KR101346802B1 - Light emitting diode with improved light extraction efficiency and method of fabricating the same - Google Patents

Abstract

Disclosed are a light emitting diode having improved light extraction efficiency and a method of manufacturing the same. The light emitting diode according to the present invention includes a light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer, a light extracting structure positioned on the light emitting structure and having a refractive index lower than that of the upper semiconductor layer. The extraction structure includes a layer of solidification material and has a nanopattern on top, and the light extraction structure has a lower refractive index in the upper region than in the lower region.
Compared with the lower region, the upper region may reduce total internal reflection of light in the device by the light extracting structure having a lower refractive index, thereby improving light extraction efficiency of the light emitting diode.
In addition, the light emitting diode manufacturing method according to the present invention provides a method for manufacturing a reliable light emitting diode in a simplified process including a light extraction structure comprising a layer of material solidified from a viscous material.

Description

LIGHT EMITTING DIODE WITH IMPROVED LIGHT EXTRACTION EFFICIENCY AND METHOD OF FABRICATING THE SAME

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode having improved light extraction efficiency by applying a light extraction structure and a method of manufacturing the same.

The white light source gallium nitride-based light emitting diode has the advantages of high energy conversion efficiency, long life, low voltage driving and no complicated driving circuit, so it replaces existing light sources such as incandescent lamp, fluorescent lamp and mercury lamp in the near future. We are looking forward to solid-state lighting. In order to use the gallium nitride-based light emitting diode as a new white light source to replace the existing light source, the gallium nitride-based light emitting diode must not only have excellent thermal stability but also be able to emit high output light at low power consumption. Is a very important issue.

The luminous efficiency of the light emitting diode is mainly determined by the internal quantum efficiency and the light extraction efficiency. In particular, the light extraction efficiency refers to the rate at which photons emitted from the active layer are emitted to the outside of the light emitting diode, that is, to the free space. When the light extraction efficiency is low, the number of photons exiting into the free space is small even though the internal quantum efficiency of the device is high. As a result, the efficiency of the light emitting diode as an actual light source is greatly reduced.

In the conventional light emitting diode, a GaN-based substrate (n _GaN = 2.4), a sapphire substrate (n _sapphire = 1.77), an ITO electrode (n _ITO = 1.9), and air (n _air = 1.0) in a path through which light escapes to free space Internal total reflection occurs due to the difference in refractive index at the interface between), which causes a considerable amount of light to be trapped, resulting in a significant drop in light extraction efficiency. In order to effectively reduce the total internal reflection phenomenon and increase the light extraction efficiency, the device may be etched to form a structure that is easy to emit light, change the structure of the LED chip, remove the reflector, or process the surface of the LED chip. Several technologies are being researched and developed.

Specifically, PSS (Patterned Sapphire Substrate) surface processing technology, p-GaN roughness growth technology, photonic band gap (PBG) technology, surface processing technology using laser, surface plasmon formation technology, surface using gold particle array Processing technology is researched, developed and used.

However, the above-mentioned techniques are difficult to deform the surface shape because the process method is very complicated and expensive equipment is used to increase the process cost, and the p-type semiconductor layer is thin and its electrical conductivity due to doping is relatively low. There is this. In addition, processes using high energy may damage the light emitting diode device, which may lower the reliability of the light emitting diode device.

The problem to be solved by the present invention is to provide a light emitting diode having a light extraction structure and a method of manufacturing the same so that the light extraction efficiency is improved.

Another object of the present invention is to provide a method of manufacturing a light emitting diode having improved light extraction efficiency and a simple and reliable process.

In one embodiment, a light emitting diode includes: a light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer; And a light extracting structure positioned on the light emitting structure and having a refractive index lower than that of the upper semiconductor layer, wherein the light extracting structure includes a solidified material layer and has a nanopattern thereon. The upper region has a lower refractive index than the lower region.

The light extraction structure having a nano pattern on the top and the light extraction structure having a lower refractive index than the bottom area can emit light while reducing total internal reflection, thereby improving light extraction efficiency of the light emitting diode.

The light extracting structure includes an upper material layer having the nanopattern; And a lower material layer interposed between the upper material layer and the upper semiconductor layer, wherein the lower material layer may include at least one solidification material layer.

In addition, the light extraction structure may be continuously reduced in refractive index from the bottom to the top.

In addition, the light emitting diode according to an embodiment of the present invention may further include a transparent electrode positioned between the semiconductor layer and the light extraction structure, the transparent electrode is formed of any one or a mixture of ITO, ZnO Can be.

The light extracting structure may include any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and SOG, or a mixture thereof.

The at least one solid material layer may include a first solid material layer disposed between the upper material layer and the upper semiconductor layer; And a second solidifying material layer positioned between the first solidifying material layer and the upper material layer, wherein the first solidifying material layer is formed of SOG, and the second solidifying material layer may be formed of ITO. .

