KR101838022B1 - Light emitting device - Google Patents

Abstract

An embodiment is a semiconductor light emitting device comprising: a first conductivity type semiconductor layer; a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer; and a second conductivity type semiconductor layer disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, Wherein the barrier layer closest to the second conductivity type semiconductor layer comprises a first barrier layer and a second barrier layer, the energy band gap of the second barrier layer being Is smaller than the energy band gap of the first barrier layer.

Description

[0001]

An embodiment relates to a light emitting element.

BACKGROUND ART Light emitting devices such as a light emitting diode (LD) or a laser diode using semiconductor materials of Group 3-5 or 2-6 group semiconductors are widely used for various colors such as red, green, blue, and ultraviolet And it is possible to realize white light rays with high efficiency by using fluorescent materials or colors, and it is possible to realize low energy consumption, semi-permanent life time, quick response speed, safety and environment friendliness compared to conventional light sources such as fluorescent lamps and incandescent lamps .

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 embodiment provides a light emitting device capable of improving internal quantum efficiency and light output.

The light emitting device according to the embodiment includes a first conductive semiconductor layer, a second conductive semiconductor layer disposed on the first conductive semiconductor layer, and a second conductive semiconductor layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer Wherein the barrier layer closest to the second conductivity type semiconductor layer comprises a first barrier layer and a second barrier layer, wherein the barrier layer closest to the second conductivity type semiconductor layer comprises a first barrier layer and a second barrier layer, And the energy band gap is smaller than the energy band gap of the first barrier layer.

The second barrier layer may be closer to the second conductivity type semiconductor layer than the first barrier layer. The energy band gap of each of the first barrier layer and the second barrier layer may be constant.

The energy band gap of the first barrier layer may be constant and the energy band gap of the second barrier layer may decrease from the first conductivity type semiconductor layer toward the second conductivity type semiconductor layer. The composition of the well layers may be In _x Ga _(1-x) N (0.13 _{? X? 1} ).

The productivity of the first barrier layer is _{In y Ga (1-y)} N (0 <y≤0.01) , and wherein the productivity of the second barrier layer is _{In z Ga (1-z)} N (0.01 <z <0.13) Lt; / RTI &gt; The thickness of the first barrier layer may be greater than the thickness of the second barrier layer.

The light emitting device includes a substrate disposed under the first conductive type semiconductor layer, a conductive layer disposed on the second conductive type semiconductor layer, a first electrode disposed on the first conductive type semiconductor layer, And a second electrode disposed on the second electrode.

Or the light emitting element may include an ohmic layer disposed under the second conductive type semiconductor layer, a reflective layer disposed under the ohmic layer, a first electrode disposed on the first conductive type semiconductor layer, And may further include a passivation layer disposed thereon.

The embodiment can improve internal quantum efficiency and light output.

1 is a cross-sectional view of a light emitting device according to an embodiment.
2 is an energy band diagram according to the first embodiment of the active layer shown in FIG. 1
Fig. 3 shows an energy band diagram according to a second embodiment of the active layer shown in Fig.
4 shows an energy band diagram of a general active layer.
5 shows the light-emitting recombination of a general active layer upon current injection.
6 shows the light-emitting recombination of the active layer according to the embodiment at the time of current injection.
7 shows a light emitting device according to another embodiment.
8 shows a light emitting device package according to an embodiment.
9 is an exploded perspective view of a lighting device including a light emitting device package according to an embodiment.
10 shows a display device including a light emitting device package according to an embodiment.

Hereinafter, embodiments will be described with reference to the accompanying drawings.

In the description of the embodiments, it is to be understood that each layer (film), region, pattern or structure is formed "on" or "under" a substrate, each layer The terms " on "and " under " encompass both being formed" directly "or" indirectly " In addition, the criteria for above or below 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. Also, the size of each component does not entirely reflect the actual size. Hereinafter, a light emitting device according to an embodiment will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a light emitting device 100 according to an embodiment. Referring to FIG. 1, a light emitting device 100 includes a substrate 110, a light emitting structure 120, a conductive layer 130, a first electrode 142, and a second electrode 144.

