KR100907524B1 - Light emitting diode device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an electrode structure for forming a uniform current distribution in a light emitting diode device and a method of forming the same. A light emitting diode device according to the present invention includes a first semiconductor layer formed on a substrate; A second semiconductor layer formed over a portion of the first semiconductor layer and having a conductive type opposite to the first semiconductor layer; A second electrode formed on the second semiconductor layer; And a first electrode formed on the first semiconductor layer, wherein the first electrode is formed in a region where the second semiconductor layer is not formed and includes a portion extending in a band shape; And a conductive pad connected to the first transparent electrode. By this structure, the current flowing to the p-n junction surface can be suppressed locally, and the light efficiency loss caused by the auxiliary electrode can be minimized, thereby maximizing the light emitting efficiency of the light emitting diode.

Light Emitting Diode, Transparent Electrode, Auxiliary Electrode, Current Distribution

Description

LIGHT EMITTING DIODE DEVICE AND MANUFACTURING METHOD THEREOF

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode device and a method of manufacturing the same, and more particularly, to an electrode structure for forming a uniform current distribution in a light emitting diode device and a method of forming the same.

BACKGROUND ART In general, a light emitting diode used as a device for emitting light is spotlighted as a next-generation lighting that replaces an incandescent lamp or a fluorescent lamp. In particular, as a blue light emitting diode using gallium nitride (GaN) has been developed, it is possible to realize all colors, and accordingly, demand in various fields is increasing. Light-emitting diodes are considered as next-generation national strategic items because they have the advantages of fast processing speed and low power consumption of semiconductors and environmentally friendly and high energy saving effect.

The general structure of such a light emitting diode is as follows.

1 is a perspective view schematically illustrating a structure of a general light emitting diode, and FIG. 2 is a plan view schematically illustrating a structure of a general light emitting diode. As shown in FIG. 1, the first semiconductor layer 11 is formed on the prepared substrate 10. The p-n junction surface 20 may be formed on the first semiconductor layer 11 by forming a second semiconductor layer 12 having a polarity opposite to that of the first semiconductor layer 11. That is, when the first semiconductor layer 11 is doped with p-type, the second semiconductor layer 12 doped with n-type is formed on the first semiconductor layer 11, and the first semiconductor layer 11 is n-type. When doped, the second semiconductor layer 12 doped in a p-type may be formed on the first semiconductor layer 11. The second metal electrode 14 is formed on the surface in contact with the second semiconductor layer 12 to flow a current through the p-n junction surface 20 thus formed. In this case, the current distribution transparent electrode 13 may be formed between the upper surface of the second semiconductor layer 12 and the second metal electrode 14 so that the current flows uniformly to the p-n junction surface 20. Further, in order to form the first metal electrode 15, etching is performed from the second semiconductor layer 12 at the top of the device structure to a part of the first semiconductor layer 11 using a dry etching method. After etching, a pattern is formed using a photolithography process, and the first metal electrode 15 is formed using an electron beam deposition method or the like. A pad (not shown) is then formed for wire contact with an external power source. When current flows through the second metal electrode 14 and the first metal electrode 15 of the light emitting diode manufactured as described above, light is emitted from the p-n junction surface.

In the light emitting diode of this structure, the first metal electrode 15 is located at one end of the light emitting diode element, as shown in FIG. As described above, in order to form the first metal electrode 15, the semiconductor layer having a light emitting function needs to be etched. Thus, for the efficiency of the device, an etched semiconductor layer, that is, the first metal electrode 15 is formed. The smaller area is advantageous. In addition, in order to maximize the effective area of the light emitting area, it is advantageous to reduce the circumference as much as possible, so that the position of the first metal electrode 15 is generally formed at the end of the element.

However, when the area of the first metal electrode 15 is small and located in one direction of the device, problems such as concentration of current occur as described later.

3 is an equivalent circuit diagram of the light emitting diode shown in FIG. 1.

As shown in FIG. 3, a path of a current that may flow from the second metal electrode 14 to the first metal electrode 15 may vary depending on the position of the lower first metal electrode 15.

Here, the shortest path is referred to as a first path (path 1) for convenience, and the path farthest from the first metal electrode 15 will be referred to as a second path (path 2). That is, in the first path Path 1, current flows to the vicinity of the first electrode 15 through the transparent electrode 13 under the second electrode 14, and near the first electrode 15. After the current flows through the pn junction surface of the light emitting diode, the path reaches the first electrode 15. In addition, the second path Path 2 has a current flowing along the first semiconductor layer 11 after a current flows through the pn junction surface 20 at a distance away from the first electrode 15. It is a path to reach (15).

