KR20110074808A - Light emitting diode, light emitting device and back light unit using the same - Google Patents

Abstract

PURPOSE: A light emitting diode, a light emitting element using the same, and a backlight unit are provided to improve light emitting efficiency by uniformly supplying drive current to a light emitting layer of a light emitting diode. CONSTITUTION: A first N-GaN layer(32) is formed at a front side of an undoped U-GaN layer(31). A first activation alloy layer(33) is formed on a front surface of the first N-GaN layer. A second N-GaN layer(34) is formed on a front surface of the first activation alloy layer and is partially etched. An active layer is formed on a front surface of the undoped second N-GaN layer which is not etched. A P-GaN layer(36) is formed on a front side of the active layer. A transparent conductive oxide layer is formed on a front surface of the P-GaN layer. A first electrode is formed on a partial surface of the first activation alloy layer in which the second N-GaN layer is etched. A second electrode is formed on a partial surface of the transparent conductive oxide(37).

Description

LIGHT EMITTING DIODE, LIGHT EMITTING DEVICE AND BACK LIGHT UNIT USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode, and more particularly, to a light emitting diode, a light emitting device using the same, and a back light unit, which improve the light emitting efficiency by supplying a driving current evenly to the light emitting layer of the light emitting diode.

Recently, a light emitting diode having an excellent monochromatic peak wavelength, excellent light efficiency, and miniaturization can be used as a light emitting device. The light emitting diode uses a phenomenon of emitting light when electrons transition, and light is generated when electrons in a semiconductor conduction band recombine with holes in a valence band.

The emission wavelength of the light emitting diode is controlled by changing the type of impurities added to the semiconductor. Silicon carbide (SiC) and group III nitrides, particularly GaN (gallium nitride), are used to generate light having a spectrum of blue or ultraviolet wavelengths. Mainly used.

In general, in a horizontal type light emitting diode using GaN, an N-GaN layer, an active layer, and a P-GaN layer are sequentially stacked on a semiconductor substrate, and then a mesa (Mesa) is formed from the P-GaN layer to the N-GaN layer. ) And each electrode is formed on the upper portion of the mesa-etched N-GaN layer and the uppermost non-etched P-GaN layer. When a positive load and a negative load are applied to each electrode of the GaN-based light emitting diode thus completed, holes and electrons are gathered and recombined into the active layer from the P-GaN and N-GaN layers, respectively. Will emit light.

However, since the current supplied to the light emitting diode, that is, electrons and holes, is only intended to move in the shortest distance, electrons and holes are not diffused well and thus are not evenly supplied to the active layer, the P-GaN layer, and the N-GaN layer. There is no problem.

In other words, the electrons and holes supplied to each electrode are concentrated only on the shortest paths of the active layer, the P-GaN layer, and the N-GaN layer, so that the electrons and holes are not diffused well except the shortest path. In this case, since the area where electrons and holes are activated, that is, the area where light is generated, also becomes small, the luminous efficiency of the light emitting diode is reduced.

The present invention is to solve the above problems, and relates to a light emitting diode and a light emitting device and a backlight unit using the same to improve the light emitting efficiency by supplying a driving current evenly to the light emitting layer of the light emitting diode.

Light emitting diode according to an embodiment of the present invention for achieving the above object is an undoped U-GaN layer; A first N-GaN layer formed on an entire surface of the undoped U-GaN layer; A first activation alloy layer formed on the entire surface of the first N-GaN layer; A second N-GaN layer formed by etching a portion of the surface of the first activation alloy layer on the front surface thereof; An active layer formed on an entire surface of the second non-etched N-GaN layer; A P-GaN layer formed on the front surface of the active layer; A transparent conductive oxide layer formed on the entire surface of the P-GaN layer; A first electrode formed on a portion of a surface of the first activation alloy layer in which the second N-GaN layer is etched; And a second electrode formed on a portion of the transparent conductive oxide.

