KR100889614B1 - Nitrides light emitting device - Google Patents

Abstract

The light emitting device of the present invention has a P-type structure and an N-type structure with an active layer interposed therebetween, and a P-type electrode pad connected to the P-type structure and an N-type electrode pad connected to the N-type structure are arranged on the same line. A light emitting diode structure formed to be spaced apart from a predetermined interval; And a charge distribution changing device having a magnetic field generating device disposed in a left / right region adjacent to an imaginary line connected between the N-type electrode and the P-type electrode.

Therefore, the light emitting device according to the present invention includes a charge distribution changing device, and provides a magnetic field to the light emitting diode structure using Lorentz's law as the charge distribution changing device to improve the efficiency of devices such as light saturation phenomenon and device deterioration. There is an effect that can improve the luminous efficiency of the light emitting device by improving the current concentration phenomenon to decrease.

Description

Light emitting device {Nitrides light emitting device}

1 is a cross-sectional view showing the structure of a conventional mesa type light emitting device.

2 is a view showing charge distribution in a conventional mesa type light emitting device.

3 is a view showing the structure of a light emitting device according to the present invention;

Figure 4 is a plan view showing the action of the charge distribution changing device in the light emitting device according to the present invention.

5 is a view schematically showing a backlight unit having a light emitting device according to the present invention.

6 schematically illustrates a liquid crystal display device having a light emitting device according to the present invention.

Explanation of symbols on main parts of the drawings

30: light emitting element 50: backlight unit

60 liquid crystal display 310 substrate

320: buffer layer 330: N-type cladding layer

340: active layer 350: P-type cladding layer

360: multi-functional ohmic contact layer 370: P-type electrode pad

380 N-type electrode pad

The present invention relates to a light emitting device having a magnetic field generating device for changing a current distribution in a light emitting diode capable of emitting light.

Currently, research on photoelectric devices such as (near) ultraviolet light emitting diodes, laser diodes, and optical sensors has been actively conducted. Among them, single crystal nitride semiconductors are considered to be one of the most important materials in the optical industry. It is a situation.

1 is a cross-sectional view illustrating a structure of a conventional mesa type light emitting device, and FIG. 2 is a view illustrating charge distribution in a conventional mesa type light emitting device.

As shown in FIG. 1, the conventional mesa type light emitting device 10 includes a sapphire substrate 110 (Al ₂ O ₃ substrate), a nitride buffer layer 120, an N type nitride cladding layer 130, and a nitride active layer. 140, a P-type nitride cladding layer 150, and a multifunctional ohmic contact layer 160 are sequentially stacked.

A P-type electrode pad 170 is formed on the multifunctional ohmic contact layer 160, and a portion of the N-type nitride cladding layer 130 is etched, and the etched N-type nitride cladding layer 130 is formed. The N-type electrode pad 180 is formed on the top surface of the N-type electrode pad 180.

The sapphire substrate 110 to the P-type nitride cladding layer 150 corresponds to the light emitting structure, and the multifunctional ohmic contact layer 160 on the P-type gallium nitride cladding layer 150 corresponds to the P-type electrode structure. do.

In this case, when the mesa type light emitting device is driven, current flows in a path such as "A" shown in the drawing.

The conventional mesa type light emitting device 10 formed as described above has problems such as efficiency, large area, and surface concentration of current due to its structural characteristics.

Referring to FIG. 2, when the mesa type light emitting device 10 is driven, current does not flow to the entire area of the active layer 140, but concentrates on the edge of the mesa type light emitting device 10.

This phenomenon occurs because the resistivity of gallium nitride (P-type GaN layer) is larger than that of gallium nitride (N-type GaN layer) due to the characteristics of the gallium nitride compound. This is because the current flows by selecting the shortest distance in the transport.

The current crowding phenomenon of the current causes recombination of electrons and holes in the active layer 140 in a narrow region, thereby lowering the luminous efficiency of the light emitting diode.

In addition, heat is not a radial recombination of electrons and holes that cause photons due to recombination of defects and the like on the outer surface of the edge of the mesa type light emitting device 10. There is a problem that causes deterioration of the device due to non-radiative recombination that generates (Phonon).

As described above, the conventional mesa type light emitting device 10 has a problem in that the area for recombination decreases the luminous efficiency of the mesa type light emitting device 10 due to the current concentration phenomenon that causes recombination efficiency, deterioration of the device, and the like. .

The present invention has been made to solve the above problems, by disposing a charge distribution changer around the light emitting diode to solve the current concentration phenomenon that reduces the efficiency of the device, such as light saturation, deterioration of the device, the luminous efficiency is improved It is an object to provide an improved light emitting device.

