High efficiency light-emitting diode

Abstract

Light-emitting diode, comprising: a light-emitting structure (110) having a semiconductor layer (113) of a second conductive type, an active layer (112) arranged on a top surface of the semiconductor layer (113) of the second conductive type, and a semiconductor layer (111) of a first conductive type arranged on a top surface of the active layer (112); at least one first electrode (120) electrically connected to the semiconductor layer (111) of the first conductive type; a current-blocking layer (130) arranged on a bottom side of the light-emitting structure (110); and a second electrode (140) electrically connected to the semiconductor layer (113) of the second conductive type, wherein the second electrode (140) comprises: a first reflective metal layer (141) adjacent to the semiconductor layer (113) of the second conductive type; and a second reflective metal layer (142) covering at least a bottom surface of the first reflective metal layer (141), characterized in that the second reflective metal layer (142) covers a bottom surface of the current-blocking layer (130) and the bottom surface of the first reflective metal layer (141) while adjoining a portion of the semiconductor layer (113) of the second conductive type, and a contact resistance between the second reflective metal layer (142) and the semiconductor layer (113) of the second conductive type is higher than a contact resistance between the first reflective metal layer (141) and the semiconductor layer (113) of the second conductive type.

Description

[Technical field]

[0001] The present invention relates to a light-emitting diode and, more particularly, to a light-emitting diode including a reflective metal layer and thus having improved light extraction efficiency. [Background of the invention]

[0002] A light-emitting diode (LED) is a semiconductor device configured to convert electrical energy into light. Light-emitting diodes are commonly used as light sources for backlighting units, lighting fixtures, signaling panels, large displays, and the like. With the increasing use of LEDs for lighting and the expansion of applications to high-current, high-output devices, there is a need to develop electrode technology to improve the reliability of electrodes that electrically connect an external structure, such as a module, to semiconductor layers of an LED, while improving the light extraction efficiency of the LED. [Revelation][Technical Problem]

[0003] One aspect of the present invention is to provide a light-emitting diode having improved light extraction efficiency by preventing a barrier metal layer from absorbing light.

[0004] Another aspect of the present invention is to provide a light-emitting diode including a region with different electrical junction characteristics on a bottom surface of a semiconductor layer of a second conductive type to improve current spreading efficiency.

[0005] Another aspect of the present invention is to provide a light-emitting diode that can prevent delamination of an electrode connected to a second conductive type semiconductor layer to improve reliability.

[0006] US 2011 / 0 215 352 A1 describes a light-emitting device with a light-emitting structure comprising a semiconductor layer of a second conductive type, an active layer and a semiconductor layer of a first conductive type, a first electrode electrically connected to the semiconductor layer of the first conductive type, a current-blocking layer arranged on a bottom side of the light-emitting structure, and a second electrode electrically connected to the semiconductor layer of the second conductive type, comprising a first reflective metal layer adjacent to the semiconductor layer of the second conductive type and a second reflective metal layer covering the bottom side of the first reflective metal layer. [6a] Further light-emitting devices are disclosed in US 2012 / 0 119 243 A1, US 2007 / 0 290 215 A1 and US 2014 / 0 231 849 A1. [Technical solution]

[0007] The present invention provides a light-emitting diode having the features of claim 1. [Beneficial Effects]

[0008] According to exemplary embodiments, a bottom surface of a second conductive type semiconductor layer of a light-emitting diode contains regions with different electrical junction characteristics, thereby improving current spreading efficiency. With this structure, the light-emitting diode can reduce a forward voltage and increase an output voltage. Furthermore, the light-emitting diode can prevent delamination of a second electrode by ensuring high bonding strength between a current-blocking layer and a second reflective metal layer, thereby improving reliability. [Description of the drawings] Fig. 1 are plan views of a light-emitting diode according to an exemplary embodiment of the present invention. Fig. 2 is a cross-sectional view of the light-emitting diode according to the exemplary embodiment of the present invention. Fig. 3 is an enlarged view of Part I of the Fig. 2. Fig. 4 shows graphs comparing performance of the light-emitting diode according to the exemplary embodiment of the present invention with that of a typical light-emitting diode. Fig. 5 is a sectional view of a light-emitting diode according to another exemplary embodiment of the present invention. Fig. 6 is a sectional view of a light-emitting diode according to another exemplary embodiment of the present invention. Fig. 7 is an exploded perspective view of an embodiment of a lighting device to which a light-emitting diode according to an exemplary embodiment of the present invention is applied. Fig. 8 is a sectional view of an embodiment of a display to which a light-emitting diode according to an exemplary embodiment of the present invention is applied. Fig. 9 is a sectional view of an embodiment of a display to which a light-emitting diode according to an exemplary embodiment of the present invention is applied. Fig. 10 is a sectional view of an embodiment of a headlight to which a light-emitting diode according to an exemplary embodiment of the present invention is applied. [Best Embodiment]

[0009] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example in order to fully convey the essence of the present invention to one skilled in the art to which the present invention belongs. Accordingly, the present invention is not limited to the embodiments disclosed herein and may be implemented in various forms. In the drawings, widths, lengths, thicknesses, and the like of elements may be exaggerated for clarity and descriptive purposes. When an element or layer is referred to as being "disposed over" or "on top of" another element or layer, the same element or layer may be directly "disposed over" or "on top of" the other element or layer, or intervening elements or layers may be present.Throughout the description, similar reference numbers indicate similar elements that have the same or similar functions.

