KR20120028741A - Light emitting device - Google Patents

Abstract

The embodiment proposes a light emitting device in which a pattern formed on a substrate is formed in multiple layers to reduce light absorbed into the substrate or total reflection from the substrate, and maximize light extraction efficiency of the emitted light.

Description

Light Emitting Device

The embodiment minimizes absorption in the direction of the substrate and loss of light lost.

In general, the nitride-based light emitting device includes a light emitting structure for generating light having a wavelength corresponding to an ultraviolet to green region, and a substrate supporting the light emitting structure. The light emitting structure emits light in all directions, and part of the light emitting structure travels in the direction of the substrate and is absorbed or scattered by the substrate to reduce light extraction efficiency of the light emitting device.

Currently, a method of reflecting light incident from the light emitting structure toward the light emitting structure by forming a pattern of an uneven structure on a junction surface adjacent to the light emitting structure is applied to the substrate. However, some of the light incident on the substrate does not direct to the light emitting structure, but is absorbed by the substrate again, or the total reflection between the substrate and the light emitting structure tends to reduce the overall light extraction efficiency of the light emitting device. Accordingly, there is a need for a substrate having a new structure for extracting light directed toward the substrate to the outside.

The embodiment maximizes the light extraction efficiency of light absorbed into the substrate by forming a double pattern formed on the substrate or total reflection on the substrate.

A light emitting device according to an embodiment includes a substrate, and a light emitting structure including a first conductive semiconductor layer stacked on the substrate and providing a carrier to an active layer, and a second conductive semiconductor layer, wherein the substrate emits light. It includes a first light extraction pattern formed on the bonding surface adjacent to the structure, and a second light extraction pattern formed on the bottom surface.

Here, the first light extraction pattern and the second light extraction pattern may be the same pattern or different patterns, and in the case of the same pattern, they may be arranged to be offset from each other.

Here, the first light extraction pattern and the second light extraction pattern may be a concave-convex structure protruding in the bonding surface direction or in a direction opposite to the bonding surface.

In addition, the bottom surface may be filled with Al, Ag, and metal oxides thereof between the uneven structures to form a reflective layer.

According to the embodiment, the light toward the substrate can be extracted to the outside to increase the overall light extraction efficiency of the light emitting device.

1 is a conceptual diagram of a light emitting structure according to an embodiment;
2 to 7 are reference drawings for the first to seventh embodiments of the pattern structure of the light emitting device according to the embodiment, and
8 to 11 show another example of the light extraction pattern according to the embodiment.

In the description of embodiments, each layer, region, pattern, or structure is “under” a substrate, each layer (film), region, pad, or “on” of a pattern or other structure. In the case of being described as being formed on the upper or lower, the "on", "under", upper, and lower are "direct" "directly" or "indirectly" through other layers or structures.

In addition, the description of the positional relationship between each layer or structure, please refer to this specification, or drawings attached to this specification.

The thickness and size of each layer in the drawings are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. In addition, the size and area of each component does not necessarily reflect the actual size or area.

Hereinafter, a light emitting device according to an embodiment will be described with reference to the accompanying drawings.

1 illustrates a conceptual diagram of a light emitting structure according to an embodiment.

Referring to FIG. 1, the light emitting device according to the embodiment includes a light emitting structure 110 and a substrate 120. The light emitting structure 110 is an active layer 112 driven by an external power source, and a first conductive semiconductor layer 111 and a second conductive semiconductor layer provided on the lower side and the upper side of the active layer 112 to provide a carrier to the active layer 112. And a light-transmitting electrode layer 114 that transmits light generated by the active layer 112 to the outside. In addition, the light emitting structure may include a current spreading layer (not shown) for spreading a carrier from the second conductive semiconductor layer 113 to the first conductive semiconductor layer 111, or an ESD resistor for resisting external electrostatic discharge (ESD). The layer may further include, but is not limited to.

The substrate 120 supports the light emitting structure 110 and increases light extraction efficiency by scattering light toward the substrate 120 among the light generated by the light emitting structure 110. The substrate 120 may be formed to have a thickness of 10 times the thickness of the light emitting structure 110. The thickness of the substrate 120 should be sufficiently secured to form the second light extraction pattern 124, and in the case where the uneven structure of the bottom surface 122 protrudes to the outside, a thicker thickness may be required. For example, the light emitting structure 110 is 7㎛? In the case of a thickness of 8 μm, the substrate 120 has a thickness of 70 μm? It may be formed to a thickness of 80㎛, or more.

The substrate 120 includes a bonding surface 121 adjacent to the light emitting structure 110 and a bottom surface 122 to be mounted on a package body (not shown), and the bonding surface 121 and the bottom surface 122 are provided on the bonding surface 121 and the bottom surface 122. A pattern for light extraction can be formed. A pattern (hereinafter, referred to as a “first light extraction pattern”) formed on the bonding surface 121 is provided to scatter light from the light emitting structure 110 to the substrate 120, and is formed on the bottom surface 122. The pattern (hereinafter, referred to as a “second light extraction pattern”) scatters light directed through the first light extraction pattern 123 and directed toward the bottom surface 122 toward the side of the light emitting device or the light emitting structure 110. Is prepared to.

