KR101106629B1 - Light emitting diode containing metal/graphene transparent electrode and manufacturing method thereof - Google Patents

Abstract

PURPOSE: An emitting device which includes a metal/graphene transparent electrode and a manufacturing method thereof are provided to improve luminous efficiency by forming high permeability in an ultraviolet range using the metal/graphene transparent electrode as a transparent electrode material. CONSTITUTION: A buffer layer(120) is formed on a first substrate(101). A light emitting structure(S) is formed on the buffer layer. The light emitting structure comprises a first electrical conduction semiconductor layer(102), an active layer(103), and a second electrical conduction semiconductor layer(104). A metal/graphene transparent electrode(107) is formed on the second electrical conduction semiconductor layer. A bonding pad(108) is formed on the metal/graphene transparent electrode. A first electrode is formed on the first electrical conduction semiconductor layer.

Description

Light emitting device including metal / graphene transparent electrode and manufacturing method thereof {Light Emitting Diode containing Metal / Graphene Transparent Electrode and Manufacturing Method}

The present invention relates to a light emitting device including a metal / graphene transparent electrode and a manufacturing method thereof, and more particularly, to a light emitting device having a high transmittance not only in the visible light region but also in the ultraviolet region and having improved electrical properties. It is about.

Light Emitting Device (LED) is a device using a phenomenon in which electrons and holes combine to emit light when a current flows through a diode made of gallium nitride (GaN) -based compound semiconductor. It is getting great attention. Since the light emitting device transmits light to form an image or generates electric power, a transparent electrode capable of transmitting light is used as an essential component.

Currently, indium tin oxide (ITO) is most commonly used as a transparent electrode. The ITO substrate has the advantage of being very transparent in the visible light range, but there is a problem in that the economical efficiency in terms of price competitiveness due to the increase in the consumption of indium increases the price.

Recently, research on a transparent electrode using graphene as a transparent electrode to replace the ITO transparent electrode has been made at various angles. Graphene has a very transparent property not only in the visible region but also in the ultraviolet region, and unlike ITO, it is possible to realize an electrode with a very thin thickness and to solve the heat dissipation problem which is the biggest problem in the light emitting device. Can be solved.

In order to form the graphene layer as a transparent electrode, methods such as a scotch tape method, a redox reaction, a chemical vapor deposition (CVD) method, and vacuum annealing of SiC have been applied, but the process is very complicated.

Therefore, the present inventors use a transparent electrode material of the light emitting device to replace the conventional ITO substrate, instead of the conventional ITO substrate, by using a metal / graphene transparent electrode, and thus have high transmittance in visible and ultraviolet rays, and have high heat emission capability and electrical characteristics. It has been found that an improved light emitting device can be manufactured and the present invention has been completed.

In addition, another object of the present invention is to provide a light emitting device manufacturing method capable of forming a large area of the metal / graphene transparent electrode while simplifying the process.

In order to achieve the above object, the present invention provides a light emitting structure including a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer; A metal / graphene transparent electrode formed on the second conductive semiconductor layer; And a first electrode formed on the first conductive semiconductor layer.

According to an embodiment of the light emitting device according to the present invention, the metal / graphene transparent electrode may have a structure in which a graphene layer is formed on a metal layer.

According to an embodiment of the light emitting device according to the present invention, the metal layer may be made of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), and aluminum (Al).

According to an embodiment of the light emitting device according to the present invention, the thickness of the metal layer may be 1 nm to 5 nm.

According to an embodiment of the light emitting device according to the present invention, the thickness of the graphene layer may be 0.1 nm to 10 nm.

According to an embodiment of the light emitting device according to the present invention, the light emitting structure may be formed on a first substrate.

According to one embodiment of the light emitting device according to the present invention, a reflective layer, an adhesive layer and a second substrate may be further included between the second conductive semiconductor layer and the metal / graphene electrode.

According to another aspect of the invention, (a) forming a light emitting structure comprising a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on the first substrate; (b) forming a metal layer on the second conductivity type semiconductor layer; (c) forming a graphene layer on the metal layer; And (d) forming a first electrode on the first conductivity type semiconductor layer.

