KR20130101221A

KR20130101221A - Light emitting device

Info

Publication number: KR20130101221A
Application number: KR1020120022193A
Authority: KR
Inventors: 이현기; 이상현
Original assignee: 엘지이노텍 주식회사
Priority date: 2012-03-05
Filing date: 2012-03-05
Publication date: 2013-09-13

Abstract

A light emitting device according to an embodiment includes a first conductive semiconductor layer; A second conductivity type semiconductor layer; And an active layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, wherein the active layer is formed by alternately stacking a well layer and a barrier layer at least once, and wherein the barrier layer comprises: a first region; A second region positioned in the direction of the first conductivity type semiconductor layer with respect to the first region, and a third region positioned in the direction of the second conductivity type semiconductor layer with respect to the first region, respectively, In one barrier layer, the energy bandgap of the first region is greater than the energy bandgap of the second region and the energy bandgap of the third region.

Description

[0001] LIGHT EMITTING DEVICE [0002]

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.

1 is a diagram illustrating an energy band diagram of a light emitting diode according to the prior art.

The light emitting diode according to the prior art includes an active layer 10 composed of a multi-quantum well structure (MQW), wherein the barrier layer 12 of the active layer 10 binds electrons and holes (carriers) into the well layer 11. It is composed of GaN or InGaN containing a small amount of In.

However, at this time, stress is generated in the active layer 10 due to the difference in the In content between the well layer 11 and the barrier layer 12, and thus polarization occurs to overlap the wave function of the electron and the wave function of the hole. Interfere with being.

In addition, when the barrier layer 12 is composed of InGaN containing a small amount of In, the energy band gap of the barrier layer 12 is smaller than the energy band gap of n-GaN or p-GaN. Electrons or holes are present, and these electrons or holes do not bind to the well layer 11 and may not contribute to light emission.

Therefore, it is necessary to reduce the band warping phenomenon of the barrier layer caused by the polarization phenomenon due to the stress and to improve the binding rate of the carrier to the well layer.

The embodiment attempts to improve the luminous efficiency of the light emitting device.

In the at least one barrier layer, an In content may increase from the first region to the second region and the third region, respectively.

In content of the second region and In content of the third region may be the same.

In content of the second region and In content of the third region may be different from each other.

In the at least one barrier layer, the energy bandgap from the first region to the second region may be reduced in a stepped shape, a straight line, or a curved shape.

In the at least one barrier layer, the energy bandgap from the first region to the third region may be reduced in a stepped shape, a straight line, or a curved shape.

The curved form may include a concave curve toward the center of the energy bandgap or a convex curve in a direction away from the center of the energy bandgap.

The well layer and the barrier layer of the active layer may have a composition of In _x Ga ₁ _- _x N and In _y Ga ₁ _- _y N (0 <x <1, 0 = y <1, x> y), respectively.

In the at least one barrier layer, the first region, the second region and the third region are In _y1 Ga ₁ _- _y1 N, In _y2 Ga ₁ _- _y2 N and In _y3 Ga ₁ _- _y3 N (0≤ y1 ≦ 0.03, 0.03 ≦ y2, y3 ≦ 0.07, y1 <y2, y1 <y3).

In the barrier layer closest to the second conductive semiconductor layer, an energy band gap of the first region and an energy band gap of the third region may be the same.

An electron blocking layer may be further included between the active layer and the second conductive semiconductor layer, and an energy band gap of the electron blocking layer may be greater than an energy band gap of the barrier layer.

The energy band gap of the well layer of the active layer may be smaller than the energy band gap of the second region of the barrier layer and the third region of the barrier layer.

The display device may further include a first electrode on the first conductive semiconductor layer and a second electrode on the second conductive semiconductor layer.

The display device may further include a transparent electrode layer positioned between the second conductive semiconductor layer and the second electrode.

According to the embodiment, the stress of the well layer and the barrier layer may be reduced to alleviate the polarization phenomenon, and the crystalline quality of the active layer may be improved.

In addition, by increasing the binding force of the carrier to the well layer to increase the recombination rate of electrons and holes can be improved the luminous efficiency of the light emitting device.

1 is a view showing an energy band diagram of a light emitting diode according to the prior art,
2 and 3 are side cross-sectional views of light emitting devices according to one embodiment;
4 is a diagram showing an energy band diagram of a light emitting device according to the first embodiment;
5 is a diagram illustrating an energy band diagram of a light emitting device according to a second embodiment;
6 is a diagram illustrating an energy band diagram of a light emitting device according to a third embodiment;
7 is a diagram illustrating an energy band diagram of a light emitting device according to a fourth embodiment;
8 is a diagram illustrating an energy band diagram of a light emitting device according to a fifth embodiment;
9 is a diagram showing an energy band diagram of a light emitting device according to a sixth embodiment;
10A is a graph showing an actual energy band diagram of a light emitting device according to the related art, and FIG. 10B is a graph showing an actual energy band diagram according to an embodiment.
FIG. 11 is a graph illustrating comparison between recombination rates of electrons and holes in a well layer of a light emitting device according to the related art and an embodiment;
12 is a view showing an embodiment of a light emitting device package including a light emitting device according to the embodiment,
FIG. 13 is a view showing an embodiment of a head lamp in which a light emitting device is disposed;
14 is a diagram illustrating an example of a display device in which a light emitting device package is disposed, according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In the description of the embodiment 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.

