KR101907742B1 - Light emitting diodes Thermoelectric material, method of fabricating the same, and thermoelectric device - Google Patents

Abstract

The present invention relates to a light emitting diode and a method of manufacturing the same. According to an embodiment of the present invention, there is provided a semiconductor device comprising a first electrode, an N-type zinc oxide layer containing nano-rods of zinc oxide on the first electrode, a nano-rod of copper oxide formed on the zinc oxide layer, And a second electrode formed on the copper oxide layer may be provided.

Description

TECHNICAL FIELD [0001] The present invention relates to a light emitting diode and a method of manufacturing the light emitting diode.

The present invention relates to a light emitting device, and more particularly, to a light emitting diode capable of forming a low temperature and a method of manufacturing the same.

Solid-state light-emitting diodes (LEDs) are quickly replacing conventional lamp-based lighting because of their high energy efficiency despite their small size. In addition, since the solid-state light emitting diode can generate light of various colors, it is very useful in the display device field. After the development of white light emitting diodes, the need for more economical and stable light emitting diodes has been the focus of research. Light emitting diodes formed with conventional III-V semiconductors, such as GaN and GaAs based materials, can be fabricated using state of the art vacuum deposition techniques, such as metal organic chemical vapor deposition, molecular beam epitaxy, or other suitable vapor deposition Technology is used at a high temperature and a high purity, a very expensive process is required. Further, the optical characteristics of the light emitting diode are changed when exposed to a high temperature for a long time.

Development of stable, abundant, economically manufacturable and non-toxic materials for replacing these expensive III-V semiconductors has recently been achieved through oxide semiconductors. In order to fabricate an LED using the oxide semiconductor, the electrical characteristics and optical characteristics of the oxide semiconductor must be simultaneously controlled.

SUMMARY OF THE INVENTION The present invention provides a light emitting diode using an oxide semiconductor which is stable, abundant, economical and capable of controlling electrical characteristics and optical characteristics of an oxide semiconductor.

It is another object of the present invention to provide a method of manufacturing an LED capable of economically manufacturing an oxide semiconductor having the above-described advantages.

According to an aspect of the present invention, there is provided a liquid crystal display comprising: a first electrode; A zinc oxide layer comprising N nanorods of zinc oxide on said first electrode; A P-type oxidized copper layer formed on the zinc oxide layer and including nano rods of copper oxide forming a heterojunction; And a second electrode formed on the copper oxide layer.

The nanoparticles of copper oxide have a length of 400 nm to 500 nm and a thickness of 50 nm to 100 nm. The thickness of the P-type copper oxide layer is in the range of 1 탆 to 3 탆. The nanorods of the copper oxide have a monoclinic crystal structure that is first grown with a (111) plane.

The nanorods of the zinc oxide have a hexagonal wurtzite crystal structure grown first with a (002) plane. The nanorods of the zinc oxide have a length of 500 nm to 700 nm. The thickness of the N-type zinc oxide layer is in the range of 400 nm to 800 nm.

The first peak of the light emitting diode has electroluminescence characteristics within a range of 610 to 620 nm. And the second peak of the light emitting diode has electroluminescence characteristics in the range of 710 to 720 nm. The copper oxide layer has a carrier concentration of 9.64 x 10 18 cm ^-3 or more. The light emitting diode has a constant rectification ratio of 10 ⁵ or more.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a first electrode on a substrate; Forming a zinc oxide layer comprising nanorods of zinc oxide on the first electrode; Forming a copper oxide layer comprising nano-rods of copper oxide on the zinc oxide layer; And forming a second electrode on the copper oxide layer.

Wherein forming the zinc oxide layer comprises: forming a mold pattern on the substrate, the mold pattern having an opening region for exposing the first electrode; And forming the zinc oxide layer in the opening region of the mold pattern, wherein the forming the copper oxide layer comprises: forming the copper oxide layer on the stamp substrate; Contacting the surface of the stamp substrate on which the copper oxide layer is formed on a mold pattern on which the zinc oxide layer is formed to pressurize; And removing the stamp substrate to transfer a portion of the oxidized copper layer onto the upper surface of the zinc oxide layer in the opening region of the mold pattern.

Forming a copper oxide layer, by dissolving copper nitrate trihydrate _{(Cu (NO 3) 2.3H 2} O) and potassium hydroxide (KOH) in a solvent to form a mixed solution; Irradiating the mixed solution with a microwave to generate a reaction solution in which copper oxide powder is dispersed; Drying the reaction solution to obtain the copper oxide powder; And coating the copper oxide powder on the stamp substrate.

The step of obtaining the copper oxide powder may include washing the reaction solution before drying the reaction solution; And centrifuging the washed reaction solution to obtain the copper oxide powder.

The manufacturing method of the light emitting diode further includes the step of adding ethylene glycol to the mixed solution.

