KR20130074073A

KR20130074073A - Light emitting device

Info

Publication number: KR20130074073A
Application number: KR1020110141943A
Authority: KR
Inventors: 박수익; 임현수
Original assignee: 엘지이노텍 주식회사
Priority date: 2011-12-26
Filing date: 2011-12-26
Publication date: 2013-07-04

Abstract

Embodiments relate to a light emitting device, a method of manufacturing a light emitting device, a light emitting device package, and an illumination system.
The light emitting device according to the embodiment includes a substrate having an inclined surface; A first conductivity type semiconductor layer on one surface of the substrate corresponding to the inclined surface; An active layer on the first conductive semiconductor layer; And a second conductivity type semiconductor layer on the active layer.

Description

[0001] LIGHT EMITTING DEVICE [0002]

Embodiments relate to a light emitting device, a method of manufacturing a light emitting device, a light emitting device package, and an illumination system.

A light emitting device is a device in which electrical energy is converted into light energy, and various colors can be realized by adjusting the composition ratio of the compound semiconductor.

When a forward voltage is applied to a light emitting device, the electrons in the n-layer and the holes in the p-layer are coupled to emit energy corresponding to the energy gap between the conduction band and the valance band. It emits mainly in the form of heat or light, and emits in the form of light.

For example, nitride semiconductors have received great interest in the development of optical devices and high power electronic devices due to their high thermal stability and wide bandgap energy. In particular, blue light emitting devices, green light emitting devices, and ultraviolet light emitting devices using nitride semiconductors are commercially used and widely used.

The light emitting device may be classified into a horizontal type and a vertical type according to the position of the electrode.

In the horizontal light emitting device according to the prior art, a light emitting structure including n-GaN, an active layer, and p-GaN is formed on a sapphire substrate, and a PSS (Patterned Sapphire Substrate) is used to improve light extraction efficiency.

On the other hand, the light generated from the active layer (MQW) of the light emitting device transmits more than the reflection at the n-GaN and PSS interface when using PSS, and the transmitted light is reflected back to the epi layer of the light emitting structure from the reflective layer formed under the substrate. There is a problem in that absorption occurs while passing through an epi layer having a relatively low transmittance, thereby degrading light extraction efficiency.

Embodiments provide a light emitting device having an increased light extraction efficiency, a method of manufacturing a light emitting device, a light emitting device package, and an illumination system.

The light emitting device according to the embodiment includes a substrate having an inclined surface; A first conductivity type semiconductor layer on one surface of the substrate corresponding to the inclined surface; An active layer on the first conductivity type semiconductor layer; And a second conductivity type semiconductor layer on the active layer.

According to the light emitting device, the manufacturing method of the light emitting device, the light emitting device package and the lighting system according to the embodiment, the light extraction efficiency can be increased.

1 is a sectional view of a light emitting device according to a first embodiment;
2 is a cross-sectional view of a light emitting device according to a second embodiment;
3 to 6 are process cross-sectional views of a method of manufacturing a light emitting device according to the embodiment.
7 is a cross-sectional view of a light emitting device package according to the embodiment.
8 is a perspective view of a lighting unit according to an embodiment;
9 is a perspective view of a backlight unit according to the embodiment;

In the description of the embodiments, it is to be understood that each layer (film), area, pattern or structure may be referred to as being "on" or "under" the substrate, each layer Quot; on "and" under "are intended to include both" directly "or" indirectly " do. Also, the criteria for top, bottom, or bottom of each layer will be described with reference to the drawings.

The thickness and size of each layer in the drawings are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. In addition, the size of each component does not necessarily reflect the actual size.

(Example)

1 is a cross-sectional view of a light emitting device 100 according to a first embodiment.

The light emitting device 100 according to the embodiment includes a substrate 105 having an inclined surface S on a bottom surface thereof, a first conductive semiconductor layer 112 formed on the substrate 105, and the first conductive type. The active layer 114 and the second conductive semiconductor layer 116 may be included on the active layer 114 on the semiconductor layer 112.

