KR100798863B1 - GaN type light emitting diode device and method of manufacturing the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride based light emitting diode device and a method of manufacturing the same, comprising: a substrate, an n-type gallium nitride layer formed on the substrate, an active layer formed on a portion of the n-type gallium nitride layer, and formed on the active layer On the p-type gallium nitride layer, the p-type gallium nitride layer and the p-type electrode and the n-type electrode formed on the n-type gallium nitride layer, respectively, and the remaining region except the upper portion of the p-type electrode and the n-type electrode The present invention provides a gallium nitride-based light emitting diode device including a polymer layer formed on a surface thereof, the polymer layer having a predetermined pattern formed thereon, and the present invention also provides a method of manufacturing the gallium nitride-based light emitting diode device.

LED, light extraction efficiency, polymer layer, refractive index, imprinting, pattern, hemisphere

Description

GaN type light emitting diode device and method of manufacturing the same

1 is a view for explaining a light extraction efficiency reduction problem of a general gallium nitride-based LED device.

2 and 3 are cross-sectional views showing the structure of a gallium nitride-based LED device according to an embodiment of the present invention.

4 to 9 are cross-sectional views sequentially showing the method for manufacturing the gallium nitride-based LED device shown in FIG.

10 is a planar photograph showing an electrode periphery of the gallium nitride-based LED device according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110: substrate 120: buffer layer

130: n-type gallium nitride layer 140: active layer

150: p-type gallium nitride layer 160: p-type electrode

170: n-type electrode 180: polymer layer

180a: uncured polymer layer 190: phosphor

200: stamp

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based light emitting diode (LED) device and a method of manufacturing the same. More particularly, a gallium nitride-based LED device and a light emitting efficiency thereof are provided. It relates to a manufacturing method.

In general, gallium nitride-based semiconductors are actively employed in optical devices for generating short wavelength light such as blue or green as materials having a relatively high energy band gap (for example, about 3.4 eV in GaN semiconductors). As the gallium nitride-based 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. .

However, in the case of the conventional gallium nitride-based LED device using a gallium nitride-based semiconductor, the gallium nitride-based semiconductor has a high refractive index (n = 2.3 ~ 2.8) compared to the material surrounding the periphery, it is generated in the active layer There is a problem that the efficiency (hereinafter referred to as "extraction efficiency") that the photons are extracted to the outside of the LED device is reduced.

1 is a view for explaining the problem of reducing the light extraction efficiency of the gallium nitride-based LED device according to the prior art, when the problem is described in detail with reference to Figure 1, the photon generated in the active layer of the LED device is the refractive index of the air ( In order to escape into the air after passing through a gallium nitride (GaN) layer having a higher refractive index (N ₁ ) than N ₂ ), the incident angle (θ ₁ ) of the photons incident from the gallium nitride layer into the air is a critical angle (θ). _c ) must be less than

In this case, the critical angle θ _c when the escape angle θ _{2 at} which the photons escape into the air is 90 ° may be defined as θ _c = Sin ⁻¹ (N ₂ / N ₁ ), and in the gallium nitride layer The critical angle when light propagates into air with a refractive index of 1 is about 23.6 °.

If the incidence angle θ ₁ is greater than or equal to the critical angle θ _c , the photons are totally reflected at the interface between the gallium nitride layer and air, and then go back to the inside of the LED and disappear within the LED, whereby light extraction efficiency is very high. There is a problem that decreases.

In order to solve the above problem of reduction of light extraction efficiency, conventionally, by forming a periodic pattern or aperiodic roughness on the upper surface of the gallium nitride layer that emits light into the air, from the gallium nitride layer The incident angle θ ₁ of photons incident into the air was lowered below the critical angle θ _c .

The pattern or roughness of the surface of the gallium nitride layer is generally formed through an etching method using photolithography or a metal dot mask.

However, in the case of using the metal dot mask, the heat treatment temperature for forming the metal dot is very high (600 ° C. or higher) so that the Mg ions doped in the gallium nitride layer are deactivated so that the forward voltage Vf is increased and the luminance is increased. There is a problem that is lowered, and has the disadvantage that the removal of the etching by-products remaining on the surface of the etching surface during the dry etching is not easy.

