KR20140126009A - Manufacturing method for UV-light emitting diode and UV-light emitting diode - Google Patents

Abstract

The present invention relates to a method of manufacturing an ultraviolet light emitting diode and an ultraviolet light emitting diode. The method of manufacturing an ultraviolet light emitting diode according to the present invention is a method of manufacturing a nitride semiconductor based ultraviolet light emitting diode including a nitride based semiconductor layer in which an n-type clad layer, an active layer and a p- . In depositing the p-electrode on the p-type cladding layer, the p-electrode is deposited only in an area of 70% or less and 10% or more of the area of the top of the p-type cladding layer. The shape of the p-electrode may be a mesh shape, a perforated plate shape, a one-dimensional grid shape, or the like.
The ultraviolet light emitting diode manufactured by the method of manufacturing the ultraviolet light emitting diode according to the present invention is manufactured by a simple process and the p-type cladding layer is exposed in a large area, thereby increasing the transmittance of ultraviolet rays through the portion where the p- Of ultraviolet light emitting diodes.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an ultraviolet light emitting diode,

The present invention relates to a method of manufacturing an ultraviolet light emitting diode and an ultraviolet light emitting diode, and more particularly, to a method of manufacturing an ultraviolet light emitting diode including a nitride based semiconductor layer in which an n-type clad layer, an active layer and a p- The p-electrode is deposited on the p-type cladding layer, and the ultraviolet ray emission efficiency is increased by depositing only the area of not less than 70% and not less than 3% of the upper area of the p-type cladding layer The present invention relates to a method for manufacturing an ultraviolet light emitting diode and a UV light emitting diode.

Light emitting diodes (LEDs) are devices that convert electrical signals into light using the characteristics of semiconductors. Since the development of light emitting diodes that emit red light in 1962, they have been used in various fields such as infrared Diodes are being developed. In particular, ultraviolet light emitting diodes are used in various fields because they can be extracted ultraviolet rays safely at a low cost while having a very small form.

Generally, a light emitting diode has a pair of electrodes that are conductive to supply electricity to the device. Korean Patent Laid-Open No. 10-2010-0095134 discloses a light emitting device in which a transparent electrode layer is formed on a conductive semiconductor layer. Since the transparent electrode using ITO (indium tin oxide) has a good current spreading property and is widely used as an electrode, especially in the case of a nitride-based light emitting diode, the GaN used for the p- An ITO transparent electrode having a low sheet resistance as an electrode is advantageous. However, although the ITO thin film transmits light in the infrared and visible light regions well, ultraviolet light emitted from the light emitting diode has a low transmittance due to absorption of ultraviolet light emitted from the ITO thin film in the case of ultraviolet light having a short wavelength.

For this purpose, ultraviolet light emitting diodes are fabricated in a vertical structure in which an ultraviolet light emitting diode is fabricated in a flip chip structure that emits light in the substrate direction or a substrate is lifted off to fabricate a light emitting diode. However, Or cracks may be generated in the epilayed film layer constituting the light emitting diode, thereby deteriorating the performance of the manufactured ultraviolet light emitting diode.

Therefore, it is necessary to develop a highly efficient ultraviolet light emitting diode capable of realizing a certain optical characteristic without decreasing the light output of the emitted ultraviolet ray while using a conventional electrode material such as a transparent electrode or a metal electrode in the ultraviolet light emitting diode Do.

Patent Document 1: Korean Patent Laid-Open No. 10-2010-0095134 (Published on Aug. 30, 2010)

An object of the present invention is to provide an ultraviolet light emitting diode manufacturing method and an ultraviolet light emitting diode which have high efficiency by increasing the transmittance of emitted ultraviolet light.

An object of the present invention is to provide an ultraviolet light-emitting diode manufacturing method and an ultraviolet light-emitting diode which can manufacture an ultraviolet light-emitting diode at a low cost and are also simple in a manufacturing process.

