WO2016048079A1

WO2016048079A1 - Light emitting diode and method for fabricating the same

Info

Publication number: WO2016048079A1
Application number: PCT/KR2015/010137
Authority: WO
Inventors: Joon Hee Lee; Mi Hee Lee
Original assignee: Seoul Viosys Co., Ltd.
Priority date: 2014-09-26
Filing date: 2015-09-24
Publication date: 2016-03-31

Abstract

A light emitting diode and a method for fabricating the same. The light emitting diode includes a light emitting structure including a second conductive type semiconductor layer, a first conductive type semiconductor layer and an active layer, the light emitting structure having a second hole formed through the active layer and the second conductive type semiconductor layer to expose the first conductive type semiconductor layer; a reflective metal layer; a cover metal layer; a first insulation layer; an electrode layer disposed under the first insulation layer and covering the first insulation layer while filling a second hole; and an electrode pad disposed on the light emitting structure, wherein the light emitting structure has a first hole formed above the cover metal layer, and the electrode pad is formed on the light emitting structure above the cover metal layer.

Description

LIGHT EMITTING DIODE AND METHOD FOR FABRICATING THE SAME

This patent document relates to a light emitting diode and a method for fabricating the same, and more particularly, to a light emitting diode including an embedded electrode layer and a method for fabricating the same.

A light emitting diode is an inorganic semiconductor device that generates light through recombination of electrons and holes. Such a light emitting diode is used in various fields including displays, vehicle lamps, general lighting, and the like, and an application range of the light emitting diode has expanded.

As for the light emitting diode, a lateral type light emitting diode in which an n-type electrode and a p-type electrode are laterally disposed is broadly used in the art. Although the lateral type light emitting diode can be relatively easily fabricated, it has a problem of reduction in luminous area due to partial removal of an active layer to form electrodes on a lower semiconductor layer. Further, lateral arrangement of the electrodes causes current crowding, thereby deteriorating luminous efficacy of the light emitting diode.

Moreover, a sapphire substrate is most generally used as a growth substrate for lateral type light emitting diodes and provides a problem of inefficient heat discharge due to low thermal conductivity thereof. Such problems of the lateral type light emitting diode cause increase in junction temperature of the light emitting diode and deterioration in internal quantum efficiency thereof.

In order to overcome such problems of the lateral type light emitting diode, a vertical type light emitting diode and a flip-chip type light emitting diode have been developed.

A typical light emitting diode includes a conductive substrate, a first electrode layer, an insulation layer, a second electrode layer, a second semiconductor layer, an active layer and a first semiconductor layer, which are sequentially stacked in this order. In this structure, in order to electrically connect the second semiconductor layer, an electrode pad is formed on an exposed region laterally extending from the second electrode layer.

However, in formation of such a structure of the light emitting diode, the electrode pad can be damaged by oxidation and the like, thereby causing increase in contact resistance and forward voltage. As a result, the light emitting diode can suffer from reduction in output, causing deterioration in reliability and lifespan of the light emitting diode.

Exemplary embodiments provide a light emitting diode which can prevent reduction of output while improving yield, and a method for fabricating the same.

In accordance with one exemplary embodiment, a light emitting diode includes: a light emitting structure including a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer, and an active layer interposed between the first and second conductive type semiconductor layers, the light emitting structure having a second hole formed through the active layer and the second conductive type semiconductor layer to expose the first conductive type semiconductor layer; a reflective metal layer disposed under the light emitting structure and contacting a portion of the light emitting structure; a cover metal layer disposed under the reflective metal layer and contacting at least a portion of the reflective metal layer; a first insulation layer disposed under the cover metal layer and covering the reflective metal layer and the cover metal layer; an electrode layer disposed under the first insulation layer and covering the first insulation layer while filling the second hole; and an electrode pad disposed on the light emitting structure, wherein the light emitting structure has a first hole formed above the cover metal layer, and the electrode pad may be formed on the light emitting structure above the cover metal layer.

The light emitting structure may be divided from a pad installation section by the first hole, and the cover metal layer may be disposed under an overall region of the light emitting structure and some region of the pad installation section. Further, the cover metal layer may be formed along peripheries of the light emitting structure and the pad installation section, and may be formed to cover a periphery of the reflective metal layer.

The electrode layer may fill the second hole to form ohmic contact with the first conductive type semiconductor layer, and the reflective metal layer may be disposed on a region of the first insulation layer in which the first hole is not formed.

In accordance with another exemplary embodiment, a method for fabricating a light emitting diode includes: forming a mesa structure on a light emitting structure including a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer and an active layer interposed between the first and second conductive type semiconductor layers; forming a reflective metal layer in some region of the light emitting structure having the mesa structure formed thereon; forming a cover metal layer to cover a portion of the reflective metal layer; forming a first insulation layer to cover the reflective metal layer and the cover metal layer; forming an electrode layer to cover the first insulation layer while filling a second hole formed on the first insulation layer and the light emitting structure such that the first conductive type semiconductor layer of the light emitting structure is exposed; removing a portion of the light emitting structure to form a first hole on a surface of the light emitting structure on which the mesa structure is not formed; and forming an electrode pad on an upper surface of a pad installation section divided from the light emitting structure by the first hole.

