KR20150140025A - Light emitting device - Google Patents

Abstract

An embodiment of the present invention provides a light emitting device which comprises: an undoped semiconductor layer; an interlayer arranged on the undoped semiconductor layer; a light emitting structure which is arranged on the interlayer, and includes a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; and an electron blocking layer between the active layer and the second conductive semiconductor layer.

Description

[0001] LIGHT EMITTING DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a light emitting device, and more particularly to a quality improvement of a light emitting device.

GaN, and AlGaN are widely used for optoelectronics and electronic devices due to their advantages such as wide and easy bandgap energy.

Particularly, a light emitting device such as a light emitting diode (Ligit Emitting Diode) or a laser diode using a semiconductor material of a 3-5 group or a 2-6 group compound semiconductor has been widely used in various fields such as red, green, blue and ultraviolet It can realize various colors, and it can realize efficient white light by using fluorescent material or color combination. It has low power consumption, semi-permanent lifetime, fast response speed, safety, and environment compared to conventional light sources such as fluorescent lamps and incandescent lamps Affinity.

Therefore, a transmission module of the optical communication means, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting element capable of replacing a fluorescent lamp or an incandescent lamp Diode lighting, automotive headlights, and traffic lights.

The conventional light emitting device includes an un-doped semiconductor layer (un-GaN), a first conductive semiconductor layer (n-GaN), an active layer (MQW), and a second conductive semiconductor layer (p- GaN) may be formed on the first conductivity type semiconductor layer and the first and second electrodes may be disposed on the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, respectively.

The light emitting structure can be manufactured by growing a nitride-based semiconductor, for example, GaN on a substrate by a method such as MOCVD.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing the boing when a light emitting structure is grown on a conventional substrate. Fig.

When a gallium nitride epitaxial layer is grown, a high-temperature environment is formed inside the chamber. As shown in FIG. 1, when gallium nitride (GaN) is deposited on a substrate to form a light emitting structure, bowing May occur in a concave shape.

Conventionally, when a substrate having a diameter of 2 inches or 4 inches is used, there is no significant problem of wafer boiling. However, when a substrate having a diameter of 6 inches or more is used, the wafer boing can be remarkable.

As described above, if the wafer is bowed, deflection may remain in the light emitting device after dicing into each device unit. The warpage of the substrate or the light emitting structure in the light emitting device may cause deterioration in quality or electrical property Which may cause deterioration.

The embodiment is intended to prevent quality deterioration due to warping of the light emitting device and to prevent deterioration of electrical characteristics.

An embodiment includes an undoped semiconductor layer; An intermediate layer on the undoped semiconductor layer; A light emitting structure disposed on the intermediate layer, the light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; And an electron blocking layer between the active layer and the second conductivity type semiconductor layer.

Another embodiment includes an undoped semiconductor layer; A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; An intermediate layer between the first conductive semiconductor layer and the active layer; And an electron blocking layer between the active layer and the second conductivity type semiconductor layer.

The interlayer may comprise AlN.

The intermediate layer may have a thickness of from 2 nanometers to 10 nanometers.

The intermediate layer can be grown at a temperature of 800 ° C to 1200 ° C in ldT

The thickness of the intermediate layer may not be constant.

The intermediate layer may be composed of a plurality of layers.

In the light emitting device according to the embodiment, since the intermediate layer is formed on the undoped semiconductor layer or in the light emitting structure, stress due to the warping of the substrate is not transferred to the light emitting structure, so that the quality of the light emitting structure can be improved have.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a boehnite when a light emitting structure is grown on a conventional substrate,
2A is a sectional view of a first embodiment of a light emitting device,
FIG. 2B is a detailed view of the structure of the intermediate layer of FIG. 2A,
3A is a sectional view of a second embodiment of a light emitting device,
FIG. 3B is a detailed view of the structure of the intermediate layer of FIG. 3A,
4 is a view showing the effect of improving the bowing state of the light emitting device according to the embodiments,
5 is a view showing an embodiment of a light emitting device package including a light emitting device,
6 is a view illustrating an embodiment of a video display device including a light emitting device,
7 is a view showing an embodiment of a lighting device including a light emitting element.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

In the description of embodiments according to the present invention, in the case of being described as being formed "on or under" of each element, the upper (upper) or lower (lower) or under are all such that two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements. Also, when expressed as "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

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

The light emitting device 200a according to the embodiment includes a substrate 210, an undoped semiconductor layer 220, an intermediate layer 230, a first conductive semiconductor layer 242 and an active layer 244, A light emitting structure 240 including a semiconductor layer 246, an electron blocking layer 260, a light transmitting conductive layer 270, and a first electrode 282 and a second electrode 286.

The substrate 210 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 O ₃ can be used.