In order to accomplish the above object, a method of manufacturing an ultraviolet light emitting diode according to an embodiment of the present invention includes a step of forming a nitride semiconductor layer and a p-electrode in which an n-type clad layer, an active layer and a p- A nitride semiconductor-based ultraviolet light-emitting diode is formed. In the method of manufacturing an ultraviolet light emitting diode according to an embodiment of the present invention, a p-electrode is deposited on a p-type cladding layer, but is deposited only in an area of 70% or less and 3% or more of an area of the p-type cladding layer.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the shape of the p-electrode may be one of a mesh shape, a perforated plate shape, and a one-dimensional grid shape.

A method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention may further include forming a bonding pad on the p-electrode and forming a gap between the p-electrode and the bonding pad so as to be radially larger around the bonding pad.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the p-electrode may have a width of 5 nm to 100 탆.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the thickness of the p-electrode may be 30 nm to 50 탆.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the p-electrode may be formed of one of ITO, ZnO, Ga ₂ O ₃ , SnO, CuO, Cu ₂ O, AgO ₂ and AgO.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the p-electrode may be formed of at least one of Ag, Ni, Pd, In, Zn, Mg and Pt.

In the method of manufacturing an ultraviolet light emitting diode according to another embodiment of the present invention, the width of the p-electrode adjacent to the bonding pad may be uneven.

The ultraviolet light emitting diode according to the embodiment of the present invention can be manufactured by the method of manufacturing the ultraviolet light emitting diode of the present invention.

The method of manufacturing an ultraviolet light-emitting diode of the present invention and the ultraviolet light-emitting diode are designed to minimize the area of the p-electrode while enhancing the transparency of the emitted ultraviolet light while smoothly spreading the current injected into the p- A high-efficiency ultraviolet light-emitting diode can be manufactured.

INDUSTRIAL APPLICABILITY The method of manufacturing an ultraviolet light-emitting diode and the ultraviolet light-emitting diode of the present invention can be used not only for transparent oxide electrode materials such as ITO, but also for manufacturing ultraviolet light-emitting diodes having high luminous efficiency while using metal electrodes having high contact resistance and conductivity of p- have.

1 (a) and 1 (b) are diagrams schematically showing an ultraviolet light emitting diode according to an embodiment of the present invention.
2 is a graph showing the transmittance of the ITO thin film according to the wavelength of light.
3 (a) and 3 (b) are views showing the shape of a p-electrode in the form of a perforated plate in an ultraviolet light emitting diode according to another embodiment of the present invention.
4 (a) and 4 (b) are views showing the shape of a one-dimensional grid-type p-electrode in an ultraviolet light-emitting diode according to another embodiment of the present invention.
5 is a view showing the shape of a one-dimensional grid-type p-electrode in an ultraviolet light emitting diode according to another embodiment of the present invention.
6 is a view showing the shape of a one-dimensional grid-shaped p-electrode in an ultraviolet light-emitting diode according to another embodiment of the present invention.
7 is a view showing the width of a p-electrode in the vicinity of a bonding pad in an ultraviolet light emitting diode according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some of the components in the drawings are exaggerated, omitted, or schematically illustrated.

1 (a) and 1 (b) schematically show an ultraviolet light emitting diode according to an embodiment of the present invention, and FIG. 2 is a diagram showing the transmittance of an ITO thin film according to a wavelength of light.

1, a buffer layer 1200, an n-type cladding layer 1300, an active layer 1400, and a p-type cladding layer (not shown) are formed on a substrate 1100 in order to manufacture an ultraviolet light emitting diode according to an embodiment of the present invention. 1500, a p-electrode 1600, and an n-electrode 1700 are formed. As the substrate 1100, silicon (Si), silicon carbide (SiC), sapphire (a-Al ₂ O ₃ ), gallium arsenide (GaAs), or the like may be used. In this embodiment, a sapphire substrate is used as the substrate 1100. The sapphire substrate is advantageous in light extraction efficiency and durability. In this embodiment, a sapphire substrate is used as the substrate 1100, but not limited thereto, and various substrates can be used

A buffer layer 1200 is formed on the substrate 1100. The buffer layer 1200 is a layer for buffering stress between the substrate and the layer grown thereon. The buffer layer 1200 is formed on the substrate 1100 for lattice match. In the process of growing the metal layer on the substrate 1100, the lattice constant between the substrate and the layer to be grown is inconsistent. In such a case, defects such as dislocation may occur and the crystal quality may be lowered. Such a defect can be reduced by the buffer layer 1200.