The electrode pad may be formed above the cover metal layer and the cover metal layer may be formed along a periphery of the light emitting structure. In addition, the cover metal layer may be formed to cover the periphery of the reflective metal layer.

Further, the electrode layer may fill the second hole to form ohmic contact with the first conductive type semiconductor layer, and the reflective metal layer may be formed on a region of the first insulation layer in which the second hole is not formed.

In accordance with a further exemplary embodiment, a light emitting diode includes: a light emitting structure including a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer and an active layer interposed between the first and second conductive type semiconductor layers, the light emitting structure having a first hole and a second hole formed through the active layer and the second conductive type semiconductor layer so as to expose the first conductive type semiconductor layer; a metal layer disposed under the light emitting structure and covering a portion of the light emitting structure; a first insulation layer disposed under the metal layer and covering the metal layer; an electrode layer disposed under the first insulation layer and covering the first insulation layer while filling the first and second holes; and an electrode pad electrically connected to the metal layer, wherein the electrode layer filling the second hole is a line electrode, and the line electrode is formed along a periphery of the light emitting structure to have directionality of one direction in a plan view of the light emitting structure.

The electrode layer filling the first hole may be a first electrode and the line electrode may have a smaller width than the first electrode. Further, the metal layer may be disposed inside the line electrode in the plan view of the light emitting structure.

The line electrode may be formed under the light emitting structure in a region in which the electrode pad is not formed.

According to exemplary embodiments, a light emitting structure of the light emitting diode has an enlarged luminous area through removal of a cover metal layer, thereby improving luminous efficacy of the light emitting diode. Further, as a contact area between the reflective metal layer and the cover metal layer is reduced, metal stress caused by contact is reduced, thereby improving yield of the light emitting diode.

Further, the light emitting diode has a line electrode formed along a periphery thereof and thus can prevent luminous efficacy from being deteriorated at the periphery of the light emitting diode due to current crowding at a central region thereof, thereby enabling uniform light emission throughout the light emitting diode.

Figure 1 is a plan view of a light emitting diode according to one exemplary embodiment.

Figure 2 is a sectional view taken along line AA' of Figure 1.

Figure 3 shows sectional views illustrating a method for fabricating the light emitting diode according to the exemplary embodiment.

Figure 4 is a plan view of a light emitting diode according to another exemplary embodiment.

Figure 5a is a plan view of a light emitting diode according to a further exemplary embodiment.

Figure 5b is a plan view of the light emitting diode according to the further exemplary embodiment, on which a line electrode is disposed.

Figure 6 is a sectional view taken along line BB' of Figure 5a.

Hereinafter, exemplary embodiments of the disclosed technology will be described in more detail with reference to the accompanying drawings.

Figure 1 is a plan view of a light emitting diode according to one exemplary embodiment and Figure 2 is a sectional view taken along line AA' of Figure 1.

Referring to Figures 1 and 2, a light emitting diode 100 according to one exemplary embodiment includes a light emitting structure 110,

metal layers

120, 130, a first insulation layer 140, an electrode layer 150, a bonding layer 160, a substrate 170, electrode pads 180, and a protective layer 190.

The light emitting structure 110 includes a first conductive type semiconductor layer 111, an active layer 113, and a second conductive type semiconductor layer 115. The first conductive type semiconductor layer 111 may be disposed on the second conductive type semiconductor layer 115, and the active layer 113 may be interposed between the first conductive type semiconductor layer 111 and the second conductive type semiconductor layer 115. In this exemplary embodiment, the first conductive type semiconductor layer 111 may further include roughness R formed on an upper surface thereof and a plurality of lower mesas may be formed under the roughness R.

Each of the first conductive type semiconductor layer 111 and the second conductive type semiconductor layer 115 may include a III-V-based compound semiconductor, for example, a nitride-based semiconductor such as (Al, Ga, In)N. The first conductive type semiconductor layer 111 may include an n-type semiconductor layer doped with n-type dopants such as Si, and the second conductive type semiconductor layer 115 may include a p-type semiconductor layer doped with p-type dopants such as Mg. Obviously, the dopants used in the first conductive type semiconductor layer 111 and the second conductive type semiconductor layer 115 may also be interchanged.

In addition, each of the first conductive type semiconductor layer 111 and the second conductive type semiconductor layer 115 may be composed of a single layer or multiple layers. For example, the first conductive type semiconductor layer 111 and/or the second conductive type semiconductor layer 115 may include a clad layer and a contact layer, and may also include a superlattice layer.

The active layer 113 may include a multi-quantum well (MQW) structure, and elements constituting the multi-quantum well structure and the composition thereof may be adjusted to allow the multi-quantum well structure to emit light having a desired peak wavelength. For example, a well layer of the active layer 113 may be a ternary semiconductor layer such as InGaN or a quaternary semiconductor layer such as AlInGaN, where a composition ratio of components may be adjusted to emit light having a desired peak wavelength.