The first activation alloy layer is characterized by being formed of a high electrical conductivity of gold, aluminum, nickel, titanium, platinum, silver or an alloy of these and GaN.

The first activated alloy layer is formed on the entire surface of the first N-GaN layer by at least one of ion implantation, sputtering, or organometallic chemical vapor deposition (MOCVD).

The first N-GaN layer is characterized in that the damaged portion is recovered through the Rapid Thermal Annealing Method (RTH) after the first activation alloy layer is formed.

A second activation alloy layer is further formed on the front surface of the transparent conductive oxide layer in the same manner as the first activation alloy layer, in which case the second electrode is not part of the transparent conductive oxide but the second activation alloy layer. Characterized in that formed on a portion of the surface.

The second activation alloy layer is characterized in that the electrical conductivity is made of gold, aluminum, nickel, titanium, platinum, silver or an alloy of these and GaN.

The second activation alloy layer is formed on the front surface of the transparent conductive oxide layer through at least one of ion implantation, sputtering or organometallic chemical vapor deposition.

The light emitting diode of the present invention having the above characteristics, the light emitting device using the same, and the backlight unit may improve the light emission efficiency by supplying the driving current evenly to the light emitting layer of the light emitting diode. In addition, as the driving current is evenly supplied as described above, the internal resistance may be reduced to reduce the amount of heat generated and to reduce the operating voltage.

Hereinafter, a light emitting diode according to an embodiment of the present invention having the features and effects as described above, a light emitting device using the same, and a back light unit will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a light emitting device according to an embodiment of the present invention, Figure 2 is a plan view of the light emitting device shown in FIG.

1 and 2 include at least one light emitting diode 16 for generating light; A lead frame (14) formed in the package frame (12) so that the at least one light emitting diode (16) is seated; And a fluorescent molding part 18 filled in the groove part of the package frame 12 to cover the at least one light emitting diode 16.

The package frame 12 may be formed of a resin series such as plastic, or may be made of a heat metal or the like for heat dissipation of the light emitting diode 16. When the package frame 12 is made of a resin series such as plastic, a silicon substrate or a glass substrate, the lead frame 14 such as a heat metal is connected to the light emitting diode 16. A groove is formed in the package frame 12 so that the fluorescent molding part 18 may be filled. The groove is filled with the fluorescent molding part 18 after the light emitting diode 16 is seated. In the case of FIG. 1, the package frame 12 is mounted on a separate printed circuit board 13 or the like. In this case, the lead frame 14 protruding to the outside may contact the printed circuit board 13.

The lead frame 14 is formed inside and outside the package frame 12 to penetrate the bottom surface and the outer surface of the groove portion of the package frame 12 so that the light emitting diode 16 is seated. May be divided into two and divided into first and second lead frames. Here, the first lead frame is configured to penetrate a portion of the bottom surface of the groove portion of the package frame 12 and one outer surface of the package frame 12, and the second lead frame is formed on one side of the groove bottom surface of the package frame 12 and the package. It is configured to penetrate the other outer surface of the frame (12). Each of the first and second lead frames may be connected to the first lead electrode 15 and the second lead electrode 17, and a driving voltage supplied from the outside may be supplied to the light emitting chip 16 through the respective lead electrodes 15 and 17. To be supplied.

The fluorescent molding part 18 covers all of the lead frame 14 exposed to the groove of the package frame 12, the light emitting diode 16 seated on the lead frame 14, and each of the lead electrodes 15 and 17. It is formed by filling the groove portion of the package frame 18 so as to. Here, the fluorescent molding unit 18 is formed of a transparent or opaque mold material by mixing a plurality of phosphors having different colors with a transparent or opaque synthetic resin at a predetermined ratio.

The light emitting diode 16 may be formed of a quaternary nitride compound device or the like which reduces the spontaneous polarization to allow a constant light generation path. Such a light emitting diode 16 will be described in more detail with reference to FIG. 3.

3 is a cross-sectional view illustrating in detail the light emitting diode of FIG. 1.