Next, an n-type cladding layer 1300 is deposited on the buffer layer 1200. The n-type cladding layer 1300 is formed mainly of GaN or AlGaN.

An active layer 1400 is formed on the n-type clad layer 1300. The active layer 1400 is a layer in which electrons and holes are recombined to generate light. The wavelength of light emitted from the ultraviolet light emitting diode is determined according to the kind of the material constituting the active layer 1400 and the thickness of the active layer 1400. As the active layer for ultraviolet light emission, GaN, AlGaN or InGaN or AlGaInN doped with a small amount of indium (In) may be used. In this embodiment, by controlling the composition of the material forming the active layer 1400, the wavelength of emitted light is set to 280 to 400 nm.

A p-type cladding layer 1500 is deposited on the active layer 1400. In the nitride semiconductor-based ultraviolet light-emitting diode, the p-type cladding layer 1500 is formed of GaN or AlGaN. By using an Al-based element for the p-type cladding layer 1500, the bandgap can be further increased. a p-type cladding layer doped at a high concentration or a p-InGaN layer containing a small amount of In may be deposited in order to improve ohmic contact resistance with the electrode layer on the p-type clad layer.

A p-electrode and an n-electrode are formed on the nitride semiconductor layer or a part of the etched nitride semiconductor layer. A part of the stacked p-type clad layer 1500, the active layer 1400 and the n-type clad layer 1300 where the n-electrode 1700 is to be formed is etched to expose the n-type clad layer 1300. An n-electrode 1700 is formed on the exposed n-type cladding layer 1300. The n-electrode 1700 may be formed of a metal such as Cr or Al. After forming the p-electrode 1600 and the n-electrode 1700, bonding pads 1620 and 1720 are formed on the p-electrode 1600 and the n-electrode 1700 for wire bonding.

Next, the p-electrode will be described.

A p-electrode 1600 is deposited on the p-type cladding layer 1500. The p-electrode 1600 has good contact resistance and current spreading properties, and is particularly made of an ITO material having high transparency. The thickness of the ITO deposited is 30 nm to 50 탆. The light emitted from the active layer 1400 is emitted through the p-electrode 1600 which is in contact with the top of the p-type cladding layer 1500. However, in the case of using the ITO thin film as the p-electrode, as shown in FIG. 2, the ITO thin film having high transmittance in the visible region has a disadvantage that the transmittance is drastically lowered due to the high absorption ratio in the ultraviolet region of 400 nm or less. Therefore, when the ITO thin film is used as the p-electrode 1600 in the ultraviolet light-emitting diode 1000, ultraviolet light emitted from the active layer of the light-emitting diode is absorbed, thereby greatly reducing the light extraction efficiency of the light-emitting diode and consequently lowering the light efficiency of the light- The results are retrieved. In the present invention, the p-electrode 1600 is deposited on the p-type cladding layer 1500 so that the area occupied by the p-type cladding layer 1500 is 70% or less in order to reduce the rate of absorption of ultraviolet rays while passing through the ITO electrode.

For this purpose, the ITO p-electrode is formed in a mesh shape in this embodiment. That is, the p-electrode 1600 is selectively deposited only on a part of the p-type cladding layer 1500. The width of the line of the p-electrode forming the mesh can vary from several nanometers to tens of micrometers. As the width of the line is decreased, the area occupied by the p-electrode 1600 on the ultraviolet light-emitting diode 1000 is reduced, and the efficiency of the ultraviolet light-emitting diode 1000 can be improved.

