KR20120018583A - Light emitting device - Google Patents

Abstract

PURPOSE: A light emitting device is provided to increase photonic efficiency by forming a first electrode and a second electrode and reflecting the light from a light emitting diode. CONSTITUTION: A first conductive semiconductor layer(110) is formed on a substrate(100). An active layer(120) is formed on the first conductive semiconductor layer. An interfacial layer(130) is formed on the active layer. A second conductive semiconductor layer(140) is formed on the interfacial layer. A first electrode(170) and a second electrode(180) are formed on the first conductive semiconductor layer and the second conductive semiconductor layer.

Description

[0001]

The embodiment relates to a light emitting device.

Light emitting devices such as light emitting diodes or laser diodes using semiconductors of Group 3-5 or 2-6 compound semiconductor materials of semiconductors have various colors such as red, green, blue and ultraviolet rays due to the development of thin film growth technology and device materials. It is possible to realize efficient white light by using fluorescent materials or combining colors, and it has low power consumption, semi-permanent life, fast response speed, safety and environmental friendliness compared to conventional light sources such as fluorescent and incandescent lamps. Has an advantage.

Therefore, a white light emitting device that can replace a fluorescent light bulb or an incandescent bulb that replaces a Cold Cathode Fluorescence Lamp (CCFL) constituting a backlight of a transmission module of an optical communication means and a liquid crystal display (LCD) display device. Applications are expanding to diode lighting devices, automotive headlights and traffic lights.

The embodiment is intended to improve the luminous efficiency of the light emitting device.

An embodiment includes a first conductivity type semiconductor layer; An active layer on the first conductivity type semiconductor layer; An interface layer on the active layer; And a second conductivity-type semiconductor layer on the interface layer, wherein the interface layer includes at least two barrier layers each having an energy band gap increased from the direction of the second conductivity-type semiconductor layer toward the active layer. Provided is a light emitting device comprising a base layer having a constant energy band gap between barrier layers and a composition of p-doped In _x Ga _{1 - x} N.

Here, the base layer may have a composition of In _x Ga _1-x N.

The base layer is p-doped and may have a thickness of at least 1 nanometer.

The at least one barrier layer may have a section in which the energy band gap is constant at the highest point of the energy band gap.

The energy band gap of the barrier layer may increase from the start point of the second conductive semiconductor layer direction and may decrease vertically at the end point of the active layer direction.

The interfacial layer includes a first barrier layer and a second barrier layer adjacent to each other with the base layer, wherein the first barrier layer has an energy bandgap increased from a starting point in the direction of the second conductive semiconductor layer. The energy band gap of the base layer may be vertically reduced at the end point of the active layer direction, and the energy band gap of the start point of the second barrier layer may be the same as the energy band gap of the base layer.

The pattern of the energy band gap of the first barrier layer and the second barrier layer may be the same.

The interface layer may have a composition of Al _x In _y Ga _1-xy N (where 0 ≦ x, y ≦ 1).

In addition, the composition of Al in the interface layer may be 30% or less.

In addition, the Al composition in the barrier layer may increase in the active layer direction.

The In composition in the barrier layer may decrease in the active layer direction.

The energy band gap of the base layer may be less than or equal to the energy band gap of the second conductive semiconductor layer.

The peak of the energy band gap of the barrier layer may be greater than the energy band gap of the quantum wall in the active layer.

The barrier layer may have a thickness of at least 2 nanometers, the energy band gap of the interfacial layer may be 0.8-6.2 eV, and the in-plane lattice constant may be 3.10-3.54 kW (Angstrom).

The interfacial layer includes a first barrier layer and a second barrier layer adjacent to each other on the base layer, and a maximum value of an energy band gap of the first barrier layer adjacent to the second conductive semiconductor layer is determined by the active layer. It may be greater than the highest value of the energy band gap of the adjacent second barrier layer.

The interface layer may include Al, and an Al composition of the first barrier layer may be greater than an Al composition of the second barrier layer.

In addition, the Al composition of the barrier layer closest to the active layer may be 10% or less.

