KR101158080B1

KR101158080B1 - Light emitting diode

Info

Publication number: KR101158080B1
Application number: KR1020100070840A
Authority: KR
Inventors: 김종규
Original assignee: 서울옵토디바이스주식회사
Priority date: 2010-07-22
Filing date: 2010-07-22
Publication date: 2012-06-22
Also published as: KR20120009874A

Abstract

A light emitting diode suitable for alternating current driving including a plurality of light emitting cells on a single substrate is disclosed. This light emitting diode comprises: a substrate; A plurality of light emitting cells formed on the substrate and having corners opposite to one side at edges thereof; A first electrode pad formed at one side corner; A linear second electrode pad facing the first electrode pad and defining a periphery of the opposite corner with the edge; And a wire connecting the first electrode pad and the second electrode pad between two light emitting cells.

Description

[0001] LIGHT EMITTING DIODE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode comprising a compound semiconductor, and more particularly, to a light emitting diode having improved current dispersion characteristics and improved light uniformity. The present invention is suitable for a light emitting diode comprising a plurality of light emitting cells on a substrate, in particular for an AC driven light emitting diode.

A light emitting diode is a light emitting device made of a compound semiconductor, in particular, a group III nitride-based compound semiconductor, and has been widely used in display devices and backlight devices. Use area is getting wider.

A typical light emitting diode is turned on / off in accordance with the direction of the current under AC power. Therefore, when the light emitting diode is directly connected to an AC power source, the light emitting diode does not emit light continuously and is easily damaged by reverse current. As a technology for solving the problem of the light emitting diode, a light emitting diode that can be used by connecting directly to a high voltage AC power source is disclosed in International Publication No. WO2004 / 023568 (A1) "Light-EMITTING DEVICE HAVING LIGHT -EMITTING ELEMENTS, which was disclosed by SAKAI et.al.

1 is a view for explaining a conventional AC light emitting diode. Referring to FIG. 1, the AC light emitting diode 1 includes rectangular light emitting cells 4 formed by forming a group III nitride-based compound semiconductor layer on an insulating substrate, in particular, a sapphire substrate 2. Bonding pads 3a and 3b are formed on the substrate 2. Each of the light emitting cells 4 includes an n-type semiconductor layer, a p-type semiconductor layer, and an active layer interposed therebetween, and a transparent electrode layer such as an ITO layer may be formed thereon. In addition, the plurality of light emitting cells 4 are formed by dividing a plurality of stacked layers of the compound semiconductor layers as described above.

The conventional light emitting diode 1 includes an n-type electrode pad 6 and a p-type electrode pad 8 on the light emitting cell 4. The light emitting cell 4 is partially removed from the top to a certain depth to expose a part of the layer in the middle of the light emitting cell 4, which is usually an n-type semiconductor layer, and the exposed n-type semiconductor. An n-type electrode pad 6 is formed in one region of the layer. The p-type electrode pad 8 is formed in the p-side region in the uppermost layer of the light emitting cell 4. The n-type electrode pads 6 and the p-type electrode pads 8 are positioned to face each other while being positioned at opposite corners of the light emitting cell 4 while being formed in a straight or bar shape. The bonding pads 3a and 3b and the light emitting cells 4 therebetween are connected in series by the wirings 5. The wiring 5 electrically connects the p-type electrode pad 8 and the n-type electrode pad 8 of neighboring light emitting cells.

In the conventional light emitting diode, when the distance between the n-type electrode pad 6 and the p-type electrode pad 8 is far, the current concentrates only around the p-type electrode pad 8, and the p-type electrode pad 8 ) Only the surroundings emit strong light. In addition, when the p-type electrode pad 8 is placed close to the n-type electrode pad 6, the brightness of the region between the p-type electrode pad 8 and the n-type electrode pad 6 will increase, but the p-type Brightness between the electrode pad 8 and the edge of the light emitting cell is greatly reduced. This greatly hinders the uniformity of light emission of the light emitting diodes, which is a major obstacle to the large area of the light emitting diodes.

In addition, as another type of light emitting diode in the related art, n-type electrode pads and p-type electrode pads are formed in a square or a circle, and these electrode pads are arranged to face diagonally at both corners of the light emitting cell. The light emitting diode of was also bright only around the p-type electrode pad 8, resulting in poor uniformity of light emission.

