KR100650189B1 - High brightness nitride semiconductor light emitting device - Google Patents

Abstract

A high brightness nitride based semiconductor light emitting device is provided to improve a current spreading effect and to prevent the loss of light reflected from a reflective electrode by forming the reflective electrode and a transparent electrode in parallel on a nitride semiconductor layer. An N type nitride semiconductor layer(120) is formed on a substrate(110). An active layer(130) is formed on the N type nitride semiconductor layer. A P type nitride semiconductor layer(140) is formed on the active layer. A reflective electrode(180) is formed on the P type nitride semiconductor layer. A transparent electrode(150) is formed on the P type nitride semiconductor layer parallel with the reflective electrode. A P type bonding pad(165) is formed on the reflective electrode. An N type electrode(170) is formed on the N type nitride semiconductor layer. An N type bonding pad(175) is formed on the N type electrode.

Description

High Brightness Nitride Semiconductor Light Emitting Device {HIGH BRIGHTNESS NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

1 is a cross-sectional view showing the structure of a horizontal nitride-based semiconductor light emitting device according to the prior art.

2 is a cross-sectional view showing the structure of another horizontal nitride-based semiconductor light emitting device according to the prior art.

3 is a cross-sectional view showing the structure of a high-brightness nitride-based semiconductor light emitting device according to a first embodiment of the present invention.

4 is a cross-sectional view showing a high brightness nitride-based semiconductor light emitting device according to a first modification of the first embodiment.

5 is a cross-sectional view showing a high brightness nitride-based semiconductor light emitting device according to a second modification of the first embodiment.

6 is a cross-sectional view showing the structure of a high-brightness nitride-based semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view of a high luminance nitride semiconductor light emitting device according to a first modification of the second embodiment; FIG.

8 is a cross-sectional view showing a high brightness nitride-based semiconductor light emitting device according to a second modification of the second embodiment.

<Explanation of symbols for main parts of the drawings>

110 substrate 120 n-type nitride semiconductor layer

130: active layer 140: p-type nitride semiconductor layer

150: transparent electrode 165: p-type bonding pad

170: n-type electrode 175: n-type bonding pad

180: reflective electrode

The present invention relates to a nitride-based semiconductor light emitting device, and more particularly to a high brightness nitride-based semiconductor light emitting device with high luminous efficiency.

In general, nitride semiconductors are actively employed in optical devices for generating short wavelength light such as blue or green as materials having relatively high energy band gaps (for example, about 3.4 eV in GaN semiconductors). As the nitride semiconductor, a material having an Al _x In _y Ga _(1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1) is widely used.

Such nitride-based semiconductor light emitting devices are classified into horizontally structured light emitting diodes and vertically structured light emitting diodes.

Next, a horizontal nitride semiconductor light emitting device according to the prior art will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing the structure of a horizontal nitride semiconductor light emitting device according to the prior art.

As shown in FIG. 1, the horizontal nitride semiconductor light emitting device 100 according to the related art includes a sapphire substrate 110, a GaN buffer layer (not shown), an n-type nitride semiconductor layer 120, and an active layer. 130 and the p-type nitride semiconductor layer 140 are sequentially grown, and the p-type nitride semiconductor layer 140 and the GaN / InGaN active layer 130 are partially etched by a partial etching process. As a result, the upper surface of the n-type nitride semiconductor layer 120 is partially exposed.

An n-type electrode 170 and an n-type bonding pad 175 formed of Cr / Au are formed on the exposed n-type nitride semiconductor layer 120.

In addition, a transparent electrode layer 150 made of ITO or the like is formed on the p-type nitride semiconductor layer 140, and a p-type electrode made of Cr / Au is formed on the transparent electrode layer 150. 160 and a p-type bonding pad 165 are formed.

However, since the p-type electrode 160 positioned on the transparent electrode layer 150 is made of Cr / Au, there is a problem of absorbing a part of light emitted from the active layer to lower the overall luminous efficiency of the device.

Accordingly, as shown in FIG. 2, instead of the p-type electrode 160 made of Cr / Au on the transparent electrode layer 150, a material having a high reflectance such as Ag on the transparent electrode layer 150 is shown. A reflective electrode 180 was formed.

