KR20060112872A - Light emitting element - Google Patents

Abstract

A light emitting device is provided to improve a light emitting characteristic and a thermal characteristic by forming an electrode structure capable of minimizing a phenomenon that currents flowing to a p-n junction part is concentrated on an n-electrode by an equivalent circuit analysis. A first gallium nitride layer is formed on a substrate. A second gallium nitride layer is formed on the first gallium nitride layer. A transparent electrode layer(130) is formed all over the second gallium nitride layer. The edge region of the second gallium nitride layer is peeled to form a first electrode on a region to which the first gallium nitride layer is exposed. A second electrode includes a second electrode branch part and a second electrode end part. The second electrode branch part is formed on the second gallium nitride layer or the transparent electrode layer, extended toward the first electrode. The second electrode end part is formed at the end part of the second electrode branch part, running in parallel with the first electrode. An interval between the first electrode and the second electrode end part is smaller than 1/4 of the width of a light emitting device.

Description

Light emitting element {LIGHT EMITTING ELEMENT}

1 is a perspective view schematically showing a structure of a gallium nitride based light emitting diode.

FIG. 2 is an equivalent circuit diagram of the gallium nitride based light emitting diode shown in FIG. 1.

3A to 3C are diagrams for describing current densities according to positions of electrodes.

FIG. 4 is an equivalent circuit diagram of a resistance-light emitting diode for analyzing the two-dimensional planar electrode shown in FIG. 1.

5 is a plan view illustrating an electrode structure of a light emitting diode according to a comparative example.

FIG. 6A is a plan view illustrating the current distribution shown in FIG. 5, and FIG. 6B is a current density distribution of a cross section cut along the cutting line I ′ in FIG. 6A.

7A is a plan view illustrating an electrode structure of a light emitting diode according to a first exemplary embodiment of the present invention, and FIG. 7B is a cross-sectional view taken along the line II-II ′ of FIG. 7A.

8A and 8B illustrate current distributions of the light emitting diode of FIG. 7A.

9 is a plan view illustrating an electrode structure of a light emitting diode according to a second exemplary embodiment of the present invention.

10 is a plan view illustrating an electrode structure of a light emitting diode according to a third exemplary embodiment of the present invention.

FIG. 11A is a plan view illustrating an electrode structure of a light emitting diode according to a fourth exemplary embodiment of the present invention, and FIG. 11B is a plan view illustrating current density distribution flowing through a p-n junction surface in the electrode structure illustrated in FIG. 11A.

12A is a plan view illustrating an electrode structure of a light emitting diode according to a fifth embodiment of the present invention, and FIG. 12B is a plan view illustrating current density distribution flowing through a p-n junction surface in the electrode structure illustrated in FIG. 12A.

FIG. 13A is a plan view illustrating an electrode structure of a light emitting diode according to a sixth exemplary embodiment of the present invention, and FIG. 13B is a cross-sectional view taken along the line IV-IV ′ of FIG. 13A.

FIG. 14A shows the distribution of current flowing through the p-n junction surface in the electrode structure of FIG. 13A using an equivalent circuit, and FIG. 14B shows the current distribution in the V-V 'cross section in FIG. 14A.

15A is a plan view illustrating an electrode structure of a light emitting diode according to a seventh embodiment of the present invention, and FIG. 15B is a plan view illustrating current distribution in the electrode structure of FIG. 15A.

<Description of the symbols for the main parts of the drawings>

10, 110: substrate 11, 111: n-type gallium nitride layer

12: active layer 13, 113: p-type gallium nitride layer

142: p-electrode pad portion 144: p-electrode branch portion

146: p-electrode termination 20, 120, 220: n-electrode layer

21, 140, 240: p-electrode layer 22, 130, 230: p-type transparent electrode layer

524: n-electrode pad portion 526: n-electrode branch portion

528 n-electrode termination

The present invention relates to a light emitting device, and more particularly to a light emitting device having an electrode structure for inducing a uniform current distribution.

In general, a light emitting diode, which is a light emitting device, is spotlighted as a next-generation lighting that replaces an incandescent bulb or a fluorescent lamp. In particular, demand is expected to increase significantly as it is used for lighting of large area liquid crystal display devices having a long lifespan. However, for the high brightness of the light emitting diode, the nonuniformity of the current distribution has to be solved. In particular, a gallium nitride (GaN) -based light emitting diode used as a blue light source has a high nonuniformity in current distribution in comparison with other light emitting diodes.

If the current is not evenly distributed over the entire surface of the light emitting diode and is locally concentrated, not only the intensity of light emission at the surface of the device but also the uniformity of the wavelength is lowered.

Specifically, in the region where the concentration of electron-holes is relatively low, the intensity of light emission due to the electron-hole coupling is small and the wavelength is relatively long. On the other hand, in the region where the concentration of electron-holes is relatively high, the intensity of light emission by electron-hole coupling is large and the wavelength is shortened by band filling phenomenon.

In this case, light having a short wavelength generated in a region where the electron-hole concentration is relatively high is partially absorbed into a low current density region where the emission wavelength is relatively low, thereby lowering the internal quantum efficiency of the device.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a light emitting device having an electrode structure that induces a uniform current distribution to implement a high power, high brightness light emitting diode.

In order to realize the above object of the present invention, a light emitting device according to an embodiment includes a substrate, a first gallium nitride layer, a second gallium nitride layer, a transparent electrode layer, a first electrode, and a second electrode. The first gallium nitride layer is formed on the substrate. The second gallium nitride layer is formed on the first gallium nitride layer. The transparent electrode layer is entirely formed on the second gallium nitride layer. The first electrode is formed at an edge region of the first gallium nitride layer. The second electrode is formed parallel to the first electrode in the central region.

The first gallium nitride layer is an n-type gallium nitride layer, the second gallium nitride layer is characterized in that the p-type gallium nitride layer. The first gallium nitride layer is a p-type gallium nitride layer, the second gallium nitride layer is an n-type gallium nitride layer is another feature.

The distance between the first electrode and the second electrode is characterized in that less than 1/4 of the width of the light emitting device. The length of the second electrode is characterized in that more than 1/4 of the length of one side of the light emitting device. The width of the second electrode is characterized in that 5 ~ 20mm.

The first electrode may include a first electrode part formed in a closed loop shape at an edge region, and a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. Here, the first electrode pad part is formed in an area corresponding to a vertex of the first electrode part defining a quadrangular shape or in an area corresponding to one side.