In addition, the light extracting structure may sequentially decrease the refractive index from the lowermost solidified material layer to the upper material layer.

Each solidifying material layer in the lower material layer has an optical thickness of 0.5 times the emission wavelength.

The nanopattern may include a horn shape, a hemispherical shape, or a cylinder shape, and the nanopattern may have a honeycomb structure.

The light emitting structure may have a mesa structure in which a portion of the lower semiconductor layer is exposed, and may further include a first electrode connected to the transparent electrode and a second electrode connected to the lower semiconductor layer, and the lower material layer May cover the exposed lower semiconductor layer.

The light emitting diode manufacturing method according to an embodiment of the present invention, forming a light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer, and has a lower refractive index than the upper semiconductor layer on the light emitting structure Forming a light extracting structure having a nanopattern, wherein forming the light extracting structure includes forming a solidified material layer on the light emitting structure, the light extracting structure having a top region more than a bottom region; It can have a low refractive index.

Forming the light extracting structure may include forming a solidified material layer to form the light extracting structure through a simplified and highly reliable process, thereby improving light extraction efficiency.

The forming of the light extracting structure may include forming a lower material layer including at least one solidifying material layer on the light emitting structure, and forming an upper material layer having the nanopattern on the lower material layer. It may include.

The forming of the light extracting structure may include applying a preliminary material mixture in which at least two preliminary materials having different densities are mixed on the light emitting structure, and converting the preliminary material mixture into the light emitting structure such that the preliminary materials are arranged according to the density. Retaining in the phase and solidifying the preliminary material mixture to form a solid material layer.

Before forming the light extracting structure, the method may further include forming a transparent electrode on the light emitting structure, and etching a portion of the upper semiconductor layer and the active layer to expose a portion of the lower semiconductor layer. It may include.

The method may further include forming a first electrode and a second electrode electrically connected to the lower semiconductor layer and the upper semiconductor layer, and forming the first electrode and the second electrode may be a partial region of the light extracting structure. Etching may include exposing a portion of the upper semiconductor layer and the lower semiconductor layer.

The forming of the solid material layer may include applying a preliminary material to the light emitting structure by any one of spin coating, bar coating, and a doctor blade, and solidifying the preliminary material. The preliminary material may comprise any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and SOG or mixtures thereof.

Each layer of solidification material in the lower material layer may have an optical thickness that is 0.5 times the emission wavelength.

In addition, the lower material layer includes a first solid material layer and a second solid material layer positioned on the first solid material layer, wherein the first solid material layer is formed of SOG and the second solid material layer May be formed of ITO.

The forming of the light extracting structure may include coating a preliminary material on the light emitting structure, transferring a pattern of a nano imprint mold to the preliminary material, and solidifying the preliminary material. Transferring the pattern of the mold may pressurize the nanoimprint mold to a pressure of 1-3 bar against the preliminary material.

As described above, the light emitting diode according to the present invention includes a light extracting structure having a lower refractive index than that of the GaN-based semiconductor layer and at the same time having a lower refractive index than that of the lower region, thereby reducing total internal reflection to improve light extraction efficiency. It works.

In addition, by forming the light extraction structure using the solidified material it is possible to simplify the manufacturing process of the light emitting diode and to improve the reliability of the light emitting diode.

1 is a cross-sectional view for describing a light emitting diode according to an embodiment of the present invention.
2 is a cross-sectional view for describing a light emitting diode according to another embodiment of the present invention.
3 is a cross-sectional view for describing a light emitting diode according to another embodiment of the present invention.
4 to 8 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.
9 is a cross-sectional view illustrating a method of manufacturing a light emitting diode according to another embodiment of the present invention.
10 to 12 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to another embodiment of the present invention.
FIG. 13 is a graph illustrating light extraction efficiency between light emitting diodes and light emitting diodes to be compared according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can sufficiently convey the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. It will also be appreciated that where parts of a layer, film, area, plate, etc. are described as being "on top" or "on" another part, And includes another portion between the other portions. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, the light emitting diode includes a substrate 17, a light emitting structure 10, and a light extracting structure 20. Furthermore, the light emitting diode may further include a first electrode 31, a second electrode 33, and a transparent electrode 19.

The substrate 17 is not particularly limited, and may be, for example, a sapphire substrate, a SiC substrate, a spinel substrate, a Si substrate, or a GaN based substrate. The substrate 17 may be a growth substrate. In addition, the upper surface may have a predetermined pattern, such as a patterned sapphire substrate (PSS).

The light emitting structure 10 is positioned on the substrate 17. The light emitting structure 10 includes a lower semiconductor layer 11, an active layer 13, and an upper semiconductor layer 15, and the active layer 13 is disposed between the lower semiconductor layer 11 and the upper semiconductor layer 15. Located in Here, the upper and lower semiconductor layers 11 and 15 may be different conductive semiconductors, for example, the upper semiconductor layer 15 may be p-type, and the lower semiconductor layer 11 may be n-type or vice versa. . In addition, a buffer layer may be interposed between the substrate 17 and the light emitting structure 10.