Accordingly, one problem to be solved by the present invention is to provide a light emitting diode having improved uniformity of light emission by improving current dispersion characteristics between electrode pads of light emitting cells having opposite polarities.

According to an aspect of the present invention, there is provided a light emitting diode comprising: a substrate and a plurality of light emitting cells formed on the substrate and having corners opposite to one side; A first electrode pad formed at one side corner; A linear second electrode pad facing the first electrode pad and defining a periphery of the opposite corner with the edge; And a wire connecting the first electrode pad and the second electrode pad between two light emitting cells. At this time, the ends of the second electrode pad is preferably adjacent to the edge.

According to one embodiment, the wiring is preferably formed by a step cover process, but may be a wire connecting between the electrode pads connected by the air bridge process.

According to an embodiment, the first electrode pad may include two or more straight portions or one or more curved portions connected along the contour of the one corner.

In example embodiments, the light emitting cell may have a quadrangular shape, and the first electrode pad may include two straight portions parallel to two sides of the one corner and adjacent to a vertex of the one corner. The second electrode pad may include two straight portions extending from the end portions adjacent to two sides of the opposite corner in a direction approaching the first electrode pad to meet each other in the middle. In addition, an angle formed by the straight portions of the second electrode pad may be equal to or greater than an angle formed by the straight portions of the first electrode pad. Alternatively, the second electrode pad may be formed of one straight portion whose both ends are adjacent to two sides of the opposite corner.

According to an exemplary embodiment, one of the straight portions of the first electrode pad may be connected to the adjacent light emitting cells in common, and the other straight portions may be connected to be in a straight line with the straight portions of the neighboring light emitting cells.

According to an embodiment, the light emitting cells may be circular or elliptical, and the first electrode pads may be formed in an arc shape along the one corner. In addition, the second electrode pad may include an arc shape parallel to the first electrode pad.

According to one embodiment, the light emitting cell is a polygon, the first electrode pad and the second electrode pad may be parallel.

In example embodiments, a first bonding pad and a second bonding pad are formed on the substrate, and the plurality of light emitting cells may include: a light emitting cell in which one end of a first electrode pad is connected by wiring to the first bonding pad; One end of the second electrode pad may include a light emitting cell connected to the second bonding pad by a wire.

According to another aspect of the present invention, a light emitting diode includes a light emitting cell having a corner opposite to one side, a first electrode pad formed at the one corner, and the opposite corner with the edge facing the first electrode pad. And a linear second electrode pad defining a periphery of the region.

In the present specification, the term 'light emitting cell' refers to a minimum unit of a compound semiconductor layer stack including a region where light is emitted.

The light emitting diode according to the present invention greatly improves the uniformity of light emission by the improved current dispersing property between the first electrode pad and the second electrode pad of the light emitting cell, and also increases the power efficiency. In particular, in the case of a light emitting diode including a plurality of light emitting cells on a single substrate, in particular, a light emitting diode connected to an AC power source, all of the light emitting cells emit uniform light and power efficiency is greatly increased.

1 is a plan view for explaining a conventional light emitting diode including a plurality of light emitting cells,
2 is a plan view illustrating a light emitting diode according to an embodiment of the present invention;
3 is an enlarged plan view illustrating a light emitting cell of the light emitting diode of FIG. 2;
4 to 10 are views for explaining light emitting cells according to various embodiments of the present disclosure.
11A and 11B are photographs showing light emission uniformity test results of a light emitting diode according to the present invention and a light emitting diode according to a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience.

2 is a plan view illustrating a light emitting diode according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the light emitting diode 100 includes a substrate 20 and a plurality of light emitting cells 40. A first electrode pad 60 (hereinafter referred to as an 'n-type electrode pad') and a second electrode pad 80 (hereinafter referred to as a 'p-type electrode pad') are formed on the light emitting cell 40. In addition, the light emitting diodes 100 may include a first bonding pad 32 and a second bonding pad 34 formed on the substrate 20.

