KR20130087767A - Light emitting device - Google Patents

Abstract

PURPOSE: A light emitting device is provided to improve luminous characteristics by uniformly distributing the temperatures of a central light emitting cell and an outer light emitting cell. CONSTITUTION: A plurality of light emitting cells (10) are formed on a substrate (110). A wire (20) connects the light emitting cells. The light emitting cells have different sizes according to areas. The light emitting cells have different current densities according to the sizes. The substrate includes a side part formed on an edge, a corner part formed on both ends of the side part, and a central part formed between the side part and the corner part.

Description

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device (LED), and more particularly to a light emitting cell array to which a plurality of light emitting cells are connected.

A light emitting device (LED) is an element that generates electrons and holes by using a P-N junction structure of a compound semiconductor, and emits predetermined light by recombination thereof. Such a light emitting device is used in a backlight unit or a lighting device of a display device, and consumes only a few to one tenths of the power of a conventional light bulb or a fluorescent lamp. It is advantageous.

On the other hand, recent lighting devices require a high power light emitting device, and the area of the light emitting device may be increased to implement the high power light emitting device. For example, the area of one light emitting chip may be increased to implement a large area chip, or a plurality of light emitting chips may be connected in parallel to implement a high power light emitting device. In this case, since the light emitting chip is driven at about 3.3V, a power supply having a large current capacity of 6A or more is required to realize a lighting device of about 20W. However, there are disadvantages compared to high voltage / low current lighting devices in terms of energy efficiency and device size of such low voltage / high current lighting devices. In addition, excessively increasing the area of one light emitting chip has an inefficient disadvantage because the rated current decreases due to the nonuniformity of the material and the spreading resistance at the electrode.

In addition, a plurality of light emitting chips or light emitting cells may be connected in series to implement a high voltage driving light emitting cell array. In this case, driving a lighting device at 100V and implementing 20W is about 200mA, which is much more advantageous in terms of power supply size and efficiency than low voltage / high current devices. Therefore, in manufacturing a general lighting device, a light emitting cell array in which a plurality of light emitting cells are connected in series is used.

On the other hand, the light emitting cell array uses a plurality of light emitting cells of the same size. However, the light emitting cells outside the light emitting device may be naturally cooled because they contact with the air, but the light emitting cells in the center of the light emitting device may not be in contact with the air, thereby maintaining a higher temperature than the light emitting cells outside. Accordingly, the light emitting cell in the center of the light emitting device may have low light emission characteristics, and may have a low lifespan.

The present invention provides a light emitting device in which a plurality of light emitting cells are formed in an array in which light emission characteristics can be improved and lifespan can be improved by uniformizing the temperature distribution between the light emitting cells at the center and the light emitting cells at the outside.

The present invention provides a light emitting device in which a plurality of light emitting cells are formed in an array to reduce the current density at the center portion and increase the current density at the outside to make the temperature distribution uniform.

A light emitting device according to an embodiment of the present invention comprises a plurality of light emitting cells; And a wire connecting the light emitting cells, wherein the plurality of light emitting cells are formed in different sizes for each of predetermined regions according to the amount of heat generated per unit area.

The plurality of light emitting cells are connected in series to receive the same current.

The light emitting cells have different current densities according to sizes and generate heat at different temperatures.

The plurality of light emitting cells are arranged in a smaller size as the amount of heat generated per unit area of the predetermined area is smaller.

The plurality of light emitting cells may maintain the same spacing or different spacing according to their size.

In another embodiment, a light emitting device includes: a substrate; A plurality of light emitting cells formed on the substrate; And a line connecting the light emitting cells, wherein the size of the light emitting cells disposed in the peripheral region of the substrate is smaller than that of the light emitting cells disposed in the other regions.

The substrate includes an edge portion corresponding to an edge region, an edge portion corresponding to both ends of the edge portion, and a center portion corresponding to the edge portion and the edge portion.

The light emitting cells disposed at the edges and the edges may be free of light emitting cells adjacent to at least one side surface, and the light emitting cells disposed at the center may be surrounded by side surfaces of light emitting cells adjacent to each other.

At least one first light emitting cell is disposed at the corner portion, and at least one second light emitting cell having a size larger than the first light emitting cell is disposed at the edge portion, and at a central portion, at least one first light emitting cell is larger than the second light emitting cell. A light emitting device in which at least one third light emitting cell is disposed.