The lower semiconductor layer 11, the active layer 13, and the upper semiconductor layer 15 may be formed of a GaN-based compound semiconductor material ((Al, Ga, In) N). The active layer 13 may be formed of a GaN-based compound whose composition element and composition ratio are adjusted to emit light of a required wavelength, for example, to emit blue light or ultraviolet light. The lower semiconductor layer 11 and the upper semiconductor layer 15 may each be a single layer or multiple layers. For example, the lower semiconductor layer 11 and / or the upper semiconductor layer 15 may include a contact layer and a cladding layer, and may also include a superlattice layer. In addition, the active layer 13 may be a single quantum well structure or a multi quantum well structure (MQW).

The semiconductor layers 11, 13, and 15 of the light emitting structure 10 may be formed using a metal organic chemical vapor deposition (MOCVD), a molecular beam epitaxy (MBE), or a hybrid vapor phase epitaxy (HVPE) technology. By using a photo process and an etching process, a portion of the lower semiconductor layer 11 may be patterned to be exposed. The active layer 13 and the upper semiconductor layer 15 may be patterned to have a mesa structure.

The transparent electrode 19 may be positioned on the upper semiconductor layer 15 and may be positioned below the light extracting structure 20. The transparent electrode may be formed of any one of ITO, IZO, or ZnO, or may be formed of a mixture thereof. In addition, the transparent electrode 19 may have a thickness of 100 ~ 500nm.

The light extracting structure 20 is located on the light emitting structure 10. The light extracting structure 20 may include a first solidified material layer 21, a second solidified material layer 23, and an upper material layer 25. In addition, the upper material layer 25 may include a nanopattern 25a on the top surface. Although not shown, the light extracting structure 20 may include fewer layers, or may include more layers.

Each layer of the light extracting structure 20 may be formed by solidifying a preliminary material having a viscosity that may be coated, such as a liquid material or a sol material. For example, it may be formed of any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and spin-on-glass (SOG) or a mixture thereof. Specifically, the first solidified material layer 21 may be formed of SOG, the second solidified material layer 23 may be formed of ITO sol-gel, and the upper material layer 25 may be formed of PUA ( Polyurethane acrylate) may be formed.

Each layer of the light extracting structure 20 may be formed by applying the viscous preliminary material by spin coating, bar coating, doctor blade, or the like, and then solidifying by thermosetting or ultraviolet curing. have. The first solidified material layer 21 and the second solidified material layer 23 have an optical thickness corresponding to 0.5 times the wavelength of light emitted from the active layer 13 so as to cause reinforcement interference and improve transmittance therein. It may have an optical thickness, but is not limited thereto. The first solidified material layer 21 may have a thicker layer formed on the lower semiconductor layer 11 than the thickness of the layer formed on the upper semiconductor layer 15. In this case, the first solid material layer 21 may cover the mesa sidewall of the light emitting structure 10.

The light extracting structure 20 has a refractive index lower than that of the light emitting structure 10. In addition, the light extracting structure 20 may have a lower refractive index than the transparent electrode 19. In addition, the light extracting structure 20 may have a lower refractive index in the upper region than in the lower region, and the change in the refractive index may be continuous, or may be sequentially intermittent. For example, the first solidified material layer 21 may be formed of SOG having a refractive index of 1.75, and the second solidified material layer 23 may be formed of ITO having a refractive index of 1.6 formed using ITO sol-gel. The upper material layer 25 may be formed of PUA having a refractive index of 1.45. Accordingly, the difference in refractive index between the material layers 21, 23, and 25 of the light extracting structure 20 is reduced, so that total reflection generated at the interface when light is incident on the medium having a small refractive index from the medium having a large refractive index The phenomenon can be effectively prevented, so that the light extraction efficiency can be improved.

On the other hand, the light extraction structure 20 has a nano-pattern 25a on the top. By forming the nanopattern 25a on the upper surface of the light emitting diode, the emitted light may be kept from the critical angle at the interface, thereby preventing total internal reflection and improving light extraction efficiency.

The nanopattern 25a may be formed using a nanoimprinting process, and may have a horn shape, a hemispherical shape, a cylinder shape, or the like. For example, the nanopattern 25a shown in FIG. 1 has a cone shape having a bottom diameter of 400 nm, a height of 200 nm, and a gap of 400 nm, and these cones are arranged in a honeycomb structure. The nanoimprinting process for forming the nanopattern 25a will be described in detail later.

The light emitting diode includes a first electrode 31 positioned on the upper semiconductor layer 15 and a second electrode 33 positioned on an area where the lower semiconductor layer 11 is exposed. Here, the first electrode 31 is electrically connected to the upper semiconductor layer 15, and the second electrode 33 is electrically connected to the lower semiconductor layer 11.