The plurality of light emitting cells 40 are formed on a single substrate 20 and are connected in series through wires 52 to form an array. To this end, the wirings 52 electrically connect the n-type electrode pad 60 and the p-type electrode pad 80 of the neighboring light emitting cells 40 and 40. The first bonding pad 32 is connected in series to the p-type electrode pad 80 of the light emitting cell 40 at one end of the array by a wiring 54a, and the second bonding pad (by the wiring 54b). 34 is connected in series to the n-type electrode pad 60 of the light emitting cell 40 at the other end of the array. Although not shown, arrays of the light emitting cells 40 may be reversely connected between the bonding pads 32 and 34 to be driven under AC power. The wirings 52 may include forming an insulating layer covering the substrate 20 and the light emitting cells 40, opening a portion of the insulating layer to expose the electrode pads 60 and 80, and forming an insulating layer on the insulating layer. The conductive material layer may be formed in a line shape, and the conductive material layer may be formed by a so-called step cover process including connecting the electrode pads of adjacent light emitting cells. The layer serves substantially as the wirings 52 electrically connecting the light emitting cells.

As the substrate 20, an insulating substrate capable of electrically insulating the light emitting cells 40 is used. A sapphire substrate is preferred as a growth substrate for growing the nitride semiconductor layers constituting the light emitting cells 40. The light emitting cells 40 may be formed to have the same area, but may have different areas. Each of the light emitting cells 40 may sequentially include an n-type semiconductor layer, an active layer, and a p-type semiconductor layer from the substrate 20, and a transparent electrode layer such as an ITO layer may be formed on the p-type semiconductor layer. . However, based on the active layer, the n-type semiconductor layer may be formed on the upper portion of the p-type semiconductor layer.

Referring to FIG. 3, the light emitting cell 40 of the light emitting diode shown in FIG. 1 is enlarged. Referring to FIG. 3, the light emitting cell 40 includes an approximately square edge, and an n-type electrode pad 60 is formed at one corner of the edge of the light emitting cell 40. The n-type electrode pad 60 includes two straight portions 62 and 64 parallel to two sides of one corner of the light emitting cell 40, that is, two adjacent sides S1 and S2 of a quadrangle. The two straight portions 62 and 64 meet vertically near the vertex V1 of the one corner. At this time, one side corner of the light emitting cell 40 is substantially the same as the region where the p-type semiconductor layer and the active layer is removed to expose the n-type semiconductor layer, the region of the one side corner has a shape of approximately 'a'. In addition, the p-type electrode pad 80 is formed such that both ends thereof are adjacent to the edge of the light emitting cell 40 while the center portion is spaced apart from the opposite corner of the light emitting cell 40. The p-type electrode pad 80 is defined in such a manner as to surround the peripheral area A of the opposite corner with the edges of the opposite corner, that is, the two sides S3 and S4 of the light emitting cells. The p-type electrode pad 80 extends from the ends adjacent to the two sides S3 and S4 in a direction approaching the n-type electrode pad 60 so as to meet two straight portions 82 and 84 at the center. Include them. With this shape, the distance between the p-type electrode pad 80 and the n-type electrode pad 60 can be sufficiently close, but the area behind the p-type electrode pad 80, that is, the area around the opposite corner The area of (A) does not greatly increase. This greatly contributes to preventing the light emission unevenness of the light emitting cell 40 caused by the concentration of current around the p-type electrode pad 80. In addition, the peripheral area A is divided into two areas by an imaginary diagonal line (indicated by a double-dotted line) connecting vertices V1 and V2 of both corners, both of which are the p-type electrode pads. Since it is close to both ends of 80, there is not much fall of the brightness of light. The angle formed by the two straight portions 82 and 84 of the p-type electrode pad 80 may be greater than about 90 °, the angle formed by the two straight portions 62 and 64 of the n-type electrode pad 60.

The planar shape of the light emitting cell 40 and the electrode pads 60 and 80 and the arrangement of the electrode pads 60 and 80 on the light emitting cell 40 are modified in various forms within the scope of the technical idea of the present invention. 4 to 11 illustrate the shapes and arrangements of the light emitting cells 40 and the electrode pads 60 and 80 according to various embodiments of the present disclosure.

FIG. 4 illustrates that the n-type electrode pad 60 and the p-type electrode pad 80 are disposed on the light emitting cell 40 having a substantially square (or rectangular) shape as in the embodiment of FIG. 3, except that the p-type electrode is provided. The angle formed by the two straight portions 82 and 84 of the pad 80 is the same as the angle formed by the two straight portions 62 and 64 of the n-type electrode pad 60.

