KR100655163B1 - Light emitting element and method for manufacturing thereof - Google Patents

Abstract

A light emitting device is provided to increase light extraction efficiency of a light emitting diode by stacking two disks having different radii to fabricate the light emitting diode. A first gallium nitride layer(120) is formed in a disk type on a substrate(110). A disk-type active layer(130) is formed in a relatively high region of the first gallium nitride layer. A second gallium nitride layer(140) is formed in a disk type on the active region. A first electrode(160) is formed in a relatively low region of the first gallium nitride layer. A second electrode(170) is formed on the second gallium nitride layer. The radius of the first gallium nitride layer is greater than that of the active layer. A current spreading layer(150) is formed as a disk type on the second gallium nitride layer, and the second electrode can be positioned on the current spreading layer.

Description

LIGHT EMITTING ELEMENT AND METHOD FOR MANUFACTURING THEREOF

1 is a schematic diagram illustrating Snell's law.

2 is a perspective view schematically illustrating a structure of a general gallium nitride based light emitting diode.

3A and 3B are cross-sectional views illustrating a bonding method of the light emitting diode chip illustrated in FIG. 2.

4 is a perspective view illustrating a light extraction shape of a general gallium nitride based light emitting diode.

5 is a perspective view illustrating a light emitting diode according to a first embodiment of the present invention.

FIG. 6 is a cross-sectional view of the light emitting diode shown in FIG. 5 taken along the line II ′.

7A to 7F are cross-sectional views illustrating a manufacturing process of the light emitting diode shown in FIG. 5.

8A and 8B are conceptual views illustrating the light extraction effect of the light emitting diode according to the present invention.

9 is a graph showing a light extraction efficiency calculation result of the light emitting diode according to the first embodiment of the present invention.

10 is a perspective view illustrating a light emitting diode according to a second embodiment of the present invention.

FIG. 11 is a cross-sectional view of the light emitting diode shown in FIG. 10 taken along a cutting line II-II '.

FIG. 12 is a plan view of the light emitting diode of FIG. 10.

13A to 13I are cross-sectional views illustrating a manufacturing process of the light emitting diode shown in FIG. 10.

14 is a perspective view illustrating a light emitting diode according to a third embodiment of the present invention.

FIG. 15 is a plan view of the light emitting diode shown in FIG. 14.

16 is a graph showing a light extraction efficiency calculation result of the light emitting diode according to the third embodiment of the present invention.

The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly to a light emitting device having a structure for increasing the extraction efficiency (Extraction efficiency) and a manufacturing method thereof.

In general, a light emitting diode, which is a light emitting device, is spotlighted as a next-generation lighting that replaces an incandescent bulb or a fluorescent lamp. In particular, demand is expected to increase further, as it is used for lighting of large area LCDs with long lifespan.

However, most of the light generated by total reflection due to the difference in refractive index between the materials constituting the light emitting diode (sapphire substrate, epi, epoxy, etc.) is trapped. The total reflection occurs when light travels from a material having a relatively high refractive index to a material having a low refractive index at an interface having a different refractive index. The total reflection is determined by Snell'law.

1 is a schematic diagram illustrating Snell's law. Where n1 and n2 are the refractive indices of the first and second media, respectively, and θ1 and θ2 are the incident angle and the exit angle, respectively. Wherein the refractive index of the second medium is greater than the refractive index of the first medium.

Referring to FIG. 1, when light is transmitted from the second medium having a relatively large refractive index to the first medium having a relatively small refractive index, the exit angle θ2 of the transmitted light has an angle greater than the incident angle θ1.

In particular, the sapphire substrate and the gallium nitride (GaN) layer employed in the gallium nitride-based light emitting diode widely used as a blue light source has a refractive index of 1.8 and 2.5, respectively, and thus there is a significant difference from the air layer having a refractive index of 1. This large difference in refractive index causes a large portion of the light generated by the light emitting diode to be trapped inside. For example, the critical angle of the interface between the gallium nitride (GaN) layer and the sapphire substrate is about 46 degrees. Therefore, light having an angle of incidence greater than 46 degrees is trapped inside the gallium nitride (GaN) layer.

In the same manner, the critical angle between the sapphire substrate and the air interface is 33.5 degrees, and the critical angle between the gallium nitride (GaN) layer and the air layer is about 23.6 degrees. Therefore, light having an incident angle greater than 33.5 degrees is trapped inside the sapphire substrate, and light having an incident angle greater than 23.6 degrees is trapped inside the gallium (GaN) layer.

As such, since a large amount of light generated in the light emitting diode is not extracted due to total reflection of the interface, there is a problem that reduces the external quantum efficiency of the entire light emitting diode, thereby reducing the light output of the light emitting diode.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a gallium nitride-based light emitting device that can increase the light extraction efficiency to implement a high brightness light emitting device.