The light emitting diode 16 shown in FIG. 3 includes an undoped U-GaN layer 31; A first N-GaN layer 32 formed on the front surface of the undoped U-GaN layer 31; A first activation alloy layer 33 formed on the entire surface of the first N-GaN layer 32; A second N-GaN layer 34 formed by etching a portion of the surface of the first activation alloy layer 33 on the front surface thereof; An active layer 35 formed on the entire surface of the second non-etched N-GaN layer 34; A P-GaN layer 36 formed on the entire surface of the active layer 35; A transparent conducting oxide layer 37 formed on the entire surface of the P-GaN layer 36; A first electrode 42 formed on a portion of the first activation alloy layer 33 from which the second N-GaN layer 34 is etched; And a second electrode 44 formed on a portion of the transparent conductive oxide 37.

The frame in which the undoped U-GaN layer 31 is formed, for example, the lead frame 14, serves as a support for growing a constituent material constituting the light emitting diode 16, for example, GaN-based crystals. do. To this end, the lead frame 14 may be a sapphire (Sapphire) frame, zinc oxide (ZnO) frame, aluminum oxide frame, silicon (Si) frame, at least one of GaN, InGaN, AlGaN, AlInGaN Stacked template substrates may be used.

The method of forming the first N-GaN layer 32, the second N-GaN layer 34, the active layer 35, and the P-GaN layer 36 is not limited as long as it can deposit a thin GaN-based compound. Organometallic chemical vapor deposition (MOCVD) is suitable, although it may be used.

In order to form the first N-GaN layer 32, the first GaN layer 32 is doped with an appropriate dopant. Here, silicon, germanium, selenium, tellurium, carbon, or the like may be used as the dopant for N doping. When silicon is used, the doping concentration is generally about 1017 / cm3. The first N-GaN layer 32 may be formed in a two-layer structure of N + and N- with different doping concentrations.

In the case where the undoped U-GaN layer 31 is first formed on the lead frame 14, and then the first N-GaN layer 32 is formed thereon, a defect occurs due to a sharp change in the lattice period. It is possible to prevent the thin film characteristics from deteriorating.

The first activation alloy layer 33 is formed on the front surface of the first N-GaN layer 32 so that the current supplied through the first electrode 42 is evenly supplied to the first and second GaN 32, 34. do. This is to alleviate the characteristic that the current supplied to the first electrode 42 flows to the second electrode 44 through the shortest path adjacent to the first electrode 42 side, and is supplied to the first electrode 42. The current to be distributed is evenly distributed to the first and second GaN 32, 34. The first activation alloy layer 33 may be made of gold, aluminum, nickel, titanium, platinum, silver, or an alloy of GaN with high electrical conductivity. The first activation alloy layer 33 is formed on the entire surface of the first N-GaN layer 32 through ion implantation, sputtering, or organic metal chemical vapor deposition (MOCVD). On the other hand, if the first activation alloy layer 33 is formed, the first N-GaN layer 32 may be damaged, so after the formation of the first activation alloy layer 33 RTH method (Rapid Thermal Annealing Method) It is preferable to recover the damaged first N-GaN layer 32 by performing a.

The second N-GaN layer 34 is formed on the entire surface of the first activation alloy layer 33 so that a partial surface thereof is etched. The second N-GaN layer 34 is formed in the same manner as the first N-GaN layer 32. Similarly, the second N-GaN layer 34 may also be formed in a two-layer structure of N + and N- with different doping concentrations.

The active layer 35 is formed on the second N-GaN layer 34 to generate light in the light emitting diode 16. The active layer 35 may be represented by Al x Ga Y In 1-X-YN (0 ≦ x <1, 0 <y <1), and may be formed of binary systems such as aluminum nitride, gallium nitride and indium nitride, and gallium nitride-indium and Ternary systems such as gallium nitride-aluminum. Group III elements may be partially substituted with boron, thallium, and the like, and nitrogen may be partially substituted with phosphorus, arsenic, antimony, and the like.