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.

2 and 3 are side cross-sectional views of light emitting devices according to one embodiment. 2 illustrates a horizontal light emitting device, and FIG. 3 illustrates a vertical light emitting device.

The light emitting device according to the exemplary embodiment may include a first conductive semiconductor layer 120, a second conductive semiconductor layer 140, and the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140. The active layer 130 of the.

The light emitting device includes a light emitting diode (LED) using a plurality of compound semiconductor layers, for example, a semiconductor layer of Group 3-Group 5 elements, and the LED is a colored LED or UV that emits light such as blue, green, or red. It may be an LED. The emitted light of the LED may be implemented using various semiconductors, but is not limited thereto.

The first conductive semiconductor layer 120, the active layer 130, and the second conductive semiconductor layer 140 may be collectively referred to as a light emitting structure.

The light emitting structure may be, for example, metal organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD), plasma chemical vapor deposition (PECVD), or molecular beam growth method (PECVD). Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), or the like, and the like, but are not limited thereto.

The first conductive semiconductor layer 120 may be formed of a semiconductor compound, for example, a compound semiconductor such as a group III-V element or a group II-VI element. In addition, the first conductivity type dopant may be doped. When the first conductivity type semiconductor layer 120 is an n type semiconductor layer, the first conductivity type dopant may include Si, Ge, Sn, Se, or Te as an n type dopant, but is not limited thereto. In addition, when the first conductivity type semiconductor layer 120 is a p type semiconductor layer, the first conductivity type dopant may include Mg, Zn, Ca, Sr, or Ba as a p type dopant.

The first conductive semiconductor layer 120 includes a semiconductor material having a composition formula of Al _x In _y Ga _(1-xy) N (0? X? 1, 0? _Y? 1, 0? _X + y? 1) can do. The first conductive semiconductor layer 120 may be formed of one or more of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP and InP.

The second conductivity-type semiconductor layer 140 may be formed of a semiconductor compound, for example, may be formed of a group III-V compound semiconductor doped with a second conductivity type dopant. The second conductivity type semiconductor layer 140 has a composition formula of In _x Al _y Ga ₁ _-x- _y N (0? X? 1, 0? _Y? 1, 0? _X + y? 1) Semiconductor material. When the second conductive semiconductor layer 140 is a p-type semiconductor layer, the second conductive dopant may include Mg, Zn, Ca, Sr, or Ba as a p-type dopant. In addition, when the second conductive semiconductor layer 140 is an n-type semiconductor layer, the second conductive dopant may include Si, Ge, Sn, Se, or Te as an n-type dopant, but is not limited thereto.

In the present exemplary embodiment, the first conductive semiconductor layer 120 may be an n-type semiconductor layer, and the second conductive semiconductor layer 140 may be a p-type semiconductor layer. Alternatively, the first conductive semiconductor layer 120 may be a p-type semiconductor layer, and the second conductive semiconductor layer 140 may be an n-type semiconductor layer.

In addition, an n-type semiconductor layer (not shown) may be formed on the second conductive semiconductor layer 140 when a semiconductor having a polarity opposite to that of the second conductive type, for example, the second conductive semiconductor layer is a p-type semiconductor layer. have. Accordingly, the light emitting structure 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.

The active layer 130 is positioned between the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140.

The active layer 130 is a layer in which electrons and holes meet each other to emit light having energy determined by an energy band inherent to an active layer (light emitting layer) material. For example, the first conductive semiconductor layer 120 may be n In the case of the semiconductor layer and the second conductivity-type semiconductor layer 140 is a p-type semiconductor layer, electrons are supplied from the first conductivity-type semiconductor layer 120 and holes are provided in the second conductivity-type semiconductor layer 140. Can be provided.

The active layer 130 may be formed of a multi quantum well structure (MQW). For example, the active layer 130 may be injected with trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and trimethyl indium gas (TMIn) to form a multi-quantum well structure. It is not limited.

A conductive clad layer (not shown) may be formed on and / or below the active layer 130. The conductive clad layer may be formed of a semiconductor having a band gap wider than the band gap of the barrier layer of the active layer. For example, the conductive clad layer may comprise GaN, AlGaN, InAlGaN or a superlattice structure. In addition, the conductive clad layer may be doped with n-type or p-type.

In the active layer 130, the well layer 131 and the barrier layer 132 are alternately stacked at least once, and the energy band gap of the well layer 131 is smaller than the energy band gap of the barrier layer 132.

2 and 3 illustrate that the well layer 131 and the barrier layer 132 are alternately stacked four times as an example, but is not limited thereto.

The barrier layer 132 of the active layer 130 may include a first region 132a, a second region 132b positioned in the direction of the first conductivity type semiconductor layer 120 around the first region 132a, Each of the third regions 132c is positioned in the direction of the second conductivity-type semiconductor layer 140 with respect to the first region 132a.

That is, the active layer 130 includes at least one barrier layer 132, and each of the barrier layers 132 includes a first region 132a, a second region 132b, and a third region 132c.