Another object of the present invention is to provide a method of manufacturing the above light emitting device.

In order to realize the above object of the present invention, a light emitting device according to an embodiment includes a substrate, a first gallium nitride layer, a disk-type active layer, a second gallium nitride layer, a first electrode, and a second electrode. The first gallium nitride layer is formed in a disk shape on the substrate. The disk-like active layer is formed in a relatively high region of the first gallium nitride layer. The second gallium nitride layer is formed in a disk shape on the active layer. The first electrode is formed in a relatively low region of the first gallium nitride layer. The second electrode is formed on the second gallium nitride layer.

Preferably, the light emitting device further includes a current spreading layer formed in a disk shape on the second gallium nitride layer, and the second electrode is formed on the current spreading layer.

Preferably, the radius of the first gallium nitride layer is larger than the radius of the active layer.

Preferably, the ratio of the radius of the first gallium nitride layer and the radius of the active layer is 4:10.

Preferably, the substrate has a rectangular shape that covers the disk shape. Here, the first gallium nitride layer is formed in a first region oriented to one side from the center of the substrate, is formed in a portion of the peripheral region surrounding the first region, the first electrically connected to the first electrode It is preferable to further include an electrode pad, it is preferable to further include a second electrode pad formed in another part of the peripheral region surrounding the first region, and electrically connected to the second electrode. In this case, while covering the first gallium nitride layer, the active layer and the second gallium nitride layer, the first connecting member connecting the first electrode and the first electrode pad is insulated, and the second electrode and the second electrode It is preferable to further include an insulating layer for insulating the second connecting member connecting the pad.

Preferably, the substrate is characterized in that it has a disk shape.

Preferably, the first gallium nitride layer is doped with n-type or p-type, and the second gallium nitride layer is doped with a polarity opposite to the first gallium nitride layer to form a p-n junction surface.

In order to achieve the above object of the present invention, a light emitting device includes a disk substrate, a first gallium nitride layer, a disk active layer, a second gallium nitride layer, a first electrode, and a second electrode. The first gallium nitride layer is formed in a disk shape on the disk substrate. The disk-like active layer is formed in a relatively high region of the first gallium nitride layer. The second gallium nitride layer is formed in a disk shape on the active layer. The first electrode is formed in a relatively low region of the first gallium nitride layer. The second electrode is formed on the second gallium nitride layer.

According to one or more exemplary embodiments, a method of manufacturing a light emitting device includes: (a) sequentially growing a first gallium nitride layer, an active layer, and a second gallium nitride layer on a substrate; (b) forming a current spreading layer over the second gallium nitride layer; (c) realizing an ohmic contact between the current spreading layer and the second gallium nitride layer; (d) forming a region of the second gallium nitride layer, the active layer and the first gallium nitride having a relatively small radius disk shape; (e) exposing a surface of the substrate to form a first gallium nitride layer having a relatively large radius disk shape; And (f) forming a first electrode in a central region of the relatively high current spreading layer, and forming a second electrode in the relatively low first gallium nitride layer.

According to another aspect of the present invention, there is provided a method of manufacturing a light emitting device, including: (a) sequentially growing a first gallium nitride layer, an active layer, and a second gallium nitride layer on a substrate; (b) forming a current spreading layer over the second gallium nitride layer; (c) realizing an ohmic contact between the current spreading layer and the second gallium nitride layer; (d) forming a region of the second gallium nitride layer, the active layer and the first gallium nitride having a relatively small radius disk shape; (e) exposing a surface of the substrate to form a first gallium nitride layer having a relatively large radius disk shape; (f) forming a first electrode electrically connected to the first gallium nitride layer on the first gallium nitride layer; (g) depositing an insulating layer on the resultant of step (f); (h) removing the insulating layer of the region of the first electrode and the region where the p-electrode is to be formed; And (i) forming a second electrode electrically connected to the second gallium nitride layer exposed by step (h).

According to such a light emitting device and a method of manufacturing the same, the light extraction efficiency can be improved by making the gallium nitride layer into a relatively large disk shape and the active layer into a relatively small disk shape.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the scope of the invention to those skilled in the art will fully convey. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. As described in the drawing, when it is described from an observer's point of view, when a part such as a layer, a film, an area, or a plate is "on" another part, it is not only when another part is "directly" but also another part in between. It also includes the case. On the contrary, when a part is "just above" another part, it means that there is no other part in the middle.

2 is a perspective view schematically illustrating a structure of a general gallium nitride based light emitting diode.