The second electrode may include a second electrode pad portion having a circular shape in a central portion for wire bonding, a second electrode branch portion extending crosswise from the second electrode pad portion, and the second electrode branch portion in the second electrode branch portion. And a second electrode end portion extending in a direction parallel to the first electrode.

The second electrode may include a second electrode pad portion having a circular shape in a center portion for wire bonding, a second electrode branch portion extending in an x-shape from the second electrode pad portion, and the second electrode branch portion. And a second electrode end portion extending in a direction parallel to the first electrode.

The first electrode further includes a first electrode branch extending in an inward direction from a central portion of the first electrode portion, and a first electrode terminal portion extending from an end of the first electrode branch and parallel to the first electrode portion. do.

The first electrode may include a first electrode part formed in a c-shaped open loop shape at an edge region, and a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. do.

In this case, the second electrode is a second electrode pad portion formed in a circular shape at one central portion for wire bonding, a horizontal second electrode branch portion extending toward the 3 o'clock direction from the second electrode pad portion, and the horizontal agent And a vertical second electrode branch extending vertically from the end of the two electrode branch, and second electrode ends extending from the end of the vertical second electrode branch.

In order to realize the above object of the present invention, a light emitting device according to another embodiment includes a substrate, a first gallium nitride layer, a second gallium nitride layer, a transparent electrode layer, a first electrode, and a second electrode. The first gallium nitride layer is formed on the substrate. The second gallium nitride layer is formed on the first gallium nitride layer. The transparent electrode layer is entirely formed on the second gallium nitride layer. The first electrode is formed on an edge region of the second gallium nitride layer or the transparent electrode layer. The second electrode is formed on a region where the first gallium nitride layer is exposed by peeling a part of the second gallium nitride layer, and a second electrode branch portion extending toward the first electrode, and the second electrode branch. A second electrode end portion formed in parallel with the first electrode is provided at the secondary end portion.

According to such a light emitting device, a current structure flowing to the pn junction surface is provided by providing an electrode structure which minimizes a phenomenon in which a current flowing to a pn junction where the first gallium nitride layer and the second gallium nitride layer are in contact with the first electrode is minimized. It is possible to maintain a uniform and wide light emitting area.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the spirit of the present invention to those skilled in the art will fully convey. In the drawings, the width and thickness of wirings are enlarged in order to clearly express various layers (or films) and regions. As described in the overall description, it is described from an observer's point of view that, when a part such as a layer, a film, an area, or a plate is located above another part, this includes not only the part directly above the other part but also another part in the middle. . On the contrary, when a part is just above another part, it means that there is no other part in the middle.

1 is a perspective view schematically showing a structure of a gallium nitride based light emitting diode.

Referring to FIG. 1, a gallium nitride based light emitting diode includes a substrate 10, a gallium nitride buffer layer, an n-type gallium nitride layer 11, an active layer 12, and a p-type gallium nitride layer 13. ), n-electrode layer 20, p-electrode layer 21 and p-type transparent electrode layer 22. In operation, when current flows through the n-electrode layer 20 and the p-electrode layer 21, light is emitted while electron-hole recombination occurs in the active layer 12.

In order to grow the gallium nitride layer 11 on the substrate 10, a metal organic chemical vapor deposition (MOCVD) device is usually used. The substrate 10 is a sapphire substrate or a silicon carbide substrate.

First, a buffer layer (not shown) to help grow the gallium nitride layer 11 is formed on the substrate 10, and the n-type gallium nitride layer 11 and the active layer 12 are formed. And the p-type gallium nitride layer 13 are sequentially grown.

Typically, a light emitting diode includes an electrode layer formed on top of a p-type gallium nitride layer and a substrate connected to an n-type gallium nitride layer to flow current through a p-n junction. However, an electrode layer cannot be formed in the sapphire substrate 10 using sapphire as an insulator as a substrate. Therefore, an electrode layer must be directly formed on the n-type gallium nitride layer 11.

To this end, partial regions of the p-type gallium nitride layer 13, the active layer 12, and the n-type gallium nitride layer 11 in the region where the electrode layer is to be formed are removed, and the n-type gallium nitride layer 11 is exposed on the n-type gallium nitride layer 11. An electrode layer 20 is formed. Since the light is emitted from the p-n junction surface, the p-electrode layer 21 is formed at the corner of the p-type transparent electrode layer 22 so that light is not obscured by the electrode layer.

As such, when both the p-electrode layer 21 and the n-electrode layer 20 are positioned on the upper side, the p-electrode layer 21 and the n-electrode layer 20 are positioned in parallel with each other, compared to a general light emitting diode structure. The current distribution is not uniform.

In addition, the p-type gallium nitride layer 13 has a larger resistance than the n-type gallium nitride layer 11, and thus, it is more difficult for a current to flow uniformly through the p-type gallium nitride layer 13. In order to prevent this, a thin transparent electrode layer is formed on the entire upper surface of the p-type gallium nitride layer 13 so that current can be transferred to the entire surface of the p-type gallium nitride layer 13.

However, since the transparent electrode layer is formed of a very thin metal layer having a thickness of about 10 nm to allow light to be transmitted, the resistance is high. There is a limit to uniform current transfer to the entire surface of the p-type gallium nitride layer using the high resistance transparent electrode layer.

In addition, the contact resistance with the p-type gallium nitride layer 13 is also high, the light emitting diode characteristics are deteriorated and may cause heat generation. The thickness of the transparent electrode layer can be reduced to reduce the resistance, but in this case, the absorption and reflectance of the light by the electrode layer are increased, so that the light is difficult to be emitted to the outside.

Guo et al., Applied Physics Letters Vol. The papers presented on pages 78 and 3337, and Kim Hyun-soo, et al., Applied Physics Letters Vol. According to a paper published on pages 81 and 1326, a gallium nitride-based light emitting diode is interpreted as an equivalent circuit composed of a resistor and a light emitting diode as shown in FIG.