The active layer 35 can adjust the wavelength of light emitted by changing the component composition. For example, about 22% of indium is included to emit blue light. And about 40% of indium is included to emit green light.

The P-GaN layer 36 may be formed through the same process as the first and second N-GaN layers 32 and 34. The dopants of the P-GaN layer 36 may be magnesium, zinc, beryllium, or calcium. , Strontium, barium and the like can be used. At this time, the P-GaN layer 36 can also be formed in a two-layer structure of P + and P- like the first and second N-GaN layers 32 and 34. The first N-GaN layer 32, the first activation alloy layer 33, the second N-GaN layer 34, the active layer 35, and the P-GaN layer 36 are sequentially arranged on the lead frame 16. After lamination, the P-GaN layer 36 needs to be activated. The activation method of the P-GaN layer 36 is to disassociate magnesium and hydrogen in order to prevent magnesium, which is a dopant of the P-GaN layer 36, from bonding with hydrogen and acting as a defect. More specifically, the heat treatment may be performed at 600 ° C. for about 20 minutes, and then heat treatment may be performed after forming the transparent conductive oxide layer 37 to be described later.

The transparent conductive oxide layer 37 is to reduce the total reflection of the light emitted from the light emitting diode 16 to the absorption and attenuation inside the light emitting diode 16. Light generated in the active layer 35 is emitted to the front surface through the first and second electrodes 42 and 44, the lead frame 14, and the like, wherein the first and second electrodes 42 and 44 and the lead frame are emitted. Due to the difference in refractive index of (14), the light incident at an angle greater than the critical angle is totally reflected and exits in the lateral direction of the light emitting element or is absorbed or attenuated therein, which is an important cause of lowering the luminous efficiency. The critical angle at which total reflection occurs is smaller as the refractive index of both media forming the interface increases. The refractive index of the GaN layer is about 2.4, and the air refractive index is close to one. Since the refractive index of the transparent conductive oxide layer 37 is about 1.7, the difference in refractive index with respect to the external environment (air or the like) of the light emitting diode 16 can be reduced.

The transparent conductive oxide layer 37 may be made of a material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or zinc carbon oxide (ZCO), and the transparent conductive oxide layer may have a light transmittance. Since is more than 90% can increase the light extraction efficiency. On the other hand, although not shown in the drawings, the transparent conductive oxide layer 16 can further reduce the total reflection by having an uneven portion having a shape of a stripe, scratch, rectangle, dome, cylinder, and the like. In addition, the uneven portion may be formed of a photonic crystal structure. Photonic crystals refer to optical structures that exhibit photonic band gaps, localization of light, nonlinearity of light, and strong dispersion characteristics. In particular, photonic crystals refer to shapes and patterns having a lattice period of a length similar to that of light. By utilizing such a photonic crystal, not only the light propagation can be controlled, but also the spontaneous emission can be controlled, which can greatly contribute to the improvement and miniaturization of the optical device.

A second activation alloy layer 38 formed in the same manner as the first activation alloy layer 33 may be further formed on the front surface of the transparent conductive oxide layer 37, in which case the second electrode 44 is It may be formed on a portion of the second activation alloy layer 38 instead of a portion of the transparent conductive oxide 37.

The second activation alloy layer 38 is formed on the front surface of the transparent conductive oxide layer 37 so that the current supplied through the second electrode 44 is evenly supplied to the P-GaN 36. This is to alleviate the characteristic that the current supplied to the first and second electrodes 42 and 44 flows only through the shortest distance path, and the current supplied to the first and second electrodes 42 and 44 are respectively Evenly distributed to the first and second GaN (32, 34) and P-GaN (36). Like the first activation alloy layer 33, the second activation alloy layer 38 may be made of gold, aluminum, nickel, titanium, platinum, silver, or an alloy of GaN with high electrical conductivity. In addition, the second activation alloy layer 38 is formed on the entire surface of the transparent conductive oxide layer 37 through ion implantation, sputtering, or organometallic chemical vapor deposition (MOCVD).