In the case of using the photolithography, an etching mask can be formed relatively simply, but it is difficult to form a pattern having a nano size similar to the wavelength of light, and moreover, when the pattern is formed through dry etching, multiple quantum There has been a problem that plasma damage occurs in the active layer of a multi-quantum well (MQW) structure, and thus luminance may be lowered.

In addition, the pattern formation through dry etching as described above is not uniformly performed on the entire upper surface of the gallium nitride layer, and the effect of improving the light extraction efficiency obtained by applying the surface pattern in a conventional manner is sufficient. Not.

Therefore, there is a need in the art for a new way to maximize the effect of improving the light extraction efficiency.

Therefore, the present invention has been made to solve the above problems, an object of the present invention, by freely implementing the pattern shape on the surface of the LED device, without worrying about the change in electrical characteristics, brightness, etc., it is possible to increase the light extraction efficiency The present invention provides a gallium nitride-based light emitting diode device and a method of manufacturing the same.

Gallium nitride-based LED device according to the present invention for achieving the above object, the substrate; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer; A p-type electrode and an n-type electrode formed on the p-type gallium nitride layer and the n-type gallium nitride layer, respectively; And a polymer layer formed on a region other than the upper portion of the p-type electrode and the n-type electrode, and having a pattern having a predetermined shape on a surface thereof.

Here, the polymer layer is characterized in that it has a refractive index smaller than the refractive index of the material formed under the polymer layer.

The polymer layer has a sealing material formed thereon, and the polymer layer has a refractive index greater than that of the sealing material.

In addition, the polymer layer has a refractive index in the range between the refractive index of the material formed on the lower portion and the refractive index of the material formed on the upper portion, it characterized in that the upward direction of the light emitted from the active layer to collect. .

In addition, the pattern is characterized in that hemispherical form.

In addition, it is characterized in that it further comprises a phosphor dispersed in the polymer layer.

In addition, a method of manufacturing a gallium nitride-based LED device according to the present invention for achieving the above object comprises the steps of sequentially forming an n-type gallium nitride layer, an active layer, and a p-type gallium nitride layer on the substrate; Mesa-etching the p-type gallium nitride layer and a portion of the active layer to expose a portion of the n-type gallium nitride layer; Forming a p-type electrode and an n-type electrode on the p-type gallium nitride layer and the exposed n-type gallium nitride layer, respectively; And forming a polymer layer on the entire structure of the result, exposing the p-type electrode and the n-type electrode and having a predetermined pattern formed on a surface thereof.

Here, exposing the p-type electrode and the n-type electrode on the overall structure of the result, and forming a polymer layer having a predetermined shape pattern on the surface,

Forming a polymer layer on the entire structure formed up to the p-type electrode and the n-type electrode; Pressing a stamp on which a pattern of a predetermined form is formed on the polymer layer to transfer the pattern; Irradiating ultraviolet rays from the lower portion of the substrate to cure only the polymer layer formed on the remaining regions except for the upper portions of the p-type electrode and the n-type electrode; Separating the stamp from the polymer layer; And selectively removing the polymer layer not cured by the ultraviolet rays.

And, the polymer layer is characterized in that the ultraviolet curable material.

In addition, the pattern is characterized in that hemispherical form.

In addition, the polymer layer is characterized in that formed by mixing the phosphor.

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 gallium nitride based LED device and a method of manufacturing the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Embodiment of Structure of Gallium Nitride LED Device

First, a gallium nitride based LED device according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 and 3.

2 and 3 are cross-sectional views showing the structure of the gallium nitride-based LED device according to an embodiment of the present invention.

In the gallium nitride-based LED device according to the embodiment of the present invention, first, as shown in FIG. 2, the buffer layer 120, the n-type gallium nitride layer 130, the active layer 140, and the p on the substrate 110. The gallium nitride layer 150 is sequentially stacked.

