nm to 50 nm.

Preferably, the multiple quantum well layer is a periodic structure formed by alternate growth of AlGaN layers and GaN layers, wherein the GaN layer is a well layer, and the thickness of the GaN layer in a single period is 2 nm to 4 nm. The AlGaN layer is a barrier layer, and the thickness of the AlGaN layer in a single cycle is 8 nm˜20 nm.

An epitaxial growth method for an LED epitaxial wafer according to an embodiment of the present invention is used to prepare the above-mentioned LED epitaxial wafer, and the epitaxial growth method includes:

When growing the buffer layer, the Al/AlN/NH ₃ superlattice layer is formed by controlling the Al sublayer, the AlN sublayer and the _NH3 sublayer to alternately grow cyclically;

The Al sub-layer, the AlN sub-layer, and the H ₂ sub-layer are controlled to alternately grow on the Al/AlN/NH ₃ superlattice layer to form an Al/AlN/H ₂ superlattice layer.

Preferably, the epitaxial growth method further comprises:

providing a sapphire substrate required for growth;

The buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multiple quantum well layer, the electron blocking layer, the P-type doped GaN layer and the AlGaN contact layer are sequentially epitaxially grown on the sapphire substrate .

Preferably, the Al/AlN/NH ₃ superlattice layer has a growth temperature of 800°C to 900°C, a growth pressure of 30torr to 80torr, and a molar ratio of V/III ratio in a range of 2000 to 4000. In a single cycle, NH Layer ₃ is only annealed with NH ₃ , and the time is 5s to 10s, and the MO source is not used for growth.

Preferably, the growth temperature of the Al/AlN/H ₂ superlattice layer is 1050°C to 1200°C, the growth pressure is 30torr to 80torr, and the molar ratio of the V/III ratio is in the range of 50 to 500. In a single cycle The H ₂ layer is only annealed with H ₂ for 5s to 10s, and the MO source is not used for growth.

Preferably, the growth temperature of the undoped AlGaN layer is 1050°C-1200°C, the growth pressure is between 50torr and 100torr, and the Al composition is between 0.3-0.8.

An LED chip according to an embodiment of the present invention includes the above-mentioned LED epitaxial wafer.

Compared with the prior art: the buffer layer is composed of a low-temperature Al/AlN/ _NH3 superlattice layer with a high V/III ratio and a high-temperature Al/AlN/ _H2 superlattice layer with a low V/III ratio. The low-temperature Al/AlN/NH ₃ superlattice layer with high V/III ratio in the layer grows in a three-dimensional mode, which can well annihilate the dislocations generated by the lattice mismatch between the substrate and the epitaxial layer, and block defects from continuing to the epitaxial layer. extension, and then through NH ₃ annealing treatment, the epitaxy is more inclined to grow in 3D mode, further reducing dislocations, while the high temperature Al/AlN/H ₂ superlattice layer with low V/III ratio in the buffer layer grows in 2D mode By covering the above-mentioned three-dimensional Al/AlN superlattice layer, a relatively flat epitaxial layer can be obtained, and then by H ₂ annealing treatment, the surface of the epitaxial layer is smoother, and the crystal quality is further improved.

Description of drawings

FIG. 1 is a schematic structural diagram of an LED epitaxial wafer in Embodiment 1 of the present invention;

FIG. 2 is a flowchart of an epitaxial growth method of an LED epitaxial wafer in Embodiment 2 of the present invention.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the related drawings. Several embodiments of the invention are presented in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

Please refer to FIG. 1, which shows an LED epitaxial wafer in Embodiment 1 of the present invention, including a sapphire substrate 1, a buffer layer 2 epitaxially grown on the sapphire substrate 1 in sequence, and an undoped AlGaN layer 3, N-type Doped AlGaN layer 4 , multiple quantum well layer 5 , electron blocking layer 6 , P-type doped GaN layer 7 and AlGaN contact layer 8 .

In this embodiment, the buffer layer 2 is composed of an Al/AlN/NH ₃ superlattice layer 21 and an Al/AlN/H ₂ superlattice layer 22, and the Al/AlN/H ₂ superlattice layer 22 is deposited on the Al /AlN/NH ₃ superlattice layer 21, wherein, Al/AlN/NH ₃ superlattice layer 21 is a periodic structure formed by Al sublayer, AlN sublayer, _NH3 sublayer cyclically alternately grown, and Al The /AlN/H ₂ superlattice layer 22 is a periodic structure formed by alternately growing Al sublayers, AlN sublayers, and _H2 sublayers cyclically.