FIG. 2 is an equivalent circuit diagram of the gallium nitride based light emitting diode shown in FIG. 1. In FIG. 2, Rt is a resistance felt by a current flowing through the p-type transparent electrode layer 22, which is proportional to the specific resistance of the p-type transparent electrode layer 22 and inversely proportional to the thickness of the p-type transparent electrode layer 22. Rv is the resistance felt by the current passing through the pn junction and is proportional to the contact resistance between the p-type transparent electrode layer 22 and the p-type transparent electrode layer 22 and the p-type gallium nitride layer and the resistivity of the p-type gallium nitride layer. It is proportional to the thickness of the gallium nitride layer. Rn is a resistance felt by a current flowing through the n-type gallium nitride layer 11, and is proportional to the specific resistance of the n-type gallium nitride layer 11 and inversely proportional to the thickness of the n-type gallium nitride layer 11.

As shown in FIG. 2, two paths of current that can flow from the p-type transparent electrode layer 22 to the n-electrode layer 20 are classified into two paths.

That is, in the first path Path 1, a current flows through the p-type transparent electrode layer 22 to the n-electrode layer 20, and a current through the pn junction surface of the light emitting diode near the n-electrode layer 20. Is the path to reach the n-electrode layer 20 after flowing. In addition, the second path Path 2 has a current flowing along the n-type gallium nitride layer 11 after a current flows through the pn junction surface at a distance away from the n-electrode layer 20. 20) is the path to reach.

Typically, since the resistance of the n-type gallium nitride layer 11 is greater than that of the p-type transparent electrode layer 22, current does not easily flow through the n-type gallium nitride layer 11. That is, a current tends to flow in the first path Path 1 more than the second path Path 2. According to this analysis, the amount of current flowing to the p-n junction near the n-electrode layer 20 is greater than that far from the n-electrode layer 20.

According to the paper by Hyun-Soo Kim, the current density flowing from the n-electrode layer 20 to the p-n junction surface according to the distance x is expressed by Equation 1 below.

Where t _n is the thickness of the n-type gallium nitride layer, t _p is the thickness of the p-type gallium nitride layer, t _t is the thickness of the p-type transparent electrode layer, r _n is the resistivity of the n-type gallium nitride layer, r _p is the p-type The resistivity of the gallium nitride layer, r _t is the resistivity of the p-type transparent electrode layer, and r _c is the contact resistance between the p-type transparent electrode layer and the p-type gallium nitride layer.

If (r _n / t _n -r _t / t _t ) is greater than 0, x = where the n-electrode layer is located, and x increases as it moves away from the n-electrode layer. On the contrary, if (r _n / t _n -r _t / t _t ) is less than 0, x = where the p-electrode is located, and x increases as the distance from the p-electrode layer increases.

According to Equation 1, the current density decreases as the distance from the n-electrode layer 20 increases.

As such, a phenomenon in which the current is not evenly distributed over the entire surface of the light emitting diode and is locally concentrated is called a current crowding effect. This means that the intensity of light emission and the uniformity of wavelength are inferior on the surface of the device. That is, in the region where the concentration of electron-holes is relatively high, the intensity of light emission by electron-hole coupling is large and the wavelength is shortened by band filling phenomenon, and in the region where the concentration of electron-holes is relatively low, The intensity of light emission due to hole bonding is small and the wavelength is relatively long.

The short wavelength light generated in the region where the electron-hole concentration is relatively high is partially absorbed into the low current density region where the emission wavelength is relatively low, thereby lowering the internal quantum efficiency of the device.

On the other hand, the p-type transparent electrode layer 22 may be formed very thin in order to increase the light transmittance, but at this time the resistance of the p-type transparent electrode layer 22 may increase sharply to be larger than the resistance of the n-type gallium nitride layer. have.

In this case, on the contrary, the farther away from the n-electrode layer 20, the greater the amount of current flowing through the pn junction surface. If the resistance of the p-type transparent electrode layer 22 and the resistance of the n-type gallium nitride layer 11 are the same, the resistance of the current flowing through the first path (path 1) or the second path (path 2) may be determined. The resistance felt by the current flowing through it becomes equal. Therefore, the current flows uniformly over the entire region and the pruning phenomenon can be greatly improved. That is, the resistance of the p-type transparent electrode layer 22 and the resistance of the n-type gallium nitride layer 11 are equal to (r _n / t _n -r _t / t _t ) in Equation 1 above. It means to be. At this time, it can be seen that the current density is the same regardless of the position.

However, in order to make the resistance of the p-type transparent electrode layer 22 the same as that of the n-type gallium nitride layer 11, the thickness of the p-type transparent electrode layer 22 is inevitably limited. The resistance of the p-type transparent electrode layer 22 is proportional to the resistivity of the p-type transparent electrode layer 22 and inversely proportional to the thickness.

Since the specific resistance is difficult to easily change due to the intrinsic properties of the material, it is preferable to adjust the resistance of the p-type transparent electrode layer 22 by changing the thickness of the p-type transparent electrode layer 22. Accordingly, the current bleeding phenomenon may be improved by maintaining the thickness of the p-type transparent electrode layer 22 that is equal to the resistance of the n-type gallium nitride layer 11.

However, when the resistance of the p-type transparent electrode layer 22 is matched with the resistance of the n-type gallium nitride layer 11, the thickness of the p-type transparent electrode layer 22 becomes excessively thick, so that light is transferred to the p-type transparent electrode layer 22. As the thickness of the p-type transparent electrode layer 22 becomes too thin, the resistance of the p-type transparent electrode layer 22 may become too large to function properly as well as increase the resistance. The fever may also increase. Forming a p-type transparent electrode having an appropriate thickness with adequate light emission while sufficiently emitting light causes a difference in resistance between the p-type transparent electrode layer 22 and the resistance of the n-type gallium nitride layer 11, resulting in a severe current collapse. There is no choice but to.

Therefore, there is a need for a method capable of reducing current bleeding in the p-type transparent electrode layer 22 having an arbitrary thickness and resistance.

When the resistance of the p-type transparent electrode layer 22 is small, the amount of current that can flow through the light emitting diode can be increased and the heat generation can be reduced, so that the resistance of the p-type transparent electrode layer is preferably reduced. However, when the resistance of the p-type transparent electrode layer 22 is smaller than that of the n-type gallium nitride layer 11, current flows along the p-type transparent electrode layer 22 and then the pn junction surface around the n-electrode layer 20. Is more prone to flowing. That is, the closer the n-electrode layer 20 is, the more the current flows, and the farther away from the n-electrode layer 20, the less the current flows. However, if there is another n-electrode layer 20 near the n-electrode layer 20, current flows to this new n-electrode layer 20, so that the current distribution becomes more uniform than when there is only one n-electrode layer 20. The effect can be obtained. As the two n-electrode layers 20 are close to each other and maintain the same distance, the phenomenon in which the current distribution becomes uniform becomes more pronounced.