However, the reflective electrode 180 formed on the transparent electrode layer 150 as described above has the advantage of improving the overall luminous efficiency of the device by reflecting the light toward the reflective electrode 180 of the light emitted from the active layer In addition, a portion of the light reflected through the reflective electrode 180 through the transparent electrode layer 150 disposed below is absorbed, thereby reducing the reflectance.

As such, when the reflectance of the reflective electrode is reduced, the overall luminous efficiency of the device is also reduced, thereby limiting the luminous efficiency.

Accordingly, an object of the present invention is to provide a high luminance nitride-based semiconductor light emitting device that can maximize the luminous efficiency by improving the current diffusion effect and at the same time increase the reflectance of the reflective electrode using a transparent electrode to solve the above problems. It is.

In order to achieve the above object, the present invention provides an n-type nitride semiconductor layer formed on a substrate, an active layer formed in a predetermined region on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, and the p A reflective electrode formed on the nitride semiconductor layer, a transparent electrode formed on the p-type nitride semiconductor layer on which the reflective electrode is not formed, a p-type bonding pad formed on the reflective electrode, and an n-type on which the active layer is not formed. A high brightness nitride-based semiconductor light emitting device including an n-type electrode formed on a nitride semiconductor layer and an n-type bonding pad formed on the n-type electrode is provided.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the reflective electrode is preferably formed to be in contact with the adjacent transparent electrode.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the reflective electrode is preferably formed so as to be in contact with the adjacent transparent electrode and overlap the upper portion of the transparent electrode.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the reflective electrode is formed so as not to contact the transparent electrode, and the reflective electrode and the transparent electrode are electrically connected to each other through a p-type bonding pad. It is preferable.

In addition, in the high brightness nitride-based semiconductor light emitting device of the present invention, the reflective electrode is preferably formed of a multilayer structure including a reflective layer containing a reflective material, more preferably, the reflective layer and the bonding layer containing a reflective material It consists of the two-layer structure laminated | stacked sequentially. In this case, the bonding layer serves to improve the adhesion of the p-type nitride semiconductor layer in contact with the reflective layer containing the reflective material.

Another object of the present invention for achieving the above object is a first bonding pad, a first reflective electrode formed on the lower surface of the first bonding pad, a transparent electrode formed on the same layer as the first reflective electrode, and the first reflection A first nitride semiconductor layer formed on the bottom surface of the electrode and the transparent electrode, an active layer formed on the bottom surface of the first nitride semiconductor layer, a second nitride semiconductor layer formed on the bottom surface of the active layer, and a second formed on the bottom surface of the second nitride semiconductor layer A high brightness nitride-based semiconductor light emitting device comprising a reflective electrode, a second bonding pad formed on a lower surface of the second reflective electrode, and a structure support layer formed on a lower surface of the second bonding pad.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the first reflective electrode is preferably formed to be in contact with the adjacent transparent electrode.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the first reflective electrode is preferably formed so as to be in contact with the adjacent transparent electrode and overlap the upper portion of the transparent electrode.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the first reflective electrode is formed so as not to be in contact with the transparent electrode, and the first reflective electrode and the transparent electrode are connected to each other through a first bonding pad. It is preferred to be electrically connected.

In the high brightness nitride-based semiconductor light emitting device of the present invention, the first and second reflective electrodes preferably have a multilayer structure including a reflective layer containing a reflective material, more preferably, a reflective material. It consists of a two-layered structure in which the reflective layers and the bonding layers are sequentially stacked. In this case, the bonding layer serves to improve the adhesion of the first nitride semiconductor layer in contact with the reflective layer containing the reflective material.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like parts throughout the specification.

Now, a high brightness nitride-based semiconductor light emitting device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Example  One

First, the high brightness nitride-based semiconductor light emitting device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 3 to 5.