Referring to FIG. 2, a general gallium nitride based light emitting diode includes a base substrate 10, an n-type gallium nitride layer 11, an active layer 12, a p-type gallium nitride layer 13, and n−. The electrode 20, the p-electrode 21, and the p-type transparent electrode 22 are formed. In operation, when current flows through the n-electrode 20 and the p-electrode 21, light is extracted (or emitted) while electron-hole recombination occurs in the active layer 12.

In order to grow the gallium nitride layer 11 on the base substrate 10, a metal organic chemical vapor deposition (MOCVD) apparatus is usually used. The base substrate 10 is a sapphire substrate or a silicon carbide substrate.

First, a buffer layer (not shown) is formed on the base substrate 10 to assist the growth of the gallium nitride layer 11, and the n-type gallium nitride layer 11 and the active layer ( 12) and the p-type gallium nitride layer 13 are grown in sequence.

In general, a diode forms an electrode on top of a p-type gallium nitride layer and a bottom of a base substrate connected to an n-type gallium nitride layer to flow current through a p-n junction. However, since the sapphire used as the substrate of the gallium nitride-based light emitting diode is an insulator, an electrode cannot be formed on the sapphire substrate 10. Therefore, an electrode must be directly formed on the n-type gallium nitride layer 11.

To this end, some regions of the p-type gallium nitride layer 13, the active layer 12, and the n-type gallium nitride layer 11 of the portion where the electrode is to be formed are removed, and the exposed n-type gallium nitride layer 11 is formed. The n-electrode 20 is formed thereon. Since the light is emitted from the p-n junction surface, the p-electrode 21 is formed at the corner of the p-type transparent electrode 22 so that the light is not obscured by the electrode.

As such, when both the p-electrode 21 and the n-electrode 20 are positioned at the top, the current is higher than that of a general diode structure in which the p-electrode 21 and the n-electrode 20 are located in parallel with each other. The distribution is not uniform.

In addition, the p-type gallium nitride layer 13 generally has a higher resistance than the n-type gallium nitride layer 11, and thus, it is more difficult for a current to flow uniformly through the p-type gallium nitride layer 13. . To prevent this, a thin transparent electrode is formed on the entire upper surface of the p-type gallium nitride layer 13 so that current can be transferred to the entire surface of the p-type gallium nitride layer 13.

However, the transparent electrode is formed of a very thin metal layer of about 10 nanometers thick in order to allow light to be transmitted, so the resistance is high. There is a limit to uniform current transfer to the entire surface of the p-type gallium nitride layer using the high resistance transparent electrode.

In addition, the contact resistance with the p-type gallium nitride layer 13 is also high, which leads to deterioration of diode characteristics and generation of heat. The thickness of the transparent electrode can be increased to lower the resistance, but in this case, the absorption and reflectance of the light by the electrode become high, making it difficult to extract light to the outside.

In order to reduce such drawbacks, a method of increasing light emission efficiency of a light emitting diode using a flip chip bonding method has been proposed. That is, a thick electrode may be formed on the entire surface of the p-type gallium nitride layer, and the LED chip may be inverted to be mounted in a package by flip chip bonding.

3A and 3B are cross-sectional views illustrating a bonding method of the light emitting diode chip illustrated in FIG. 2. In particular, FIG. 3A is a cross-sectional view showing a gallium nitride-based LED chip assembled by wire bonding, and FIG. 3B is a cross-sectional view showing a gallium nitride-based LED chip assembled by flip chip bonding.

As shown in FIG. 3A, a lead frame for supplying a current is disposed in a package containing a light emitting diode chip. A light emitting diode chip is attached on the lead frame, and the lead frame and the n-electrode 20 and the p-electrode 21 of the light emitting diode chip are electrically connected with thin metal wires 30a and 30b. In this case, a thin transparent electrode is formed so that light can be emitted through the p-type gallium nitride layer.

Meanwhile, as illustrated in FIG. 3B, in the flip-chip bonding method, another substrate 40 connected to the lead frame is disposed, and solder bumps are disposed at positions corresponding to electrodes of the light emitting diodes on the substrate 40. bumps 31b are formed. The light emitting diode is turned upside down to attach a light emitting diode chip such that the electrodes of the light emitting diode and the solder bumps 31b are connected to each other.

4 is a perspective view illustrating a light extraction shape of a general gallium nitride based light emitting diode.

Referring to FIG. 4, a general gallium nitride-based light emitting diode 50 has a hexahedral shape, and has six escape cones. That is, it has two light escape cones in a direction perpendicular to the substrate surface and four light escape cones in a direction parallel to the substrate surface.

In the case of the gallium nitride-based light emitting device, only light traveling in the solid angle of 23.6 degrees is extracted and the rest cannot be escaped due to total reflection. This is because the critical angle due to total reflection between the gallium nitride layer and air is about 23.6 degrees. As such, since a large amount of light generated in the light emitting diode is not extracted due to total reflection of the interface, it reduces the external quantum efficiency of the entire LED, thereby reducing the light output of the LED.