The lattice mismatch between GaN and AlGaN and sapphire is very large when the substrate 210 is formed of sapphire or the like and the light emitting structure 230 including GaN or the like is disposed on the substrate 210, The dislocation, melt-back, crack, pit, and surface morphology defects that deteriorate the crystallinity may occur because the difference in the thermal expansion coefficient is too large. , An undoped semiconductor layer 220 or a buffer layer (not shown) may be formed.

An intermediate layer 230 may be disposed between the undoped semiconductor layer 220 and the light emitting structure 240. The intermediate layer 230 can prevent the stress due to the bending of the substrate 210 from being directly transmitted from the undoped semiconductor layer 220 to the light emitting structure 240.

For example, when the undoped semiconductor layer 220 is made of GaN and the light emitting structure is made of GaN, the intermediate layer 240 may be made of AlN, and the thickness of the intermediate layer 240 may be 2 nanometers to 10 nanometers have. When the thickness of the intermediate layer 240 is less than 2 nanometers, it may not be enough to prevent transfer of the stress from the substrate 210, and it is sufficient to prevent stress transmission even when the intermediate layer 240 is not grown to 10 nanometers or more. For this purpose, the intermediate layer can be grown at a temperature of 800 ° C to 1200 ° C.

FIG. 2B is a detailed view illustrating the structure of the intermediate layer of FIG. 2A.

The substrate 210 and the undoped semiconductor layer 220 may have some of the boing generated during growth of the undoped semiconductor layer but may not transmit such boiling to the light emitting structure 240 on the intermediate layer 230.

Therefore, a portion of the intermediate layer 230 which is in contact with the underside undoped bar layer 230 is warped in some regions, the region in contact with the above light emitting structure 240 is flat, and the thickness of the intermediate layer 230 is And the thickness shown in Fig. 2A may be an average thickness.

The first conductive semiconductor layer 242 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a first conductive dopant to form a first conductive semiconductor layer. The first conductive semiconductor layer 242 is 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 + And may be formed of any one or more of AlGaN, GaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP, for example.

When the first conductive semiconductor layer 242 is an n-type semiconductor layer, the first conductive dopant may include n-type dopants such as Si, Ge, Sn, Se, and Te. The first conductive semiconductor layer 242 may be formed as a single layer or a multilayer, but the present invention is not limited thereto.

The active layer 244 is disposed on the upper surface of the first conductive semiconductor layer 242 and has a structure of a double well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW) structure , A quantum dot structure, or a quantum wire structure.

InGaN / InGaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and InGaN / AlGaN / / 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 conductive semiconductor layer 246 may be formed of a semiconductor compound on the surface of the active layer 244. [ The second conductive semiconductor layer 246 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a second conductive dopant. The second conductivity type semiconductor layer 246 is formed of a semiconductor material having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + y? And may be formed of any one or more of AlGaN, GaN AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

The second conductivity type semiconductor layer 246 may be a second conductivity type semiconductor layer doped with a second conductivity type dopant. When the second conductivity type semiconductor layer 246 is a p-type semiconductor layer, the second conductivity type dopant may be a Mg , Zn, Ca, Sr, Ba, and the like.

An electron blocking layer 260 may be disposed between the active layer 244 and the second conductive semiconductor layer 246. The electron blocking layer 260 may have a superlattice structure. For example, the superlattice may include AlGaN doped with a second conductive dopant, for example, AlGaN doped with 15% aluminum The GaN layer may have a thickness of 30 nm and GaN layers having different aluminum composition ratios may be alternately arranged.

A part of the active layer 244 and the first conductivity type semiconductor layer 242 are mesa-etched from the second conductivity type semiconductor layer 246 in a part of the light emitting structure 240 to form a part of the first conductivity type semiconductor layer 242 The surface is exposed.

The transmissive conductive layer 270 may be disposed on the second conductive semiconductor layer 246. The transmissive conductive layer 270 may be formed of indium-tin-oxide (ITO) The current spreading characteristic of the transmissive conductive layer 270 is poor and the current can be supplied from the second electrode 286 to the transmissive conductive layer 270.

A first electrode 282 and a second electrode 286 are respectively disposed on the surface of the exposed first conductive semiconductor layer 242 and the transmissive conductive layer 270. The first electrode 282 and the second electrode 286 286 may be formed as a single layer or a multilayer structure including at least one of aluminum (Al), titanium (Ti), chrome (Cr), nickel (Ni), copper (Cu), and gold (Not shown).

Although not shown, a passivation layer may be formed around the light emitting structure 240. The passivation layer may be made of an insulating material, specifically, an oxide or a nitride, and more specifically, a silicon oxide (SiO ₂ ) layer, an oxynitride layer, and an aluminum oxide layer.

3A is a cross-sectional view of a second embodiment of a light emitting device.