The mold pattern includes a photoresist (PR) pattern, and the step of forming the zinc oxide layer is performed by hydrothermal synthesis. The nanorods of the zinc oxide are grown vertically on the electrode. The zinc oxide layer has a single crystal structure, and the copper oxide layer has a polycrystalline structure.

According to an embodiment of the present invention, an N-type zinc oxide layer containing nanorods of zinc oxide and a P-type oxidized copper layer containing nanorods of copper oxide formed on the zinc oxide layer to form a heterojunction are included A light emitting diode using an oxide semiconductor is provided which is stable and abundant and can be economically manufactured and which can control electrical characteristics and optical characteristics of an oxide semiconductor.

Further, according to another embodiment of the present invention, a method of manufacturing a light emitting diode having the above-described advantages can be provided.

1 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention.
2A and 2B are SEM images of a zinc oxide layer containing zinc oxide nanorods according to an embodiment of the present invention.
Figure 3a shows an x-ray diffraction (XRD) pattern for a zinc oxide layer according to one embodiment of the present invention.
Figure 3b shows UV-VIS absorption spectra for the zinc oxide layer according to one embodiment of the present invention.
4A and 4B are SEM images of a copper oxide layer containing nanorods of copper oxide according to an embodiment of the present invention.
5A and 5B show XRD patterns and UV-VIS absorption spectra for respective copper oxide layers according to an embodiment of the present invention.
6A and 6B are TEM images showing the crystalline properties of the nano-rods of copper oxide according to an embodiment of the present invention.
7 is a flowchart illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.
8 is a view illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.
9A to 9D are SEM images corresponding to main steps of a method of manufacturing a light emitting diode according to an embodiment of the present invention.
10A and 10B are graphs showing electrical characteristics of light emitting diodes.
11A to 11D are diagrams showing emission characteristics of electroluminescence and photoluminescence.
12 is a view showing a coupling induction release mechanism according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

Like numbers refer to like elements in the drawings. Also, as used herein, the term "and / or" includes any and all combinations of any of the listed items.

The terms used herein are used to illustrate the embodiments and are not intended to limit the scope of the invention. Also, although described in the singular, the present invention may include plural forms, unless the context clearly dictates the singular value. Also, the terms "comprise" and / or "comprising" used herein should be interpreted as referring to the presence of stated shapes, numbers, steps, operations, elements, elements and / And does not exclude the presence or addition of other features, numbers, operations, elements, elements, and / or groups.

Reference herein to a layer formed "on" a substrate or other layer refers to a layer formed directly on top of the substrate or other layer, or may be formed on intermediate or intermediate layers formed on the substrate or other layer Layer. ≪ / RTI > It will also be appreciated by those skilled in the art that structures or shapes that are "adjacent" to other features may have portions that overlap or are disposed below the adjacent features.

As used herein, the terms "below," "above," "upper," "lower," "horizontal," or " May be used to describe the relationship of one constituent member, layer or regions with other constituent members, layers or regions, as shown in the Figures. It is to be understood that these terms encompass not only the directions indicated in the Figures but also the other directions of the devices.

In the following, embodiments of the present invention will be described with reference to cross-sectional views schematically illustrating ideal embodiments (and intermediate structures) of the present invention. In these figures, for example, the size and shape of the members may be exaggerated for convenience and clarity of explanation, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, embodiments of the present invention should not be construed as limited to any particular shape of the regions shown herein. In addition, reference numerals of members in the drawings refer to the same members throughout the drawings.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, the light emitting diode 10 includes a first electrode E1, an N-type zinc oxide layer Z1 including zinc oxide nanorods on the electrode E1, And a second electrode E2 formed on the P-type oxidized copper layer C1 including the nano rods of copper oxide forming the heterojunction and the copper oxide layer C1.

The light emitting diode 10 may be formed on a substrate (not shown). The substrate may be an insulating substrate itself such as ceramic or polyimide, a semiconductive substrate such as a silicon wafer, or even a conductive substrate such as a leadframe. Further, an insulating film such as silicon oxide, silicon nitride, or aluminum oxide, a metal conductive film, or a semiconductor film may be formed on the surface of these substrates, and the present invention is not limited thereto. The substrate may be formed of a flexible polymer-based material such as a resin-based material because the light-emitting diode 10 can be synthesized at a low temperature as described later. The light emitting diode 10 may be formed on the conductive substrate or the conductive film. In this case, the conductive substrate or the conductive film may constitute the first electrode E1 of the light emitting diode 10. In one embodiment of the present invention, the first electrode E1 may be a transparent conductive film, for example, a transparent conductive metal oxide thin film or a conductive nanowire laminate. The transparent conductive metal oxide thin film may be formed of at least one selected from the group consisting of ZnO, Ga-doped ZnO, ITO, IGO, IZO, IGZO, indium gallium zinc oxide, , And ZTO (Zinc Tin Oxide). However, the metal oxide thin film in the present invention is not limited thereto. The conductive nanowire laminate may include at least one of nickel (Ni), gold (Au), platinum (Pt) and alloys thereof, carbon (C), silicon (Si) and germanium (Ge), silicon oxide The nanowire may be composed of a material selected from the group consisting of TiO ₂ , WOx, GaN, InP, and SiC. The nanowires may be nanowires, nanotubes, It can be a nano-rod.