As shown in Figures 1 and 2, first holes H1 may be formed through the light emitting structure 110 by partially removing the light emitting structure 110. In this exemplary embodiment, two first holes H1 are formed such that two pad installation sections 111a disposed at corners of the light emitting diode are divided from the light emitting structure 110 by the two grooves H1.

Referring to Figure 1, although each of the pad installation sections 111a is formed in a rectangular shape by the first hole H1 in this exemplary embodiment, it should be understood that the shape of the pad installation sections 111a can be changed, as needed.

The pad installation sections 111a are disposed at the corners of the light emitting diode 100, respectively, as shown in Figure 1, and may be flush with the light emitting structure 110, as shown in Figure 1. The pad installation sections 111a are formed in the course of forming the light emitting structure 110 and thus may be composed of a semiconductor layer having the same composition as that of the first conductive type semiconductor layer 111 of the light emitting structure 110. In addition, the pad installation sections 111a are flush with the light emitting structure 110. Accordingly, the electrode pads 180 disposed on the pad installation sections 111a protrude above the light emitting structure 110, thereby reducing defect rate upon wire bonding.

The roughness R may be formed on the upper surface of the first conductive type semiconductor layer 111 and may include irregular bumps and depressions. The structure wherein the roughness R is formed on the upper surface of the light emitting structure 110 can improve light extraction efficiency upon emission of light through the upper surface of the light emitting structure 110.

The roughness R may be formed by wet etching in a solution containing at least one of KOH and NaOH, or by PEC etching. Alternatively, the roughness R may be naturally formed in the course of separating a growth substrate from the first conductive type semiconductor layer 111. For example, the roughness R may be formed on a separated surface of the first conductive type semiconductor layer 111 and originates from cavities formed by a sacrificial layer, which is additionally formed for separation of the growth substrate, when the growth substrate is separated from the first conductive type semiconductor layer 111 by chemical lift-off or stress lift-off. In this way, the roughness R may be formed by various methods.

Mesas may be formed on a lower side of the light emitting structure 110. The mesas may include the second conductive type semiconductor layer 115 and the active layer 113, and may further include a portion of the first conductive type semiconductor layer 111. In the exemplary embodiment, the mesas may be formed in a partial protrusion shape, as shown in Figures 1 and 2. However, it should be understood that the present disclosure is not limited thereto and other implementations are possible. The mesas may have various shapes and sizes.

Further, one or more second holes H2 may be formed in the mesa. Accordingly, the electrode layer 150 fills the second holes H2 such that the electrode layer 150 can be electrically connected to the first conductive type semiconductor layer 111. Although plural second holes H2 are regularly arranged at certain intervals in Figure 1, it should be understood that various modifications of locations and arrangement of the second holes are possible.

The metal layers 120, 130 are formed under the light emitting structure 110 and include a reflective metal layer 120 and a cover metal layer 130. The metal layers 120, 130 may be electrically connected to the second conductive type semiconductor layer 115. In this exemplary embodiment, the metal layers 120, 130 directly contact the second conductive type semiconductor layer 115, as shown in Figure 2.

The reflective metal layer 120 serves to reflect light emitted from the light emitting structure 110, and also acts as an electrode that is electrically connected to the second conductive type semiconductor layer 115 in this exemplary embodiment. Accordingly, the reflective metal layer 120 may include a metal having high reflectivity and capable of forming ohmic contact with the second conductive type semiconductor layer 115. Accordingly, the reflective metal layer 120 may include at least one of Ni, Pt, Pd, Rh, W, Ti, Al, Ag and Au, and may be composed of a single layer or multiple layers, as needed.

Even in a structure wherein the reflective metal layer 120 is composed of a single layer, the reflective metal layer 120 may be formed only in some regions instead of being formed over an overall region thereof, as shown in Figure 2. That is, in a region of the mesa including an inclined surface, a second insulation layer 140a (for example, SiO₂) is formed without forming the reflective metal layer 120, such that the reflective metal layer 120 can be formed only in a flat region. With this structure, the reflective metal layer 120 is formed to have a smaller area than the second conductive type semiconductor layer 115, and the electrode layer 150 filling the second holes H2 is prevented from directly contacting the reflective metal layer 120. Here, the second insulation layer 140a may include, for example, SiO₂ or SiN.

Here, the reflective metal layer 120 is disposed on most region of the second conductive type semiconductor layer 115 excluding a region in which the second hole H2 is formed, so that most light emitted from the active layer 113 and directed in the downward direction can reach the reflective metal layer 120 and be reflected in the upward direction by the reflective metal layer 120. As a result, the light emitting diode 100 can have improved light extraction efficiency.

The cover metal layer 130 is formed to cover some region of the reflective metal layer 120. As shown in Figure 2, the cover metal layer 130 covers some region of the reflective metal layer 120 including a region in which the electrode pads 180 are formed. Conventionally, since the cover metal layer 130 is formed to cover the entirety of the reflective metal layer 120, metal stress between the reflective metal layer 120 and the cover metal layer 130 occurs over the reflective metal layer 120. On the other hand, in the exemplary embodiment, the cover metal layer 130 is formed to cover some region of reflective metal layer 120 to minimize metal stress between the cover metal layer 130 and the reflective metal layer 120, thereby minimizing peeling caused thereby while improving reflection efficiency.

