Light-emitting diode with improved light extraction efficiency

Abstract

Light-emitting diode (LED) including: a substrate (21); a light-emitting arrangement arranged on the substrate (21), wherein the light-emitting arrangement comprises a semiconductor layer of the first conductivity type (23), an active layer (25) and a semiconductor layer of the second conductivity type (27); a first electrode field (35) electrically connected to the semiconductor layer of the first conductivity type (23), a second electrode field (33) arranged above the substrate (21); at least one upper extension (33a) connected to the second electrode field (33) in such a way that it is electrically connected to the semiconductor layer of the second conductivity type (27); and a structure of light extraction elements (LEE) arranged on the semiconductor layer of the second conductivity type (27); characterized by a reflective insulating layer (31) that covers part of the light-emitting structure and is arranged under the second electrode field (33) such that the second electrode field (33) is spaced apart from the light-emitting arrangement; wherein the semiconductor layer of the first conductivity type (23) has an exposed area by mesa etching of the semiconductor layer of the second conductivity type (27) and the active layer (25), the second electrode field (33) is arranged on the exposed area of ​​the semiconductor layer of the first conductivity type (23), and the reflective insulating layer (31) is arranged between the second electrode field (33) and the semiconductor layer of the first conductivity type (23).

Description

[Technical field]

[0001] The present invention relates to a light-emitting diode and in particular to a light-emitting diode with improved light extraction efficiency. [State of the art]

[0002] Since the development of gallium nitride (GaN) based light-emitting diodes (LEDs), GaN-based LEDs are currently finding diverse applications, such as colorful LED displays, LED traffic lights and white LEDs.

[0003] A GaN-based LED is generally formed by epitaxial growth of layers on a substrate, such as a sapphire substrate, and comprises an n-type semiconductor layer, a p-type semiconductor layer, and an active layer sandwiched between them. An n-type electrode field is generated on the n-type semiconductor layer, and a p-type electrode field is generated on the p-type semiconductor layer. The LED is powered by an external current source via these electrode fields. In this case, the current flows through the semiconductor layers from the p-type electrode field to the n-type electrode field.

[0004] Since p-type semiconductor layers generally have a high resistivity, the current does not spread uniformly throughout the layer but rather concentrates in the area where the p-type electrode field is present. Additionally, the current flows concentrated along an edge of the LED. This current concentration reduces the light-emitting area and results in lower luminous efficacy. To address this issue, a current distribution technique is employed by creating a transparent electrode layer with low resistivity on top of the p-type semiconductor layer. Because the current introduced by the p-type electrode field spreads through this transparent electrode layer and is then introduced into the p-type semiconductor layer, the light-emitting area of ​​the LED can be expanded.However, since the transparent electrode layer absorbs light, its thickness is limited, and therefore there is a limitation on current propagation. Specifically, there is a current distribution limitation of approximately 1 mm when using a transparent electrode layer in a large-format, high-power LED. 2 or more.

[0005] Currently, extending projections radiating from the electrode fields are used to promote current propagation in an LED. For example, US Patent No. 6,650,018 discloses that a plurality of projections extend from the electrode contact parts 117, 127 in opposite directions to each other, thus improving current propagation. Although the current can be distributed over a large area of ​​an LED using the plurality of projections, current still accumulates in the areas where the electrode fields are positioned.

[0006] As the size of the LED increases, the likelihood of a defect within the LED increases. For example, a defect such as a dislocation line or a pinhole creates a path along which the current flows rapidly, thus disrupting current propagation.

[0007] Nowadays, a structured sapphire substrate is generally used to improve the light extraction efficiency of an LED. A pattern on the sapphire substrate scatters or reflects the light generated in an active layer in such a way that the light loss due to total internal reflection in the LED is reduced, and consequently the light extraction efficiency is improved.

[0008] The light extraction efficiency is expected to improve using the pattern on the sapphire substrate. However, since the refractive index of a GaN-based semiconductor compound layer is relatively high, some light is still likely to be lost through total internal reflection within the LED.