The substrate 110 supports the light emitting structure 120. The substrate 110 may be any one of a sapphire substrate, a silicon substrate, a zinc oxide (ZnO) substrate, a nitride semiconductor substrate, or a template substrate in which at least one of GaN, InGaN, AlGaN, and AlInGaN is stacked. have.

The light emitting structure 120 is disposed on the substrate 110, and generates light. The light emitting structure 120 may include a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126 sequentially formed on a substrate 110. The light emitting structure 120 may be formed by partially etching the second conductivity type semiconductor layer 126, the active layer 124, and the first conductivity type semiconductor layer 122 to expose a portion of the first conductivity type semiconductor layer 122 .

A buffer layer (not shown) may be interposed between the substrate 110 and the light emitting structure 120 to mitigate the difference between the lattice constant and the thermal expansion coefficient between the substrate 110 and the light emitting structure 120, An undoped semiconductor layer (not shown) may be interposed between the buffer layer and the first conductivity type semiconductor layer 122 to improve the crystallinity of the conductivity type semiconductor layer 122.

At this time, the buffer layer may be grown at a low temperature, and the material may be a GaN layer or an AlN layer, but the present invention is not limited thereto. The n-type dopant is not doped, May be the same material as the first conductivity type semiconductor layer 122 except for having electrical conductivity.

The conductive layer 130 not only reduces the total reflection but also increases light extraction efficiency of the light emitted from the active layer 124 to the second conductivity type semiconductor layer 126 because of its good translucency.

The conductive layer 130 may be formed of a transparent conductive oxide such as indium tin oxide (ITO), tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), indium aluminum zinc oxide Indium Gallium Zinc Oxide), IGTO (Indium Gallium Tin Oxide), AZO (Aluminum Zinc Oxide), ATO (Antimony Tin Oxide), GZO (Gallium Zinc Oxide), IrOx, RuOx, RuOx / ITO, Ni, / Au, or Ni / IrOx / Au / ITO.

The first electrode 142 is disposed on the exposed first conductive semiconductor layer 122 and the second electrode 144 is disposed on the conductive layer 130.

The first conductive semiconductor layer 122 may be formed of a compound semiconductor such as a group III-V element, a group II-VI element, or the like. The first conductive type dopant (e.g., Si, Ge, Sn, Lt; / RTI &gt; The second conductivity type semiconductor layer 26 may be formed of a compound semiconductor such as a group III-V, a group II-VI, or the like, and the second conductivity type semiconductor layer 26 may include a second conductivity type dopant , Zn, Ca, Sr, Ba) may be doped.

For example, each of the first conductivity type semiconductor layer 122 and the second conductivity type semiconductor layer 126 may be formed of In _x Al _y Ga _1-xy N (0? _X? 1, 0? Y? 1), for example, at least one of GaN, AlN, AlGaN, InGaN, InN, InAlGaN, and AlInN.

The active layer 124 is disposed between the first conductivity type semiconductor layer 122 and the second conductivity type semiconductor layer. The active layer 124 is formed by energy generated during recombination of electrons provided from the first conductive type semiconductor layer 122 and holes provided from the second conductive type semiconductor layer 126 Light can be generated.

The active layer 124 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 + y? The active layer 124 may be a multiple quantum well (MQW) structure comprising alternating quantum well layers and quantum barrier layers. The active layer 124 may include at least one quantum well layer (QW1 to QWn, a natural number of n &gt; = 1) and a quantum barrier layer (QB1 to QBm,

For example, the quantum well layers (QW1 to QWn, n is a natural number of 1) are spaced apart from the first conductivity type semiconductor layer 122 in the direction of the second conductivity type semiconductor layer 126, and adjacent quantum well layers (QB1 to QBm, a natural number of m &gt; = 1) may be disposed between the quantum barrier layers.

