KR102140274B1 - Light emitting device - Google Patents

Abstract

Examples include a substrate; A light emitting structure disposed on the substrate and including a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer disposed between the first conductivity type semiconductor layer; A first electrode and a second electrode disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, respectively; And a contact layer disposed on the second conductivity-type semiconductor layer adjacent to the second electrode and having an energy band gap smaller than that of the second conductivity-type semiconductor layer.

Description

Light emitting device {LIGHT EMITTING DEVICE}

The embodiment relates to a light emitting device.

Group 3-5 compound semiconductors such as GaN and AlGaN are widely used for optoelectronics and electronic devices due to many advantages such as having a wide and easily adjustable band gap energy.

In particular, light emitting devices such as light emitting diodes or laser diodes using semiconductor group 3 or 2-6 compound semiconductor materials of semiconductors include red, green, blue and ultraviolet light due to the development of thin film growth technology and device materials. Various colors can be realized, and white light with high efficiency can be realized by using fluorescent materials or combining colors, and low power consumption, semi-permanent life, fast response speed, safety, and environment compared to conventional light sources such as fluorescent lamps and incandescent lamps It has the advantage of affinity.

Accordingly, a light emitting diode backlight that replaces a Cold Cathode Fluorescence Lamp (CCFL) constituting a backlight of a transmission module of an optical communication means, a backlight of a liquid crystal display (LCD) display device, and white light emission that can replace a fluorescent lamp or an incandescent light bulb Applications are expanding to diode lighting devices, automotive headlights and traffic lights.

In a conventional light emitting device, a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer is formed on a substrate made of sapphire or the like, on a first conductivity type semiconductor layer and a second conductivity type semiconductor layer. The first electrode and the second electrode are respectively disposed.

The light emitting device emits light having energy determined by an energy band unique to a material forming an active layer when electrons injected through the first conductivity type semiconductor layer and holes injected through the second conductivity type semiconductor layer meet each other. The light emitted from the active layer may vary depending on the composition of the material constituting the active layer, and may be blue light, ultraviolet light (UV), or deep UV light.

In the case of a horizontal light emitting device, electrodes may be deposited by depositing metal on each of the first conductivity type semiconductor layer and the second conductivity type semiconductor layer grown as an epitaxial layer, and metal is connected to the semiconductor layer to form an ohmic contact. contact), otherwise rectification characteristics may appear and current may not flow in a specific direction.

In order to achieve an ohmic contact, a dopant may be heavily doped in the uppermost layer of the epitaxial layer. In the case of an n-type conductive semiconductor layer, a silicon (Si) doped InGaN/GaN superlattice structure is formed in the prior art. In the case of the conductive semiconductor layer, an InGaN/GaN superlattice structure doped with magnesium (Mg) was formed.

However, when the thickness of the superlattice structure described above is thick, the content of the dopant may be increased to lower the operating voltage, but there is a problem in that the light absorption rate is increased.

The embodiment is intended to improve the operating voltage of the light emitting device and prevent the light absorption rate from increasing at the same time.

Examples include a substrate; A light emitting structure disposed on the substrate and including a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer disposed between the first conductivity type semiconductor layer; A first electrode and a second electrode disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, respectively; And a contact layer disposed on the second conductivity-type semiconductor layer adjacent to the second electrode and having an energy band gap smaller than that of the second conductivity-type semiconductor layer.

In the contact layer, In may be doped.

The contact layer may have a thickness of 0.5 nanometers to 3 nanometers.

The contact layer is made of InGaN, and indium (In) may be doped between 2% and 10% in the contact layer.

The second conductivity type semiconductor layer may be disposed between a contact layer and the second electrode with a thickness of 0.5 nanometers to 3 nanometers.

The contact layer may be doped in p-type.

In the light-emitting device according to the embodiment, a contact layer doped with a p-type dopant is formed in the p-type semiconductor layer, thereby forming an ohmic contact and improving injection of holes, but the light absorption does not increase, so the operating voltage of the light emitting device is lowered and the light is lowered. The output may increase.

