KR102013364B1 - Light emitting diode and application thereof - Google Patents

Abstract

A light emitting diode and its application are disclosed. The light emitting diode includes a transparent substrate having a first surface, a second surface, and a side surface, a first conductive semiconductor layer positioned on the first surface of the transparent substrate, and a second conductive semiconductor layer positioned on the first conductive semiconductor layer. An electrically conductive semiconductor layer, an active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer, a first pad electrically connected to the first conductive semiconductor layer, and an electrically conductive second layer And a second pad connected with. In addition, 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 light emitting diode has a directing angle of 140 degrees or more in at least one axial direction. Therefore, a light emitting diode suitable for a backlight unit or a surface lighting apparatus can be provided.

Description

LIGHT EMITTING DIODE AND APPLICATION THEREOF

TECHNICAL FIELD The present invention relates to light emitting diodes and their applications, and more particularly to flip chip type light emitting diodes having improved directivity angles and their applications.

Since the development of gallium nitride (GaN) -based light emitting diodes, GaN-based LEDs have been used in a variety of applications, including color LED display devices, LED traffic signals, backlight units, and lighting devices.

A gallium nitride-based light emitting diode is generally formed by growing epi layers on a substrate such as sapphire, and includes an N-type semiconductor layer, a P-type semiconductor layer, and an active layer interposed therebetween. Meanwhile, 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 and driven by an external power source through electrode pads. At this time, current flows from the P-electrode pad to the N-electrode pad via the semiconductor layers.

On the other hand, a light emitting diode having a flip chip structure is used to prevent light loss caused by the P-electrode pad and to improve heat dissipation efficiency. Since the flip-chip light emitting diode emits light through the growth substrate, light loss due to the P-electrode pad can be reduced compared to the light emitting diode of the horizontal structure emitting light to the outside through the epitaxial layer.

In addition, in order to increase the light extraction efficiency, a light emitting diode having a vertical structure for removing a growth substrate such as sapphire from the epi layer has been developed. In particular, the light emitting diode having the vertical structure may prevent light loss due to total internal reflection by texturing the exposed surface of the semiconductor layer.

On the other hand, in particular applications, especially in applications where it is necessary to irradiate light in a large area such as a backlight unit or a surface lighting device, the directing angle of the light source is an important concern.

However, the light emitting diode of the flip-chip structure according to the prior art generally has a direction angle of about 120 degrees, and the light emitting diode of the vertical structure generally has a direction angle smaller than about 120 degrees by surface texturing. Accordingly, efforts have been made to increase the directing angle of light by using a molding part at a package level or by using a separately manufactured secondary lens.

SUMMARY OF THE INVENTION An object of the present invention is to provide a flip chip type light emitting diode suitable for a backlight unit or a surface lighting device and an application thereof.

Another object of the present invention is to provide a flip chip type light emitting diode which can improve light extraction efficiency by increasing reflectance.

Another object of the present invention is to provide a flip chip type light emitting diode having improved current spreading performance.

According to an aspect of the present invention, there is provided a light emitting diode comprising: a transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface; A first conductivity type semiconductor layer on the first surface of the transparent substrate; A second conductivity type semiconductor layer on the first conductivity type semiconductor layer; An active layer positioned 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. In addition, light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate. Furthermore, the light emitting diode has a directing angle of 140 degrees or more in at least one axial direction.

Unlike conventional light emitting diodes, the light emitting diode according to the present embodiments has a relatively wide direct angle of 140 degrees or more without using a lens-shaped molding member or a secondary lens. Therefore, it is suitable for lighting apparatuses, such as a backlight unit and a surface lighting apparatus. The light emitting diode according to the present embodiments may be directly applied to an application without performing a separate packaging process. Furthermore, the light emitting diode may be used without or in combination with a secondary lens.

In some embodiments, the light emitting diode may further include a conformal coating layer covering the second surface of the transparent substrate. Light emitted from the second surface is emitted to the outside of the conformal coating layer through the conformal coating layer. The conformal coating layer may contain phosphors and thus may wavelength convert at least some of the light generated in the active layer.

The sum of the thicknesses of the transparent substrate and the conformal coating layer may have a value within the range of 225 μm to 600 μm. Further, the thickness of the transparent substrate may have a value within the range of 150㎛ 400㎛. In addition, the thickness of the conformal coating may have a value within the range of 20㎛ to 200㎛.

In some embodiments, the thickness of the transparent substrate may have a value in the range of 225 μm to 400 μm. By setting the thickness of the transparent substrate within a range of 225 μm to 400 μm, a flip chip light emitting diode having a directivity angle of 140 degrees or more can be provided regardless of the presence or absence of a conformal coating layer. When the thickness of the transparent substrate exceeds 400 μm, it is difficult to separate the substrate into individual light emitting diode chips.

The light emitting diode may further include a plurality of mesas spaced apart from each other on the first conductivity type semiconductor layer. Each mesa includes the active layer and the second conductive semiconductor layer.