[0010] A light-emitting diode according to an exemplary embodiment of the present invention includes: a light-emitting structure having a semiconductor layer of a second conductive type, an active layer disposed on a top surface of the semiconductor layer of the second conductive type, and a semiconductor layer of a first conductive type disposed on a top surface of the active layer; at least one first electrode electrically connected to the semiconductor layer of the first conductive type; a current-blocking layer disposed on a bottom surface of the light-emitting structure;and a second electrode electrically connected to the second conductive type semiconductor layer, wherein the second electrode includes a first reflective metal layer adjacent to the second conductive type semiconductor layer and a second reflective metal layer covering a bottom surface of the current-blocking layer and a bottom surface of the first reflective metal layer while adjacent to a portion of the second conductive type semiconductor layer, and wherein a contact resistance between the second reflective metal layer and the second conductive type semiconductor layer is higher than a contact resistance between the first reflective metal layer and the second conductive type semiconductor layer;

[0011] The first reflective metal layer may be spaced from the current-blocking layer.

[0012] The second reflective metal layer may include an Al layer, and the Al layer may be adjacent to the current blocking layer, the first reflective metal layer, and the second conductive type semiconductor layer.

[0013] The light-emitting diode may further include a barrier metal layer disposed on a bottom surface of the second reflective metal layer, and the barrier metal layer may include Ni.

[0014] The current-blocking layer may include a first region adjacent to the second conductive type semiconductor layer, the first reflective metal layer may include a second region adjacent to the second conductive type semiconductor layer, the second reflective metal layer may include a third region adjacent to the second conductive type semiconductor layer, and the first region, the second region, and the third region may have different electrical transition characteristics.

[0015] The third region and the second reflective metal layer may form a Schottky junction between them.

[0016] The third area may have a smaller area than the second area.

[0017] A portion of the second reflective metal layer may cover a side surface of the current blocking layer.

[0018] The side surface of the current-blocking layer may contain an inclined surface.

[0019] The second reflective metal layer may include a protrusion that projects beyond a side surface of the light-emitting structure.

[0020] The light-emitting diode may further include an insulating layer arranged on a top surface and a side surface of the light-emitting structure.

[0021] A portion of the current blocking layer may be placed on a top surface of the protrusion.

[0022] The insulating layer and the current-blocking layer can be adjacent to each other.

[0023] The insulating layer and the current-blocking layer can be made of the same material.

[0024] In some exemplary embodiments, the first electrode may include an electrode pad and an upper extension, and the upper extension may include a region that overlaps the current-blocking layer. Further, the current-blocking layer may have a greater width than the upper extension, such that portions of the current-blocking layer are placed beyond both sides of the upper extension in a width direction in a view showing the upper extension overlapping the current-blocking layer. In particular, the portions of the current-blocking layer placed beyond both sides of the upper extension in the width direction may each have the same width as or a greater width than the upper extension.With the structure in which the width of the current-blocking layer is three times or more of the width of the upper extension, the light-emitting diode can achieve current spreading over a wide area thereof, thereby improving the luminous efficiency.

[0025] A light-emitting diode according to another exemplary embodiment of the present invention includes: a light-emitting structure having a semiconductor layer of a second conductive type, an active layer disposed on a top surface of the semiconductor layer of the second conductive type, and a semiconductor layer of a first conductive type disposed on a top surface of the active layer; at least one first electrode disposed on a top surface of the light-emitting structure and electrically connected to the semiconductor layer of the first conductive type; a current-blocking layer disposed on a bottom surface of the light-emitting structure;and a second electrode disposed on a bottom surface of the light-emitting structure and electrically connected to the second conductive type semiconductor layer, wherein the second electrode includes a first reflective metal layer adjacent to the second conductive type semiconductor layer and a second reflective metal layer covering a bottom surface of the current-blocking layer and a bottom surface of the first reflective metal layer, and wherein a bonding strength between the current-blocking layer and the second reflective metal layer is greater than a bonding strength between the current-blocking layer and the first reflective metal layer;

[0026] The second reflective metal layer may contain Al.

[0027] A portion of the second reflective metal layer may cover a side surface of the current blocking layer and separate the current blocking layer from the first reflective metal layer.

[0028] The Fig. 1 to 4 are plan views, a cross-sectional view, and graphs illustrating a light-emitting diode according to an exemplary embodiment of the present invention. Fig. 1(a) is a top view of the light-emitting diode and Fig. 1(b) is a top plan view of a lower structure of a second reflective metal layer of the light-emitting diode, which will be described below. Fig. 2 is a cross-sectional view taken along a line AA' of the Fig. 1 was taken, and Fig. 3 is an enlarged view of part I of the Fig. 2. Fig. 4(a) shows a graph comparing a forward voltage of the light-emitting diode according to the exemplary embodiment with that of a typical light-emitting diode, and Fig. 4(b) shows a graph comparing an output power of the light-emitting diode according to the exemplary embodiment with that of the typical light-emitting diode.

[0029] Regarding the Fig. 1 to 3, the light-emitting diode according to this exemplary embodiment includes a light-emitting structure 110, a first electrode 120, a current-blocking layer 130, and a second electrode 140, and may further include an insulating layer 170 and a substrate 160.

[0030] The light-emitting structure 110 may include a semiconductor layer 113 of a second conductive type, an active layer 112 arranged on top of the semiconductor layer 113 of the second conductive type, and a semiconductor layer 111 of a first conductive type arranged on top of the active layer 112. The semiconductor layer 111 of the first conductive type, the active layer 112, and the semiconductor layer 113 of the second conductive type may include a III-V-based compound semiconductor, for example, a nitride-based semiconductor such as (Al, Ga, In)N. The semiconductor layer 111 of the first conductive type may include an n-type dopant (e.g., Si), and the semiconductor layer 113 of the second conductive type may include a p-type dopant (e.g., Mg), or vice versa. The active layer 112 may have a multiple quantum well (MQW) structure.multi-quantum well structure) and have a composition ratio designed to emit light with a desired peak wavelength. In particular, the active layer 112 may include an InGaN well layer to emit blue light or near-ultraviolet light.

