KR20080062572A - A light emitting diode and manufacturing method thereof - Google Patents

Abstract

A light emitting diode and a method for manufacturing the same are provided to improve the efficiency of the light emitting diode by using SiC as a conductive substrate and ZnO as an N-type or P-type semiconductor device located at both sides of the conductive substrate. An N-type semiconductor material, a conductive substrate, and a P-type semiconductor material are laminated to configure a light emitting diode. The conductive substrate functions as an active layer. The N-type semiconductor material and the P-type semiconductor material are protruded to the outside so that a space for patterning a device is not required. Therefore, the overall area of the light emitting diode is used as an effective light emitting region. The conductive substrate has a high thermal conductivity so that heat generated in the light emitting diode easily transferred. Therefore, the lifetime of the light emitting diode is extended.

Description

Light emitting diode and manufacturing method thereof {A LIGHT EMITTING DIODE AND MANUFACTURING METHOD THEREOF}

1 is a conventional light emitting diode structure.

2 is an improved conventional light emitting diode structure.

3 is a structure of a light emitting diode according to an embodiment of the present invention.

4 is a graph showing electron concentration of a ZnO thin film.

5 is a scanning electron microscope (SEM) photograph of ZnO grown at 800 ° C.

6 is a SEM photograph of ZnO grown at room temperature.

7 is a SEM photograph of ZnO grown at 600 ° C.

8 is an AFM (Atomic Force Microscope) photograph of ZnO grown at room temperature.

9 is an AFM photograph of ZnO grown at 600 ° C.

10 is an AFM photograph of ZnO grown at 800 ° C.

11 is an AFM photograph of a ZnO thin film including a buffer layer.

12 is an X-ray diffraction (XRD) graph of a ZnO thin film including a buffer layer.

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly to a light emitting diode using a conductive substrate and a method of manufacturing the same.

At present, various light emitting diodes (LEDs) are commercially available. However, the performance of the light emitting diode substrate is still a problem. In the case of the sapphire substrate which is most used as a substrate of the light emitting diode, the difference between the lattice constant and the coefficient of thermal expansion with the epitaxial layer is large. Therefore, when an epitaxial layer is formed on a sapphire substrate, defects of a crystal structure tend to occur. In addition, since sapphire is not a heat transfer material, heat emission is not efficient, which shortens the lifespan of a light emitting diode. Therefore, it is necessary to develop a substrate that has a similar lattice constant to a substrate, an LED epi layer, and can effectively extract heat.

On the other hand, Figure 1 shows a light emitting diode using a conventional GaN-based material. As shown in Fig. 1, a conventional light emitting diode needs patterning to make a device. Therefore, there is a problem that the effective light emitting area is smaller than the size of the actual device.

To solve this problem, vertical light emitting diodes have been developed. 2 shows a vertical light emitting diode having a metal support layer. The vertical light emitting diode includes a metal support layer so that the entire device area becomes an effective light emitting area. However, such a structure has a problem in that the separation of the substrate and the epi layer is not easy.

In order to solve the above-mentioned problems, a light emitting diode having excellent thermal safety and a large effective light emitting area using a conductive substrate usable as an active layer and a method of manufacturing the same are provided.

A light emitting diode according to an embodiment of the present invention includes a structure in which a P-type semiconductor, a substrate, and an N-type semiconductor are sequentially stacked or vice versa. The substrate is a conductive substrate that acts as an active layer.

In this case, the conductive substrate may have a lattice structure, a lattice constant, and an energy bandgap similar to that of the P-type semiconductor and the N-type semiconductor. The conductive substrate also includes a SiC substrate.

In addition, the N-type semiconductor may include a ZnO semiconductor or a semiconductor doped with Z-type impurities in ZnO, the N-type impurities may be Al, Ga, In. The P-type semiconductor may include a semiconductor in which ZnO is doped with P-type impurities, and the P-type impurities may be N, P, As, or Sb.

Meanwhile, a method of manufacturing a light emitting diode according to an embodiment of the present invention includes: i) fabricating a conductive substrate, ii) depositing a buffer layer of 50 to 150 nm at room temperature on the substrate, and iii) the buffer layer. And depositing a P-type or N-type semiconductor material at 700 ° C. or higher.

The conductive substrate may be a SiC substrate, and the buffer layer, the P-type, and the N-type semiconductor material may be ZnO.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Like reference numerals in the present specification and drawings denote like elements.