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

The buffer layer 120 may be formed of GaN, which may be omitted.

The n-type or p-type gallium nitride layers 130 and 150 are formed of a GaN layer or a GaN / AlGaN layer doped with each conductivity type impurity, and the active layer 140 is formed of an MQW structure composed of InGaN / GaN layers.

The p-type gallium nitride layer 150 and a part of the active layer 140 are removed by mesa etching to expose a portion of the n-type gallium nitride layer 130 on the bottom surface.

On the other hand, the present invention may further include a current diffusion layer (not shown) made of ITO or the like on the p-type gallium nitride layer 150 to improve the current diffusion efficiency.

The p-type electrode 160 is formed on the p-type gallium nitride layer 150, and the n-type electrode 170 is formed on a predetermined portion of the n-type gallium nitride layer 130 exposed by the mesa etching. Here, the p-type electrode 160 and the n-type electrode 170 is preferably made of Cr / Au or the like so as to simultaneously serve as a reflection role and an electrode.

On the remaining regions other than the upper portions of the p-type electrode 160 and the n-type electrode 170, a polymer layer 180 having a predetermined pattern on the surface is formed. The pattern formed on the surface of the polymer layer 180 is preferably in the shape of a hemisphere, and in this form, the traveling direction of the light emitted from the active layer 140 (shown by the arrow in FIG. 2) is mostly straight toward the top of the LED device. To do it.

In particular, the polymer layer 180 may have a refractive index lower than that of a material formed under the polymer layer 180, such as the ITO, p-type gallium nitride layer 150, and n-type gallium nitride layer 130 as described above. It is desirable to have a small refractive index.

In addition, a sealing material (not shown) of an LED package such as epoxy or silicon resin may be formed on the polymer layer 180. In this case, the polymer layer 180 may be formed. Silver preferably has a larger refractive index than this sealing material.

That is, in the embodiment of the present invention, the polymer layer 180 is formed on the outermost side of the gallium nitride-based LED device, the polymer layer 180 is the refractive index of the material formed on the bottom and the refractive index of the material formed on the top By using a material having a refractive index in the range of between, it is possible to minimize the difference in the refractive index of the materials present on the path through which light exits, increasing the critical angle of the light emitted from the active layer 140 of the LED device You can increase the amount of light pointing upwards.

Here, the ITO, p-type and n-type gallium nitride layers 150 and 130 formed under the polymer layer 180 have a refractive index of about 2.0 to 2.8, and the sealing material formed on the polymer layer 180 is Since the refractive index is generally about 1.4, the polymer layer 180 is preferably made of a material having a refractive index in the range of about 1.4 to 2.0.

The gallium nitride-based LED device according to the present invention, as shown in Figure 3, may further include a phosphor 190 dispersed in the polymer layer 180. In this case, since the phosphor 190 can be uniformly distributed in the adjacent region of the LED element, the effect of improving the wavelength distribution of the LED element can be obtained.

In addition, when the phosphor 190 is included in the polymer layer 180, the refractive index of the polymer layer 180 may be increased by about 0.1 to about 0.2 by the phosphor 190. Accordingly, the difference in refractive index between the polymer layer 180 and the underlying material may be further reduced to further increase the light extraction effect.

The polymer layer 180 according to the present invention is formed on the outermost side of the gallium nitride-based LED device as described above, and serves as a protective film to protect the LED device from the external environment.

On the other hand, in the case of SiO _{2 that} is commonly used as a protective film of the gallium nitride-based LED device, the adhesion to the surface of the LED device is not excellent, it is vulnerable to moisture did not properly protect the LED device from the external environment, the present invention Since the polymer layer 180 constituting the LED device according to the present invention is mostly a hydrophobic material having no affinity for water, the polymer layer 180 may protect the LED device from external environments such as moisture, thereby contributing to improving the reliability of the device. have.

Embodiment of the manufacturing method of gallium nitride-based LED device

Hereinafter, a method of manufacturing a gallium nitride based LED device according to an embodiment of the present invention will be described in detail with reference to FIGS. 4 to 9.