[0031] The light-emitting structure 110 may be formed by sequentially stacking the first conductive type semiconductor layer 111, the active layer 112, and the second conductive type semiconductor layer 113 on a growth substrate (not shown). The growth substrate may be selected from any substrates as long as the substrate allows the growth of the first conductive type semiconductor layer 111, the active layer 112, and the second conductive type semiconductor layer 113 thereon, and may include, for example, a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, an aluminum nitride substrate, a silicon substrate, and the like. In this exemplary embodiment, the growth substrate may specifically be a patterned sapphire substrate (PSS).The growth substrate can be removed from the light-emitting structure, allowing a top surface of the light-emitting structure 110 to have a shape that corresponds to the pattern of the substrate. If the growth substrate includes a rounded pattern, the top surface of the light-emitting structure 110 can also have a rounded shape.

[0032] A side surface of the light-emitting structure 110 may include an inclined surface. With respect to Fig. 2, the inclined surface may have an angle of 90° or smaller, for example, 60°, with respect to a bottom surface of the first conductive type semiconductor layer 111. The inclined surface of the light-emitting structure 110 serves to improve the emission of the light generated in the light-emitting structure 110. The inclined surface may be formed by a dicing process for individually dividing light-emitting diodes or by a separate etching process.

[0033] The first electrode 120 may be arranged on a top surface of the light-emitting structure 110. The number of first electrodes 120 may be at least one, and the first electrode 120 may be electrically connected to the first conductive type semiconductor layer 111. The first electrode 120 may be a single-layer or multi-layer structure made of Ni, Al, Au, Cr, and the like. The first electrode 120 may be formed by depositing a metallic material onto the top surface of the light-emitting structure 110, followed by patterning.

[0034] A bottom surface of the first electrode 120 is adjacent to a top surface of the first conductive type semiconductor layer 111. In a structure where the top surface of the first conductive type semiconductor layer 111 includes a pattern, a top surface of the first electrode 120 may include a shape corresponding to the pattern of the top surface of the first conductive type semiconductor layer 111. For example, in a structure where the top surface of the first conductive type semiconductor layer 111 includes a rounded pattern, the top surface of the first electrode 120 placed on the rounded pattern may also include a rounded shape. With this structure, when connecting a wire to the first electrode 120, the wire can be stably connected to the first electrode 120 via the shape of the top surface of the first electrode 120.

[0035] The first electrode 120 may include at least one bond pad 121 and an upper extension 122.

[0036] The bonding pad 121 serves to conduct the electric current applied to the light-emitting structure 110 to flow outward. In this exemplary embodiment, the bonding pad 121 may be placed near one side of the light-emitting structure 110. In particular, the first conductive type semiconductor layer 111 includes a first side surface 111a and a second side surface 111b positioned opposite the first side surface 111a, and the bonding pad 121 may be placed near the first side surface 111a. While the first electrode is illustrated in this exemplary embodiment as including two bonding pads 121, it should be understood that other implementations are also possible, and the first electrode 120 may include one bonding pad or three or more bonding pads.

[0037] The upper extension 122 may extend from the bonding pad 121. The upper extension 122 serves to prevent current crowding near the bonding pad 121 when current is applied to the light-emitting diode. In particular, a portion of the upper extension 122 may be placed along four sides of the first conductive type semiconductor layer 111. Furthermore, the other portion of the upper extension 122 may be placed between the bonding pads 121 and a portion of the upper extension 122 near the second side surface 111b.

[0038] The current-blocking layer 130 may be placed on a bottom surface of the light-emitting structure 110. The current-blocking layer 130 may at least partially overlap the first electrode 120 in a vertical direction. The current-blocking layer 130 may include a first region 113a adjacent to the semiconductor layer 113 of the second conductive type. The current-blocking layer 130 may serve to prevent the electric current applied to the light-emitting diode from concentrating on the semiconductor layer near the first electrode 120, thereby preventing deterioration in current spreading efficiency. The first region 113a may overlap the first electrode 120 in the vertical direction. This structure can more effectively prevent current concentrating.In particular, the current-blocking layer 130 may be formed to have a larger width than the upper extension 122 to improve luminous efficiency by efficiently spreading the electric current. Specifically, in a view showing the current-blocking layer 130 overlapping the upper extension 122, the portions of the current-blocking layer 130 located beyond both sides of the upper extension 122 in a width direction may each have a larger width than the upper extension 122. Consequently, the width of the current-blocking layer 130 may be greater than three times the width of the upper extension 122 to achieve a significant improvement in luminous efficiency. For example, when the upper extension 122 of the first electrode 120 has a width of 15 μm, the width of the current-blocking layer 130 may be approximatelyexceed 45 µm, and the upper extension 122 may be placed on top of a central region of the current-blocking layer 130. However, since an excessively large width of the current-blocking layer may cause an increase in forward voltage, it is desirable that the width of the current-blocking layer 130 be set to be four times or less the width of an upper extension 121. The adjustment of the widths of the upper extension 122 and the current-blocking layer 130 disposed below the upper extension may be applied to an entire region of the upper extension 122 or applied to a portion thereof.In particular, the width adjustment may be applied to the upper extension 122 and the current-blocking layer 130 placed in the light-emitting diode, rather than along an edge of the light-emitting diode, such as the upper extension 121 connecting a portion of the upper extension 122 placed near the second side surface 111b to the bonding pads 121.

[0039] The current-blocking layer 130 may have insulating properties and may contain an insulating material. For example, the current-blocking layer 130 may contain SiO x or SiN xor a distributed Bragg reflector (DBR) in which material layers with different refractive indices are stacked on top of one another. That is, the current-blocking layer 130 may exhibit a transmittance or reflectivity with respect to light of a specific wavelength. The current-blocking layer 130 may consist of a single layer or multiple layers formed by chemical vapor deposition (CVD) or the like.

[0040] The current-blocking layer 130 may include at least one opening 130a exposing the semiconductor layer 113 of the second conductive type. With respect to Fig. 1(b), the opening 130a may have a rectangular shape or a circular shape, but is not limited thereto. The opening 130a may be formed using a mask or by evaporating the current-blocking layer 130 followed by etching, but is not limited thereto.

