KR101024359B1 - Semiconductor light emitting device - Google Patents

Abstract

The present invention relates to a semiconductor light emitting device, comprising n-type and p-type semiconductor layers formed on a substrate, an active layer formed therebetween, and n-type and p-type pad electrodes formed on each of the n-type and p-type semiconductor layers. A semiconductor light emitting device, comprising: an electrical connection with the p-type pad electrode and extending in a longitudinal direction in an area opposite to the n-type pad electrode with respect to a vertical line between the n-type and p-type pad electrodes with respect to a center connection line; A semiconductor light emitting device further comprising one or more branch electrodes is disclosed.

Semiconductor light emitting device, pad electrode

Description

Semiconductor Light Emitting Device {SEMICONDUCTOR LIGHT EMITTING DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device having a remarkably improved pad electrode structure.

In general, nitride-based light emitting devices have a structure in which a low temperature buffer layer and an undoped layer are formed on a substrate, and nitride layers are formed thereon. FIG. 1A is a schematic plan view of a general light emitting device, and FIG. 1B is a cross-sectional view thereof seen from broken line A-A 'of FIG. 1A.

Referring to FIG. 1B, the structure of a general light emitting device 1 will be schematically described. First, a low temperature buffer layer 3, an N-type nitride semiconductor layer 4, an active layer 6, and a light emitting region P are disposed on an upper portion of a substrate 2. The type nitride semiconductor layer 7 and the P-type electrode 8 are sequentially arranged. In this case, the low temperature buffer layer 3 may be omitted to prevent the occurrence of crystal defects due to lattice mismatch between the substrate 2 and the N-type nitride semiconductor layer 4. The P-type pad electrode 9 is disposed on the P-type electrode 8, and the N-type pad electrode 5 is disposed on the N-type nitride semiconductor layer 4, respectively.

In such a light emitting device 1, electrons are supplied from the N-type nitride semiconductor layer 4 and holes are supplied from the P-type nitride semiconductor layer 7. However, in general, since the electrical conductivity of the P-type nitride is very low, the P-type nitride semiconductor layer as shown in FIGS. 1A and 1B in order to uniformly flow a driving current to the entire surface thereof without obstructing the light emission of the device 1. (7) is arranged on the uppermost layer of the element 1, and a P-type electrode 8 serving as a transparent electrode is formed thereon. The P-type electrode 8 is generally made of a metal such as Ni, Au, Pd, Pt, or a conductive oxide film such as ITO (Indium / Tin / Oxide), and especially Ni / Au or Ni having a thin thickness to increase light transmittance. Since it is made of ITO, it has a high resistance component. Therefore, as shown in FIG. 1A, as the distance d between the P-type pad electrode 9 and the N-type pad electrode 5 increases, the operating voltage of the light emitting device 1 increases, and an example thereof is illustrated in FIG. 2A. And 2b. 2A shows the operating voltage ((V): y1 axis) and current of the device according to the distance d between the P-type pad electrode 9 and the N-type pad electrode 5 in the light emitting device having a size of 600 × 250 μm ^2. It is a graph of the change of the density density (current density STD (A / cm ² ): y2 axis), which means that the smaller the current density dispersion value, the better the current uniformity. In addition, FIG. 2B is a light power distribution photograph when the distance d between the electrodes is 270 μm, and since the light output is proportional to the current density, this light output distribution means a current density distribution.

Referring to FIG. 2A, it can be seen that the smaller the distance d between the pad electrodes is, the lower the operating voltage of the device is, whereas the uniformity of the current is worse. In particular, in FIG. 2B, the N-type pad electrode ( It can be seen that the operating current is hardly applied to the left region 9L of the P-type pad electrode 9 opposite to the N-type pad electrode 5 and concentrated in the vicinity of 5). This phenomenon occurs because the diffusion resistance of electrons supplied from the N-type pad electrode 5 increases as the distance d between the pad electrodes increases. Therefore, in order to overcome this, a method of increasing the concentration of the N-type nitride semiconductor layer 4 or increasing its thickness has been considered, but in this case, there is a high probability that a defect occurs when the N-type nitride semiconductor layer 4 is grown. There is a limit to thus increasing the conductivity of the N-type nitride semiconductor layer 4 because it may become large and even cracks may occur.

Accordingly, the present invention was devised to solve the above problems, and an object of the present invention is to provide a semiconductor light emitting device having an electrode structure in which the distance d between the pad electrodes can be significantly shortened.