Further, the light emitting diodes may include: reflective electrodes positioned on the plurality of mesas and ohmic contact with a second conductive semiconductor layer; And openings covering the plurality of mesas and the first conductivity type semiconductor layer, the openings being located in the upper region of each mesa and exposing the reflective electrodes, ohmic contacting the first conductivity type semiconductor layer, and the plurality of mesas. It may further include a current spreading layer insulated from them. The first pad may be electrically connected to the current spreading layer, and the second pad may be electrically connected to the reflective electrodes through the openings.

Since the current spreading layer covers the plurality of mesas and the first conductivity type semiconductor layer, the current spreading performance is improved through the current spreading layer.

The first conductivity type semiconductor layer may be continuous. In addition, the plurality of mesas may have an elongated shape extending in parallel to each other in one direction. Openings of the current spreading layer may be located at the same end side of the plurality of mesas. Therefore, a pad connecting the reflective electrodes exposed to the openings of the current spreading layer can be easily formed.

The current spreading layer may include a reflective metal such as Al. Accordingly, in addition to the light reflection by the reflective electrodes, the light reflection by the current spreading layer can be obtained, and thus, the light traveling through the plurality of mesas sidewalls and the first conductivity type semiconductor layer can be reflected.

The reflective electrodes may each include a reflective metal layer and a barrier metal layer. Further, the barrier metal layer may cover the top and side surfaces of the reflective metal layer. As a result, the reflective metal layer can be prevented from being exposed to the outside, and deterioration of the reflective metal layer can be prevented.

The light emitting diode includes: an upper insulating layer covering at least a portion of the current spreading layer and having openings exposing the reflective electrodes; And a second pad disposed on the upper insulating layer and connected to the reflective electrodes exposed through the openings of the upper insulating layer.

In addition, the first pad and the second pad may be formed in the same shape and size, and thus flip chip bonding may be easily performed.

The light emitting diode may further include a lower insulating layer positioned between the plurality of mesas and the current spreading layer to insulate the current spreading layer from the plurality of mesas. The lower insulating layer may have openings positioned in the upper mesas and exposing the reflective electrodes.

Further, each of the openings of the current spreading layer may have a wider width than the openings of the lower insulating layer so that all of the openings of the lower insulating layer are exposed. That is, sidewalls of the openings of the current spreading layer are located on the lower insulating layer. In addition, the light emitting diode may further include an upper insulating layer covering at least a portion of the current spreading layer and having openings exposing the reflective electrodes. The upper insulating layer may cover sidewalls of the openings of the current spreading layer.

The lower insulating layer may be a reflective dielectric layer, such as a distributed Bragg reflector (DBR).

According to another aspect of the present invention, a light emitting diode includes: a transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface; A first conductivity type semiconductor layer on the first surface of the transparent substrate; A second conductivity type semiconductor layer on the first conductivity type semiconductor layer; An active layer positioned 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. In addition, the light generated in the active layer is emitted to the outside through the second surface of the transparent substrate, the thickness of the transparent substrate has a value in the range of 225㎛ to 400㎛.

According to another aspect of the present invention, there is provided a light emitting diode comprising: a transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface; A first conductivity type semiconductor layer on the first surface of the transparent substrate; A second conductivity type semiconductor layer on the first conductivity type semiconductor layer; An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer; A first pad electrically connected to the first conductive semiconductor layer; A second pad electrically connected to the second conductive semiconductor layer; And a conformal coating layer covering the transparent substrate. In addition, the light generated in the active layer is emitted to the outside through the conformal coating layer, the sum of the thickness of the transparent substrate and the conformal coating has a value in the range of 225㎛ to 600㎛.

Further, the thickness of the transparent substrate may have a value within the range of 150㎛ 400㎛. Alternatively, the thickness of the conformal coating may have a value within the range of 20 μm to 200 μm.

An illumination module according to another aspect of the invention comprises a plurality of light emitting diodes, at least one light emitting diode having a first side, a second side and a side connecting the first side and the second side Board; A first conductivity type semiconductor layer on the first surface of the transparent substrate; A second conductivity type semiconductor layer on the first conductivity type semiconductor layer; An active layer positioned 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. In addition, light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate. Furthermore, the at least one light emitting diode has a directing angle of at least 140 degrees in at least one axial direction.

The thickness of the transparent substrate may have a value within the range of 225㎛ to 400㎛.

Furthermore, the at least one light emitting diode may further include a conformal coating layer covering the second surface of the transparent substrate. The sum of the thicknesses of the transparent substrate and the conformal coating may have a value within the range of 225 μm to 600 μm. Here, the thickness of the conformal coating may have a value within the range of 20㎛ to 200㎛.

According to another aspect of the invention, there is provided a lighting device comprising a lighting module. The lighting module has a plurality of light emitting diodes including at least one light emitting diode as described above.

According to another aspect of the present invention, a backlight unit includes a plurality of light emitting diodes, wherein at least one light emitting diode has a first surface, a second surface, and a side surface connecting the first surface and the second surface. Board; A first conductivity type semiconductor layer on the first surface of the transparent substrate; A second conductivity type semiconductor layer on the first conductivity type semiconductor layer; An active layer positioned 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. In addition, light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate. The at least one light emitting diode has a directing angle of at least 140 degrees in at least one axial direction.