In the at least one barrier layer 132, the energy bandgap of the first region 132a is greater than the energy bandgap of the second region 132b and larger than the energy bandgap of the third region 132c.

Here, the first region 132a of the barrier layer 130 refers to the center of each of the barrier layers 130, and the second region 132b of the barrier layer 130 refers to the first region 132a. The outer portion in the direction of the first conductivity type semiconductor layer 120 is indicated, and the third region 132c of the barrier layer 130 refers to the outer portion in the direction of the second conductivity type semiconductor layer 140 with respect to the first region 132a. Defined by pointing.

The energy band gap of the active layer 130 may be controlled by the In content of the materials constituting the well layer 131 and the barrier layer 132. That is, as the In content increases, the energy band gap becomes smaller, and as the In content decreases, the energy band gap may increase.

In at least one barrier layer 132, the In content may increase from the first region 132a to the first region 132b and from the first region 132a to the third region 132c.

In this case, the In content of the second region 132b and the In content of the third region 132c may be the same as or different from each other.

In an embodiment, the energy bandgap of the barrier layer 132 is not the same everywhere, but the In content gradually increases from the first region 132a to the second region 132b and the third region 132c so that the energy bandgap is increased. By setting it to decrease, the polarization phenomenon caused by the stress caused by the sudden change of the In content between the well layer 131 and the barrier layer 132 is controlled, and carriers such as electrons and holes are transferred to the well layer 131. Induction of binding can improve the luminous efficiency of the light emitting device.

The energy bandgap may decrease continuously or discretely from the first region 132a to the second region 132b of the barrier layer 132 and from the first region 132a to the third region 132c. Can be.

That is, the energy bandgap from the first region 132a to the second region 132b may be discretely reduced in a step shape, for example, or may be continuously reduced in a straight or curved form.

In addition, the energy band gap from the first region 132a to the third region 132b may be discretely reduced, for example, in a step shape, or may be continuously reduced in a straight or curved form.

In this case, the curved shape may mean a curved shape concave toward the center of the energy band gap or a convex curve shape away from the center of the energy band gap.

However, the energy bandgap from the first region 132a to the second region 132b and the energy bandgap from the first region 132a to the third region 132c do not necessarily have to decrease symmetrically. It may be reduced in other forms.

The well layer 131 / barrier layer 132 of the active layer 130 is formed of In _x Ga ₁ _- _x N / In _y Ga ₁ _- _y N (0 <x <1, 0 = y <1, x> y). It may have a composition. That is, since the energy band gap of the well layer 131 is smaller than the energy band gap of the barrier layer 132, the In content x of the well layer 131 is greater than the In content y of the barrier layer 132. In addition, the barrier layer 132 may be made of only GaN without In.

In some embodiments, when the light emitting device is a UV LED, the well layer and the barrier layer of the active layer may be made of a material including Al.

In one example, the first region 132a, the second region 132b and the third region 132c of the barrier layer 132 are In _y1 Ga ₁ _- _y1 N, In _y2 Ga ₁ _- _y2 N and In _{y3, respectively.} Ga ₁ _- _y3 N (0≤y1≤0.03, 0.03≤y2, y3≤0.07, y1 <y2, y1 <y3) may have a composition, but is not limited thereto.

That is, the In content of the first region 132a is less than the In content of each of the second region 132b and the third region 132c (y1 <y2, y1 <y3), and In of the first region 132a. The content y1 is 0-3%. In contents y2 and y3 of the second region 132b and the third region 132c may be 3 to 7%, respectively. If the barrier layer 132 contains more In than this, the crystallinity of the active layer 130 may be lowered.

In this case, the In content y2 of the second region 132b and the In content y3 of the third region 132c may be the same as or different from each other.

The well layer 131 of the active layer 130 has a composition of In _x Ga ₁ _-x N (0 <x <1). For example, the In content x of the well layer 131 may be 13 to 14%.

Therefore, since the In content of the well layer 131 is greater than the In content of the second region 132b and the third region 132c of the barrier layer 132, the energy band gap of the well layer 131 may be defined as the barrier layer ( It may be smaller than the energy band gap of the second region 132b and the third region 132c of 132.

In addition, among the barrier layers 132, the barrier layer 132 nearest to the second conductivity-type semiconductor layer 140 has an energy band gap of the first region 132a and an energy band gap of the third region 132c. May be the same.

An electron blocking layer (EBL) 150 may be positioned between the active layer 130 and the second conductive semiconductor layer 140.

Since the electrons in the carrier have good mobility in the electron blocking layer 150, electrons provided from the first conductivity-type semiconductor layer 120 do not contribute to light emission, and the electron blocking layer 150 crosses the active layer 130 to the second conductivity-type semiconductor layer 140. It can act as a potential barrier to prevent it from escaping and causing leakage current.

The energy bandgap of the electron blocking layer 150 is larger than the energy bandgap of the barrier layer 132 of the active layer 130, and may be made of a single layer of AlGaN or a multilayer of AlGaN / GaN, InAlGaN / GaN. It is not limited.

The light emitting structure including the first conductive semiconductor layer 120, the active layer 130, and the second conductive semiconductor layer 140 is grown on the growth substrate 110.

