KR101106135B1 - A light emitting diode having uniform current density - Google Patents

Abstract

A lower semiconductor layer formed on the substrate; An upper semiconductor layer disposed on the lower semiconductor layer to expose at least a portion of edge regions of the lower semiconductor layer; A lower electrode formed adjacent to a first side on the exposed lower semiconductor layer; An upper electrode formed on the upper semiconductor layer adjacent to the second side opposite to the first side; A first lower extension part extending from the lower electrode on the exposed lower semiconductor layer adjacent to the first side and a second lower part extending from the lower electrode and adjacent to the third side adjacent to the first side; An extension; And a first upper extension extending from the upper electrode on the upper semiconductor layer and formed adjacent to the second side, and a second upper extension extending from the upper electrode and adjacent to the fourth side adjacent to the second side. A light emitting diode having a uniform current density characteristic including a portion is provided.

Current Density, Light Emitting Diode, LED, Extension, Upper Electrode, Symmetry, Large Area

Description

A light emitting diode having uniform current density

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode having a uniform current density characteristic having an electrode structure capable of inducing a uniform current distribution and high power and high brightness.

Gallium nitride (GaN) series light emitting diodes have been applied and developed for about 10 years. GaN-based LEDs have changed the LED technology considerably and are currently used in a variety of applications, including color LED displays, LED traffic signals and white LEDs. Recently, high-efficiency white LEDs are expected to replace fluorescent lamps. In particular, the efficiency of white LEDs has reached a level similar to that of conventional fluorescent lamps.

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

In general, since the P-type semiconductor layer has a high specific resistance, current is not evenly distributed in the P-type semiconductor layer, current is concentrated in a portion where the P-electrode is formed, and current flows intensively through a corner. do. Current concentration leads to a reduction of the light emitting area, and consequently lowers the light emitting efficiency. In order to solve this problem, a technique of forming a transparent electrode layer having a low specific resistance on the P-type semiconductor layer to achieve current dispersion is used. Since the current flowing from the P-electrode is dispersed in the transparent electrode layer and flows into the P-type semiconductor layer, the light emitting area of the light emitting diode can be widened.

However, since the transparent electrode layer absorbs light, its thickness is limited, and thus there is a limit in current dispersion. In particular, in the large area light emitting diode of about 1 mm 2 or more used for high power, current dispersion using the transparent electrode layer is limited.

On the other hand, the current flows through the semiconductor layers and exits to the N-electrode. Accordingly, the current is concentrated in the portion where the N-electrode is formed in the N-type semiconductor layer, which means that the current flowing in the semiconductor layer is concentrated near the region where the N-electrode is formed. Therefore, there is also a need for a light emitting diode capable of improving current concentration in the N-type semiconductor layer.

In general, a diagonal electrode structure shown in FIG. 1 and a large-area structure + a symmetric extended structure shown in FIG. 2 are introduced for uniform current spreading in a light emitting diode.

1 is a view for explaining a light emitting diode having a conventional diagonal electrode structure, FIG. 2 is a view for explaining a light emitting diode having a conventional large-area structure + symmetric extended electrode structure, Figure 3 is a cut line of FIG. A cross section taken along AA. In FIG. 1, 1 is an N-type electrode, 2 is a P-type electrode, 3 is an exposed N-type semiconductor layer, and 4 is a transparent electrode layer. 2 and 3, 111 is a substrate, 113 is an N-type semiconductor layer, 115 is an active layer, 117 is a P-type semiconductor layer, 119 is a transparent electrode layer, and 122 and 123 are extensions.

Referring to FIG. 1, the diagonal electrode structure may exhibit a large effect in a small sized light emitting diode, but as the area of the light emitting diode increases, a current concentration phenomenon is enhanced in the center, thereby preventing light emission except the center. This happens. In addition, the electrode pattern of the simple face-to-face structure also has the same problems as the diagonal electrode structure.