<Example-1 of Light Emitting Diode>

5 is a perspective view illustrating a light emitting diode according to a first exemplary embodiment of the present invention, and FIG. 6 is a cross-sectional view of the light emitting diode shown in FIG. 5 taken along the line II ′.

5 and 6, the light emitting diode 100 according to the first embodiment of the present invention includes a substrate 110, an n-type gallium nitride layer 120, an active layer 130, and p−. A type gallium nitride layer 140, a current spreading layer 150, an n-electrode 160 and a p-electrode 170 are included. In operation, when current flows through the n-electrode 160 and the p-electrode 170, electron-hole recombination occurs in the active layer 130 to emit light.

The substrate 110 has a rectangular shape, and all the layers formed on the substrate 110 have a disk shape. The first radius r1 of the p-type gallium nitride layer 140 including the active layer 130 and the second radius r2 of the n-type gallium nitride layer 120 are different from each other. In this case, the first radius r1 is smaller than the second radius r2. Preferably, the condition of r1 / r2 <0.8 is satisfied.

The n-type gallium nitride layer 120 formed in a disk shape is formed on the substrate 110. The substrate 110 is a substrate having sapphire, quartz, zinc oxide (ZnO), silicon carbide (SiC), or a metal nitride buffer layer. Various gallium nitride systems described in this embodiment may be a mixture satisfying the conditions of (AlxGa1-x) InyN (here, 0≤x≤1, 0≤y≤1). In order to further increase the light extraction efficiency, the substrate 110 may further have a predetermined roughness on a surface of the substrate 110 which is in contact with the n-type gallium nitride layer 120.

In order to grow the n-type gallium nitride layer 120 or the p-type gallium nitride layer 140 described in the present embodiment, usually, organic organic chemical vapor deposition (MOCVD), molecular beam epitaxy (Molecular Beam) Devices such as Epitaxy (MBE) or Hybrid Vapor Phase Epitaxy (HVPE). Since sapphire used as a substrate of a gallium nitride-based light emitting diode is an insulator, an electrode cannot be formed on the substrate 110. Therefore, an electrode must be formed on the n-type gallium nitride layer 120. To this end, some regions of the p-type gallium nitride layer 140, the active layer 130, and the n-type gallium nitride layer 120 of the portion where the electrode is to be formed are removed, and the exposed n-type gallium nitride layer 120 The n-electrode 160 is formed thereon.

Accordingly, the n-type gallium nitride layer 120 is formed to have a first height corresponding to the central region, and has a second height smaller than the first height to correspond to the peripheral region surrounding the central region.

Since light is emitted from the p-n junction surface, the p-electrode 160 is formed at an edge of the current diffusion layer 150 so that light is not obscured by the electrode.

When both the n-electrode 160 and the p-electrode 170 are located at the top, the n-electrode 160 and the p-electrode 170 have a current distribution in comparison with a general diode structure located parallel to different planes. Is not uniform.

In addition, the p-type gallium nitride layer 140 has a larger resistance than the n-type gallium nitride layer 120, and thus, it is more difficult to uniformly flow current through the p-type gallium nitride layer 140. . In order to prevent this, the current diffusion layer 150, which is a thin transparent electrode, is formed on the entire upper surface of the p-type gallium nitride layer 140 so that the current can be transmitted to the entire surface of the p-type gallium nitride layer 140.

Although the n-type gallium nitride layer 120 doped with n-type has been described as an example of the gallium nitride-based semiconductor layer, it is obvious that the p-type gallium nitride layer may be applied to the p-type gallium nitride layer. Accordingly, an active layer, an n-type gallium nitride layer, and a current diffusion layer are formed on the p-type gallium nitride layer, a p-electrode is formed in a portion of the current diffusion layer, and the p- is exposed while opening a portion of the current diffusion layer. It is apparent that n-electrodes are formed in some regions of the type gallium nitride layer.

7A to 7F are cross-sectional views illustrating a manufacturing process of a light emitting diode according to an embodiment of the present invention.

7A and 7B, a sapphire substrate 110 is prepared, and an n-type gallium nitride layer 120 and an active layer 130 (eg, MQW; multi quantum well) are formed on the sapphire substrate 110. And p-type gallium nitride layer 140 is sequentially grown by organometallic chemical vapor deposition (MOCVD). Although not shown, in order to further increase the light extraction efficiency, the surface of the sapphire substrate 110 in contact with the n-type gallium nitride layer 120 may be further provided with a certain roughness.