Specifically, the width of the p-electrode 1600 may be formed to be 5 nm to 100 탆. As the line width of the p-electrode 1600 is reduced, the area occupied by the p-electrode 1600 on the p-type cladding layer 1500 is reduced, thereby improving the efficiency of the ultraviolet light emitting diode. Depending on the characteristics of the material forming the p-electrode 1600 and the nitride semiconductor forming the p-type cladding layer 1500, the line width of the p-electrode can be changed to several tens of micrometers.

On the other hand, the thickness of the p-electrode 1600 can be changed to improve the characteristics of the electrode such as current spreading. Specifically, the thickness of the p-electrode 1600 may be 30 nm to 50 μm. When the thickness of the p-electrode 1600 is increased, the width of the line of the p-electrode 1600 may be reduced, and the influence of current spreading and other characteristics may be reduced. The thickness of the p-electrode 1600 may vary depending on the material and characteristics of the nitride semiconductor-based ultraviolet light-emitting diode to be manufactured.

3 (a) and 3 (b) are views showing the shape of a p-electrode in the form of a perforated plate in an ultraviolet light emitting diode according to another embodiment of the present invention, and Figs. 4 (a) FIG. 5 is a view showing the shape of a one-dimensional grid-type p-electrode in an ultraviolet light-emitting diode according to another embodiment of the present invention, and FIG. And FIG. 6 is a view illustrating the shape of a one-dimensional grid-type p-electrode in an ultraviolet light-emitting diode according to another embodiment of the present invention.

In this embodiment, the shape of the p-electrode 1600 is a meshed shape. However, in another embodiment, the shape of the p-electrode 1600 may be a perforated plate shape, a one-dimensional grid shape, or the like. 3 (a) and 3 (b), the shape of the p-electrode 1600 may be a shape in which a circular shape is punched on a plate or a shape in which a hexagonal shape is punched. In such an electrode, the area where the p-type cladding layer 1500 is exposed due to the circular shape or the hexagonal shape may be 30% or more of the area of the p-type cladding layer 1500. The size of the circular or hexagonal shape can be variously changed according to the embodiment, and the shape is not limited thereto, and various polygonal shapes can be used.

In another embodiment, it may be in the form of a one-dimensional grid in the form of a p-electrode 1600, as shown in Figures 4 and 5. [ 4, the p-electrode 1600 is formed in a radial shape on the p-type cladding layer 1500 with the bonding pad 1620 as a center. A plurality of radial p-electrodes 1600 overlap the linear p-electrode 1600 disposed from the bonding pad 1620. Accordingly, the current spreading property can be improved while reducing the area occupied by the p-electrode 1600 on the p-type cladding layer 1500. The spacing between the p-electrodes 1600 may become larger in the radial direction around the bonding pad 1620. [ As the spacing between the lines forming the p-electrode 1600 increases, the area of the exposed p-type cladding layer 1500 increases and the efficiency of the ultraviolet light emitting diode increases. Considering the current spreading characteristics, the interval between the lines can be optimized to maximize the optical characteristics according to the structure of the light emitting diode.

As shown in FIGS. 5A and 5B, the p-electrode 1600 may be formed of a plurality of parallel lines. In this case as well, the distance between the p-electrodes 1600 can be increased as the spacing between the p-electrodes 1600 increases from the bonding pad. With this configuration, the area occupied by the p-electrode 1600 at the upper portion of the ultraviolet LED 1000 is further reduced, The emission area can be increased. In another embodiment, as shown in FIG. 6, a point at which the horizontal line and the vertical line meet at the mesh-shaped p-electrode 1600 is formed thicker, for example, in the form of a dot, have.