Vertical light emitting device for achieving the object of the present invention has a P-type structure and an N-type structure with an active layer between, the P-type electrode pad connected to the P-type structure and the N-type connected to the N-type structure A light emitting diode structure in which electrode pads are disposed to be spaced apart from each other on the same line by a predetermined distance, and a state in which the light emitting diode structure is spaced apart from the light emitting diode structure in a left / right region adjacent to a virtual line connecting the N-type electrode pad and the P-type electrode pad. Disposed in each of the light emitting diode structures, and disposed so that a magnetic field flows between the P-type electrode pad and the N-type electrode pad so that a current flows in a direction perpendicular to each other. And a charge distribution changing device having a magnetic field generating device for distributing charge distribution to the entire area of the active layer.

The magnetic field generating device is characterized in that it comprises an electromagnet or a permanent magnet.

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Magnetic field strength of the magnetic field generating device is characterized in that 0.1 to 3 Tesla (Tesla).

On the other hand, the backlight unit for achieving the object of the present invention is a light source formed of a plurality of light emitting elements according to the present invention; A plurality of optical members for collecting, diffusing and guiding light emitted from the light source; And a mold frame protecting the light source and the optical member.

In addition, a liquid crystal display device for achieving the object of the present invention comprises a liquid crystal panel having a liquid crystal; It characterized in that it comprises a backlight unit using a plurality of light emitting elements formed by the present invention for providing light from the liquid crystal panel back as a light source.

Illumination device for achieving the object of the present invention is formed as described above; A package covering the light emitting device; It includes a supply device for supplying power to the light emitting device.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

In addition, in the drawings, the size and thickness of layers and films or regions are exaggerated for clarity of description, and when any film or layer is described as being formed "on" of another film or layer, It may be directly on top of the other film or layer, and a third other film or layer may be interposed therebetween.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing the structure of a light emitting device according to the present invention.

Referring to FIG. 3, the light emitting device 30 according to the present invention will be described as an embodiment of a nitride light emitting device in which a nitride semiconductor thin film is grown.

The nitride-based (GaN) semiconductor material is a compound semiconductor material having a broad energy band structure of 3.4 eV, high thermal stability, and electrical and optical properties as a light emitting material capable of emitting blue and purple light from green.

In the light emitting device 20 according to the present invention, a light emitting diode structure 300 and a charge distribution changing device 200 are disposed around the light emitting diode structure 300.

The light emitting diode structure 300 includes a substrate 310, a buffer layer 320, an N-type cladding layer 330, an active layer 340, a P-type cladding layer 350, a multifunctional ohmic contact layer 360, and a P-type. The electrode pads 370 are stacked in this order.

The light emitting diode may be formed by etching a portion of the N-type cladding layer 330 and a plurality of layers formed on the N-type cladding layer 330 and forming an N-type electrode pad 380 in the etched region. The structure 300 is formed. Thus, in the present invention, the light emitting diode structure 300 will be described as an embodiment of the mesa type light emitting diode.

The substrate 310 may use an insulating sapphire (Al ₂ O ₃ ) material. The sapphire substrate 310 has a crystal structure of hexagonal closed packings (HCP) having the same crystal structure as that of the nitride semiconductor. The buffer layer 320 is formed on the substrate 310.

The buffer layer 320 is gallium nitride at a temperature of 490 ° C. to 570 ° C. in order to suppress defects that may occur due to a large lattice constant and thermal expansion coefficient difference between the substrate 310 and the nitride semiconductor. It can be formed by growing (GaN) or aluminum nitride (AlN).

The N-type cladding layer 330 is formed of aluminum-indium-gallium-nitrogen (AlxInyGazN: x + y + z = 1, 0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1). The N-type cladding layer 330 may be formed by adding an N-type dopant such as Si, Ge, Se, or Te to gallium nitride.

The active layer 340 may be formed of a layer of Al x In y Ga z N (x, y, z: x + y + z = 1, 0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1), or a single layer or It can be formed of a multilayer or quantum well (single or multi quantum well, hereinafter MQW). The active layer 340 may be formed of InGaN / GaN MQW or AlGaN / GaN MQW.

The P-type cladding layer 350 is made of aluminum-indium-gallium-nitrogen (AlxInyGazN: x + y + z = 1, 0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1). Gallium layer. The P-type cladding layer 350 may be formed by adding P-type dopants such as Mg, Zn, Ca, Sr, and Ba to gallium nitride (GaN).

Herein, the multi-functional ohmic contact layer 360 stacked on the P-type cladding layer 350 corresponds to a P-type electrode structure, from the substrate 310 to the P-type cladding layer 350. do.

The multifunctional ohmic contact layer 360 is a P-type electrode structure as a top-emitting device that emits light generated from the active layer 340 to the outside through the multifunctional ohmic contact layer 340. Alternatively, the light may be formed as a flip-chip device that emits light through the transparent sapphire substrate 310.