In addition, the at least one barrier layer may have a predetermined thickness at the highest point of the energy band gap.

The light emitting device according to the embodiment improves luminous efficiency.

1 is a cross-sectional view of a light emitting device according to an embodiment;
2 is a view showing a first embodiment of an energy band gap of a light emitting device according to the embodiment;
3 is a view showing a second embodiment of the energy band gap of the light emitting device according to the embodiment;
4 is a view showing a third embodiment of the energy band gap of the light emitting device according to the embodiment;
5 is a view showing a fourth embodiment of the energy band gap of the light emitting device according to the embodiment;
6 is a diagram showing energy band gap and lattice constant of an interfacial layer,
7 to 9 are views showing other embodiments of the energy band gap of the light emitting device,
10 is a view showing an embodiment of a light emitting device package.

Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings.

In the description of the embodiments, it is to be understood that each layer (film), region, pattern or structure is formed "on" or "under" a substrate, each layer The terms " on "and " under " encompass both being formed" directly "or" indirectly " In addition, the criteria for the top or bottom of each layer will be described with reference to the drawings.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. In addition, the size of each component does not necessarily reflect the actual size.

1 is a cross-sectional view of a light emitting device according to an embodiment, FIG. 2 is a view showing a first embodiment of an energy band gap of a light emitting device according to the embodiment, and FIG. 6 shows an energy band gap and a lattice constant of an interface layer. Drawing. Hereinafter, a light emitting device according to an embodiment will be described with reference to FIGS. 1, 2, and 6.

As illustrated, in the light emitting device according to the embodiment, the first conductive semiconductor layer 110, the active layer 120, the interface layer 130, and the second conductive semiconductor layer 140 are stacked on the substrate 100. .

The substrate 100 may be formed of a light-transmissive material, for example, sapphire (Al ₂ 0 ₃ ), GaN, SiC, ZnO, Si, GaP, InP, Ga ₂ 0 ₃ , and GaAs.

In addition, a buffer layer (not shown) may be provided between the nitride semiconductor and the substrate 100 to mitigate the difference in lattice mismatch and thermal expansion coefficient of the material. The buffer layer (not shown) may be a low temperature growth GaN layer or an AlN layer, or the like. Can be used.

The first conductive semiconductor layer 110 may be formed of only the first conductive semiconductor layer, or may further include an undoped semiconductor layer under the first conductive semiconductor layer, but is not limited thereto.

The first conductivity-type semiconductor layer 110 may include, for example, an n-type semiconductor layer, wherein the n-type semiconductor layer is In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y 1, 0 ≦ x + y ≦ 1), for example, GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, and the like, and may be selected from Si, Ge, Sn, Se, Te, and the like. An n-type dopant may be doped.

The undoped semiconductor layer is a layer in which the first conductivity type semiconductor layer is formed to improve crystallinity, except that the n-type dopant is not doped and thus has lower electrical conductivity than that of the first conductivity type semiconductor layer. It may be the same as the first conductive semiconductor layer.

An active layer 120 may be formed on the first conductivity type semiconductor layer 110. The active layer 120 is formed of, for example, a semiconductor material having a compositional formula of In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). It may include at least one of a quantum wire structure, a quantum dot structure, a single quantum well structure, or a multi quantum well structure (MQW).

The active layer 120 may generate light by energy generated in a recombination process of electrons and holes provided from the first conductive semiconductor layer 110 and the second conductive semiconductor layer 140. Can be.

In addition, an interface layer 130 may be formed on the active layer 120. The interfacial layer 130 is provided with a barrier layer at least twice, and a base layer is provided between each barrier layer. In FIG. 2, three barrier layers are provided in the interface layer 130, and two base layers are provided between each barrier layer.

Here, the base layer is provided between each barrier layer, the energy band gap is a constant section, and the section having the lowest energy band gap in the interface layer 130. In addition, the base layer may have a composition of In _x Ga _{1 - x} N, where x has a value greater than 0 and less than 1, and may be p-doped with magnesium (Mg) or the like. Since the base layer is for smooth movement of the holes injected from the second conductive semiconductor layer 126 toward the active layer 120, a section having a constant energy band gap between each barrier layer is 1 nanometer. The base layer may be provided with a small amount of Al in the manufacturing process.