By depositing the p-electrode 1600 only on a part of the p-type cladding layer 1500, that is, in a region of 70% or less, the ratio of ultraviolet rays absorbed while passing through the ITO electrode is reduced, have. The area where the p-electrode 1600 is formed may be 70% or less of the upper surface area of the p-type cladding layer 1500, 3% or more, and preferably 50% or less and 10% or more. When the area of the p-electrode 1600 is 70% or more of the upper surface area of the p-type cladding layer 1500, the light extraction efficiency may be lowered. When the p-electrode 1600 is 3% or less, There is a fear of not being able to do. When the p-type clad layer 1500 is exposed to 30% or more, ultraviolet ray extraction efficiency is increased.

In this embodiment, however, use the ITO thin film as the p- electrode 1600, in other embodiments as a material for forming the p- electrode 1600. In addition to ITO MgO, BeO ZnO, Ga ₂ O _3, SnO, CuO, Cu ₂ O, AgO ₂ , and AgO, and ZnMgO 2, ZnBeO 2, or the like mixed with two or more of these oxides can be used.

Since the area occupied on the p-type cladding layer 1500 is reduced by manufacturing the p-electrode 1600 in this mesh form, it is necessary to form the p-electrode 1600 as a transparent electrode such as ITO There is no. The p-electrode 1600 may be a metal electrode material that is widely used as a p-electrode such as Ag, Ni / Au, Ni, Pd, In, Zn, Mg, or Pt as well as a transparent electrode material such as ITO. The p-electrode 1600 may be formed of one of Ag, Ni, Pd, In, Zn, Mg, and Pt, or an alloy of two or more metals. In the case of such a metal electrode, since the ohmic contact resistance with the p-type cladding layer 1500 is lower than that of the oxide transparent electrode, it is judged that the current spreading effect and the effect of reducing the driving voltage are greater.

The oxide electrode or the metal electrode such as ITO can be selectively deposited on the p-type cladding layer 1500 in a mesh shape using an electron beam or a laser beam. As the electrode is formed in the form of a mesh, ultraviolet rays are not absorbed at the portion where the electrode is not deposited, and the transmittance of ultraviolet rays is increased. As an evaporation method, an ITO thin film may be deposited on the p-type cladding layer 1500 and a portion thereof may be etched to form a mesh. In this case, however, the electrical characteristics of the thin film are lowered by etching to the p- There is a fear that spreading may not be smooth, and the process is also complicated. The present invention is directed to selective deposition using a beam and to design the electrode so as not to affect current spreading by adjusting the width, spacing and thickness of the mesh.

Meanwhile, a printing technique can be used to deposit the ITO thin film into a desired shape. When an ITO thin film is deposited by a printer, various shapes can be easily deposited without being subjected to an exposure process, and the thickness of the line can be finely miniaturized. The ITO thin film has a good current spreading property and can evenly spread the current to the p-type cladding layer 1500 and the active layer 1400 even in a fine line pattern, thereby improving the luminous efficiency in the active layer 1400.

Since the ultraviolet ray emitted from the active layer 1400 is emitted to the portion where the p-electrode 1600 is not deposited, light can be smoothly transmitted in the upward direction, thereby increasing ultraviolet ray emitting efficiency. Since the area occupied by the p-electrode 1600 on the upper portion of the ultraviolet light emitting diode is reduced, the p-electrode 1600 does not need to be transparent, so that Ag, Ni, Pd , In, Zn, Mg, Pt, or the like may be used, thereby increasing the degree of freedom of the material and reducing the manufacturing cost.

Meanwhile, an ohmic contact layer having the same shape as that of the p-electrode 1600 may be further provided between the p-type cladding layer 1500 and the p-electrode 1600 so as to facilitate ohmic contact formation. As the ohmic contact layer, a material such as Ag, Pd, or Ni, a metal alloy, or a transparent electrode can be used, thereby reducing the sheet resistance value of the p-electrode 1600 and improving current spreading. The ohmic contact layer allows the p-electrode 1600 to uniformly distribute the current, thereby spreading the current evenly across the active layer 1400 and increasing the luminous efficiency of the ultraviolet light-emitting diode 1000.