[0009] Since the electrode fields are generally made of a metallic material that absorbs light, the light propagating towards the electrode fields is also absorbed by the electrode fields and lost.

[0010] Therefore, it is constantly necessary to strive for an improvement in light extraction efficiency.

[0011] Furthermore, from US 2008 / 0308833A1, a light-emitting diode is known, comprising a substrate, a light-emitting arrangement arranged on the substrate, wherein the light-emitting arrangement has a semiconductor layer of the first conductivity type, an active layer and a semiconductor layer of the second conductivity type, a first electrode field electrically connected to the semiconductor layer of the first conductivity type, a second electrode field arranged above the substrate, at least one upper extension which is connected to the second electrode field in such a way that it is electrically connected to the semiconductor layer of the second conductivity type; and a structure of light extraction elements which is arranged on the semiconductor layer of the second conductivity type.

[0012] US 2009 / 0108250 A1 discloses a gallium nitride (GaN)-based LED. JP 2005-19646 A relates to a light-emitting device in which an electrode is extended and connected to the element contained therein, and US 2009 / 008672 A1 discloses a light-emitting device comprising a transparent electrode, wherein a titanium oxide-based conductive film is used for at least one layer of the transparent electrode. [Disclosure of the invention][Technical problem]

[0013] One object of the present invention is to provide an LED with improved light extraction efficiency. Another object of the invention is to provide an LED that prevents current from accumulating in the vicinity of an electrode field.

[0014] Another object of the present invention is to provide a large-area LED that can distribute the current evenly in the LED.

[0015] Furthermore, it is an object of the present invention to provide an LED that can reduce light loss due to an electrode field.

[0016] The problem is solved by a light-emitting diode with the features of claim 1. Advantageous further developments are found in the dependent claims. [Technical solution]

[0017] According to one aspect of the present invention, an LED is provided comprising: a substrate; a light-emitting arrangement arranged on the substrate, wherein the light-emitting arrangement comprises a semiconductor layer of a first conductivity type, an active layer, and a semiconductor layer of a second conductivity type; a first electrode array electrically connected to the semiconductor layer of the first conductivity type; a second electrode array arranged above the substrate; at least one extension connected to the second electrode array in such a way as to be electrically connected to the semiconductor layer of the second conductivity type; and a structure of light extraction elements arranged above the semiconductor layer of the second conductivity type.According to the invention, a reflective insulating layer covers a portion of the light-emitting arrangement and is positioned beneath the second electrode array such that the second electrode array is spaced apart from the light-emitting arrangement. Furthermore, the semiconductor layer of the first conductivity type has an area exposed by mesa etching of the semiconductor layer of the second conductivity type and the active layer. The second electrode array is positioned on the exposed area of ​​the semiconductor layer of the first conductivity type, and the reflective insulating layer is positioned between the second electrode array and the semiconductor layer of the first conductivity type.

[0018] Since the second electrode surface is separated from the light-emitting arrangement by the reflective insulating layer, it is possible to prevent current from accumulating around the second electrode field, thereby improving current distribution efficiency.

[0019] Furthermore, the reflective insulating layer reflects the light propagating towards the second electrode field, thereby reducing light loss caused by the second electrode field. Additionally, the light extraction element structure on the semiconductor layer of the second conductivity type is arranged so that it faces the substrate, allowing light to be easily emitted through the structure and thus improving light extraction efficiency. This light extraction element structure can, for example, be used in combination with a structure formed on a sapphire substrate.

[0020] Despite the lack of any specific restrictions, the semiconductor layer of the first conductivity type can be an n-type nitride semiconductor layer, and the semiconductor layer of the second conductivity type can be a p-type nitride semiconductor layer. Additionally, the LED can further include a transparent electrode layer arranged on the p-type nitride semiconductor layer, and the upper extension can be connected to the transparent electrode layer.

[0021] In some embodiments, the structure of light extraction elements can be formed on the transparent electrode layer. The structure of the light extraction elements can be formed, for example, by structuring an upper part of the transparent electrode layer.