The thickness of the transparent substrate may have a value within the range of 225㎛ to 400㎛.

In addition, the at least one light emitting diode may further include a conformal coating layer covering the second surface of the transparent substrate, the sum of the thickness of the transparent substrate and the conformal coating has a value within the range of 225㎛ to 600㎛ Can have In addition, the thickness of the conformal coating may have a value within the range of 20㎛ to 200㎛.

According to embodiments of the present invention, a flip chip type light emitting diode having a relatively wide orientation angle is provided. Therefore, it can be used suitably for a backlight unit or a surface lighting apparatus. In particular, when the light emitting diodes having the wide directivity are arranged, the number of use of the light emitting diodes may be reduced or the backlight unit or the lighting module may be slimmed.

In addition, according to embodiments of the present invention, it is possible to provide a flip chip light emitting diode that can improve the light extraction efficiency by increasing the reflectance, it is possible to provide a flip chip light emitting diode having improved current dispersion performance.

1 to 5 are views for explaining a light emitting diode manufacturing method according to an embodiment of the present invention, (a) is a cross-sectional view taken along the cutting line AA (b) in each of the drawings.
6 is a plan view for explaining a modification of the mesa structure.
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 for describing a light emitting diode according to still another embodiment of the present invention.
9 to 12 are graphs showing directivity of light emitting diodes at various substrate thicknesses.
13 is a graph showing the directivity angles of light emitting diodes according to the thickness of the substrate.
14 to 17 are graphs showing directivity of light emitting diodes with conformal coatings at various substrate thicknesses.
18 is a graph showing the directivity angles of light emitting diodes with conformal coating according to substrate thickness.
19 is a schematic cross-sectional view illustrating a light emitting diode module employing conventional light emitting diodes and a light emitting diode module employing light emitting diodes according to 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 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. Like numbers refer to like elements throughout.

First, a light emitting diode manufacturing method will be described first to help understand the structure of a flip chip type light emitting diode according to an embodiment of the present invention.

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

First, referring to FIG. 1, a first conductivity type semiconductor layer 23 is formed on a substrate 21, and an active layer 25 and a second conductivity type semiconductor layer (on the first conductivity type semiconductor layer 23). 27) is located. The substrate 21 is a substrate for growing a gallium nitride based semiconductor layer, for example, may be a sapphire substrate, a silicon carbide substrate, or a gallium nitride substrate, and in particular, may be a sapphire substrate.

A plurality of mesas M spaced apart from each other may be formed on the first conductive semiconductor layer 23, and the plurality of mesas M may be the active layer 25 and the second conductive semiconductor layer 27, respectively. It may include. The active layer 25 is positioned between the first conductive semiconductor layer 23 and the second conductive semiconductor layer 27. Meanwhile, the reflective electrodes 30 are located on the plurality of mesas M, respectively.

The plurality of mesas M may include an epitaxial layer including the first conductive semiconductor layer 23, the active layer 25, and the second conductive semiconductor layer 27 on the first surface of the substrate 21. After growing using a vapor phase growth method or the like, the second conductive semiconductor layer 27 and the active layer 25 may be patterned to expose the first conductive semiconductor layer 23. Sides of the plurality of mesas M may be formed to be inclined by using a technique such as photoresist reflow. The inclined profile of the mesa (M) side improves the extraction efficiency of the light generated in the active layer 25.

The plurality of mesas M may have an elongated shape extending in parallel to each other in one direction as shown. This shape simplifies forming a plurality of mesas M of the same shape in the plurality of chip regions on the substrate 21.

Meanwhile, the reflective electrodes 30 may be formed on each mesa M after the plurality of mesas M are formed, but is not limited thereto. The second conductive semiconductor layer 27 may be grown and mesas. It may be formed in advance on the second conductivity-type semiconductor layer 27 before forming (M). The reflective electrode 30 covers most of the upper surface of the mesa M, and has a shape substantially the same as the planar shape of the mesa M. FIG.

The reflective electrodes 30 may include a reflective layer 28 and may further include a barrier layer 29. The barrier layer 29 may cover the top and side surfaces of the reflective layer 28. For example, by forming a pattern of reflective layer 28 and forming barrier layer 29 thereon, barrier layer 29 can be formed to cover the top and side surfaces of reflective layer 28. For example, the reflective layer 28 may be formed by depositing and patterning an Ag, Ag alloy, Ni / Ag, NiZn / Ag, TiO / Ag layer. Meanwhile, the barrier layer 29 may be formed of Ni, Cr, Ti, Pt, or a composite layer thereof, and prevents the metal material of the reflective layer from being diffused or contaminated.

After the plurality of mesas M are formed, an edge of the first conductivity type semiconductor layer 23 may also be etched. Accordingly, the upper surface of the substrate 21 may be exposed. Side surfaces of the first conductive semiconductor layer 23 may also be formed to be inclined.