In general, the energy efficiency of a light emitting diode is about 40% or more, which is influenced by internal quantum efficiency, light extraction efficiency, electrical efficiency, package efficiency and the like. Herein, the internal quantum efficiency relates to the polarity of the substrate and the layer that is grown on the substrate, and by continuously growing the thin film on the substrate by MOCVD using various growth materials with high purity, It is increasing. Electrical efficiency is the efficiency with which electrons are injected from an external source into the light emitting diode, and electrical efficiency is related to chip process technology. The light extraction efficiency is an efficiency that allows the light generated inside the light emitting diode to escape to the outside as much as possible. In the embodiment of the present invention, the light extraction efficiency is further improved by deforming the shape of the p-electrode 1600.

7A and 7B are views showing the width of a p-electrode in the vicinity of a bonding pad in an ultraviolet light emitting diode according to an embodiment of the present invention.

A bonding pad 1620 is provided on the p-electrode 1600. When a current is supplied to the p-electrode 1600, a bottleneck may occur at a portion of the p-electrode 1600 located around the bonding pad 1620. [ If the current does not spread well due to the bottleneck phenomenon, the emission efficiency of the light emitting diode can not be reduced. In order to prevent this, the width of the p-electrode 1600 located adjacent to the bonding pad 1620 may be unevenly formed as shown in FIGS. 7A and 7B. When the shape of the p-electrode 1600 is a mesh shape, one to two horizontal lines and vertical lines near the bonding pad 1620 may be formed to be thicker than the line width of the other portion. When the shape of the p-electrode 1600 is a radial shape, one horizontal line and a vertical line near the bonding pad 1620, and the first concentric circle may be formed to be thicker than the width of the line of the other portion. Since the p-electrode 1600 around the bonding pad 1620 is formed thick, the current spreads uniformly throughout the p-electrode 1600. In another embodiment, the p-electrode located adjacent to the bonding pad may be formed thick as well as wide.

The ultraviolet light emitting diode according to the present invention has a high optical efficiency by minimizing the rate of absorption of ultraviolet rays emitted from the active layer by the p-electrode without affecting current spreadability of the p-electrode.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of the present invention in order to facilitate description of the present invention and to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

1000: ultraviolet light emitting diode 1100: substrate
1200: buffer layer 1300: n-type cladding layer
1400: active layer 1500: p-type cladding layer
1600: p-electrode 1620: bonding pad
1700: n- electrode 1720: bonding pad

Claims (9)

A nitride semiconductor-based ultraviolet light emitting diode comprising a nitride based semiconductor layer in which an n-type clad layer, an active layer and a p-type clad layer are sequentially stacked, and a p-electrode and an n-
Wherein the p-electrode is deposited on the p-type cladding layer, and the p-electrode is deposited only in an area of 70% or less and 3% or more of the area of the upper surface of the p-type cladding layer. The method according to claim 1,
Wherein the shape of the p-electrode is one of a mesh shape, a perforated plate shape, and a one-dimensional grid shape. 3. The method of claim 2,
A bonding pad is further formed on the p-electrode,
Wherein the gap between the p-electrodes is radially enlarged about the bonding pad. 4. The method according to any one of claims 1 to 3,
Wherein the p-electrode has a width of 5 nm to 100 탆. 4. The method according to any one of claims 1 to 3,
Wherein the p-electrode has a thickness of 30 nm to 50 탆. 4. The method according to any one of claims 1 to 3,
Wherein the p-electrode is formed of one of ITO, ZnO, Ga ₂ O ₃ , SnO, CuO, Cu ₂ O, AgO ₂ , and AgO. 4. The method according to any one of claims 1 to 3,
Wherein the p-electrode is formed of at least one of Ag, Ni, Pd, In, Zn, Mg, and Pt. The method of claim 3,
Wherein a width of the p-electrode located adjacent to the bonding pad is not constant. An ultraviolet light emitting diode produced by the method for manufacturing an ultraviolet light emitting diode according to any one of claims 1 to 3.

Images