The growth substrate 110 may be formed of a material suitable for semiconductor material growth, a material having excellent thermal conductivity. For example, at least one of sapphire (Al ₂ O ₃ ), SiC, GaAs, GaN, ZnO, Si, GaP, InP, Ge, and Ga ₂ O ₃ may be used as the growth substrate 110. The growth substrate 110 may be wet-cleaned to remove impurities on the surface.

The undoped semiconductor layer 115 may be first grown before the first conductive semiconductor layer 120 is grown on the growth substrate 110.

The undoped semiconductor layer 115 is a layer formed to improve the crystallinity of the first conductivity type semiconductor layer 120, and is lower than the first conductivity type semiconductor layer 120 because the first conductivity type dopant is not doped. It may be the same as the first conductive semiconductor layer 120 except for having conductivity.

The first electrode 155 is positioned on the first conductive semiconductor layer 120, and the second electrode 160 is positioned on the second conductive semiconductor layer 140.

The first electrode 155 and the second electrode 160 each include at least one of aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), copper (Cu), or gold (Au). It may be formed in a single layer or a multilayer structure.

In the case of the horizontal light emitting device as illustrated in FIG. 2, a portion of the second conductive semiconductor layer 140, the active layer 130, and the first conductive semiconductor layer 120 are selectively etched and exposed. The first electrode 155 is positioned on the surface of 120.

In the case of the vertical light emitting device as illustrated in FIG. 3, the conductive support substrate 210 is positioned under the second conductive semiconductor layer 140, and the conductive support substrate 210 may serve as a second electrode.

The conductive support substrate 210 may be formed of a material having high electrical conductivity and thermal conductivity. For example, the conductive support substrate 210 may be formed of molybdenum (Mo), silicon (Si), tungsten (W), copper (Cu), or aluminum (Al) as a base substrate having a predetermined thickness. It may be made of a material selected from the group or alloys thereof, and also, gold (Au), copper alloy (Cu Alloy), nickel (Ni), copper-tungsten (Cu-W), carrier wafers (eg GaN, Si, Ge, GaAs, ZnO, SiGe, SiC, SiGe, Ga ₂ O _3, etc.) or a conductive sheet may be optionally included.

Referring to FIG. 2 again, the transparent electrode layer 170 may be positioned between the second conductivity-type semiconductor layer 140 and the second electrode 160.

The transparent electrode layer 170 is to improve the electrical contact between the second conductivity-type semiconductor layer 140 and the second electrode 160, and a light transmissive conductive layer and a metal may be selectively used. For example, ITO (indium) tin oxide), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), Antimony tin oxide (ATO), gallium zinc oxide (GZO), IZO (IZO Nitride), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), ZnO, IrOx, RuOx, NiO, RuOx / ITO, Ni / Including at least one of IrOx / Au, or Ni / IrOx / Au / ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, Hf It may be formed, and is not limited to these materials.

Referring to FIG. 3, a reflective layer 230 may be positioned between the second conductive semiconductor layer 140 and the conductive support substrate 210 of the light emitting structure.

The reflective layer 230 may effectively reflect light generated by the active layer 130 to greatly improve the light extraction efficiency of the light emitting device.

A separate transparent electrode layer 220 may be positioned between the reflective layer 230 and the second conductive semiconductor layer 140, but the reflective layer 230 is formed of a material in ohmic contact with the second conductive semiconductor layer 140. In this case, the transparent electrode layer 220 may not be formed separately.

The light emitting structure having the reflective layer 230 and / or the transparent electrode layer 220 and the conductive support substrate 210 may be coupled to each other by the bonding layer 215.

The bonding layer 215 may include a barrier metal or a bonding metal, and may include, for example, at least one of Ti, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag, or Ta. It does not limit to this.

A roughness pattern may be formed on a surface of the first conductivity type semiconductor layer 120 of the light emitting structure. The roughness pattern may be formed by performing a photo enhanced chemical (PEC) etching method or an etching process using a mask pattern. The roughness pattern is to increase the external extraction efficiency of the light generated by the active layer 130, and may have a regular period or an irregular period.

In addition, the passivation layer 240 may be formed on at least a portion of the side surface of the light emitting structure and the first conductivity type semiconductor layer 120.

The passivation layer 240 is made of oxide or nitride to protect the light emitting structure. As an example, the passivation layer 240 may be formed of a silicon oxide (SiO ₂ ) layer, an oxynitride layer, and an aluminum oxide layer.

Hereinafter, an embodiment will be described in more detail with reference to the respective figures showing an energy band diagram.

4 is a diagram illustrating an energy band diagram of the light emitting device according to the first embodiment.

The light emitting device according to the first embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

Each of the barrier layers 132 included in the active layer 130 has a first region 132a, which is a central portion, and a second region located in the direction of the first conductivity-type semiconductor layer 120 with respect to the first region 132a. 132b) and a third region 132c positioned in a direction of the second conductivity type semiconductor layer 140 with respect to the first region 132a.

In the at least one barrier layer 132, the energy band gap of the first region 132a is greater than the energy band gap of the second region 132b and the energy band gap of the third region 132c.