[0041] A side surface of the current-blocking layer 130 may include a sloped surface. With respect to the Fig. 2 and Fig. 3, an angle defined between a bottom surface of the current-blocking layer 130 and the side surface of the current-blocking layer 130 can be greater than 90° and less than 180°. In the structure where the side surface of the current-blocking layer 130 includes the sloped surface, a portion of a second reflective metal layer 141 covering the side surface of the current-blocking layer 130 is placed along the sloped side surface of the current-blocking layer 130 and can more effectively reflect light generated by the active layer 112 toward a top surface of the light-emitting structure 110. Furthermore, this structure can increase the interface area between the current-blocking layer 130 and the second reflective metal layer 141, thereby improving the mechanical reliability of the light-emitting diode.

[0042] The second electrode 140 may be placed on the underside of the light-emitting structure 110. The second electrode 140 may be electrically connected to the second conductive type semiconductor layer 113. The second electrode 140 may include a first reflective metal layer 141, a second reflective metal layer 142, and a barrier metal layer 143.

[0043] The first reflective metal layer 141 may be adjacent to the semiconductor layer 113 of a second conductive type. Furthermore, the first reflective metal layer 141 may form an ohmic contact with the semiconductor layer 113 of the second conductive type. The first reflective metal layer 141 includes a second region 113b that forms an ohmic contact with the semiconductor layer 113 of the second conductive type through the opening 130a. The first reflective metal layer 141 may be spaced apart from the current-blocking layer 130.

[0044] The first reflective metal layer 141 may include a metal or alloy capable of reflecting the light emitted by the light-emitting structure 110. For example, the first reflective metal layer 141 may include Ag, Ag alloy, Ni / Ag, NiZn / Ag, TiO / Ag, or Ni / Ag / Ni / Ti layers and may be formed by vapor deposition and patterning. In particular, when the second conductive type semiconductor layer 113 is a p-type semiconductor layer, the Ni layer forms an ohmic contact with the second conductive type semiconductor layer 113. Since the Ni layer degrades the reflectivity of Ag due to low reflectivity with respect to light generated by the light-emitting structure 110, the Ni layer may have a thin thickness.The first reflective metal layer 141 can be formed by electron beam evaporation, vacuum evaporation, sputtering or metal organic chemical vapor deposition (MOCVD).

[0045] The second reflective metal layer 142 may cover the current-blocking layer 130 and the first reflective metal layer 141. Specifically, the second reflective metal layer 142 may be placed to cover a bottom and side surface of the current-blocking layer 130 and a bottom and side surface of the first reflective metal layer 141. The second reflective metal layer 142 may be adjacent to the current-blocking layer 130 and the first reflective metal layer 141. Furthermore, the second reflective metal layer 142 may be adjacent to a portion of the second conductive type semiconductor layer 113 through the opening 130a.In particular, the second reflective metal layer 142 may include a third region 113c formed by separating between the first reflective metal layer 141 and the current blocking layer 130 and exposing a bottom surface of the second conductive type semiconductor layer 113.

[0046] The second reflective metal layer 142 may be placed between the current blocking layer 130 and the barrier metal layer 143, which will be described below, and / or placed between the first reflective metal layer 141 and the barrier metal layer 143.

[0047] The second reflective metal layer 142 may contain a metal with a different reflectivity than the metal of the first reflective metal layer 141. If the first reflective metal layer 141 contains Ag, the second reflective metal layer 142 may, in particular, contain Al. Ag has a reflectivity of approximately 98.9%, and Al has a reflectivity of approximately 90.3%.

[0048] Regarding the Fig. 1 to 3, the first region 113a, the second region 113b, and the third region 113c may have different electrical transition characteristics and may have different reflection characteristics. In particular, the first region 113a, the second region 113b, and the third region 113c may have different contact resistances due to their different electrical transition characteristics.

[0049] The contact resistance of the third region 113c, that is, the second reflective metal layer 142 and the second conductive-type semiconductor layer 113, can be higher than the contact resistance of the second region 113b, that is, the first reflective metal layer 141 and the second conductive-type semiconductor layer 113. With this structure, the second reflective metal layer 142 can serve to reflect light while reducing a forward voltage by current spreading.

[0050] The second reflective metal layer 142 may be formed from a metal with a higher work function than the first reflective metal layer 141. In particular, the second reflective metal layer 142 may form a Schottky junction with the second conductive type semiconductor layer 113. Increasing the area of the first region 113a, where the current-blocking layer 130 adjoins the second conductive type semiconductor layer 113, may cause a deterioration in light extraction efficiency by reducing a reflective area of the second electrode 140. Conversely, reducing the area of the first region 113a may cause a deterioration in the current spreading efficiency of the light-emitting diode.In the structure where the second reflective metal layer 142 forms a Schottky junction with the third region 113c, most of the current can be applied to the second electrode 140 through the second region 113b, which forms the ohmic contact. Since the third region 113c can also reflect light generated in the light-emitting structure 110, this structure can further improve current spreading and light extraction efficiency while minimizing the area of the current-blocking layer 130.

[0051] With the structure in which the second reflective metal layer 142 contains Al, the light-emitting diode can be further configured to have an ohmic contact between the second reflective metal layer 142 and the second conductive type semiconductor layer 113. However, in this structure, to form the ohmic contact between the second reflective metal layer 142 and the second conductive type semiconductor layer 113, it is necessary to perform a heat treatment at a high temperature of 700°C or more. As a result, there may be a problem of damage to the light-emitting structure 110 due to heat.However, in exemplary embodiments of the invention, the second reflective metal layer 142 forms a Schottky junction with the second conductive type semiconductor layer 113 instead of an ohmic contact, as long as the second reflective metal layer 142 has light reflection characteristics. As a result, the exemplary embodiments can omit heat treatment with respect to the first reflective metal layer 142 while maximizing reflection of light by the second electrode 140 when generating light in the light-emitting structure 110. That is, compared to the structure in which the second reflective metal layer 142 is omitted, an effective area of the second electrode 140 capable of reflecting light can be increased, thereby improving light extraction efficiency.