5 shows that the p-type electrode pad 80 is formed of one straight portion unlike the previous embodiments. The p-type electrode pad 80 includes both ends adjacent to two sides S3 and S4 of opposite corners, that is, opposite corners of the n-type electrode pad 60. Although the p-type electrode pad 80 is formed of one straight portion, the p-type electrode pad 80 may be defined in such a manner as to surround the area A around the opposite corner together with the edges S3 and S4 of the opposite corner. Can be. In addition, since both ends of the p-type electrode pad 80 are adjacent to the two sides (S3, S4) on the edge of the opposite corner, the center portion is close to the n-type electrode pad 60, the foregoing embodiments In the same manner as above, light uniformity of the light emitting cells 40 may be widely dispersed.

FIG. 6 is an improved embodiment of the embodiment of FIG. 5, in which both ends of the straight portion of the p-type electrode pad 80 are extended so as to be shorter to both sides S3 and S4 at opposite corners. 85b) is further formed.

7 shows an embodiment in which the light emitting cells 40 are formed in parallelograms. The term 'square' in the claims of the present invention includes not only rectangles, squares, but also all geometric shapes consisting of parallelograms, trapezoids or only four corner angles.

FIG. 8 illustrates an embodiment in which one n-type electrode pad 60 is commonly belong to two neighboring light emitting cells 40 and 40. Referring to FIG. 8, one of the straight portions 64 of the straight portions of the n-type electrode pad 60 belonging to one light emitting cell 40 belongs to another neighboring light emitting cell 40 and the remaining straight lines The part 62 is connected to be in line with another straight line part of the neighboring other light emitting cells 40.

9 shows an embodiment in which the light emitting cell 40 is circular. One corner of the circular light emitting cell 40 is defined as the vicinity of an arc of the circular light emitting cell 40, and the opposite corner is defined as the vicinity of the circular arc opposite to the one corner. The n-type electrode pad 60 is formed in a (circle) arc shape along the one side corner, and the second electrode pad 80 is formed on the upper surface of the light emitting cell 40 to be parallel to the n-type electrode pad 60. It is formed, and surrounds the periphery of the opposite corner with the circular-shaped edge and limits. Both ends of the second electrode pad 80 are close to the edge of the light emitting cell 40, that is, the circumference thereof, and the center portion of the second electrode pad 80 faces toward the n-type electrode pad 60. . The light emitting cell 40 may have another geometric shape including elliptical or curved.

10 shows an embodiment in which the light emitting cell 40 has an octagon. Since the light emitting cell of the present embodiment is formed in an octagonal shape by removing the part indicated by the double-dot chain line from the rectangle, the parts indicated by the double-dot chain line correspond to the corners of the rectangle. Accordingly, the n-type electrode pad 60 may be viewed as disposed at one corner of the light emitting cell 40. The n-type electrode pad 60 has a shape corresponding to one corner, that is, two short straight portions are connected to both ends of one long straight portion in the center thereof, and the second electrode pad 80 has the shape of n. It is arranged in parallel with the n-type electrode pad 60 in the same shape as the type electrode pad 60. The second electrode pad 80 surrounds the opposite corner A together with its edge. Both ends of the second electrode pad 80 are closer to the edge of the light emitting cell 40 than the center portion.

11A and 11B are photographic diagrams showing light emission uniformity test results of a light emitting diode according to an exemplary embodiment of the present invention and a conventional light emitting diode (comparative example), and Table 1 below is an embodiment of the present invention. The electrical characteristics of the comparative example were tested and compared. The material of the semiconductor layers constituting the light emitting cell and the size of the light emitting cells are the same as in the embodiment and the comparative example, and only the structure of the light emitting cell and the arrangement of electrode pads are different. An ITO layer of 1200 셀 thickness was employed on the light emitting cell.

The light emitting diode of this embodiment shown in FIG. 11A has a uniform brightness of the entire light emitting cell, whereas the light emitting diode of Comparative Example shown in FIG. 11B shows a large difference in brightness between the near and far portions of the p-type electrode pad. Note that the relatively dark areas shown in FIGS. 11A and 11B are actually light emitting areas.

