KR20140085919A - Light emitting diode and lighting apparatus employing the same - Google Patents

Abstract

Disclosed are a light emitting diode and a lighting apparatus applying the same. The light emitting diode comprises a transparent substrate having a first surface, a second surface, and a side surface; a first conductive semiconductor layer disposed on the first surface of the transparent substrate; a second conductive semiconductor layer disposed on the first conductive semiconductor layer; an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first pad electrically connected to the first conductive semiconductor layer; and a second pad electrically connected to the second conductive semiconductor layer. In addition, the light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate, and the transparent substrate is in the form of a polygon having at least one acute angle. Therefore, provided is the light emitting diode having improved light efficiency and also having the properties of a beam spread angle depending on the direction.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode (LED)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode and a lighting apparatus, and more particularly, to a light emitting diode having different directional characteristics according to a direction and a lighting apparatus employing the same.

BACKGROUND ART GaN-based LEDs have been used in a variety of applications such as color LED display devices, LED traffic signals, backlight units, and lighting devices since gallium nitride (GaN) -based LEDs have been developed.

Gallium nitride based light emitting diodes are generally formed by growing epitaxial layers on a substrate such as sapphire and include an N-type semiconductor layer, a P-type semiconductor layer, and an active layer interposed therebetween. On the other hand, an N-electrode pad is formed on the N-type semiconductor layer, and a P-electrode pad is formed on the P-type semiconductor layer. The light emitting diode is electrically connected to the external power source through the electrode pads and driven. At this time, current flows from the P-electrode pad to the N-electrode pad through the semiconductor layers.

On the other hand, a flip-chip type light emitting diode is used to prevent light loss caused by the P-electrode pad and to increase heat dissipation efficiency. Since the flip chip type light emitting diode emits light to the outside through the growth substrate, light loss due to the P-electrode pad can be reduced as compared with a light emitting diode having a horizontal structure that emits light to the outside through the epi layer. Furthermore, since the light emitting diode having a horizontal structure has to transmit heat through a growth substrate such as a sapphire substrate, heat dissipation efficiency is low. On the other hand, the flip chip type light emitting diodes transmit heat through the electrode pads, and thus heat radiation efficiency is high.

Further, in order to increase light extraction efficiency, vertical type light emitting diodes are being developed in which a growth substrate such as sapphire is removed from an epi layer. In particular, the light emitting diode of the vertical structure can prevent light loss due to total internal reflection by texturing the surface of the exposed semiconductor layer.

On the other hand, in a specific application, for example, in an illumination device such as an LED fluorescent lamp, an LED having different orientation angles depending on the direction may be required. When a large number of LEDs are mounted in an illuminating device having a long fluorescent lamp shape, it is advantageous that the directional angle of the LEDs is large in a direction orthogonal to the direction of the fluorescent lamp.

A problem to be solved by the present invention is to provide a light emitting diode having different directivity angles according to a direction and a lighting apparatus employing the same.

Another object of the present invention is to provide a flip chip type light emitting diode having improved luminous efficiency and a lighting apparatus having the same.

A light emitting diode according to an aspect of the present invention includes: a transparent substrate having a first surface, a second surface, and a side connecting the first surface and the second surface; A first conductive semiconductor layer located on a first surface of the transparent substrate; A second conductive semiconductor layer disposed on the first conductive semiconductor layer; An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; A first pad electrically connected to the first conductive semiconductor layer; And a second pad electrically connected to the second conductivity type semiconductor layer. Also, the light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate, and the transparent substrate has a polygonal shape having at least one acute angle.

Since light emitted near the corner increases, the light extraction efficiency of the light emitting diode is improved, and further, the directivity characteristics of the light emitting diode can be controlled. Therefore, it is possible to provide a light emitting diode having different directivity angles depending on the direction.