On the other hand, since the p-electrode layer 21 formed on the p-type transparent electrode layer 22 is much thinner than the p-type transparent electrode layer 22, the resistance is lower, so that the p-electrode layer 21 is lower than the p-type transparent electrode layer 22. Since the current is well transmitted through the p-electrode layer 21, a phenomenon in which the current is driven occurs. Therefore, even if the n-electrode layer 20 and the p-electrode layer 21 are formed at equal intervals close to each other, a phenomenon similar to a phenomenon in which the current distribution is uniform due to the adjacent n-electrode layers 20 are formed close to each other can be expected.

3A to 3C are diagrams for describing current densities according to positions of electrodes. In particular, FIG. 3A is a cross-sectional view of a first type of light emitting diode A in which the n-electrode layer 20 and the p-electrode layer 21 are far apart from each other, and FIG. 3B is an n-electrode layer 20 and the p-electrode layer ( 21 is a cross-sectional view of the light emitting diode B according to the second type arranged closely to each other, and FIG. 3C is a graph showing the current density flowing to the pn junction surface according to the position of the n-electrode layer and the p-electrode layer 21.

As shown in FIG. 3C, the first type of light emitting diode A has a relatively high current density around the n-electrode layer 20 and the p-electrode layer 21 and a relatively low current density in the central region. You can check it.

On the other hand, it can be seen that the second type of light emitting diode (B) has a very uniform current density compared to the first type of light emitting diode (A). Accordingly, an increase in the total amount of current can also be expected. That is, by properly arranging the n-electrode layer 20 and the p-electrode layer 21 formed on the light emitting diode, the current bleeding phenomenon can be improved regardless of the resistance of the p-type transparent electrode layer 22.

3A and 3B use an equivalent circuit in which several small resistors are arranged to calculate the current distribution. That is, in FIGS. 3A and 3B, although the electrodes of the light emitting diodes are arranged in two dimensions, the electrodes of the light emitting diodes are three-dimensionally planar, and thus three-dimensional as shown in FIG. 4 to make a more efficient electrode structure. The equivalent circuit can be extended in planar form.

FIG. 4 is an equivalent circuit diagram of a resistive light emitting diode for analyzing the two-dimensional planar electrode shown in FIG. 1.

In FIG. 4, Rt is the resistance of the p-type transparent electrode layer 22. At this time, the current flows through the Rt arranged in the two-dimensional plane. Rv is a contact resistance between the p-type transparent electrode layer 22 and the p-type gallium nitride layer and the resistance of the p-type gallium nitride layer. At this time, the current transmitted through the p-type transparent electrode layer 22 flows to the p-n junction surface through Rv. The light emitting diode exhibits a p-n junction surface. Rn arranged in a two-dimensional plane represents the resistance of the n-type gallium nitride layer. At this time, the current passing through the p-n junction surface flows through the n-type gallium nitride layer to the n-electrode layer.

Since the current droop phenomenon depends largely on the resistance component of each layer, the light emitting diode can be omitted in FIG. 4.

In Fig. 4, Rt is 30 ms, Rv is 10 ms, and Rn is 100 ms. Using Kirchhoff's voltage principle and current principle, the current flowing through each resistor can be obtained from FIG. 4. The current flowing through each Rv is the current density flowing through the p-n junction surface.

Comparative Example

5 is a plan view illustrating an electrode structure of a light emitting diode according to a comparative example. For convenience of description, the light emitting device described with reference to FIG. 1 is shown, and a detailed description thereof will be omitted.

FIG. 6A is a plan view illustrating the current distribution shown in FIG. 5, and FIG. 6B is a current density distribution of a cross section cut along the cutting line I ′ in FIG. 6A. In particular, FIG. 6A calculates a distribution of current flowing through the light emitting diode shown in FIG. 5 using the equivalent circuit of FIG. 4, and shows the result in a contour form. For convenience of explanation, the maximum value of the current density is normalized to 1. Therefore, the closer the minimum current value is to 1, the more uniform the current distribution.

As shown in FIGS. 6A and 6B, in the vicinity of the p-electrode layer 21, the current density is about 0.25, and gradually increases as it moves to the n-electrode layer 20, and becomes the maximum at the edge of the n-electrode layer 20. .

The minimum current is only 0.25, and the closer to the n-electrode layer 20, the higher the current density is. It can be seen that the current distribution is not uniform and the current bleeding phenomenon is severe. Accordingly, there is a disadvantage in that the intensity of light emission and the uniformity of wavelength are inferior in the surface of the device of the light emitting diode.

<Example 1>

7A is a plan view illustrating an electrode structure of a light emitting diode according to a first exemplary embodiment of the present invention, and FIG. 7B is a cross-sectional view taken along the line II-II ′ of FIG. 7A.

7A and 7B, the gallium nitride based light emitting diode 100 according to the first embodiment includes a substrate 110, an n-type gallium nitride layer 111, a p-type gallium nitride layer 113, and an n-electrode layer. 120, a p-type transparent electrode layer 130, and a p-electrode layer 140. In operation, when current flows through the n-electrode layer 120 and the p-electrode layer 140, light is emitted while electron-hole recombination occurs in an active layer (not shown). In the drawing, a gallium nitride buffer layer interposed between the substrate 110 and the n-type gallium nitride layer 111 and an active layer interposed between the n-type gallium nitride layer 111 and the p-type gallium nitride layer 113. The illustration of the (active layer) is omitted.

The n-electrode layer 120 includes an n-electrode portion 122 formed in a closed loop shape at an edge region and an n-electrode pad portion 124 formed in a circular shape for wire bonding. The n-electrode pad part 124 is formed in one of the vertex areas of the light emitting diode 100 defining a quadrangular shape.

The p-electrode layer 140 is thickly formed in the center of the light emitting diode 100. The p-electrode layer 140 may include a p-electrode pad part 142 having a circular shape in a center portion for wire bonding, and four p-electrode branch parts extending in a cross shape from the p-electrode pad part 142 ( 144, a p-electrode end portion 146 extending in a direction parallel to the n-electrode layer 120 in the p-electrode branch portions 144. Two p-electrode branch portions 144 adjacent to the p-electrode pad portion 142 and the p-electrode termination portion 146 connected thereto define an L shape and an inverted-L shape, respectively. Two p-electrode branch portions 144 adjacent to the p-electrode pad portion 142 and the p-electrode termination portion 146 connected thereto define a T-shape.