In this case, the energy bandgap of the first region 132a and the energy bandgap of the third region 132c may be the same as or different from each other.

The energy band gap of the active layer 130 may be controlled by the In content of the materials constituting the well layer 131 and the barrier layer 132. That is, as the In content increases, the energy band gap becomes smaller, and as the In content decreases, the energy band gap becomes larger.

Therefore, the In content is increased from the first region 132a to the second region 132b of the barrier layer 132 and from the first region 132a to the third region 132c to increase the energy band gap. May decrease.

In content control of the well layer 131 and the barrier layer 132 of the active layer 130, a method of controlling the supply amount of TMI (Trimethyl Indium) which is a source gas of In when the active layer 130 is grown is used, or The method of volatilizing In at a high temperature by controlling the growth temperature of 130) may be used, but is not limited thereto.

The barrier layer of the active layer is generally composed of a material that does not contain In or contains a small amount of In compared to the well layer in order to bind carriers such as electrons or holes to the well layer. Stress occurred in the liver, which caused a polarization (polarization), there was a problem that the recombination rate of electrons and holes is reduced.

In an embodiment, the well layer and the barrier layer are reduced by gradually increasing the In content from the first region 132a of the barrier layer 132 to the second region 132b and the third region 132c to reduce the energy band gap. Polarization can be alleviated by reducing stress caused by rapid change in In content of liver. Therefore, compared with the related art, the area where the wave function of the electron and the wave function of the hole overlap is increased, thereby increasing the recombination rate of the electron and the hole.

In addition, due to the structure of the barrier layer 132 according to the embodiment, since the energy of the carrier located in the upper region of the barrier layer 132 having a high energy level can be lowered, the binding to the well layer 131 can be increased. The luminous efficiency of the device can be further increased.

In FIG. 4, as an example, the well layer 131 and the barrier layer 132 are alternately stacked four times, but is not limited thereto.

In FIG. 4, as an example, in all four barrier layers 132, the energy band gap decreases from the first region 132a to the second region 132b and the third region 132c. It is not limited.

Referring to FIG. 4, as an example, when the first conductivity type semiconductor layer 120 is made of GaN, an energy band gap between the first conductivity type semiconductor layer 120 and the first region 132a of the barrier layer 132 may be used. As such, the first region 132a of the barrier layer 132 may be formed of only GaN without In.

That is, the In content of the first region 132a is less than the In content of each of the second region 132b and the third region 132c (y1 <y2, y1 <y3), and the In content of the first region 132a. y1 is 0 to 3%. In contents y2 and y3 of the second region 132b and the third region 132c may be 3 to 7%, respectively, but are not limited thereto. If the barrier layer 132 contains more In than this, the crystallinity of the active layer 130 may be lowered.

The energy band gap of the first region 132a and the third region 132c of the barrier layer 132 may be larger than the energy band gap of the well layer 131. Therefore, the In content of the first region 132a and the third region 132c of the barrier layer 132 may be less than the In content of the well layer 131.

The energy bandgap from the first region 132a to the second region 132b of the barrier layer 132 and the energy bandgap from the first region 132a to the third region 132c may decrease continuously. It may be reduced in the form of a convex curve in a direction away from the center (C) of the energy band gap.

Since the energy band gap is controlled by the In content, the In content continuously increases from the first region 132a to the second region 132b and from the first region 132a to the third region 132c. Can be.

If the energy bandgap from the first region 132a to the second region 132b and the energy bandgap from the first region 132a to the third region 132c decrease gradually, the well layer 131 Stress between the barrier layer 132 and the barrier layer 132 may be alleviated, and thus the crystallinity quality of the active layer 130 may be improved and the recombination rate of electrons and holes may be increased.

In FIG. 4, as an example, the energy band gap from the first region 132a to the second region 132b and the energy band gap from the first region 132a to the third region 132c are symmetric with each other. Although shown as decreasing, it may be reduced while having different shapes without being symmetrical.

In addition, in FIG. 4, as an example, there is a difference in the energy band gap between the second region 132b or the third region 132c of the barrier layer 132 and the well layer 131, and thereafter, the first region. Although the energy band gap is gradually changed toward 132a, the energy band gap may be set to gradually change from an adjacent portion of the well layer 131 and the barrier layer 132. In this case, the second region 132b or the third region 132c may mean an adjacent portion between the well layer 131 and the barrier layer 132.

An electron blocking layer 150 may be positioned between the active layer 130 and the second conductive semiconductor layer 140.

5 is a diagram illustrating an energy band diagram of a light emitting device according to a second embodiment.

Duplicates of the above-described embodiments will not be described again, and the following description will focus on differences.

The light emitting device according to the second embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

The difference between the second embodiment and the first embodiment is that the energy band from the first region 132a 'to the second region 132b' in the barrier layer 132 closest to the second conductivity-type semiconductor layer 140. The gap is reduced, but the energy band gap from the first region 132a 'to the third region 132c' may not be reduced.