The transparent substrate may have a thickness in the range of 100 mu m to 400 mu m. Further, the polygonal shape having the at least one acute angle may be a triangular shape, a parallelogram shape, or a pentagonal shape. The transparent substrate may be a sapphire substrate. Further, the transparent substrate may have a parallelogram shape, and the side surface of the transparent substrate may be an m-plane group. Since the side surface of the transparent substrate is made of the group of m planes, the wafer can be scribed along the crystal plane of the m plane group, thereby preventing damage such as chipping during division into individual light emitting diodes.

The light emitting diode may further include a reflective electrode positioned on the second conductive semiconductor layer and reflecting light generated in the active layer. The light efficiency can be improved by reflecting light by the reflective electrode.

Meanwhile, the active layer and the second conductivity type semiconductor layer may be confined within the upper region of the first conductivity type semiconductor layer such that the upper surface of the first conductivity type semiconductor layer is exposed along the edge of the substrate.

The light emitting diode may further include a current dispersion layer connecting the first pad and the first conductivity type semiconductor layer, wherein the first pad and the second pad are formed on the second conductivity type semiconductor layer Can be located. Accordingly, the height difference between the first pad and the second pad can be reduced, and the flip chip bonding can be facilitated.

Furthermore, the current-spreading layer may include a reflective metal. The light can be reflected by the current dispersion layer in addition to the reflective electrode, thereby further increasing the light efficiency of the light emitting diode.

The light emitting diode may further include a lower insulating layer for insulating the current dispersion layer from the reflective electrode. The lower insulating layer has openings for exposing the first conductivity type semiconductor layer, and the current spreading layer may be connected to the first conductivity type semiconductor layer through the openings.

In some embodiments, the openings may each be arranged in an elongated shape along the edges of the substrate. In addition, the openings may be further away from the at least one example portion than the other portions. Thus, concentration of current in the corner portions can be mitigated.

In other embodiments, the openings may include a plurality of holes spaced apart from one another along an edge of the substrate. The spacing between the holes may increase as the distance is closer to the at least one leg portion. Thus, concentration of current in the corner portions can be mitigated.

The side surface of the light emitting diode may be inclined such that the first surface has a larger area than the second surface. The light extraction efficiency is further improved by inclined sides.

In some embodiments, the light emitting diode may further comprise a conformal coating covering the second side of the substrate. The sum of the thicknesses of the transparent substrate and the conformal coating may have a value within a range of 225 μm to 600 μm, thereby increasing the directivity angle of light.

According to still another aspect of the present invention, there is provided a lighting apparatus including a plurality of light emitting diodes. At least one light emitting diode of the light emitting diodes includes: a transparent substrate having a first side, a second side, and a side connecting the first side and the second side; A first conductive semiconductor layer located on a first surface of the transparent substrate; A second conductive semiconductor layer disposed on the first conductive semiconductor layer; An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; A first pad electrically connected to the first conductive semiconductor layer; And a second pad electrically connected to the second conductivity type semiconductor layer. Also, the light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate, and the transparent substrate has a polygonal shape having at least one acute angle.

According to the embodiments of the present invention, it is possible to provide a flip-chip type light emitting diode having an improved luminous efficiency by adopting a substrate having at least one acute angle portion and also having different directing angle characteristics depending on the direction. Furthermore, by adopting such a light emitting diode, it is possible to provide an illumination device capable of illuminating a wide area while reducing light loss.

FIGS. 1 to 5 are views for explaining a method of manufacturing a light emitting diode according to an embodiment of the present invention, in which (a) is a plan view, and (b) is a cross-sectional view taken along the cutting line AA.
6 is a plan view for explaining a modified example of an opening for exposing the first conductivity type semiconductor layer.
7 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.
8 is a cross-sectional view illustrating a light emitting diode according to another embodiment of the present invention.
9 is a schematic plan view for explaining light extraction characteristics according to a substrate shape.
10 is a graph showing the orientation angle characteristics of the flip chip type light emitting diode manufactured according to the conventional technology and the flip chip type light emitting diode manufactured according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

First, a method of manufacturing a light emitting diode will be described in order to facilitate understanding of the structure of a flip chip type light emitting diode according to an embodiment of the present invention.