Fig. 2 shows an energy band die diagram according to the first embodiment of the active layer 124 shown in Fig. Herein, the electron injection layer represents the first conductive type semiconductor layer 122, the hole injection layer represents the second conductive type semiconductor layer 126, and the active layer 124 may be disposed between the electron injection layer and the hole injection layer have.

Referring to FIG. 2, the active layer 124 includes a plurality of quantum well layers (QW1 to QWn, n? 2 is a natural number) and quantum barrier layers (QB1 to QBm, The quantum well layer and the quantum barrier layer may be alternately located. The energy band gap E2 of the quantum barrier layers QB1 to QBm and m≥1 is larger than the energy band gap E1 of the quantum well layers QW1 to QWn (E2> E1).

For example, the active layer 124 may include first through fourth quantum well layers QW1 through QWn, n = 4 and first through third quantum barrier layers QB1 through QBm, m = 3.

The first quantum well layer QW1, the second quantum well layer QW2, the third quantum well layer QW3, and the fourth quantum well layer QW4 may be adjacent to the electron injection layer in this order. The third quantum barrier layer QB3, the second quantum barrier layer QB2, and the first quantum barrier layer QB1 may be adjacent to the hole injection layer in this order. The energy band gaps of the quantum well layers (QW1 to QWn, n? 2 are natural numbers) may be equal to each other.

The energy band gap of the quantum barrier layer QBm (for example, m = 3) closest to the second conductivity type semiconductor layer 126 is shifted from the first conductivity type semiconductor layer 122 to the direction of the second conductivity type semiconductor layer 126 As shown in Fig.

The quantum barrier layer QBm (e.g., m = 3) closest to the second conductivity type semiconductor layer 126 may include a first barrier layer a1 and a second barrier layer a2. The energy band gap E31 of the first barrier layer a1 may be equal to or smaller than the energy band gap E2 of the remaining barrier layers QB1 to QBm-1. The energy band gap E31 of the first barrier layer a1 may be larger than the energy band gap E32 of the second barrier layer a2 (E32 <E31 &lt; E2).

The energy band gap E32 of the second barrier layer a2 is greater than the energy band gap E1 of the quantum well layers QW1 to QWn and n> 1 and is greater than the energy band gap E1 of the first barrier layer a1 E31) (E1 < E32 < E31). The energy bandgaps E31 and E32 of each of the first barrier layer a1 and the second barrier layer a2 may be constant.

The composition of each of the quantum well layers (QW1 to QWn, n> 1) and the quantum barrier layers (QB1 to QBm, m≥1) may be InGaN.

The composition of the quantum well layer (QW1 to QWn, natural number of n> 1) may be In _x Ga _(1-x) N (0.13 _{? X? 1} ). The composition of the first barrier layer (a1) is _{In y Ga (1-y)} N (0 <y≤0.01) , and the second composition of the barrier layer (a2) are _{In z Ga (1-z)} N (0.01 < z < 0.13).

The thickness of the first barrier layer a1 is greater than the thickness of the second barrier layer a2. In order to serve as a barrier, the thickness of the first barrier layer a1 must be greater than the thickness of the second barrier layer a2. If the thickness of the first barrier layer (a1) is too thin, it can not serve as a quantum barrier and the reliability of the light emitting device may deteriorate.

In general, the mobility of holes is very small as compared with the mobility of electrons. Therefore, the hole injected from the second conductivity type semiconductor layer into the active layer is difficult to move to the quantum well layer far from the second conductivity type semiconductor layer.

FIG. 4 shows an energy band diagram of a general active layer 410, and FIG. 5 shows a light emitting recombination of a general active layer 410 at the time of current injection.

4 and 5, the active layer 410 has a multiple quantum well structure including quantum well layers QW11 to QW14 and quantum barrier layers QB11 to QB13.