4 to 9 are cross-sectional views sequentially illustrating a method of manufacturing the gallium nitride based LED device shown in FIG. 2.

First, as shown in FIG. 4, the buffer layer 120, the n-type gallium nitride layer 130, the active layer 140, and the p-type gallium nitride layer on the substrate 110 for growth of a gallium nitride based semiconductor material. 150 are formed in sequence. Here, the formation of the buffer layer 120 may be omitted.

Next, as shown in FIG. 5, a portion of the p-type gallium nitride layer 150 and the active layer 140 are mesa-etched to expose a portion of the n-type gallium nitride layer 130.

Next, as shown in FIG. 6, the p-type electrode 160 is formed on the p-type gallium nitride layer 150 which is not etched by the mesa etching process, and the n-type exposed by the mesa etching process. An n-type electrode 170 is formed on the gallium nitride layer 130. The p-type electrode 160 and the n-type electrode 170 may be formed using a metal such as Cr / Au.

Next, as shown in FIG. 7, the polymer layer 180 is formed on the entire structure formed up to the p-type electrode 160 and the n-type electrode 170. The polymer layer 180 may reduce the difference in refractive index between the internal and external materials of the LED device to improve the light extraction efficiency of the device, so that the refractive index of the material formed thereon and the refractive index of the material to be formed thereon may be improved. It is preferable that it is made of a material having a refractive index in the range. In addition, in order to improve the wavelength distribution of the LED device and to further increase the light extraction effect, the polymer layer 180 may be formed by mixing phosphors (reference numeral 190 of FIG. 3).

Next, the present invention forms a nano-scale fine pattern having a predetermined shape on the surface of the polymer layer 180 by using a nano imprinting method.

The nano-imprinting method is a method invented by Stephen Chou of Princeton University in the United States to prepare the required shape on the surface of a relatively strong material in advance, as if the coating on another material After dipping and patterning, or manufacturing a mold of a desired shape, a pattern is formed by applying a polymer material into the mold. The nano-imprinting method has the advantage of being able to manufacture a large-scale fine pattern of nano size, and the shape of the pattern is free.

A method of forming a pattern on the polymer layer 180 by using the nanoimprinting method is as follows.

First, as shown in FIG. 7, a stamp 200 prepared in advance to have a desired pattern of a desired shape is provided on the polymer layer 180. The polymer layer 180 is preferably an ultraviolet curable material cured by ultraviolet (UV) used in a subsequent process. The material of the stamp 200 is high in strength, such as silicon, metal, diamond, or quartz glass.

Next, as shown in FIG. 8, the stamp 200 is pressed toward the polymer layer 180 to transfer the pattern of the predetermined shape, for example, the hemispherical pattern, to the polymer layer 180.

In addition, ultraviolet rays (UV) are irradiated under the substrate 110 in order to cure the polymer layer 180 existing on portions where the p-type and n-type electrodes 160 and 170 are not formed. As described above, according to the present invention, by performing ultraviolet irradiation under the substrate 110, the p-type electrode 160 and the n-type electrode 170 of the upper part of the LED block some of the ultraviolet rays, and thus the electrodes 160 and 170. The portion of the polymer layer 180a formed on the upper portion thereof is not cured.

That is, the present invention applies the p-type and n-type electrodes to act as a mask to block ultraviolet rays (hereinafter referred to as "self-align masking method"), the p-type And only the polymer layer 180 formed on the remaining regions except for the upper portions of the n-type electrodes 160 and 170.

Thereafter, as shown in FIG. 9, the stamp 200 is separated from the polymer layer 180, and the polymer layer 180a which is not cured by the ultraviolet rays is selectively removed. Accordingly, the polymer layer 180 having the hemispherical pattern formed on the surface of the p-type electrode 160 and the n-type electrode 170 may be exposed. The exposed p-type electrode 160 and n-type electrode 170 are portions electrically connected to the outside to supply a current to the LED device.

10 is a planar photograph showing a p-type or n-type periphery of a gallium nitride-based LED device formed according to an embodiment of the present invention.