FIGS. 1 to 5 are views for explaining a method of manufacturing a light emitting diode according to an embodiment of the present invention, wherein (a) is a plan view and (b) is a cross-sectional view taken along the cutting line A-A.

1, a first conductive semiconductor layer 23 is formed on a substrate 21, and an active layer 25 and a second conductive semiconductor layer 23 are formed on the first conductive semiconductor layer 23 27) are located. The substrate 21 may be a sapphire substrate, a silicon carbide substrate, or a gallium nitride substrate, in particular, a sapphire substrate, for growing a gallium nitride semiconductor layer. The substrate 21 may be provided in the form of a wafer having a large area capable of manufacturing a plurality of light emitting diodes. In FIG. 1, only the substrate portion of the final light emitting diode after separated into individual light emitting diodes is shown. In the final light emitting diode, the substrate 21 may have a parallelogram shape with an acute angle, for example, a rhombus shape, but it is not limited thereto, and may be various polygonal shapes such as triangular, pentagonal, and the like.

A mesa is formed on the first conductivity type semiconductor layer 23 and a portion of the first conductivity type semiconductor layer 23 is exposed along the edge of the mesa. The upper surface of the first conductivity type semiconductor layer 23 may be exposed along the edge of the substrate 21 of the final light emitting diode and the active layer 25 and the second conductivity type semiconductor layer 27 May be confined within the upper region of the first conductivity type semiconductor layer 23.

The mesa is formed by stacking a semiconductor laminated structure 26 including a first conductive type semiconductor layer 23, an active layer 25 and a second conductive type semiconductor layer 27 on a first surface of a substrate 21, And may be formed by patterning the second conductivity type semiconductor layer 27 and the active layer 25 so that the first conductivity type semiconductor layer 23 is exposed. The side of the mesa can be formed obliquely by using a technique such as photoresist reflow. The inclined profile of the mesa side improves the extraction efficiency of the light generated in the active layer 25. The planar shape of the mesa is similar to the planar shape of the substrate 21.

On the other hand, the reflective electrode 30 is formed on the second conductivity type semiconductor layer 27. The reflective electrode 30 may be formed on the mesa after the mesa is formed. Alternatively, the reflective electrode 30 may be formed on the mesa of the second conductivity type semiconductor layer 27 27). The reflective electrode 30 covers most of the upper surface of the second conductivity type semiconductor layer and has substantially the same shape as the planar shape of the mesa.

The reflective electrode 30 includes a reflective layer 28, and may further comprise a barrier layer 29. The barrier layer 29 may cover the top and side surfaces of the reflective layer 28. For example, the barrier layer 29 may be formed to cover the upper surface and the side surface of the reflective layer 28 by forming a pattern of the reflective layer 28 and forming a barrier layer 29 thereon. For example, the reflective layer 28 may be formed by depositing and patterning Ag, Ag alloy, Ni / Ag, NiZn / Ag, and TiO / Ag layers. On the other hand, the barrier layer 29 may be formed of Ni, Cr, Ti, Pt or a composite layer thereof to prevent diffusion or contamination of the metal material of the reflection layer 28.

Referring to FIG. 2, a lower insulating layer 31 covering the first conductivity type semiconductor layer 23 and the reflective electrode 30 is formed. The lower insulating layer 31 has openings 31a and 31b for allowing electrical connection to the first conductivity type semiconductor layer 23 and the second conductivity type semiconductor layer 27 in a specific region. For example, the lower insulating layer 31 may have openings 31a for exposing the first conductivity type semiconductor layer 23 and openings 31b for exposing the reflective electrode 30.