3 is a cross-sectional view illustrating a structure of a high brightness nitride semiconductor light emitting device according to a first embodiment of the present invention, and FIG. 4 is a cross-sectional view showing a high brightness nitride semiconductor light emitting device according to a first modification of the first embodiment. 5 is a cross-sectional view showing a high brightness nitride-based semiconductor light emitting device according to a second modification of the first embodiment.

First, as shown in FIG. 3, the high brightness nitride-based semiconductor light emitting device 100 according to the first embodiment of the present invention includes a buffer layer (not shown) and an n-type nitride semiconductor layer 120 on the substrate 110. ), The active layer 130 and the p-type nitride semiconductor layer 140 are sequentially stacked.

The substrate 110 is preferably formed using a transparent material including sapphire. In addition to sapphire, the substrate 110 may be formed of zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC), and aluminum nitride (AlN).

The buffer layer (not shown) is formed of GaN and may be omitted.

The n-type or p-type nitride semiconductor layers 120 and 140 are formed of GaN layers or GaN / AlGaN layers doped with conductive impurity, respectively, and the active layer 130 is composed of a multi-well structure composed of InGaN / GaN layers. Quantum Well).

Meanwhile, the active layer 130 may be formed of one quantum well layer or a double hetero structure. In addition, the active layer 130 determines whether the diode is a green light emitting device or a blue light emitting device by the amount of indium (In) constituting it. More specifically, about 22% of indium is used for light emitting devices having blue light, and about 40% of indium is used for light emitting devices having green light. That is, the amount of indium used to form the active layer 130 varies depending on the required blue or green wavelength.

A portion of the active layer 130 and the p-type nitride semiconductor layer 140 are removed by mesa etching, exposing a portion of the n-type nitride semiconductor layer 120 on the bottom.

The n-type electrode 170 and the n-type bonding pad 175 are sequentially stacked on a predetermined portion of the n-type nitride semiconductor layer 120 exposed by the mesa etching. Here, the n-type electrode 170 and the n-type bonding pad 175 is made of Cr / Au.

In addition, the p-type nitride semiconductor layer 140 is formed with a transparent electrode 150 and a reflective electrode 180 which simultaneously serves as a reflection role and an electrode. That is, the reflective electrode 180 is in direct contact with the p-type nitride semiconductor layer 140 and is formed in parallel with the adjacent transparent electrode 150 on the p-type nitride semiconductor layer 140. .

As described above, the reflective electrode 180 according to the present invention is different from the reflective electrode (see FIG. 2) formed on the transparent electrode according to the related art, and the transparent electrode 150 is formed on the p-type nitride semiconductor layer 140. Since it is formed side by side and directly in contact with the p-type nitride semiconductor layer, to solve the conventional problem that a portion of the light reflected through the reflective electrode 180 is absorbed and lost by the transparent electrode 150 to improve the luminous efficiency of the device .

Next, the transparent electrode 150 and the reflective electrode 180 formed side by side on the p-type nitride semiconductor layer according to the first embodiment of the present invention will be described in detail.

First, the transparent electrode 150 is a layer for improving the current diffusion effect, and is made of a conductive metal oxide such as indium tin oxide (ITO). In addition, the transparent electrode 150 may be formed of a metal thin film having high conductivity and low contact resistance if the transmittance of the light emitting device is high.

The reflective electrode 180 is a layer for improving light extraction efficiency by reflecting light directed to a p-type bonding pad made of Cr / Au. Although illustrated as a single layer in FIG. 3, aluminum (Al) or silver (Ag) It consists of a multi-layer structure including a reflective layer containing a reflective material such as). For example, the bonding layer and the reflecting layer containing the reflecting material are formed in a double layer structure in which they are sequentially stacked.

Accordingly, in the present invention, the reflective electrode 180 made of a multilayer including at least one reflective layer containing a reflective material while improving the current diffusion effect through the transparent electrode 150 is a p-type nitride semiconductor layer 140 and By directly contacting to minimize the loss of reflectance, it is possible to improve the luminous efficiency of the device.

Meanwhile, as illustrated in FIGS. 4 and 5, the reflective electrode 180 is formed to overlap an upper portion of the adjacent transparent electrode 150 or is transparent without being in contact with the transparent electrode 150. It is possible to be formed to be electrically connected to each other through the electrode 150 and the p-type bonding pad 165.