Since there is no pn junction surface in the region where the n-electrode layer 120 is formed, no light is emitted, and there is a pn junction surface in the region where the p-electrode layer 140 is formed, but is covered by the thick p-electrode layer 140. No light is emitted That is, light may be emitted upward only to a region where the p-type transparent electrode 130 is formed. Therefore, the area of the p-type transparent electrode 130 should be increased.

The length L1 of one side of the light emitting diode 100 is 300 mm to 500 mm, and the shape is square or rectangular. The n-electrode portion 122 and the p-electrode branch portion 144 have a width of the light p-electrode end portion 146 of 5 mm to 20 mm, and the n-electrode pad 124 and the p-electrode pad 142. ) Diameter ranges from 80 mm to 100 mm.

The distance D1 between the p-electrode end portion 146 and the n-electrode portion 122 formed in parallel with the n-electrode portion 122 is equal to 1 / length of one side length L1 of the light emitting diode 100. The length L2 of the p-electrode end portion 146 which is less than 4 and formed in parallel with the n-electrode portion 122 is equal to or greater than 1/4 of the length of one side of the light emitting diode 100.

Typically, a light emitting diode having two n-electrodes arranged at equal intervals has a higher current uniformity than a light emitting diode having one n-electrode layer.

However, as shown in FIG. 7A, the n-electrode part 122 is formed in a closed loop along the edge region of the light emitting diode 100, and another n-electrode layer is formed on the side facing the n-electrode layer on either side. Because of its shape, two n-electrode layers are arranged at equal intervals. Accordingly, current uniformity can be increased, and the distribution of current is also more symmetrical than the electrode structure of a general light emitting diode.

In addition, since the n-electrode layer 120 and the p-electrode layer 140 are formed in close proximity and parallel to each other, the n-electrode layer 120 and the p-electrode layer 140 do not have the p-electrode end portion 146. ) Has the effect of reducing the distance between. That is, since the resistance felt when the current flows from the p-electrode layer 140 to the n-electrode layer 120 is smaller, the overall resistance is reduced, thereby improving the electrical and thermal characteristics of the light emitting diode.

8A and 8B illustrate current distributions of the light emitting diode of FIG. 7A. In particular, FIG. 8A is a plan view showing the distribution of current density in the light emitting diode shown in FIG. 7A using the equivalent circuit of FIG. 4 in the form of contour lines, and FIG. 8B is a cross-sectional view taken along line III-III 'of FIG. 8A. to be.

As shown in FIGS. 7A to 8B, the current density distribution of the light emitting diode 100 according to the first embodiment is symmetrical and uniform. That is, the current density of the edge region of the light emitting diode approaches 1, which is a normalized value, and the current density gradually decreases to 0.939, 0.903, 0.855, 0.806, 0.758, and 0.697 as it moves toward the center of the light emitting diode. The contour of the current density in the edge area is rectangular, and the contour of the current density is circular in shape as it moves toward the center.

On the other hand, although the current distribution is uniform, the emission area may be reduced by increasing the area of the n-electrode layer 120. Light is not generated in the region where the n-electrode layer 120 is formed by the member of the p-n junction surface. In addition, although the p-n junction surface is present in the region where the p-electrode layer 140 is formed, light may not be emitted upward due to the thick p-electrode layer 140.

Therefore, in order to calculate the actual light emission amount (total light emission efficiency S), the current value calculated through the equivalent circuit was normalized and added together. If the current is uniform, the normalized current value will be equal to 1 throughout the light emitting diode, so the total amount of current will be the light emitting diode total area (A).

However, since the actual current differs depending on the position of the surface of the light emitting diode, the total amount of current becomes a value obtained by multiplying the area of each portion by the current density of each portion of the light emitting diode. Therefore, when the current distribution is uneven, when the total current amount and the current distribution are perfectly uniform, the total luminous efficiency S is defined by the following equation (3).

Here, the region in which the n-electrode layer and the p-electrode layer are formed is excluded.

When the total light emission efficiency S is calculated in the light emitting diode according to the comparative example illustrated in FIG. 5 using Equation 2, 36.5%. However, when the total light emitting efficiency S is calculated in the light emitting diode according to the first embodiment shown in FIG. 7A, it reaches 67.4%.

<Example 2>

9 is a plan view illustrating an electrode structure of a light emitting diode according to a second exemplary embodiment of the present invention.

Referring to FIG. 9, the gallium nitride based light emitting diode 200 according to the second embodiment includes a substrate (not shown), an n-type gallium nitride layer (not shown), a p-type gallium nitride layer (not shown), and an n-electrode layer. 220, a p-type transparent electrode layer 230, and a p-electrode layer 240. In operation, when current flows through the n-electrode layer 220 and the p-electrode layer 240, light is emitted while electron-hole recombination occurs in an active layer (not shown).

The n-electrode layer 220 includes an n-electrode portion 222 formed in a closed loop shape at an edge region and an n-electrode pad portion 224 formed in a circular shape for wire bonding. The n-electrode pad part 224 is formed in one of the vertex areas of the light emitting diode 200 defining a quadrangular shape.

The p-electrode layer 240 is thickly formed in the center of the light emitting diode 200. The p-electrode layer 240 is a p-electrode pad part 242 formed in a circular shape at the center for wire bonding, and 3 extending in the x-direction (or diagonal direction) from the p-electrode pad part 242. P-electrode branches 244, p-electrode branches 244 and p-electrode terminations 246 extending in a direction parallel to the n-electrode 220. In particular, the p-electrode branch portions 244 are formed only toward the vertex region where the n-electrode pad portion 224 is not formed.

The p-electrode end portion 246 is formed while defining the L shape at the p-electrode branch portion 244. Accordingly, the p-electrode branch portion 244 and the p-electrode end portion 246 define an arrow shape.

Since there is no pn junction surface in the region where the n-electrode layer 220 is formed, no light is emitted, and there is a pn junction surface in the region where the p-electrode layer 240 is formed, but is covered by a thick p-electrode layer 240. No light is emitted That is, light may be emitted upward only to a region where the p-type transparent electrode layer 230 is formed. Therefore, the area of the p-type transparent electrode layer 230 should be increased.