[0022] However, the LED can still include an insulating layer covering the transparent electrode layer. In this case, the insulating layer can have an opening to expose the transparent electrode layer, and the upper extension can be connected to the transparent electrode layer through this opening.

[0023] Furthermore, the opening can be positioned so that it is spaced away from the second electrode field. Accordingly, the upper extension, which is connected to the transparent electrode layer through the opening, is connected to the second electrode field via a connecting element located on the insulating layer. Since the connecting element is located on the insulating layer, the upper extension is not directly connected to the transparent electrode layer surrounding the second electrode field, thus preventing further current accumulation near the second electrode field.

[0024] In some embodiments, the structure can be formed from the light extraction elements on the insulating layer. For example, the structure can be formed from the light extraction elements by structuring an upper part of the insulating layer.

[0025] The reflective insulating layer can cover at least part of the side faces of the second conductivity type semiconductor layer and the active layer that have been exposed by mesa etching. Thus, the reflective insulating layer can reflect the light generated in the active layer in such a way that it propagates towards the second electrode field through the mesa faces, thereby preventing light loss caused by the second electrode field.

[0026] The LED can still include a connecting element to link the upper extension to the second electrode array, and this connecting element can be separated from the second-type semiconductor layer by an insulating layer. For example, the connecting element can be isolated from the mesa sidewalls by the reflective insulating layer. Furthermore, the connecting element can be isolated from a top surface of the second-type semiconductor layer (or the transparent electrode layer) by another insulating layer.

[0027] In some embodiments, the semiconductor layer of the second conductivity type and the active layer can be subdivided to define at least two light-emitting regions, and the upper extensions connected to the second electrode field can be arranged on the corresponding at least two light-emitting regions.

[0028] The light-emitting arrangement is divided into a multitude of light-emitting regions, so that even if a defect exists at a specific location, such as a pinhole or dislocation line, it is possible to prevent excessive current accumulation at the defect. Thus, current can be distributed evenly over a large area.

[0029] The at least two light-emitting regions can be symmetrical with respect to a straight line that crosses the first and second electrode surfaces. Accordingly, the at least two light-emitting regions can have the same light emission characteristics.

[0030] Furthermore, the LED can comprise at least one lower extension connected to the first electrode field. Moreover, the at least one lower extension can be arranged between the at least two light-emitting areas. [Beneficial effects]

[0031] In a conventional LED, the second electrode array is located on the semiconductor layer of the second conductivity type and is electrically connected to it. Consequently, current accumulates around the second electrode array, thus interrupting current propagation. However, since the second electrode array is isolated from the light-emitting assembly by the reflective insulating layer, it is possible, according to embodiments of the present invention, to prevent current accumulation near the electrode array. Furthermore, the second electrode array is formed in a region where the semiconductor layer of the second conductivity type and the active layer have been removed by mesa etching in the light-emitting assembly. This prevents light from being unnecessarily generated under the second electrode array, thereby improving the light emission efficiency.Additionally, the light-emitting array is divided into a multitude of light-emitting regions, thus preventing excessive current accumulation at crystal defects in these regions and ensuring a uniform current distribution. Furthermore, the light extraction element structure is arranged on the light-emitting array to further improve light extraction efficiency. [Description of the drawings] Fig. 1 is a top view illustrating an LED according to one embodiment of the present invention; Fig. 2a to 2c are sectional drawings along lines AA, BB and CC respectively. Fig. 1; Fig. 3 is a sectional drawing of an LED according to a further embodiment of the present invention, which is the sectional drawing of Fig. 2c along line CC from Fig. 1 corresponds to; Fig. 4 is a top view illustrating an LED according to a further embodiment of the present invention; and Fig. Figure 5 is a top view showing an LED according to a further embodiment of the present invention. [Best Design]

[0032] Preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments are provided for illustrative purposes only, so that a person skilled in the art can fully understand the essence of the present invention. Therefore, the present invention is not limited to the following embodiments, but can also be implemented in other ways. In the drawings, widths, lengths, thicknesses, and the like may be exaggerated for the sake of clarity. Throughout the description and the drawings, the same reference numerals denote the same elements.