The electrodes 31 and 33 may expose the transparent electrode 19, the upper semiconductor layer 15, and the lower semiconductor layer 11 by using a photolithography and etching process on the light extracting structure 20. Can be formed on the exposed area. In addition, the electrodes 31 and 33 may protrude from the light extracting structure 20.

2 is a cross-sectional view for describing a light emitting diode according to another exemplary embodiment of the present invention.

Referring to FIG. 2, the light emitting diode includes a substrate 47, a light emitting structure 40, and a light extracting structure 50. Furthermore, the light emitting diode may further include an electrode 61 and a bonding layer 49. The light emitting diode shown in FIG. 2 is generally similar to the light emitting diode according to the exemplary embodiment of the present invention described with reference to FIG. 1, except that the light emitting diode is a light emitting diode having a vertical structure.

The substrate 47 may be a conductive substrate such as a metal substrate or a semiconductor substrate as a support substrate, but is not limited thereto and may be an insulating substrate. The substrate 47 is, for example, a substrate formed of sapphire, Si, GaAs, GaP, AlGaINP, Ge, SiSe, GaN, AlInGaN or InGaN, but Al, Zn, Ag, W, Ti, Ni, Au, Mo, Pt It may be a substrate containing a single metal of Pd, Cu, Cr or Fe or a stack or alloy thereof.

A bonding layer 49 may be located between the substrate 47 and the light emitting structure 40. In addition, a reflective layer (not shown) and a diffusion barrier layer (not shown) may be further interposed between the bonding layer 49 and the light emitting structure 40, and the reflective layer reflects light emitted from the active layer 43 and downwards. The diffusion barrier layer prevents the diffusion of metal elements from the bonding layer 49 into the reflective layer or the reflection material of the reflective layer into the bonding layer 49 to maintain the reflectivity of the reflective layer.

The light emitting structure 40 is positioned on the bonding layer 49. The light emitting structure 40 includes a lower semiconductor layer 41, an active layer 43, and an upper semiconductor layer 45, and the active layer 43 is disposed between the lower semiconductor layer 41 and the upper semiconductor layer 45. Located in Here, the upper and lower semiconductor layers 11 and 15 may be different conductive semiconductors, for example, the upper semiconductor layer 15 may be n-type, and the lower semiconductor layer 11 may be p-type or vice versa. .

The lower semiconductor layer 41, the active layer 43, and the upper semiconductor layer 45 may be formed of GaN-based compound semiconductor material ((Al, Ga, In) N). The active layer 43 may be formed of a GaN-based compound whose composition element and composition ratio are adjusted to emit light of a required wavelength, for example, to emit blue light or ultraviolet light. The lower semiconductor layer 41 and the upper semiconductor layer 45 may each be a single layer or multiple layers. For example, the lower semiconductor layer 41 and / or the upper semiconductor layer 45 may include a contact layer and a cladding layer, and may also include a superlattice layer. In addition, the active layer 13 may be a single quantum well structure or a multi quantum well structure (MQW).

The light extracting structure 50 is located on the light emitting structure 40. The light extracting structure 50 may include a first solid material layer 51, a second solid material layer 53, and an upper material layer 55. In addition, the upper material layer 55 may include a nanopattern 55a on the top surface. Although not shown in FIG. 2, the light extraction structure 20 may include fewer layers, or may include more layers.

The light extraction structure 50 and the nanopattern 55a are generally similar to the light extraction structure 20 and the nanopattern 25a described with reference to FIG. 1, and thus, detailed description thereof will be omitted.

The light emitting diode includes an electrode 61 positioned on the upper semiconductor layer 45. The electrode 61 is electrically connected to the upper semiconductor layer 45.

The electrode 61 may be formed on the exposed region by allowing the light extracting structure 50 to expose the upper semiconductor layer 45 by using a photolithography and etching process. In addition, the electrode 61 may be formed to protrude from the light extracting structure 50.

Meanwhile, when the substrate 47 is a conductive substrate, the substrate 47 may be used as an electrode, or a metal electrode may be added below the substrate 47. Alternatively, the substrate 47 may be added. In the case of the insulating substrate, an electrode electrically connected to the lower semiconductor layer 41 may be further formed above or below the substrate 47.

3 is a cross-sectional view for describing a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 3, the light emitting diode includes a substrate 17, a light emitting structure 10, and a light extracting structure 71. Furthermore, the light emitting diode may further include a first electrode 31, a second electrode 33, and a transparent electrode 19. The light emitting diode described with reference to FIG. 3 is generally similar to the light emitting diode described with reference to FIG. 1 except that there is a difference in the light extraction structure 71. Hereinafter, the light extraction structure 71 will be described.

The light extracting structure 71 is positioned on the light emitting structure 10 and includes a nanopattern 71a on an upper surface thereof.