In addition, the energy band gap of each barrier layer is provided to increase in the direction of the active layer 120 from the second conductivity type semiconductor layer 140. In addition, the energy band gap of the barrier layer increases from the start point in the direction of the second conductivity type semiconductor layer 140 and decreases perpendicularly from the end point in the direction of the active layer to reach the base layer.

That is, in FIG. 2, the first barrier layer and the second barrier layer which are adjacent to each other with the base layer in the interface layer 130 are provided, and the energy band gap of the first barrier layer is the second conductive semiconductor layer. It increases from the starting point in the (140) direction and decreases perpendicularly to the energy band gap of the base layer at the end point in the active layer 120 direction. The energy band gap of the starting point of the second barrier layer is provided in the same manner as the energy band gap of the base layer.

In FIG. 2, the energy band gaps of the first barrier layer, the second barrier layer, and the third barrier layer are provided in the same pattern so that holes injected from the second conductive semiconductor layer may be constantly injected into the active layer. have.

The interfacial layer, which can be moved in an inclined structure with respect to a hole and can be difficult to move due to a vertical structure with respect to an electron, is provided with a thickness of 2 nanometers or more and has a thickness of Al _x In _y Ga _{1 -x- y} N. (Where 0 ≦ x, y ≦ 1).

If the thickness of each barrier layer is too thin, due to the tunneling effect or the like, it may not be sufficient to serve as a barrier for electrons. In addition, if the thickness of each barrier layer is too thick, it may act as an obstacle to the passage of holes, so that it may be provided with a thickness of 10 nanometers or less.

In order to have the above-described energy band gap, the Al composition in each barrier layer increases in the direction of the active layer but has a composition within 30%, and the In composition decreases in the direction of the active layer.

The energy band gap of the first barrier layer may be provided to be equal to or less than the energy band gap of the second conductivity type semiconductor layer 140 at the starting point of the second conductivity type semiconductor layer direction 140. If the energy band gap of the first barrier layer is greater than the energy band gap of the second conductivity type semiconductor layer 140 at the starting point of the second conductivity type semiconductor layer direction 140, the hole band gap is increased. Can act as a barrier.

In addition, the energy band gap of the end point of the barrier layer may be larger than the energy band gap of the quantum wall in the active layer 120. If the energy band gap of the barrier layer is less than or equal to the energy band gap of the quantum walls in the active layer 120, the barrier layer may not be sufficiently acted on the electrons injected from the first conductivity-type semiconductor layer 110.

The second conductivity type semiconductor layer 140 may be formed on the interface layer 130. The second conductivity-type semiconductor layer 140 may be implemented, for example, as a p-type semiconductor layer, wherein the p-type semiconductor layer is In _x Al _y Ga _{1 -x- y} N (0 ≦ x ≦ 1, 0 ≦ y≤1, 0≤x + y≤1), for example, GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, and the like, and may be selected from Mg, Zn, Ca, Sr, Ba P-type dopants may be doped.

Here, unlike the above, the first conductivity-type semiconductor layer 110 may include a p-type semiconductor layer, and the second conductivity-type semiconductor layer 140 may include an n-type semiconductor layer. In addition, a third conductive semiconductor layer (not shown) including an n-type or p-type semiconductor layer may be formed on the first conductive semiconductor layer 110. Accordingly, the light emitting device according to the present embodiment It may have at least one of np, pn, npn, pnp junction structure.

In addition, the doping concentrations of the conductive dopants in the first conductive semiconductor layer 110 and the second conductive semiconductor layer 140 may be uniformly or non-uniformly formed. That is, the structure of the plurality of semiconductor layers may be formed in various ways, but is not limited thereto.

The first electrode 170 and the second electrode 180 are provided on the first conductive semiconductor layer 110 and the second conductive semiconductor layer 140, respectively. Here, the first electrode 170 and the second electrode 180 are at least one of aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), copper (Cu), and gold (Au), respectively. It may be formed in a single layer or a multi-layer structure, including.