As shown in FIG. 1, the plurality of mesas M may be formed so as to be limitedly positioned inside the upper region of the first conductivity-type semiconductor layer 23. That is, the plurality of mesas M may be located in an island shape on the upper region of the first conductivity type semiconductor layer 23. In contrast, as shown in FIG. 6, mesas M extending in one direction may be formed to reach an upper edge of the first conductivity-type semiconductor layer 23. That is, the one side edge of the bottom surface of the plurality of mesas M coincides with the one side edge of the first conductivity type semiconductor layer 23. Accordingly, an upper surface of the first conductivity type semiconductor layer 23 is partitioned by the plurality of mesas M.

Referring to FIG. 2, a lower insulating layer 31 covering the plurality of mesas M and the first conductive semiconductor layer 23 is formed. The lower insulating layer 31 has openings 31a and 31b to allow electrical connection to the first conductive semiconductor layer 23 and the second conductive semiconductor layer 27 in a specific region. For example, the lower insulating layer 31 may have openings 31a exposing the first conductivity type semiconductor layer 23 and openings 31b exposing the reflective electrodes 30.

The openings 31a may be positioned near the edge between the mesas M and the edge of the substrate 21, and may have an elongated shape extending along the mesas M. On the other hand, the openings 31b are limited to the upper portion of the mesa M, and may be positioned to the same end side of the mesas.

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 as a single layer, but is not limited thereto and may be formed as a multilayer. Further, the lower insulating layer 31 may be formed of a distributed Bragg reflector (DBR) in which the low refractive material layer and the high refractive material layer are alternately stacked. For example, an insulating reflective layer having a high reflectance can be formed by laminating layers such as SiO ₂ / TiO ₂ or SiO ₂ / Nb ₂ O ₅ .

Referring to FIG. 3, a current spreading layer 33 is formed on the lower insulating layer 31. The current spreading layer 33 covers the plurality of mesas M and the first conductive semiconductor layer 23. In addition, the current spreading layer 33 has openings 33a located in the upper region of each mesa M and exposing the reflective electrodes 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. Meanwhile, the current spreading layer 33 is insulated from the plurality of mesas M and the reflective electrodes 30 by the lower insulating layer 31.

The openings 33a of the current spreading layer 33 have a larger area than the openings 31b of the lower insulating layer 31, respectively, to prevent the current spreading layer 33 from connecting to the reflective electrodes 30. Have Thus, sidewalls of the openings 33a are located on the lower insulating layer 31.

The current spreading layer 33 is formed over almost the entire area of the substrate 31 except for the openings 33a. Therefore, the current can be easily distributed through the current spreading layer 33. The current spreading layer 33 may include a high reflective metal layer such as an Al layer, and the high reflective metal layer may be formed on an adhesive layer such as Ti, Cr, or Ni. In addition, a protective layer of a single layer or a composite 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, for example, a multilayer structure of Ti / Al / Ti / Ni / Au.

Referring to FIG. 4, an upper insulating layer 35 is formed on the current spreading layer 33. The upper insulating layer 35 has openings 35b exposing the current spreading layer 33 and openings 35b exposing the reflective electrodes 30. The opening 35a may have an elongated shape in a direction perpendicular to the longitudinal direction of the mesa M, and has a relatively large area compared to the openings 35b. The openings 35b expose the reflective electrodes 30 exposed through the openings 33a of the current spreading layer 33 and the openings 31b of the lower insulating layer 31. The openings 35b may have a smaller area than the openings 33a of the current spreading layer 33, and may have a larger area than the openings 31b of the lower insulating layer 31. Accordingly, sidewalls of the openings 33a of the current spreading layer 33 may be covered by the upper insulating layer 35.

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

Referring to FIG. 5, a first pad 37a and a second pad 37b are formed on the upper insulating layer 35. The first pad 37a connects to the current spreading layer 33 through the opening 35a of the upper insulating layer 35, and the second pad 37b connects the openings 35b of the upper insulating layer 35. It is connected to the reflective electrodes 30 through. The first pad 37a and the second pad 37b may be connected to bumps or used as pads for SMT in order to mount a light emitting diode to a submount, package, or printed circuit board.

The first and second pads 37a and 37b may be formed together in the same process, for example, using photo and etching techniques or lift off techniques. The first and second pads 37a and 37b may include, for example, an adhesive layer such as Ti, Cr, or Ni, and a highly conductive metal layer such as Al, Cu, Ag, or Au.

Thereafter, the light emitting diode is completed by dividing the substrate 21 into individual light emitting diode chip units. The substrate 21 may be deformed to have a thinner thickness through a thinning process before being divided into individual LED chips.

Hereinafter, the structure of the 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 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. It may include reflective electrodes 30, current spreading layer 33, lower insulating layer 31, upper insulating layer 35 and mesas (M).

The substrate 21 may be a growth substrate for growing the gallium nitride-based epi layers, such as sapphire, silicon carbide, and gallium nitride substrate. 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 is not limited thereto and may be an inclined surface. For example, the substrate 21 may have an inclined side surface 21d such that the first surface 21a has a larger area than the second surface 21b, as shown by the dotted line 21d shown in FIG. 7. In the present embodiment, the thickness t1 of the substrate 21 may have a value within the range of 225 μm to 400 μm.