[0052] The third region 113c may have a smaller area than the second region 113b. Since the third region 113c, which forms a Schottky junction with the second conductive type semiconductor layer 113, has a small area, the overall resistance of the light-emitting diode can be reduced, and a forward voltage (Vf) can be further reduced.

[0053] In the structure where the current-blocking layer 130 has a distributed Bragg reflector (DBR), the current-blocking layer 130 can reflect light in a broad wavelength band. In particular, when the active layer 112 emits light, such as near-UV light, the light can be reflected by the distributed Bragg reflector (DBR), thereby improving the light extraction efficiency. On the other hand, the second reflective metal layer 142 disposed under the current-blocking layer 130 reflects light that passes through the current-blocking layer 130, thereby improving the light extraction efficiency. In the structure where the current-blocking layer 130 is the distributed Bragg reflector (DBR), in particular, the second reflective metal layer 142 and the current-blocking layer 130 can reflect light in substantially the entire wavelength band emitted by the active layer 112.For example, when light emitted from the active layer 112 is near-UV light, it is possible to maintain high reflectivity through the current-blocking layer 130 and the second reflective metal layer 142. Furthermore, a combination of the second reflective metal layer 142 and the current-blocking layer 130 can maintain high reflectivity with respect to light entering the current-blocking layer 130 at different angles of incidence.

[0054] The bonding strength between the second reflective metal layer 142 and the current-blocking layer 130 may be greater than the bonding strength between the first reflective metal layer 141 and the current-blocking layer 130. Specifically, in the structure where the first reflective metal layer 141 contains Ag and the second reflective metal layer 142 contains Al, a bonding strength between Al of the second reflective metal layer 142 and the current-blocking layer 130 may be greater than that between Ag of the first reflective metal layer 141 and the current-blocking layer 130. A portion of the second reflective metal layer 142 may cover the bottom and side surfaces of the current-blocking layer 130. In this structure, light passing through the bottom and side surfaces of the current-blocking layer 130 can be reflected by the second reflective metal layer 142.Furthermore, since the current-blocking layer 130 is adjacent to the second reflective metal layer 142 instead of the first reflective metal layer 141 having a low bonding strength with respect to the current-blocking layer 130, the light-emitting diode has improved reliability by solving the problem of delamination of the second electrode 140 from the current-blocking layer 130.

[0055] The second reflective metal layer 142 may be formed by electron beam evaporation, vacuum evaporation, sputtering, or metal organic chemical vapor deposition (MOCVD).

[0056] The barrier metal layer 143 can be placed on the underside of the second reflective metal layer 142. The barrier metal layer 143 can be spaced apart from the first reflective metal layer 141 and the current-blocking layer 130 by the second reflective metal layer 142. In a structure where the barrier metal layer 143 is adjacent to the current-blocking layer 130, light passing through the current-blocking layer 130 can be absorbed in the barrier metal layer 143. However, since the second reflective metal layer 142, which has a higher reflectivity than the barrier metal layer 143, is disposed between the current-blocking layer 130 and the barrier metal layer 143, it is possible to prevent light loss caused by light absorption by the barrier metal layer 143.

[0057] The barrier metal layer 143 serves to prevent the Ag of the first reflective metal layer 141 from diffusing to the outside of the first reflective metal layer. The barrier metal layer 143 can be formed from Ni, Cr, Ti, Pt, Au, or combinations thereof. Fig. 3, the barrier metal layer 143 may, for example, include a structure in which a Ni layer 143a and a Ti layer 143b are repeatedly stacked. Since the barrier metal layer 143, particularly the Ni layer 143a, has a high reflectivity with respect to light emitted from the active layer 112, there is a need to prevent light emitted from the active layer 112 from entering the Ni layer 143a. To this end, according to exemplary embodiments, the second reflective metal layer 142 is disposed between the current-blocking layer 130 and the barrier metal layer 143 while being adjacent to the second conductive type semiconductor layer 113 to prevent direct contact between the Ni layer 143a and the second conductive type semiconductor layer 113.The barrier metal layer 143 can be formed by electron beam evaporation, vacuum evaporation, sputtering, or metal organic chemical vapor deposition (MOCVD).

[0058] The light-emitting diode according to this exemplary embodiment may further include the insulating layer 170. The insulating layer 170 may be arranged on a top and side surfaces of the light-emitting structure 110. The insulating layer 170 serves to protect the light-emitting structure 110 from external influences and contamination. The insulating layer 170 may include at least one opening 170a exposing the first electrode 120. The first electrode 120 may be exposed through the opening 170a to be connected to a wire and the like. The insulating layer 170 may be SiO x or SiN xThe insulating layer 170 may be formed from the same material as the current-blocking layer 130.

[0059] The light-emitting diode according to this exemplary embodiment may further include the substrate 160. The substrate 160 may be arranged on a bottom surface of the barrier metal layer 143. The substrate 160 may serve to protect the barrier metal layer 143. In addition, the substrate 160 may serve to hold the light-emitting structure 110 upon separation of a substrate (not shown) from the light-emitting structure 110. The substrate 160 may contain a conductive metal, such as Cu. Fig. 2, the substrate 160 can be arranged on the underside of the barrier metal layer 143 over a bonding material 150. The bonding material 150 can, for example, contain bonding metals such as AuSn.

[0060] In relation to Fig. 4, the light-emitting diode according to the present invention has better characteristics with regard to the forward voltage V f and the output power as a typical light-emitting diode. Specifically, the light-emitting diode according to the present invention was used as an inventive example, and a typical light-emitting diode having the same structure as the light-emitting diode according to the present invention except for the second reflective metal layer 142 was used as a comparative example. Both light-emitting diodes had a size of 1,000 µm x 1,000 µm, the first reflective metal layer 141 consisted of Ni / Ag / Ni / Ti layers (3 Å / 2,000 Å / 200 Å / 3,000 Å), the current-blocking layer 130 consisted of SiO2 (8,000 Å), the barrier metal layer 143 consisted of Ti / Ni layers (14 layers, 1.4 µm) and Au (50 Å), and the second reflective metal layer 142 of the light-emitting diode of the inventive example consisted of Al (2,000 Å).