Meanwhile, referring to FIGS. 2 and 3, the conventional large-area structure and the symmetric extension structure are mainly used for the large sized light emitting diodes, but the extensions 132 and 133 of the P electrode 131 may be used. ) And the extension 122 and 123 of the N electrode 121, there is an inevitable problem that the sacrifice of the emission area is reduced.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting diode capable of reducing a reduction in light emitting area while uniformly distributing a current flowing during operation.

According to one aspect of the invention, the lower semiconductor layer formed on the substrate; An upper semiconductor layer disposed on the lower semiconductor layer to expose at least a portion of edge regions of the lower semiconductor layer; A lower electrode formed adjacent to a first side on the exposed lower semiconductor layer; An upper electrode formed on the upper semiconductor layer adjacent to the second side opposite to the first side; A first lower extension part extending from the lower electrode on the exposed lower semiconductor layer adjacent to the first side and a second lower part extending from the lower electrode and adjacent to the third side adjacent to the first side; An extension; And a first upper extension extending from the upper electrode on the upper semiconductor layer and formed adjacent to the second side, and a second upper extension extending from the upper electrode and adjacent to the fourth side adjacent to the second side. A light emitting diode having a uniform current density characteristic including a portion is provided.

Preferably, the lower electrode may be formed in the middle of the first side, and the upper electrode may be formed in the middle of the second side.

Preferably, the lower electrode and the upper electrode may be formed at positions deflected to one side and the other side from the middle portion of the first side and the second side, respectively.

Preferably, the upper electrode may further have a third upper extension formed on the first upper extension or the second upper extension.

Preferably, the lower electrode may further have a third lower extension formed on the first lower extension or the second lower extension.

Preferably, the upper electrode may further have a third upper extension formed in the first upper extension or the second upper extension in correspondence with the third extension.

Preferably, the light emitting diode may further include a transparent electrode layer formed on the upper semiconductor layer.

According to the present invention, it is possible to evenly distribute the current flowing during the operation of the light emitting diode, it is possible to reduce the reduction in the light emitting area.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; The following embodiments are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, it is to be understood that the present invention is not limited to the embodiments described below and may be embodied in other forms.

4 is a plan view illustrating a light emitting diode having an electrode structure for current dispersion according to an embodiment of the present invention, FIG. 5 is a cross-sectional view taken along the line BB of FIG. 4, and FIG. 6 is a line CC of FIG. 4. A cross section taken along.

4 to 6, the first conductivity type lower semiconductor layer 13 is positioned on the substrate 11. The substrate 11 is not particularly limited and may be a sapphire substrate.

The second conductive upper semiconductor layer 17 is positioned on the first conductive lower semiconductor layer 13. Meanwhile, the upper semiconductor layer 17 is located in an area surrounded by the edges of the lower semiconductor layer 13 so that at least some of the edge regions of the lower semiconductor layer 13 are exposed. Meanwhile, an active layer 15 is interposed between the lower semiconductor layer 13 and the upper semiconductor layer 17. The active layer 15 is located below the upper semiconductor layer 17 so that at least some of the edge regions of the lower semiconductor layer 13 are still exposed.

In more detail, a portion of the edge regions of the lower semiconductor layer 13 is exposed. The lower portions positioned at both sides with respect to the first corner portion (the lower left corner portion in FIG. 3) of the substrate 11. At least some of the edge regions of the semiconductor layer are exposed.

Meanwhile, edge regions of the lower semiconductor layers positioned at both sides of the second corner portion (the corner portion of the upper right side in FIG. 3) facing the first corner portion of the substrate 11 may not be exposed. However, the present invention is not limited thereto, and for example, the lower semiconductor layer positioned at both sides with respect to the second corner portion (the corner portion at the upper right corner in FIG. 3) facing the first corner portion of the substrate 11. At least some of the edge regions of the can be exposed.

The lower semiconductor layer 13, the active layer 15, and the upper semiconductor layer 17 may be formed of a gallium nitride-based compound semiconductor material, that is, (B, Al, In, Ga) N, but are not limited thereto. . The active layer 15 has a composition element and composition ratio determined so as to emit light of a desired wavelength such as ultraviolet light or blue light, and the lower semiconductor layer 13 and the upper semiconductor layer 17 have a band compared to the active layer 15. The gap is formed of a large material.