Since the mobility of holes is generally low at the time of current injection, the injection of holes into the entire quantum well layers QW11 to QW14 is not smooth and uniform. As a result, as shown in FIG. 4, light is mainly emitted from the last quantum well QW14 closest to the second conductivity type semiconductor layer. Accordingly, uniform light emission does not occur in the entire region of the active layer, and the light emitting efficiency of the light emitting device can be reduced.

However, since the energy band gap of the quantum barrier layer Qm closest to the second conductivity type semiconductor layer 126 according to the embodiment is stepped, it is injected from the second conductivity type semiconductor layer 126 to the active layer 124 The hole can be easily moved from the second conductivity type semiconductor layer 126 to a quantum well layer (e.g., QW1) located away from the second conductivity type semiconductor layer 126. [ The holes injected from the second conductivity type semiconductor layer 126 into the active layer 124 can be uniformly moved and distributed into the quantum well layers QW1 to QWn and n> 1.

6 shows the light-emitting recombination of the active layer 124 according to the embodiment upon current injection. Referring to FIG. 6, in the embodiment, holes are uniformly distributed to quantum well layers (QW1 to QWn, for example, n = 4), uniformly distributed holes are recombined with electrons injected from the first conductivity type semiconductor layer It can be seen that light emission by radiative recombination occurs in all of the first to fourth quantum well layers QW1 to QW4. Therefore, the embodiment can improve the internal quantum efficiency and the output power.

FIG. 3 shows an energy band diagram according to a second embodiment of the active layer 124 shown in FIG. 3, the quantum barrier layer QBm (for example, m = 3) closest to the second conductive semiconductor layer 126 includes a first barrier layer b1 and a second barrier layer b2 . The energy band gap E41 of the first barrier layer b1 may be equal to or less than the energy band gap E2 of the remaining barrier layers QB1 to QBm-1. The energy band gap E41 of the first barrier layer b1 may be larger than the energy band gap E42 of the second barrier layer b2 (E42 <E41 &lt; E2).

The energy band gap E42 of the second barrier layer b2 is greater than the energy band gap E1 of the quantum well layers QW1 to QWn and n> 1 and is greater than the energy band gap E1 of the first barrier layer b1 E41) (E1 < E42 < E41). The energy bandgaps E31 and E32 of the first barrier layer b1 may be constant. The energy band gap E42 of the second barrier layer b2 may decrease linearly or nonlinearly from the first conductivity type semiconductor layer 122 toward the second conductivity type semiconductor layer 126. [

The composition of the quantum well layer (QW1 to QWn, a natural number of n> 1), the first barrier layer (b1), and the second barrier layer (b2) may be InGaN.

The indium content contained in the first barrier layer b1 is constant and the indium content contained in the second barrier layer b2 is in the direction from the first conductivity type semiconductor layer 122 to the second conductivity type semiconductor layer 126 It can be increased linearly or nonlinearly.

7 shows a light emitting device 200 according to another embodiment.

Referring to FIG. 7, the light emitting device 200 includes a second electrode layer 205, a passivation layer 230, a light emitting structure 240, a passivation layer 250, and a first electrode 255.

The second electrode layer 205 includes a support substrate 210, a bonding layer 215, a barrier layer 218, a reflective layer 220, and an ohmic layer 225. The support substrate 210 supports the light emitting structure 240 and provides power to the light emitting structure 240 together with the first electrode 255. The support substrate 210 may be formed of a conductive material such as copper (Cu), gold (Au), nickel (Ni), molybdenum (Mo), copper-tungsten For example, Si, Ge, GaAs, ZnO, SiC).

The barrier layer 218 is disposed on the support substrate 210 and blocks the metal ions of the support substrate 110 from diffusing into the reflection layer 220 and the ohmic layer 225. For example, the barrier layer 218 may include at least one of Ni, Pt, Ti, W, V, Fe, and Mo and may be a single layer or a multilayer.

The bonding layer 215 is disposed between the supporting substrate 210 and the barrier layer 218. The bonding layer 215 is a bonding layer so that the reflective layer 220 and the ohmic layer 225 can be bonded to the supporting substrate 210. The bonding layer 215 may include at least one of a bonding metal, for example, Ti, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag or Ta.