According to an embodiment of the method of manufacturing a light emitting device according to the present invention, the method may further include exposing the first conductive semiconductor layer by etching a portion of the light emitting structure between the steps (a) and (b). Can be.

According to one embodiment of the method of manufacturing a light emitting device according to the present invention, between the steps (a) and (b), forming a reflective layer on the second conductive semiconductor layer; Forming an adhesive layer on the reflective layer; Forming a second substrate on the adhesive layer; And removing the first substrate.

According to an embodiment of the method of manufacturing a light emitting device according to the present invention, the step (b) is one method selected from the group consisting of e-beam evaporation, thermal evaporation, and sputtering. It can be performed as.

According to one embodiment of the method of manufacturing a light emitting device according to the present invention, step (c) may be performed by a chemical vapor deposition (CVD) method.

According to another aspect of the present invention, there is provided a lighting device having the light emitting element.

According to another aspect of the present invention, a display device having the light emitting device is provided.

The light emitting device according to the present invention can have high transmittance even in the ultraviolet region by using a metal / graphene transparent electrode as the transparent electrode material, thereby improving luminous efficiency and facilitating heat dissipation of the device by facilitating heat dissipation generated in the device. It can be effective.

In addition, the light emitting device manufacturing method according to the present invention can simplify the process and form a metal / graphene transparent electrode in a large area.

1 is a cross-sectional view of a horizontal light emitting device according to the present invention.
2 is a cross-sectional view of a vertical light emitting device according to the present invention.
3 is an optical micrograph before applying a bias to a metal / graphene transparent electrode according to the present invention.
4 is an optical micrograph after applying a bias to the metal / graphene transparent electrode according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to be limited to the particular embodiment of the present invention, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

According to the present invention, there is provided a light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; A metal / graphene transparent electrode formed on the second conductive semiconductor layer; And a first electrode formed on the first conductive semiconductor layer. The light emitting device according to an embodiment of the present invention may be a horizontal light emitting device or a vertical light emitting device, but is not limited thereto.

1 is a cross-sectional view of a horizontal light emitting device according to an embodiment of the present invention. The horizontal light emitting device according to the present invention includes a first substrate 101, a buffer layer 120, a first conductive semiconductor layer 102, an active layer 103, a second conductive semiconductor layer 104, and a first electrode ( 105), a metal / graphene electrode 107 and a bonding pad 108. A structure of a horizontal light emitting device according to an embodiment of the present invention will be described below with reference to FIG. 1.

The first conductivity type semiconductor layer 102 is positioned on the first substrate 101. The first substrate 101 may be a GaN-based substrate as a homogeneous substrate, and may be a sapphire substrate, a SiC substrate, and a spinel substrate as a heterogeneous substrate, and any substrate capable of growing a nitride semiconductor layer may be used. . In this case, the gap between the first substrate 101 and the first conductivity-type semiconductor layer 102 between the first substrate 101 and the first conductivity-type semiconductor layer 102 to overcome the difference in the lattice constant and thermal expansion coefficient between the first substrate 101 and the first conductivity-type semiconductor layer 102 A buffer layer 120 may be included, and the buffer layer 120 may be GaN or AlN. In the first conductive semiconductor layer 102, at least a region where the first electrode 105 is formed is doped with an impurity and is n-type GaN.

A second conductive semiconductor layer 104 is positioned on the first conductive semiconductor layer 102, and an active layer 103 is disposed between the first conductive semiconductor layer 102 and the second conductive semiconductor layer 104. ). The active layer 103 is a layer that generates photons through recombination of electrons and holes, and may have a multi-quantum well structure in which at least one well layer and at least one barrier layer are alternately stacked, and Al _x In _y Ga _{1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) layer. The second conductive semiconductor layer 104 is GaN doped with p-type impurities.

A portion of the light emitting structure S including the first conductive semiconductor layer 102, the active layer 103, and the second conductive semiconductor layer 104 is etched to form a vertical sidewall on which a portion of the first conductive semiconductor layer is exposed. Equipped step is formed. The first electrode 105 is formed on the first conductivity type semiconductor layer 102 at the bottom of the step. The first electrode 105 is not particularly limited, and one selected from the group consisting of Cr / Au, Ni / Au, Ti / Au, and Ti / Al / Ni / Au may be used.