Referring to FIG. 7C, after the current diffusion layer 150 is formed by electron beam deposition, an ohmic contact is realized between the current diffusion layer 150 and the p-type gallium nitride layer 140 through heat treatment. The current spreading layer 150 mainly consists of a transparent oxide electrode such as indium tin oxide (ITO) or antimony tin oxide (ATO), and is deposited by evaporation or sputtering. Since the p-type gallium nitride layer 140 and the ITO are difficult to make ohmic contact with each other, the tunnel junction is actually formed by introducing a thin SLS (Super Lattice Structure) on the p-type gallium nitride layer 140. desirable.

Referring to FIG. 7D, the p-type gallium nitride 140 and the active layer 130 have a disk shape having the first radius r1 by using a first mask MA1 having an opaque member having a first radius r1. A portion of the n-type gallium nitride 120 is etched by a dry etching method.

Referring to FIG. 7E, the remaining n − may be formed in a disk shape having the second radius r2 by using the second mask MA2 having the opaque member having the second radius r2 greater than the first radius r1. The type gallium nitride layer 120 is etched by a dry etching method until the substrate surface is exposed.

Referring to FIG. 7F, the p-electrode 160 and the n-electrode 170 are formed on the resultant of FIG. 7E using the third mask MA3. Specifically, the p-electrode 160 is defined by depositing Cr / Ni / Au in a relatively high region of the resultant region of FIG. 7E, that is, a central region of the current diffusion layer 150, and a relatively low region. That is, the n-electrode 170 is defined by depositing Ti / Al / Ti / Au or Cr / Ni / Au on the mesa-etched gallium nitride layer 120.

In the above, the current diffusion layer 150 made of a transparent material is deposited on the p-type gallium nitride layer 140. The top light emitting diode is assembled by wire bonding as shown in FIG. 3A and emits light in a front direction.

However, the p-type gallium nitride layer 140 is in ohmic (Ohmic) contact with the p-contact layer having a high reflecting layer is deposited, it is obvious that it can be applied to a kind of bottom-emitting light emitting diode. The bottom light emitting diode is assembled by flip chip bonding as shown in FIG. 3B and emits light in the rear direction. The p-contact layer is made of Ni / Ag, Ni / Al, Pt / Ag, and the like, and is deposited through an evaporation or sputtering method, an excimer laser, or the like.

8A and 8B are conceptual views illustrating the light extraction effect of the light emitting diode according to the present invention. In particular, FIG. 8A shows the light extraction effect emitted at a particular point when the radius of the active layer is close to the radius of the gallium nitride layer, and FIG. 8B shows the light extraction effect when the change of the active layer is far from the radius of the gallium nitride layer. The light extraction effect is shown.

Referring to FIG. 8A, when the radius r1 of the active layer 130 approaches the radius r2 of the gallium nitride layer 120, an arbitrary point exists near the boundary of the radius r1 of the active layer 130. The light emitted from the light source cannot escape when it enters a specific direction. That is, the light emitted from the point light source may escape only when the angle formed between the tangent normal of the circle defining the gallium nitride layer 120 and the incident angle of light is 23.6 degrees or less (in this case, the critical angle between gallium nitride and air).

However, as shown in FIG. 8B, when the radius r1 of the active layer 130 becomes small to be close to zero, all light emitted from any point light source is limited to the center of the circle (theoretically close to zero) and thus is emitted from the point light source. All the lights can escape.

However, since a light emitting diode having a zero radius of the active layer 130 cannot be manufactured, it is necessary to appropriately select the lower limit of the radius r1 of the active layer 130.

In order to examine the correlation between the ratio (r1 / r2) of the radius (r2) of the gallium nitride layer 120 to the radius (r1) of the active layer 130 and the light extraction efficiency, a computer simulation through ray tracing is performed. It shows in FIG. 9 which shows the result measured by irradiating using.

9 is a graph showing light extraction efficiency of a light emitting diode compared to a radius ratio between an active layer and a gallium nitride layer according to the first embodiment of the present invention.

Referring to FIG. 9, the light extraction efficiency of a typical cubic LED is about 28%.

However, in the disk LED according to the present invention, as the active layer radius r1 is reduced rather than the gallium nitride layer radius R1, the light extraction efficiency increases.

That is, when the radius R1 of the gallium nitride layer 120 and the radius r1 of the active layer 130 are substantially the same, the value is lower than the light extraction efficiency of the cubic light emitting diode.

However, when the radius r1 of the active layer 130 is reduced to exist within about 80% of the radius R1 of the gallium nitride layer 120, the light extraction efficiency is about 30%. Is about 34%. In addition, when present in about 50% or less reaches 39%, it can be seen that the light extraction efficiency is maintained at about 40% below 40%.

As such, it can be seen that the light extraction efficiency of the disk type light emitting diode according to the present invention is increased by about 40% more than the light extraction efficiency (28%) of the general cubic light emitting diode.