The reflective layer 220 is disposed on the barrier layer 218. The reflective layer 220 reflects light incident from the light emitting structure 240, thereby improving light extraction efficiency. The reflective layer 220 may be formed of a metal or an alloy including at least one of a reflective material, for example, Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au and Hf.

The reflective layer 220 may be formed of a metal or an alloy and a transparent conductive material such as IZO, IZTO, IAZO, IGZO, IGTO, AZO, or ATO. IZO / Ag / Ni, AZO / Ag / Ni, or the like.

The ohmic layer 225 is disposed on the reflective layer 220. The ohmic layer 225 is in ohmic contact with the second conductivity type semiconductor layer 242 of the light emitting structure 240 to supply power to the light emitting structure 240 smoothly. The ohmic layer 225 may selectively use a light-transmitting conductive layer and a metal. For example, the ohmic layer 225 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc oxide (IZTO), indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO) tin oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO), IrO _x , RuO _x , RuO _x / ITO, Ni, Ag, Ni / IrO _x / IrO _x / Au / ITO.

The ohmic layer 225 is not formed separately and the material used for the reflective layer 220 may be selected as a material that makes an ohmic contact with the second conductive semiconductor layer 242 to achieve ohmic contact.

The protective layer 230 is disposed on the second electrode layer 205. The protective layer 230 can reduce the phenomenon that the interface between the light emitting structure 240 and the barrier layer 218 is peeled off and the reliability of the light emitting device 200 is deteriorated.

The protective layer 230 may be disposed in a peripheral region on the barrier layer 218. In the case where the barrier layer 218 is not formed, the protective layer 230 may be disposed in the peripheral region on the support substrate 210. The protective layer 230 may be formed of an electrically insulating material, for example, ZnO or SiO ₂ .

The light emitting structure 240 is disposed on the second electrode layer 205. The light emitting structure 240 may have a structure in which the second conductive semiconductor layer 242, the active layer 244, and the first conductive semiconductor layer 246 are sequentially stacked on the second electrode layer 205. The second conductivity type semiconductor layer 242 and the first conductivity type semiconductor layer may be the same as those described with reference to FIG.

The active layer 244 may be the same as that described in FIG. 1, and the energy band diagram of the active layer 244 may be the same as the embodiment shown in FIG. 2 or FIG.

2, the energy bandgap of the quantum barrier layer QBm (for example, m = 3) closest to the second conductivity type semiconductor layer 242 is smaller than the energy band gap of the first conductivity type semiconductor layer 122. In other words, The conductivity type semiconductor layer 126 can be reduced in a stepwise manner. Also, as shown in FIG. 3, the energy band gap E42 of the second barrier layer b2 may decrease linearly. Therefore, in the embodiment, since the light emission occurs uniformly in each of the quantum well layers QW1 to QW3 during current injection, the internal quantum efficiency can be improved and the light output can be improved.

The passivation layer 250 may be formed on the side of the light emitting structure 240 to electrically protect the light emitting structure 240. For example, the passivation layer 250 is _{SiO 2, SiO x, SiO x} N y, Si ₃ N ₄ , Al ₂ O ₃ .

The upper surface of the first conductive semiconductor layer 246 may be formed with a roughness 260 to increase light extraction efficiency. The first electrode 255 is disposed on the upper surface of the light emitting structure 240. The roughness 260 may be formed on the portion of the first conductive semiconductor layer 246 under the first electrode 255 or not.

8 shows a light emitting device package according to an embodiment. Referring to FIG. 8, the light emitting device package includes a package body 510, a first metal layer 512, a second metal layer 514, a light emitting device 520, a reflector 525, a wire 530, 540).

The package body 510 may have a cavity formed of side and bottom in one side region. At this time, the side wall of the cavity may be formed to be inclined. The package body 510 may be formed of a substrate having good insulating or thermal conductivity, such as a silicon based wafer level package, a silicon substrate, silicon carbide (SiC), aluminum nitride (AlN) Or may be a structure in which a plurality of substrates are stacked. The embodiments are not limited to the material, structure, and shape of the body described above.