The first conductive semiconductor layer 23 is located on the first surface 21a of the substrate 21. The first conductive semiconductor layer 23 is continuous, and the active layer 25 and the second conductive semiconductor layer 27 are positioned on the first conductive semiconductor layer 23. In particular, the plurality of mesas M may be spaced apart from each other on the first conductivity type semiconductor layer 23. The mesas M include the active layer 25 and the second conductivity-type semiconductor layer 27 as described with reference to FIG. 1 and have an elongated shape extending toward one side. The mesas M may be a stacked structure of a gallium nitride compound semiconductor. Mesas M may be located within the upper region of the first conductivity-type semiconductor layer 23, as shown in FIG. On the contrary, as shown in FIG. 6, the mesas M may extend to one edge of the upper surface of the first conductivity-type semiconductor layer 23 in one direction, and thus the first conductivity-type semiconductor layer ( The upper surface of 23 may be partitioned into a plurality of regions. Accordingly, it is possible to alleviate the concentration of the current near the edge of the mesas (M) to further enhance the current distribution performance.

The reflective electrodes 30 are respectively positioned on the plurality of mesas M to make ohmic contact with the second conductive semiconductor layer 27. As described with reference to FIG. 1, the reflective electrodes 300 may include a reflective layer 28 and a barrier layer 29, and the barrier layer 29 may cover the top and side surfaces of the reflective layer 28.

The current spreading layer 33 covers the plurality of mesas M and the first conductive semiconductor layer 23. The current spreading layer 33 has openings 33a positioned in the upper region of each mesa M and exposing the reflective electrodes 30. The current spreading layer 33 may cover the entire area of the mesa M except for a part of the upper area of the mesa M in which the openings 33a are formed. It can cover the whole area. The current spreading layer 33 is also in ohmic contact with the first conductivity type semiconductor layer 23 and insulated from the plurality of mesas M. The current spreading layer 33 may include a reflective metal such as Al.

The current spreading layer 33 may be insulated from the plurality of mesas M by the lower insulating layer 31. For example, the lower insulating layer 31 may be positioned between the plurality of mesas M and the current spreading layer 33 to insulate the current spreading layer 33 from the plurality of mesas M. FIG. In addition, the lower insulating layer 31 may have openings 31b disposed in the upper region of each mesa M to expose the reflective electrodes 30, and may expose the first conductivity-type semiconductor layer 23. It may have openings 31a. The current spreading layer 33 may be connected to the first conductivity type semiconductor layer 23 through the openings 31a. The openings 31b of the lower insulating layer 31 have a smaller area than the openings 33a of the current spreading layer 33 and are all exposed by the openings 33a.

The upper insulating layer 35 covers at least a portion of the current spreading layer 33. In addition, the upper insulating layer 35 has openings 35b exposing the reflective electrodes 30. Furthermore, the upper insulating layer 35 may have an opening 35a exposing the current spreading layer 33. The upper insulating layer 35 may cover sidewalls of the openings 33a of the current spreading layer 33.

The first pad 37a may be positioned on the current spreading layer 33, and may be connected to the current spreading layer 33 through, for example, an opening 35a of the upper insulating layer 35. The first pad 37a is electrically connected to the first conductive semiconductor layer 23 through the current spreading layer 33. In addition, the second pad 37b is connected to the reflective electrodes 30 exposed through the openings 35b and electrically connected to the second conductive semiconductor layer 27 through the reflective electrodes 30. .

According to the present embodiment, since the substrate 21 has a thickness t1 of 225 µm or more, the directivity angle of the light emitting diode 100 can be increased to 140 degrees or more. In addition, since the current spreading layer 33 covers almost the entire area of the first conductivity-type semiconductor layer 23 between the mesas M and the mesas M, the current easily flows through the current spreading layer 33. Can be dispersed.

Furthermore, the current spreading layer 23 includes a reflective metal layer such as Al, or the lower insulating layer is formed as an insulating reflecting layer so that the light not reflected by the reflecting electrodes 30 is reflected by the current spreading layer 23 or the lower insulating layer. The layer 31 can be used for reflection to improve the light extraction efficiency.

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

The light emitting diode 200 according to the present embodiment is generally similar to the light emitting diode 100 of FIG. 7, but there is a difference in that the conformal coating 50 is positioned on the substrate 21. The conformal coating 50 may cover the second surface 21b of the substrate 21 with a uniform thickness and may also cover the side surface 21c. The conformal coating 50 may include a wavelength converting material such as a phosphor.

Furthermore, the sum of the thickness t1 of the substrate 21 and the thickness t2 of the conformal coating 50 may be 225 µm or more and 600 µm or less. For example, the thickness t2 of the conformal coating 50 may have a value in the range of 20 μm to 200 μm. In addition, the thickness t1 of the substrate 21 may be changed according to the thickness t2 of the conformal coating, and may have a value within a range of 150 μm to 400 μm, for example.