<Example 2 of Light Emitting Diode>

10 is a perspective view illustrating a light emitting diode according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view of the light emitting diode shown in FIG. 10 taken along a cutting line II-II '. FIG. 12 is a plan view of the light emitting diode of FIG. 10.

10 to 12, the light emitting diode 200 according to the second embodiment of the present invention includes a substrate 210, an n-type gallium nitride layer 220, an active layer 230, and p−. Type gallium nitride layer 240, current spreading layer 250, insulating layer 255, n-electrode 260, n-electrode pad 262, p-electrode 270 and p-electrode Pad 272. In operation, when current flows through the n-electrode 260 and the p-electrode 270, light is emitted while electron-hole recombination occurs in the active layer 230.

The substrate 210 has a quadrangular shape, and all the layers formed on the substrate 210 have a disk shape, and are formed on one side of the substrate. The first radius r1 of the p-type gallium nitride layer 240 including the active layer 230 and the second radius r2 of the n-type gallium nitride layer 220 are different from each other. In this case, the first radius r1 is smaller than the second radius r2. Preferably, the condition of r1 / r2 <0.8 is satisfied.

The disk-type n-type gallium nitride layer 220 is formed on one side of the substrate 210. The n-type gallium nitride layer 220 is formed to have a first height corresponding to the central region, and is formed to have a second height smaller than the first height to correspond to the peripheral region surrounding the central region.

The current spreading layer 250 is formed on the p-type gallium nitride layer 240.

The insulating layer 255 may include a side surface and an upper surface of the n-type gallium nitride layer 220, a side surface of the active layer 230, a side surface and an upper surface of the p-type gallium nitride layer 240, and the current diffusion layer. Covering the side and top surfaces of the 250, the lower layer is exposed to correspond to the region where the n-electrode 260 is to be formed and the region where the p-electrode 270 is to be formed.

The p-electrode 260 is formed at an edge of the current diffusion layer 250 to prevent light from being blocked by the electrode because light is emitted from the p-n junction surface. The p-electrode pad 262 is formed on the substrate 210 from which the n-type gallium nitride layer 220 is removed. A p-electrode connecting member 263 connecting the p-electrode 260 and the p-electrode pad 262 is further formed, and the p-electrode connecting member 263 is the n-type gallium nitride layer 220. ) And an insulating layer 255 covering the active layer 230 and the p-type gallium nitride layer 250 to be electrically insulated.

When both the n-electrode 260 and the p-electrode 270 are positioned at the top, the n-electrode 260 and the p-electrode 270 have a current distribution compared to a general diode structure in parallel to different planes. Is not uniform.

The n-electrode 270 is formed on the surface of the n-type gallium nitride layer 220 exposed by the insulating layer 255, and the n-electrode pad 272 is the n-type gallium nitride layer 220. It is formed on the removed substrate 210. An n-electrode connecting member 273 connecting the n-electrode 270 and the n-electrode pad 272 is further formed, and the n-electrode connecting member 273 is the n-type gallium nitride layer 220. ) And an insulating layer 255 covering the active layer 230 and the p-type gallium nitride layer 250 to be electrically insulated.

13A to 13I are cross-sectional views illustrating a manufacturing process of the light emitting diode shown in FIG. 10.

13A and 13B, a sapphire substrate 210 is prepared, and an n-type gallium nitride layer 220 and an active layer 230 (eg, MQW; multi quantum well) are disposed on the sapphire substrate 210. And p-type gallium nitride layer 240 is sequentially grown by organometallic chemical vapor deposition (MOCVD).

Referring to FIG. 13C, after forming the current spreading layer 250 by electron beam deposition, an ohmic contact is realized between the current spreading layer 250 and the p-type gallium nitride layer 240 through heat treatment. The current diffusion layer 250 is mainly composed of a transparent oxide electrode such as indium tin oxide (ITO) or antimony tin oxide (ATO), and is deposited by evaporation or sputtering. Since the p-type gallium nitride layer 240 and the ITO are difficult to make ohmic contact with each other, the tunnel junction is actually formed by introducing a thin SLS (Super Lattice Structure) on the p-type gallium nitride layer 240. desirable.

Referring to FIG. 13D, the p-type gallium nitride 240 and the active layer 230 have a disk shape having the first radius r1 by using a first mask MA1 having an opaque member having a first radius r1. A portion of the n-type gallium nitride 220 is etched by a dry etching method. The opaque member formed on the first mask MA1 is formed to be relatively biased to one side.

Referring to FIG. 13E, the remaining n− in the shape of a disk having the second radius r2 is formed by using a second mask MA2 having an opaque member having a second radius r2 greater than the first radius r1. The type gallium nitride layer 220 is etched by a dry etching method until the substrate surface is exposed. The opaque member formed on the second mask MA2 is formed to be relatively biased to one side.