The cover metal layer 130 may be electrically connected to the reflective metal layer 120 to be electrically connected to the second conductive type semiconductor layer 115. With this structure, the cover metal layer 130 can also act as an electrode together with the reflective metal layer 120. The cover metal layer 130 may include at least one of Au, Ni, Ti, Cr, Pt, W and TiW, and may be composed of a single layer or multiple layers.

The first insulation layer 140 is disposed under the light emitting structure 110. Particularly, the first insulation layer 140 is formed to surround the second holes H2 formed in the lower mesas. The first insulation layer 140 may include an insulation material. Further, the first insulation layer 140 may include multiple layers and may include a distributed Bragg reflector in which materials having different indexes of refraction are stacked one above another.

As such, the first insulation layer 140 includes the distributed Bragg reflector and thus has a thick thickness, thereby minimizing step formation.

The electrode layer 150 is disposed under the first insulation layer 140. Further, a first electrode 150a may extend from a portion of the electrode layer 150 and form ohmic contact with the first conductive type semiconductor layer 111 through the second holes H2. Accordingly, electric current supplied through the electrode layer 150 can be supplied to the first conductive type semiconductor layer 111 through the first electrode 150a.

A plurality of first electrodes 150a may extend from the electrode layer 150. Further, the plurality of first electrodes 150a may be arranged in a pattern over the electrode layer 150, as shown in Figure 1. However, it should be understood that the present disclosure is not limited thereto and arrangement of the first electrodes may be changed in various ways, as needed. With the structure wherein the plurality of first electrodes 150a is arranged throughout the light emitting diode 100, the light emitting diode 100 has further improved current spreading efficiency.

The bonding layer 160 is disposed under the electrode layer 150 and bonds the substrate 170 to the electrode layer 150. That is, the substrate 170 is bonded to the light emitting structure 110 through the bonding layer 160. Further, the bonding layer 160 may be electrically connected to the first electrodes 150a on the electrode layer 150 and may serve to electrically connect the substrate 170 to the electrode layer 150. To this end, the bonding layer 160 may include Au and Sn, and may also include NiSn or AuIn.

The substrate 170 is disposed under the bonding layer 160 and allows electric current to be supplied to the electrode layer 150 and the first conductive type semiconductor layer 111 therethrough when the electric current is supplied to the substrate.

The substrate 170 may also act as a support substrate, and may be a conductive substrate, a circuit board, or a patterned insulation substrate. In one exemplary embodiment, the substrate may include a metal and may have a structure in which a molybdenum (Mo) layer and a copper (Cu) layer are stacked. Further, the substrate may include Ti, Cr, Ni, Al, Cu, Ag, Au, Pt, and the like.

The light emitting diode according to the exemplary embodiment includes a plurality of electrode pads 180 each disposed on the pad installation section 111a. Each of the electrode pads 180 may be disposed on the pad installation section 111a having roughness R formed thereon and electrically connected to the first conductive type semiconductor layer 111.

Further, the electrode pad 180 may include a plurality of electrode pad layers including an upper electrode pad layer and a lower electrode pad layer. The lower electrode pad layer is formed on the first conductive type semiconductor having the roughness R formed thereon, and the upper electrode pad layer may be formed on the lower electrode pad layer.

With such a vertical type structure, the light emitting diode 100 according to the exemplary embodiment may further include a protective layer 190 as shown in Figure 2. The protective layer 190 may cover the upper surface of the first conductive type semiconductor layer 111. Further, the protective layer 190 may cover a side surface of the first conductive type semiconductor layer 111 to protect the light emitting structure 110 from an external environment. Further, the protective layer 190 may cover the roughness R on the upper surface of the first conductive type semiconductor layer 111 to have a gentler inclination than the roughness R, thereby improving light extraction efficiency. Here, the protective layer 190 may include an insulation material, for example, SiO₂.

Referring to Figure 3a, a light emitting structure 110 including a first conductive type semiconductor layer 111, an active layer 113 and a second conductive type semiconductor layer 115 is formed.

The light emitting structure 110 is grown on a growth substrate 10. As for the growth substrate 10, any substrate may be used so as to allow growth of the light emitting structure 110 thereon. For example, the growth substrate may be a sapphire substrate, a silicon carbide substrate, a silicon substrate, a gallium nitride substrate, an aluminum nitride substrate, and the like.

The first conductive type semiconductor layer 111, the active layer 113, and the second conductive type semiconductor layer 115 may be grown on the growth substrate 10 by a process, such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE).

Referring to Figure 3b, with the light emitting structure 110 formed on the growth substrate, a lower mesa structure is formed by partially etching an upper surface of the light emitting structure 110. In this process, the first conductive type semiconductor layer 111 may be partially exposed by etching.