When the sum t1 + t2 of the thickness of the substrate 21 and the conformal coating 50 is 225 μm or more, the directivity angle of the light emitting diode 200 may be increased to 140 degrees or more.

9 to 12 are graphs showing directivity of light emitting diodes at various substrate thicknesses. In each graph, the solid line represents the directivity characteristic in the first axis (x-axis) direction, and the dotted line represents the directivity characteristic in the second axis (y-axis) direction orthogonal to the first axis.

A sapphire substrate was used as the substrate 21, and light emitting diodes as described in FIG. 7 were manufactured by varying the thickness of the sapphire substrate 21. The size of the light emitting diode was 1 mm x 1 mm, and the thicknesses of the sapphire substrate 21 were approximately 80 µm, 150 µm, 250 µm and 400 µm.

9 to 12, it can be seen that as the thickness of the substrate 21 is increased from 80 μm to 250 μm, the directional distribution is widened. However, when the thickness of the substrate 21 was increased from 250 µm to 400 µm, no significant difference appeared in the orientation distribution.

FIG. 13 is a graph illustrating the directivity angles of light emitting diodes according to the thickness of the substrate of FIGS. 9 to 12. 'Orientation angle' refers to the angle range in which a light beam of 1/2 or more of the maximum light beam appears. 'Orientation angle' corresponds to the angular length from the minimum angle to the maximum angle at which the normalized intensity becomes 0.5 in the directed distribution graph.

Referring to FIG. 13, as the thickness t1 of the substrate 21 is increased to 250 μm, the orientation angle increases to about 140 degrees, and the orientation angle is large when the thickness t1 of the substrate 21 is 250 μm or more. There was no change.

Therefore, when the thickness t1 of the substrate 21 is set to 250 μm, the orientation angle can be maintained at 140 degrees without applying another transparent film on the substrate 21, and the thickness t1 is increased beyond that. Even if it is made, a big change in orientation angle does not occur.

14 to 17 are graphs showing directivity of light emitting diodes 200 having conformal coatings at various substrate thicknesses t1. In each graph, the solid line represents the directivity characteristic in the first axis (x-axis) direction, and the dotted line represents the directivity characteristic in the second axis (y-axis) direction orthogonal to the first axis.

As described with reference to FIGS. 9 to 12, light emitting diodes are manufactured by varying the thickness t1 of the sapphire substrate 21, and the same thickness t2 of about 75 μm is formed on each substrate 21. The formal coating 50 was applied to fabricate the light emitting diodes 200 as shown in FIG. 8.

14 to 17, it can be seen that the directivity distribution is greatly changed as the thickness of the substrate 21 is increased from 80 μm to 150 μm. In addition, as the thickness of the substrate 21 increased from 150 μm to 400 μm, the light flux tended to decrease slightly around 0 degrees, but there was no significant difference in the directional distribution.

FIG. 18 is a graph illustrating directing angles of the light emitting diodes 200 having the conformal coating 50 according to the substrate thickness t1 of FIGS. 14 to 17.

Referring to FIG. 18, as the thickness t1 of the substrate 21 increases to 150 μm, the orientation angle increases to about 143 degrees, and when the thickness t1 of the substrate 21 is 150 μm or more, the orientation angle is large. There was no change. Therefore, when the sum of the thickness t1 of the substrate 21 and the thickness t2 of the conformal coating 50 is 225 µm or more, the orientation angle is saturated to a value of 140 degrees or more.

Accordingly, when the sum of the thicknesses of the substrate 21 and the conformal coating 50 is set to 225 μm or more, the light emitting diode 200 having a directivity angle of 140 degrees or more can be provided.

From the above experimental results, it is expected that the light emitting diode 200 having a directivity angle of 140 degrees or more may be provided even when the thickness of the substrate 21 is about 225 μm without the conformal coating 50.

19 is a schematic cross-sectional view illustrating a light emitting diode module 300a employing conventional light emitting diodes 10 and light emitting diode modules 300b and 300c employing light emitting diodes 100 according to the present invention. Here, as an example, the light emitting diode modules 300a, 300b, and 300c are used as backlight units for backlighting the liquid crystal display panel 400.

Referring to FIG. 19, the conventional light emitting diode 10 has a directivity angle θ ₁ of approximately 120 degrees, whereas the light emitting diode 100 of the present invention has a directivity angle θ ₂ of approximately 140 degrees or more.

The distance between the light emitting diode module and the liquid crystal display panel 400 may be expressed as d, the pitch of the light emitting diodes p, and the directivity angle of the light emitting diodes θ. On the other hand, when the light emitting diodes are arranged such that the directivity angles do not overlap each other, the pitch p represents the width of a region where one light emitting diode irradiates the liquid crystal display panel 400, and is represented by the following equation (1).

[Equation 1]

p = 2.dtan (θ / 2).

Therefore, the pitch p1 of the conventional light emitting diode module 300a and the pitch p2 of the light emitting diode module 300b according to the present invention are represented by the following equations (2) and (3), respectively.

[Equation 2]

p1 = 2 · d1 · tan ( θ 1/2).