In order to achieve the above object, a semiconductor light emitting device according to the present invention includes n-type and p-type semiconductor layers formed on a substrate, an active layer formed therebetween, and n-type and p-type formed on each of the n-type and p-type semiconductor layers. Pad electrodes, in particular electrically connected to the p-type pad electrode and extending longitudinally in an area opposite the n-type pad electrode with respect to the vertical line between the n-type and p-type pad electrodes with respect to the center line. It may further include one or more branch electrodes. In this case, the branch electrode may be a straight line or a curved line or a combination thereof. In addition, when the branch electrode is formed to be excellent, it is preferable to be symmetrical with respect to the center connection line.

In addition, the semiconductor light emitting device according to the present invention may further include at least one additional supporting electrode electrically connected to the branch electrode and extending in both longitudinal directions therefrom. In this case, the additional supporting electrode is preferably vertically symmetrical with respect to the branch electrode, and may be linear or curved, or a combination thereof.

The semiconductor light emitting device according to the present invention includes branch electrodes having the structure disclosed herein, thereby reducing the distance between the n-type and p-type pad electrodes required for wire bonding for connection to the outside. As a result, a low operating voltage operation can be realized, the current can be evenly distributed even in the light emitting device having a larger area through the branch electrode, and the reliability of the device can be maintained or improved even during the high current operation. In addition, since the current can be prevented from being collected in the branch electrode having a small area, there is an effect of having a high resistance when generating external static electricity.

Accordingly, the present invention provides a specific structure of the P-type pad electrode in order to alleviate or prevent the phenomenon that the operating current is concentrated near the N-type pad electrode causing the high operating voltage and current density distribution of the light emitting element. It is based on forming an electrode to further diffuse the operating current.

Figure 3a is a schematic plan view of a light emitting device 100 according to a preferred embodiment of the present invention, Figure 3b is a cross-sectional view thereof seen from the broken line BB 'of Figure 3a.

Referring to FIG. 3B, a low temperature buffer layer 130, an N-type nitride semiconductor layer 140, an active layer 160 that emits light, and a P-type nitride are formed on a substrate 120 of a material known in the art including sapphire. The semiconductor layer 170 and the P-type electrode 180 are sequentially disposed. In this case, the low temperature buffer layer 130 is to prevent the occurrence of crystal defects due to lattice mismatch between the substrate 120 and the N-type nitride semiconductor layer 140 may be omitted in another embodiment of the present invention. In this case, the P-type electrode 180 is formed to uniformly flow the driving current to the entire surface of the P-type nitride semiconductor layer 170, which is a metal known in the art including Ni, Au, Pd and Pt or It may be a conductive oxide film known in the art including Indium / Tin / Oxide (ITO), and preferably Ni / Au or ITO of a thin film to increase light transmittance. In addition, the P-type pad electrode 190 is disposed on the P-type electrode 180, and the N-type pad electrode 150 is disposed on the N-type nitride semiconductor layer 140, and the electrodes 190 and 150 are wire bonded. By being electrically connected to an external current circuit through the hole, holes are supplied through the P-type pad electrode 190 and electrons are supplied through the N-type pad electrode 150 to apply the holes and electrons in the active layer 160 region. Combine to produce light.

In particular, referring to FIG. 3A, in this embodiment, one end thereof is electrically connected to the P-type pad electrode 190 and a center between the N-type and P-type pad electrodes 150 and 190 for diffusion of a driving current. The branch electrode 191 extends in the longitudinal direction in the region opposite to the n-type pad electrode based on a vertical line (not shown) perpendicular to the connection line, and has a predetermined length L. The branching electrode 191 reduces current concentration between the P-type pad electrode 190 and the N-type pad electrode 150, thereby distributing the current density to a wide area around the P-type pad electrode 190. Is relaxed. This can also have a strong resistance to the occurrence of external static electricity. In addition, the branch electrode 191 may be linear or curved, or a combination thereof.

Table 1 below shows the operating voltage and current density distribution values according to the electrode structures of Example 1 and Comparative Examples 1 and 2 of the present embodiment, and the distance between the pad electrodes d shown in FIG. The length L of the branch electrode 191 is a variable, where the size of each light emitting element is 250 × 600 μm ² and the applied current is 20 mA:

TABLE 1

Branch electrode d (μm) L (μm) Vf (V) I (A / cm ² ) Comparative Example 1 Up 470 0 3.177 2.130 Comparative Example 2 none 270 0 3.068 3.650 Example 1 has exist 270 200 3.054 2.433

Referring to Table 1, Comparative Examples 1 and 2 do not have branch electrodes, and in particular, the distance d between pad electrodes of Comparative Example 1 is the longest. On the other hand, Example 1 has branch electrodes 191 extending from the P-type pad electrode 190 in the opposite direction to the N-type pad electrode 150, and the distance d between the pad electrodes is equal to that of Comparative Example 2; Similarly, it is very close compared with the comparative example 1. According to Table 1, the first embodiment was fixed by 3.05V from 3.17V in this Comparative Example 1, the operating voltage can be seen that the current density variation is improved in Comparative Example 2 of 3.650A / cm ² to 2.433A / cm ² .