[0033] Fig. Figure 1 is a top view illustrating an LED according to an embodiment of the present invention and the Fig. 2a to 2c are sectional drawings along lines AA, BB and CC respectively. Fig. 1.

[0034] Referring to the Fig. In Figures 1 and 2a to 2c, the LED comprises a substrate 21, a light-emitting arrangement with light-emitting regions LE1 and LE2, a reflective insulating layer 31, a first electrode field 35, a second electrode field 33, and upper extensions 33a. The LED may further comprise a transparent electrode layer 29, an insulating layer 32, connections 33b, a first lower extension 35a, and a second lower extension 35b. The light-emitting arrangement comprises a semiconductor layer of first conductivity type 23, an active layer 25, and a semiconductor layer of second conductivity type 27.

[0035] The substrate 21 can be a structured sapphire substrate, but the present invention is not limited to this. The semiconductor layer of the first conductivity type 23 is arranged on the substrate 21, and the semiconductor layer of the second conductivity type 27 is arranged above the semiconductor layer of the first conductivity type 23. The active layer 25 is arranged between the semiconductor layers of the first and second conductivity types.

[0036] The semiconductor layer of the first conductivity type 23, the active layer 25, and the semiconductor layer of the second conductivity type 27 can be formed from a KGaN-based semiconductor compound material, i.e., (Al, In, Ga)N. The elements in the composition of the active layer 25 and their ratios are determined such that light of a desired wavelength, for example, ultraviolet or blue light, is emitted.

[0037] The semiconductor layer of the first conductivity type 23 can be an n-type nitride semiconductor layer and the semiconductor layer of the second conductivity type 27 can be a p-type nitride semiconductor layer or vice versa.

[0038] The semiconductor layer of the first conductivity type 23 and / or the semiconductor layer of the second conductivity type 27 can be configured as a single-layer structure, as shown in the figures, or as a multi-layer structure. The active layer 25 can have a single quantum well structure or a multiple quantum well structure. The buffer layer (not shown) can be positioned between the substrate 21 and the semiconductor layer of the first conductivity type 23. The semiconductor layers 23, 25, and 27 can be fabricated using metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

[0039] In the light-emitting arrangement, the semiconductor layer of the second conductivity type 27 and the active layer 25 can be subdivided such that at least two light-emitting regions LE1 and LE2 are defined. The light-emitting regions LE1 and LE2 can be formed to have a symmetrical structure, and such a subdivision can be carried out by a mesa etching process. The semiconductor layer of the first conductivity type 23 is exposed by the mesa etching process in the region traversing the center of the light-emitting arrangement such that the semiconductor layer of the second conductivity type 27 and the active layer 25 can be subdivided into two regions. Each of the side faces of the light-emitting arrangement formed by the mesa etching process can have an angle of inclination in the range of 30 to 70 degrees with respect to a surface of the substrate 21.

[0040] Meanwhile, the transparent electrode layer 29 can be arranged on the semiconductor layer of the second conductivity type 27. The transparent electrode layer 29 can be made of indium tin oxide (ITO) or Ni / Au and is in ohmic contact with the semiconductor layer of the second conductivity type. Light extraction element (LEE) structures are arranged on the transparent electrode layer 29. The LEE structures can, for example, be cylindrical with a diameter of approximately 5 µm and spaced approximately 30 µm apart. As the light generated in the active layer 25 propagates towards the transparent electrode layer 29, the LEE structures can promote the emission of the light by scattering or reflecting it. Although the LEE structures can be regular, the present invention is not limited to this.This means that the structures of the light extraction elements can be irregular.

[0041] The reflective insulating layer 31 is arranged on the semiconductor layer of the first conductivity type 23, which was exposed by the mesa etching process. The reflective insulating layer 31 is arranged on a portion of the light-emitting arrangement and covers part of the mesa facets exposed by the mesa etching. The reflective insulating layer 31 can be formed by alternately stacking material layers with different refractive indices and subsequently structuring them using photolithography and an etching process. The layers with different refractive indices can be selected, for example, from SiO2, Si3N4, TiO2, and Nb2O5.