[Equation 3]

p2 = 2 · d2 · tan ( θ 2/2).

Here, the orientation angle (θ ₂₎ of the LED 100 is to the following formula (4) is satisfied since larger than the directivity angle (θ ₁₎ of the conventional light-emitting diode (10) θ _2/2 is smaller than 90 degrees .

[Equation 4]

_{tan (θ 1/2) <} tan (θ 2/2).

Therefore, if d1 is equal to d2 in the above formulas (2) and (3), the following formula (5) holds.

[Equation 5]

p2> p1 (when d1 = d2).

That is, the light emitting diode modules 300a and 300b shown in FIGS. 19A and 19B may be irradiated with the same area of the liquid crystal display panel 400 at a same distance (d1 = d2) away from the liquid crystal display panel 400. In this case, the light emitting diode module 300b according to the present invention may arrange the light emitting diodes 100 at a wider distance than the conventional light emitting diode module 300a. Therefore, the number of light emitting diodes 100 used in the light emitting diode module 300b may be reduced.

Meanwhile, as shown in FIGS. 19A and 19C, the pitch p1 of the light emitting diodes 10 of the conventional light emitting diode module 300a and the pitch p of the light emitting diodes 100 of the present invention ( If p3) is the same, the following equation (6) holds.

[Equation 6]

d3 <d1 (when p1 = p3).

That is, when the number of light emitting diodes disposed in the light emitting diode modules 300a and 300c is the same, the light emitting diode module 300c of the present invention is closer to the liquid crystal display panel 400 than the light emitting diode module 300a. It can be arranged and, therefore, the backlight unit and further liquid crystal display can be made slimmer.

Herein, the light emitting diode modules 300a, 300b, and 300c are used as backlight units, but the light emitting diode modules 300a, 300b, and 300c may be used as lighting modules used in lighting devices. In this case, the illumination modules 300a, 300b, and 300c may irradiate the diffuser plate 400 of the illumination device. , Or closer to the diffuser plate.

Claims (28)

A transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface;
A first conductivity type semiconductor layer on the first surface of the transparent substrate;
A second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer;
A reflective electrode disposed on the second conductive semiconductor layer and ohmic contacting the second conductive semiconductor layer;
A current spreading layer covering the second conductive semiconductor layer and the reflective electrode, having an opening exposing the reflective electrode, ohmic contact with the first conductive semiconductor layer, and insulated from the second conductive semiconductor layer;
A first pad electrically connected to the current spreading layer and electrically connected to the first conductivity type semiconductor layer; And
A second pad electrically connected to the reflective electrode through the opening of the current spreading layer and electrically connected to the second conductive semiconductor layer;
A conformal coating layer covering the second surface of the transparent substrate,
The sum of the thicknesses of the transparent substrate and the conformal coating layer has a value within the range of 225 μm to 600 μm,
The thickness of the transparent substrate has a value in the range of 150 ㎛ to 400 ㎛,
Light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate,
Light emitted from the second surface is emitted to the outside of the conformal coating layer through the conformal coating layer,
A light emitting diode having a directivity angle of at least 140 degrees in at least one axial direction. delete delete delete The method according to claim 1,
The thickness of the conformal coating has a value in the range of 20㎛ 200㎛. The method according to claim 1,
The thickness of the transparent substrate is a light emitting diode having a value in the range of 225㎛ to 400㎛. delete The method according to any one of claims 1, 5 and 6,
Further comprising a plurality of mesas spaced apart from each other on the first conductivity type semiconductor layer,
Wherein each mesa includes the active layer and the second conductivity type semiconductor layer,
The reflective electrode is located on each mesa and ohmic contact to the second conductive semiconductor layer of each mesa,
The current spreading layer covers the plurality of mesas and the first conductive semiconductor layer, and has openings disposed in the upper region of each mesa and exposing reflective electrodes on the respective mesas, and are insulated from the plurality of mesas. Become,
And the second pad is electrically connected to the reflective electrode on each mesa through the openings. The method according to claim 8,
The plurality of mesas have an elongated shape extending parallel to each other in one direction. The method according to claim 8,
And the current spreading layer comprises a reflective metal. The method according to claim 8,
Each of the reflective electrodes includes a reflective metal layer and a barrier metal layer, the barrier metal layer covering the top and side surfaces of the reflective metal layer. The method according to claim 8,
An upper insulating layer covering at least a portion of the current spreading layer, the upper insulating layer having openings exposing the reflective electrodes,
And the second pad is connected to reflective electrodes exposed through openings of the upper insulating layer. The method according to claim 8,
A lower insulating layer disposed between the plurality of mesas and the current spreading layer to insulate the current spreading layer from the plurality of mesas,
And the lower insulating layer has openings positioned in the respective mesa upper regions to expose the reflective electrodes. The method according to claim 13,
The openings of the current spreading layer each have a wider width than the openings of the lower insulating layer so that all of the openings of the lower insulating layer are exposed. The method according to claim 14,
A top insulating layer covering at least a portion of the current spreading layer and having openings exposing the reflective electrodes,
And the upper insulating layer covers sidewalls of openings of the current spreading layer. The method according to claim 13,
The lower insulating layer is a reflective dielectric layer. The method according to claim 1,
Wherein the side surface is inclined such that the width of the first surface has a larger area than the width of the second surface. A transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface;
A first conductivity type semiconductor layer on the first surface of the transparent substrate;
A second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer;
A reflective electrode disposed on the second conductive semiconductor layer and ohmic contacting the second conductive semiconductor layer;
A current spreading layer covering the second conductive semiconductor layer and the reflective electrode, having an opening exposing the reflective electrode, ohmic contact with the first conductive semiconductor layer, and insulated from the second conductive semiconductor layer;
A first pad electrically connected to the current spreading layer and electrically connected to the first conductivity type semiconductor layer; And
A second pad electrically connected to the reflective electrode through the opening of the current spreading layer and electrically connected to the second conductivity type semiconductor layer,
Light generated in the active layer is emitted to the outside through the second surface of the transparent substrate,
The thickness of the transparent substrate is a light emitting diode having a value in the range of 225㎛ to 400㎛. A transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface;
A first conductivity type semiconductor layer on the first surface of the transparent substrate;
A second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer;
A reflective electrode disposed on the second conductive semiconductor layer and ohmic contacting the second conductive semiconductor layer;
A current spreading layer covering the second conductive semiconductor layer and the reflective electrode, having an opening exposing the reflective electrode, ohmic contact with the first conductive semiconductor layer, and insulated from the second conductive semiconductor layer;
A first pad electrically connected to the current spreading layer and electrically connected to the first conductivity type semiconductor layer;
A second pad electrically connected to the reflective electrode through the opening of the current spreading layer and electrically connected to the second conductive semiconductor layer; And
Conformal coating layer covering the transparent substrate,
Light generated in the active layer is emitted to the outside through the conformal coating layer,
The sum of the thicknesses of the transparent substrate and the conformal coating has a value in the range of 225 μm to 600 μm. Have, delete An illumination module comprising a plurality of light emitting diodes,
At least one light emitting diode,
A transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface;
A first conductivity type semiconductor layer on the first surface of the transparent substrate;
A second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer;
A reflective electrode disposed on the second conductive semiconductor layer and ohmic contacting the second conductive semiconductor layer;
A current spreading layer covering the second conductive semiconductor layer and the reflective electrode, having an opening exposing the reflective electrode, ohmic contact with the first conductive semiconductor layer, and insulated from the second conductive semiconductor layer;
A first pad electrically connected to the current spreading layer and electrically connected to the first conductivity type semiconductor layer;
A second pad electrically connected to the reflective electrode through the opening of the current spreading layer and electrically connected to the second conductive semiconductor layer; And
A conformal coating layer covering the second surface of the transparent substrate,
The sum of the thicknesses of the transparent substrate and the conformal coating layer has a value within the range of 225 μm to 600 μm,
The thickness of the transparent substrate has a value in the range of 150 ㎛ to 400 ㎛,
Light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate,
Light emitted from the second surface is emitted to the outside of the conformal coating layer through the conformal coating layer,
And the at least one light emitting diode has a directing angle of at least 140 degrees in at least one axial direction. The method according to claim 21,
The thickness of the transparent substrate is a lighting module having a value in the range of 225㎛ to 400㎛. delete A lighting device comprising the lighting module according to claim 21. In the backlight unit comprising a plurality of light emitting diodes,
At least one light emitting diode,
A transparent substrate having a first surface, a second surface, and a side surface connecting the first surface and the second surface;
A first conductivity type semiconductor layer on the first surface of the transparent substrate;
A second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
An active layer positioned between the first conductive semiconductor layer and the second conductive semiconductor layer;
A reflective electrode disposed on the second conductive semiconductor layer and ohmic contacting the second conductive semiconductor layer;
A current spreading layer covering the second conductive semiconductor layer and the reflective electrode, having an opening exposing the reflective electrode, ohmic contact with the first conductive semiconductor layer, and insulated from the second conductive semiconductor layer;
A first pad electrically connected to the current spreading layer and electrically connected to the first conductivity type semiconductor layer;
A second pad electrically connected to the reflective electrode through the opening of the current spreading layer and electrically connected to the second conductive semiconductor layer; And
A conformal coating layer covering the second surface of the transparent substrate,
The sum of the thicknesses of the transparent substrate and the conformal coating layer has a value within the range of 225 μm to 600 μm,
The thickness of the transparent substrate has a value in the range of 150 ㎛ to 400 ㎛,
Light generated in the active layer is emitted to the outside of the transparent substrate through the second surface of the transparent substrate,
Light emitted from the second surface is emitted to the outside of the conformal coating layer through the conformal coating layer,
And the at least one light emitting diode has a directivity angle of at least 140 degrees in at least one axial direction. The method according to claim 25,
The thickness of the transparent substrate is a backlight unit having a value in the range of 225㎛ to 400㎛. delete The method according to claim 25,
The thickness of the conformal coating has a value in the range of 20㎛ to 200㎛.

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