The structure of the horizontal light emitting device has been described above, but in the vertical light emitting device, an interface layer including a barrier layer may exist between the second conductive semiconductor layer and the active layer.

6 is a graph showing energy band gaps and lattice constants of an interfacial layer. The bandgap Eg of gallium nitride (GaN) is 3.4 eV, and the in-plane lattice constant is 3.185 Å (Angstrom). As shown in FIG. 5, when the composition of the interfacial layer is GaN, the composition of the interfacial layer may be selected within the hatched region, and the energy band gap of the interfacial layer may be 0.8-6.2 eV, and the In-plane The lattice constant may be 3.10 to 3.54 kW (Angstrom).

In the first embodiment of the above-described light emitting device, a large amount of forward holes injected in the direction of the active layer from the hole injection layer first encounter the barrier layer. Since one side of the barrier layer adjacent to the hole injection layer has a small energy band gap and the energy band gap gradually increases in the direction of the active layer, a large amount of holes injected when forward voltage is applied is easily moved along the slope of the energy band gap of the barrier layer toward the active layer. Is injected.

In addition, there is a p-doped base layer between each barrier layer. Since the base layer has better mobility of electrons or charges than GaN, even if the concentration of holes increases, the mobility increases. Holes with increased mobility can move to quantum wells far from the hole injection layer, and can be evenly distributed throughout the active layer.

Therefore, the increased mobility of the holes can move from the quantum wells adjacent to the hole injection layer to the quantum wells farther from each other, so that the holes are evenly distributed throughout the active layer.

That is, the holes injected when the forward voltage is applied are easily injected toward the active layer along the energy band gap slope of the interface layer including the plurality of barriers, and the surplus electrons that do not participate in the light emission in the quantum wells in the active layer are transferred to the interface. Forward energy leakage is effectively blocked because the energy band gap of the layer encounters a relatively large energy barrier.

3 is a view showing a second embodiment of the energy band gap of the light emitting device according to the embodiment. In the embodiment shown in FIG. 3, the barrier layer has a section in which the energy band gap is constant at the highest point of the energy band gap. That is, since the energy band gap of the barrier layer can act as a barrier even for holes, the peak of the energy band gap is lowered.

In the present embodiment, the vertical energy band gap of the barrier layer acts as a barrier to electrons injected from the first conductivity type semiconductor layer, but the mobility may increase due to a decrease in the peak of the energy band gap for holes.

4 is a view showing a third embodiment of the energy band gap of the light emitting device according to the embodiment. Similar to the first embodiment in this embodiment, but the energy band gap of each barrier layer is not the same, and the highest point of the energy band gap of the barrier layer close to the second conductivity type semiconductor layer is larger.

In other words, the highest point of the energy band gap of the first barrier layer is the highest among the three illustrated barrier layers, and the highest point of the energy band gap of the third barrier layer adjacent to the active layer is the lowest. Such a configuration is possible with the Al composition of the first barrier layer being larger than the Al composition of the second barrier layer with respect to the composition of Al contained in the interface layer. In addition, the Al composition of the barrier layer closest to the active layer may be 10% or less. In addition, the base layer having the composition of p-doped In _x Ga _{1 - x} N and the like is the same as in the first embodiment.

In this embodiment, the Al composition of the third barrier layer in contact with the active layer is relatively low, so that a defect due to the lattice constant difference between the two layers may not occur at the interface between the active layer and the third barrier layer.

In addition, the composition of Al is increased toward the second barrier layer and the third barrier layer to prevent electrons from leaking into the hole injection layer. In the case of a hole, a plurality of barrier layers are passed from the hole injection layer toward the active layer, but since the Al composition of each barrier layer gradually decreases, the hole injection efficiency is increased, and even hole distribution is possible in the active layer direction. Accordingly, even light emission of the entire active layer can be achieved and light emission efficiency and reliability of the light emitting device can be improved.

5 is a view showing a fourth embodiment of the energy band gap of the light emitting device according to the embodiment.