As such, the multifunctional ohmic contact layer 360 may selectively form a transparent conductive thin film layer or a reflective thick film layer on the P-type cladding layer 350.

The N and P electrode pads 370 and 380 may be formed on the P and N type cladding layers 320 and 350, respectively.

The P-type electrode pad 370 may be formed on the P-type cladding layer 350, that is, the multifunctional ohmic contact layer 360, and may have a structure in which nickel / gold or silver / gold are sequentially stacked. Can be.

In addition, the N-type electrode pad 380 may be formed on the N-type cladding layer 330 in an area where a portion of the N-type cladding layer 330 is etched from the multi-functional ohmic contact layer 360. .

Here, an N-type ohmic contact layer (not shown) may be further formed between the N-type cladding layer 330 and the N-type electrode pad 380. The N-type ohmic contact layer may be formed of a structure in which titanium / aluminum is sequentially stacked or thick films of various structures.

Where each layer is an electron beam evaporator, metal organic CVD (MOCVD), physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma laser deposition (PLD), dual-type thermal evaporator, sputtering Can be formed by a vapor deposition apparatus.

As described above, the nitride-based semiconductor may be stacked to form the light emitting diode structure 300 according to the present invention in a mesa structure.

Herein, the flow of charge in the light emitting diode structure 300 will be described. When the light emitting diode structure 300 is driven, the resistivity of the P-type GaN layer is high due to the characteristics of the gallium nitride compound. This phenomenon occurs because it is larger than the specific resistance of the N-type GaN layer, and the current flows by selecting the shortest distance in the carrier transport.

As such, as the current flows by selecting the shortest distance, the current may not flow in the entire area of the active layer 340, but may flow in the edge of the light emitting diode structure 300.

Therefore, the current is concentrated, and electrons and holes are recombined only in a narrow region of the active layer 340, thereby lowering the luminous efficiency of the light emitting diode structure 300.

Therefore, the light emitting device 30 according to the present invention includes a charge distribution changing device 200 that can improve the recombination efficiency of holes and electrons around the light emitting diode structure 300.

The charge distribution changing device 200 includes a left / right adjacent to an imaginary line connecting the N-type electrode pad 380 and the P-type electrode pad 370 arranged to be spaced apart from the light emitting diode structure 300 by a predetermined distance. The magnetic field generators 210 may be disposed in the right region, respectively. In this case, the magnetic field generating device 210 is preferably packaged in the light emitting device 30 together with the light emitting diode structure 300.

Preferably, the direction in which the current passes in the light emitting diode structure 300 and the flow of the magnetic field formed in the magnetic field generating device 210 may be disposed to be perpendicular to each other.

The magnetic field generating device 210 may form one or more structures, or may provide a plurality of structures to form the charge distribution changing device 200. At this time, the magnetic field generating device 210 is provided in a stacked form according to the stacked structure of the light emitting diode structure 300, or a virtual line connecting the N-type electrode pad 380 and the P-type electrode pad 370. It may be provided in a form arranged on the plane containing.

The charge distribution changing device 200 may use an electromagnet or a permanent magnet, and may use a device capable of changing the distribution of charge in the light emitting diode structure 300 as well as the magnet, that is, changing the direction of charge movement. have. In this case, when the permanent magnet is used, if the N pole and the S pole are disposed in the left / right regions, respectively, a magnetic field is naturally generated from the N pole to the S pole. When using an electromagnet, it should be connected to a separate power supply for applying current so that different polarities are generated in the left / right regions, and the charge distribution changing device 200 preferably includes all such devices. Do.

As such, the light emitting device 30 according to the present invention can improve the light emitting efficiency by using the charge distribution changing device 200 around the light emitting diode structure 300 and the light emitting diode structure 300.

Figure 4 is a plan view showing the action of the charge distribution changing device in the light emitting device according to the present invention.

In the present invention, a magnetic field generating device is provided in the charge distribution changing device as an embodiment for easy description.

Referring to FIG. 4, the magnetic field generating device 210 provided in the charge distribution changing device 200 may provide the N pole and the S pole with magnets, respectively.

The N pole and the S pole may generate a magnetic field, and the charge in the magnetic field may be changed by using the Lorentz law, in which a charge in the magnetic field is forced by the magnetic field in a predetermined direction.

Lorenz's law refers to the force that the charged particles receive in the magnetic field, and the force receives only the moving charge, and in the static magnetic field, the magnetic field only affects the direction of charge movement.

That is, the force F of the charge

F = e * [v * B] / c

Where B is magnetic flux density, v is velocity, and c is luminous flux.

In other words, it exerts a force on the moving charge, but the direction of the force is perpendicular to the direction of the magnetic flux and velocity, so the electromagnetic field does not work on the moving charged particles, but only changes the direction of movement.