The first metal layer 512 and the second metal layer 514 are disposed on the surface of the package body 510 so as to be electrically separated from each other in consideration of heat discharge or mounting of the light emitting device. The light emitting device 520 is electrically connected to the first metal layer 512 and the second metal layer 514. Here, the light emitting device 520 may be any one of the embodiments.

The reflection plate 525 is formed on the cavity side wall of the package body 510 to direct the light emitted from the light emitting element 520 in a predetermined direction. The reflection plate 525 is made of a light reflection material, and may be, for example, a metal coating or a metal flake.

The resin layer 540 surrounds the light emitting element 520 located in the cavity of the package body 510 to protect the light emitting element 520 from the external environment. The resin layer 540 is made of a colorless transparent polymer resin material such as epoxy or silicone. The resin layer 540 may include a phosphor to change the wavelength of light emitted from the light emitting device 520. The light emitting device package can mount at least one of the feet and the elements according to the above-described embodiments, but is not limited thereto.

A plurality of light emitting device packages according to embodiments may be arranged on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, and the like may be disposed on the light path of the light emitting device package. The light emitting device package, the substrate, and the optical member may function as a backlight unit.

Still another embodiment may be implemented as a display device, an indicating device, and a lighting system including the light emitting device or the light emitting device package described in the above embodiments. For example, the lighting system may include a lamp and a streetlight.

9 is an exploded perspective view of a lighting device including a light emitting device package according to an embodiment. 9, the illumination device according to the embodiment includes a light source 750 for projecting light, a housing 700 in which a light source 7500 is embedded, a heat dissipation unit 740 for emitting heat of the light source 750, And a holder 760 coupling the heat sink 750 and the heat dissipating unit 740 to the housing 700.

The housing 700 includes a socket coupling portion 710 coupled to an electric socket (not shown), and a body portion 730 connected to the socket coupling portion 710 and having a light source 750 embedded therein. One air flow hole 720 may be formed through the body portion 730.

A plurality of air flow holes 720 are provided on the body portion 730 of the housing 700 and one or more air flow holes 720 may be provided. The air flow port 720 may be disposed radially or in various forms on the body portion 730.

The light source 750 includes a plurality of light emitting device packages 752 provided on the substrate 754. [ The substrate 754 may have a shape that can be inserted into the opening of the housing 700 and may be made of a material having a high thermal conductivity to transmit heat to the heat dissipating unit 740 as described later. The plurality of light emitting device packages may be any one of the embodiments described above.

A holder 760 is provided below the light source 750, and the holder 760 may include a frame and other air flow holes. Although not shown, an optical member may be provided under the light source 750 to diffuse, scatter, or converge light projected from the light emitting device package 752 of the light source 750.

10 shows a display device including a light emitting device package according to an embodiment. 10, the display device 800 includes a bottom cover 810, a reflection plate 820 disposed on the bottom cover 810, light emitting modules 830 and 835 for emitting light, a reflection plate 820 A light guide plate 840 disposed in front of the light emitting module 830 and guiding the light emitted from the light emitting modules 830 and 835 to the front of the display device and prism sheets 850 and 860 disposed in front of the light guide plate 840, An image signal output circuit 872 connected to the display panel 870 and supplying an image signal to the display panel 870 and a display panel 870 disposed in front of the display panel 870, And a color filter 880 disposed therein. Here, the bottom cover 810, the reflection plate 820, the light emitting modules 830 and 835, the light guide plate 840, and the optical sheet may form a backlight unit.

The light emitting module comprises a light emitting device package 835 on a substrate 830. The substrate 830 may be a PCB or the like. The light emitting device package 835 may be a light emitting device package according to the embodiment.

The bottom cover 810 can house components within the display device 800. [ Also, the reflection plate 820 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 840 or on the front surface of the bottom cover 810 in a state of being coated with a highly reflective material .