1 is a cross-sectional view of one embodiment of a light emitting device,
Figure 2a is a view showing the energy band gap of the light emitting device of Figure 1,
2b is a view showing an energy band gap of a conventional light emitting device,
3 is a view showing the improvement of the light efficiency of the light emitting device,
4 is a view showing an improvement in driving voltage of a light emitting device,
5 is a view showing an embodiment of a light emitting device package in which a light emitting device is disposed,
6 is a view showing an embodiment of a backlight unit in which a light emitting element is disposed,
7 is a view showing an embodiment of a lighting device in which a light emitting element is disposed.

Hereinafter, embodiments of the present invention capable of specifically realizing the above object will be described with reference to the accompanying drawings.

In the description of the embodiment according to the present invention, when described as being formed on "on (up) or down (down)" (on or under) of each element, the top (top) or bottom (bottom) (on or under) includes both two elements directly contacting each other or one or more other elements formed indirectly between the two elements. Also, when expressed as “on (up) or down (on or under)”, it may include the meaning of the downward direction as well as the upward direction based on one element.

2 is a cross-sectional view of one embodiment of a light emitting device.

In the light emitting device 100 according to the present embodiment, a buffer layer 115, a light emitting structure 120, an electron blocking layer 130, and a transmissive conductive layer 140 are disposed on a substrate 110, and the light emitting structure 120 ) Comprises a first conductivity type semiconductor layer 122, an active layer 124, and a second conductivity type semiconductor layer 126, the first conductivity type semiconductor layer 122 and the second conductivity type semiconductor layer 126 ), the first electrode 162 and the second electrode 126 may be disposed, respectively.

The substrate 110 may be formed of a material suitable for semiconductor material growth or a carrier wafer, may be formed of a material having excellent thermal conductivity, and may include a conductive substrate or an insulating substrate. For example, at least one of sapphire (Al ₂ O ₃ ), SiO ₂ , SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga ₂ 0 ₃ may be used.

The buffer layer 115 is disposed between the substrate 110 and the light emitting structure 120, and the material of the buffer layer 115 is a group 3-5 compound semiconductor such as AlN, AlAs, GaN, InN, InGaN, AlGaN, InAlGaN , AlInN.

When the substrate 110 is formed of sapphire or the like and the light emitting structure 120 including GaN or AlGaN is disposed on the substrate 110, lattice mismatch between the light emitting structure or the substrate is very large and therebetween. Since the difference in thermal expansion coefficient is also very large, dislocation, melt-back, crack, pit, and surface morphology defects that deteriorate crystallinity may occur. , The buffer layer 115 may be used.

The light emitting structure 120 includes a first conductivity type semiconductor layer 122, an active layer 124, and a second conductivity type semiconductor layer 126. The first conductivity-type semiconductor layer 122 may be doped with an n-type dopant, and the second conductivity-type semiconductor layer 126 may be doped with a p-type dopant. On the contrary, the first conductivity-type semiconductor layer 126 may be p-type. The dopant may be doped and the second conductivity type semiconductor layer 122 may be doped with an n-type dopant.

The first conductivity type semiconductor layer 122 may be implemented with a compound semiconductor such as a III-V group or a II-VI group, and a first conductivity type dopant, such as Si, Ge, Sn, Se, Te, or the like, may be doped. Can. The first conductivity-type semiconductor layer 122 may be formed of a nitride-based semiconductor material, and may be formed of any one or more of AlGaN, GaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, for example. May be made of a semiconductor material having a composition formula of Al _x In _y Ga _(1-xy) N (0≤x≤1, 0≤y≤1, 0≤x+y≤1).

The active layer 124 is disposed between the first conductivity type semiconductor layer 122 and the second conductivity type semiconductor layer 126, and has a single well structure, a double well structure, a single quantum well structure, and a multiple quantum well. (MQW: Multi Quantum Well) structure, a quantum dot structure or a quantum wire structure.