In the barrier layer 132 ′ closest to the second conductivity-type semiconductor layer 140, the energy bandgap from the first region 132a ′ to the third region 132c ′ is the same as in the other barrier layer 132. When decreasing, the junction surface of the barrier layer 132 ′ and the second conductivity-type semiconductor layer 140 and the junction of the barrier layer 132 ′ and the electron blocking layer 150 when the electron blocking layer 150 is present. Because the energy bands are curved in the plane, losses due to inadvertent carrier binding can occur.

Therefore, in the second embodiment, the In content is increased in the direction of the first region 132a 'to the third region 132c' in the barrier layer 132 'closest to the second conductivity-type semiconductor layer 140. The energy band gap can be maintained without increasing.

In FIG. 5, for example, the energy band gaps of the first region 132a 'and the third region 132c' of the barrier layer 132 'closest to the second conductivity-type semiconductor layer 140 are shown to be exactly the same. However, the present invention is not limited thereto, and energy band gaps of the first region 132a 'and the third region 132c' may be adjusted within a range capable of alleviating polarization while preventing loss due to unintended carrier binding. Can be. As described above, the control of the energy band gap may be achieved by controlling the In content during the growth of the barrier layer 132 ′.

In the second embodiment, the energy conduction band gap from the first region 132a of the barrier layer 132 to the second region 132a and the third region 132c decreases in a continuous curved form, thereby providing a second conductivity type. Although the energy band gap from the first region 132a 'of the barrier layer 132' closest to the semiconductor layer 140 toward the third region 132c 'is maintained, this is merely an example. The reduction form of the energy band gap from the first region 132a to the second region 132a and the third region 132c of the barrier layer 132 may vary depending on the embodiment, but is not limited thereto.

6 is a diagram illustrating an energy band diagram of a light emitting device according to a third embodiment.

Duplicates of the above-described embodiment will not be described again, and the following description will focus on differences.

The light emitting device according to the third embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

In addition, in the barrier layer 132 ′ closest to the second conductivity-type semiconductor layer 140, the energy band gap from the first region 132a ′ to the second region 132b ′ is reduced, but the first region ( The energy band gap from 132a 'to the third region 132c' may not be reduced.

In a third embodiment, the energy bandgap of the first region 132a of the barrier layer 132 may be smaller than the energy bandgap of the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140. .

Since the energy band gap decreases as the In content increases, the first region 132a of the barrier layer 132 may have a higher In content than the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140. And, may have a composition of In _y1 Ga ₁ _- _y1 N (0 <y1 <1), as an example may have a composition of In _y1 Ga ₁ _- _y1 N (0 <y1 <0.3), but is not limited thereto.

When the energy bandgap of the first region 132a of the barrier layer 132 is smaller than the energy bandgap of the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140, the barrier layer 132 Carriers are also present on the first region 132a, and these carriers have high energy.

In the third embodiment, the energy bandgap from the first region 132a to the second region 132b of the barrier layer 132 and the energy bandgap from the first region 132a to the third region 132c. Since the energy band gap of the first region 132a of the barrier layer 132 is smaller than that of the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140, The carriers on the first region 132a lose energy and bind to the well layer 131, thereby improving the recombination rate of electrons and holes.

In the third embodiment, the energy bandgap of the first region 132a of the barrier layer 132 is smaller than the energy bandgap of the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140. Although the energy bandgap from the first region 132a to the second region 132a and the third region 132c of the layer 132 has been described as decreasing in the form of a continuous curve, this is only one example, and the barrier The reduction form of the energy bandgap from the first region 132a to the second region 132a and the third region 132c of the layer 132 may vary depending on the embodiment, but is not limited thereto.

7 is a diagram illustrating an energy band diagram of the light emitting device according to the fourth embodiment.

The light emitting device according to the fourth embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

The energy bandgap from the first region 132a to the second region 132b of the barrier layer 132 and the energy bandgap from the first region 132a to the third region 132c may decrease discretely. Can be reduced in the form of stairs. The shape, height, width, and the like of the stairs may vary depending on the embodiment.

In this case, the first region 132a may mean a region that is the center of the barrier layer 132 and has no change in the energy band gap.

Since the energy bandgap is controlled by In content control, the In content is discretely from the first region 132a to the second region 132b and from the first region 132a to the third region 132c. Can be increased.

8 is an energy band diagram of a light emitting device according to a fifth embodiment.

The light emitting device according to the fifth embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

The energy bandgap from the first region 132a to the second region 132b of the barrier layer 132 and the energy bandgap from the first region 132a to the third region 132c may decrease continuously. It may be reduced in the form of a convex curve toward the center (C) of the energy band gap.

Since the energy band gap is controlled by the In content control, the In content continuously increases from the first region 132a to the second region 132b and from the first region 132a to the third region 132c. Can be.

9 is an energy band diagram of a light emitting device according to a sixth embodiment.

The light emitting device according to the sixth embodiment includes a first conductivity type semiconductor layer 120, an active layer 130, and a second conductivity type semiconductor layer 140, and the active layer 130 includes a well layer 131 and a barrier. Layers 132 may have multiple quantum well structures stacked alternately at least once.

The energy bandgap from the first region 132a to the second region 132b of the barrier layer 132 and the energy bandgap from the first region 132a to the third region 132c may decrease continuously. And can decrease linearly.