[0042] The reflective insulating layer 31 can be formed on the light-emitting arrangement after the formation of the transparent electrode layer 29. However, the present invention is not limited to this. For example, the reflective insulating layer 31 can be formed first, and then the transparent electrode layer 29 can be formed.

[0043] The insulating layer 32 can cover the semiconductor layer of the second conductivity type 27 (or the transparent electrode layer 29) of the light-emitting arrangement. The insulating layer 32 can also cover the side faces of the semiconductor layer of the second conductivity type 27 and the active layer 25 that have been exposed by the mesa etching process. Furthermore, the insulating layer 32 has openings 32a for exposing the transparent electrode layer 29 on the corresponding light-emitting regions LE1 and LE2. The transparent electrode layer 29 (or the semiconductor layer of the second conductivity type 27) is exposed through the openings 32a. There are no particular restrictions for the insulating layer 32 as long as it is made of a transparent material through which the light generated in the active layer 25 can pass. The insulating layer can, for example, be made of SiO2.

[0044] The first electrode array 35 and the second electrode array 33 are arranged on the semiconductor layer of the first conductivity type exposed by the mesa etching process. The first electrode array 35 is electrically connected to the semiconductor layer of the first conductivity type 23. The second electrode array 33, however, is insulated from the semiconductor layer of the first conductivity type 23 by the insulating layer 31. The first and second electrode arrays 35 and 33 are contact fields to which wires are connected and have a relatively large contact area. Although the first and second electrode arrays 35 and 33 can be arranged only on the exposed area of ​​the semiconductor layer of the first conductivity type 23, the present invention is not limited to this. That is to say, the first and second electrode arrays can be arranged partially on the semiconductor layer of the second conductivity type 27.

[0045] The reflective insulating layer 31 is arranged between the second electrode field 33 and the semiconductor layer of the first conductivity type 23 to insulate the second electrode field 33 from the semiconductor layer of the first conductivity type 23. Furthermore, the reflective insulating layer 31 covers part of the mesa side faces to prevent the second electrode field 33 from coming into contact with the semiconductor layer of the second conductivity type 27 or the active layer 25.

[0046] The upper extensions 33a are arranged on the semiconductor layer of the second conductivity type 27 (or the transparent electrode layer 29). The upper extensions 33a can be connected to the second electrode field 33 by the corresponding connecting parts 33b. The upper extensions 33a are electrically connected to the semiconductor layer of the second conductivity type 27 (or the transparent electrode layer 29). The upper extensions 33a can be connected to the transparent electrode layer 29 by the corresponding openings 32a in the insulating layer 32. The upper extensions 33a are arranged such that they allow a uniform distribution of the current in the semiconductor layer of the first conductivity type 23. The connecting parts 33b are spaced apart from the semiconductor layer of the second conductivity type 27 and the active layer 25 by the reflective insulating layer 31 and / or the insulating layer 32.

[0047] Furthermore, at least one lower extension 35a can extend from the first electrode field 35. The lower extension 35a is arranged on the semiconductor layer of the first conductivity type 23 and electrically connected to the semiconductor layer of the first conductivity type 23. Although the lower extension 35a can be arranged between the subdivided light-emitting regions, the present invention is not limited to this. That is, the lower extension can be arranged outside the light-emitting regions, such as the lower extension 35b.

[0048] The electrode fields 33 and 35, the upper extensions 33a, the connecting parts 33b, and the lower extensions 35a and 35b can be formed together on the same metallic material, for example Cr / Au, using the same method. However, the present invention is not limited to this. The upper extensions 33a and the electrode field 33 can, for example, be formed using separate methods and from different materials.