The opening 31a may be located near the edge of the substrate 21 around the reflective electrode 30 and may have an elongated shape extending along the edge of the substrate 21. [ As shown in Fig. 2, the openings 31a are formed so as to be farther away from each other at the corner portions than at the obtuse angles. On the other hand, the opening 31b is located on the upper portion of the reflective electrode 30 and can be positioned near the corner of the substrate 21.

The lower insulating layer 31 may be formed of an oxide film such as SiO ₂ , a nitride film such as SiNx, or an insulating film of MgF ₂ using a technique such as chemical vapor deposition (CVD). The lower insulating layer 31 may be formed of a single layer, but is not limited thereto and may be formed of multiple layers. Further, the lower insulating layer 31 may be formed of a distributed Bragg reflector (DBR) in which a low refractive index material layer and a high refractive index material layer are alternately laminated. For example, an insulating reflection layer having a high reflectance can be formed by laminating SiO ₂ / TiO ₂ or SiO ₂ / Nb ₂ O ₅ layers.

In the present embodiment, the opening 31a for exposing the first conductivity type semiconductor layer 23 has an elongated shape and is formed along the edge of the substrate 21. However, the present invention is not limited thereto. For example, as shown in Fig. 6, a plurality of holes 31c for exposing the first conductivity type semiconductor layer 23 may be arranged along the edge of the substrate 21. [ At this time, it is preferable that the plurality of holes 31c are arranged so as to be distant from each other as they approach the corners of the stator.

Referring to FIG. 3, a current spreading layer 33 is formed on the lower insulating layer 31. The current dispersion layer 33 covers the reflective electrode 30 and the first conductivity type semiconductor layer 23. The current spreading layer 33 has an opening 33a located in the region above the reflective electrode 30 and exposing the reflective electrode 30. The current spreading layer 33 may be in ohmic contact with the first conductivity type semiconductor layer 23 through the openings 31a of the lower insulating layer 31. [ On the other hand, the current-spreading layer 33 is insulated from the reflective electrode 30 by the lower insulating layer 31.

The opening 33a of the current dispersion layer 33 has a larger area than the opening 31b of the lower insulating layer 31 so as to prevent the current dispersion layer 33 from connecting to the reflective electrode 30. [ Therefore, the side wall of the opening 33a is located on the lower insulating layer 31. [

The current spreading layer 33 is formed on almost the entire region of the substrate 31 except for the opening 33a. Therefore, the current can be easily dispersed through the current dispersion layer 33. The current spreading layer 33 may include a highly reflective metal layer such as an Al layer and the highly reflective metal layer may be formed on an adhesive layer such as Ti, Cr, or Ni. Further, a protective layer of a single layer or a multiple layer structure such as Ni, Cr, Au or the like may be formed on the highly reflective metal layer. The current-spreading layer 33 may have a multilayer structure of Ti / Al / Ti / Ni / Au, for example.

Referring to FIG. 4, an upper insulating layer 35 is formed on the current spreading layer 33. The upper insulating layer 35 has an opening portion 35b for exposing the reflective electrode 30 together with an opening portion 35a for exposing the current dispersion layer 33. [ The opening 35a and the opening 35b may be disposed opposite to each other and may be disposed near the acute portions of the substrate 21 as shown in Fig. 4 (a). The opening 35b exposes the exposed reflective electrode 30 through the opening 33a of the current spreading layer 33 and the opening 31b of the lower insulating layer 31. [ The opening 35b has a smaller area than the openings 33a of the current-spreading layer 33. [ Thus, the side wall of the opening 33a of the current-spreading layer 33 is covered with the upper insulating layer 35. [ On the other hand, the opening 35b may have a smaller area than the opening 31b of the lower insulating layer 31, but it is not limited thereto and may have a wider area.

The upper insulating layer 35 may be formed using an oxide insulating layer, a nitride insulating layer, or a polymer such as polyimide, Teflon, or parylene.