The light extracting structure 71 has a refractive index lower than that of the light emitting structure 10. In addition, the light extracting structure 71 may have a refractive index lower than that of the transparent electrode 19. In addition, the light extracting structure 71 may have a lower refractive index in the upper region than in the lower region, and the change in the refractive index may be continuous. For example, as shown in FIG. 3, the refractive index may be differently formed along the vertical direction of the light extracting structure 71 to form a refractive index grading layer.

The light extracting structure 71 may be formed by solidifying from a preliminary material having a viscosity that may be coated, such as a liquid material or a sol material. For example, it may be formed of any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and spin-on-glass (SOG) or a mixture thereof. In addition, the light extracting structure 71 may be formed by applying the preliminary material by a method such as spin coating, bar coating, and doctor blade, and then solidifying by a method such as thermosetting or ultraviolet curing. For example, as shown in FIG. 3, two or more of the above preliminary materials are mixed to prepare a preliminary material mixture such that the refractive index of the light extracting structure 71 is continuously changed, and then applied onto the light emitting structure 10. If kept after, it is arranged up and down according to the density. That is, the higher density material is located in the lower region, the lower density material is located in the relatively upper region.

Thereafter, when the preliminary material mixture is solidified by a method such as thermosetting or ultraviolet curing, a light extraction structure 71 is formed in which the density continuously changes in the vertical direction. In general, since a material having a higher density has a larger refractive index than a material having a lower density, the light extracting structure 71 has a lower refractive index than the lower region, and the refractive index continuously changes at the same time. It may be formed of a refractive index grading layer. As a result, the refractive index of the light extracting structure 71 is lowered outward from the light emitting structure 10, the difference in refractive index at the interface between the light emitting diode and the free space is reduced, and the total reflection phenomenon of the light can be prevented. The efficiency can be improved.

The nanopattern 71a is generally similar to that described with reference to FIG. 1, and will be described in detail later as described above.

In the present embodiment, although the light extraction structure 71 is formed and described on the light emitting diode of the horizontal structure, it can be applied to the light emitting diode of the vertical structure as shown in FIG. In other words, a refractive index grading layer in which the refractive index continuously decreases, such as the light extraction structure 71 according to the present embodiment, may be used instead of the light extraction structure 50 of FIG. 2.

Incidentally, in the present embodiment, it will be described that all of the light extracting structure 71 is formed of the refractive index grading layer, but a part of the light extracting structure 71 may be formed of the refractive index grading layer. For example, a refractive index grading layer may be formed on the light emitting structure 10, and an upper material layer having a nanopattern as described with reference to FIG. 1 may be formed thereon.

Hereinafter, a method of manufacturing a light emitting diode according to embodiments of the present invention will be described in detail with reference to FIGS. 4 to 12.

4 to 8 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

First, referring to FIG. 4, an epitaxial layer including the lower semiconductor layer 11, the active layer 13, and the upper semiconductor layer 15 is grown on the substrate 17 to form the light emitting structure 10. The epi layers 11, 13, 15 may be formed using a technique such as MOCVD, MBE, or HVPE. A buffer layer (not shown) may be formed before the lower semiconductor layer 11 is grown. The lower semiconductor layer 11 and the upper semiconductor layer 15 have different conductivity types, for example, the lower semiconductor layer 11 is an n-type conductive semiconductor layer and the upper semiconductor layer 15 is a p-type conductive semiconductor. It may be a layer or vice versa.

Thereafter, the light emitting structure 10 is mesa-etched to expose a portion of the lower semiconductor layer 11. The light emitting structure 10 may be patterned through a photolithography and an etching process.

Subsequently, a transparent electrode 19 may be formed on the mesa of the light emitting structure 10, that is, on the upper semiconductor layer 15. The transparent electrode 19 may be formed through e-beam evaporation, sputtering, or thermal deposition. In this case, the transparent electrode 19 may be formed of any one or a mixture thereof selected from ITO, ZnO, and IZO, and may be formed to have a thickness of about 100 to 500 nm. The transparent electrode 19 may be in ohmic contact with the upper semiconductor layer 15.

The transparent electrode 19 may be formed using, for example, a lift off process. In the present embodiment, the transparent electrode 19 is formed after mesa etching, but the transparent electrode 19 may be formed first before the mesa etching.

Referring to FIG. 5, a first solidified material layer 21 and a second solidified material layer 23 are formed on the light emitting structure 10. As illustrated in FIG. 5, two solid material layers 21 and 23 are formed in the present exemplary embodiment, but the present invention is not limited thereto, and fewer or more solid material layers may be formed.

The first solidification material layer 21 and the second solidification material layer 23 may be formed by solidification from a preliminary material having a viscosity such as a liquid material or a sol material. For example, the preliminary material may be formed of any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and spin-on-glass (SOG) or a mixture thereof.