The second electrode 107 is formed on the second conductive semiconductor layer 104, and the second electrode 107 is provided so that the current is well supplied to the entire second conductive semiconductor layer. As the second electrode 107, a metal / graphene transparent electrode 107 is used. The metal / graphene transparent electrode 107 has a structure in which a graphene layer is formed on a metal layer. The metal layer of the metal / graphene transparent electrode 107 may be formed of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), and aluminum (Al). According to an example it may be nickel (Ni). Light is emitted through the metal / graphene transparent electrode 107 which is the second electrode 107. A bonding pad 108 for external connection may be formed on the metal / graphene transparent electrode 107. The bonding pads 108 are not particularly limited, and Cr / Au Or Ni / Au may be used.

2 is a cross-sectional view of a vertical light emitting device according to an embodiment of the present invention. As shown in FIG. 1, the vertical light emitting device according to the present invention includes a bonding pad 108, a metal / graphene electrode 107, a second substrate 203, an adhesive layer 202, a reflective layer 201, and a second The conductive semiconductor layer 104, the active layer 103, the first conductive semiconductor layer 102, and the first electrode 105 are formed. A structure of a vertical light emitting device according to an embodiment of the present invention will be described below with reference to FIG. 2.

A second conductive semiconductor layer 104 is positioned on the first conductive semiconductor layer 102, and an active layer 103 is disposed between the first conductive semiconductor layer 102 and the second conductive semiconductor layer 104. It includes. The active layer 103 is a layer that generates photons through recombination of electrons and holes, and may have a multi-quantum well structure in which at least one well layer and at least one barrier layer are alternately stacked, and Al _x In _y Ga _{1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) layer. The second conductive semiconductor layer 104 is GaN doped with p-type impurities.

The reflective layer 201, the adhesive layer 202, and the second substrate 203 are sequentially formed on the second conductive semiconductor layer 104. The reflective layer 201 effectively reflects light generated from the active layer and may be aluminum (Al), silver (Ag), or an alloy thereof. The adhesive layer 202 may be formed using nickel (Ni) or gold (Au), but the reflective layer 201 may function as an adhesive layer.

The second substrate 203 may be made of a metal, a metal alloy, or a conductive semiconductor material having excellent electrical conductivity to efficiently inject holes, and include copper (Cu), copper alloy (Cu Alloy), silicon (Si), It may be one selected from the group consisting of molybdenum (Mo) and silicon germanium (SiGe), but is not limited thereto.

A second electrode 107 is formed on the second substrate 203, and the second electrode 107 is provided to supply a good current to the entire second conductive semiconductor layer. As the electrode 107, a metal / graphene transparent electrode 107 is used. The metal / graphene transparent electrode 107 has a structure in which a graphene layer is formed on a metal layer. The metal layer of the metal / graphene transparent electrode 107 may be formed of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), and aluminum (Al). According to an example it may be nickel (Ni). Light is emitted through the metal / graphene transparent electrode 107 which is the second electrode 107.

The first electrode 105 is formed on the first conductive semiconductor layer 102. The first electrode 105 is not particularly limited, and one selected from the group consisting of Cr / Au, Ni / Au, Ti / Au, and Ti / Al / Ni / Au may be used. In addition, a bonding pad 108 for external connection may be formed on the metal / graphene transparent electrode 107. The bonding pads 108 are not particularly limited, and Cr / Au Or Ni / Au may be used.

In the metal / graphene transparent electrode 107 of the horizontal light emitting device and the vertical light emitting device according to an embodiment of the present invention, the thickness of the metal layer is 1 nm to 5 nm, and the thickness of the graphene layer 107 is 0.1 nm. To 10 nm. When the thickness of the metal layer is less than 1 nm, there is a problem that the metal layer may be broken, and when it exceeds 5 nm, there may be a problem of blocking light due to a decrease in transparency. In addition, the thinner the thickness of the graphene layer is, the better it is, and if it exceeds 10 nm, it is difficult to call it graphene, and there is a problem in that the effect as a transparent electrode is reduced by decreasing transparency.