The active layer 124 is a well layer and a barrier layer using a compound semiconductor material of a group III-V element, for example, AlGaN/AlGaN, InGaN/GaN, InGaN/InGaN, AlGaN/GaN, InAlGaN/GaN, GaAs (InGaAs) It may be formed of any one or more pair structure of /AlGaAs, GaP (InGaP) / AlGaP, but is not limited thereto. The well layer may be formed of a material having an energy band gap smaller than the energy band gap of the barrier layer.

The second conductivity-type semiconductor layer 126 may be formed of a semiconductor compound. The second conductivity-type semiconductor layer 126 may be formed of a compound semiconductor such as a III-V group or a II-VI group, and a second conductivity-type dopant such as Mg, Zn, Ca, Sr, or Ba may be doped. Can. The second conductivity-type semiconductor layer 124c may be formed of a nitride-based semiconductor material, and may be formed of any one or more of AlGaN, GaN AlInN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, for example, In _x Al _y Ga _{1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) may be made of a semiconductor material having a composition formula.

A contact layer may be disposed in the second conductivity-type semiconductor layer 126, and the contact layer may be disposed adjacent to the second electrode 164, and the energy band gap of the contact layer may be the second conductivity. It may be smaller than the energy band gap of the type semiconductor layer 126. That is, the electron blocking layer 130 described later may be disposed adjacent to the active layer 124 and the contact layer may be disposed adjacent to the second electrode 164.

The contact layer may be doped with In (indium) to have a lower energy band gap than the second conductivity type semiconductor layer 126. For example, when the second conductivity type semiconductor layer is made of GaN, the contact layer may be made of InGaN. , The second conductivity type dopant may be doped. In addition, the In-doped concentration of the contact layer may be 2% to 10%.

2A is a view showing an energy band gap of the light emitting device of FIG. 1, and FIG. 2B is a view showing an energy band gap of the conventional light emitting device.

As illustrated, the contact layer may be InGaN doped with a p-type dopant, and the thickness (w ₁ ) of the contact layer may be 0.5 nanometers to 3 nanometers, and GaN may be used between the contact layer and the second electrode. The second conductive semiconductor layer may be formed to have a thickness w ₂ of 0.5 nanometers to 3 nanometers.

In the light emitting device having the above-described structure, since a contact layer having a low energy band gap is disposed in the direction of the second electrode and In is doped, holes can be supplied to the second conductive type semiconductor layer more than before. In addition, the contact layer is also doped with a second conductivity type dopant, so that the second electrode and the second conductivity type semiconductor layer form an ohmic contact, thereby lowering the operating voltage, but without using a conventional superlattice structure, light absorption is reduced.

If the thickness of the contact layer is 0.5 nanometers or more, an ohmic contact can be formed ldT, and if it is 3 nanometers or more, a decrease in luminosity due to light absorption may occur due to the thickness of the ohmic contact layer.

If the In composition in the contact layer is 2% or more, improvement of the hole injection effect can be expected, and if it exceeds 10%, the energy band gap becomes too small, and holes may be constrained.

An electron blocking layer 130 may be disposed between the active layer 124b and the second conductivity type semiconductor layer 124c, and an electron blocking layer having a superlattice structure may be disposed. The superlattice may be, for example, AlGaN doped with a second conductivity type dopant, and GaNs having different aluminum composition ratios may be layered to form a layer and alternately disposed.

A transparent conductive layer 140 is disposed on the light emitting structure 120 to promote current supply from the second electrode 164 to the second conductive semiconductor layer 126. The transparent conductive layer 140 is, for example, indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IZAO), indium gallium zinc oxide (IGZO), IGTO ( indium gallium tin oxide (AZO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO), IZON (IZO Nitride), AGZO (Al-GaZnO), IGZO (In-GaZnO), ZnO, IrOx , RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, and Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, It may be formed of at least one of Hf, and is not limited to such a material.