The N-type zinc oxide layer (Z1) may be composed of zinc oxide grown on the basis of a hydrothermal synthesis method. For example, zinc oxide can have a variety of nanostructures such as nanorods, nanoflowers, nanowires, and nanosheets. In one example of the present invention, zinc oxide grown on the basis of hydrothermal synthesis has a structure of nanorods, and the N-type zinc oxide layer (Z1) may include nanorods of zinc oxide. At this time, the nanorods of zinc oxide can be grown inside the mold pattern described later. The hydrothermal synthesis method is widely used in the production of various kinds of materials due to its simple equipment structure, process, low manufacturing cost and environment friendliness. Variables for controlling the characteristics of zinc oxide grown by the hydrothermal synthesis include precursor concentration, growth temperature, and growth time. In particular, growth temperature is an important thermodynamic parameter because it regulates the mechanism of the chemical reaction. For example, growth temperature affects the morphology, crystallinity and optical properties of zinc oxide grown by hydrothermal synthesis.

The thickness of the N-type zinc oxide layer (Z1) is in the range of 400 nm to 800 nm. In addition, the zinc oxide nanorods have a hexagonal wurtzite crystal structure grown first with a (002) plane, and the zinc oxide nanorods have a length of 500 nm to 700 nm.

The P-type oxidized copper layer (C1) can be formed on the N-type zinc oxide layer (Z1) through a low-temperature solution process using a microwave reaction or a nanoimprint process to be described later. For example, copper oxide powders are produced through a low-temperature solution process, and the copper oxide powders are coated on a second substrate (a bare substrate or a stamp substrate) different from the first substrate on which the first electrode E1 is formed, By performing the nanoimprint process using the substrate and the second substrate, the P-type oxidized copper layer (C1) can be formed.

The thickness of the P-type copper oxide layer is in the range of 1 탆 to 3 탆. The nano rods of copper oxide contained in the P-type copper oxide layer (C1) have a length of 400 nm to 500 nm and a thickness of 50 nm to 100 nm, and the nano rods of the copper oxide are preferentially And has a grown monoclinic crystal structure. The copper oxide layer may have a carrier concentration of 9.64 x 10 18 cm -3 or more.

When a bias voltage is supplied to the light emitting diode to which the zinc oxide layer (Z1) and the copper oxide layer (C1) are bonded, electrical shorting may occur in the light emitting diode. However, as described above, the P-type oxidized copper layer (C1) may be formed thicker than the N-type zinc oxide layer (Z1), which can prevent the electrical short.

The second electrode E2 may be the same as or different from the first electrode E1. For example, when the second electrode E2 is different from the first electrode E1, the second electrode E2 may be made of Au, Cu, Ag, Ag-Cu alloy, Co, , Nickel (Ni), or the like.

The first peak of the light emitting diode has an electroluminescence characteristic in a range of 610 to 620 nm and the second peak of the light emitting diode has an electroluminescence characteristic in a range of 710 to 720 nm. In addition, the light emitting diode may have a constant rectification ratio of 10 ⁵ or more.

2A is a scanning electron microscope (SEM) image of a zinc oxide layer Z1 according to an embodiment of the present invention, and FIG. 2B is a SEM image of a cross section of a zinc oxide layer Z1 formed. The substrate used was a glass substrate, and as the first electrode, a GZO electrode pattern was used. In addition, the nanorod layer was formed within the opening of a photoresist (PR) patterned to have openings on the substrate.

The PR pattern may have a shape in which a plurality of circular openings are uniformly distributed. The nanorods of zinc oxide disposed in one circular opening can constitute one light emitting diode. In another embodiment, the nanorods of zinc oxide disposed in at least two or more circular openings may constitute one diode. The circular pattern is only one example, and is not limited to the present invention. For example, the opening pattern of the PR may appear in various forms such as a hexagon, a square, or an ellipse.

Referring to FIGS. 2A and 2B, it is observed that the zinc oxide nano-rods are densely, uniformly and vertically aligned inside the PR pattern. The length of the nanorods of zinc oxide in the PR pattern after hydrothermal growth for 1 hour has a size of about 600 nm within the range of 500 nm to 700 nm.

FIG. 3A shows an X-ray diffraction (XRD) pattern of the zinc oxide layer Z1. Referring to FIG. 3A, a main peak P1 occurs at a 2θ value of 34.38 degrees, from which the zinc oxide nanorods in the zinc oxide layer Z1 have a hexagonal wurtzite lattice structure, 002) plane. Further, in the zinc oxide nanowires in the zinc oxide layer (Z1) according to the embodiment of the present invention, a small peak due to the (004) plane of the hexagonal Wurtzite lattice is observed at a 2? Value of 72.8 degrees. From these results, it can be seen that the nanorods of zinc oxide in the zinc oxide layer (Z1) according to the embodiment of the present invention have a single crystal structure, and the single crystal structure is preferentially grown in the c-axis direction.