Referring to Figure 3c, a reflective metal layer 120 is deposited on the upper surface of the light emitting structure 110 on which the lower mesa structure is formed. The reflective metal layer 120 is formed on a flat region of the light emitting structure 110 instead of being formed over the entirety of the upper surface thereof. Since the reflective metal layer 120 is formed on the second conductive type semiconductor layer 115 by deposition and the like to be disposed only on a predetermined portion by a lift-off process, the reflective metal layer 120 is formed on the overall flat region excluding an inclined surface. As a result, although the reflective metal layer 120 can be formed in a smaller size than an exposed region of the second conductive type semiconductor layer 115, the reflective metal layer 120 can be formed to cover most of the second conductive type semiconductor layer 115. Further, a second insulation layer 140a is deposited on a region of the first conductive type semiconductor layer 111 in which the reflective metal layer 120 is not formed.

Referring to Figure 3d, a cover metal layer 130 is deposited on the upper surface of the light emitting structure on which the reflective metal layer 120 is formed. The cover metal layer 130 is formed to cover a portion of the reflective metal layer 120.

Referring to Figure 3e, a first insulation layer 140 is formed to cover an upper surface of the cover metal layer 130 and the entirety of the reflective metal layer 120 excluding a region of the reflective metal layer 120 on which the cover metal layer 130 is not formed. In addition, second holes H2 are formed at locations at which the light emitting structure 110 is removed by etching. As a result, the first conductive type semiconductor layer 111 can be exposed on bottoms of the second holes H2. In this way, a plurality of second holes H2 may be formed.

Referring to Figure 3f, an electrode layer 150 is formed on the first insulation layer 140. The electrode layer 150 fills the second holes H2 formed in the first insulation layer 140 to contact some exposed regions of the first conductive type semiconductor layer 111 on the bottoms of the second holes H2.

Referring to Figure 3g, a bonding layer 160 may be formed on the electrode layer 150, and a substrate 170 may be formed on the bonding layer 160. The growth substrate 10 may be removed upon formation of the substrate 170. The bonding layer 160 may be formed to have ohmic contact with the electrode layer 150. The bonding layer 160 bonds the electrode layer 150 to the substrate 170 by adjusting pressure and temperature with the bonding layer 160 interposed between the electrode layer 150 and the substrate 170.

Referring to Figures 3h to 3j, the light emitting diode is turned upside down from the state shown in Figures 3a to 3g. Thus, for convenience of description, upper and lower sides of the light emitting diode will be described with reference to the structure shown in Figures 3h to 3j, and it should be understood that the present disclosure is not limited thereto.

Referring to Figure 3h, roughness R may be formed on the surface of the first conductive type semiconductor layer 111 in the course of removing the growth substrate 10. Further, upon removal of the growth substrate 10, a side surface of the light emitting structure 110 may also be partially removed.

Referring to Figure 3i, with the growth substrate 10 removed from the light emitting structure 10, a first hole H1 is formed on a rear side of the light emitting structure 110, to which the substrate 170 is bonded, to pass through the light emitting structure 110. The first hole H1 is provided to divide the light emitting structure 110 from a pad installation section 111a and may be formed by removing the first conductive type semiconductor layer 111, the active layer 113 and the second conductive type semiconductor layer 115 by dry etching or the like. Here, only the first conductive type semiconductor layer 111 remains in the pad installation section 111a divided from the light emitting structure 110, as shown in Figure 3i.

After forming the first hole H1, a protective layer 190 may be additionally formed on the first conductive type semiconductor layer 111. The protective layer 190 may be formed over the overall region including the upper and side surfaces of the first conductive type semiconductor layer 111 and the first hole H1. With this structure, the protective layer 190 can protect the light emitting structure 110 from an external environment and the roughness formed on the upper surface of the first conductive type semiconductor layer 111 can have a gentle slope, thereby improving light extraction efficiency.

Referring to Figure 3j, with the light emitting structure 110 divided from the pad installation section 111a by the first hole H1, an electrode pad 180 is formed on an upper surface of the pad installation section 111a. The electrode pad 180 may be formed by deposition or any lift-off technology. Here, the electrode pad 180 may be disposed to contact the pad installation section 111a in a state that a portion of the protective layer 190 is removed.

A light emitting diode 100 according to another exemplary embodiment includes a light emitting structure 110,

metal layers

120, 130, a first insulation layer 140, an electrode layer 150, a bonding layer 160, a substrate 170, and electrode pads 180, and may further include a protective layer 190. Descriptions of the same features of the light emitting diode 100 according to this exemplary embodiment as those of the above exemplary embodiment are omitted and Figures 1 to 3 are also referred to in description of the light emitting diode 100 according to this exemplary embodiment.

Referring to Figure 4, in this exemplary embodiment, a cover metal layer 130 is formed along the periphery of the light emitting structure 110 while surrounding the electrode pads 180. Since the cover metal layer 130 is formed to completely cover the periphery of the reflective metal layer 120, the reflective metal layer 120 is not exposed. Accordingly, it is possible to prevent damage to the reflective metal layer 120 due to diffusion of foreign substances to the reflective metal layer 120, which can occur when the reflective metal layer 120 is exposed.