Meanwhile, in the method of forming the solidified material layers 21 and 23, the preliminary material is coated on the light emitting structure 10. At this time, the viscous material may be applied by spin coating, bar coating, and doctor blade methods. The preliminary material may be thicker on the lower semiconductor layer 11 than the thickness applied on the upper semiconductor layer 15, and the preliminary material may cover the mesa sidewall of the light emitting structure 10. After applying the preliminary material, the solidified material layers 21 and 23 may be formed by solidification by a thermosetting or ultraviolet curing method. The first solidified material layer 21 and the second solidified material layer 23 have an optical thickness corresponding to 0.5 times the wavelength of light emitted from the active layer 13 so as to cause reinforcement interference and improve transmittance therein. It may be formed with an optical thickness, but is not limited thereto. As described above, applying the preliminary material by a method such as spin coating, bar coating, and doctor blade and then solidifying to form a layer of the solid material can easily form each layer through a simplified process, and each layer The thickness can be easily adjusted to increase the reliability.

Referring back to FIG. 5, the refractive indices of the first solidified material layer 21 and the second solidified material layer 23 may be formed to be lower than the refractive index of the light emitting structure 10. In addition, the refractive index of the second solid material layer 23 may be lower than the refractive index of the first solid material layer 21. For example, the first solidified material layer 21 may be formed of SOG having a refractive index of 1.75, and the second solidified material layer 23 may be formed of ITO sol-gel having a refractive index of 1.6.

As shown in FIG. 5, the change in the refractive index of each of the solidified material layers 21 and 23 may be intermittent, but is not limited thereto. The refractive index grading layer may continuously change the refractive index.

Referring to FIG. 6, in order to form the upper material layer 22 on the second solidified material layer 23, a preliminary material 22 having a viscosity such as a liquid material or a sol material is added to the second solidified material layer. It is apply | coated on (23). In this case, the preliminary material 22 may be any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and spin-on-glass (SOG), or a mixture thereof.

Next, referring to FIG. 7, the nanoimprint mold 80 is corresponded to the preliminary material 22 applied on the second solid material layer 23 to form the nanopattern 25a and at the same time, the preliminary material. The 22 is solidified to form the upper material layer 25. In more detail, the nanoimprint mold 80 may be pressed in correspondence with the preliminary material 22 and may be solidified by a method of thermosetting or ultraviolet curing. Alternatively, the nanoimprint mold 80 may be corresponded to the preliminary material 22 applied on the second solid material layer 23 to form a nanopattern 25a, and then the preliminary material 22 may be solidified to form an upper portion. The material layer 25 may be formed.

Thereafter, the nanoimprint mold 80 is separated from the light extraction structure 20. Before the nanoimprint mold 80 corresponds to the preliminary material 22, the method may further include performing an anti-adhesion treatment on a corresponding surface.

The upper material layer 25 may be formed to have a refractive index lower than that of the first solidified material layer 21 and the second solidified material layer 23. For example, the first solidified material layer 21 may be formed of SOG having a refractive index of 1.75, the second solidified material layer 23 may be formed of an ITO sol-gel having a refractive index of 1.6, and an upper material layer 25 ) May be formed of PUA having a refractive index of 1.45. Accordingly, the difference in refractive index between the material layers 21, 23, and 25 of the light extracting structure 20 is reduced, so that total reflection generated at the interface when light is incident on the medium having a small refractive index from the medium having a large refractive index The phenomenon can be effectively prevented, so that the light extraction efficiency can be improved.

On the other hand, the nano imprint mold 80 may have a nano pattern of various shapes, for example, may have a horn shape, hemispherical shape, or a cylinder shape. In addition, the nano-pattern of the nano-imprint mold 80 may have a honeycomb structure of each shape. The nanopattern 25a is formed on the light extracting structure 20 in a shape corresponding to that of the nanoimprint mold 80.

Since the nanopattern 25a is formed on the light extracting structure 20, total internal reflection may be prevented, thereby improving light extraction efficiency. In addition, when the nano-pattern is formed using the nano-imprinting process, the nano-pattern can be formed by a simple process, and the nano-pattern can be easily formed on a large-area substrate. The nanopattern can be formed without using a conventional patterning process that can damage the light emitting diode while easily forming the nanopattern, thereby forming the nanopattern in a simplified and highly reliable process.

Referring to FIG. 8, a portion of the light extracting structure 20 is patterned using a photolithography and an etching process. The exposed regions 32 and 34 may be formed through patterning, and the transparent electrode 19 and the lower semiconductor layer 11 may be exposed through the exposed regions 32 and 34. The light extraction structure 20 may be patterned using a dry and / or wet etching process. A wet etching process is preferred in order not to damage the light emitting structure 10. In addition, a portion of the light extracting structure 20 may be etched using dry etching, and then the transparent electrode 19 and the lower semiconductor layer 11 may be exposed using a wet etching process. For example, the upper material layer 25 formed of PUA may etch a partial region using an oxygen plasma, and the second solid material layer 23 formed of ITO may etch a partial region using hydrochloric acid. The first solidified material layer 21 formed of SOG may etch a portion of the first solidified material layer 21 using a hydrogen fluoride solution.