[0061] Since the light-emitting diode of the invention example had a forward voltage of 3.041 V and the light-emitting diode of the comparative example had a forward voltage of 3.104 V, with respect to Fig. 4(a) that the light-emitting diode according to the present invention has a reduced forward voltage. Since the light-emitting diode of the invention example had an output power of 621.6 mW and since the light-emitting diode of the comparative example had an output power of 615.7 mW, Fig. 4(b) that the light-emitting diode according to the present invention exhibits increased output power. This result demonstrates that the second reflective metal layer 142 can serve to improve the light extraction efficiency of the light-emitting diode.

[0062] On the other hand, the forward voltage V fand the luminous efficiency was measured with the width of the upper extension 122 set at 15 µm, while the width of the current-blocking layer 130 was varied to 23 µm, 30 µm, 50 µm, and 70 µm. With respect to a value obtained by setting the width of the current-blocking layer to 23 µm, as the width of the current-blocking layer 130 increased, the luminous efficiency increased and the forward voltage increased slightly. In particular, when the current-blocking layer 130 had a width of 50 µm, the forward voltage V increased. f by less than 1% and the luminous efficacy increased significantly by about 3.2%.

[0063] Fig. 5 is a sectional view of a light-emitting diode according to another exemplary embodiment of the present invention. The light-emitting diode of Fig. 5 is similar to that in relation to the Fig. 1 to 3, except that a top surface of the first conductive type semiconductor layer 111 includes a rough surface R. The rough surface R serves to prevent light generated in the light-emitting structure 110 from returning to the inside of the light-emitting diode by reflection by the top surface of the first conductive type semiconductor layer 111, thereby improving the light extraction efficiency of the light-emitting diode. In particular, a portion of the top surface of the first conductive type semiconductor layer 111 that is not adjacent to the first electrode 120 may include the rough surface R.In a structure in which a portion of the top surface of the light-emitting structure 110 having the first electrode 120 disposed thereon, that is, a portion of the top surface of the first conductive type semiconductor layer 111 adjacent to the bottom surface of the first electrode 120, includes the rough surface R, the material of the first electrode 120 may be diffused to an excessively deep portion in the light-emitting structure 110 along the rough surface R. As a result, the light-emitting diode may have a reduced internal quantum efficiency, thereby lowering the reliability of the light-emitting diode.

[0064] Fig. 6 is a sectional view of a light-emitting diode according to another exemplary embodiment of the present invention. The light-emitting diode of Fig. 6 is similar to that in terms of Fig. 1 to 3, except that side surfaces of the second reflective metal layer 142 protrude beyond the side surfaces of the light-emitting structure 110. In particular, the second reflective metal layer 142 may include a protrusion P that protrudes beyond the side surfaces of the light-emitting structure 110. An upper surface of the second reflective metal layer 142 may have a wider area than the bottom surface of the light-emitting structure 110. With this structure, a portion of the light emitted by the side surfaces of the light-emitting structure 110 may be reflected toward an upper portion of the light-emitting diode by the second reflective metal layer 142. Consequently, the light-emitting diodes may have improved light extraction efficiency.

[0065] In relation to Fig. 6, a portion of the current-blocking layer 130 can be placed on a top surface of the protrusion P. With this structure, the top surface of the protrusion P can be protected from external influences and contaminants. Furthermore, the insulating layer 170 can be adjacent to the current-blocking layer 130. In particular, a portion of the insulating layer 170 can be adjacent to the current-blocking layer 130 arranged on the top surface of the protrusion P. With this structure, a distance from a side surface of the insulating layer 170 or a side surface of the current-blocking layer 130 to the light-emitting structure 110 can be increased, thereby preventing external contaminants from entering the light-emitting diode while more effectively protecting the light-emitting structure 110 from external influences. The insulating layer 170 and the current-blocking layer 130 can be formed from the same material.For example, if the current-blocking layer 130 is formed from SiO2, the insulating layer 170 may also be formed from SiO2. With this structure, a high bonding strength can be created between the insulating layer 170 and the current-blocking layer 130, thereby preventing delamination of the insulating layer 170 or the current-blocking layer 130, while more effectively preventing external impurities from entering the light-emitting diode.

[0066] Fig. 7 is an exploded perspective view of an embodiment of a lighting device to which a light-emitting diode according to an exemplary embodiment of the invention is applied.

[0067] In relation to Fig. 7, the lighting device according to this embodiment includes a diffusion cover 1010, a light-emitting diode module 1020, and a body 1030. The body 1030 can accommodate the light-emitting diode module 1020, and the diffusion cover 1010 can be arranged on the body 1030 to cover an upper side of the light-emitting diode module 1020.

[0068] The body 1030 may have any shape as long as the body can supply electric power to the light-emitting diode module 1020 while accommodating and supporting the light-emitting diode module 1020. As shown in the drawing, the body 1030 may include, for example, a body case 1031, a power supply 1033, a power supply case 1035, and a power source connecting portion 1037.

[0069] The power supply 1033 is housed in the power supply housing 1035 to be electrically connected to the light-emitting diode module 1020, and may include at least one integrated circuit chip. The integrated circuit chip can regulate, change, or control electrical power applied to the light-emitting diode module 1020. The power supply housing 1035 can accommodate and store the power supply 1033. The power supply housing 1035, having the power supply 1033 mounted therein, can be arranged within the body housing 1031. The power source connecting portion 1037 is arranged at a lower end of the power supply housing 1035 and connected thereto.Consequently, the power source connecting portion 1037 is electrically connected to the power supply 1033 within the power supply housing 1035 and can serve as a passage through which power can be applied from an external power source to the power supply 1033.