3B shows the UV-VIS absorption spectrum of the zinc oxide layer (Z1). Referring to FIG. 3B, it can be seen that zinc oxide nanorods exhibit significant absorption at 376 nm. Also, referring to the illustration IS of FIG. 3B, the optical bandgap was calculated to be 3.3 eV based on the Tauc graph.

4A and 4B are SEM images of nanorods of copper oxide according to an embodiment of the present invention. In Fig. 4A, the nanorods of copper oxide were formed by a spin coating method on a stamp substrate. In Fig. 4B, the nano-rods of copper oxide were transferred from the stamp substrate of Fig. 4A to the zinc oxide layer Z1 by a nano-imprint process and formed on the zinc oxide layer Z1. The imprint process may include transferring the nanorods of copper oxide coated on the stamp substrate to the zinc oxide layer Z1 using a stamp substrate (e.g., polydimethylsiloxane (PDMS) as a non-limiting example) Rubbing the nano rods of copper oxide in the zinc oxide layer Z1 so as to form uniformly and smoothly, and pressing the nano rods of the copper oxide to adhere to the zinc oxide layer Z1 do.

Referring to FIG. 4A, nanowires of copper oxide coated on a bare substrate before the nanoimprint process each have an average length in the range of 400 nm to 500 nm and an average width in the range of 50 nm to 100 nm. In particular, copper oxide nanorods exhibited a unique tendency of agglomeration.

Referring to FIG. 4B, it is confirmed that the nano-rods of the copper oxide are formed uniformly, smoothly, and densely on the zinc oxide layer Z1. This uniform, smooth, dense character facilitates the formation of the second electrode on the copper oxide layer (C1) comprising the nanorods of the copper oxide.

5A and 5B show XRD patterns and UV-VIS absorption spectra of nanoparticles of copper oxide formed on the zinc oxide layer Z1, respectively.

Referring to FIG. 5A, it can be seen that all peaks are associated with copper oxide (JCPDS file no. 48-1548 C2 / c) having a standard monoclinic crystal structure. From the XRD results, it can be seen that the copper oxide nanorods are pure copper oxide free from other impurities. The nanorods of the copper oxide have a monoclinic crystal structure that is first grown with a (111) plane.

Referring to FIG. 5B, light is absorbed within a wavelength range of 200 nm to 9000 nm, and light is not absorbed in other wavelength ranges. In addition, the optical bandgap of the nanoparticles of the copper oxide was found to be approximately 1.4 eV in the range of 1.25 eV to 1.75 eV.

6A and 6B are TEM images showing the crystalline properties of nano-rods of copper oxide. Specifically, FIG. 6A is a TEM image of copper oxide showing a rod like the shape according to the SEM image shown in FIG. 4A. Figure 6b is a high resolution lattice image that confirms the polycrystalline nature of copper oxide nano rods in various directions. The illustration IS of FIG. 6B shows a selected-area electron diffraction (SAED) pattern in a reciprocal lattice system. The hall effect measurements of the nano rods of copper oxide at room temperature show a carrier concentration of P-type characteristics of greater than 9.64 x 10 ¹⁸ cm ^-3 and a resistivity of 1.77 cm ² / V with a resistivity of 2.7 Ω · cm Lt; RTI ID = 0.0 > s. ≪ / RTI > This electrical characteristic indicates that there is a possibility of using the copper oxide layer (C1) by the low temperature solution process as an efficient hole transport layer in the LED.

7 is a flowchart illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 7, a first electrode E1 is formed on a substrate, a zinc oxide layer Z1 containing zinc nano-rods is formed on the first electrode E1, A copper oxide layer C1 including nano rods of copper oxide is formed on the zinc oxide layer Z1 in step S30 and a second electrode E2 is formed on the copper oxide layer C1 in step S40 ).

The step (S20) of forming the zinc oxide layer (Z1) may include forming a mold pattern having an opening region for exposing the first electrode (E1) on the substrate, And forming a zinc oxide layer. The step of forming the copper oxide layer (C1) includes the steps of: forming the copper oxide layer on the stamp substrate; contacting the surface on which the copper oxide layer is formed on the stamp substrate with a mold pattern on which the zinc oxide layer is formed, And removing the stamp substrate to transfer a portion of the oxidized copper layer onto the upper surface of the zinc oxide layer within the aperture region of the mold pattern. The stamp substrate is a bare substrate without patterning and may be made of polydimethylsiloxane (PDMS). However, in the present invention, the stamp substrate is not limited to the material of the PDMS. For example, the stamp substrate may be composed of polypropylene (PP), polystyrene (PS), polyethylene (PE), or polyvinyl chloride (PVC).