The distance between the p-electrode end portion 246 and the n-electrode portion 222 formed parallel to the n-electrode portion 222 is less than 1/4 of the length of one side of the light emitting diode 200, and the n The length of the p-electrode end portion 246 formed parallel to the electrode portion 222 is equal to or greater than 1/8 the length of one side of the light emitting diode 200.

The length of one side of the light emitting diode 200 is 300 mm to 500 mm, the shape is square or rectangular. The widths of the p-electrode termination part 246, the p-electrode branch part 244, and the n-electrode layer 220 are 5 mm to 20 mm, and the p-electrode pad 242 and the n-electrode pad 224 may be formed. The diameter is 80 mm to 100 mm.

<Example 3>

10 is a plan view illustrating an electrode structure of a light emitting diode according to a third exemplary embodiment of the present invention.

Referring to FIG. 10, the gallium nitride based light emitting diode 300 according to the third embodiment includes a substrate (not shown), an n-type gallium nitride layer (not shown), a p-type gallium nitride layer (not shown), and an n-electrode layer. And a p-type transparent electrode layer 330 and a p-electrode layer 340. In operation, when current flows through the n-electrode layer 320 and the p-electrode layer 330, light is emitted while electron-hole recombination occurs in an active layer (not shown). In the drawing, a gallium nitride buffer layer interposed between the substrate 310 and the n-type gallium nitride layer 311, and an active layer interposed between the n-type gallium nitride layer 311 and the p-type gallium nitride layer 313. The illustration of the (active layer) is omitted.

The n-electrode layer 320 includes an n-electrode portion 322 formed in a closed loop shape at an edge region and an n-electrode pad portion 324 formed in a circular shape for wire bonding. The n-electrode pad portion 324 is formed in a region corresponding to one side of the sides of the light emitting diode 300 defining a quadrangular shape.

The p-electrode layer 340 is thickly formed in the center of the light emitting diode 300. The p-electrode layer 340 has a p-electrode pad portion 342 formed in a circular shape in a center portion for wire bonding, and three p-electrode branch portions extending in a cross shape from the p-electrode pad portion 342 ( 344, a p-electrode end portion 346 extending from the p-electrode branch portions 344 in a direction parallel to the n-electrode layer 320. The p-electrode branch 344 and the p-electrode end 346 define a T-shape.

<Example 4>

FIG. 11A is a plan view illustrating an electrode structure of a light emitting diode according to a fourth exemplary embodiment of the present invention, and FIG. 11B is a plan view illustrating current density distribution flowing through a p-n junction surface in the electrode structure illustrated in FIG. 11A.

Referring to FIG. 11A, the gallium nitride-based light emitting diode 400 according to the fourth embodiment of the present invention has a gallium nitride-based light emitting diode 200 having a substrate (not shown), an n-type gallium nitride layer (not shown), and a p-type gallium nitride. A layer (not shown), an n-electrode layer 420, a p-type transparent electrode layer 430, and a p-electrode layer 440. In operation, when current flows through the n-electrode layer 420 and the p-electrode layer 440, light is emitted while electron-hole recombination occurs in an active layer (not shown).

The n-electrode layer 420 includes an n-electrode portion 422 formed in a closed loop shape at an edge region and an n-electrode pad portion 424 formed in a circular shape for wire bonding. The n-electrode pad part 424 is formed at a vertex region of the light emitting diode 400 defining a quadrangular shape.

The p-electrode layer 440 is thickly formed in the center of the light emitting diode 400. The p-electrode layer 440 may include a p-electrode pad portion 442 having a circular shape in a central portion for wire bonding, and four p-electrode branch portions extending in a cross shape from the p-electrode pad portion 442. 444), the p-electrode branch portion 444 extends in a direction parallel to the n-electrode layer 420 and includes a p-electrode end portion 446 formed in a closed loop shape.

As described above, the light emitting diode 400 according to the fourth exemplary embodiment of the present invention has a p-electrode end portion 446 having a closed loop shape, and a distance between the p-electrode end portion 446 and the n-electrode portion 422. Is very close.

As shown in FIG. 11B, the current density distribution of the light emitting diode 400 according to the fourth embodiment is symmetrical and uniform. That is, the current density of the edge region of the light emitting diode approaches 1, which is a normalized value, and the current density gradually decreases to 0.921, 0.868, 0.8828 0.802, 0.762, 0.709 and 0.67 as it moves toward the center of the light emitting diode. The contour of the current density in the edge area is rectangular, and the contour of the current density is circular in shape as it moves toward the center. That is, it can be seen that the electrode structure of the light emitting diode shown in FIG. 7 is similar to the current density distribution flowing through the p-n junction surface. Here, the calculated total luminous efficiency S of the light emitting diode according to the fourth embodiment of the present invention is 60.1%.

Example 5

12A is a plan view illustrating an electrode structure of a light emitting diode according to a fifth embodiment of the present invention, and FIG. 12B is a plan view illustrating current density distribution flowing through a p-n junction surface in the electrode structure illustrated in FIG. 12A.

Referring to FIG. 12A, a gallium nitride-based light emitting diode 500 according to a fifth embodiment includes a substrate (not shown), an n-type gallium nitride layer (not shown), a p-type gallium nitride layer (not shown), and an n-electrode layer. 520, a p-type transparent electrode layer 530, and a p-electrode layer 540. In operation, when current flows through the n-electrode layer 520 and the p-electrode layer 540, light is emitted while electron-hole recombination occurs in an active layer (not shown). In the drawing, a gallium nitride buffer layer interposed between the substrate 510 and the n-type gallium nitride layer 511 and an active layer interposed between the n-type gallium nitride layer 511 and the p-type gallium nitride layer 513. The illustration of the (active layer) is omitted.

The n-electrode layer 520 may include an n-electrode portion 522 formed in a closed loop at an edge region, an n-electrode pad portion 524 formed in a circular shape for wire bonding, and an n-electrode portion 522. An n-electrode branch 526 extending inward from the center portion and an n-electrode end portion 528 extending from the end of the n-electrode branch 526 and parallel to the n-electrode portion 522. do. The n-electrode pad part 524 is formed at a vertex region of the light emitting diode 500 that defines a quadrangular shape. Each of the n-electrode branch portions 526 is formed at 12 o'clock and 6 o'clock from an observer's point of view.