Since the resistance of the first semiconductor layer 11 is greater than that of the transparent electrode 13, which is a conductive material, current does not easily flow through the first semiconductor layer 11. That is, a current tends to flow in the first path Path 1 more than the second path Path 2. According to this analysis, the amount of current flowing to the p-n junction surface 20 near the first electrode 15 rather than far from the first electrode 15 is greater.

When such a concentration of current occurs, the luminous efficiency is remarkably degraded in a region where current is not easily transmitted, that is, a region far from the first electrode 15. In other words, the intensity of light emission by electron-hole coupling is shorter and the wavelength is shorter in the region where the electron-hole concentration is relatively high, while the intensity of light emission by such bonding is higher in the region where electron-hole concentration is relatively low. It is relatively small and the wavelength becomes longer. In addition, in this case, light having a short wavelength is partially absorbed into a light region having a relatively long wavelength, thereby lowering the internal quantum efficiency in light emission of the device.

In order to solve the concentration phenomenon of the current, various first electrode structures may be considered.

4 is a plan view schematically illustrating a structure of a light emitting diode having various types of first electrodes. The same reference numerals are used for the same components as in FIGS. 1 and 2.

Reference numeral (a) is a light emitting diode having the same structure as shown in Figs. 1 and 2, in which only the metal pad 15a is used for the first electrode. The structure of the first electrode shown in reference numeral (b) has a band-shaped metal auxiliary electrode 15b extending beyond the metal pad 15a toward the second electrode 14. The structure of the first electrode shown in (c) is a form in which a band-shaped metal auxiliary electrode 15c extends along the side edge of the light emitting diode, and the structure of the first electrode shown in (d) is The strip-shaped metal auxiliary electrode 15d has a closed loop shape surrounding the side edge of the light emitting diode.

The structures of the first electrode of the type introduced in the reference numerals (b) to (d) are for solving the problem of current concentration as described above, and by making the path from the first electrode to the second electrode as uniform as possible To distribute the flow of

However, when such a structure is introduced, the effective light emitting area is reduced, and light is blocked due to the auxiliary electrode of the metal component, thereby reducing the light output.

FIG. 5 is a graph showing experimental results of driving voltage and light output with respect to the electrode area of the light emitting diode shown in FIG. 4.

The horizontal axis of the graph represents the area (μm ² ) of the first electrode 15, the left axis of the vertical axis represents the voltage (V) required for driving each light emitting diode, and the right vertical axis represents the light from each light emitting diode. Indicates output mW. Areas and measured values for each of the light emitting diodes shown in FIG. 4 are plotted on the graph as points of square (light output) and diamond (drive voltage) using the same reference numerals as in FIG. 4.

As can be seen from the graph, as the area of the first electrode increases due to the use of the metal auxiliary electrode, the driving voltage required for light emission is lowered, but the light output from the light emitting diode is also lowered.

This phenomenon is caused by the decrease of the area of the LED layer relatively as the area of the first electrode increases, but the actual measurement is more than the loss due to the decrease of the area of the LED layer. It shows a big decrease in light output. This is because part of the light emitted by the auxiliary electrode formed of the metal is absorbed.

FIG. 6 is a view for explaining light output reduction in the light emitting diode shown in FIG. 4. The top view (left side) of the light emitting diode of FIG. 4 (c) and the cross section (right side) cut along the AA 'straight line are shown.

Light emitted from the pn junction surface or the active layer 13 of the light emitting diode is emitted through the second semiconductor layer 12 and the transparent electrode 13 thereon, the main part of the light emitting diode, but the side of the semiconductor layer In some embodiments, the light may be emitted through the light emitting device, and some may be reflected by the lower substrate as indicated by the arrow 30. In this case, as shown in FIG. 6, when the metal auxiliary electrode 15c of the first electrode is in the path of emitted light, the emission of the light is blocked or absorbed.

The present invention is to solve the above problems, an object of the present invention is to provide a light emitting diode device having an electrode structure for inducing a uniform current distribution to implement a large area light emitting diode of high power, high brightness.