By way of example but not limitation, in some preferred embodiments of this embodiment, the total thickness of the Al/AlN/NH ₃ superlattice layer 21 is 50 nm to 100 nm, such as 60 nm, 70 nm, 80 nm, etc., and the Al sublayer in a single period The thickness is 1nm to 2nm, such as 1nm, 1.5nm, 2nm, etc. The thickness of the AlN sublayer in a single cycle is 5nm to 10nm, such as 6nm, 7nm, 8nm, etc. The total thickness of the Al/AlN/H ₂ superlattice layer is 22 It is 100nm to 200nm, such as 100nm, 120nm, 140nm, etc., the thickness of the Al sublayer in a single cycle is 1nm to 2nm, such as 1nm, 1.5nm, 2nm, etc., the thickness of the AlN sublayer in a single cycle is 10nm to 20nm, such as 10 nm, 12 nm, 14 nm, etc., the thickness of the undoped AlGaN layer 3 is 1 μm to 3 μm, such as 1 μm, 2 μm, 3 μm, etc., and the thickness of the N-type doped AlGaN layer 4 is 1 μm to 3 μm, such as 1 μm, 2 μm, 3 μm, etc., the thickness of the multiple quantum well layer 5 is 50 nm to 288 nm, such as 100 nm, 150 nm, 200 nm, etc., the thickness of the electron blocking layer 6 is 20 nm to 100 nm, such as 20 nm, 40 nm, 60 nm, etc., P-type doped GaN layer The thickness of 7 is 30 nm to 200 nm, such as 40 nm, 60 nm, 80 nm, etc., and the thickness of AlGaN contact layer 8 is 10 nm to 50 nm, such as 20 nm, 30 nm, 40 nm, etc. In the Al/AlN/NH ₃ superlattice layer 21 , the Al sub-layer, the AlN sub-layer, and the NH ₃ sub-layer are cyclically alternately grown in cycles of 3 to 10, for example, 5, that is, the Al/AlN/NH ₃ superlattice. A total of 5 layers are grown in the layer 21. Similarly, in the Al/AlN/H ₂ superlattice layer 22, the Al sub-layer, the AlN sub-layer and the H ₂ sub-layer are cyclically alternately grown in cycles of 3 to 10, for example, 5. That is, the Al/AlN/H ₂ superlattice layer 22 is grown in five layers in total.

Specifically, the multiple quantum well layer 5 is a periodic structure formed by alternate growth of AlGaN layers and GaN layers, wherein the GaN layer is a well layer, and the AlGaN layer is a barrier layer, which is an example but not a limitation. In an example, the thickness of the GaN layer in a single cycle is 2 nm to 4 nm, such as 2 nm, 3 nm, 4 nm, etc., and the thickness of the AlGaN layer in a single cycle is 8 nm to 20 nm, such as 10 nm, 12 nm, 14 nm, etc. In the multiple quantum well layer 5, the AlGaN layer and the GaN layer are alternately grown for 5 to 12 periods, for example, 8 periods, that is, 8 multiple quantum well layers are grown in total.

Embodiment 2

Please refer to FIG. 2 , which shows an epitaxial growth method of an LED epitaxial wafer proposed in the second embodiment of the present invention, which is used for preparing the LED epitaxial wafer in the above-mentioned first embodiment. The method specifically includes steps S201 to S209 , wherein :

Step S201, providing a sapphire substrate required for growth.

In step S202, a buffer layer is grown, and the growth thickness thereof is 150 nm˜300 nm.

In this embodiment, the buffer layer includes a low-temperature Al/AlN/NH ₃ superlattice layer with a high V/III ratio and a high-temperature Al/AlN/H ₂ superlattice with a low V/III ratio. /AlN/ _NH3 superlattice layer and Al/AlN/ _H2 superlattice are sequentially deposited on a sapphire substrate, wherein trimethylaluminum (TMAl), trimethylgallium or triethylgallium (TMGa or TEGa ) and ammonia were used as the precursors of group III and group V sources, respectively, silane and magnesium dimethylocene were used as the precursors of N-type dopants and P-type dopants, respectively, and nitrogen and hydrogen were used as carrier gases.

Specifically, the growth temperature of the Al/AlN/NH ₃ superlattice layer ranges from 800°C to 900°C, the growth pressure ranges from 30torr to 80torr, the molar ratio of the V/III ratio ranges from 2000 to 4000, and the NH ₃ flow rate is 3000sccm～6000sccm, Al flow rate is 100sccm～200sccm. When the Al sublayer is grown in a single cycle, only the Al source is used for growth, and the time is 5s to 15s, without NH ₃ ; when the AlN sublayer is grown in a single cycle, the Al source and NH ₃ are simultaneously grown for growth. The growth time is 1min-3min; when the NH ₃ sublayer is grown in a single cycle, only NH ₃ is introduced for annealing treatment, and the Al source is not used for growth, and the time is 5s-10s.