[0070] The light-emitting diode module 1020 includes a substrate 1023 and a light-emitting diode 1021 disposed on the substrate 1023. The light-emitting diode module 1020 can be disposed at an upper portion of the body case 1031 and electrically connected to the power supply 1033.

[0071] Any substrate capable of supporting the light-emitting diode 1021 can be used as the substrate 1023 without limitation. For example, the substrate 1023 may include a circuit board having connections formed thereon. The substrate 1023 may have a shape corresponding to a fixing portion formed on the upper portion of the body casing 1031 for being stably fixed to the body casing 1031. The light-emitting diode 1021 may include at least one of the light-emitting diodes according to the embodiments described above.

[0072] The diffusion cover 1010 is disposed on the light-emitting diode 1021 and can be attached to the body casing 1031 to cover the light-emitting diode 1021. The diffusion cover 1010 can be formed of a light-transmitting material, and a light orientation of the lighting device can be adjusted by regulating the shape and optical transmittance of the diffusion cover 1010. As such, the diffusion cover 1010 can be modified into various shapes depending on a use and application of the lighting device.

[0073] Fig. 8 is a sectional view of an embodiment of a display to which a light-emitting diode according to an exemplary embodiment of the invention is applied.

[0074] The display according to this embodiment includes a display panel 2110, a backlight unit BLU1 that supplies light to the display panel 2110, and a panel guide 2100 that supports a lower edge of the display panel 2110.

[0075] The display panel 2110 is not particularly limited and may, for example, be a liquid crystal panel including a liquid crystal layer. Gate driver PCBs may also be arranged at the edge of the display panel 2110 to apply drive signals to a gate line. Here, the gate driver PCBs 2112 and 2113 may be formed on a thin-film transistor substrate instead of being formed on separate PCBs.

[0076] The backlight unit BLU1 includes a light source module including at least a substrate 2150 and a plurality of light-emitting diodes 2160. The backlight unit BLU1 may further include a bottom cover 2180, a reflective film 2170, a diffusion plate 2131, and optical films 2130.

[0077] The bottom cover 2180 may be open at an upper side thereof to accommodate the substrate 2150, the light-emitting diodes 2160, the reflective film 2170, the diffusion plate 2131, and the optical films 2130. Furthermore, the bottom cover 2180 may be connected to the field guide 2100. The substrate 2150 may be disposed under the reflective film 2170 to be surrounded by the reflective film 2170. Alternatively, if a reflective material is applied to a surface thereof, the substrate 2150 may be disposed on the reflective film 2170. Furthermore, a plurality of substrates 2150 may be arranged parallel to each other. However, it should be understood that other implementations are also possible, and the light source module may include a single substrate.

[0078] The light-emitting diodes 2160 may include at least one of the light-emitting diodes according to the embodiments described above. The light-emitting diodes 2160 may be regularly arranged in a predetermined pattern on the substrate 2150. Furthermore, a lens 2210 is arranged on each light-emitting diode 2160 to improve the uniformity of the light emitted by the plurality of light-emitting diodes 2160.

[0079] The diffusion plate 2131 and the optical films 2130 are arranged on the light-emitting devices 2160. The light emitted by the light-emitting devices 2160 can be supplied to the display panel 2110 through the diffusion plate 2131 and the optical films 2130 in the form of planar light.

[0080] In this way, the light-emitting diodes according to the embodiments can be applied to direct type displays such as the display according to this embodiment.

[0081] Fig. 9 is a sectional view of an embodiment of a display to which a light-emitting diode according to an exemplary embodiment of the invention is applied.

[0082] The display according to this embodiment includes a display panel 3210 on which an image is displayed, and a backlight unit BLU2 disposed on a back side of the display panel 3210 and emitting light thereto. Furthermore, the display includes a frame 240 that supports the display panel 3210 and accommodates the backlight unit BLU2, and covers 3240, 3280 that surround the display panel 3210.

[0083] The display panel 3210 is not particularly limited and may, for example, be a liquid crystal panel including a liquid crystal layer. A gate driver PCB may be further disposed at an edge of the display panel 3210 to apply drive signals to a gate line. Here, the gate driver PCB may be formed from a thin-film transistor substrate instead of being formed on a separate PCB. The display panel 3210 is fixed by the covers 3240, 3280 disposed on the upper and lower sides thereof, and the cover 3280 disposed on the lower side of the display panel 3210 may be connected to the backlight unit BLU2.

[0084] The backlight unit BLU2, which supplies light to the display panel 3210, includes a lower cover 3270 partially open on an upper side thereof, a light source module disposed on one side of the lower cover 3270, and a light guide plate 3250 disposed parallel to the light source module and converting point light into area light. In addition, the backlight unit BLU2 according to this embodiment may further include optical sheets 3230 disposed on the light guide plate 3250 to scatter and collect light, and a reflective sheet 3260 disposed on a lower side of the light guide plate 3250 and reflecting light traveling in a downward direction of the light guide plate 3250 toward the display panel 3210.

[0085] The light source module includes a substrate 3220 and a plurality of light-emitting diodes 3110 arranged at constant intervals on a surface of the substrate 3220. Any substrate capable of supporting and electrically connecting the light-emitting diodes 3110 can be used as the substrate 3220 without limitation. For example, the substrate 3220 may include a circuit board. The light-emitting diodes 3110 may include at least one of the light-emitting diodes according to the exemplary embodiments described above. Light emitted from the light source module enters the light guide plate 3250 and is supplied to the display panel 3210 through the optical sheets 3230. The light guide plate 3250 and the optical sheets 3230 convert point light emitted by the light-emitting diodes 3110 into planar light.

[0086] In this way, the light-emitting diodes according to the embodiments can be applied to edge displays such as the display according to this embodiment.

[0087] Fig. 10 is a sectional view of an embodiment of a headlight to which a light-emitting diode according to an exemplary embodiment of the invention is applied.