The embodiment may include a reflective layer 160 formed on the inclined surface S of the bottom surface of the substrate 105.

The embodiment can improve the light extraction efficiency by preventing the emitted light from being absorbed by the epi layer by providing the inclined surface on the bottom by asymmetrically fabricating the symmetric substrate portion in the prior art.

For example, according to the prior art, most of the light generated from the quantum wells in the substrate using the PSS passes through the n-GaN and PSS interfaces and proceeds toward the sapphire.

In addition, in the conventional horizontal LED by the prior art, the probability that the reflected light is re-absorbed via the epi layer.

Accordingly, the embodiment may process the bottom portion of the substrate at an angle to improve light extraction efficiency by reducing reabsorption through the epi layer by changing the path of light.

In addition, according to the embodiment, since the bottom surface of the substrate has an inclination, the area bonded to the package body during the packaging process may be increased to increase contact force, and the heat dissipation area may be increased to increase the heat dissipation effect.

In addition, the embodiment may include a light extraction pattern 150 on the side of the substrate 105.

For example, the light extraction pattern 150 may be formed by processing a side surface of the substrate 105 or may form the light extraction pattern 150 on a side surface of the substrate 105 using a material different from that of the substrate 105. It may be.

When the light extraction pattern 150 is different from the material of the substrate 105, the light extraction pattern 150 may be formed of a material having a refractive index higher than that of the substrate 105 to prevent total reflection, thereby increasing light extraction efficiency. For example, the light extraction pattern 150 may be formed of silicon, but is not limited thereto.

In the embodiment, the light extraction pattern 150 may be formed on the side of the substrate facing the inclined surface of the substrate 105 to increase the external light extraction efficiency of the light reflected from the inclined surface of the substrate 105.

2 is a sectional view of the light emitting device 102 according to the second embodiment.

The second embodiment can employ the technical features of the first embodiment.

In the second embodiment, a plurality of inclined surfaces S of the bottom surface of the substrate may be formed.

For example, the inclined surface S of the substrate of the second embodiment may include a first inclined surface S1 and a second inclined surface S2, and the bottom surface of the substrate 105 may be inward by the inclined surface S. FIG. A concave portion, a cavity, or the like, such as a predetermined cone shape or a square cone shape, is formed so that light emitted from the active layer can be efficiently extracted to the side of the light emitting device.

In the second embodiment, the space in the substrate 105 formed by the inclined surface S of the substrate may be triangular in shape of the longitudinal section.

In the second embodiment, the reflective layer 160 may include a first reflective layer 161 on the first inclined surface S1 and a second reflective layer 162 on the second inclined surface S2.

In addition, the second embodiment may include a first light extraction pattern 150 on the first side of the substrate 105 and a second light extraction pattern 152 on the second side.

According to the light emitting device according to the embodiment, the light extraction efficiency can be increased.

Hereinafter, a method of manufacturing a light emitting device according to an embodiment will be described with reference to FIGS. Hereinafter, the present invention will be described with reference to a horizontal light emitting device, but the present invention is not limited thereto. When the substrate 105 is a conductive substrate, an inclined surface and a light extraction pattern may be formed on the conductive substrate.

First, the substrate 105 is prepared as shown in Fig. The substrate 105 may include a conductive substrate or an insulating substrate. For example, the substrate 105 may include sapphire (Al ₂ O ₃ ), SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga ₂ 0. ₃ May be used. Impurities on the surface may be removed by wet cleaning the substrate 105.

A patterned sapphire substrate (PSS) P may be formed on the substrate 105.

Next, a buffer layer (not shown) may be formed on the substrate 105. The buffer layer may mitigate lattice mismatch between the material of the light emitting structure 110 and the substrate 105, and the material of the buffer layer may be a Group III-V compound semiconductor such as GaN, InN, AlN, InGaN, AlGaN, InAlGaN. , AlInN may be formed of at least one.