The step of forming the copper oxide layer (C1) comprises dissolving copper nitrate trihydrate (Cu (NO3) 2.3H2O) and potassium hydroxide (KOH) in a solvent (e.g., water, alcohol, distilled water) A step of forming a reaction solution in which copper oxide powder is dispersed by irradiating a microwave to the mixed solution and reacting the solution to obtain a copper oxide powder; drying the reaction solution to obtain the copper oxide powder; And further coating the copper powder. The step of obtaining the copper oxide powder may further include washing the reaction solution before drying the reaction solution and centrifuging the washed reaction solution to obtain the copper oxide powder .

The step of forming the copper oxide layer (C1) may further include adding ethylene glycol to the mixed solution. The mold pattern may include a photoresist (PR) pattern.

The step of forming the zinc oxide layer may be performed by hydrothermal synthesis. For example, the hydrothermal synthesis method is a method of synthesizing a metal oxide or a metal powder by using a property depending on the solubility, temperature, pressure and solvent concentration of a substance in a solution state or a suspension state, or to grow crystals.

The nano-rods of the zinc oxide may be vertically grown on the first electrode, the zinc oxide layer may have a single crystal structure, and the copper oxide layer may have a polycrystalline structure.

8 is a view illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 8, 3 wt% Ga-doped ZnO (GZO) is deposited by physical vapor deposition (e.g., thermal evaporation, electron beam evaporation, sputtering), chemical vapor deposition (e.g., thermal decomposition, photolysis, redox reaction, (A), on a substrate Pl (e.g., glass). However, (a) in the present invention is not limited to chemical vapor deposition, physical vapor deposition, chemical vapor deposition, and atomic layer deposition. For example, (a) may be performed by atomic layer deposition. In addition, the GZO-coded substrate Pl can be cleaned by continuous sonication in acetone, methanol and de-ionized (DI water) (18.2 M?). However, in the present invention, cleaning is not limited to these. For example, water, distilled water or ethanol may be used as the cleaning agent.

A mold pattern MP having an opening area OP for exposing GZO on the substrate P1 may be formed using an optical lithographic technique. The mold pattern may be a PR pattern, and the PR pattern may have a plurality of uniformly distributed circular openings (OPs) of about 5 mu m in diameter. Continuous, compact and uniform nanorods of zinc oxide can be formed in the mold pattern (MP).

An aqueous solution containing about 297.49 mg of zinc nitrate hexahydrate (Zn (NO ₃ ) 2.6H ₂ O) and about 140.19 mg of hexamethylenetetramine (HMT) at a temperature of about 90 ° C for 1 hour At about 50 ml, nanorods of undoped zinc oxide are grown on the patterned GZO coated substrate (P1) (c).

In addition, nanoproducts of copper oxide are synthesized utilizing the easy low temperature solution method in the MARS 6 microwave reaction system of CEM. For example, 181.2 mg of copper nitrate trihydrate (Cu (NO3) 2.3H2O) and 168.33 mg of potassium hydroxide (KOH) are dissolved in 15 ml of DI water to form a mixed solution. Subsequently, about 2 ml of the reaction accelerator may be added to the mixed solution. For example, the reaction promoter may be a chelating agent, and the chelating agent may be selected from the group consisting of ethylene glycol, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediamine sesquioxide, sodium diethylenetriaminepioacetate, It may be one of sodium acetate. However, in the present invention, the chelating agent is not limited thereto.

At this time, the total volume may be 30 ml, including nanopure water. The mixed solution is accommodated in a reaction vessel (e.g., a microwaveable teflon vessel), the temperature of the vessel is fixed at 100 ° C, and the microwave reaction is performed for 2 hours. After the completion of the reaction, the reaction solution containing the copper oxide powder is centrifuged to obtain a copper oxide powder. In addition, the reaction solution can be washed with DI water or ethanol before centrifugation. The washed reaction solution may be dried at about < RTI ID = 0.0 > 60 C < / RTI >

The surface morphology of the nanoparticles of copper oxide can be analyzed using Hitachi S5000 scanning electron microscopy (SEM). Structural properties of the nanoparticles of copper oxide can be analyzed using JEOL's JEM-ARM 200F transmission electron microscope (TEM). The Rigaku UltimaIV X-ray diffractometer can be used to investigate the crystallinity of the material. The optical properties of the nanoparticles of copper oxide can be investigated using a JASCO V-670 UV-VIS spectrophotometer. X-ray photoelectron spectroscopy (XPS) can be performed using AXIS-NOVA (KRATOS Inc.) with monochromatic Al-Ka (1486.6 eV) to determine the chemical composition and purity of newly grown copper oxide nanorods . The electrical properties of the nanoparticles of copper oxide can be investigated by measuring the room temperature Hall effect in a van der Pauw configuration.

The obtained copper oxide powder can be formed on the nanorods of the patterned zinc oxide using a nanoimprint process (d).