In order to achieve the above technical problem, a light emitting diode device according to an embodiment of the present invention includes a substrate; A first semiconductor layer formed on the substrate; A second semiconductor layer formed over a portion of the first semiconductor layer and having a conductive type opposite to the first semiconductor layer; A second electrode formed on the second semiconductor layer; And a first electrode formed on the first semiconductor layer, wherein the first electrode is formed in a region where the second semiconductor layer is not formed and includes a portion extending in a band shape; And a conductive pad connected to the first transparent electrode.

The conductive pad of the first electrode may be positioned in an edge region of the first semiconductor layer, and the first transparent electrode may include a portion formed in a band shape along all or part of an edge of the first semiconductor layer. A metal thin film layer may be formed between the first semiconductor layer and the first transparent electrode. In this case, the metal thin film layer may be formed to a thickness that can transmit light generated by the light emitting diode device. The conductive pad of the first electrode may be formed of a semicircular metal layer.

According to another aspect of the present invention, there is provided a method of manufacturing a light emitting diode device, including: forming a first semiconductor layer on a prepared substrate; Forming a second semiconductor layer of a conductive type opposite to the first semiconductor layer on the first semiconductor layer; Selectively etching a portion of the second semiconductor layer to expose a portion of the first semiconductor layer; Forming a second electrode on the second semiconductor layer; Forming a first transparent electrode on the exposed region of the first semiconductor layer, the first transparent electrode including a portion patterned in a band shape; And forming a conductive pad connected to the first transparent electrode.

The forming of the first transparent electrode may include forming a first transparent electrode layer; And patterning the first transparent electrode layer to have a band shape along an edge of the first semiconductor layer, and further comprising forming a metal thin film layer before forming the first transparent electrode layer. The metal thin film layer may be patterned in the same form as the first transparent electrode layer.

According to an exemplary embodiment of the present invention, the light emitting efficiency of the light emitting diode may be maximized by providing an electrode structure which minimizes local current flow to the p-n junction and minimizes light efficiency loss caused by the auxiliary electrode.

In addition, the process cost and time can be reduced by performing the process of forming the auxiliary electrode and the metal pad of the lower electrode simultaneously with the process of forming the transparent electrode and the metal electrode of the upper electrode.

Hereinafter, a method of manufacturing a light emitting diode according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

An embodiment of the present invention is characterized in that the auxiliary electrode is formed as a transparent electrode in order to prevent or reduce the light blocking effect by the auxiliary electrode as described above. That is, in the first electrode formed on the first semiconductor layer, the auxiliary electrode portions other than the metal pads use an electrode that is "substantially transparent". Here, the term "substantially transparent" means that there is a property of transmitting light generated from the diode, and does not necessarily mean that there is a transmittance of 100%. That is, the effect is remarkable even when there is a light transmittance of about 50% to 90% as in the ITO material which is generally used for the transparent electrode positioned on the second semiconductor layer.

7 is a plan view schematically illustrating a structure of a light emitting diode according to an embodiment of the present invention, and FIG. 8 is a cross-sectional view illustrating a state in which the light emitting diode illustrated in FIG. 7 is cut along a line BB ′.

There is a substrate 100 formed of sapphire, silicon carbide or the like below, the first semiconductor layer 110 formed on the substrate 100 is formed. The second semiconductor layer 120 is formed on the first semiconductor layer 110, and has a conductivity-type opposite to that of the first semiconductor layer to form the p-n junction surface 200. That is, when the first semiconductor layer 110 is doped with p-type, the second semiconductor layer 120 doped with n-type is formed on the first semiconductor layer 110, and conversely, the first semiconductor layer 110 is n-formed. If doped with a die, a second semiconductor layer 120 doped with a p-type may be formed on the first semiconductor layer 110. In addition, a substantially undoped semiconductor layer (not shown) may be inserted between the first semiconductor layer 110 and the second semiconductor layer 120 to act as an active layer for emitting light. As the semiconductor layer of the light emitting diode, a material capable of emitting light by recombination of electrons and holes is used. Particularly, a compound semiconductor of Group III-nitride series (for example, gallium nitride, etc.) performs direct type recombination. Suitable as semiconductor layer material of light emitting diode.

In order to form an electrode for current injection for light emission in the semiconductor layer, a first electrode 150 for the first semiconductor layer 110 and second electrodes 130 and 140 on the second semiconductor layer 120 are formed. Is formed.