Thereafter, the light emitting structure 110 is formed on the buffer layer (not shown). The light emitting structure 110 may include a first conductive semiconductor layer 112, an active layer 114, and a second conductive semiconductor layer 116.

The first conductivity type semiconductor layer 112 may be implemented as a group III-V compound semiconductor doped with a first conductivity type dopant, and when the first conductivity type semiconductor layer 112 is an N-type semiconductor layer, The first conductive dopant may be an N-type dopant and may include Si, Ge, Sn, Se, or Te, but is not limited thereto.

The first conductive semiconductor layer 112 may include 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 + . For example, the first conductive semiconductor layer 112 may be formed of one or more of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, .

The first conductive semiconductor layer 112 may form an N-type GaN layer using a chemical vapor deposition method (CVD), molecular beam epitaxy (MBE), or sputtering or hydroxide vapor phase epitaxy (HVPE). . In addition, the first conductive semiconductor layer 112 may include a silane containing n-type impurities such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and silicon (Si). The gas SiH ₄ may be injected and formed.

In an embodiment, a current spreading layer (not shown) may be formed on the first conductivity type semiconductor layer 112. The current diffusion layer may be an undoped GaN layer, but is not limited thereto. The current spreading layer may have a thickness of 50 nm to 200 nm, but is not limited thereto.

In addition, the embodiment may form an electron injection layer (not shown) on the current diffusion layer. The electron injection layer may be a first conductivity type gallium nitride layer. For example, the electron injection layer may be the electron injection efficiently by being doped at a concentration of the n-type doping element ^{6.0x10 18 atoms / cm 3 ~ 8.0x10} 18 atoms / cm 3.

In addition, the embodiment can form a strain control layer (not shown) on the electron injection layer. For example, a strain control layer formed of In _y Al _x Ga _(1-xy) N (0? X? 1, 0? _Y? 1) / GaN or the like can be formed on the electron injection layer. The strain control layer may effectively alleviate stresses that are odd due to lattice mismatch between the first conductivity-type semiconductor layer 112 and the active layer 114.

Further, as the strain control layer is repeatedly laminated in at least six cycles having compositions such as first In _x1 GaN and second In _x2 GaN, more electrons are collected at a low energy level of the active layer 114, The probability of recombination of holes is increased and the luminous efficiency can be improved.

Thereafter, an active layer 114 is formed on the strain control layer.

The active layer 114 has an energy band inherent in the active layer (light emitting layer) material because electrons injected through the first conductive semiconductor layer 112 and holes injected through the second conductive semiconductor layer 116 formed thereafter meet each other. It is a layer that emits light with energy determined by.

The active layer 114 may be formed of at least one of a single quantum well structure, a multi quantum well structure (MQW), a quantum-wire structure, or a quantum dot structure. For example, the active layer 114 may be formed with a multiple quantum well structure by injecting trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and trimethyl indium gas (TMIn) But is not limited thereto.

The well layer / barrier layer of the active layer 114 is formed of one or more pair structures of InGaN / GaN, InGaN / InGaN, GaN / AlGaN, InAlGaN / GaN, GaAs (InGaAs) / AlGaAs, GaP (InGaP) / AlGaP. But it is not limited thereto. The well layer may be formed of a material having a lower band gap than the band gap of the barrier layer.

In the embodiment, an electron blocking layer (not shown) is formed on the active layer 114 to serve as electron blocking and cladding of the active layer, thereby improving the luminous efficiency. For example, the electron blocking layer may be formed of an Al _x In _y Ga _(1-xy) N (0? _X _{? 1, 0?} _Y _{? 1} ) semiconductor, And may be formed to a thickness of about 100 A to about 600 A, but the present invention is not limited thereto.

The electron blocking layer may be formed of a superlattice of Al _z Ga _(1-z) N / GaN (0? _Z ? 1), but is not limited thereto.