3 illustrates a light emitting diode according to an embodiment of the present invention.

In the light emitting diode of FIG. 3, an N-type semiconductor material (or P-type semiconductor material), a substrate, and a P-type semiconductor material (or N-type semiconductor material) are sequentially stacked. At this time, the substrate uses a conductive substrate that can pass electricity.

Conductive substrates transfer electricity and heat well, unlike conventional sapphire substrates. Therefore, unlike conventional light emitting diodes in which a separate active layer exists between the P-type and N-type semiconductors, the substrate located in the center serves as an active layer.

In such a structure, since the N-type and P-type semiconductors protrude to the outside, no separate space is required for the patterning of the device. Therefore, the entire area of the diode can be used as the effective light emitting area. In addition, since the substrate having a good thermal conductivity is located in the center, heat generated in the diode is easily transferred. Therefore, the light emitting diode does not overheat, and the lifespan of the light emitting diode is also extended.

As the material of the conductive substrate, a lattice structure, a lattice constant, and an energy band gap of the material are the same as or similar to those of the P-type and N-type semiconductor materials to be deposited on both sides of the substrate. P-type or N-type semiconductors deposited on both sides of the substrate should be deposited epitaxially to increase the luminous efficiency of the light emitting device. When a material having a lattice structure, a lattice number, and an energy band gap similar to that of the substrate is deposited, an excellent epitaxial layer is formed. Therefore, a high efficiency light emitting diode can be manufactured using a substrate having a lattice structure, a constant, and an energy band gap similar to that of a P-type or N-type semiconductor.

GaN and ZnO include N-type or P-type semiconductor materials commonly used in light emitting diodes. Therefore, a SiC substrate having the same lattice structure and similar lattice constant and energy band gap is used as the conductive substrate.

As the N-type semiconductor material, ZnO-based materials are used as well as GaN-based materials, which are used in many cases.

4 is a graph showing electron concentration and mobility of electrons of a ZnO thin film to which impurities are not added. The data of FIG. 4 is obtained by depositing a thin film on a sapphire substrate while varying the pressure of oxygen and argon at a temperature of 800 ° C. by RF magnetron sputtering, and using a thin film heat-treated with Rapid Thermal Annealing (RTA) at 850 ° C. FIG. will be. As shown in FIG. 4, ZnO may be used as an N-type semiconductor without impurities. However, Al, Ga, and In which are N-type impurities may be further added thereto.

As the P-type semiconductor material, a material in which N, P, As, and Sb, which are P-type impurities, are added to a GaN-based material and a ZnO-based material, is used. ZnO is cheaper than conventional GaN, and has the same lattice constant and the same lattice constant as SiC, thus showing high efficiency in SiC substrates.

Hereinafter, a method of manufacturing a light emitting diode according to an embodiment of the present invention will be described.

First, a conductive substrate is produced. Any material that transfers electricity well and heat can be used, but SiC is recommended.

Next, a buffer layer having a thickness of about 50 to 150 nm is deposited on the fabricated substrate at room temperature. If the buffer layer is less than 50 nm, it is difficult to achieve the purpose of forming the buffer layer. On the other hand, when the buffer layer exceeds 150 nm, the buffer layer more than necessary is formed, and only the time required for the deposition becomes long. The deposition method is any method capable of thin film deposition such as sputtering, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), evaporation, and chemical vapor deposition (CVD). This can be Since the buffer layer is formed, deposition occurs well even at a high temperature, and adhesion between the deposited semiconductor layer and the substrate may be enhanced. The related experimental results will be described in detail later in the experimental examples.

Next, a P-type or N-type semiconductor material is deposited on the deposited buffer layer. As the deposition temperature is lower, the deposition is slower, so that a good shape lamination layer can be obtained, but the deposition time is required a lot. Therefore, it is deposited at 700 ℃ or more to increase the production efficiency. As the deposition method, all possible thin film deposition methods can be used as in the buffer deposition.

The buffer layer and the N or P-type semiconductor layer are laminated with the same material. Materials having the same or similar lattice structure, lattice constant, and energy bandgap as the materials of the prepared substrate are used. When the material of the substrate is SiC, materials of ZnO and GaN series are used.