As described above, as the transparent electrode material according to the present invention, the metal / graphene transparent electrode generates light from the front surface of the transparent electrode as well as the edge, so that the light efficiency can be seen in terms of light efficiency. Because of the transparency, the amount of light lost is small, which is competitive in terms of cost.

In addition, by using an ohmic metal of a GaN-based material as the metal of the metal / graphene transparent electrode, the electrical characteristics can be improved, and the graphene of the metal / graphene transparent electrode has a very high thermal conductivity. By dissipating the heat generated at, the temperature of the device can be reduced. As a result, the metal / graphene transparent electrode as described above can further increase the light efficiency of the light emitting device, and can prevent the shortening of the life of the light emitting device, thereby increasing its life.

The light emitting device including the metal / graphene transparent electrode according to the present invention may be utilized in an illumination device or a display.

According to another aspect of the invention (a) forming a light emitting structure comprising a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on the first substrate; (b) forming a metal layer on the second conductivity type semiconductor layer; (c) forming a graphene layer on the metal layer; And (d) forming a first electrode on the first conductivity type semiconductor layer. The light emitting device manufacturing method according to an embodiment of the present invention may be a horizontal light emitting device manufacturing method or a vertical light emitting device manufacturing method, but is not limited thereto.

A method of manufacturing a horizontal light emitting device according to an embodiment of the present invention will be described with reference to FIG. 1. The buffer layer 120 is formed on the first substrate 101. Thereafter, the light emitting structure S including the first conductive semiconductor layer 102, the active layer 103, and the second conductive semiconductor layer 104 is formed on the buffer layer 120, and then the light emitting structure S is formed. By etching, a portion of the first semiconductor layer 102 which is a portion where the first electrode 105 is to be formed is exposed. Thereafter, a metal layer is formed on the second semiconductor layer 104. The metal layer may be formed by performing one method selected from the group consisting of e-beam evaporation, thermal evaporation, and sputtering. The metal layer may be formed of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), and aluminum (Al), and the thickness of the metal layer may be 1 nm to 5 nm.

Thereafter, a graphene layer is formed on the metal layer. The graphene layer may be formed by depositing by CVD using a mixed gas of CH ₄ , H ₂ and Ar at 1000 ° C. to 1200 ° C. under an argon (Ar) atmosphere.

The thickness of the graphene layer formed as described above is 0.1 nm to 10 nm, and a bonding pad 108 for external connection may be formed on the metal / graphene transparent electrode 107.

Thereafter, a portion of the light emitting structure of the light emitting device is etched to form the first electrode 105 on the exposed n-type semiconductor layer. The bonding pad 108 is not particularly limited, but Cr / Au or Ni / Au may be used, and the bonding pad 108 is not particularly limited, but Cr / Au, Ni / Au, Ti / Au, and the like. One selected from the group consisting of Ti / Al / Ni / Au may be used.

A method of manufacturing a vertical light emitting device according to an embodiment of the present invention will be described with reference to FIG. 2.

The light emitting structure S including the first conductive semiconductor layer 102, the active layer 120, and the second conductive semiconductor layer 104 is formed on the first substrate (not shown). Thereafter, the reflective layer 201 or the adhesive layer 202 is formed on the second conductivity-type semiconductor layer 104. If the reflective layer 201 may serve as the adhesive layer 202, the forming of the adhesive layer 202 may be omitted. Thereafter, a second substrate 203 is formed on the adhesive layer 202. The second substrate 203 may be formed by an electrochemical metal deposition method or a bonding method using a eutectic metal.

Next, after removing the first substrate (not shown) to expose the first conductivity type semiconductor layer 102, the first electrode 105 is formed on the first conductivity type semiconductor layer 102. The first electrode 105 is not particularly limited but may be one selected from the group consisting of Cr / Au, Ni / Au, Ti / Au, and Ti / Al / Ni / Au.