Since the energy band gap is controlled by the In content control, the In content continuously increases from the first region 132a to the second region 132b and from the first region 132a to the third region 132c. The increment may be constant.

10A is a graph showing an actual energy band diagram of a light emitting device according to the related art, and FIG. 10B is a graph showing an actual energy band diagram according to an embodiment.

Referring to FIG. 10B according to the embodiment, it can be seen that the carrier has a structure that binds the carrier on the top of the barrier layer to the well layer, as compared with the energy bandgap structure of the barrier layer shown in FIG. 10A. .

That is, according to the embodiment, the bending of the energy band of the barrier layer caused by the stress due to the difference in In content is reduced, and the binding of the carrier to the well layer is strengthened by the energy bandgap structure of the barrier layer, thereby recombining electrons and holes. As the rate is increased, the luminous efficiency of the light emitting device can be improved.

FIG. 11 is a graph illustrating recombination rates of electrons and holes in a well layer of a light emitting device according to the related art and an exemplary embodiment.

The x axis of the graph is the distance (nm) from the first conductivity type semiconductor layer to the second conductivity type semiconductor layer, and the y axis is the recombination rate of electrons and holes (cm ⁻³ s ⁻¹ ).

Referring to FIG. 11, it can be seen that the recombination rate of electrons and holes in the well layer is increased in the case of (a) the conventional case (b).

12 is a view illustrating an embodiment of a light emitting device package including the light emitting device according to the embodiments.

The light emitting device package 300 according to the exemplary embodiment may include a body 310, a first lead frame 321 and a second lead frame 322 installed on the body 310, and the body 310. The light emitting device 100 according to the above-described embodiments is electrically connected to the first lead frame 321 and the second lead frame 322, and a molding part 340 formed in the cavity. A cavity may be formed in the body 310.

The body 310 may be formed including a silicon material, a synthetic resin material, or a metal material. When the body 310 is made of a conductive material such as a metal material, although not shown, an insulating layer is coated on the surface of the body 310 to prevent an electrical short between the first and second lead frames 321 and 322. Can be.

The first lead frame 321 and the second lead frame 322 are electrically separated from each other, and supplies a current to the light emitting device 100. In addition, the first lead frame 321 and the second lead frame 322 may increase the light efficiency by reflecting the light generated by the light emitting device 100, heat generated by the light emitting device 100 Can be discharged to the outside.

The light emitting device 100 may be installed on the body 310 or may be installed on the first lead frame 321 or the second lead frame 322. In the present embodiment, the first lead frame 321 and the light emitting device 100 are directly energized, and the second lead frame 322 and the light emitting device 100 are connected through a wire 330. The light emitting device 100 may be connected to the lead frames 321 and 322 by a flip chip method or a die bonding method in addition to the wire bonding method.

The molding part 340 may surround and protect the light emitting device 100. In addition, a phosphor 350 is included on the molding part 340 to change the wavelength of light emitted from the light emitting device 100.

The phosphor 350 may include a garnet-based phosphor, a silicate-based phosphor, a nitride-based phosphor, or an oxynitride-based phosphor.

For example, the garnet-base phosphor is _{YAG (Y 3 Al 5 O 12} : Ce 3 +) or TAG: may be a _{(Tb 3 Al 5 O 12 Ce} 3 +), wherein the silicate-based phosphor is (Sr, Ba, Mg, Ca) ₂ SiO ₄ : Eu ² ⁺ , and the nitride phosphor may be CaAlSiN ₃ : Eu ² ⁺ containing SiN, and the oxynitride phosphor may be Si ₆ _- _x _{Al x O x N 8 -x:} Eu 2 + (0 <x <6) can be.

Light in the first wavelength region emitted from the light emitting device 100 is excited by the phosphor 250 and converted into light in the second wavelength region, and the light in the second wavelength region passes through a lens (not shown). The light path can be changed.

A plurality of light emitting device packages according to the embodiment may be arranged on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, and the like, which are optical members, may be disposed on an optical path of the light emitting device package. Such a light emitting device package, a substrate, and an optical member can function as a light unit. Another embodiment may be implemented as a display device, an indicator device, or a lighting system including the semiconductor light emitting device or the light emitting device package described in the above embodiments, and for example, the lighting system may include a lamp or a street lamp. .

Hereinafter, a head lamp and a backlight unit will be described as an embodiment of the lighting system in which the above-described light emitting device or light emitting device package is disposed.

FIG. 13 is a diagram illustrating an embodiment of a head lamp in which a light emitting device is disposed.

Referring to FIG. 13, after the light emitted from the light emitting module 710 in which the light emitting device is disposed is reflected by the reflector 720 and the shade 730, the light may pass through the lens 740 to face the vehicle body. have.

The light emitting module 710 may be provided with a plurality of light emitting devices on a circuit board, but is not limited thereto.

FIG. 14 is a diagram illustrating a display device in which a light emitting device package according to an embodiment is disposed.

Referring to FIG. 14, the display device 800 according to the embodiment is disposed in front of the light emitting modules 830 and 835, the reflector 820 on the bottom cover 810, and the reflector 820. A light guide plate 840 for guiding light emitted from the front of the display device, a first prism sheet 850 and a second prism sheet 860 disposed in front of the light guide plate 840, and the second prism sheet ( And a color filter 880 disposed in front of the panel 870 disposed in front of the panel 870.