Hereinafter, the present invention will be described in more detail through experimental examples. However, these experimental examples are for explaining the present invention, the present invention is not limited thereto.

Experimental Example

ZnO thin films were deposited on SiC substrates at 800 ° C using RF magnetron sputtering.

5 is a photograph showing the deposition result. As shown in FIG. 5, when the deposition was performed at a high temperature of about 800 ° C., the ZnO thin film did not grow well, and the adhesion between the thin film and the substrate was also poor. In order to compare the results, the temperature was lowered to deposit ZnO on SiC in the same manner.

6 and 7 are photographs measured by SEM (Scanning Electronic Microscope) of the result of lamination at room temperature and 600 ° C. It can be seen that both the thin films in FIGS. 6 and 7 are superior in shape and adhesiveness of the thin films as compared to the thin films of FIG. 5 laminated at 800 ° C.

8 to 10 are photographs of the same thin film of FIGS. 5 to 7 measured by atomic force microscope (AFM). 8 is a normal temperature, 9 is 600 ℃, Figure 10 is deposited at 800 ℃. As measured by the SEM, it can be seen from the results measured at 800 ° C. of FIG. 10 that the thin film did not grow properly.

Therefore, it can be seen that depositing a thin film at a low temperature can yield a better thin film. However, if the deposition temperature is low, more time is required for deposition. Therefore, in terms of manufacturing efficiency, it is better to deposit at a high temperature. Therefore, first, a ZnO layer of about 100 nm was grown at room temperature, and then a ZnO thin film was deposited using this layer as a buffer layer.

FIG. 11 is a photograph showing the results of growing the ZnO layer at 800 ° C. after growing the ZnO layer at about 100 nm at room temperature using AFM. When the buffer layer is present as shown in Figure 11, it can be seen that an excellent epitaxial thin film can be obtained.

FIG. 12 illustrates the orientation of the thin film of FIG. 11 using X-ray diffraction (XRD). Referring to FIG. 12, it can be seen that the resulting thin film was grown with constant crystallinity along the C axis. As such, since the thin film layer used as the N-type or P-type semiconductor grows epitaxially, a light emitting diode having high efficiency can be manufactured.

The light emitting diode according to the embodiment of the present invention includes a conductive substrate, and thus does not require a separate active layer. Therefore, the entire area of the diode can be used as a light emitting surface, which is highly efficient.

In addition, since the conductive substrate that transfers heat well is located in the center, it is possible to transfer heat generated from the diode well. Therefore, since the diode does not overheat, the use time of the light emitting diode is increased.

In addition, SiC is used as the conductive substrate, and ZnO is used as an element of an N-type or P-type semiconductor located on both sides of the substrate. Therefore, since the semiconductor layer is epitaxially deposited, the efficiency is higher.

On the other hand, in the method of manufacturing a light emitting diode according to an embodiment of the present invention, the buffer layer is deposited at room temperature, and the semiconductor layer is deposited at a high temperature thereon. Therefore, a well grown semiconductor layer is formed while shortening the deposition time.

Claims (10)

A P-type semiconductor, a substrate, a structure in which an N-type semiconductor is sequentially stacked, or vice versa, A light emitting diode, wherein the substrate is a conductive substrate acting as an active layer. The method of claim 1, Wherein said substrate has a lattice structure, lattice constant, and energy bandgap of material similar to said P-type semiconductor and N-type semiconductor. The method of claim 1, The conductive substrate comprises a SiC substrate. The method of claim 1, The N-type semiconductor includes a ZnO semiconductor or a semiconductor in which ZnO is doped with N-type impurities. The method of claim 4, wherein The n-type impurity is Al, Ga, In light emitting diode. The method of claim 1, The P-type semiconductor includes a semiconductor in which Z-type dopants are doped with ZnO. The method of claim 6, The p-type impurity is a light emitting diode of N, P, As, Sb. (a) manufacturing a conductive substrate, (b) depositing a buffer layer of 50 to 150 nm at room temperature on the substrate, and (c) depositing a P-type or N-type semiconductor material on the buffer layer at a temperature of 700 ° C. or higher, Method of manufacturing a light emitting diode comprising a. The method of claim 8, The conductive substrate is a method of manufacturing a light emitting diode comprising a SiC substrate. The method of claim 8, The buffer layer is a manufacturing method of a light emitting diode comprising a buffer layer made of ZnO.

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