10, the polymer layer 180a formed on the p-type or n-type electrodes 160 and 170 was completely removed, and the hemispherical pattern was uniformly formed in other portions.

As such, the present invention frees the implementation of pattern shapes such as hemispheres on the surface of the LED device through the nano-imprinting method, so that the light extraction efficiency of the device without worrying about electrical characteristics change or luminance deterioration when forming the pattern There is an effect to increase.

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 to the disclosed embodiments, but 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 belong to the scope of the present invention.

As described above, according to the gallium nitride-based light emitting diode device according to the present invention and a method for manufacturing the same, a hemispherical pattern at the outermost part of the device by using a nanoimprinting method that is free to implement the shape of the pattern and relatively simple manufacturing process By forming this uniformly formed polymer layer, the light extraction efficiency of the LED element can be improved.

Here, the polymer layer may reduce the difference in refractive index between the internal and external materials of the LED device, thereby increasing the amount of light directed toward the upper part of the LED device, thereby further improving the brightness of the device.

In addition, since the polymer layer is a hydrophobic material having no affinity for water, there is an advantage that it can contribute to improve the reliability of the device by protecting the LED device from an external environment such as moisture.

Claims (11)

Board; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer; A p-type electrode and an n-type electrode formed on the p-type gallium nitride layer and the n-type gallium nitride layer, respectively; And A polymer layer formed on a region other than the upper portion of the p-type electrode and the n-type electrode and having a pattern of a predetermined shape on a surface thereof; Gallium nitride-based light emitting diode device comprising a. The method of claim 1, And the polymer layer has a refractive index smaller than that of a material formed under the polymer layer. The method of claim 1, The polymer layer, the sealing material is formed on the upper portion, and the gallium nitride-based light emitting diode device, characterized in that the polymer layer has a larger refractive index than the sealing material. The method according to any one of claims 1 to 3, The polymer layer has a refractive index in a range between the refractive index of the material formed on the lower portion and the refractive index of the material formed on the upper portion thereof, thereby collecting the upward direction of the light emitted from the active layer. Light emitting diode device. The method of claim 1, The pattern is hemispherical gallium nitride-based light emitting diode device, characterized in that. The method of claim 1, The gallium nitride-based light emitting diode device further comprises a phosphor dispersed in the polymer layer. A first step of sequentially forming an n-type gallium nitride layer, an active layer, and a p-type gallium nitride layer on the substrate; Mesa etching a portion of the p-type gallium nitride layer and the active layer to expose a portion of the n-type gallium nitride layer; Forming a p-type electrode and an n-type electrode on the p-type gallium nitride layer and the exposed n-type gallium nitride layer, respectively; And A fourth step of exposing the p-type electrode and the n-type electrode on an upper surface of the entire structure made by the first to third steps, and forming a polymer layer having a predetermined pattern on the surface; Method of manufacturing a gallium nitride-based light emitting diode device comprising a. The method of claim 7, wherein The fourth step is A step 4-1 of forming a polymer layer on the entire structure formed up to the p-type electrode and the n-type electrode; 4-2 step of transferring the pattern by pressing a stamp on which a pattern of a predetermined form is formed on the polymer layer; Irradiating ultraviolet rays from the lower portion of the substrate to cure only the polymer layer formed on the remaining regions except for the upper portions of the p-type electrode and the n-type electrode; 4-4, separating the stamp from the polymer layer; And 4-5 to selectively remove the polymer layer not cured by the ultraviolet ray; Method of manufacturing a gallium nitride-based light emitting diode device comprising a. The method of claim 8, The polymer layer is a method of manufacturing a gallium nitride-based light emitting diode device, characterized in that the ultraviolet curable material. The method according to claim 7 or 8, The pattern is a method of manufacturing a gallium nitride-based light emitting diode device, characterized in that hemispherical form. The method according to claim 7 or 8, The polymer layer is a method of manufacturing a gallium nitride-based light emitting diode device, characterized in that formed by mixing the phosphor.

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