The lower semiconductor layer 13 and / or the upper semiconductor layer 17 may be formed as a single layer, as shown, but may be formed in a multilayer structure. In addition, the active layer 15 may have a single quantum well or multiple quantum well structures. In addition, a buffer layer (not shown) may be interposed between the substrate 11 and the lower semiconductor layer 13. The buffer layer is employed to mitigate lattice mismatch between the substrate 11 and the underlying semiconductor layer 13 to be formed thereon.

The semiconductor layers 13, 15, and 17 may be formed using MOCVD or MBE technology, and may be patterned to expose regions of the lower semiconductor layer 13 using a photolithography and etching process.

On the other hand, the lower electrode 21 is positioned on the exposed lower semiconductor layer 13 adjacent to the first side of the substrate 11 (the lower middle in FIG. 4). In addition, a transparent electrode layer 19 is formed on the upper semiconductor layer 17, and an upper portion is formed on the transparent electrode layer 19 in a portion adjacent to the second side opposite to the first side (upper middle in FIG. 4). The electrode 31 is located.

On exposed edge regions of the lower semiconductor layer 13, adjacent to the first lower extension part 22 extending from the lower electrode 21 adjacent to the first side and the third side adjacent to the first side. As a result, a second lower extension part 23 extending from the lower electrode 21 is formed. The lower electrode 21, the first lower extension 22, and the second lower extension 23 may be formed together through the same material and the same process. For example, when the lower semiconductor layer is N-type, the lower electrode and the lower extensions may be formed of Ti / Al using a lift off technique.

The transparent electrode layer 19 may have an opening that exposes a portion of the upper semiconductor layer 17 of the second region of the substrate. In this case, the upper electrode 31 covers the opening and contacts the upper semiconductor layer 17.

In general, the transparent electrode layer 19 is formed of ITO or Ni / Au to transmit light, and also has ohmic contact with the upper semiconductor layer to lower the contact resistance. However, the upper electrode 31 is not light-transmitting and cannot be ohmic contacted to the upper semiconductor layer. Therefore, by bringing the upper electrode 31 directly into the upper semiconductor layer 17, it is possible to prevent the current flowing below the upper electrode 31, the light generated by this is absorbed by the upper electrode 31 is lost Can be prevented.

Meanwhile, a first upper extension part 32 extends from the upper electrode 31 and is formed on the transparent electrode layer 19 adjacent to the second side, and a second upper extension part 33 is formed on the upper electrode ( Extending from 31) adjacent to the fourth side adjacent to the second side. The upper electrode 31, the first upper extension 32, and the second upper extension 33 may be formed by the same material and the same process.

3 and 5 will be compared with respect to the current distribution and the light emitting area area in the light emitting diode according to the prior art and the light emitting diode according to the embodiment of the present invention.

When comparing FIG. 3 and FIG. 5, although there is no difference in the left part in each drawing, it can be seen that there is a large difference in the area of the light emitting area in the right part. That is, it can be seen that the length of the active layer 15 remaining in FIG. 5 is much larger than the length of the active layer 115 remaining in FIG. That is, it can be seen that the light emitting diode according to the exemplary embodiment of the present invention shown in FIG. 5 has more light emitting regions than the light emitting diode according to the related art shown in FIG. 3. Therefore, it is possible to effectively solve the conventional reduction of the light emitting area.

In addition, as shown in FIG. 4, the first lower extension part 22 and the second lower extension part 23 of the lower electrode 21 and the first upper extension part of the upper electrode 31 formed corresponding thereto ( 32) and the second upper extension 33 can make the current density uniform.

7 is a plan view illustrating a light emitting diode having electrode extensions for current distribution according to another embodiment of the present invention. According to another embodiment of the present invention, the position of the upper electrode and the lower electrode is modified compared to the embodiment described in Figures 4 to 6, accordingly the first lower extension, the second lower extension And it can be seen that the shape of the first upper extension, the second upper extension is modified.