Embodiments of the present invention implement a light emitting device by providing a plurality of light emitting cells in different sizes for each region, and apply the same current to drive the same. That is, the small sized light emitting cells generate a high current density and generate heat at a high temperature, and the large sized light emitting cells generate a low current density and generate a low temperature. The light emitting cells are arranged in regions where heat dissipation is not easy. Therefore, the light emitting cell that generates heat at a high temperature can facilitate heat dissipation, thereby making the overall temperature distribution of the light emitting device almost uniform, thereby improving light emission characteristics and preventing the life of the device from being lowered.

1 is a schematic plan view of a light emitting device according to an embodiment of the present invention.
2 is a schematic plan view of a light emitting device according to another embodiment of the present invention;
3 is a cross-sectional view of a light emitting cell according to an embodiment of the present invention.
4 is a schematic diagram showing a temperature distribution of a conventional light emitting device in which a plurality of light emitting cells are connected in series.
5 is a schematic diagram showing a temperature distribution of a light emitting device according to embodiments of the present invention.
6 and 7 are schematic plan views of light emitting devices according to embodiments of the present invention.
8 is a cross-sectional view of a light emitting cell according to another embodiment of the present invention.

Hereinafter, 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 disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to those skilled in the art. It is provided for complete information. In the drawings, the thickness is enlarged to clearly illustrate the various layers and regions, and the same reference numerals denote the same elements in the drawings.

1 is a schematic plan layout of a light emitting device according to an embodiment of the present invention, Figure 2 is a schematic plan layout of a light emitting device according to another embodiment of the present invention. 3 is a partial cross-sectional view of the light emitting cell.

1 and 2, a light emitting device according to an embodiment of the present invention connects a plurality of light emitting cells 11, 12, 13; 10 arranged in different sizes to regions, and connects two adjacent light emitting cells 10. A plurality of light emitting cells 10 are connected in series, including a plurality of wirings 20.

The plurality of light emitting cells 10 may be formed on the same substrate 110. In addition, the plurality of light emitting cells 10 are formed in different sizes for each region. For example, the substrate 110 is divided into a central portion A where the side surface of the light emitting cell 10 is not exposed and a peripheral portion where at least one side surface of the light emitting cell 10 is exposed, and the peripheral portion is again divided into two portions of the substrate 110. The corner portion B, at which the two sides of the light emitting cell 10 are exposed, and the edge portion C, at which one side of the light emitting cell 10 is exposed, are areas extending along one side of the substrate 110. The light emitting cells 10 having different sizes are arranged for each area. That is, the first light emitting cell 11 provided at the corner portion B of the light emitting element is formed to have a smaller size than the second light emitting cell 12 provided at the edge portion C, and the second light emitting cell 12 is formed at the center portion ( It is formed in a smaller size than the third light emitting cell 13 provided in A). That is, the light emitting cells 10 may be arranged in different sizes for each predetermined area according to the amount of heat generated per unit area of the substrate 110. The substrate 110 includes edges C corresponding to the edge regions, edges B corresponding to both ends of the edge C, and a central portion A corresponding between the edge C and the edge B. FIG. Can be set. The light emitting cells 10 disposed at the side portion C and the corner portion B have no light emitting cells adjacent to at least one side surface, and the light emitting cells 10 disposed at the center portion A have light emission adjacent to all of the side surfaces thereof. It is surrounded by the side of the cell 10. Therefore, the corner portion B and the edge portion C are regions where the heat dissipation area is relatively wider because the light emitting cell is absent on some side surfaces of the light emitting cell 10, and thus the heat generation amount per unit area is small. Since the side surfaces are all surrounded by the light emitting cells 10, the heat dissipation area is relatively narrow, and thus the heat generation amount per unit area is large. In this case, the second light emitting cell 12 may be formed to be twice as large as the first light emitting cell 11, and the third light emitting cell 13 is formed to be twice as large as the second light emitting cell 12. Can be. For example, as shown in FIG. 1, two first light emitting cells 11 are provided at the corners B, and each side C of the horizontal and vertical directions between the first light emitting cells 11 is provided. Two and four second light emitting cells 12 may be provided, and four third light emitting cells 13 may be provided in the central portion A. FIG. In addition, as shown in FIG. 2, one first light emitting cell 11 is provided at the corner portion B, and three are respectively provided at the side portions C of the horizontal and vertical directions between the first light emitting cells 11. And four second light emitting cells 12 may be provided, and four third light emitting cells 13 may be provided at the central portion A. FIG. When the light emitting cells 10 are provided in different sizes according to the exposure area with respect to the atmosphere of the light emitting cells 10, they have different current densities when the same current is applied. That is, the first light emitting cell 11 has a higher current density than the second light emitting cell 12, and the third light emitting cell 13 has a lower current density than the second light emitting cell 12. If the current density is high, a lot of heat is generated during light emission, and if a current density is low, little heat is generated during light emission. Accordingly, the temperature at the time of emitting light increases in the order of the high current density, that is, in the order of the first light emitting cell 11, the second light emitting cell 12, and the third light emitting cell 13. As a result, the first light emitting cell 11 having a large amount of heat generation is disposed at a corner portion B having a relatively large heat dissipation area, and the third light emitting cell 13 having a small amount of heat dissipation is disposed at a central portion A having a relatively small heat dissipation area. do. As a result, the temperature distribution is uniform in all regions of the light emitting device. In addition, the plurality of light emitting cells 10 may be spaced apart from each other at the same interval, or may be provided spaced at different intervals according to the size and position. For example, the spacing between the second light emitting cells 12 may be wider than the spacing between the first light emitting cells 11, and the spacing between the third light emitting cells 13 is the first and second light emitting cells. It may be arranged wider than the interval of (11, 12). That is, the light emitting cells 10 disposed in regions where heat dissipation is not easy may be disposed at wide intervals. In addition, the light emitting cells 10 of the same size may have different intervals according to their positions. The second light emitting cells 12 may be arranged at narrow intervals in a large contact area and at a wide interval in a narrow contact area. Can be. On the other hand, the light emitting cells 10 are provided in different sizes for each region, but the structure may be the same. For example, as illustrated in FIG. 2, the first semiconductor layer 120, the active layer 130, the second semiconductor layer 140, and the transparent electrode 150 sequentially stacked on the substrate 110, and 2, the first electrode 160 formed on the exposed first semiconductor layer 130 by removing the semiconductor layer 140 and the active layer 130, and the second electrode 170 formed in a predetermined region on the transparent electrode 150. ) May be included. The light emitting cell 10 will be described in more detail later. In addition, the light emitting cell 10 may be formed to have an inclined side surface. That is, the wiring 20 is formed in contact with the side surface of the light emitting cell 10. When the side surface of the light emitting cell 10 is vertical, since the wiring 20 is not easily formed, the wiring 20 may be disconnected. At least two side surfaces of the light emitting cells 10 in which the wirings 20 are formed are formed to be inclined. In this case, the light emitting cell 10 may be formed at an inclination of, for example, 30 ° to 60 °.