Referring to FIG. 5, a first pad 37a and a second pad 37b are formed on the upper insulating layer 35. Referring to FIG. The first pad 37a is connected to the current spreading layer 33 through the opening 35a of the upper insulating layer 35 and the second pad 37b is connected to the current spreading layer 33 through the opening 35b of the upper insulating layer 35 And is connected to the reflective electrode 30. The first pad 37a and the second pad 37b may be used as pads for connecting SMTs or connecting bumps for mounting the light emitting diode on a submount, a package, a printed circuit board, or the like.

The first and second pads 37a and 37b may be formed together in the same process and may be formed using, for example, a photo and etch technique or a lift-off technique. The first and second pads 37a and 37b may include, for example, an adhesive layer of Ti, Cr, Ni, or the like and a high-conductivity layer of metal such as Al, Cu, Ag, or Au. In addition, the first and second pads 37a and 37b may further include a pad barrier layer covering the high-conductivity metal layer. The barrier metal layer prevents diffusion of metal atoms such as tin (Sn) during the bonding or soldering process to prevent the resistivity of the first and second pads 37a and 37b from increasing. The pad barrier layer may be formed of Cr, Ni, Ti, W, TiW, Mo, Pt, or a composite layer thereof.

Thereafter, the substrate 21 is divided into individual LED chip units to complete the light emitting diode. The substrate 21 can be divided into discrete light emitting diode chip units of a parallelogram shape by scribing, for example, along the m plane group. Accordingly, a light emitting diode in which the side surfaces of the substrate 21 are m-plane groups can be provided.

On the other hand, the substrate 21 may be deformed to have a thinner thickness through a thinning process before being divided into individual LED chip units. At this time, the thickness of the substrate 21 may exceed 100 탆, and may be 225 탆 or more and 400 탆 or less.

On the other hand, a conformal coating (50 in FIG. 8) covering the substrate 21 of the individual LED chip may be additionally formed. Conformal coating 50 may be formed before or after dividing substrate 21 into chip units.

Hereinafter, the structure of a light emitting diode 100 according to an embodiment of the present invention will be described in detail with reference to FIG.

7, the light emitting diode 100 includes a substrate 21, a first conductive semiconductor layer 23, an active layer 25, a second conductive semiconductor layer 27, a first pad 37a, And a second pad 37b and may include a reflective electrode 30, a current spreading layer 33, a lower insulating layer 31, and an upper insulating layer 35. [

The substrate 21 may be a growth substrate for growing gallium nitride-based epitaxial layers, such as sapphire, silicon carbide, or gallium nitride. The substrate 21 may include a first surface 21a, a second surface 21b, and a side surface 21c. The first surface 21a is a surface on which semiconductor layers are grown and the second surface 21b is a surface on which light generated in the active layer 25 is emitted to the outside. The side surface 21c connects the first surface 21a and the second surface 21b. The side surface 21c of the substrate 21 may be a surface perpendicular to the first surface 21a and the second surface 21b, but it is not limited thereto and may be a tilted surface. For example, the substrate 21 may have an inclined side surface 21d such that the first surface 21a has a wider area than the second surface 21b, such as a side surface 21d indicated by a dotted line in Fig.

In addition, the substrate 21 may be in the form of a polygon having at least one acute angle. For example, the first surface 21a and the second surface 21b may have a polygonal shape such as a parallelogram, a triangle, or a pentagon, as described with reference to Fig. Since the substrate 21 has an acute angle, the extraction efficiency of light through the acute-angled portion is improved, and the directivity angle of light at the corner portions can be increased.

On the other hand, in the present embodiment, the thickness of the substrate 21 may exceed 100 mu m, and in particular may have a value in the range of 225 mu m to 400 mu m. The directing angle of light can be increased as the thickness of the substrate 21 is larger, and the directivity angle of the light can be kept substantially constant when the thickness of the substrate 21 is 225 탆 or more.

The first conductive type semiconductor layer 23 is located on the first surface 21a of the substrate 21. The first conductive semiconductor layer 23 may cover the entire surface of the first surface 21a of the substrate 21 so that the first surface 21a is exposed along the edge of the substrate 21 The first conductivity type semiconductor layer 23 may be located within the upper region of the substrate 21.