_In addition, the growth temperature of the Al/AlN/H superlattice layer ranges from 1050°C to 1200°C, the growth pressure ranges from 30torr to 80torr, the molar ratio of V/III ratio ranges from 50 to 500, and the _NH3 flow rate is 100sccm～500sccm, Al flow rate is 500sccm～1000sccm. When the Al sublayer is grown in a single cycle, only the Al source is used for growth, and the time is 5s to 15s, without NH ₃ ; when the AlN sublayer is grown in a single cycle, the Al source and NH ₃ are simultaneously grown for growth. The growth time is 1min-3min; when the H ₂ sublayer is grown in a single cycle, that is, only H ₂ is fed for annealing treatment, and the Al source is not fed for growth, and the time is 5s-10s.

It is understandable that the Al sublayer in the superlattice is set to wet the substrate or the grown epitaxial layer through the Al layer first, which is beneficial to improve the migration ability of the subsequent AlN sublayer, thereby obtaining an epitaxial layer with better crystal quality.

Step S203 , growing an undoped AlGaN layer with a growth thickness of 1 μm˜3 μm.

It should be noted that the growth temperature of the undoped AlGaN layer is 1050° C. to 1200° C., the growth pressure is 50 torr to 100 torr, and the Al composition is 0.3 to 0.8.

Step S204 , growing an N-type doped AlGaN layer with a growth thickness of 1 μm˜3 μm.

Specifically, the N ^- type doped ^AlGaN layer is doped with Si. .

Step S205, alternately growing the quantum well layer and the quantum barrier layer to obtain a multi-quantum well layer, the growth thickness of which is 50 nm-288 nm.

It should be noted that the multiple quantum well layer is composed of 5 to 12 cycles of GaN/AlGaN, wherein GaN is the well layer and AlGaN is the barrier layer, wherein the well layer is grown at a temperature of 900°C to 1000°C and a growth pressure of 50torr ～200torr; the growth temperature of the barrier layer is 1000℃～1100℃, the pressure is between 50torr and 100torr, and the Al composition is 0.1～0.5.

Step S206 , growing an electron blocking layer with a growth thickness of 20 nm˜100 nm.

Wherein, the growth temperature of the electron blocking layer is 1000°C to 1100°C, the growth pressure is 50torr to 100torr, and the Al composition is 0.1 to 0.5.

Step S207 , growing a P-type doped GaN layer with a growth thickness of 30 nm˜200 nm.

The P-type doped AlGaN layer is doped with Mg, the growth temperature is 950°C to 1050°C, the growth pressure is 50torr to 300torr, and the Mg doping concentration is 1019cm ³ to 1020cm ³ .

Step S208 , growing an AlGaN contact layer with a growth thickness of 10 nm˜50 nm.

Specifically, the growth temperature of the AlGaN contact layer is 1000°C to 1100°C, the growth pressure is 50torr to 100torr, and the Al composition is 0.0 to 0.3.

Step S209, annealing treatment.

In this embodiment, after the growth of the epitaxial structure is completed, the temperature of the reaction chamber is lowered, and the annealing treatment is performed in a nitrogen atmosphere. Finish.

To sum up, the LED epitaxial wafer and the epitaxial growth method thereof in the embodiments of the present invention are composed of a low-temperature Al/AlN/NH ₃ superlattice layer with a high V/III ratio and a high-temperature Al/AlN/H with a low V/III ratio ₂ The buffer layer composed of superlattice layers, the low-temperature Al/AlN/NH ₃ superlattice layer with high V/III ratio in the buffer layer grows in a three-dimensional mode, which can well annihilate the lattice mismatch between the substrate and the epitaxial layer. The generated dislocations and blocking defects continue to extend to the epitaxial layer, and then through NH ₃ annealing treatment, the epitaxy is more inclined to grow in a three-dimensional mode, further reducing dislocations, while the low V/III ratio of high temperature Al/AlN in the buffer layer The /H ₂ superlattice layer grows in a two-dimensional mode. By covering the above grown three-dimensional Al/AlN superlattice layer, a relatively flat epitaxial layer can be obtained, and then the surface of the epitaxial layer is smoother by H ₂ annealing treatment. , the crystal quality is further improved.