The wiring 20 is formed between two adjacent light emitting cells 10 to electrically connect two adjacent light emitting cells 10. The wiring 20 connects the second electrode 170 of the other light emitting cell 10 adjacent from the first electrode 160 of the one light emitting cell 10. Therefore, the plurality of light emitting cells 10 may be connected in series. In addition, in order to prevent the first semiconductor layer 120, the active layer 130, and the second semiconductor layer 140 of the light emitting cell 10 from being shorted by the wiring 20, an insulating film is formed on the sidewall of the light emitting cell 10. 180 is formed.

Meanwhile, each of the plurality of light emitting cells 10 is formed on the same substrate 110, and as illustrated in FIG. 3, the first semiconductor layer 120, the active layer 130, the second semiconductor layer 140, and the transparent layer are transparent. An electrode 150, a first electrode 160 formed on the first semiconductor layer 130, and a second electrode 170 formed in a predetermined region above the transparent electrode 150 are included. Meanwhile, a buffer layer (not shown) formed between the substrate 110 and the first semiconductor layer 120 may be further included.

The substrate 110 refers to a conventional wafer for fabricating a light emitting device, and preferably, a material suitable for growing a nitride semiconductor single crystal may be used. For example, the substrate 110 may use any one of Al ₂ O ₃ , SiC, ZnO, Si, GaAs, GaP, LiAl ₂ O ₃ , BN, AlN, and GaN.

The first semiconductor layer 120 may be an N-type semiconductor doped with N-type impurities, thereby supplying electrons to the active layer 130. For example, the first semiconductor layer 120 may use a GaN layer doped with N-type impurities, for example, Si. However, the present invention is not limited thereto, and various semiconductor materials are possible. That is, a compound in which nitrides such as GaN, InN, AlN (Group III-V), and such nitrides are mixed at a constant ratio may be used. For example, AlGaN may be used. In addition, the first semiconductor layer 120 may be formed of a multilayer film.