A mesa including the active layer 25 and the second conductivity type semiconductor layer 27 is located on the first conductivity type semiconductor layer 23. In particular, the active layer 25 and the second conductivity type semiconductor layer 27 are located within the upper region of the first conductivity type semiconductor layer 27 as described with reference to Fig. Therefore, a part of the region of the first conductivity type semiconductor layer 27 can be exposed along the edge of the substrate 21 in particular.

The reflective electrode 30 is in ohmic contact with the second conductivity type semiconductor layer 27. The reflective electrodes 30 may include a reflective layer 28 and a barrier layer 29 as described with reference to FIG. 1 and a barrier layer 29 may cover the top and sides of the reflective layer 28.

The current dispersion layer 33 covers the reflective electrode 30 and the first conductivity type semiconductor layer 23. The current spreading layer 33 has an opening 33a located in the upper region of the reflective electrode 30 and exposing the reflective electrode 30. [ The current spreading layer 33 may cover the entire area of the reflective electrode 30 except for a part of the upper region of the reflective electrode 30 where the opening 33a is formed and the first conductivity type semiconductor layer 23 ). ≪ / RTI >

The current-spreading layer 33 is also in ohmic contact with the first conductivity type semiconductor layer 23 and is insulated from the reflective electrode 30. For example, the current-spreading layer 33 may be insulated from the reflective electrode 30 by the lower insulating layer 31. [ The lower insulating layer 31 can be positioned between the reflective electrode 30 and the current dispersion layer 33 to isolate the current dispersion layer 33 from the reflective electrode 30. [

The lower insulating layer 31 may have openings 31b that are located in the upper region of the reflective electrode 30 and expose the reflective electrode 30 and openings 31b that expose the first conductive semiconductor layer 23 Lt; RTI ID = 0.0 > 31a. ≪ / RTI > The opening 31b of the lower insulating layer 31 has an area narrower than the opening 33a of the current spreading layer 33 and is entirely exposed by the opening 33a.

On the other hand, the current-spreading layer 33 can be connected to the first conductivity type semiconductor layer 23 through the openings 31a. Here, the openings 31a may be located along the edges of the substrate 21 as described with reference to FIG. 2, and may be farther away from the corners than at the obtuse angles. Accordingly, it is possible to prevent the current from concentrating at the corner portions and improve the luminous efficiency. In addition, the lower insulating layer 31 may have holes 31c as described with reference to Fig. 6 instead of the openings 31a.

The upper insulating layer 35 covers at least a part of the current-spreading layer 33. The upper insulating layer 35 has an opening portion 35a for exposing the current dispersion layer 33 and an opening portion 35b for exposing the reflective electrode 30. The opening 35a and the opening 35b may be located near the acute angles with respect to each other. The upper insulating layer 35 may cover the side wall of the opening 33a of the current spreading layer 33 and the opening 35b may be located within the opening 33a.

The first pad 37a may be located on the current spreading layer 33 and may be connected to the current spreading layer 33 through the opening 35a of the upper insulating layer 35, for example. The first pad 37a is electrically connected to the first conductive type semiconductor layer 23 through the current dispersion layer 33. [ The second pad 37b is connected to the reflective electrode 30 exposed through the opening 35b and is electrically connected to the second conductivity type semiconductor layer 27 through the reflective electrode 30. [

According to the present embodiment, the light extraction efficiency can be improved by making the substrate 21 have a parallelogram shape or a polygonal shape having at least one acute angle like a triangle shape. Further, since the luminous flux emitted through the acute-angled portion increases, it is possible to control the directivity characteristics of the LED using the acute angle portion.

In the present embodiment, the thickness of the substrate 21 is set to 100 mu m or more to increase the light directing angle.