Thereafter, in order to form the metal / graphene electrode 107 as the second electrode on the second substrate 203, first, a metal layer is formed on the second substrate 203 (S301). The metal layer is formed by carrying out one method selected from the group consisting of e-beam evaporation, thermal evaporation and sputtering. The metal layer may be formed of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), and aluminum (Al), and the thickness of the metal layer may be 1 nm to 5 nm. Thereafter, a graphene layer is formed on the metal layer. The graphene layer may be formed by depositing by CVD using a mixed gas of CH ₄ , H ₂ and Ar at 1000 ° C. to 1200 ° C. under an argon (Ar) atmosphere.

The thickness of the graphene layer formed as described above is 0.1 nm to 10 nm, and a bonding pad 108 for external connection may be formed on the metal / graphene transparent electrode 107.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are only for illustrating the present invention, and the scope of the present invention will not be construed as being limited by these Examples.

Example : metal/ Graphene  Transparent electrode

Nickel (Ni) was deposited on the conductive semiconductor layer using an e-beam evaporator to form a nickel layer. Then, a light emitting device in which a nickel layer was formed on a quartz tube was placed, and the temperature was raised to 1000 ° C. under argon (Ar) conditions. The mixed gas of CH ₄ , H ₂ and Ar was flowed at a flow rate of CH ₄ : H ₂ : Ar = 50: 65: 200 sccm. Then, a rapid cooling at a rate of 10 ° C / s under argon (Ar) conditions to prepare a metal / graphene transparent electrode.

3 and 4 are optical micrographs before and after applying a bias to the metal / graphene transparent electrode according to the present invention. Referring to FIG. 3, the transparent portion of white in the graphene layer is a thin graphene layer and the opaque portion is a thick graphene layer. As the graphene layer becomes thicker, the transparency decreases. In FIG. 4, when a bias is applied to the metal / graphene layer, strong light is emitted from the thin transparent portion of the graphene layer, and light is hardly emitted from the thick portion of the graphene layer.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

101: first substrate
120: buffer layer
102: first conductive semiconductor layer
103: active layer
104: second conductivity type semiconductor layer
105: first electrode
107: metal / graphene transparent electrode (second electrode)
108: bonding pad
201: reflective layer
202: adhesive layer
203: second substrate
S: light emitting structure

Claims (14)

A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer;
A metal / graphene transparent electrode formed on the second conductive semiconductor layer; And
A first electrode formed on the first conductive semiconductor layer;
Light emitting device comprising a.
The method of claim 1,
The metal / graphene transparent electrode has a structure in which a graphene layer is formed on a metal layer.
The method of claim 2,
The metal layer is a light emitting device, characterized in that made of one selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd) and aluminum (Al).
The method of claim 2,
The thickness of the metal layer is a light emitting device, characterized in that 1 nm to 5 nm.
The method of claim 2,
The thickness of the graphene layer is a light emitting device, characterized in that 0.1 nm to 10 nm.
The method of claim 1,
The light emitting device is characterized in that formed on the first substrate.
The method of claim 1,
And a reflective layer, an adhesive layer, and a second substrate between the second conductive semiconductor layer and the metal / graphene electrode.
(a) forming a light emitting structure on the first substrate, the light emitting structure including a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer;
(b) forming a metal layer on the second conductivity type semiconductor layer;
(c) forming a graphene layer on the metal layer; And
(d) forming a first electrode on the first conductivity type semiconductor layer;
Light emitting device manufacturing method comprising a.
The method of claim 8,
Between steps (a) and (b),
And etching the portion of the light emitting structure to expose the first conductivity type semiconductor layer.
The method of claim 8,
Between steps (a) and (b),
Forming a reflective layer on the second conductivity type semiconductor layer;
Forming an adhesive layer on the reflective layer;
Forming a second substrate on the adhesive layer; And
Removing the first substrate;
Light emitting device manufacturing method comprising a further.
The method of claim 8,
The step (b) is a light emitting device manufacturing method characterized in that is carried out by one method selected from the group consisting of e-beam evaporation (thermal evaporation), thermal evaporation (thermal evaporation) and sputtering (sputtering).
The method of claim 8,
The step (c) is a light emitting device manufacturing method characterized in that it is carried out by CVD (Chemical Vapor Deposition) method.
An illumination device comprising the light emitting element according to any one of claims 1 to 7.
A display device comprising the light emitting element according to any one of claims 1 to 7.

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