In the nanoimprinting process, a monolayer (CP) in which the obtained copper oxide powders are coded may be formed on a stamp substrate (ST) (for example, PDMS). A monolayer CP containing copper oxide powders on the stamp substrate ST is then brought into contact with the substrate P1 comprising the nanorods of zinc oxide grown on each opening OP of the mold pattern MP.

Thereafter, using the rubbing and pressing techniques, the copper oxide powders of the single layer (CP) are transferred corresponding to the respective openings OP of the mold pattern MP of the substrate P1, OP), copper oxide powders may not be transferred (e). Through the rubbing technique, nano rods of copper oxide can be horizontally aligned on the nano rods of vertically aligned zinc oxide to form a uniform layer (A). This technique can form a PN heterojunction between the nanorods of zinc oxide and the nanorods of copper oxide in an aperture (OP) in a mold pattern (MP), that is, within a 5 μm circular opening. In addition, compacting and smooth surfaces of the nanorods of copper oxide are obtained through pressing by PDMS. This may be easy to deposit gold (Au) electrodes without pinholes.

As described above, by using the nanoimprint process, it is easy to fill copper oxide powders in a circular pattern of 5 mu m unlike the spray or spin coating technique. It is also possible to form the zinc oxide layer Z1 and the copper oxide layer C1 (C1) through the nanoimprint process rather than growing and collecting the copper nano rods for forming the copper oxide layer C1 directly on the zinc oxide layer Z1. Is excellent in performance.

In one embodiment of the present invention, after the nanoimprinting process, a further heat treatment process may be performed to ensure that the PN heterojunction between the zinc oxide layer and the copper oxide layer is firmly adhered.

Finally, the device is annealed at 200 < 0 > C for 1 hour in an argon atmosphere with a flow rate of 1.5 LPM. Using an e-beam evaporator, gold was formed on the copper oxide layer as a p-type electrode while GZO was used as the bottom electrode. Electrical measurements of the PN heterojunction were performed using a semiconductor device analyzer by Agilent Technologies B1500A. Electroluminescence (EL) of the device was investigated using Andor SOLIS simulation software coupled with a CCD camera (CamWare 64). To measure emission sources from devices, room temperature photoluminescence (PL) measurements were performed using an IK3252R-E-He-Cd (325 nm) laser source combined with a MonoRa 320i monochromator and Andor SOLIS simulation package ≪ / RTI >

9A to 9D are SEM images corresponding to main steps of a method of manufacturing a light emitting diode according to an embodiment of the present invention. FIG. 9A is an SEM image of zinc oxide nanorods oriented in step (c) of FIG. 8, and FIG. 9C is an SEM image of copper oxide nanorods formed on zinc oxide nanorods in step (e) . FIG. 9B is a cross-sectional view of zinc oxide nano-rods corresponding to FIG. 9A, and FIG. 9D is a cross-sectional view of copper oxide nanorods corresponding to FIG. 9C. 9D, the thickness of the zinc oxide layer Z1 is about 600 nm in the range of 400 nm to 800 nm, while the thickness of the copper oxide layer C1 is about 1 mu m in the range of 1 mu m to 3 mu m Can be observed.

10A and 10B are graphs showing electrical characteristics of light emitting diodes. FIG. 10A is a graph showing current-voltage characteristics of the PN heterojunction, and FIG. 10B is a graph showing current flow stability and durability when a bias voltage is applied for a predetermined time. As shown in the illustration IS of Fig. 10A, in order to perform DC electrical measurement of the heterojunction, a gold (Au) electrode is formed on the copper oxide layer C1 by an e-beam evaporator .

Referring to FIG. 10A, a PN heterojunction diode characteristic with a forward-biased current-voltage IV of 3.2 V cut-in voltage and a very high rectifying ratio of 4 V to 10 ⁵ appears. It has been found that in-rush current, which can cause permanent damage to the device, is a common phenomenon in LEDs. Avalanche Joule heating can easily damage LED due to radiative recombination of charge carriers emitting photons with many non-radiative charge carriers. Thus, in order to protect the diode from uncontrollable inrush current and continuous damage, a current compliance of 100 mA can be defined during the IV measurement.

Referring to FIG. 10B, it can be seen that when a voltage stress of 4 V is applied to the light emitting diode for 50 seconds, a stable current flow of 30 mA appears. As described above, it can be seen that the light emitting diode of the present invention has a high value of rectification ratio and a stable current flow.

11A to 11D are diagrams showing emission characteristics of electroluminescence and photoluminescence. 11A is a graph showing electroluminescence behavior under a DC forward bias of 4 V and FIG. 11B is a graph showing electroluminescence operation under a DC forward bias of 5 V. FIG. Electroluminescence (EL) was measured by identifying photon emission corresponding to current flow.

Referring to FIGS. 11A and 11B, when the forward bias was increased by 1 V from 4 V to 5 V, the electroluminescence intensity increased more than twice. The emitted photons have a broad range of wavelengths of visible light corresponding to orange-red light having a first peak at approximately 610-620 nm and a second peak at approximately 710-720 nm.