The light emitting module includes the above-described light emitting device package 835 on the circuit board 830. Here, the circuit board 830 may be a PCB or the like, and the light emitting device package 835 is the same as that described with reference to FIG.

The bottom cover 810 may house the components in the display device 800. The reflection plate 820 may be formed as a separate component as shown in the drawing, or may be formed to be coated on the rear surface of the light guide plate 840 or on the front surface of the bottom cover 810 with a highly reflective material Do.

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 840 scatters 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 830 is made of a material having a good refractive index and transmittance. The light guide plate 830 may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), or polyethylene (PE). An air guide system is also available in which the light guide plate is omitted and light is transmitted in a space above the reflective sheet 820.

The first prism sheet 850 is formed on one side of the support film with a transparent and elastic polymeric material, and the polymer may have a prism layer in which a plurality of steric structures are repeatedly formed. Here, the plurality of patterns may be provided in the stripe type and the valley repeatedly as shown.

In the second prism sheet 860, the edges and the valleys on one surface of the support film may be perpendicular to the edges and the valleys on one surface of the support film in the first prism sheet 850. This is to evenly distribute the light transmitted from the light emitting module and the reflective sheet in all directions of the panel 870.

In the present embodiment, the first prism sheet 850 and the second prism sheet 860 form an optical sheet, which may be formed of other combinations, for example, a microlens array or 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 870. In addition to the liquid crystal display panel 860, other types of display devices requiring a light source may be provided.

In the panel 870, the liquid crystal is positioned between the glass bodies, and the 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 880 is provided on the front surface of the panel 870 so that light projected from the panel 870 transmits only red, green, and blue light for each pixel.

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 embodiments, but, on the contrary, This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

110: growth substrate 115: undoped semiconductor layer
120: first conductivity type semiconductor layer 130: active layer
131: well layer 132: barrier layer
132a: first region 132b: second region
132c: third region 140: second conductivity type semiconductor layer
150: electron blocking layer 155: first electrode
160: second electrode 170: transparent electrode layer
210: conductive support substrate 215: bonding layer
230: reflective layer 240: passivation layer
310: package body 321, 322: first and second lead frames
330: wire 340: molding part
350: phosphor 710: light emitting module
720: Reflector 730: Shade
800: Display device 810: Bottom cover
820: reflector 840: light guide plate
850: first prism sheet 860: second prism sheet
870: Panel 880: Color filter

Claims

A first conductive semiconductor layer;
A second conductivity type semiconductor layer; And
And an active layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,
The active layer may be formed by alternately stacking a well layer and a barrier layer at least once, and the barrier layer may include a first region, a second region positioned in the direction of the first conductivity type semiconductor layer with respect to the first region, and Each of the third regions positioned in the direction of the second conductivity-type semiconductor layer with respect to the first region;
And at least one barrier layer, wherein an energy band gap of the first region is greater than an energy band gap of the second region and an energy band gap of the third region.

The method of claim 1,
In the at least one barrier layer, the In content increases from the first region to the second region and the third region, respectively.

3. The method of claim 2,
A light emitting device in which the In content of the second region and the In content of the third region are the same.

3. The method of claim 2,
A light emitting device in which the In content of the second region and the In content of the third region are different from each other.

The method of claim 1,
In the at least one barrier layer, the energy band gap from the first region to the second region is reduced in the form of steps, straight lines or curved lines.

The method of claim 1,
In the at least one barrier layer, the energy band gap from the first region to the third region is reduced in the form of steps, straight lines or curved lines.

The method according to claim 5 or 6,
The curved shape may include a concave curve toward the center of the energy band gap or a convex curve shape away from the center of the energy band gap.

The method of claim 1,
The well layer and the barrier layer of the active layer have a composition of In _x Ga ₁ _- _x N and In _y Ga ₁ _- _y N (0 <x <1, 0 = y <1, x> y), respectively.

The method of claim 1,
In the at least one barrier layer, the first region, the second region and the third region are In _y1 Ga ₁ _- _y1 N, In _y2 Ga ₁ _- _y2 N and In _y3 Ga ₁ _- _y3 N (0≤ A light emitting device having a composition of y1 ≦ 0.03, 0.03 ≦ y2, y3 ≦ 0.07, y1 <y2, y1 <y3).

The method of claim 1,
A light emitting device in which the energy bandgap of the first region and the energy bandgap of the third region are the same in the barrier layer closest to the second conductivity type semiconductor layer.

The method of claim 1,
And an electron blocking layer between the active layer and the second conductive semiconductor layer, wherein an energy band gap of the electron blocking layer is larger than an energy band gap of the barrier layer.

The method of claim 1,
The energy band gap of the well layer of the active layer is smaller than the energy band gap of the second region of the barrier layer and the third region of the barrier layer.

The method of claim 1,
And a second electrode on the first conductive semiconductor layer and a second electrode on the second conductive semiconductor layer.

The method of claim 13,
And a transparent electrode layer disposed between the second conductivity type semiconductor layer and the second electrode.