When Lorentz's law is substituted into the light emitting device 30 according to the present invention, the current flows from the top to the bottom of the light emitting diode structure 300. That is, the P-type electrode pad 370 proceeds in the shortest distance toward the N-type electrode pad 380. Here, the current direction will be described with reference to the active layer 340, which is a region in which the light emitting diode structure 300 emits light.

In addition, the charge distribution changing device 200 forms a direction perpendicular to the current direction, and the magnetic field generating device 210 is configured to receive the force in a direction opposite to a partial region (on the edge) of the active layer 340. Place the magnet.

The magnetic field strength of the magnetic field generating device is preferably 0.1 to 3 Tesla.

Accordingly, the charges are distributed to a wide area of the active layer 340 by the force in the opposite direction from the edge region of the active layer 340.

That is, by improving the current surface concentration phenomenon that may be structurally formed in the light emitting diode structure 300, the charge is distributed to a wide area of the active layer 340, thereby improving recombination efficiency of electrons and holes.

As described above, the charge distribution changing device 200 provides a magnetic field to the light emitting diode structure 300 by using Lorentz's law to improve a current concentration phenomenon that lowers the efficiency of devices such as light saturation and device deterioration. By doing so, the luminous efficiency of the light emitting device 30 can be improved.

5 is a view schematically showing a backlight unit having a light emitting device according to the present invention.

Referring to FIG. 5, the backlight unit 50 may include a light source 35 including a plurality of light emitting elements 30 and a plurality of light guides, diffusers, and condensed light emitted from the light source 35. An optical member 510 is provided, and a mold frame 520 for accommodating the optical member 510 and the light source 35 is provided.

The light source 35 may include a plurality of light emitting devices 30 according to the present invention to emit white light to the outside. The light emitting device 30 used as the light source 35 may be packaged in one device to emit white light, and a plurality of light emitting devices 30 may gather to emit white light.

The optical member 510 may include a light guide plate for guiding light emitted from the light source 35, a diffusion sheet for diffusing light, a prism sheet for condensing the light, and the like.

The mold frame 520 is formed in a container shape for accommodating the light source 35 and the optical member 510, and protects the optical member 510 and the light source 35 from external flow and impact. Can be formed.

6 is a view schematically showing a liquid crystal display device having a light emitting device according to the present invention.

Referring to FIG. 6, since the liquid crystal display 60 is not a light emitting device but a light receiving device, a means for receiving light is required.

Thus, the liquid crystal display device 60 may be formed with a liquid crystal panel 610 having liquid crystals and a backlight unit 50 for providing light to the liquid crystal panel 610. That is, the liquid crystal display 60 is a device for displaying an image by transmitting light provided from the backlight unit 50.

As described above, the liquid crystal display device 60 displays a clear image by improving color reproducibility by using the light emitting element 30 according to the present invention in which the light source 35 of the backlight unit 50 improves the light emission efficiency. It can work.

As described above, the light emitting device according to the present invention includes a charge distribution changing device, and provides a magnetic field to the light emitting diode structure by using Lorentz's law as the charge distribution changing device. There is an effect that can improve the luminous efficiency of the light emitting device by improving the current concentration phenomenon that reduces the efficiency of the device.

Claims (11)

It has a P-type structure and an N-type structure with an active layer interposed therebetween, so that the P-type electrode pads connected to the P-type structure and the N-type electrode pads connected to the N-type structure are spaced apart from each other on the same line. A formed light emitting diode structure; And The light emitting diode structure may be spaced apart from the light emitting diode structure in a left / right area adjacent to an imaginary line connecting the N-type electrode pad and the P-type electrode pad, and may be packaged in the light emitting diode structure. A charge having a magnetic field generating device disposed between the P-type electrode pad and the N-type electrode pad in such a manner that a magnetic field flows in a direction perpendicular to each other and distributing the distribution of moving charges over the entire area of the active layer. A light emitting device comprising a distribution change device. delete The method of claim 1, The magnetic field generating device disposed on the left and right in the charge distribution changing device has a different polarity. delete The method of claim 1, The magnetic field generating device includes an electromagnet or a permanent magnet. The method of claim 1, The magnetic field strength of the magnetic field generating device is a light emitting device, characterized in that 0.1 to 3 Tesla (Tesla). delete A light source formed of a plurality of light emitting elements according to claim 1; A plurality of optical members for collecting, diffusing and guiding light emitted from the light source; And And a mold frame protecting the light source and the optical member. The method of claim 8, And the light source emits white light by combining a plurality of light emitting elements. A light emitting element according to claim 1; A package covering the light emitting device; Lighting device including a supply device for supplying power to the light emitting device. A liquid crystal panel having liquid crystals; A liquid crystal display device comprising a backlight unit using the light emitting device according to claim 1 for providing light from the liquid crystal panel back surface.

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