The p-electrode layer 540 is thickly formed in the center of the light emitting diode 500. The p-electrode layer 540 extends toward the 3 o'clock and 9 o'clock directions of the p-electrode pad part 542 and the p-electrode pad part 542 formed in a circular shape at the center for wire bonding, respectively. P-electrode branches 544, and p-electrode terminations 546 extending in a direction parallel to the n-electrode layer 520 in the p-electrode branches 544.

As such, the n-electrode branch may be formed in the center region of the n-electrode layer formed along the edge of the light emitting diode to make the current density distribution more uniform.

As shown in FIG. 12B, the current density distribution of the light emitting diode 500 according to the fifth embodiment is symmetrical and uniform. That is, the current density of the edge region of the light emitting diode 500, that is, the region close to the n-electrode layer 520 is closer to the normalized value of 1, and moves toward the center of the light emitting diode, that is, the n-electrode layer 520. Farther away from), the current density decreases sequentially to 0.9476, 0.908, 0.87, and 0.809.

The minimum value of normalized current is 0.81, and the normalized current value is close to 1 over the entire area. This means that the current distribution is very uniform. Here, the calculated total luminous efficiency S of the light emitting diode is 68.1%.

In the above, the current density distribution was made uniform by making the n-electrode layer form a closed loop along the edge region of the light emitting diode. However, those skilled in the art may make the current density distribution uniform by allowing the p-electrode layer to form a closed loop along the edge region of the light emitting diode. In this case, the n-electrode pad is located at the center of the light emitting diode, and a branched n-electrode layer is formed in the cross direction from the n-electrode pad. A strip-shaped n-electrode layer is formed in parallel with the electrode layer.

<Example 6>

FIG. 13A is a plan view illustrating an electrode structure of a light emitting diode according to a sixth exemplary embodiment of the present invention, and FIG. 13B is a cross-sectional view taken along the line IV-IV ′ of FIG. 13A. In particular, the p-electrode layer forms a closed loop along the edge region of the light emitting diode, and the n-electrode layer is formed in the center of the light emitting diode.

13A and 13B, the gallium nitride based light emitting diode 600 according to the sixth embodiment includes a substrate 610, an n-type gallium nitride layer 611, a p-type gallium nitride layer 613, and an n-electrode layer. 620, a p-type transparent electrode layer 630, and a p-electrode layer 640. In operation, when current flows through the n-electrode layer 620 and the p-electrode layer 640, light is emitted while electron-hole recombination occurs in an active layer (not shown). In the drawing, a gallium nitride buffer layer interposed between the substrate 610 and the n-type gallium nitride layer 611 and an active layer interposed between the n-type gallium nitride layer 611 and the p-type gallium nitride layer 613. The illustration of the (active layer) is omitted.

The n-electrode layer 620 is thickly formed in the center of the light emitting diode 600. The n-electrode layer 620 has an n-electrode pad portion 622 formed in a circular shape in a center portion for wire bonding, and four n-electrode branch portions extending in a cross shape from the n-electrode pad portion 622 ( 624, an n-electrode end portion 626 extending in a direction parallel to the p-electrode layer 640 at the n-electrode branch portions 624.

The p-electrode layer 640 includes a p-electrode 642 formed in a closed loop shape at an edge region and a p-electrode pad 644 formed in a circular shape for wire bonding. The p-electrode portion 642 is formed in parallel with the n-electrode end portion 626. The p-electrode pad part 644 is formed at a vertex region of the light emitting diode 600 defining a quadrangular shape.

The closer the distance is between two adjacent n-electrode layers, the more uniform the distribution of current density. When the n-electrode layer is formed in a closed loop shape along the edge region of the light emitting diode, the average distance between adjacent n-electrode layers becomes the length of one side of the light emitting diode.

However, as shown in FIG. 13A, when the n-electrode layer is formed at the center of the light emitting diode and the n-electrode branches are formed in the cross direction, the average distance between adjacent n-electrode layers is equal to one side length of the light emitting diode. In half, the distribution of current density becomes more uniform.

FIG. 14A shows the distribution of current flowing through the p-n junction surface in the electrode structure of FIG. 13A using an equivalent circuit, and FIG. 14B shows the current distribution in the V-V 'cross section in FIG. 14A.

As shown in FIG. 14B, the current density distribution of the light emitting diode 600 according to the sixth embodiment is symmetrical and uniform. That is, the current density of the center portion of the light emitting diode 600, that is, the region close to the n-electrode layer 620 is closer to the normalized value 1, and moves toward the edge region of the light emitting diode, that is, the n-electrode layer 620. Farther away from) decreases the current density sequentially to 0.939, 0.893, 0.831, 0.755, and 0.678. Here, the calculated total luminous efficiency S of the light emitting diode is 65.4%.

<Example 7>

15A is a plan view illustrating an electrode structure of a light emitting diode according to a seventh embodiment of the present invention, and FIG. 15B is a plan view illustrating current distribution in the electrode structure of FIG. 15A. In particular, the n-electrode is formed inside the light emitting diode, and the n-electrode pad portion is formed in the edge region of the light emitting diode.

Referring to FIG. 15A, a gallium nitride based light emitting diode 700 according to a seventh embodiment may include a substrate (not shown), an n-type gallium nitride layer (not shown), a p-type gallium nitride layer (not shown), and an n-electrode layer. 720, a p-type transparent electrode layer 730 and a p-electrode layer 740. In operation, when a current flows through the n-electrode layer 720 and the p-electrode layer 740, light is emitted while electron-hole recombination occurs in an active layer (not shown). In the drawings, gallium nitride buffer layers and active layers are omitted.

The n-electrode layer 720 is formed thick in the center of the light emitting diode 700. The n-electrode layer 720 has an n-electrode pad part 722 formed in a circular shape at a left center portion for wire bonding, and a horizontal n-electrode branch extending toward the 3 o'clock direction from the n-electrode pad part 722. A portion 724, a vertical n-electrode branch 726 extending vertically at the end of the horizontal n-electrode branch 724, and an n− extending at the end of the vertical n-electrode branch 726, respectively. Electrode terminations 728.

The p-electrode layer 740 includes a p-electrode portion 742 formed in a c-shape at an edge region and a p-electrode pad portion 744 formed in a circular shape for wire bonding. The p-electrode portion 742 is formed in parallel with the n-electrode end portion 728. The p-electrode pad portion 744 is formed in a region corresponding to the middle of three sides of the light emitting diode 600 defining the c-shape.