The second conductive semiconductor layer 126 and the active layer 124 and a portion of the first conductive semiconductor layer 122 are etched from the transparent conductive layer 140 so that a portion of the first conductive semiconductor layer 122 is exposed. , The first electrode 162 may be disposed on the exposed first conductivity type semiconductor layer 122, and the second electrode 164 may be disposed on the second conductivity type semiconductor layer 126.

The first electrode 162 and the second electrode 164 include a single layer including at least one of aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), copper (Cu), and gold (Au) Or it may be formed in a multi-layer structure.

3 is a view showing an improvement in light efficiency of a light emitting device.

The voltage through which the light emitting elements (Device A, Device B) in which the contact layer is grown according to the embodiment flows the same current is smaller than the conventional light emitting device (Reference Device), and thus the operating voltage is improved.

4 is a view showing an improvement in driving voltage of a light emitting device.

When the same current flows through the light emitting elements (Device A, Device B) in which the contact layer is grown according to the embodiment than the conventional light emitting device (Reference Device), the output (Power) is improved and the light emission efficiency (EQE) is also improved. have.

5 is a view showing an embodiment of a light emitting device package.

The light emitting device package 400 according to an embodiment includes a body including a cavity, a first lead frame 421 and a second lead frame 422 installed in the body, and the first lead frame 422. It includes a light emitting device 200a according to the above-described embodiments electrically connected to the lead frame 421 and the second lead frame 422, and a molding part 470 formed in the cavity.

The body may be formed of a silicon material, a synthetic resin material, or a metal material. When the body is made of a conductive material such as a metal material, although not illustrated, an insulating layer is coated on the surface of the body to prevent electrical shorts between the first and second lead frames 421 and 422.

The first lead frame 421 and the second lead frame 422 are electrically separated from each other, and supplies current to the light emitting device 200a. In addition, the first lead frame 421 and the second lead frame 422 may reflect light generated from the light emitting device 200a to increase light efficiency, and heat generated from the light emitting device 200a may be externally applied. It can also be discharged.

The light emitting device 200a may be fixed to the first lead frame 421 with a conductive paste (not shown) or the like, and the electrode 430 may be bonded to the second lead frame with a wire 450.

The molding part 470 may surround and protect the light emitting device 200a. In addition, a phosphor 480 may be included on the molding part 470. In this structure, the phosphor 480 is distributed, and the wavelength of light emitted from the light emitting device 200a can be converted in all regions where light from the light emitting device package 400 is emitted.

The light emitting device package 400 may be mounted as one or a plurality of light emitting devices according to the above-described embodiments, but is not limited thereto.

Hereinafter, an image display device and a lighting device will be described as an embodiment of the lighting system in which the above-described light emitting device package is disposed.

6 is a view showing an embodiment of an image display device including a light emitting device package.

As shown, the image display apparatus 500 according to the present embodiment is disposed in front of the light source module, the reflector 520 on the bottom cover 510, and the reflector 520, the light emitted from the light source module The light guide plate 540 for guiding the front of the image display device, the first prism sheet 550 and the second prism sheet 560 disposed in front of the light guide plate 540, and the second prism sheet 560 It comprises a panel 570 disposed in front and a color filter 580 disposed in front of the panel 570.

The light source module includes a light emitting device package 535 on the circuit board 530. Here, a PCB or the like may be used as the circuit board 530, and the light emitting device disposed in the light emitting device package 535 may be in accordance with the above-described embodiments.

The bottom cover 510 may store components in the image display device 500. The reflector 520 may be provided as a separate component, as shown in the figure, or may be provided in a form coated with a material having high reflectivity on the back of the light guide plate 540 or the front of the bottom cover 510.

The reflector 520 may use a material having a high reflectance and an ultra-thin type, and may use PolyEthylene Terephtalate (PET).

The light guide plate 540 scatters the light emitted from the light emitting device package module so that the light is uniformly distributed over the entire screen area of the liquid crystal display. Therefore, the light guide plate 530 is made of a material having good refractive index and transmittance, and may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), or polyethylene (PolyEthylene; PE). Also, when the light guide plate 540 is omitted, an air guide type display device may be implemented.