In order to form the first electrode 150 connected to the first semiconductor layer 110, the second semiconductor layer 120 and an active layer (not shown) below are selectively etched to form a first semiconductor layer ( Expose some areas of 110). The first electrode 150 is formed in a portion of the exposed first semiconductor layer 110. The first electrode includes a conductive pad 151 and a thin strip-shaped transparent electrode 152 connected to the conductive pad 151.

The conductive pad 151 has a shape close to a semicircle as shown in FIG. 7 in terms of ease of processing and device efficiency, but is not limited thereto. In addition, the position of the conductive pad may also be generally located at the center of one side of the device, but is not limited thereto.

The transparent electrode 152 preferably has a thin stripe shape in order to minimize the loss of the effective area of the light emitting diode, and as shown in FIG. 7, the transparent electrode 152 may be formed to surround the edge of the light emitting diode. And light emission efficiency. However, the shape of the transparent electrode 152 to function as an auxiliary electrode is not limited to this, it will be apparent to those skilled in the art that the shape and similar variations as shown in Figure 4 (b) or (d) is possible.

In the first electrode, since the conductive pad 151 is directly supplied with power or serves to transfer current to the outside, a metal-based conductor having low resistance and stable conductivity is mainly used, and the transparent electrode 152 A transparent conductive oxide such as ITO having good light transmittance may be used.

In addition, in the case of using a conductive oxide such as ITO, it is generally difficult to form an ohmic junction with a lower semiconductor layer (particularly, a group III nitride compound semiconductor layer). Thus, the transparent conductive oxide 152a and the first semiconductor layer The metal thin film layer 152b may be inserted between the 110. The metal thin film layer 152b is preferably formed in a thin film form as much as possible to achieve the purpose of forming an ohmic junction between the transparent conductive oxide 152a and the first semiconductor layer 110. To this end, the metal thin film layer 152b may be formed of a metal such as Cr, Al, Ti, W, Hf, etc., and the thickness thereof is 1 kPa to 100 kPa, so that the light transmittance may be maintained while making ohmic bonding.

The second electrode layer may include a second transparent electrode layer 130 covering the entire surface of the second semiconductor layer and a metal electrode 140 serving as a power supply pad for current distribution.

9A to 9D are cross-sectional views showing exemplary steps in the method according to an embodiment of the present invention for manufacturing the light emitting diode shown in FIG. Here, the cross section which cut | disconnected the light emitting diode shown in FIG. 7 with respect to straight line CC 'is shown.

First, as shown in FIG. 9A, the first semiconductor layer 110, the second semiconductor layer 120, and the like are formed on the prepared substrate 100, and a portion of the second semiconductor layer 120 is selectively etched. Thus, a partial region of the first semiconductor layer 110 is exposed. The pattern of the region of the first semiconductor layer 110 exposed by the selective etching is determined in consideration of the formation pattern of the conductive pad and the auxiliary electrode thereof as illustrated in FIG. 7.

After a portion of the first semiconductor layer 110 is exposed, as shown in FIG. 9B, a metal thin film layer 152b for ohmic bonding is formed on the exposed first semiconductor layer 110, and ohmic Heat treatment is required to form the junction. In this step, a metal thin film layer (not shown) is also formed on the second semiconductor layer 120 at the same time, and may be used to form an ohmic junction. Here, the heat treatment conditions for forming the ohmic junction are similar to the conditions applied for the ohmic junction between the second semiconductor layer and the transparent electrode on the light emitting diode having the general structure, and thus the detailed description thereof will be omitted. .

Thereafter, as shown in FIG. 9C, a transparent conductive oxide layer 152a such as ITO is formed on the metal thin film layer 152b. In this case, heat treatment may be performed to form an ohmic junction with the lower metal thin film layer 152b. The metal thin film layer 152b thus formed and the conductive oxide layer 152a thereon function as a transparent auxiliary electrode, and thus are patterned into a band shape formed along the edge of the light emitting diode. In this case, the second transparent electrode 130 made of the same material may be formed and patterned on the second semiconductor layer 120 at the same time. Since the second transparent electrode 130 is formed for the purpose of maximizing the efficiency of the current distribution, the second transparent electrode 130 is formed to cover the upper surface of the second semiconductor layer as much as possible.

After the formation of the transparent electrodes 152a and 130 is completed, a metal-based conductive pad 151 connected to the first transparent electrode 150 is formed, and the metal of the second electrode is formed on the second transparent electrode 130. The electrode 140 is formed. The conductive pad 151 and the metal electrode 140 of the second electrode may be formed of the same material, and may be formed through one photolithography process using the same mask.