The first electrode 31 and the second electrode 33 are formed in the exposed regions 32 and 34. The electrodes 31 and 33 may protrude from the light extracting structure 20. The first electrode 31 and the second electrode 33 are formed to provide a light emitting diode as shown in FIG.

9 is a cross-sectional view for describing a light emitting diode manufacturing method according to another exemplary embodiment of the present invention.

Referring to FIG. 9, in the light emitting diode manufacturing method according to the present embodiment, forming the light extracting structure 50 on the light emitting structure 40 is generally similar to that described with reference to FIGS. 4 to 8. However, there is a difference in that the light emitting structure 40 has a vertical structure, and the exposed area 62 of the light extracting structure 50 is formed differently.

That is, the light emitting structure 40 is first attached to the support substrate 47 and the growth substrate is removed as in the conventional vertical structure light emitting diode manufacturing method. Thereafter, as described with reference to FIGS. 4 to 8, the light extracting structure 50 is formed on the light emitting structure 40, and a portion of the light extracting structure 50 is removed to remove the light emitting structure 40. Some areas are exposed. Thereafter, an electrode may be formed on a portion of the exposed light emitting structure 40 to provide the light emitting diode of FIG. 2.

10 to 12 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 10, as described with reference to FIG. 4, a substrate 17, a light emitting structure 10, and a transparent electrode 19 are formed. Thereafter, a premixed material layer 72 having a viscosity such as a liquid material or a sol material is formed on the light emitting structure 10.

The premix material layer 72 may be formed of a mixture thereof selected from nanoimprint resin, photoresist, polyimide, sol-gel, and spin-on-glass (SOG). May be a preliminary material mixture having a viscosity of at least two different density materials mixed.

The preliminary mixed material layer 72 may be formed by applying a viscous preliminary material mixture by spin coating, bar coating, or a doctor blade.

Thereafter, the premixed material layer 72 is maintained without solidifying for a predetermined time. Preferably it can be maintained for 15 to 30 hours. After a predetermined time, as shown in FIG. 11, the premixed material layer 72 is arranged according to the density of the respective materials in the mixture in the vertical direction, so that the lower region of the premixed material layer 72 The relatively dense material is located, and the upper region is located a relatively low density material. In general, the higher the density, the higher the refractive index of the material. Thus, the premixed material layer 72 may be formed of a refractive index grading layer 74 having a viscosity.

Referring to FIG. 12, the nanopattern 71a is formed on the refractive index grading layer 74 having the viscosity and simultaneously solidified to form the light extracting structure 71. In addition, the nanopattern 71a may be formed first, and the refractive index grading layer 74 may be solidified, or vice versa.

The solidification of the viscous grading index layer 74 is generally similar to that of the upper material layer 25 as described with reference to FIGS.

In addition, since forming the nanopattern 71a is substantially similar to forming the nanopattern 25a as described with reference to FIGS. 7 to 8, detailed description thereof will be omitted.

The light extracting structure 71 may be formed of a refractive index grading layer in which the upper region has a lower refractive index than the lower region and simultaneously the refractive index is continuously changed. Accordingly, the refractive index of the light extracting structure 71 is lowered outwardly from the light emitting structure 10, and the difference in refractive index at the interface between the light emitting diode and the free space is reduced, thereby preventing total reflection of light, thereby preventing light extraction efficiency. Can be improved.

Subsequently, a portion of the light extracting structure 71 may be patterned using photo and etching processes to form exposed regions 32 and 34, and the first electrode 31 may be formed in the exposed regions 32 and 34. And a second electrode 33. When the electrodes 31 and 33 are formed, a light emitting diode as described with reference to FIG. 3 is completed.

In the present embodiment, the light extraction structure 71 is formed on the horizontal light emitting structure, but the light extraction structure 71 may be formed on the light emitting structure of the vertical structure.

FIG. 13 is a graph illustrating light extraction efficiency between light emitting diodes and light emitting diodes to be compared according to an embodiment of the present invention.

Comparative Example 1 shows the light extraction efficiency of the light emitting diode which forms a transparent electrode on the light emitting structure and emits light through the transparent electrode without forming a light extraction structure, and Comparative Example 2 has a nano pattern on the transparent electrode The light extraction efficiency of the light emitting diode in which the upper material layer is formed is shown. On the other hand, the experimental example is a light emitting diode having a light extracting structure having a first solidified material layer, a second solidified material layer, and an upper material layer having a nano-pattern on the light emitting structure and the transparent electrode as shown in FIG. Light extraction efficiency. Here, the light extraction efficiency of Comparative Example 2 and Experimental Example is shown as a relative value based on the light extraction efficiency of Comparative Example 1.