Referring to FIG. 13F, an n-electrode 270 is formed on the n-type gallium nitride layer 220 by using a third mask MA3 on the resultant material of FIG. 13E.

Referring to FIG. 13G, an insulating layer 255 is formed on all surfaces on the resultant shown in FIG. 13F.

Referring to FIG. 13H, the insulating layer 255 on the n-electrode 260 and the region where the p-electrode 270 is to be formed is removed using the fourth mask MA4.

Referring to FIG. 13I, a p-electrode 270, a p-electrode pad 272 extending from the p-electrode 270, and an n-electrode 260 extending from the p-electrode 270 are formed using a fifth mask MA5. An n-electrode pad 262 is formed.

<Example-3 of Light Emitting Diode>

14 is a perspective view illustrating a light emitting diode according to a third embodiment of the present invention, and FIG. 15 is a plan view of the light emitting diode shown in FIG. 14. In particular, there is shown a light emitting diode in which the active layer, gallium nitride layer and the substrate have a disk shape.

14 and 15, a light emitting diode 300 according to a third embodiment of the present invention may include a substrate 310, an n-type gallium nitride layer 320, an active layer 330, and p−. A type gallium nitride layer 340, a current spreading layer 350, an n-electrode 360, and a p-electrode 370 are included. In operation, when current flows through the n-electrode 360 and the p-electrode 370, light is emitted while electron-hole recombination occurs in the active layer 330.

The substrate 310 has a disk shape, and all the layers formed on the substrate 310 have a disk shape. The first radius r of the p-type gallium nitride layer 340 including the active layer 330 and the second radius R of the n-type gallium nitride layer 320 are different from each other. In this case, the first radius r is smaller than the second radius R. Preferably, the condition of r / R <0.8 is satisfied.

An n-type gallium nitride layer 320 formed in a disk shape is formed on the substrate 310. The substrate 310 is a substrate having sapphire, quartz, zinc oxide (ZnO), silicon carbide (SiC), or a metal nitride buffer layer. Various gallium nitride systems described in this embodiment may be a mixture satisfying the conditions of (AlxGa1-x) InyN (here, 0≤x≤1, 0≤y≤1).

In order to grow the n-type gallium nitride layer 320 or the p-type gallium nitride layer 340 described in the present embodiment, the organic organic chemical vapor deposition (MOCVD), molecular beam epitaxy (Molecular) Beam Epitaxy (MBE) or (Hydride Vappor Phase Epitaxy, HVPE), etc. are used. Since sapphire used as a substrate of a gallium nitride-based light emitting diode is an insulator, an electrode cannot be formed on the substrate 310. Therefore, an electrode must be formed on the n-type gallium nitride layer 320. To this end, some regions of the p-type gallium nitride layer 340, the active layer 330, and the n-type gallium nitride layer 320 where the electrode is to be formed are removed, and the exposed n-type gallium nitride layer 320 is removed. The n-electrode 360 is formed thereon.

Accordingly, the n-type gallium nitride layer 320 is formed to have a first height corresponding to the central region, and is formed to have a second height smaller than the first height to correspond to the peripheral region surrounding the central region.

Since light is emitted from the p-n junction surface, the p-electrode 360 is formed at an edge of the current diffusion layer 350 so that light is not obscured by the electrode.

As a method of manufacturing the disk-shaped substrate described in this embodiment, various methods can be used. For example, a disk cutter can be used to fabricate tens of um deep.

FIG. 16 shows the results obtained by investigating using computer simulation through ray tracing in order to examine the correlation between light extraction efficiency and r / R of the light emitting diode according to the present embodiment.

16 is a graph showing a light extraction efficiency calculation result of the light emitting diode according to the third embodiment of the present invention.

14 to 16, the light extraction efficiency of a typical cubic LED is about 28%.

However, in the disk-type light emitting diode (Disk LED) according to the third embodiment of the present invention, as the active layer radius (r) is reduced rather than the gallium nitride layer radius (R), it can be seen that the light extraction efficiency increases. .

That is, when the radius R of the gallium nitride layer 320 and the radius r of the active layer 330 are substantially the same, the light extraction efficiency of the disk type light emitting diode is the same as that of the cubic light emitting diode.

However, if the radius (r) of the active layer 330 is reduced to exist within about 80% of the radius (R) of the gallium nitride layer 320, the light extraction efficiency is about 31%. Is about 38%. In addition, the presence of about 50% reaches about 42%, the light extraction efficiency is maintained at about 45% below 40%.

As such, it can be seen that the light extraction efficiency of the disk type light emitting diode according to the present invention is increased by about 45% more than the light extraction efficiency (28%) of the general cubic light emitting diode.