The second activation alloy layer 38 may have a high electrical conductivity, but may be formed in a pattern form because of poor light transmittance. In this case, the thinner the pattern width, the thinner the thickness is. Preferably, the pattern width of the second activation alloy layer 38 is 10 to 10000 kPa, and the thickness thereof may be 10 to 50000 kPa. When the second activation alloy layer 38 is formed in a pattern form, the shape may be formed in any one of a stripe shape, a lattice shape, a radial shape, a spider web shape, or a honeycomb shape.

The first activation alloy layer 33 or the second activation alloy layer 38 according to the present invention has a uniform current compared to the case where the current is supplied to the light emitting diode 16 only by the first and second electrodes 42 and 44. By injecting the light, the luminous efficiency can be increased as a result. In addition, the contact resistance can be reduced by allowing the current to be supplied evenly, and the amount of heat generated at the contact surface can also be reduced. In particular, the second activation alloy layer 38 can be formed between the transparent conductive oxide layer 38 and the second electrode 42, as well as between the transparent conductive oxide layer 37 and the P-GaN layer 36. Can be formed on. In this case, a lower contact resistance with the P-GaN layer 36 can be expected.

4 is an exploded cross-sectional view schematically illustrating a backlight unit and a liquid crystal display device to which the light emitting device of the present invention is applied.

The liquid crystal display shown in FIG. 4 includes a backlight unit 20; Panel guide 27; A liquid crystal panel 50; A case 61 is provided.

The backlight unit 20 is disposed on the front surface of the bottom cover 23 so as to face the plurality of light emitting elements 22, the bottom cover 23 accommodating the plurality of light emitting elements 22, and the plurality of light emitting elements 22. And a plurality of optical sheets 26 for diffusing and emitting light from the diffuser plate 25.

Each of the light emitting devices 22 may include light emitting devices 22 including the light emitting diodes 16 according to the exemplary embodiment of the present invention described above with reference to FIGS. 1 to 3. The light emitting devices 22 are detachably mounted to sockets (not shown) to face the liquid crystal panel 30.

The bottom cover 23 is a bottom surface facing the plurality of light emitting elements 22, an inclined surface inclined at a predetermined slope from the top and bottom of the bottom surface so as to correspond to the longitudinal direction of the light emitting element 22, and an inclined surface facing the bottom surface. It is made to include a seating portion extending from. In addition, a reflective sheet 24 for reflecting light from each light emitting element 22 toward the liquid crystal panel 30 is formed on the bottom surface and the inclined surface of the bottom cover 23.

The diffusion plate 25 is stacked on the front opening of the bottom cover 23. That is, the diffusion plate 25 is stacked on the upper surface of the seating portion of the bottom cover 23, and the diffusion plate 25 diffuses the light emitted from the plurality of light emitting elements 22 to the entire area of the liquid crystal panel 50. Let's do it.

The plurality of optical sheets 26 allow the light diffused by the diffusion plate 25 to be irradiated perpendicular to the liquid crystal panel 50. Here, the optical sheets 26 convert one diffusion sheet for diffusing the light emitted from the diffusion plate 25 to the entire area, and the propagation angle of the light diffused by the diffusion sheet to be perpendicular to the liquid crystal panel 50. And first and second prism sheets.

On the other hand, the panel guide 27 is mounted on the seating portion of the bottom cover 23 to wrap the edges and side surfaces of the diffusion plate 25 and the plurality of optical sheets 26 and surround the side surfaces of the bottom cover 23. . The panel guide 27 includes a panel supporter for supporting the liquid crystal panel 50. The panel support part is formed to be stepped to support the rear non-display area and the side surface of the liquid crystal panel 50.

The liquid crystal panel 50 is stacked on the panel support of the panel guide 27 to reflect the light incident to the front surface or to adjust the transmittance of the light incident from the backlight unit 20 to display an image.