4 is a plan view of a light emitting device 100 according to another preferred embodiment of the present invention. At this time, since the schematic sectional drawing of FIG. 4 is the same as FIG. 3B, it abbreviate | omits here.

Referring to FIG. 4, the structure of the present embodiment is the same as that of the above-described embodiment shown in FIG. 3A, except that the second branch electrodes 196-198 are formed at one end of the first branch electrode 191. Only different. That is, in the present embodiment, the branch electrode includes a first branch electrode 191 and one or more second branch electrodes 196 or 197 or 198. The first branch electrode 191 extends at a predetermined length L in an opposite direction to the N-type pad electrode 150 at an electrical connection point with the P-type pad electrode 190, and the second branch electrode 196 or 197 or 198, one surface having a predetermined length T is electrically connected to the first branch electrode 191 at the other end of the first branch electrode 191. In this case, the crossing angle with the first branch electrode 191 is preferably about 90 °. In addition, the second branch electrode 196 or 197 or 198 is positioned above the center of one surface having the predetermined length T by connecting a connection point with the first branch electrode 191 up and down about the connection point. It is preferred to be symmetrical. In addition, as an embodiment, the second branch electrode may be a straight line 196. In another embodiment, the second branch electrode may have a curved surface 197 having a central portion thereof convex toward the P-type pad electrode 190. Or a central portion thereof may be a curved surface 198 concave toward the P-type pad electrode 190, or may be of various combinations of the linear and two curved surfaces. It is not limited to the above-mentioned shapes. This embodiment can achieve the same effect as the embodiment described above with respect to Figure 3a by the above structure.

Table 2 below shows the operating voltage and current density distribution values according to the electrode structures of Example 2 and Comparative Examples 1 and 2 of the present embodiment, and the distance between the pad electrodes (d) and the pad electrodes shown in FIG. The length L of the first branch electrode 191 and the length T of the second branch electrode 196 are variables, wherein each light emitting device has a size of 250 × 600 μm ² and an applied current of 20 mA. :

TABLE 2

Branch electrode d (μm) L (μm) T (μm) Vf (V) I (A / cm ² ) Comparative Example 1 Up 470 0 0 3.177 2.130 Comparative Example 2 none 270 0 0 3.068 3.650 Example 2 has exist
(First and second electrodes) 270 200 200 3.047 2.265

Referring to Table 1, Comparative Examples 1 and 2 do not have branch electrodes, and in particular, the distance d between pad electrodes of Comparative Example 1 is the longest. On the other hand, in Embodiment 2, the first branch electrode 191 is formed extending from the P-type pad electrode 190 in the opposite direction to the N-type pad electrode 150 and at one end of the first branch electrode 191. The center point is connected to the second branch electrode 196 extending vertically, and the distance d between the pad electrodes is very close to that of Comparative Example 1 as in Comparative Example 2. According to Table 2, in Example 2, the operating voltage was improved from 3.17V to 3.04V in Comparative Example 1, and the current density distribution was improved to 2.265A / cm ² from 3.650A / cm ² in Comparative Example 2. In particular, it can be seen that it is more improved than the case of Example 1.

5 is a plan view of a light emitting device 100 according to another preferred embodiment of the present invention. At this time, since the schematic sectional drawing of FIG. 5 is the same as FIG. 3B, it abbreviate | omits here.