The first light extraction pattern 123 is before stacking the light emitting structure 110, and the second light extraction pattern 124 is before or after stacking the light emitting structure 110 on the substrate 120 The surface of the substrate 120 may be formed by etching, dry etching, scratching using a laser beam, or by using a diamond tip or a diamond blade.

The first light extraction pattern 123 and the second light extraction pattern 124 may be formed by chemical etching, scratching using a laser beam, or using a diamond tip or a diamond blade before the light emitting structure 110 is stacked on the substrate 120. It may be formed by scraping the surface of the substrate 120 using. The first light extraction pattern 123 may have a concave-convex shape protruding in the direction of the light emitting structure 110, or may have a concave-convex shape protruding in the direction of the bottom surface 123. Similarly, the second light extraction pattern 124 may also have a concave-convex shape that protrudes in the direction of the light emitting structure 110, or may have a concave-convex shape that protrudes along the direction toward the substrate 120 from the light emitting structure 110.

The first light extraction pattern 123 and the second light extraction pattern 124 prevent the light emitted from the light emitting structure 110 from total reflection between the substrate 120 and the light emitting structure 110. The second light extraction pattern 124 scatters light in any one direction of the first light extraction pattern 123 and the left side and the right side of the substrate 120 so that the light generated in the light emitting structure 110 is as external as possible. To the side.

Meanwhile, the width between the uneven structures constituting the second light extraction pattern 124 or the depth of the uneven structures may be determined in consideration of the critical angles of the light emitting structure 110 and the substrate 120. At this time, the interval between the uneven structure of the first light extraction pattern 123 and the second light extraction pattern 124 has a width and spacing larger than the wavelength of the light incident at the critical angle, the width is 0.001㎛? It can be formed in the range of 10㎛, the spacing is 0.05㎛? It may be formed to 1.5㎛.

2 to 7 illustrate first and seventh embodiments of the pattern structure of the light emitting device according to the embodiment.

First, referring to FIG. 2, the first light extraction pattern 123 protruding toward the light emitting structure 120 and the second light extraction pattern 124 formed under the substrate 110 are configured in the same pattern. It has a double structure. As the first light extraction pattern 123 and the second light extraction pattern 124 are formed in the same shape, the first light extraction pattern 123 and the second light extraction pattern 124 may be subjected to the same etching process or laser process. It can be easily implemented by.

Next, referring to FIG. 3, the first light extraction pattern 211 and the second light extraction pattern 212 have a double structure having the same pattern and protrude in opposite directions. The first light extraction pattern 211 protrudes toward the light emitting structure 220, and the second light extraction pattern 212 protrudes downward from the substrate 210. In this case, the protruding regions of the first light extraction pattern 211 and the second light extraction pattern 212 may be arranged to be offset from each other. Based on the line L1 perpendicular to the light emitting structure 220 and directed toward the non-projection area of the first light extraction pattern 211, the protruding area of the second light extraction pattern 212 is the line L1. The light L1 directly under the light emitting structure 220 may be induced to scatter again in the second light extraction pattern 212.

Next, referring to FIG. 4, the first light extraction pattern 231 and the second light extraction pattern 232 may have different forms. The first light extraction pattern 231 has a shape in which a circular dot protrudes toward the light emitting structure 240, and in the second light extraction pattern 232, a triangular pattern protrudes toward the lower side of the substrate 230. Can be configured.

Next, FIG. 5 illustrates an example of a light extraction pattern formed by irradiating a laser beam, an ion beam, an E-beam, and the like on the lower end of the substrate 250. FIG. 5 illustrates a second light extraction pattern 252 having a rectangular cross section at the bottom of the substrate 250 by irradiating a laser beam, an ion beam, an E-beam, etc. on the bottom of the substrate 250. A first light extraction pattern 251 protruding in the direction of the light emitting structure 260 is formed in the upper direction of the second light extraction pattern 252 to form a double pattern.

Next, referring to FIG. 6, the first light extraction pattern 271 protruding toward the light emitting structure 280 and the second light extraction pattern 272 having a trapezoidal shape protruding below the substrate 270 are illustrated. do. The second light extraction pattern 272 is formed by chemically etching the lower surface of the substrate 270, and may be engraved in a direction toward the light emitting structure 280 on the lower surface of the substrate 270.

Next, FIG. 7 shows the first light extraction pattern 291 protruding toward the light emitting structure 300 and the second light extraction pattern 292 protruding downward from the substrate 290 to form a double light extraction pattern. An example is shown. In FIG. 7, the second light extraction pattern 292 is a pattern formed by etching the lower surface of the substrate 290 in relief, and unlike the second light extraction pattern 272 illustrated in FIG. 6, the shape of the pattern is different. It is formed so as not to face inward of the substrate 290.