In the above, the present invention has been described with reference to the presently considered embodiments, but the present invention should not be understood as being limited to the above embodiments. Rather, it should be construed as including all modifications of the range which are easily changed by those skilled in the art from the above-described embodiment of the present invention and considered equivalent.

1 is a cross-sectional view schematically showing the structure of a general light emitting diode.

2 is a plan view schematically illustrating a structure of a general light emitting diode.

3 is an equivalent circuit diagram of the light emitting diode shown in FIG. 1.

4 is a plan view schematically illustrating a structure of a light emitting diode having various types of first electrodes.

FIG. 5 is a graph showing the driving voltage and the light output with respect to the electrode area of the light emitting diode shown in FIG. 4.

FIG. 6 is a view for explaining light output reduction in the light emitting diode shown in FIG. 4.

7 is a plan view schematically showing the structure of a light emitting diode according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating the light emitting diode of FIG. 7 taken along a line BB ′. FIG.

9A to 9D are front and plan views illustrating exemplary steps in the method of manufacturing the light emitting diode shown in FIG. 7.

Claims (15)

In the light emitting diode device, Board; A first semiconductor layer formed on the substrate; A second semiconductor layer formed over a portion of the first semiconductor layer and having a conductive type opposite to the first semiconductor layer; A second electrode formed on the second semiconductor layer; And A first electrode formed on the first semiconductor layer in a region where the second semiconductor layer is not formed; The first electrode is A first transparent electrode formed on the first semiconductor layer and including a portion extending in a band shape; And And a conductive pad formed on the first semiconductor layer and connected to the first transparent electrode. The method of claim 1, The conductive pad of the first electrode is located at an edge region of the first semiconductor layer, The portion extending in the band shape of the first transparent electrode is formed along all or part of the edge of the first semiconductor layer. The method of claim 1, The conductive pad of the first electrode is located at an edge region of the first semiconductor layer, A band extending portion of the first transparent electrode is formed on the central region of the first semiconductor layer. The method according to any one of claims 1 to 3, The first electrode further includes a metal thin film layer between the first semiconductor layer and the first transparent electrode, The metal thin film layer is a light emitting diode device, characterized in that formed to a thickness that can transmit the light generated by the light emitting diode device. The method of claim 4, wherein The metal thin film layer is formed of a material selected from the group consisting of Cr, Al, Ti, W, Hf, The metal thin film layer has a thickness of 1 kHz to 100 kHz. The method of claim 1, The second transparent electrode layer is formed on the second semiconductor layer, the light emitting diode device, characterized in that the second electrode is formed on a portion of the second transparent electrode layer. In the manufacturing method of a light emitting diode element, Forming a first semiconductor layer on the prepared substrate; Forming a second semiconductor layer of a conductive type opposite to the first semiconductor layer on the first semiconductor layer; Selectively etching a portion of the second semiconductor layer to expose a portion of the first semiconductor layer; Forming a first transparent electrode on the exposed region of the first semiconductor layer, the first transparent electrode including a portion patterned in a band shape; Forming a second electrode on the second semiconductor layer; And Forming a conductive pad on the exposed region of the first semiconductor layer, the conductive pad being connected to the first transparent electrode. The method of claim 7, wherein Forming the first transparent electrode, Forming a first transparent electrode layer; And And patterning the first transparent electrode layer to include a portion extending in a band shape along an edge of the first semiconductor layer. The method of claim 8, Forming the first transparent electrode, Forming a metal thin film layer prior to forming the first transparent electrode layer; The metal thin film layer is patterned in the same form as the first transparent electrode layer. The method of claim 9, The metal thin film layer is formed to a thickness that can transmit the light generated by the light emitting diode device. The method of claim 10, The metal thin film layer is formed of a material selected from the group consisting of Cr, Al, Ti, W, Hf, The metal thin film layer has a thickness of 1 kPa to 100 kPa. The method according to claim 7 or 8, Forming the conductive pad, Forming a metal layer over the patterned first transparent electrode layer; And Patterning the metal layer. The method of claim 7, wherein Forming the second electrode, Forming a second transparent electrode layer on the second semiconductor layer; And Forming a metal electrode on a portion of the second transparent electrode layer. The method of claim 13, The forming of the second transparent electrode layer is performed at the same time as the forming of the first transparent electrode layer. The method of claim 13, The forming of the metal electrode may be performed at the same time as forming the conductive pad connected to the first transparent electrode layer.

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