The first prism sheet 550 is formed of a polymer material having a light transmissive elasticity on one surface of a support film, and the polymer may have a prism layer in which a plurality of three-dimensional structures are repeatedly formed. Here, the plurality of patterns may be repeatedly provided in a stripe type as the floor and the valley as shown.

In the second prism sheet 560, the direction of the floors and valleys of one side of the support film may be perpendicular to the direction of the floors and valleys of one side of the support film in the first prism sheet 550. This is to evenly distribute the light transmitted from the light source module and the reflective sheet in all directions of the panel 570.

In this embodiment, the first prism sheet 550 and the second prism sheet 560 form an optical sheet, the optical sheet is made of a different combination, for example, a micro lens array or a diffusion sheet and a micro lens array. Combination or a combination of a single prism sheet and a micro lens array.

The panel 570 may be provided with a liquid crystal display panel, and other types of display devices that require a light source may be provided in addition to the liquid crystal display panel 560.

In the panel 570, a liquid crystal is positioned between the glass bodies and a polarizing plate is placed on both glass bodies in order to use polarization of light. Here, the liquid crystal has an intermediate property between a liquid and a solid, and the liquid crystal, which is an organic molecule having liquidity, has a state in which the liquid crystals are regularly arranged like crystals, and the molecular arrangement is changed by an external electric field. Display an image.

A liquid crystal display panel used in a display device is an active matrix method, and a transistor is used as a switch for controlling the voltage supplied to each pixel.

A color filter 580 is provided on the front surface of the panel 570 to transmit the light projected from the panel 570 and transmit only red, green, and blue light for each pixel, so that an image can be expressed.

7 is a view showing an embodiment of a lighting device in which a light emitting element is disposed.

The lighting device according to the present embodiment may include a cover 1100, a light source module 1200, a heat radiator 1400, a power supply unit 1600, an inner case 1700, and a socket 1800. In addition, the lighting device according to the embodiment may further include any one or more of the member 1300 and the holder 1500, the light source module 1200 includes a light emitting device package according to the above-described embodiments, light emission The angle of light emission can be adjusted by the cavity structure formed in the device, and thus a light concentration effect in a specific direction can be obtained, so that the light emitting area can be adjusted without a separate mechanism outside the lighting device.

The cover 1100 has a shape of a bulb or a hemisphere, is hollow, and may be provided in an open shape. The cover 1100 may be optically coupled to the light source module 1200. For example, the cover 1100 may diffuse, scatter, or excite light provided from the light source module 1200. The cover 1100 may be a kind of optical member. The cover 1100 may be combined with the heat sink 1400. The cover 1100 may have a coupling portion coupled to the heat radiator 1400.

A milky white coating may be coated on the inner surface of the cover 1100. The milky white paint may include a diffusion material that diffuses light. The surface roughness of the inner surface of the cover 1100 may be greater than the surface roughness of the outer surface of the cover 1100. This is for light from the light source module 1200 to be sufficiently scattered and diffused to be emitted to the outside.

The material of the cover 1100 may be glass, plastic, polypropylene (PP), polyethylene (PE), polycarbonate (PC), or the like. Here, polycarbonate has excellent light resistance, heat resistance, and strength. The cover 1100 may be transparent so that the light source module 1200 is visible from the outside, and may be opaque. The cover 1100 may be formed through blow molding.

The light source module 1200 may be disposed on one surface of the heat radiator 1400. Thus, heat from the light source module 1200 is conducted to the heat sink 1400. The light source module 1200 may include a light emitting device package 1210, a connection plate 1230, and a connector 1250.

The member 1300 is disposed on the upper surface of the heat sink 1400, and has a plurality of light emitting device packages 1210 and guide grooves 1310 into which the connector 1250 is inserted. The guide groove 1310 corresponds to the substrate and connector 1250 of the light emitting device package 1210.