Here, the reflection plate 820 can be made of a material having a high reflectance and can be used in an ultra-thin shape, and polyethylene terephthalate (PET) can be used.

The light guide plate 830 may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), or polyethylene (PE).

The first prism sheet 850 may be formed of a light-transmissive and elastic polymeric material on one side of the support film, and the polymer may have a prism layer in which a plurality of three-dimensional structures are repeatedly formed. Here, as shown in the drawings, the plurality of patterns may be provided with a floor and a valley repeatedly as stripes.

In the second prism sheet 860, the direction of the floor and the valley on one side of the supporting film may be perpendicular to the direction of the floor and the valley on one side of the supporting film in the first prism sheet 850. This is for evenly distributing the light transmitted from the light emitting module and the reflective sheet to the front surface of the display panel 1870.

Although not shown, a diffusion sheet may be disposed between the light guide plate 840 and the first prism sheet 850. The diffusion sheet may be made of polyester and polycarbonate-based materials, and the light incidence angle can be maximized by refracting and scattering light incident from the backlight unit. The diffusion sheet includes a support layer including a light diffusing agent, a first layer formed on the light exit surface (first prism sheet direction) and a light incidence surface (in the direction of the reflection sheet) . &Lt; / RTI &gt;

In an embodiment, the diffusion sheet, the first prism sheet 850, and the second prism sheet 1860 make up an optical sheet, which may be made of other combinations, for example a microlens array, A combination of one prism sheet and a microlens array, or the like.

The display panel 870 may include a liquid crystal display (LCD) panel, and may include other types of display devices that require a light source in addition to the liquid crystal display panel 860.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It can be seen 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.

110, 210: substrate 120, 240:
122, 246: first conductivity type semiconductor layer 124, 244:
126, 242: second conductivity type semiconductor layer 130: conductive layer
142, 255: first electrode 144: second electrode
205: second electrode layer 215: bonding layer
218: barrier layer 220: reflective layer
225: Ohmic layer 230: Protective layer
250: passivation layer 260: roughness
MQW: multiple quantum well structures QW1 to QW4: quantum well layers
QB1 to QB3: quantum barrier layers. a1, b1: a first barrier layer,
a2, b2: second barrier layer.

Claims (9)

A first conductive semiconductor layer;
A second conductive semiconductor layer disposed on the first conductive semiconductor layer; And
And an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer and including well layers and barrier layers,
The energy band gap of the last barrier layer closest to the second conductivity type semiconductor layer among the barrier layers gradually decreases from the first conductivity type semiconductor layer toward the second conductivity type semiconductor layer,
The energy band gap of each of the barrier layers except for the last barrier layer is maintained at a constant value,
Wherein the last barrier layer comprises a first barrier layer and a second barrier layer,
Wherein the second barrier layer is closer to the second conductivity type semiconductor layer than the first barrier layer,
Wherein an energy band gap of the first barrier layer is equal to or smaller than an energy band gap of each of the remaining barrier layers,
Wherein the energy band gap of the second barrier layer is smaller than the energy band gap of the first barrier layer, greater than the energy band gap of each of the well layers,
Wherein the thickness of the first barrier layer is greater than the thickness of the second barrier layer. delete The method according to claim 1,
Wherein the energy band gap of each of the first barrier layer and the second barrier layer is constant. The method according to claim 1,
Wherein an energy band gap of the first barrier layer is constant and an energy band gap of the second barrier layer is decreased in the direction of the second conductivity type semiconductor layer from the first conductivity type semiconductor layer. The method according to claim 1,
Wherein the composition of the well layers is In _x Ga _(1-x) N (0.13 _{? X? 1} ). 6. The method of claim 5,
The productivity of the first barrier layer is _{In y Ga (1-y)} N (0 <y≤0.01) , and wherein the productivity of the second barrier layer is _{In z Ga (1-z)} N (0.01 <z <0.13) Emitting device. delete delete delete

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