In this structure, Ag, Al, or an oxide thereof may be filled between the patterns constituting the second light extraction pattern 292 to form a reflective layer, and the light extraction efficiency may be further increased.

Here, the second light extraction patterns 122, 212, 232, and 252 mentioned in FIGS. 2 to 6 may also be filled with Ag, Al, or oxides thereof between the patterns exposed on the lower side of the substrate to form a reflective layer. It may be.

In addition, the first light extraction patterns 123, 211, 231, 251, and 271 and the second light extraction patterns 122, 212, 232, 252, and 272 mentioned in FIGS. 2 to 7 are chemically etched and dry etched. It can be formed by the laser scratch by the laser beam, but can be used selectively or together depending on the convenience of manufacturing, of course.

8 to 11 show another example of the light extraction pattern according to the embodiment.

The light extraction patterns illustrated in FIGS. 8 to 11 may include the first light extraction patterns 123, 211, 231, 251, and 271 (hereinafter omitted) shown in FIGS. 2 to 7, or the second light extraction patterns 122. 212, 232, 252, 272, hereinafter omitted), the first light extraction pattern and the second light extraction pattern may be the same shape or different shapes. However, it is not limited thereto.

First, FIG. 8 illustrates an example in which one of the first and second light extraction patterns has a rectangular lattice shape, FIG. 9 illustrates an example of forming a diagonal checkered pattern, and FIG. 10 illustrates a circular shape. An example of forming a dot pattern is illustrated, and FIG. 11 illustrates an example of a hexagonal pattern in the form of a honeycomb. The illustrated patterns may correspond to the first light extraction pattern or the second light extraction pattern in the structure described with reference to FIGS. 2 to 7. 8 or 9 may be formed by using a laser beam or by scraping with a diamond tip or a diamond blade. However, it is not limited thereto.

In addition, the circular dots and polygonal dots shown in FIGS. 10 and 11 are easy to implement through chemical etching or dry etching. 8 to 11 may be embossed or engraved to be inserted in the direction of the substrate, or may be embodied in the form of protruding from the substrate. It may be engraved according to the direction toward the substrate.

In the above, the shape of the first light extraction pattern and the second light extraction pattern has been exemplified by being formed into a lattice Mooney, a checkered pattern, a circle, and a polygon. However, the shapes of the first light extraction pattern and the second light extraction pattern described with reference to FIGS. 2 to 11 may be formed in an irregular pattern to increase light scattering efficiency. When the first light extraction pattern and the second light extraction pattern are formed in an irregular pattern, light scattered in both lateral directions of the substrate may further increase, and the shape of the irregular pattern is not limited.

In this embodiment, laser scratching is performed using a laser beam, and chemical etching and dry etching are exemplified. However, the first light extraction pattern and the second light extraction pattern referred to in FIGS. 2 to 11 may be formed by directly scraping the substrate by a diamond tip or a diamond blade. However, in order to form the first light extraction pattern and the second light extraction pattern, the first light extraction pattern and the second light extraction pattern may be formed by scraping with a material having a higher hardness than the substrate.

Features, structures, effects, and the like described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in each embodiment may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

In addition, the above description has been made with reference to the embodiment, which is merely an example, and is not intended to limit the present invention. Those skilled in the art to which the present invention pertains will be illustrated as above without departing from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications should be construed as being included in the scope of the rights provided in the appended claims.

110 light emitting structure 111 first conductive semiconductor layer
112: active layer 113: second conductive semiconductor layer
114: transparent electrode layer 120: substrate
121: joint surface 122: bottom surface
123: first light extraction pattern 124: second light extraction pattern

Claims (10)

Board; And
And a light emitting structure stacked on the substrate, the light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer.
The substrate,
A first light extraction pattern positioned on an opposite surface to the light emitting structure; And
Light emitting device comprising a; second light extraction pattern located on the bottom surface. The method of claim 1,
The first light extraction pattern and the second light extraction pattern,
Light emitting elements that are different patterns. The method of claim 1,
The first light extraction pattern and the second light extraction pattern,
The light emitting element which is the same pattern. The method of claim 3,
The first light extraction pattern and the second light extraction pattern,
The light emitting element in which the same pattern is mutually shift | deviated. The method of claim 1,
The first light extraction pattern and the second light extraction pattern,
A light emitting device formed of any one of embossed and intaglio. The method of claim 1,
The first light extraction pattern and the second light extraction pattern,
A light emitting device formed by any one of chemical etching, dry etching, and laser scratching on the substrate. The method of claim 1,
The bottom surface is,
And a reflective layer filled and formed between the uneven structures of the second light extraction pattern. The method of claim 7, wherein
The reflective layer,
A light emitting device, which is any one of Al, Ag, and metal oxides thereof. The method of claim 1,
The first light extraction pattern, and the second light extraction pattern,
A light emitting element in which the pattern is any one of a checkered pattern, a plaid pattern, an oblique pattern, an atypical pattern, a dot pattern, and a polygonal pattern. The method of claim 1,
The substrate,
Light emitting device having a thickness of at least 10 times the thickness of the light emitting structure.

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