The active layer 130 has a predetermined band gap and is a region where quantum wells are made to recombine electrons and holes. The active layer 130 may be formed of a single quantum well structure (SQW) or a multi quantum well structure (MQW). The multi quantum well structure may be formed by repeatedly stacking a plurality of quantum well layers and barrier layers. For example, the active layer 130 of the multi-quantum well structure may be formed by repeatedly stacking InGaN and GaN, or may be formed by repeatedly stacking AlGaN and GaN. In this case, since the emission wavelength generated by the combination of electrons and holes is changed according to the type of material constituting the active layer 130, it is preferable to adjust the semiconductor material included in the active layer 130 according to the target wavelength. Meanwhile, the active layer 130 is formed by removing a region where the first electrode 160 is to be formed.

The second semiconductor layer 140 may be a semiconductor layer doped with P-type impurities, thereby supplying holes to the active layer 130. For example, the second semiconductor layer 140 may use a GaN layer doped with P-type impurities, for example, Mg. However, the present invention is not limited thereto, and various semiconductor materials are possible. That is, a compound in which nitrides such as GaN, InN, AlN (Group III-V), and such nitrides are mixed at a predetermined ratio may be used. For example, various semiconductor materials including AlGaN and AlInGaN may be used. In addition, the second semiconductor layer 140 may be formed in multiple layers. Meanwhile, the second semiconductor layer 140 is formed by removing a region where the first electrode 160 is to be formed.

The transparent electrode 150 is formed on the second semiconductor layer 140 so that power applied through the second electrode 170 is evenly supplied to the second semiconductor layer 140. In addition, the transparent electrode 150 may be formed of a transparent conductive material so that light generated in the active layer 130 may be transmitted through. For example, the transparent electrode 150 may be formed using ITO, IZO, ZnO, RuOx, TiOx, IrOx, or the like.

The first and second electrodes 160 and 170 may be formed using a conductive material. For example, the first and second electrodes 160 and 170 may be formed using a metal material such as Ti, Cr, Au, Al, Ni, Ag, or an alloy thereof. have. In addition, the first and second electrodes 160 and 170 may be formed in a single layer or multiple layers. The first electrode 160 is formed on the exposed first semiconductor layer 120 by removing predetermined regions of the second semiconductor layer 140 and the active layer 130 to supply power to the first semiconductor layer 120. . In addition, the second electrode 170 is formed in a predetermined region above the transparent electrode 150 to supply power to the second semiconductor layer 140 through the transparent electrode 150. On the other hand, the first electrode 160 is formed near one corner of, for example, a rectangular light emitting element, and the second electrode 170 is formed in a central portion in contact with a surface opposite to the surface on which the first electrode 160 is formed. Can be. However, the formation positions of the first and second electrodes 160 and 170 may be variously changed.

The insulating layer 180 is formed to prevent the first semiconductor layer 120, the active layer 130, and the second semiconductor layer 140 of the light emitting cell 10 from being shorted by the wiring 20. Thus, the insulating layer 180 is formed at least on the side of the light emitting cell 10. That is, the insulating layer 180 may be formed only on the side surface of the light emitting cell 10, and may be formed from the side surface of the light emitting cell 10 to the side surface of the light emitting cell 10 through the upper portion of the substrate 110. The insulating layer 180 may be formed using a silicon oxide layer (SiO ₂ ), a silicon nitride layer (Si ₃ N ₄ ), or the like, and may be formed of a single layer or a plurality of layers.

As described above, an embodiment of the present invention implements a light emitting device by providing a plurality of light emitting cells 10 in different sizes for each region. That is, the first light emitting cell 11 of the first size is disposed in the corner region where the light emitting cells adjacent to at least one side of the light emitting cell is absent, and the second light emitting cell 12 of the second size larger than the first size is disposed. ) Is disposed in the edge region excluding the corner, and the third light emitting cell 13 of the third size larger than the second size is disposed in the center surrounded by the sides of the light emitting cells adjacent to all of the third light emitting cells 13. . When the same current is applied to such a light emitting device, the smaller the size, the lower the current density and accordingly the higher temperature, and the larger the size, the lower the current density and accordingly the lower temperature. However, the larger the amount of heat generated, the larger the heat dissipation area is, so that the almost same temperature distribution is maintained over the entire area of the light emitting element. That is, FIG. 4 is a schematic view of a light emitting device in which a plurality of light emitting cells of the same size are arranged in the related art. In the related art, a plurality of light emitting cells generate heat at the same temperature. The light emitting cells 10a are higher and lower toward the light emitting cells 10b at the edges and the light emitting cells 10c at the edges. Therefore, the light emission characteristics of the light emitting cell 10a in the center portion may be reduced and the life may be shortened. In contrast, FIG. 5 is a schematic view of a light emitting device in which a plurality of light emitting cells having different sizes are arranged for each region according to the present invention. The larger the heat dissipation area is, the higher the temperature is generated. The distribution is uniform. Therefore, the present invention can improve the luminescence properties as compared with the conventional one, and can prevent a decrease in life.