As such, since the n-electrode pad portion 722 and the p-electrode pad portion 744 are spaced apart from each other, wire bonding is easy, and since the wire does not cover the upper portion of the light emitting diode 700, the emitted light may be blocked. Can be.

As shown in FIG. 15B, the current density distribution of the light emitting diode 700 according to the seventh embodiment is symmetrical and uniform. Here, the calculated total luminous efficiency S of the light emitting diode is 66.7%.

As described above, by providing an electrode structure that minimizes the phenomenon that the current flowing to the p-n junction is concentrated on the n-electrode by an equivalent circuit analysis, it is possible to improve the light emission characteristics and thermal characteristics of the light emitting diode.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (27)

Board; A first gallium nitride layer formed on the substrate; A second gallium nitride layer formed on the first gallium nitride layer; A transparent electrode layer formed entirely on the second gallium nitride layer; A first electrode formed on the region where the first gallium nitride layer is exposed by removing an edge region of the second gallium nitride layer; And A second electrode branch portion extending toward the first electrode on the second gallium nitride layer or the transparent electrode layer, and a second electrode terminal portion formed at the end of the second electrode branch portion in parallel with the first electrode; A light emitting device comprising two electrodes. The light emitting device according to claim 1, wherein the first gallium nitride layer is an n-type gallium nitride layer, and the second gallium nitride layer is a p-type gallium nitride layer. The light emitting device according to claim 1, wherein the first gallium nitride layer is a p-type gallium nitride layer, and the second gallium nitride layer is an n-type gallium nitride layer. The light emitting device of claim 1, wherein a distance between the first electrode and the second electrode terminal portion is less than 1/4 of a width of the light emitting device. The light emitting device according to claim 1, wherein the length of the second electrode terminal portion is at least 1/4 of a length of one side of the light emitting device. The light emitting device of claim 1, wherein a width of the second electrode branch portion and the terminal portion is 5 to 20 mm. The method of claim 1, wherein the first electrode, A first electrode part formed in a closed loop shape in an edge region; And And a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. The light emitting device of claim 7, wherein the first electrode pad part is formed in an area corresponding to a vertex of the first electrode part or a region corresponding to one side of the first electrode part defining a square shape. The method of claim 1, wherein the second electrode, A second electrode pad portion formed in a circular shape at the center portion for wire bonding; A second electrode branch part extending in a cross shape from the second electrode pad part; And And a second electrode terminal portion extending from the second electrode branch portion in a direction parallel to the first electrode. The method of claim 1, wherein the second electrode, A second electrode pad portion formed in a circular shape at the center portion for wire bonding; A second electrode branch portion extending from the second electrode pad portion in an x-shaped shape; And And a second electrode terminal portion extending from the second electrode branch portion in a direction parallel to the first electrode. The light emitting device of claim 9, wherein the second electrode end portions are connected to each other to define a closed loop. The light emitting device of claim 10, wherein the second electrode end portions are connected to each other to define a closed loop. The method of claim 7, wherein the first electrode, A first electrode branch portion extending in an inward direction from a center portion of the first electrode portion; And And a first electrode end portion extending from the end of the first electrode branch portion and parallel to the first electrode portion. The method of claim 1, wherein the first electrode, A first electrode portion formed in a c-shaped open loop shape in an edge region; And And a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. The method of claim 13, wherein the second electrode, A second electrode pad part formed in a circular shape at one central portion for wire bonding; A horizontal second electrode branch part extending toward the 3 o'clock direction from the second electrode pad part; A vertical second electrode branch extending vertically from an end of the horizontal second electrode branch; And And second electrode end portions extending horizontally from the end of the vertical second electrode branch portion, respectively. Board; A first gallium nitride layer formed on the substrate; A second gallium nitride layer formed on the first gallium nitride layer; A transparent electrode layer formed entirely on the second gallium nitride layer; A first electrode formed on an edge region of the second gallium nitride layer or the transparent electrode layer; And A second electrode branch portion formed on the exposed portion of the second gallium nitride layer by exposing a portion of the second gallium nitride layer and extending toward the first electrode, and at the end of the second electrode branch portion; And a second electrode having a second electrode end formed in parallel with the first electrode. The light emitting device according to claim 16, wherein the first gallium nitride layer is an n-type gallium nitride layer, and the second gallium nitride layer is a p-type gallium nitride layer. The light emitting device according to claim 16, wherein the first gallium nitride layer is a p-type gallium nitride layer, and the second gallium nitride layer is an n-type gallium nitride layer. 17. The light emitting device of claim 16, wherein a distance between the first electrode and the second electrode terminal portion is less than 1/4 of a width of the light emitting device. The light emitting device according to claim 16, wherein a length of the second electrode terminal portion is at least 1/4 of a length of one side of the light emitting device. The light emitting device of claim 16, wherein a width of the second electrode branch portion and the terminal portion is 5 to 20 mm. The method of claim 16, wherein the first electrode, A first electrode part formed in a closed loop shape in an edge region; And And a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. The light emitting device of claim 22, wherein the first electrode pad part is formed in an area corresponding to a vertex of the first electrode part or a region corresponding to one side of the first electrode part defining a quadrangular shape. The method of claim 16, wherein the second electrode, A second electrode pad portion formed in a circular shape at the center portion for wire bonding; A second electrode branch part extending in a cross shape from the second electrode pad part; And And a second electrode terminal portion extending from the second electrode branch portion in a direction parallel to the first electrode. The method of claim 16, wherein the second electrode, A second electrode pad portion formed in a circular shape at the center portion for wire bonding; A second electrode branch portion extending from the second electrode pad portion in an x-shaped shape; And And a second electrode terminal portion extending from the second electrode branch portion in a direction parallel to the first electrode. The method of claim 22, wherein the first electrode, A first electrode portion formed in a c-shaped open loop shape in an edge region; And And a first electrode pad part connected to the first electrode part and formed in a circular shape for wire bonding. The method of claim 26, wherein the second electrode, A second electrode pad part formed in a circular shape at one central portion for wire bonding; A horizontal second electrode branch part extending toward the 3 o'clock direction from the second electrode pad part; A vertical second electrode branch extending vertically from an end of the horizontal second electrode branch; And And second electrode end portions extending horizontally from each end of the vertical second electrode branch portion.

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