The current dispersion layer 23 includes a reflective metal layer such as Al or the lower insulating layer is formed of an insulating reflection layer so that the light that is not reflected by the reflective electrodes 30 is separated from the current dispersion layer 23 or the lower insulating layer 23. [ Layer 31, so that the light extraction efficiency can be improved.

8 is a cross-sectional view illustrating a light emitting diode 200 according to another embodiment of the present invention.

The light emitting diode 200 according to this embodiment is substantially similar to the light emitting diode 100 of FIG. 7, but differs in that the conformal coating 50 is located on the substrate 21. The conformal coating 50 covers the second surface 21b of the substrate 21 to a uniform thickness and can also cover the side surface 21c. Conformal coating 50 may comprise a wavelength converting material such as a phosphor.

Further, the sum of the thickness of the substrate 21 and the thickness of the conformal coating 50 may be 225 탆 or more, and may be 600 탆 or less. For example, the thickness of the conformal coating 50 may have a value in the range of 20 占 퐉 to 200 占 퐉. In addition, the thickness of the substrate 21 may vary depending on the thickness of the conformal coating, and may have a value in the range of, for example, 100 mu m to 400 mu m. When the sum of the thicknesses of the substrate 21 and the conformal coating 50 is 225 탆 or more, the directivity angle of the light emitting diode 200 can be increased to 140 degrees or more.

9 is a schematic plan view for explaining light extraction characteristics according to a substrate shape. (A) is a view showing a progress path of light in a conventional rectangular substrate 11, (b) is a view showing a light path in a diamond-shaped substrate 21 having acute angle portion according to an embodiment of the present invention FIG.

Referring to FIG. 9A, a part of light generated at a specific position Lp of the active layer enters the substrate 11, and then repeats total internal reflection at the side surfaces of the substrate 11. As a result, light travels a considerable distance inside the substrate 11, and therefore light loss occurs in the substrate 11. The greater the thickness of the substrate 11, the more total internal reflection takes place on the side of the substrate 11, thereby increasing the light loss. Furthermore, since the light emitted from the respective parts of the substrate 11 is similar to each other, the directivity angle along the direction is constant without any significant difference.

On the other hand, in the case of the diamond-like substrate 21 shown in FIG. 9 (b), a part of the light generated at the specific position Lp of the active layer enters the substrate 21, After total internal reflection at the side surfaces, the incidence angle of light is generally reduced near the corners of the sample and is emitted to the outside. Therefore, by adopting the diamond-like substrate 21, the light extraction efficiency is improved as compared with the case where the conventional substrate 11 is adopted. Further, since the light extraction efficiency is increased at the corner portions, the directivity angle of the light increases at the corner portions in comparison with the dull corner portions. Therefore, it is possible to provide a light emitting diode in which the directional angle characteristics are different depending on the direction.

10 is a graph showing the orientation angle of a flip chip type light emitting diode manufactured according to a conventional technique and a flip chip type light emitting diode manufactured according to an embodiment of the present invention. Here, the substrate 11 of the light emitting diode manufactured according to the related art had a rectangular shape of 300 mu m x 1000 mu m, and the thickness thereof was approximately 250 mu m. Meanwhile, in the light emitting diode manufactured according to an embodiment of the present invention, the length of the substrate 21 between the acute angles was 1 mm and the length between the obtuse angles was about 0.58 mm.

Referring to FIG. 10, the LED according to the related art is substantially similar in the directional angle distribution R-X along the x-axis (short axis) direction and the directivity angle distribution R-Y along the y-axis (long axis) direction. In contrast, the light emitting diode according to an embodiment of the present invention has a relatively smaller directivity angle distribution DY along the y-axis direction passing through the acute angle portions than the directivity angle distribution DX along the x-axis direction passing through the obtuse- It appears large.