Referring to FIG. 5, the structure of this embodiment is the same as that of the above-described embodiment shown in FIG. 3A, except that the branch electrode is composed of a plurality of branch electrodes. The number of branch electrodes of this embodiment is illustrated in FIG. 5 as only two (192, 193) for convenience, but is not limited thereto. One end of each of the branch electrodes 192 and 193 according to the present embodiment is electrically connected to the P-type pad electrode 190 and is perpendicular to a center connection line between the N-type and P-type pad electrodes 150 and 190. It is formed to have a predetermined length (L) extending in the longitudinal direction in the region opposite to the n-type pad electrode with respect to the vertical line (not shown). In this case, the ends of the branch electrodes may be connected to the same point of the P-type pad electrode 190 or may be connected to different points of the P-type pad electrode 190. In addition, the lengths of the branch electrodes may be the same or different from each other. In addition, the branch electrodes may be formed such that the total number is excellent so that they are vertically symmetrical with respect to the center connection line. In addition, the branch electrodes may be linear or curved 194, 195, but the shape thereof is not limited thereto. This embodiment can achieve the same effect as the embodiment described above with respect to Figure 3a by the above structure.

Table 3 below shows the operating voltage and current density distribution values according to the electrode structures of Example 3 and Comparative Examples 1 and 2 of the present embodiment, and the distance between the pad electrodes (d) and the pad electrodes shown in FIG. The length L of the first and second electrodes 192 and 193 is a variable, with each light emitting device having a size of 250 × 600 μm ² and an applied current of 20 mA:

TABLE 3

Branch electrode d (μm) L (μm) T (μm) Vf (V) I (A / cm ² ) Comparative Example 1 Up 470 0 0 3.177 2.130 Comparative Example 2 none 270 0 0 3.068 3.650 Example 3 has exist
(First and second electrodes) 270 200 200 3.045 2.217

Referring to Table 1, Comparative Examples 1 and 2 do not have branch electrodes, and in particular, the distance d between pad electrodes of Comparative Example 1 is the longest. On the other hand, in Example 3, since the first and second electrodes 192 and 193 are provided, the distance d between the pad electrodes is very close to that of Comparative Example 1 as in Comparative Example 2. According to Table 3, in Example 3, the operating voltage was improved from 3.17V to 3.045V in Comparative Example 1, and the current density distribution was improved from 3.650A / cm ² in Comparative Example ² to 2.217A / cm ² . In particular, it can be seen that the embodiments 1 and 2 are further improved.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and any person of ordinary skill in the art may make various modifications, changes, additions, etc. within the spirit and scope of the present invention. And additions should be regarded as within the scope of the claims. For example, the embodiments of the present invention are formed to extend in a direction from the P-type pad electrode 190 to the N-type pad electrode 150 so that one end thereof is electrically connected to the P-type pad electrode 190. Conventional branch electrodes (not shown) connected to each other may be further provided. In this case, the branch electrodes may have the same structure as at least one of the branch electrodes 191 to 198 of the embodiments, thereby alleviating concentration of current density at the ends of the branch electrodes.

1A is a schematic plan view of a general light emitting device.

FIG. 1B is a cross-sectional view of a general light emitting device seen from the broken line A-A 'of FIG. 1A.

FIG. 2A is a graph showing changes in operating voltage (y1 axis) and current density distribution (y2 axis) of a device according to a distance d between a P-type pad electrode and an N-type pad electrode in a 600 × 250 μm ² size light emitting device. FIG.

FIG. 2B is a light power distribution photograph when the distance d between the electrodes in FIG. 2A is 270 μm.

Figure 3a is a schematic plan view of a light emitting device according to an embodiment of the present invention.

3B is a cross-sectional view of the light emitting device of FIG. 3A seen from the broken line BB ′ of FIG. 3A.

Figure 4 is a plan view of a light emitting device according to another preferred embodiment of the present invention.

5 is a plan view of a light emitting device according to another preferred embodiment of the present invention.

Claims (6)

A semiconductor light emitting device comprising n-type and p-type semiconductor layers formed on a substrate, an active layer formed therebetween, and n-type and p-type pad electrodes formed on each of the n-type and p-type semiconductor layers, And at least one branch electrode electrically connected to the p-type pad electrode and extending in a longitudinal direction in a region opposite to the n-type pad electrode based on a vertical line between the n-type and p-type pad electrodes. A semiconductor light emitting device, characterized in that. The method of claim 1, The branch electrode is a semiconductor light emitting device, characterized in that the linear or curved or a combination thereof. The method of claim 1, The branch electrodes are formed of excellent water, and the semiconductor light emitting device, characterized in that symmetrical with respect to the center connection line. The method according to any one of claims 1 to 3, And at least one additional supporting electrode electrically connected to the branch electrodes and extending in both longitudinal directions therefrom. The method of claim 4, wherein The additional supporting electrode is vertically symmetrical with respect to the branch electrode. The method of claim 4, wherein The additional supporting electrode is a semiconductor light emitting device, characterized in that the linear or curved shape or a combination thereof.

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