Referring to FIG. 13, when the light extraction degree of Comparative Example 1 is 1, the light extraction efficiency of Comparative Example 2 is 1.32, and the light extraction ratio of Experimental Example is 1.49. That is, since the light extraction structure is formed on the light emitting structure, the light extraction efficiency of 49% is increased. Through this, it can be seen that the light emitting diode according to an embodiment of the present invention shows more improved light extraction efficiency than when only the upper material layer having the nanopattern is formed.

In the above, various embodiments and features of the present invention have been described, but the present invention is not limited to the various embodiments and features described above, and the scope does not depart from the technical spirit of the claims of the present invention. Many variations and modifications are possible.

Claims (27)

A light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer;
A light extraction structure positioned on the light emitting structure and having a refractive index lower than that of the upper semiconductor layer;
The light extracting structure includes a solid material layer and has a nanopattern on the top,
The light extracting structure has a lower refractive index in the upper region than in the lower region,
The light extraction structure,
An upper material layer having the nanopattern; And
A lower material layer interposed between the upper material layer and the upper semiconductor layer,
The lower material layer comprises at least one layer of solidifying material,
The at least one layer of solidified material,
A first solidified material layer positioned between the upper material layer and the upper semiconductor layer; And
A second solidified material layer positioned between the first solidified material layer and the upper material layer;
The first solidified material layer is formed of SOG,
The second solid material layer is formed of ITO. delete A light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer;
A light extraction structure positioned on the light emitting structure and having a refractive index lower than that of the upper semiconductor layer;
The light extracting structure includes a solid material layer and has a nanopattern on the top,
The light extracting structure has a lower refractive index in the upper region than in the lower region,
The light extracting structure is a light emitting diode in which the refractive index is continuously reduced from the bottom to the top. The method according to claim 1 or 3,
The light emitting diode further comprises a transparent electrode positioned between the semiconductor layer and the light extraction structure. The method of claim 4,
The transparent electrode is a light emitting diode formed of any one or a mixture of ITO, IZO, and ZnO. The method according to claim 3,
The light extracting structure includes a light emitting diode including any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and SOG or a mixture thereof. delete delete delete The method according to claim 1 or 3,
The nanopattern may include a horn shape, a hemispherical shape, or a cylinder shape. The method of claim 10,
The nanopattern is a light emitting diode having a honeycomb structure. The method of claim 4,
The light emitting diode is a light emitting diode having a mesa structure in which a portion of the lower semiconductor layer is exposed. The method of claim 12,
The light emitting diode further comprises a first electrode connected to the transparent electrode and a second electrode connected to the lower semiconductor layer. The method according to claim 13,
The lower material layer covers the exposed lower semiconductor layer. Forming a light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer,
Forming a light extraction structure having a low refractive index compared to the upper semiconductor layer and having a nano-pattern on the light emitting structure,
Forming the light extracting structure includes forming a solidified material layer on the light emitting structure,
The light extracting structure has a lower refractive index in the upper region than in the lower region,
Forming the light extraction structure,
Forming a lower material layer including at least one solidifying material layer on the light emitting structure,
Forming an upper material layer having the nanopattern on the lower material layer,
The lower material layer includes a first solid material layer and a second solid material layer positioned on the first solid material layer,
Wherein the first solid material layer is formed of SOG, and the second solid material layer is formed of ITO. delete Forming a light emitting structure including a lower semiconductor layer, an active layer, and an upper semiconductor layer,
Forming a light extraction structure having a low refractive index compared to the upper semiconductor layer and having a nano-pattern on the light emitting structure,
Forming the light extracting structure includes forming a solidified material layer on the light emitting structure,
The light extracting structure has a lower refractive index in the upper region than in the lower region,
Forming the light extraction structure,
Applying a liquid preliminary mixture of two or more preliminary materials having different densities onto the light emitting structure,
Holding the liquid preliminary material mixture on the light emitting structure to arrange the liquid preliminary material mixture according to the density,
And solidifying the liquid preparative material mixture to form a solidified material layer. The method according to claim 15 or 17,
Before forming the light extracting structure, further comprising forming a transparent electrode on the light emitting structure. 19. The method of claim 18,
And forming a portion of the upper semiconductor layer and the active layer to expose a portion of the lower semiconductor layer before forming the solidified material layer. 18. The method of claim 17,
Forming the solidified material layer,
Applying a preliminary material on the light emitting structure by any one of spin coating, bar coating, and doctor blade;
A method of manufacturing a light emitting diode comprising solidifying the preliminary material. The method of claim 20,
The preliminary material comprises a light emitting diode including any one selected from nanoimprint resin, photoresist, polyimide, sol-gel, and SOG or a mixture thereof. delete delete delete delete The method of claim 19,
And forming a first electrode and a second electrode electrically connected to the lower semiconductor layer and the upper semiconductor layer. 27. The method of claim 26,
The forming of the first electrode and the second electrode includes etching the partial region of the light extracting structure to expose the upper semiconductor layer and the lower semiconductor layer partial region.

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