The electron blocking layer can efficiently block the electrons that are ion-implanted into the p-type and overflow, and increase the hole injection efficiency. For example, the electron blocking layer can effectively prevent electrons that are overflowed by ion implantation of Mg in a concentration range of about 10 ¹⁸ to 10 ²⁰ / cm ³ , and increase the hole injection efficiency.

The second conductive type semiconductor layer 116 is a second conductive type dopant is doped -5-group three-V compound semiconductor, for _{example, In x Al y Ga 1 -x-} y N (0≤x≤1, 0≤y And a semiconductor material having a composition formula of ≦ 1, 0 ≦ x + y ≦ 1). When the second conductivity type semiconductor layer 116 is a P type semiconductor layer, the second conductivity type dopant may include Mg, Zn, Ca, Sr, Ba, or the like as a P type dopant.

The second conductivity type semiconductor layer 116 is a bicetyl cyclone containing p-type impurities such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and magnesium (Mg) in the chamber. Pentadienyl magnesium (EtCp ₂ Mg) {Mg (C ₂ H ₅ C ₅ H ₄ ) ₂ } may be injected to form a p-type GaN layer, but is not limited thereto.

In an exemplary embodiment, the first conductive semiconductor layer 112 may be an N-type semiconductor layer, and the second conductive semiconductor layer 116 may be a P-type semiconductor layer, but is not limited thereto. In addition, a semiconductor, for example, an N-type semiconductor layer (not shown) having a polarity opposite to that of the second conductive type may be formed on the second conductive type semiconductor layer 116. Accordingly, the light emitting structure 110 may be implemented as any one of an N-P junction structure, a P-N junction structure, an N-P-N junction structure, and a P-N-P junction structure.

Next, the transparent electrode 120 may be formed on the second conductivity type semiconductor layer. For example, the translucent electrode 120 may be formed by stacking a single metal, a metal alloy, a metal oxide, or the like in multiple layers so as to efficiently inject a carrier. For example, the light transmissive electrode 120 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO), or IGTO. (indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), 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 At least one of Au, Hf, and the like may be formed, and the material is not limited thereto.

Next, a portion of the light transmissive electrode 120, the second conductive semiconductor layer 116, and the active layer 114 is removed to expose the first conductive semiconductor layer 112.

Next, the first electrode 131 and the second electrode 132 may be formed on the exposed first conductive semiconductor layer 112 and the translucent electrode 120, respectively.

Next, as shown in FIG. 4, a light extraction pattern 150 may be formed on the side surface of the substrate 105.

When the light extraction pattern 150 is different from the material of the substrate 105, the light extraction pattern 150 may be attached to the side surface of the substrate 105 or the light emitting structure 110 by a heat treatment, an adhesive material, or a compression method. It is not.

In the embodiment, the light extraction pattern 150 may be formed on the side of the substrate facing the inclined surface S of the substrate to be formed thereafter, thereby increasing external light extraction efficiency of light reflected from the inclined surface of the substrate 105. have.

In addition, the light extraction pattern 150 may be formed of a light transmissive material and may be formed of a material that transmits and emits to the outside rather than reflecting light.

In addition, in the exemplary embodiment, when the light extraction pattern 150 is disposed in a line shape horizontally on the bottom surface of the substrate 105, an effect on side light extraction efficiency may be increased by increasing lateral diffuse reflection of light.

Next, in an embodiment, the inclined surface S may be formed on the bottom surface of the substrate 105. The process of forming the inclined surface S may be performed before the process of forming the light extraction pattern 150.

The process of forming the inclined surface S of the substrate may be performed by a process such as grinding or etching, but is not limited thereto.

Next, as illustrated in FIG. 5, the reflective layer 160 may be formed on the inclined surface S of the bottom surface of the substrate 105. The reflective layer 160 may be formed of a metal layer including Al, Ag, or an alloy containing Al or Ag, but is not limited thereto.

6 is a cross-sectional view of the light emitting device 102 according to the second embodiment. In the second embodiment, a plurality of inclined surfaces S of the bottom surface of the substrate may be formed.