In order to irradiate the emission light source, the defect state of the zinc oxide nano-rods was confirmed using the room temperature photoluminescence (PL) shown in Fig. 11C. 11C is a graph showing the emission characteristics of the light emission (PL).

Referring to FIG. 11C, in addition to the helium-cadmium laser at 325 nm and the peak associated with near band edge emission (NBE) near 380 nm, a 500 a broad visible light range peak appeared from nm to 800 nm. NBE is light emission by free exciton emission, and DLE is light emission by defect. For example, DLE is an interstitial zinc (Zni), interstitial oxygen (Oi), zinc vacancy (VZn), oxygen vacancy (Oxygen) vacancy (VO), as well as the transitions between intrinsic point defects such as vacancy (VO). DLE maintains the intensity of the first peak at about 610 nm, corresponding to a second peak of about 720 nm corresponding to orange-red light, red light. Here, the first peak has a larger value than the second peak. Thus, it can be seen that through the photoluminescence spectrum, electroluminescence (EL) emission of orange-red light occurs from zinc oxide nanorods. The aforementioned ZnO defects can effectively be used for purple, blue, green, yellow, orange-red and red light emission. Thus, a combination of RGB colors (red-green-blue) may result in a low-cost white color.

11D is an image of orange-red light emitted from a heterojunction diode under a forward bias of 4V. The illustration (IS) in Fig. 11d shows luminescence from a single 5 [mu] m patterned device.

12 is a view showing a coupling induction release mechanism according to an embodiment of the present invention. Particularly, Fig. 12 is a band diagram before and after making contact between the P-type copper oxide and the N-type zinc oxide, respectively.

12, the electron affinity (xi) and the work function (? 1) values of copper oxide nanowires related to band-bending are respectively in the range of χ = 1 to 4.07, 5.3, and the values of the electron affinity (x2) and the work function (? 2) of zinc oxide nanorods related to band-bending are? = 2 to 4.5 and? = 2 to 4.7, respectively (a). The bandgap of the copper oxide nanorods is 1.4 eV and the bandgap of the zinc oxide nanorods is 3.3 eV.

After contact, the conduction band (CB) offset (ΔEC) and valence band offset (ΔEV) were 1 eV and 2.9 eV, respectively, causing an absolute barrier to carrier flow through the depletion region (b). This high value of the band offset is seen to interfere with the direct flow of the charge carriers and to allow radiative recombination in the depletion region of the heterojunction. If the band gap of the copper oxide nanorods is only 1.4 eV, the radiation recombination corresponding to the visible light range is excluded from the CuO layer. It is assumed that the radiative recombination does not occur in the copper oxide layer (C1) because of the low-crystalline nature.

On the other hand, the zinc oxide nanorods showed a high-intensity broad-range DLE in the PL spectrum and confirmed the presence of intrinsic point defects in the undoped ZnO lattice. After confirming the possibility of transitions associated with all defects, it is assumed that the first peak associated with the orange-red (610 nm) emission is due to the transition of Zni to Oi. A second peak (or shoulder peak) (710 nm) smaller than the first peak associated with red light is seen to be due to the transition of the conduction band (CB) to VO. Therefore, it is assumed that the transition occurs within the lattice of the ZnO in the depletion region due to the occurrence of defects. (c) is a schematic diagram showing the corresponding transition and photon emission. The locations of defect levels within the bandgap of ZnO have been considered in accordance with the prior art. Thus, zinc oxide nanorods contain many Zni, Oi, and Vo defects. These surface defects were incorporated as a result of intense DLE in the orange-red region.

As described above, in embodiments of the present invention, P-type copper oxide nanowires / N-type zinc oxide nanorods heterojunction LEDs based on a low temperature solution-treated oxide material and a method of manufacturing the same are provided. Copper oxide nanorods were prepared by microwave synthesis at 100 ℃. The copper oxide nanorods have electrical properties with a high hole concentration of 9.64 × 10 18 cm -3 or more and exhibit unique cohesive structural properties. The light emitting diode showed a steady rectification ratio of 10 ⁵ at 4 V. Orange-red light emission from the light emitting diode was visually observed. The photoluminescence (PL) spectra of zinc oxide nanorods have resulted in a wide DLE (deep level emission), including many defect states.

Also, in the electroluminescence (EL) spectrum, an orange-red emission in the visible range with a second peak at 710 nm and a first peak at 610 nm above the second peak was observed. The red emission at 710 nm is related to the transition from conduction band (CB) to VO, whereas the orange emission at 610 nm is related to the transition from Zni to Oi. Thus, in an embodiment of the present invention, an orange-red light was observed utilizing an inherent point defect of zinc oxide nanorods, satisfying an LED based on a low cost oxide material.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be clear to those who have knowledge.