As described above, when manufacturing the actual disk-shaped light emitting device, it can be seen that the radius of the active layer is about 0.4 times the radius of the n-type gallium nitride is most suitable.

As described above, according to the present invention, by manufacturing a light emitting diode having a shape in which two disks having different radii are stacked, the light extraction efficiency of the light emitting diode can be improved.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (20)

Board; A first gallium nitride layer formed in a disk shape on the substrate; A disk-type active layer formed in a relatively high region of the first gallium nitride layer; A second gallium nitride layer formed in a disk shape on the active layer; A first electrode formed at a relatively low region of the first gallium nitride layer; And A second electrode formed on the second gallium nitride layer, The radius of the first gallium nitride layer is larger than the radius of the active layer, the light emitting device. The light emitting device of claim 1, further comprising a current diffusion layer formed in a disk shape on the second gallium nitride layer, wherein the second electrode is formed on the current diffusion layer. delete The light emitting device of claim 1, wherein a ratio of a radius of the first gallium nitride layer and a radius of the active layer is 10: 4. The light emitting device of claim 1, wherein the substrate has a rectangular shape covering the disk shape. The method of claim 5, wherein the first gallium nitride layer is formed in a first region oriented to one side from the center of the substrate, and is formed in a portion of a peripheral region surrounding the first region, and electrically connected to the first electrode. The light emitting device further comprises a first electrode pad connected to. The light emitting device of claim 6, further comprising a second electrode pad formed on another portion of the peripheral region surrounding the first region and electrically connected to the second electrode. The method of claim 7, wherein the first connecting member connecting the first electrode and the first electrode pad is insulated while covering the first gallium nitride layer, the active layer, and the second gallium nitride layer. The light emitting device of claim 1, further comprising an insulating layer for insulating the second connection member connecting the second electrode pad. The light emitting device of claim 1, wherein the substrate has a disk shape. The method of claim 1, wherein the first gallium nitride layer is doped with an n-type or p-type, and the second gallium nitride layer is doped with a polarity opposite to the first gallium nitride layer to form a pn junction surface. Light emitting device. Disc-shaped substrates; A first gallium nitride layer formed in a disk shape on the disk substrate; A disk-type active layer formed in a relatively high region of the first gallium nitride layer; A second gallium nitride layer formed in a disk shape on the active layer; A first electrode formed at a relatively low region of the first gallium nitride layer; And A second electrode formed on the second gallium nitride layer, The radius of the relatively low region of the first gallium nitride layer is larger than the radius of the active layer. The ratio of the radius of the disk-shaped substrate and the relatively low first gallium nitride layer to the radius of the relatively high first gallium nitride layer, active layer and second gallium nitride layer is 10: 4. Light emitting device. The light emitting device of claim 11, wherein a rear surface of the substrate has a constant roughness. 12. The light emitting device according to claim 11, wherein the substrate in contact with the first gallium nitride layer has a surface of constant roughness. (a) sequentially growing a first gallium nitride layer, an active layer and a second gallium nitride layer on the substrate; (b) forming a current spreading layer over the second gallium nitride layer; (c) realizing an ohmic contact between the current spreading layer and the second gallium nitride layer; (d) forming a region of the second gallium nitride layer, the active layer and the first gallium nitride having a relatively small radius disk shape; (e) exposing a surface of the substrate to form a first gallium nitride layer having a relatively large radius disk shape; And (f) forming a first electrode in a central region of a relatively high current spreading layer, and forming a second electrode in a relatively low first gallium nitride layer. The method of claim 15, wherein the first gallium nitride layer, the active layer, and the second gallium nitride layer are grown by organometallic chemical vapor deposition (MOCVD). The method of claim 15, wherein the current spreading layer is formed by an electron beam deposition method. The method of claim 15, wherein the ohmic contact is performed by heat treatment. (a) sequentially growing a first gallium nitride layer, an active layer and a second gallium nitride layer on the substrate; (b) forming a current spreading layer over the second gallium nitride layer; (c) realizing an ohmic contact between the current spreading layer and the second gallium nitride layer; (d) forming a region of the second gallium nitride layer, the active layer and the first gallium nitride having a relatively small radius disk shape; (e) exposing a surface of the substrate to form a first gallium nitride layer having a relatively large radius disk shape; (f) forming a first electrode electrically connected to the first gallium nitride layer on the first gallium nitride layer; (g) depositing an insulating layer on the resultant of step (f); (h) removing the insulating layer of the region of the first electrode and the region where the p-electrode is to be formed; And (i) forming a second electrode electrically connected to the second gallium nitride layer exposed by step (h). 20. The method of claim 19, wherein the ratio of the relatively small radius and the relatively large radius is 4:10.

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