As shown in FIG. 4, the reflective electrode 180 overlaps the upper portion of the adjacent transparent electrode 150, and the current diffusion effect is improved to reduce the operating voltage of the device.

In addition, as shown in FIG. 5, when the reflective electrode 180 is not directly in contact with the transparent electrode 150, but is electrically connected through the p-type bonding pad 165, the reflective electrode 180 is provided. Since the reflectance decreases due to contact with the adjacent transparent electrode 150, the light emission efficiency may be further improved.

Example  2

Next, the high-brightness nitride-based semiconductor light emitting device according to the second embodiment of the present invention will be described in detail with reference to FIGS. 6 to 8.

6 is a cross-sectional view illustrating a structure of a high brightness nitride semiconductor light emitting device according to a second embodiment of the present invention, and FIG. 7 is a cross-sectional view showing a high brightness nitride semiconductor light emitting device according to a first modification of the second embodiment. 8 is a cross-sectional view showing a high brightness nitride-based semiconductor light emitting device according to a second modification of the second embodiment.

First, as shown in FIG. 6, in the high brightness nitride-based semiconductor light emitting device 200 according to the second embodiment of the present invention, a first bonding pad 220a made of Cr / Au or the like is formed on the top thereof.

A first reflective electrode 230a is formed on the bottom surface of the first bonding pad 220a.

Meanwhile, in the present exemplary embodiment, the transparent electrode 260 is formed on one side of the first reflective electrode 230a, that is, the same layer as the first reflective electrode 230a in order to maximize the current diffusion efficiency of the device.

In this case, the first reflective electrode 230a is a layer for reflecting light directed to the first bonding pad 220a made of Cr / Au to improve light extraction efficiency, and is illustrated as a single layer in FIG. 6. It is composed of a multilayer structure including a reflective layer containing a reflective material such as (Al) or silver (Ag). For example, the bonding layer and the reflecting layer containing the reflecting material are formed in a double layer structure in which they are sequentially stacked.

Accordingly, in the present invention, the first reflective electrode 230a formed of a multilayer including at least one reflective layer containing a reflective material while improving the current diffusion effect through the transparent electrode 260 is parallel to the transparent electrode 260. The amount of light that is formed and absorbed and lost by the transparent electrode 260 may be minimized, thereby improving luminous efficiency of the device.

Meanwhile, as illustrated in FIGS. 7 and 8, the first reflective electrode 230a is formed to overlap with an upper portion of the adjacent transparent electrode 260, or does not contact the transparent electrode 260 without being in contact with each other. The transparent electrode 260 and the first bonding pad 230a may be formed to be electrically connected to each other.

As shown in FIG. 7, the first reflective electrode 220a overlaps the upper portion of the adjacent transparent electrode 260, and the current diffusion effect is improved to reduce the operating voltage of the device. have.

In addition, as shown in FIG. 8, when the first reflective electrode 220a is not directly in contact with the transparent electrode 260 and is electrically connected through the first bonding pad 230a, the first reflection electrode 220a may be electrically connected. Since the electrode 220a may increase the reflectance reduced due to the contact with the transparent electrode 260, there is an advantage of further improving the light emission efficiency.

In addition, a first nitride semiconductor layer 240a, an active layer 250, and a second nitride semiconductor layer 240b are sequentially stacked on the lower surfaces of the first reflective electrode 220a and the transparent electrode 260.

The first or second nitride semiconductor layers 240a and 240b may be GaN layers or GaN / AlGaN layers doped with a conductive impurity, and the active layer 250 may be a multi-well structure composed of InGaN / GaN layers. Quantum Well).

A second reflective electrode 230b and a second bonding pad 220b are sequentially stacked on the lower surface of the second nitride semiconductor layer 240b. In this case, the second reflective electrode 230b is also a layer for improving light extraction efficiency by reflecting light directed to the second bonding pad 220b made of Cr / Au similarly to the first reflective electrode 230a. Although illustrated as a single layer in FIG. 6, the multilayer structure includes a reflective layer containing a reflective material such as aluminum (Al) or silver (Ag).