Figure 5a is a plan view of a light emitting diode according to a further exemplary embodiment and Figure 5b is a plan view of the light emitting diode according to the further exemplary embodiment, on which a line electrode is disposed. Figure 6 is a sectional view taken along line BB' of Figure 5a.

A light emitting diode 100 according to a further exemplary embodiment includes a light emitting structure 110,

metal layers

120, 130, a first insulation layer 140, a second insulation layer 140a, an electrode layer 150, a bonding layer 160, a substrate 170, electrode pads 180, and a protective layer 190. Descriptions of the same features of the light emitting diode 100 according to this exemplary embodiment as those of the above exemplary embodiment are omitted and Figures 1 to 3 are also referred to in description of the light emitting diode 100 according to this exemplary embodiment.

Referring to Figures 5a and 5b, the light emitting diode 100 according to this exemplary embodiment includes a plurality of holes H2, which may be regularly or irregularly arranged. Further, the light emitting diode 100 is provided with two electrode pads 180 respectively disposed at corners thereof. The reflective metal layer 120 and the cover metal layer 130 are formed to cover an overall region of the light emitting diode 100 excluding some region thereof.

In this exemplary embodiment, a line electrode 150b may be formed along the periphery of the light emitting diode 100. The line electrode 150b is formed to surround the entire periphery of the light emitting diode 100 excluding some region in which the electrode pads 180 are formed. Namely, in the plan view of Figure 5b, with two electrode pads 180 disposed at upper corners of the light emitting diode 100, the line electrode 150b may be formed along a periphery section of the light emitting diode 100 between the two electrode pads 180 and along other periphery sections of the light emitting diode 100.

Further, as shown in Figure 5a, the cover metal layer 130 may be formed on the overall region of the light emitting diode 100, excluding some region in which the electrode pads 180 are formed, to be placed inside the reflective metal layer 120. That is, since the reflective metal layer 120 is formed to have a larger area than the cover metal layer 130 on the overall region of the light emitting diode 100, the reflective metal layer 120 improves reflection efficiency of the light emitting diode 100, thereby improving luminous efficacy of the light emitting diode 100. In this exemplary embodiment, the cover metal layer 130 may extend to a lower side of the electrode pad in order to provide electrical connection between the electrode pad 180 and the second conductive type semiconductor layer 115.

Further, the line electrode 150b may be formed on a further outer region of the light emitting diode 100 than the reflective metal layer 120 and the cover metal layer 130. With the structure wherein the first insulation layer 140 is formed outside the line electrode 150b, it is possible to protect the side surface of the light emitting diode 100.

This structure of the light emitting diode 100 will be described in more detail with reference to Figure 6. Referring to Figure 6, the bonding layer 160 is formed on the substrate 170 and the electrode layer 150 is bonded to the substrate 170 via the bonding layer 160. The first insulation layer 140 is formed on the electrode layer 150 and the metal layers 120, 130 including the cover metal layer 130 and the reflective metal layer 120 are sequentially stacked on the first insulation layer 140. In addition, the second insulation layer 140a is formed on a side surface of the reflective metal layer 120. The second insulation layer 140a may be formed to a larger thickness than the total thickness of the reflective metal layer 120 and the cover metal layer 130, as will be described below.

The light emitting structure 110 is disposed on the second insulation layer 140a and the reflective metal layer 120. The light emitting structure 110 includes a plurality of mesas, and second holes H2 and a third hole H3 are formed between the plural mesas. The second holes H2 and the third hole H3 are formed through the first insulation layer 140 to expose the first conductive type semiconductor layer 111 therethrough. Further, the electrode layer 150 fills the second holes H2 and the third hole H3 to allow electrical connection between the electrode layer 150 and the first conductive type semiconductor layer 111. In this structure, side surfaces of the second holes H2 and the third hole H3 are covered by the first insulation layer 140 such that the electrode layer 150 filling the second holes H2 and the third hole H3 is electrically insulated from other layers.

As shown in Figure 1, the second holes H2 have a circular shape and the third hole H3 has a line shape extending in one direction in plan view. Accordingly, the electrode layer 150 filling the second holes H2 has a different structure than the electrode layer 150 filling the third hole H3. Here, the electrode layer 150 filling the second holes H2 are referred to as the first electrodes 150a and the electrode layer 150 filling the third hole H is referred to as the line electrode 150b.

As shown in Figure 1, the plurality of first electrodes 150a may be distributed over the overall surface of the light emitting diode 100 to be regularly or irregularly arranged.

In this exemplary embodiment, the line electrode 150b may be formed in a line shape having directionality along the periphery of the light emitting diode 100 excluding the corners of the light emitting diode 100 at which the electrode pads 180 are disposed. Of course, the line electrode 150b may have a curved shape instead of the line shape extending in one direction, and may be formed in regions where the electrode pads 180 are placed, as needed.