[0049] In the present embodiment, the subdivided light-emitting regions are symmetrical with respect to a line connecting the first electrode field 35 with the second electrode field 33, for example BB. The upper extensions 33a are also arranged symmetrically, so that the light-emitting regions have the same light-emitting properties. Compared to two conventional LEDs, which are normally connected in parallel, the LED according to the invention, which has two subdivided light-emitting regions, can be used to simplify the assembly process of an LED. Moreover, the subdivided light-emitting regions prevent the accumulation of current due to a defect. In addition, the inclined sides are formed by the mesa etching process, so that the light extraction efficiency can be increased.

[0050] In the present embodiment, the second electrode array 33 is arranged on the semiconductor layer of the first conductivity type 23, which has been exposed by mesa etching, and the reflective insulating layer 31 is arranged between them. Such a configuration prevents light from being generated under the electrode array 33 and allows light to be generated in an area extending to the area where the second electrode array 33 is formed, thereby utilizing the current effectively. However, the present invention is not limited to this. For example, the substrate can be exposed by further removing the areas of the semiconductor layer of the first conductivity type 23 exposed by the mesa etching process. The reflective insulating layer 31 can be formed on the substrate 21, and the second electrode array 33 can be arranged on the reflective insulating layer.Alternatively, the second electrode field 33 can be arranged on the reflective insulating layer 31 such that it is located between the second electrode field 33 and the semiconductor layer of the second conductivity type 27 or the transparent electrode layer 27.

[0051] Fig. 3 is a sectional drawing illustrating an LED according to a further embodiment of the present invention, and which is the sectional drawing of Fig. 2c along line CC from Fig. 1 corresponds to.

[0052] Referring to Fig. 3. The LED according to the present embodiment is almost identical to the previously described LED, and therefore only the differences are described to avoid overlap.

[0053] In the case of the previously mentioned reference to the Fig. In the LED described in Figures 1 and 2a to 2c, the light extraction element (LEE) structure is arranged on the transparent electrode layer 29. In contrast, in the LED according to the present embodiment, the LEE structure is arranged on the insulating layer 32. The LEE light extraction elements can be formed by partially structuring an upper part of the insulating layer 32, or they can be formed by forming another material layer on the insulating layer 32 and subsequently structuring this material layer. The LEE light extraction elements can, for example, be cylindrical with a diameter of 5 µm and spaced apart from each other by approximately 30 µm.

[0054] Fig. Figure 4 is a top view illustrating an LED according to a further embodiment of the present invention.

[0055] In the embodiment of Fig. In the first and second electrode fields 35 and 33 are arranged along a main axis of the LED, and the light-emitting areas are subdivided along this main axis. In the present embodiment, however, the electrode fields 53 and 55 are arranged along a secondary axis of the LED, and the light-emitting areas are subdivided along this secondary axis. The subdivided light-emitting areas have a symmetrical structure, and the upper and lower extensions 53a and 55a are also arranged symmetrically to each other.

[0056] A reflective insulating layer 51 is arranged below the second electrode field 53, as described in reference to Fig. 1 is described, and a structure of light extraction elements LEE is arranged on a transparent electrode layer or the insulating layer 52.

[0057] In the present case, the upper extensions 53a are arranged such that they extend along an outer edge of the LED and surround it. Furthermore, each upper extension has a projection 53c that extends from the outer edge of the LED into its interior. Meanwhile, the lower extensions 55a extend from the interior of the LED outwards. Each of the lower extensions 55a can be subdivided into two branches that surround the projections 53c in each light-emitting region.

[0058] The upper extensions 55a are connected to the second electrode field 53 via connecting parts 53b.

[0059] Fig. Figure 5 is a top view showing an LED according to a further embodiment of the present invention.

[0060] Referring to Fig. 5. The LED according to the present embodiment is almost identical to the one referred to in reference to Fig.4 LEDs described. However, they differ in the arrangement of the upper and lower extensions 65a and 63a.

[0061] That is, the lower extensions 65a extend first along an outer edge of the LED and then into the interior of the light-emitting areas. Each of the upper extensions 63a has two extensions in each light-emitting area, the two extensions being arranged such that they surround the lower extension 65a, which extends into the interior of the light-emitting area.