On the other hand, in the present invention, the small sized light emitting cells 11 are arranged in a large heat dissipation area, and the large sized light emitting cells 12 and 13 are arranged in a relatively small heat dissipation area, and thus, are shown in FIGS. 6 and 7. As shown, various modifications are possible. For example, as shown in FIG. 6, the first light emitting cells 11 of the first size are disposed in the corner regions, and the second light emission of the second size is disposed in the horizontal and vertical directions between the first light emitting cells 11. The cells 12 are disposed, and the long axes of the second light emitting cells 12 are disposed to be exposed to the outer surface of the light emitting device. And the 3rd light emitting cell 13 of a 3rd size is arrange | positioned at a center part. In addition, as illustrated in FIG. 7, light emitting cells 10 having different sizes may be arranged in a plurality of square light emitting cells 10 according to heat dissipation areas.

Meanwhile, the embodiment of the present invention has been described in the case where the plurality of light emitting cells 10 formed on the same substrate 110 are connected in series by the wiring 20, but the plurality of light emitting cells 10 is connected to the wire 25. May be connected in series. That is, as shown in FIG. 6, the first semiconductor layer 120, the active layer 130, the second semiconductor layer 140, and the transparent electrode 150 are stacked on the substrate 110, and the first semiconductor layer is formed. A plurality of light emitting cells 10 having a first electrode 160 formed on the 120 and a second electrode 170 formed on the transparent electrode 150 are provided, and a first electrode of the one light emitting cell 10 is provided. The 160 and the second electrode 170 of the other light emitting cell 10 may be connected by the wire 25. Also in this case, light emitting cells 10 having a high current density, that is, small in size, are disposed in a region having a large heat dissipation area, and light emitting cells 10 having a low current density, that is, large in a region, are disposed in a region having a small heat dissipation area. . In addition, when the wire 25 is used, the side surface of the light emitting cell 10 may be formed in a vertical profile instead of being inclined.

10 light emitting cell 20 wiring
110 substrate 120 first semiconductor layer
130: active layer 140: second semiconductor layer
150 transparent electrode 160 first electrode
170: second electrode 180: insulating film

Claims (9)

A plurality of light emitting cells;
A wire connecting the light emitting cells;
The plurality of light emitting cells are formed in different sizes for each of the predetermined area according to the amount of heat generated per unit area.
The light emitting device of claim 1, wherein the plurality of light emitting cells are connected in series and applied with the same current.
The light emitting device of claim 2, wherein the plurality of light emitting cells have different current densities according to sizes and generate heat at different temperatures.
The light emitting device of claim 3, wherein the plurality of light emitting cells are arranged in a smaller size as the amount of heat generated per unit area of the predetermined area is smaller.
The light emitting device of claim 4, wherein the plurality of light emitting cells maintain the same spacing or different spacing according to their size.
Board;
A plurality of light emitting cells formed on the substrate;
A wire connecting the light emitting cells;
And a light emitting cell disposed in a peripheral area of the substrate among the plurality of light emitting cells has a size smaller than that of the light emitting cells disposed in other areas.
The light emitting device of claim 6, wherein the substrate comprises a side portion corresponding to an edge region, a corner portion corresponding to both ends of the edge portion, and a center portion corresponding to the edge portion and the edge portion.
The light emitting cell of claim 7, wherein the light emitting cells disposed at the edges and the corners are free of light emitting cells adjacent to at least one side surface, and the light emitting cells disposed at the center are surrounded by side surfaces of light emitting cells adjacent to each other. Light emitting element.
10. The display device of claim 8, wherein at least one first light emitting cell is disposed at the corner portion, at least one second light emitting cell having a size larger than the first light emitting cell is disposed at the edge portion, and the second portion is disposed at the center portion. A light emitting device in which at least one third light emitting cell of a size larger than the light emitting cell is disposed.

Images