As described above, with the structure wherein the line electrode 150b is formed along the periphery of the light emitting diode 100, the light emitting diode can prevent deterioration in luminous efficacy at the periphery of the light emitting diode 100 due to current crowding at the center of the light emitting diode 100 in plan view. That is, the line electrode 150b formed along the periphery of the light emitting diode 100 can improve luminous efficacy at the periphery of the light emitting diode 100. As a result, the light emitting diode 100 enables uniform light emission, thereby providing improved luminous efficacy.

Further, in this exemplary embodiment, the line electrode 150b may be continuously formed at corners of the light emitting diode 100, at which the electrode pads 180 are not formed, in a shape corresponding to the corners of the light emitting diode 100, thereby improving luminous efficacy at a distal end of the light emitting diode 100.

In addition, the metal layers 120, 130 are not formed outside the line electrode 150b. In Figure 2, the outside of the line electrode 150b is a left side of the line electrode 150b and only the first insulation layer 140 is formed outside the line electrode 150b.

Referring to Figure 6, a width d1 of the first electrodes 150a filling the second hole H2 is different from a width d2 of the line electrode 150b filling the third hole H3. Specifically, the width d2 of the line electrode 150b is smaller than the width d1 of the first electrodes 150a. The line electrode 150b is formed along the periphery of the light emitting diode 100 and is disposed separate from arrangement of the first electrodes 150a. Thus, with the structure wherein the width d2 of the line electrode 150b is smaller than the width of the first electrodes 150a, current spreading in the line electrode 150b can be carried out more gently than current spreading in the first electrodes 150a.

Further, a contact width d3 between the first electrodes 150a and the first conductive type semiconductor layer 111 is different from a contact width d4 between the line electrode 150b and the first conductive type semiconductor layer 111. Specifically, the contact width d4 between the line electrode 150b and the first conductive type semiconductor layer 111 is smaller than the contact width d3 between the first electrodes 150a and the first conductive type semiconductor layer.

As in the exemplary embodiments, the first insulation layer 140 is formed on the overall region of the electrode layer 150 excluding some regions thereof in which the second holes H2 and the third hole H3 are formed, and the second insulation layer 140a is formed at opposite sides of the reflective metal layer 120. In this exemplary embodiment, a thickness d6 of the second insulation layer 140a is larger than a thickness d5 of the reflective metal layer 120 and is larger than a total thickness d5+d8 of a thickness d5 of the reflective metal layer 120 and a thickness d8 of the cover metal layer 130 covering the reflective metal layer 120. For example, the reflective metal layer 120 has a thickness d5 of about 2,200A and the cover metal layer 130 has a thickness d8 of about 7,000A. In addition the second insulation layer 140a formed at the opposite sides of the reflective metal layer 120 has a thickness d6 of about 16,000A.

In this exemplary embodiment, the electrode pads 180 are disposed at the corners of the light emitting diode 100, as shown in Figure 1. Further, as shown in Figure 2, the electrode pads 180 are formed after removal of the light emitting structure 110 by etching portions of the light emitting structure 110 on which the electrode pad 180 will be disposed. In a vertical structure of the light emitting structure at which the electrode pads 180 are disposed, the first insulation layer 140 is formed on the electrode layer 150 and the cover metal layer 130 is formed on the first insulation layer 140. Further, the second insulation layer 140a is formed on the cover metal layer 130.

The cover metal layer 130 extends from the lower side of the light emitting structure 110 and has a uniform thickness d8. In addition, the second insulation layer 140a formed on the cover metal layer 130 extends from the second insulation layer 140a formed under the light emitting structure 110 and has a smaller thickness d7 than the thickness d6 thereof under the light emitting structure 110. In this exemplary embodiment, the second insulation layer 140a formed under the light emitting structure 110 has a thickness d6 of about 16,000A and the second insulation layer 140a formed under the electrode pad 180 has a thickness d7 of about 8,000A.

The structure wherein the thickness d6 of the second insulation layer 140a disposed under the light emitting structure 110 is larger than the thickness d7 of the second insulation layer disposed under the electrode pad 180 can secure sufficient electrical insulation between the second conductive semiconductor layer and the electrode layer 150. Recently, since high electric current and high voltage are applied to the light emitting diode 100, electrical insulation between the light emitting structure 110 and the electrode layer 150 is of great concern.

Further, since the light emitting structure 110 is not formed in some region in which the electrode pads 180 are formed, it is not necessary to have a high thickness of the second insulation layer 140a, unlike the second insulation layer under the light emitting structure 110. Although increase in thickness of the second insulation layer 140a can provide improvement in insulation function, there can be an adverse effect of deterioration in luminous efficacy of the light emitting diode 100 due to a relative decrease in thickness of the light emitting structure 110 in a luminous region.

Further, a reflection area is enlarged by the cover metal layer 130 extending from the lower side of the light emitting structure 110 to a location at which the electrode pad 180 is formed, thereby improving luminous efficacy of the light emitting diode 100.

Further, since the electrode pad 180 is formed in a region from which the light emitting structure 110 is removed, the second insulation layer 140a is partially removed to allow the electrode pad 180 to be formed while contacting the cover metal layer 130, as shown in Figure 2.

Further, the protective layer 190 is formed to cover the entirety of the light emitting structure 110 and may be formed on the overall region of the light emitting diode 100 excluding the electrode pad 180.