The case 61 is bent to surround the front non-display area of the liquid crystal panel 50 and the side surface of the bottom cover 23. At this time, the case 61 is fastened to the panel guide 27 surrounding the side of the cover 23 is fixed.

As described above, the light emitting diode 16 and the light emitting device 22 and the backlight unit 20 using the same according to the embodiment of the present invention may be formed of the first activation alloy layer 33 or the second activation alloy layer ( Light is generated using the light emitting diode 16 in which 38 is formed. Thus, the present invention can not only increase the luminous efficiency of the light emitting element 22 or the backlight unit 20, but also reduce the contact resistance by allowing the current to be supplied evenly, and also reduce the amount of heat generated at the contact surface. Can be.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

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

FIG. 2 is a plan view of the light emitting device shown in FIG. 1. FIG.

3 is a cross-sectional view illustrating in detail the light emitting diode of FIG. 1.

4 is an exploded cross-sectional view schematically illustrating a backlight unit and a liquid crystal display device to which a light emitting device of the present invention is applied.

* Brief description of symbols for the main parts of the drawings.

12: package frame 14: lead frame

16: light emitting diode 18: fluorescent molding layer

31: U-GaN layer 32: First N-GaN layer

33: first activation alloy layer 34: second N-GaN layer

35: active layer 36: P-GaN layer

37: transparent conductive oxide layer 38: second activation alloy layer

Claims (9)

An undoped U-GaN layer; A first N-GaN layer formed on an entire surface of the undoped U-GaN layer; A first activation alloy layer formed on the entire surface of the first N-GaN layer; A second N-GaN layer formed by etching a portion of the surface of the first activation alloy layer on the front surface thereof; An active layer formed on an entire surface of the second non-etched N-GaN layer; A P-GaN layer formed on the front surface of the active layer; A transparent conductive oxide layer formed on the entire surface of the P-GaN layer; A first electrode formed on a portion of a surface of the first activation alloy layer in which the second N-GaN layer is etched; And And a second electrode formed on a portion of the transparent conductive oxide. The method of claim 1, The first activation alloy layer A light emitting diode, which is formed of gold, aluminum, nickel, titanium, platinum, silver, or an alloy of GaN with high electrical conductivity. The method of claim 2, The first activation alloy layer A light emitting diode formed on the front surface of the first N-GaN layer by at least one of ion implantation, sputtering, or organometallic chemical vapor deposition (MOCVD). The method of claim 3, wherein The first N-GaN layer After the first activation alloy layer is formed, the light emitting diode characterized in that the damaged portion is recovered through the Rapid Thermal Annealing Method (RTH method). The method of claim 4, wherein In front of the transparent conductive oxide layer A second activation alloy layer is further formed in the same manner as the first activation alloy layer, in which case the second electrode is formed on a portion of the second activation alloy layer rather than a portion of the transparent conductive oxide. Light emitting diode. The method of claim 5, The second activation alloy layer A light emitting diode comprising high electrical conductivity of gold, aluminum, nickel, titanium, platinum, silver or an alloy thereof with GaN. The method of claim 6, The second activation alloy layer A light emitting diode formed on the front surface of a transparent conductive oxide layer by at least one of ion implantation, sputtering or organometallic chemical vapor deposition. At least one light emitting diode for generating light; A lead frame formed in a package frame to seat the at least one light emitting diode; And A fluorescent molding part filled in a groove part of the package frame to cover the at least one light emitting diode, The at least one light emitting diode is a light emitting device having the characteristics of at least one of the first to seventh. A plurality of light emitting elements for generating light; A bottom cover to accommodate the plurality of light emitting elements; A diffusion plate disposed on a front surface of the bottom cover to face the plurality of light emitting devices; And A plurality of optical sheets for diffusing light from the diffuser plate and outputting the light; And said plurality of light emitting elements are light emitting elements having the features of claim 8.

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