In the second embodiment, light extraction patterns 150 and 152 may be formed on both side surfaces, thereby increasing side light extraction efficiency.

According to the light emitting device and the light emitting device according to the embodiment, the light extraction efficiency can be improved.

7 is a view illustrating a light emitting device package in which the light emitting device according to the embodiments is installed.

The light emitting device package 200 according to the embodiment includes a package body 205, a third electrode layer 213 and a fourth electrode layer 214 provided on the package body 205, a package body 205, And a molding member 230 surrounding the light emitting device 100. The light emitting device 100 is electrically connected to the third electrode layer 213 and the fourth electrode layer 214,

The package body 205 may include a silicon material, a synthetic resin material, or a metal material, and an inclined surface may be formed around the light emitting device 100.

The third electrode layer 213 and the fourth electrode layer 214 are electrically isolated from each other and provide power to the light emitting device 100. The third electrode layer 213 and the fourth electrode layer 214 may function to increase light efficiency by reflecting the light generated from the light emitting device 100, And may serve to discharge heat to the outside.

The light emitting device 100 may be a light emitting device of the horizontal type illustrated in FIG. 1 or 2, but is not limited thereto.

The light emitting device 100 may be mounted on the package body 205 or on the third electrode layer 213 or the fourth electrode layer 214.

The light emitting device 100 may be electrically connected to the third electrode layer 213 and / or the fourth electrode layer 214 by a wire, flip chip, or die bonding method. In the exemplary embodiment, the light emitting device 100 is connected to the third electrode layer 213 and the fourth electrode layer 214 by wire.

The molding member 230 surrounds the light emitting device 100 to protect the light emitting device 100. In addition, the molding member 230 may include a phosphor 232 to change the wavelength of light emitted from the light emitting device 100.

A light guide plate, a prism sheet, a diffusion sheet, a fluorescent sheet, and the like, which are optical members, may be disposed on a path of light emitted from the light emitting device package. The light emitting device package, the substrate, and the optical member may function as a backlight unit or function as a lighting unit. For example, the lighting system may include a backlight unit, a lighting unit, a pointing device, a lamp, and a streetlight.

8 is a perspective view 1100 of a lighting unit according to an embodiment. However, the lighting unit 1100 of FIG. 8 is an example of a lighting system, but is not limited thereto.

In the embodiment, the lighting unit 1100 is connected to the case body 1110, the light emitting module unit 1130 installed on the case body 1110, and the case body 1110 and receive power from an external power source. It may include a terminal 1120.

The case body 1110 may be formed of a material having good heat dissipation characteristics. For example, the case body 1110 may be formed of a metal material or a resin material.

The light emitting module unit 1130 may include a substrate 1132 and at least one light emitting device package 200 mounted on the substrate 1132.

The substrate 1132 may be a circuit pattern printed on an insulator, and for example, a general printed circuit board (PCB), a metal core PCB, a flexible PCB, a ceramic PCB, and the like. It may include.

In addition, the substrate 1132 may be formed of a material that reflects light efficiently, or the surface may be formed of a color that reflects light efficiently, for example, white, silver, or the like.

The at least one light emitting device package 200 may be mounted on the substrate 1132. Each of the light emitting device packages 200 may include at least one light emitting diode (LED) 100. The light emitting diodes 100 may include colored light emitting diodes emitting red, green, blue, or white colored light, and UV light emitting diodes emitting ultraviolet (UV) light.

The light emitting module unit 1130 may be disposed to have a combination of various light emitting device packages 200 to obtain color and luminance. For example, a white light emitting diode, a red light emitting diode, and a green light emitting diode may be combined to secure high color rendering (CRI).

The connection terminal 1120 may be electrically connected to the light emitting module unit 1130 to supply power. In an embodiment, the connection terminal 1120 is coupled to the external power source by a socket, but is not limited thereto. For example, the connection terminal 1120 may be formed in a pin shape and inserted into an external power source, or may be connected to the external power source by a wire.