The structural support layer 210 is bonded to the bottom surface of the second bonding pad 220b by a conductive bonding layer (not shown). In this case, the structural support layer 210 serves as a supporting layer and an electrode of the final LED element, and is made of a silicon (Si) substrate, a GaAs substrate, a Ge substrate, or a metal layer. The metal layer may be formed by electrolytic plating, electroless plating, thermal evaporator, e-beam evaporator, sputter, chemical vapor deposition (CVD), or the like.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

As described above, the present invention forms a reflection electrode and a transparent electrode side by side on the nitride semiconductor layer, thereby improving the current diffusion effect through the transparent electrode and at the same time a portion of the light reflected by the reflection electrode is absorbed by the transparent electrode and lost Can be prevented to maximize the overall luminous efficiency of the device.

Therefore, the present invention has the effect of improving the characteristics and reliability of the high brightness nitride-based semiconductor light emitting device.

Claims (16)

An n-type nitride semiconductor layer formed on the substrate; An active layer formed in a predetermined region on the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the active layer; A reflective electrode formed on the p-type nitride semiconductor layer; A transparent electrode formed on the p-type nitride semiconductor layer on which the reflective electrode is not formed; A p-type bonding pad formed on the reflective electrode; An n-type electrode formed on the n-type nitride semiconductor layer on which the active layer is not formed; And A high brightness nitride-based semiconductor light emitting device comprising a; n-type bonding pad formed on the n-type electrode. The method of claim 1, The reflective electrode is in contact with the transparent electrode adjacent to each other, characterized in that the high brightness nitride-based semiconductor light emitting device. The method of claim 2, And the reflective electrode is in contact with the adjacent transparent electrode and overlaps with an upper portion of the transparent electrode. The method of claim 1, The reflective electrode is a high brightness nitride-based semiconductor light emitting device, characterized in that not in contact with the transparent electrode. The method of claim 4, wherein And the reflective electrode and the transparent electrode are electrically connected to each other through the p-type bonding pad. The method of claim 1, The reflective electrode is a high brightness nitride-based semiconductor light emitting device, characterized in that the multi-layer structure including a reflective layer containing a reflective material. delete The method of claim 6, The reflective electrode is a high brightness nitride-based semiconductor light-emitting device, characterized in that consisting of a two-layer film in which the bonding layer and the reflective layer containing the reflective material are sequentially stacked. A first bonding pad; A first reflective electrode formed on a lower surface of the first bonding pad; A transparent electrode formed on the same layer as the first reflective electrode; A first nitride semiconductor layer formed on the lower surface of the first reflective electrode and the transparent electrode; An active layer formed on a lower surface of the first nitride semiconductor layer; A second nitride semiconductor layer formed on the lower surface of the active layer; A second reflective electrode formed on the bottom surface of the second nitride semiconductor layer; A second bonding pad formed on a bottom surface of the second reflective electrode; And And a structure support layer formed on a lower surface of the second bonding pad. The method of claim 9, The first reflective electrode is in contact with the adjacent transparent electrode, the high brightness nitride-based semiconductor light emitting device, characterized in that. The method of claim 9, The first reflective electrode is in contact with the adjacent transparent electrode and the high brightness nitride-based semiconductor light emitting device, characterized in that overlapping the upper portion of the transparent electrode. The method of claim 9, The first reflective electrode is not in contact with the transparent electrode, high brightness nitride-based semiconductor light emitting device, characterized in that. The method of claim 12, The first reflective electrode and the transparent electrode, the high brightness nitride-based semiconductor light emitting device, characterized in that electrically connected to each other through the first bonding pad. The method of claim 9, The first and second reflective electrodes, the high brightness nitride-based semiconductor light emitting device, characterized in that the multi-layer structure including a reflective layer containing a reflective material. delete The method of claim 14, The first and second reflective electrodes, the high brightness nitride-based semiconductor light-emitting device, characterized in that consisting of a two-layer film in which the bonding layer and the reflective layer containing the reflective material are sequentially stacked.

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