Embodiment 3

The third embodiment of the present invention provides an LED chip, including the LED epitaxial wafer in the first embodiment. The LED epitaxial wafer can be epitaxially grown by the epitaxial growth method of the LED epitaxial wafer in the second embodiment.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that, for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims (10)

1. The LED epitaxial wafer is characterized by comprising a buffer layerFrom Al/AlN/NH₃Superlattice layer and Al/AlN/H₂A superlattice layer, and the Al/AlN/H₂A superlattice layer deposited on the Al/AlN/NH₃A superlattice layer;

wherein the Al/AlN/NH₃The superlattice layer is composed of an Al sublayer, an AlN sublayer and NH₃A periodic structure formed by cyclic and alternate growth of sublayers, the Al/AlN/H₂The superlattice layer is composed of the Al sublayer, the AlN sublayer and H₂The sub-layers are cyclically and alternately grown to form a periodic structure.

2. The LED epitaxial wafer according to claim 1, further comprising a sapphire substrate, an undoped AlGaN layer, an N-type doped AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type doped GaN layer and an AlGaN contact layer;

the buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multi-quantum well layer, the electronic barrier layer, the P-type doped GaN layer and the AlGaN contact layer are sequentially epitaxially grown on the sapphire substrate.

3. LED epitaxial wafer according to claim 2, characterized in that the Al/AlN/NH₃The total thickness of the superlattice layer is 50 nm-100 nm, the thickness of the Al sublayer in a single period is 1 nm-2 nm, the thickness of the AlN sublayer in a single period is 5 nm-10 nm, and the Al/AlN/H₂The total thickness of the superlattice layer is 100 nm-200 nm, the thickness of the Al sublayer in a single period is 1 nm-2 nm, the thickness of the AlN sublayer in the single period is 10 nm-20 nm, the thickness of the undoped AlGaN layer is 1 mu m-3 mu m, the thickness of the N-type doped AlGaN layer is 1 mu m-3 mu m, the thickness of the multi-quantum well layer is 50 nm-288 nm, the thickness of the electron blocking layer is 20 nm-100 nm, the thickness of the P-type doped GaN layer is 30 nm-200 nm, and the thickness of the AlGaN contact layer is 10 nm-50 nm.

4. The LED epitaxial wafer according to claim 2, wherein the MQW layer is a periodic structure in which AlGaN layers and GaN layers are alternately grown, wherein the GaN layers are well layers, the thickness of the GaN layers in a single period is 2nm to 4nm, the AlGaN layers are barrier layers, and the thickness of the AlGaN layers in a single period is 8nm to 20 nm.

5. An epitaxial growth method of an LED epitaxial wafer, for preparing the LED epitaxial wafer of any one of claims 1 to 4, the epitaxial growth method comprising:

controlling Al sublayer, AlN sublayer and NH during buffer layer growth₃The sublayers cyclically and alternately grow to form Al/AlN/NH₃A superlattice layer;

controlling the Al sublayer, the AlN sublayer, H₂Sub-layers cyclically and alternately grow on the Al/AlN/NH₃Forming Al/AlN/H on the superlattice layer₂A superlattice layer.

6. The epitaxial growth method of an LED epitaxial wafer according to claim 5, further comprising:

providing a sapphire substrate required for growth;

and sequentially epitaxially growing the buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multi-quantum well layer, the electronic barrier layer, the P-type doped GaN layer and the AlGaN contact layer on the sapphire substrate.

7. The epitaxial growth method of LED epitaxial wafer according to claim 5, wherein the Al/AlN/NH₃The growth temperature of the superlattice layer is 800-900 ℃, the growth pressure is 30-80 torr, the molar ratio of the V/III ratio is 2000-4000, and NH is generated in a single period₃Layer of only NH₃Annealing for 5-10 s without MO source.

8. The epitaxial growth method of LED epitaxial wafer according to claim 5, wherein the Al/AlN/H₂The growth temperature of the superlattice layer is 1050-1200 ℃, the growth pressure is 30-80 torr, and the molar ratio range of the V/III ratio isBetween 50 and 500, H in a single period₂Layer is introduced with H only₂Annealing for 5-10 s without MO source.

9. The epitaxial growth method of LED epitaxial wafer according to claim 6, wherein the growth temperature of the undoped AlGaN layer is 1050 ℃ to 1200 ℃, the growth pressure is 50torr to 100torr, and the Al composition is 0.3 to 0.8.

10. An LED chip comprising the LED epitaxial wafer according to any one of claims 1 to 4.

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