[0088] In relation to Fig. 10, the headlight according to this embodiment includes a lamp body 4070, a substrate 4020, a light-emitting diode 4010, and a cover lens 4050. The headlight may further include a heat dissipation unit 4030, a support frame 4060, and a connecting member 4040.

[0089] The substrate 4020 is fixed by the support frame 4060 and arranged over the lamp body 4070. Any element capable of supporting the light-emitting diode 4010 can be used as the substrate 4020 without limitation. For example, the substrate 4020 may include a substrate having a circuit pattern, such as a printed circuit board. The light-emitting diode 4010 is arranged on the substrate 4020 and can be supported and fixed by the substrate 4020. In addition, the light-emitting diode 4010 can be electrically connected to an external power source through the circuit pattern of the substrate 4020. Furthermore, the light-emitting diode 4010 may include at least one of the light-emitting diodes according to the exemplary embodiments described above.

[0090] The cover lens 4050 is arranged on a path of the light emitted by the light-emitting diode 4010. As shown in the drawing, for example, the cover lens 4050 can be spaced from the light-emitting diode 4010 by the connecting member 4040 and arranged in a direction for supplying the light emitted by the light-emitting diode 4010. The cover lens 4050 can adjust an orientation angle and / or a color of the light emitted by the headlight. On the other hand, the connecting member 4040 is arranged to fix the cover lens 4050 to the substrate 4020 while surrounding the light-emitting diode 4010, and thus can function as a light guide that provides a light path 4045. The connecting member 4040 can be formed of or coated with a light-reflecting material.On the other hand, the heat dissipation unit 4030 may include heat dissipation fins 4031 and / or a heat dissipation fan 4033 and dissipates heat generated when the light-emitting diode 4010 is actuated.

[0091] In this way, the light-emitting diodes according to the exemplary embodiment can be applied to headlights, in particular headlights for vehicles, such as the headlight according to this embodiment.

Claims

[1] Light-emitting diode, comprising: a light-emitting structure (110) having a semiconductor layer (113) of a second conductive type, an active layer (112) arranged on a top surface of the semiconductor layer (113) of the second conductive type, and a semiconductor layer (111) of a first conductive type arranged on a top surface of the active layer (112); at least one first electrode (120) electrically connected to the semiconductor layer (111) of the first conductive type; a current-blocking layer (130) arranged on a bottom side of the light-emitting structure (110); and a second electrode (140) electrically connected to the semiconductor layer (113) of the second conductive type, wherein the second electrode (140) comprises: a first reflective metal layer (141) adjacent to the semiconductor layer (113) of the second conductive type; and a second reflective metal layer (142) covering at least a bottom surface of the first reflective metal layer (141), characterized by , that the second reflective metal layer (142) covers a bottom surface of the current-blocking layer (130) and the bottom surface of the first reflective metal layer (141) while adjoining a portion of the semiconductor layer (113) of the second conductive type, and a contact resistance between the second reflective metal layer (142) and the semiconductor layer (113) of the second conductive type is higher than a contact resistance between the first reflective metal layer (141) and the semiconductor layer (113) of the second conductive type. [2] The light-emitting diode of claim 1, wherein the first reflective metal layer (141) is spaced from the current-blocking layer (130). [3] The light-emitting diode according to claim 1, wherein the second reflective metal layer (142) comprises an Al layer, the Al layer being adjacent to the current-blocking layer (130), the first reflective metal layer (141) and the second conductive type semiconductor layer (113). [4] The light-emitting diode of claim 3, further comprising: a barrier metal layer (143) arranged on a bottom surface of the second reflective metal layer (142), wherein the barrier metal layer comprises Ni. [5] The light-emitting diode according to claim 3, wherein the current-blocking layer (130) has a first region (113a) adjacent to the semiconductor layer (113) of the second conductive type, the first reflective metal layer (141) has a second region (113b) adjacent to the semiconductor layer (113) of the second conductive type, and the second reflective metal layer (142) has a third region (113c) adjacent to the semiconductor layer (113) of the second conductive type, the first region (113a), the second region (113b) and the third region (113c) having different electrical junction characteristics. [6] The light-emitting diode according to claim 5, wherein the third region (113c) and the second reflective metal layer (142) form a Schottky junction therebetween. [7] A light-emitting diode according to claim 6, wherein the third region (113c) has a smaller area than the second region (113b). [8] The light-emitting diode of claim 1, wherein a portion of the second reflective metal layer (142) covers a side surface of the current-blocking layer (130). [9] A light-emitting diode according to claim 8, wherein the side surface of the current-blocking layer (130) has an inclined surface [10] The light-emitting diode according to claim 1, wherein the second reflective metal layer (142) has a protrusion (P) projecting beyond a side surface of the light-emitting structure (110). [11] The light-emitting diode of claim 10, wherein a portion of the current-blocking layer (130) is placed on a top surface of the protrusion (P). [12] The light-emitting diode of claim 10, further comprising: an insulating layer (170) arranged on a top surface and a side surface of the light-emitting structure (110). [13] The light-emitting diode of claim 12, wherein the insulating layer (170) and the current-blocking layer (130) are adjacent to each other. [14] The light-emitting diode according to claim 13, wherein the insulating layer (170) and the current-blocking layer (130) are formed of the same material. [15] The light-emitting diode according to claim 1, wherein the first electrode (120) has an electrode pad (121) and an upper extension (122), wherein the upper extension (122) has a region that overlaps the current-blocking layer (130), wherein the current-blocking layer (130) has a greater width than the upper extension (122) such that portions of the current-blocking layer (130) are placed beyond both sides of the upper extension (122) in a width direction in a view showing the upper extension (122) overlapping the current-blocking layer (130), and wherein the portions of the current-blocking layer (130) placed beyond both sides of the upper extension (122) in the width direction each have the same width as the upper extension (122) or a greater width than the same.

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