This embodiment is similar to the third embodiment described above, but has a section in which the energy band gap of the barrier layer is constant at the highest point. That is, the base layer has a low energy band gap section between each barrier layer, or a constant energy band gap at the highest point of the energy band gap within each barrier layer, so that the section has a constant thickness on the interface layer.

In the present embodiment, the vertical energy band gap of the barrier layer acts as a barrier to electrons injected from the first conductivity type semiconductor layer, but the mobility may increase due to a decrease in the peak of the energy band gap for holes.

7 to 9 are diagrams showing other embodiments of the energy band gap of the light emitting device.

In the embodiment shown in FIG. 7, the p-AlGaN single layer may serve as an electron blocking layer between the active layer and the hole injection layer. However, if the p-AlGaN electron blocking layer is thin, the electrons can be passed in the direction of the hole injection layer through quantum mechanical tunneling, so that the electron blocking layer may be sufficiently thick so that tunneling of electrons does not occur. In this case, the thick P-AlGaN electron blocking layer may act as an energy barrier to holes injected from the hole injection layer into the active layer.

In the embodiment shown in FIG. 8, a thin p-AlGaN layer and a thin P-GaN layer are alternately stacked to form a superlattice layer, wherein the P-AlGaN layer is thin so that holes injected from the hole injection layer to the active layer are quantum mechanically. Tunneling can pass through the superlattice layer, improving the low hole injection efficiency problem of thick P-AlGaN electron blocking layers. However, electrons may also pass through the thin P-AlGaN layer through quantum mechanical tunneling, and thus may not effectively block the leakage of electrons from the active layer toward the hole injection layer.

And, in the embodiment shown in Figure 9 is provided with an interfacial layer between the hole injection layer and the active layer, the interface layer is composed of at least one barrier layer, the energy band gap of each barrier layer increases in the direction of the hole injection layer It is provided by. Therefore, (p-type) A large amount of forward holes injected from the hole injection layer toward the active layer first encounter a barrier layer (layer A). Since one side of the barrier layer adjacent to the hole injection layer has a small energy band gap and the energy band gap gradually increases in the direction of the active layer, holes injected when forward voltage is applied are injected along the energy band gap slope of the barrier layer toward the active layer.

In addition, electrons in the quantum well in the active layer encounter one energy barrier of the barrier layer having a relatively large energy band gap adjacent to the active layer, so that forward electron leakage toward the hole injection layer is effectively blocked under the forward voltage.

However, although the hole injection efficiency is improved compared to the embodiments shown in FIGS. 7 and 8, due to the low mobility of the holes, the holes are mainly distributed in the quantum well layer close to the hole injection layer, and the further away from the hole injection layer, The concentration of can be lowered.

In addition, due to the lattice constant difference between the quantum well layer or the quantum barrier layer and the barrier layer (A layer) in the interface layer, crystallographic defects (V pit) may occur at the interface.

10 is a cross-sectional view of an embodiment of a light emitting device package. Hereinafter, an embodiment of the light emitting device package will be described with reference to FIG. 10.

As illustrated, the light emitting device package according to the embodiment may include a package body 320, a first electrode layer 331 and a second electrode layer 332 installed on the package body 320, and the package body 320. A light emitting device 300 according to the above-described embodiments, which is installed and electrically connected to the first electrode layer 331 and the second electrode layer 332, and a filler 340 surrounding the light emitting device 00. do.

The package body 320 may include a silicon material, a synthetic resin material, or a metal material. An inclined surface may be formed around the light emitting device 300 to increase light extraction efficiency.

The first electrode layer 311 and the second electrode layer 312 are electrically separated from each other, and provide power to the light emitting device 300. In addition, the first electrode layer 311 and the second electrode layer 312 can increase the light efficiency by reflecting the light generated from the light emitting device 300, the outside of the heat generated from the light emitting device 300 May also act as a drain.

The light emitting device 300 may be installed on the package body 320 or on the first electrode layer 311 or the second electrode layer 312.

The light emitting device 300 may be electrically connected to the first electrode layer 311 and the second electrode layer 312 by any one of a wire method, a flip chip method, or a die bonding method.