Referring to Table 1 below, it can be seen that the power efficiency of the present embodiment is better than that of the comparative example. In the present embodiment, compared with the comparative example, it can be seen that the average forward voltage is lower, the output is larger, and the power efficiency is greatly increased.

division Forward voltage Power wavelength Power efficiency
WPE (%) Avg. [V] Std Avg. [mW] Std Avg. [nm] Std In comparison 56.92 2.70 362.87 19.19 454.25 0.89 31.88 Example 56.58 1.23 382.00 12.08 453.71 1.54 33.76

20: substrate 40: light emitting cell
60: n-type electrode pad (first electrode pad) 80: p-type electrode pad (second electrode pad)
32, 34: bonding pad

Claims

Board;
A plurality of light emitting cells formed on the substrate and having one corner and an opposite corner at an edge thereof;
A first electrode pad formed at one side corner;
A linear second electrode pad facing the first electrode pad and defining a periphery of the opposite corner with the edge; And
A wiring connecting the first electrode pad and the second electrode pad between two light emitting cells;
End portions of the second electrode pad are adjacent to the edge.

delete

The light emitting diode of claim 1, wherein the wiring is formed by a step cover process.

The light emitting diode of claim 1, wherein the first electrode pad includes at least two straight portions or at least one curved portion connected along a contour of the one corner.

The light emitting diode of claim 1, wherein the light emitting cell has a quadrangle, and the first electrode pad includes two straight portions parallel to two sides of the one corner and adjacent to a vertex of the one corner.

The light emitting device as set forth in claim 5, wherein the second electrode pad includes two straight portions which extend from the ends adjacent to two sides of the opposite corner to the first electrode pad and meet each other in the middle. diode.

The light emitting diode of claim 6, wherein an angle formed by the straight portions of the second electrode pad is equal to or greater than an angle formed by the straight portions of the first electrode pad.

The light emitting diode of claim 5, wherein the second electrode pad is formed of one straight portion whose both ends are adjacent to two sides of the opposite corner.

The light emitting diode of claim 5, wherein one of the straight portions of the straight portions of the first electrode pad belongs to a neighboring light emitting cell, and the remaining straight portions are connected in a straight line with the straight portions of the neighboring light emitting cells. .

The light emitting diode of claim 1, wherein the light emitting cell is circular or elliptical, and the first electrode pad is formed in an arc shape along the one corner.

The light emitting diode of claim 10, wherein the second electrode pad includes an arc shape parallel to the first electrode pad.

The light emitting diode of claim 1, wherein the light emitting cell is polygonal, and the first electrode pad and the second electrode pad are parallel to each other.

The method according to claim 1,
A first bonding pad and a second bonding pad are formed on the substrate, and the plurality of light emitting cells may include: a light emitting cell having one end of a first electrode pad connected to the first bonding pad by a wire; and the second electrode pad. Wherein one end of the light emitting cell includes a light emitting cell connected to the second bonding pad by a wire.

A light emitting cell having one corner and an opposite corner at an edge thereof;
A first electrode pad formed at one side corner; And
A linear second electrode pad facing the first electrode pad and defining a periphery of the opposite corner with the edge;
The first electrode pad includes at least two straight portions or at least one curved portion connected along the contour of the one corner.

delete

The light emitting diode of claim 14, wherein the light emitting cell has a quadrangular shape, and the first electrode pad includes two straight portions parallel to two sides of the one corner and adjacent to a vertex of the one corner.

17. The light emitting device of claim 16, wherein the second electrode pad includes two straight portions which extend from the ends adjacent to two sides of the opposite corner to the second electrode pad and meet each other in the middle. diode.

The light emitting diode of claim 16, wherein an angle formed by the straight portions of the second electrode pad is equal to or greater than an angle formed by the straight portions of the first electrode pad.

17. The light emitting diode of claim 16, wherein the second electrode pad is formed of one straight portion whose both ends are adjacent to two sides of the opposite corner.

The light emitting diode of claim 14, wherein the light emitting cell is circular or elliptical, and the first electrode pad is formed in an arc shape along the one corner.

21. The light emitting diode of claim 20, wherein the second electrode pad comprises an arc shape parallel to the first electrode pad.