Claims

[1] Light-emitting diode (LED) comprising: a substrate (21); a light-emitting arrangement arranged on the substrate (21), wherein the light-emitting arrangement comprises a semiconductor layer of the first conductivity type (23), an active layer (25) and a semiconductor layer of the second conductivity type (27); a first electrode field (35) electrically connected to the semiconductor layer of the first conductivity type (23), a second electrode field (33) arranged above the substrate (21); at least one upper extension (33a) connected to the second electrode field (33) in such a way that it is electrically connected to the semiconductor layer of the second conductivity type (27); and a structure of light extraction elements (LEE) arranged on the semiconductor layer of the second conductivity type (27); characterized by a reflective insulating layer (31) that covers part of the light-emitting structure and is arranged under the second electrode field (33) such that the second electrode field (33) is spaced apart from the light-emitting arrangement; wherein the semiconductor layer of the first conductivity type (23) has an exposed area by mesa etching of the semiconductor layer of the second conductivity type (27) and the active layer (25), the second electrode field (33) is arranged on the exposed area of ​​the semiconductor layer of the first conductivity type (23), and the reflective insulating layer (31) is arranged between the second electrode field (33) and the semiconductor layer of the first conductivity type (23). [2] LED according to claim 1, wherein the semiconductor layer of the first conductivity type (23) is an n-type nitride semiconductor layer and the semiconductor layer of the second conductivity type (27) is a p-type nitride semiconductor layer. [3] LED according to claim 2, further comprising a transparent electrode layer (29) arranged on the n-type nitride semiconductor layer, wherein the upper extension (33a) is connected to the transparent electrode layer (29). [4] LED according to claim 3, wherein the structure is formed from light extraction elements (LEE) on the transparent electrode layer (29). [5] LED according to claim 3, which further comprises an insulating layer (32) covering the transparent electrode layer (29), wherein the insulating layer (32) has openings for exposing the transparent electrode layer (29) and the upper extension (33a) is connected to the transparent electrode layer (29) through the opening. [6] LED according to claim 5, wherein the opening is arranged such that it is spaced apart from the second electrode field (33). [7] LED according to claim 5, wherein the structure is formed from light extraction elements (LEE) on the insulating layer (32). [8] LED according to claim 1, wherein the reflective insulating layer (31) covers at least a part of the side surfaces of the semiconductor layer of the second conductivity type (27) and the active layer (25) exposed by mesa etching. [9] LED according to claim 1, further comprising a connecting part (33b) for connecting the upper extension (33a) to the second electrode field (33), wherein the connecting part (33b) is spaced apart from the semiconductor layer of the second conductivity type (27) by the insulating layer (32). [10] LED according to claim 1, the semiconductor layer of the second conductivity type (27) and the active layer (25) are divided to define at least two light-emitting regions (LE1, LE2), and the upper extensions (33a) connected to the second electrode field (33) are arranged accordingly on the at least two light-emitting regions (LE1, LE2). [11] LED according to claim 10, wherein the at least two light-emitting areas (LE1, LE2) are symmetrical to each other with respect to a straight line traversing the first and second electrode fields (33, 35). [12] LED according to claim 10, further comprising at least one lower extension (35a) connected to the first electrode field (35), wherein the at least one lower extension (35a) is arranged between the at least two light-emitting areas (LE1, LE2). [13] LED according to claim 10, further comprising transparent electrode layers (29) arranged accordingly on the semiconductor layers of the second conductivity type (27) in the light-emitting regions (LE1, LE2), wherein the upper extensions (33a) connected to the second electrode field (33) are connected to the corresponding transparent electrode layers (29). [14] LED according to claim 13, wherein the structure is formed from light extraction elements (LEE) on the transparent electrode layers (29). [15] LED according to claim 13, further comprising an insulating layer (32) covering the transparent electrode layers (29), wherein the insulating layer (32) has openings for exposing the transparent electrode layers (29) and the upper extensions (33a) are connected to the transparent electrode layers (29) through the openings accordingly. [16] LED according to claim 15, wherein the structure is formed from light extraction elements (LEE) on the insulating layer (32).

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