The surface of the member 1300 may be coated or coated with a light reflective material. For example, the surface of the member 1300 may be coated or coated with a white paint. The member 1300 reflects light that is reflected on the inner surface of the cover 1100 and returns to the direction of the light source module 1200 again in the direction of the cover 1100. Therefore, it is possible to improve the light efficiency of the lighting device according to the embodiment.

The member 1300 may be made of an insulating material, for example. The connection plate 1230 of the light source module 1200 may include an electrically conductive material. Therefore, electrical contact may be made between the heat sink 1400 and the connection plate 1230. The member 1300 may be formed of an insulating material to block electrical shorts between the connection plate 1230 and the heat sink 1400. The heat radiator 1400 receives heat from the light source module 1200 and heat from the power supply unit 1600 to radiate heat.

The holder 1500 closes the storage groove 1719 of the insulating portion 1710 of the inner case 1700. Therefore, the power supply unit 1600 accommodated in the insulating portion 1710 of the inner case 1700 is sealed. The holder 1500 has a guide projection 1510. The guide protrusion 1510 has a hole through which the protrusion 1610 of the power supply unit 1600 passes.

The power supply unit 1600 processes or converts an electrical signal provided from the outside and provides it to the light source module 1200. The power supply unit 1600 is accommodated in the storage groove 1719 of the inner case 1700 and is sealed inside the inner case 1700 by the holder 1500. The power supply unit 1600 may include a protrusion 1610, a guide 1630, a base 1650, and an extension 1670.

The guide portion 1630 has a shape protruding from one side of the base 1650 to the outside. The guide part 1630 may be inserted into the holder 1500. A plurality of parts may be disposed on one surface of the base 1650. The plurality of components include, for example, a DC converter that converts AC power provided from an external power source into DC power, a driving chip that controls the driving of the light source module 1200, and ESD for protecting the light source module 1200. (ElectroStatic discharge) may include a protection element, but is not limited thereto.

The extension 1670 has a shape protruding from the other side of the base 1650 to the outside. The extension portion 1670 is inserted into the connection portion 1750 of the inner case 1700 and receives an electrical signal from the outside. For example, the extension portion 1670 may be provided equal to or smaller than the width of the connection portion 1750 of the inner case 1700. Each end of the "+ wire" and the "- wire" may be electrically connected to the extension 1670, and the other end of the "+ wire" and the "- wire" may be electrically connected to the socket 1800.

The inner case 1700 may include a molding part together with the power supply part 1600. The molding part is a part in which the molding liquid is hardened, so that the power supply unit 1600 can be fixed inside the inner case 1700.

The embodiments have been mainly described above, but this is merely an example, and is not intended to limit the present invention. Those of ordinary skill in the art to which the present invention pertains are not exemplified above, without departing from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be implemented by modification. And differences related to these modifications and applications should be construed as being included in the scope of the invention defined in the appended claims.

100: light emitting element 110: substrate
115: buffer layer 120: light emitting structure
122: first conductive semiconductor layer 124: active layer
126: second conductive semiconductor layer 130: electron blocking layer
140: light-transmitting conductive layer 162: first electrode
166: second electrode 400: light emitting device package
500: video display device

Claims (6)

Board;
A light emitting structure disposed on the substrate and including an active layer of a multi-quantum well structure disposed between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer and the first conductivity type semiconductor layer;
A first electrode and a second electrode disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, respectively; And
The energy band gap of the quantum well structure is greater than the energy band gap of the quantum well structure of the multiple quantum well structure, and the energy band gap of the quantum well structure of the multiple quantum well structure A contact layer smaller than the energy band gap of the second conductivity type semiconductor layer,
The contact layer has a thickness of 0.5 to 3 nanometers,
A light emitting device in which the second conductivity type semiconductor layer is disposed between 0.5 nm and 3 nanometers between the contact layer and the second electrode. delete delete According to claim 1,
The contact layer is made of InGaN, a light emitting device doped with 2% to 10% of indium (In) in the contact layer. delete The method according to claim 1 or 4,
The contact layer is a light emitting device doped with a p-type.

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