Although some exemplary embodiments are disclosed in conjunction with the drawings, it should be understood that these embodiments and the accompanying drawings are provided for illustration only and are not to be construed as limiting the disclosed technology. The scope of the disclosed technology should be interpreted according to the following appended claims as covering all modifications or variations derived from the appended claims and equivalents thereof.

* List of Reference Numerals

100: Light emitting diode

110: Light emitting structure

111: First conductive type semiconductor layer

111a: Pad installation section

113: Active layer

115: Second conductive type semiconductor layer

120: Reflective metal layer

130: Cover metal layer 140: First insulation layer

140a: Second insulation layer 150: Electrode layer

150a: First electrode 150b: Line electrode

160: Bonding layer 170: Substrate

180: Electrode pad 190: Protective layer

H1: First hole H2: Second hole

H3: Third hole R: Roughness

Claims

A light emitting diode comprising:

a light emitting structure comprising a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer, and an active layer interposed between the first and second conductive type semiconductor layers, the light emitting structure having a second hole formed through the active layer and the second conductive type semiconductor layer to expose the first conductive type semiconductor layer;

a reflective metal layer disposed under the light emitting structure and contacting a portion of the light emitting structure;

a cover metal layer disposed under the reflective metal layer and contacting at least a portion of the reflective metal layer;

a first insulation layer disposed under the cover metal layer and covering the reflective metal layer and the cover metal layer;

an electrode layer disposed under the first insulation layer and covering the first insulation layer while filling the second hole; and

an electrode pad disposed on the light emitting structure,

wherein the light emitting structure has a first hole formed above the cover metal layer, and the electrode pad is formed on the light emitting structure above the cover metal layer.
The light emitting diode according to claim 1, wherein the light emitting structure is divided from a pad installation section by the first hole, and the cover metal layer is disposed under an overall region of the light emitting structure and some region of the pad installation section.
The light emitting diode according to claim 2, wherein the cover metal layer is formed along peripheries of the light emitting structure and the pad installation section.
The light emitting diode according to claim 3, wherein the cover metal layer is formed to cover a periphery of the reflective metal layer.
The light emitting diode according to claim 1, wherein the electrode layer fills the second hole to form ohmic contact with the first conductive type semiconductor layer.
The light emitting diode according to claim 1, wherein the reflective metal layer is disposed on a region of the first insulation layer in which the first hole is not formed.
A method for fabricating a light emitting diode, comprising:

forming a mesa structure on a light emitting structure comprising a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer and an active layer interposed between the first and second conductive type semiconductor layers;

forming a reflective metal layer in some region of the light emitting structure having the mesa structure formed thereon;

forming a cover metal layer to cover a portion of the reflective metal layer;

forming a first insulation layer to cover the reflective metal layer and the cover metal layer;

forming an electrode layer to cover the first insulation layer while filling a second hole formed on the first insulation layer and the light emitting structure such that the first conductive type semiconductor layer of the light emitting structure is exposed;

removing a portion of the light emitting structure to form a first hole on a surface of the light emitting structure on which the mesa structure is not formed; and

forming an electrode pad on an upper surface of a pad installation section divided from the light emitting structure by the first hole.
The method for fabricating a light emitting diode according to claim 7, wherein the electrode pad is formed above the cover metal layer.
The method for fabricating a light emitting diode according to claim 7, wherein the cover metal layer is formed along a periphery of the light emitting structure.
The method for fabricating a light emitting diode according to claim 9, wherein the cover metal layer is formed to cover a periphery of the reflective metal layer.
The method for fabricating a light emitting diode according to claim 7, wherein the electrode layer fills the second hole to form ohmic contact with the first conductive type semiconductor layer.
The method for fabricating a light emitting diode according to claim 7, wherein the reflective metal layer is formed on a region of the first insulation layer in which the second hole is not formed.
A light emitting diode comprising:

a light emitting structure comprising a second conductive type semiconductor layer, a first conductive type semiconductor layer disposed on the second conductive type semiconductor layer and an active layer interposed between the first and second conductive type semiconductor layers, the light emitting structure having a first hole and a second hole formed through the active layer and the second conductive type semiconductor layer so as to expose the first conductive type semiconductor layer;

a metal layer disposed under the light emitting structure and covering a portion of the light emitting structure;

a first insulation layer disposed under the metal layer and covering the metal layer;

an electrode layer disposed under the first insulation layer and covering the first insulation layer while filling the first and second holes; and

an electrode pad electrically connected to the metal layer,

wherein the electrode layer filling the second hole is a line electrode, the line electrode being formed along a periphery of the light emitting structure to have directionality of one direction in a plan view of the light emitting structure.
The light emitting diode according to claim 13, wherein the electrode layer filling the first hole is a first electrode and the line electrode has a smaller width than the first electrode.
The light emitting diode according to claim 13, wherein the metal layer is disposed inside the line electrode in the plan view of the light emitting structure.
The light emitting diode according to claim 13, wherein the line electrode is formed under the light emitting structure in a region in which the electrode pad is not formed.