The light emitting device 200b according to the present embodiment is similar to the light emitting device 200a according to the first embodiment described above except that the intermediate layer 230 is formed between the first conductive semiconductor layer 242 and the active layer 244 There are differences placed.

Since the thickness of the intermediate layer 230 is as described above and the thickness may not be uniform due to the shape described above, a pattern may be formed on the surface of the substrate 210 to improve the light extraction efficiency. This pattern of the surface can also be applied to the light emitting device 200a according to the first embodiment described above.

FIG. 3B is a detailed view of the structure of the intermediate layer of FIG. 3A.

The intermediate layer may be composed of a plurality of layers {230-1, 230-2, ..., 230- (n-1), 203- ..., 230- (n-1), 203-n} may be grown, or the temperature may be varied during the growth of the intermediate layer or may be varied by varying the supply amounts of aluminum and nitrogen in the AlN.

The intermediate layer shown in FIG. 3B may also be applied to the light emitting device 200a of FIG. 2A.

4B is a view showing an effect of improving the bowing state of the light emitting device according to the embodiments.

It can be seen that the flatness of the light emitting device according to the embodiment is improved more flat than the flatness of the surface of the light emitting device according to the comparative example and the electrical characteristics are not degraded, _f may not be increased.

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

The light emitting device package 400 according to the embodiment includes a body 410 including a cavity, a first lead frame 421 and a second lead frame 422 provided on the body 410, The light emitting device 200a according to the above-described embodiments, which is installed in the cavity 410 and is electrically connected to the first lead frame 421 and the second lead frame 422, and a molding part 470 formed in the cavity, .

The body 410 may be formed of a silicon material, a synthetic resin material, or a metal material. If the body 410 is made of a conductive material such as a metal material, an insulating layer may be coated on the surface of the body 410 to prevent an electrical short 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 supply current to the light emitting device 200a. The first lead frame 421 and the second lead frame 422 can reflect the light generated from the light emitting device 200a to increase the light efficiency and reduce the heat generated from the light emitting device 200a to the outside It may be discharged.

The light emitting device 200a may be a light emitting device according to the embodiments described above.

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

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

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

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

6 is a view showing an embodiment of a video display device in which a light emitting device is disposed.

As shown in the drawing, the image display apparatus 500 according to the present embodiment includes a light source module, a reflection plate 520 on the bottom cover 510, and a reflection plate 520 disposed in front of the reflection plate 520, A first prism sheet 550 and a second prism sheet 560 disposed in front of the light guide plate 540 and a second prism sheet 560 disposed between the first prism sheet 560 and the second prism sheet 560, A panel 570 disposed in front of the panel 570 and a color filter 580 disposed in the front of the panel 570.

The light source module comprises a light emitting device package 535 on a circuit board 530. Here, the circuit board 530 may be a PCB or the like, and the light emitting device of the light emitting device package 535 is as described above.

The bottom cover 510 can house the components in the image display apparatus 500. The reflective plate 520 may be formed as a separate component as shown in the drawing, or may be provided on the rear surface of the light guide plate 540 or on the front surface of the bottom cover 510 with a highly reflective material.

The reflector 520 can be made of a material having a high reflectance and can be used in an ultra-thin shape, and a polyethylene terephthalate (PET) can be used.

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 LCD. Accordingly, the light guide plate 530 is made of a material having a good refractive index and transmittance. The light guide plate 530 may be formed of poly methylmethacrylate (PMMA), polycarbonate (PC), or polyethylene (PE). Also, if the light guide plate 540 is omitted, an air guide display device can be realized.

The first prism sheet 550 is formed on one side of the support film with a translucent and elastic polymer material. The polymer may have a prism layer in which a plurality of steric structures are repeatedly formed. As shown in the drawings, the plurality of patterns may be repeatedly provided with a stripe pattern.

In the second prism sheet 560, a direction of a floor and a valley of one side of the supporting film may be perpendicular to a direction of a floor and a valley of one side of the supporting film in the first prism sheet 550. This is for evenly distributing 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 constitute an optical sheet, which may be made of other combinations, for example, a microlens array or a combination of a diffusion sheet and a microlens array Or a combination of one prism sheet and a microlens array, or the like.

A liquid crystal display (LCD) panel may be disposed on the panel 570. In addition to the liquid crystal display panel 560, other types of display devices requiring a light source may be provided.

In the panel 570, a liquid crystal is positioned between glass bodies, and a polarizing plate is placed on both glass bodies to utilize the polarization of light. Here, the liquid crystal has an intermediate property between a liquid and a solid, and liquid crystals, which are organic molecules having fluidity like a liquid, are regularly arranged like crystals. The liquid crystal has a structure in which the molecular arrangement is changed by an external electric field And displays an image.

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

A color filter 580 is provided on the front surface of the panel 570 so that only the red, green, and blue light is transmitted through the panel 570 for each pixel.