The filler 340 may surround and protect the light emitting device 300. In addition, the filler 340 may include a phosphor to change the wavelength of light emitted from the light emitting device 300.

The light emitting device package may mount at least one of the light emitting devices of the above-described embodiments as one or more, but is not limited thereto.

A plurality of light emitting device packages according to the embodiment may be arranged on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, or the like, which is an optical member, may be disposed on an optical path of the light emitting device package. The light emitting device package, the substrate, and the optical member may function as a light unit. Another embodiment may be implemented as a display device, an indicator device, or a lighting system including the semiconductor light emitting device or the light emitting device package described in the above embodiments, for example, the lighting system may include a lamp and a street lamp. .

Features, structures, effects, and the like described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

In addition, the above description has been made with reference to the embodiment, which is merely an example, and is not intended to limit the present invention. Those skilled in the art to which the present invention pertains will be illustrated as above without departing from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

100 substrate 110 first conductive semiconductor layer
120: active layer 130: interface layer
140: second conductive semiconductor layer 170: first electrode
180: second electrode

Claims (19)

A first conductive semiconductor layer;
An active layer on the first conductivity type semiconductor layer;
An interface layer on the active layer; And
A second conductivity type semiconductor layer on the interface layer,
The interfacial layer is provided with at least two barrier layers whose energy band gap increases from the direction of the second conductivity type semiconductor layer toward the active layer, and the energy band gap is constant and p-doped In _x between the respective barrier layers. A light emitting device provided with a base layer having a composition of Ga _{1 - x} N. The method of claim 1,
The base layer has a thickness of at least 1 nanometer. The method of claim 1,
The at least one barrier layer is a light emitting device having a constant interval of the energy band gap at the highest point of the energy band gap. The method of claim 1,
The energy band gap of the barrier layer increases from the start point in the direction of the second conductivity type semiconductor layer and decreases vertically at the end point in the direction of the active layer. The method of claim 1,
The interfacial layer includes a first barrier layer and a second barrier layer adjacent to each other with the base layer, wherein the first barrier layer has an energy bandgap increased from a starting point in the direction of the second conductive type semiconductor layer and thus in the active layer direction. And a vertical decrease to the energy band gap of the base layer at an end point of the base layer, wherein the energy band gap of the start point of the second barrier layer is the same as the energy band gap of the base layer. The method of claim 5, wherein
The light emitting device of the energy band gap pattern of the first barrier layer and the second barrier layer is the same. The method of claim 1,
A light emitting device having a composition of the interface _{layer, Al x In y Ga 1 -x-} y N ( where, 0≤x, y≤1). The method of claim 8,
A light emitting device in which the composition of Al in the interface layer is 30% or less. The method of claim 8,
The Al composition in the barrier layer increases in the direction of the active layer. The method of claim 7, wherein
The In composition in the barrier layer is reduced in the direction of the active layer. The method of claim 1,
The energy band gap of the base layer is less than the energy band gap of the second conductive semiconductor layer. The method of claim 1,
The energy band gap of the barrier layer is larger than the energy band gap of the quantum wall in the active layer. The method of claim 1,
The barrier layer has a thickness of at least 2 nanometers. The method of claim 1,
The energy band gap of the interface layer is a light emitting device of 0.8 ~ 6.2 eV. The method of claim 1,
In-plane lattice constant of the interface layer is a light emitting device of 3.10 ~ 3.54 Å (Angstrom). The method of claim 1,
The interfacial layer includes a first barrier layer and a second barrier layer adjacent to each other with the base layer, wherein a maximum value of an energy band gap of the first barrier layer adjacent to the second conductivity type semiconductor layer is determined by the first layer adjacent to the active layer. 2 A light emitting device having a value larger than the maximum value of the energy band gap of the barrier layer. 17. The method of claim 16,
The interfacial layer includes Al, and the Al composition of the first barrier layer is larger than the Al composition of the second barrier layer. 17. The method of claim 16,
The Al composition of the barrier layer closest to the active layer is 10% or less. 17. The method of claim 16,
The at least one barrier layer has a predetermined thickness at the highest point of the energy band gap.

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