9 is an exploded perspective view 1200 of a backlight unit according to an embodiment. However, the backlight unit 1200 of FIG. 9 is an example of an illumination system, but is not limited thereto.

The backlight unit 1200 according to the embodiment includes a light guide plate 1210, a light emitting module unit 1240 that provides light to the light guide plate 1210, a reflective member 1220 under the light guide plate 1210, and the light guide plate. 1210, a bottom cover 1230 for accommodating the light emitting module unit 1240 and the reflective member 1220, but is not limited thereto.

The light guide plate 1210 serves to diffuse light into a surface light source. The light guide plate 1210 may be made of a transparent material such as acrylic resin such as PMMA (polymethyl methacrylate), polyethylene terephthalate (PET), polycarbonate (PC), cycloolefin copolymer (COC), and polyethylene naphthalate Resin. &Lt; / RTI >

The light emitting module unit 1240 provides light to at least one side of the light guide plate 1210 and ultimately serves as a light source of a display device in which the backlight unit is installed.

The light emitting module 1240 may be in contact with the light guide plate 1210, but is not limited thereto. Specifically, the light emitting module 1240 includes a substrate 1242 and a plurality of light emitting device packages 200 mounted on the substrate 1242. The substrate 1242 is mounted on the light guide plate 1210, But is not limited to.

The substrate 1242 may be a printed circuit board (PCB) including a circuit pattern (not shown). However, the substrate 1242 may include not only a general PCB, but also a metal core PCB (MCPCB), a flexible PCB (FPCB), and the like.

The plurality of light emitting device packages 200 may be mounted on the substrate 1242 such that a light emitting surface on which the light is emitted is spaced apart from the light guiding plate 1210 by a predetermined distance.

The reflective member 1220 may be formed under the light guide plate 1210. The reflection member 1220 reflects the light incident on the lower surface of the light guide plate 1210 so as to face upward, thereby improving the brightness of the backlight unit. The reflective member 1220 may be formed of, for example, PET, PC, or PVC resin, but is not limited thereto.

The bottom cover 1230 may receive the light guide plate 1210, the light emitting module 1240, and the reflective member 1220. For this purpose, the bottom cover 1230 may be formed in a box shape having an opened upper surface, but the present invention is not limited thereto.

The bottom cover 1230 may be formed of a metal material or a resin material, and may be manufactured using a process such as press molding or extrusion molding.

The features, structures, effects and the like described in the embodiments are included in at least one embodiment and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Accordingly, the contents of such combinations and modifications should be construed as being included in the scope of the embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. It can be seen that the modification and application of branches are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

100: light emitting element, S: slope
105: substrate, 112: first conductive semiconductor layer
114: active layer, 116: second conductive semiconductor layer, 160: reflective layer

Claims

A substrate having an inclined surface;
A first conductivity type semiconductor layer on one surface of the substrate corresponding to the inclined surface;
An active layer on the first conductive semiconductor layer; And
And a second conductive semiconductor layer on the active layer.

The method according to claim 1,
A light emitting device comprising a light extraction pattern on the side of the substrate.

The method of claim 2,
The light extraction pattern is formed on the side of the substrate facing the inclined surface of the substrate.

The method of claim 2,
The refractive index of the light extraction pattern is
A light emitting device equal to the refractive index of the substrate.

The method of claim 2,
The refractive index of the light extraction pattern is
A light emitting device larger than the refractive index of the substrate.

The method according to claim 1,
The light emitting device further comprises a reflective layer formed on the inclined surface of the substrate.

The method according to claim 1,
The inclined surface of the substrate
A plurality of light emitting elements formed.

The method of claim 7, wherein
The inclined surface of the substrate may include a first inclined surface and a second inclined surface,
The bottom surface of the substrate by the inclined surface has a light emitting device having a concave portion of a cone shape or a square pyramid inside.

The method of claim 7, wherein
And a space in the substrate formed by the inclined surface of the substrate is triangular in shape in its longitudinal section.