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

The lighting apparatus according to the present embodiment may include a cover 1100, a light source module 1200, a heat sink 1200, a power supply unit 1600, an inner case 1700, and a socket 1800. In addition, the illumination device according to the embodiment may further include at least one of the member 1300 and the holder 1500, and the light source module 1200 may include the light emitting device package according to the above-described embodiments .

The cover 1100 may have a shape of a bulb or a hemisphere and may be provided in a shape in which the hollow is hollow and a part is opened. The cover 1100 may be optically coupled to the light source module 1200. For example, the cover 1100 can 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 coupled to the heat discharger 1200. The cover 1100 may have an engaging portion that engages with the heat discharger 1200.

The inner surface of the cover 1100 may be coated with a milky white paint. Milky white paints may contain a diffusing agent to diffuse light. The surface roughness of the inner surface of the cover 1100 may be formed larger than the surface roughness of the outer surface of the cover 1100. This is for sufficiently diffusing and diffusing light from the light source module 1200 and emitting it to the outside.

The cover 1100 may be made of glass, plastic, polypropylene (PP), polyethylene (PE), polycarbonate (PC), or the like. Here, polycarbonate is excellent in 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 by blow molding.

The light source module 1200 may be disposed on one side of the heat sink 1200. Accordingly, the heat from the light source module 1200 is conducted to the heat sink 1200. 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 discharger 1200 and has guide grooves 1310 into which the plurality of light emitting device packages 1210 and the connector 1250 are inserted. The guide groove 1310 corresponds to the substrate of the light emitting device package 1210 and the connector 1250.

The surface of the member 1300 may be coated or coated with a light reflecting material. For example, the surface of the member 1300 may be coated or coated with a white paint. The member 1300 reflects the light reflected by the inner surface of the cover 1100 and returns toward the light source module 1200 toward the cover 1100. Therefore, the light efficiency of the illumination device according to the embodiment can be improved.

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 discharger 1200 and the connection plate 1230. The member 1300 may be formed of an insulating material to prevent an electrical short circuit between the connection plate 1230 and the heat discharger 1200. The heat sink 1200 receives heat from the light source module 1200 and heat from the power supply unit 1600 to dissipate heat.

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

The power supply unit 1600 processes or converts an electric signal provided from the outside and provides the electric signal to the light source module 1200. The power supply unit 1600 is housed in the receiving 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 unit 1630, a base 1650, and an extension unit 1670.

The guide portion 1630 has a shape protruding outward from one side of the base 1650. The guide portion 1630 may be inserted into the holder 1500. A plurality of components may be disposed on one side of the base 1650. The plurality of components may include, for example, a DC converter for converting an AC power supplied from an external power source to a DC power source, a driving chip for controlling driving of the light source module 1200, an ESD (ElectroStatic discharge) protective device, and the like, but the present invention is not limited thereto.

The extension 1670 has a shape protruding outward from the other side of the base 1650. The extension portion 1670 is inserted into the connection portion 1750 of the inner case 1700 and receives an external electrical signal. For example, the extension portion 1670 may be provided to be equal to or smaller than the width of the connection portion 1750 of the inner case 1700. One end of each of the positive wire and the negative wire is electrically connected to the extension portion 1670 and the other end of the positive wire and the negative wire are electrically connected to the socket 1800 .

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

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

200a, 200b: light emitting element 210: substrate
220: undoped semiconductor layer 230: intermediate layer
240: light emitting structure 242: first conductivity type semiconductor layer
244: active layer 246: second conductivity type semiconductor layer
260: Electron barrier layer 270: Transparent conductive layer
282: first electrode 286: second electrode
400: light emitting device package 410: body
421: first lead frame 422: second lead frame
450: wire 470: molding part
480: phosphor 500: image display device

Claims (7)

An undoped semiconductor layer;
An intermediate layer on the undoped semiconductor layer;
A light emitting structure disposed on the intermediate layer, the light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; And
And an electron blocking layer between the active layer and the second conductivity type semiconductor layer. An undoped semiconductor layer;
A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer;
An intermediate layer between the first conductive semiconductor layer and the active layer; And
And an electron blocking layer between the active layer and the second conductivity type semiconductor layer. 3. The method according to claim 1 or 2,
Wherein the intermediate layer comprises AlN. 3. The method according to claim 1 or 2,
Wherein the intermediate layer has a thickness of 2 nanometers to 10 nanometers. 3. The method according to claim 1 or 2,
Wherein the intermediate layer is grown at a temperature of 800 ° C to 1200 ° C. 3. The method according to claim 1 or 2,
Wherein the intermediate layer has a constant thickness. 3. The method according to claim 1 or 2,
Wherein the intermediate layer comprises a plurality of layers.

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