E1: a first electrode,
Z1: an N-type zinc oxide layer (Z1)
C1: a P-type oxidized copper layer (C1) and a copper oxide layer
E2: second electrode,

Claims (21)

A first electrode;
An N-type zinc oxide layer comprising nanorods of zinc oxide on the first electrode;
A P-type oxidized copper layer formed on the zinc oxide layer and including nano rods of copper oxide forming a heterojunction; And
And a second electrode formed on the copper oxide layer,
Wherein the zinc oxide layer has a single crystal structure,
Wherein the copper oxide layer has a polycrystalline structure. The method according to claim 1,
Wherein the nanoparticles of copper oxide have a length of 400 nm to 500 nm and a thickness of 50 nm to 100 nm. The method according to claim 1,
Wherein the thickness of the P-type copper oxide layer is in the range of 1 占 퐉 to 3 占 퐉. A first electrode;
An N-type zinc oxide layer comprising nanorods of zinc oxide on the first electrode;
A P-type oxidized copper layer formed on the zinc oxide layer and including nano rods of copper oxide forming a heterojunction; And
And a second electrode formed on the copper oxide layer,
Wherein the nanorods of the copper oxide have a monoclinic crystal structure that is first grown to a (111) plane. A first electrode;
An N-type zinc oxide layer comprising nanorods of zinc oxide on the first electrode;
A P-type oxidized copper layer formed on the zinc oxide layer and including nano rods of copper oxide forming a heterojunction; And
And a second electrode formed on the copper oxide layer,
Wherein the zinc oxide nanorods are hexagonal wurtzite crystal structures grown first with (002) planes. The method according to any one of claims 1, 4, and 5,
Wherein the nanorods of zinc oxide have a length of 500 nm to 700 nm. The method according to any one of claims 1, 4, and 5,
Wherein the zinc oxide layer has a thickness in the range of 400 nm to 800 nm. The method according to any one of claims 1, 4, and 5,
Wherein the first peak of the light emitting diode has electroluminescence characteristics in a range of 610 to 620 nm. The method according to any one of claims 1, 4, and 5,
Wherein the second peak of the light emitting diode has an electroluminescence characteristic in a range of 710 to 720 nm. The method according to any one of claims 1, 4, and 5,
Wherein the copper oxide layer has a carrier concentration of 9.64 x 10 ¹⁸ cm ^-3 or more. The method according to any one of claims 1, 4, and 5,
Wherein the light emitting diode has a constant rectification ratio of 10 ⁵ or more. The method according to any one of claims 1, 4, and 5,
Wherein the first electrode comprises gallium-zinc oxide. Forming a first electrode on the substrate;
Forming an N-type zinc oxide layer comprising nanorods of zinc oxide on the first electrode;
Forming a P-type oxidized copper layer containing nano-rods of copper oxide on the zinc oxide layer; And
And forming a second electrode on the copper oxide layer,
Wherein forming the zinc oxide layer comprises:
Forming a mold pattern on the substrate, the mold pattern having an opening region for exposing the first electrode; And
And forming the zinc oxide layer in the opening region of the mold pattern,
Wherein forming the copper oxide layer comprises:
Forming the copper oxide layer on the stamp substrate;
Contacting the surface of the stamp substrate on which the copper oxide layer is formed on a mold pattern on which the zinc oxide layer is formed to pressurize; And
And removing the stamp substrate to transfer a portion of the copper oxide layer onto the upper surface of the zinc oxide layer in the opening region of the mold pattern. 14. The method of claim 13,
Wherein the second electrode is formed on a stamp substrate on which the copper oxide layer is formed. 14. The method of claim 13,
Wherein forming the copper oxide layer comprises:
Dissolving copper nitrate trihydrate (Cu (NO ₃ ) ₂ .3H ₂ O) and potassium hydroxide (KOH) in a solvent to form a mixed solution;
Irradiating the mixed solution with a microwave to generate a reaction solution in which copper oxide powder is dispersed;
Drying the reaction solution to obtain the copper oxide powder; And
And coating the copper oxide powder on the stamp substrate. 16. The method of claim 15,
The step of obtaining the copper oxide powder comprises:
Washing the reaction solution before drying the reaction solution; And
And centrifuging the washed reaction solution to obtain the copper oxide powder. 16. The method of claim 15,
And adding ethylene glycol to the mixed solution. 14. The method of claim 13,
Wherein the mold pattern comprises a photoresist (PR) pattern. 14. The method of claim 13,
Wherein the step of forming the zinc oxide layer is performed by hydrothermal method. 14. The method of claim 13,
And the nano-rods of the zinc oxide are vertically grown on the first electrode. A first electrode;
A mold pattern defining an opening region for exposing the first electrode and formed of photoresist;
An N-type zinc oxide layer containing zinc oxide nanorods in the opening region of the mold pattern;
A p-type oxide comprising nano-rods of copper oxide in contact with said nano-rods of said n-type zinc oxide layer in said opening region of said mold pattern to form a heterostructure on said zinc oxide layer, layer; And
And a second electrode formed on the copper oxide layer.

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