Referring to FIG. 7, the lower electrode 21a is located closer to the left edge by deflecting to the left side as compared with FIG. 4, and the upper electrode 31a is located closer to the right edge by deflecting to the right than in FIG. 4. As a result, the first lower extension portion 22a is longer than in FIG. 4, and the second lower extension portion 23a is shorter than in FIG. 4. Similarly, the first upper extension 32a is longer than in FIG. 4, and the second upper extension 33a is shorter than in FIG. 4.

8 is a plan view illustrating a light emitting diode having electrode extensions for current distribution according to another embodiment of the present invention. According to another embodiment of the present invention below, the third lower extension part 24 and the third upper extension part 34 are formed on the upper electrode and the lower electrode, respectively, as compared with the embodiment described with reference to FIG. 7. It is. In this case, the third lower extension part 24 and the third upper extension part 34 may be formed at positions corresponding to each other, and the third lower extension part 24 may be the first lower extension part 22 or the second. The lower extension 23 may be formed, and the third upper extension 34 may be formed at the first upper extension 32 or the second upper extension 33.

Referring to FIG. 8, the third lower extension part 24 is formed in a state in which the lower electrode 21b is deflected to the left and is located close to the left edge. The third upper extension part 34 is formed in the state in which the upper electrode 31a is deflected to the right and located close to the right edge.

While some embodiments of the present invention have been described by way of example, those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential features thereof. Therefore, the embodiments described above should not be construed as limiting the technical spirit of the present invention but merely for better understanding. The scope of the present invention is not limited to these embodiments, and should be interpreted by the following claims, and the technical spirit within the equivalent scope should be interpreted as being included in the scope of the present invention.

1 is a view for explaining a light emitting diode having a conventional diagonal electrode structure.

2 is a view for explaining a light emitting diode having a conventional large surface structure + symmetric extended electrode structure.

3 is a cross-sectional view taken along the line A-A of FIG.

4 is a plan view illustrating a light emitting diode having an electrode structure for current dispersion according to an embodiment of the present invention.

5 is a cross-sectional view taken along the line B-B of FIG. 4.

6 is a cross-sectional view taken along the line C-C of FIG. 4.

7 is a plan view illustrating a light emitting diode having electrode extensions for current distribution according to another embodiment of the present invention.

8 is a plan view illustrating a light emitting diode having electrode extensions for current distribution according to another embodiment of the present invention.

Claims (7)

A lower semiconductor layer formed on the substrate; An upper semiconductor layer disposed on the lower semiconductor layer to expose at least a portion of edge regions of the lower semiconductor layer; A lower electrode formed adjacent to a first side on the exposed lower semiconductor layer; An upper electrode formed on the upper semiconductor layer adjacent to the second side opposite to the first side; A first lower extension part extending from the lower electrode on the exposed lower semiconductor layer adjacent to the first side and a second lower part extending from the lower electrode and adjacent to the third side adjacent to the first side; An extension; And A first upper extension extending from the upper electrode on the upper semiconductor layer and formed adjacent to the second side; and a second upper extension extending from the upper electrode and adjacent to a fourth side adjacent to the second side; Includes; A third lower extension extending directly from the lower electrode and formed between the first lower extension and the second lower extension; And And a third upper extension extending directly from the upper electrode to correspond to the third lower extension, wherein the third upper extension is formed between the first upper extension and the second upper extension. Light emitting diode having a. The method according to claim 1, And the lower electrode is formed in the middle of the first side, and the upper electrode is formed in the middle of the second side. The method according to claim 1, And the lower electrode and the upper electrode are formed at positions deflected to one side and the other side from the middle portions of the first side and the second side, respectively. delete delete delete The method according to claim 1, Light emitting diode having a uniform current density characteristics, characterized in that it further comprises a transparent electrode layer formed on the upper semiconductor layer.

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