Therefore, according to the embodiment of the present invention, it is possible to provide a light emitting diode having different directivity angle characteristics in the x-axis direction and the y-axis direction. Such a light emitting diode can be usefully used particularly in an illuminating device, such as an LED fluorescent lamp, which requires different directional characteristics depending on the direction. For example, a plurality of light emitting diodes may be arranged in a row so that the y-axis direction having a wide directing angle is orthogonal to the longitudinal direction of the LED fluorescent lamp. Accordingly, a large area can be illuminated have.

Claims (20)

A transparent substrate having a first side, a second side and a side connecting the first side and the second side;
A first conductive semiconductor layer located on a first surface of the transparent substrate;
A second conductive semiconductor layer disposed on the first conductive semiconductor layer;
An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer;
A first pad electrically connected to the first conductive semiconductor layer; And
And a second pad electrically connected to the second conductive type semiconductor layer,
The light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate,
Wherein the transparent substrate is a polygonal shape having at least one acute angle. The method according to claim 1,
Wherein the transparent substrate has a thickness within a range of 100 mu m to 400 mu m. The method of claim 2,
Wherein the polygonal shape having at least one acute angle is a triangular shape, a parallelogram shape, or a pentagonal shape. The method according to claim 1,
Wherein the transparent substrate is a sapphire substrate. The method of claim 4,
Wherein the transparent substrate has a parallelogram shape and the side surface of the transparent substrate is an m-plane group. The light emitting diode of claim 1, further comprising a reflective electrode positioned on the second conductivity type semiconductor layer and reflecting light generated in the active layer. The method according to any one of claims 1 to 6,
Wherein the active layer and the second conductivity type semiconductor layer are confined within an upper region of the first conductivity type semiconductor layer such that an upper surface of the first conductivity type semiconductor layer is exposed along an edge of the substrate. The method of claim 7,
And a current spreading layer connecting the first pad and the first conductive type semiconductor layer,
Wherein the first pad and the second pad are disposed on the second conductive type semiconductor layer. The method of claim 8,
Wherein the current dispersion layer comprises a reflective metal. The method of claim 8,
And a lower insulating layer for insulating the current dispersion layer from the reflective electrode,
Wherein the lower insulating layer has openings for exposing the first conductivity type semiconductor layer,
And the current spreading layer is connected to the first conductive type semiconductor layer through the openings. The method of claim 10,
The openings are each arranged in an elongated shape along the edges of the substrate,
Wherein the openings are further away from the at least one example corner than the other sides. The method of claim 10,
Wherein the openings comprise a plurality of holes spaced apart along an edge of the substrate,
And the spacing between the holes increases toward the at least one corner portion. The method according to claim 1,
Wherein the side face is inclined such that the first face has a wider area than the second face. The method according to claim 1,
And a conformal coating covering the second surface of the substrate. 15. The method of claim 14,
Wherein the sum of the thicknesses of the transparent substrate and the conformal coating has a value within a range of 225 mu m to 600 mu m. In a lighting apparatus including a plurality of light emitting diodes,
At least one light emitting diode,
A transparent substrate having a first side, a second side and a side connecting the first side and the second side;
A first conductive semiconductor layer located on a first surface of the transparent substrate;
A second conductive semiconductor layer disposed on the first conductive semiconductor layer;
An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer;
A first pad electrically connected to the first conductive semiconductor layer; And
And a second pad electrically connected to the second conductive type semiconductor layer,
The light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate,
Wherein the transparent substrate has a polygonal shape with at least one acute angle. 15. The method of claim 14,
Wherein the transparent substrate has a thickness within a range of 100 mu m to 400 mu m. 15. The method of claim 14,
Wherein the polygonal shape having at least one acute angle is a triangular shape, a parallelogram shape, or a pentagonal shape. 19. The method of claim 18,
Wherein the transparent substrate has a parallelogram shape and the side surface of the transparent substrate is an m-plane group. The method of claim 19,
Wherein the at least one light emitting diode further comprises a conformal coating covering the second surface of the transparent substrate,
Wherein the sum of the thicknesses of the transparent substrate and the conformal coating has a value within a range of 225 mu m to 600 mu m.

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