KR20170082830A - Light emitting device - Google Patents

Abstract

A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; A first electrode on the first conductive type semiconductor layer; A second electrode on the second conductive type semiconductor layer; And at least one pair of well layers and a barrier layer disposed between the first conductive semiconductor layer and the active layer, wherein the barrier layer includes at least a pair of first layers and a second barrier layer disposed between the first layers And a second layer having a composition different from that of the first layer.

Description

[0001] LIGHT EMITTING DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly, to an improvement in quality of a light emitting structure and an improvement in light output.

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

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

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

1 is a view showing a conventional light emitting device.

A conventional light emitting device 100 includes a light emitting structure 120 including a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126 on a substrate 110 The first electrode 162 and the second electrode 166 are disposed on the first conductivity type semiconductor layer 122 and the second conductivity type semiconductor layer 126, respectively.

There may occur a problem of quality deterioration of the light emitting structure 120 due to mismatch of lattice constants or the like between the substrate 110 and the light emitting structure 120 which are different materials. A superlattice layer may be disposed for current diffusion and stress relaxation in the direction of the active layer 124 from the layer 122.

However, even if a superlattice layer is disposed, a stress applied to the active layer 124 still exists, and valley-shaped defects may occur in the first conductivity type semiconductor layer 122, The light output of the light emitting device 100 may be lowered.

In particular, when a v-pit (pit) structure is formed in the light emitting structure 120 to improve the luminous intensity of the light emitting device 100, the stress applied to the light emitting structure 120 can be increased.

The embodiments attempt to improve the quality of the light emitting device and improve the current characteristics to improve the characteristics of the light emitted from the light emitting device.

A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; A first electrode on the first conductive type semiconductor layer; A second electrode on the second conductive type semiconductor layer; And at least one pair of well layers and a barrier layer disposed between the first conductive semiconductor layer and the active layer, wherein the barrier layer includes at least a pair of first layers and a second barrier layer disposed between the first layers And a second layer having a composition different from that of the first layer.

Another embodiment includes a light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; A first electrode on the first conductive type semiconductor layer; A second electrode on the second conductive type semiconductor layer; And at least one pair of well layers and a barrier layer disposed between the first conductive semiconductor layer and the active layer, wherein the barrier layer includes at least a pair of first layers and a second barrier layer disposed between the first layers And a second layer having a different energy band gap from the first layer.

The first layer may comprise GaN, and the second layer may comprise AlGaN.

The well layer may comprise InGaN.

The thickness of the second layer may be 1 to 1.5 times the thickness of the well layer.

The thickness of the barrier layer may be 3 to 3.5 times the thickness of the well layer.

The In (indium) composition ratio of the well layer may be 13% to 17%.

The Al (aluminum) composition ratio of the second layer may be 1% to 10%.

The light emitting device according to the embodiments includes a superlattice layer of InGaN / GaN / AlGaN / GaN structure, which reduces the stress acting on the light emitting structure and improves the film characteristics of the light emitting structure, The light output can be improved.

Particularly, when a v-pit (pit) structure is formed in the light emitting structure, it can act as a stress relieving layer for preventing defects acting on v-pit-shaped valleys and current leakage.

1 is a view showing a conventional light emitting device,
2 is a sectional view of an embodiment of a light emitting device,
FIG. 3 is a view showing the structure of the superlattice layer of FIG. 2,
FIG. 4 is a diagram showing the energy band gap of the superlattice layer of FIG. 3,
FIG. 5 is a graph showing the growth of a superlattice layer according to temperature,
6 is a view showing a light emitting device package including a light emitting element.

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. Also, the size of each component does not entirely reflect the actual size.

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

The light emitting device 200 according to the embodiment includes the substrate 210, the buffer layer 215, the active layer 220, the superlattice layer 230, the electron blocking layer 240, the transparent electrode layer 250, A first electrode 262, and a second electrode 266. In addition,

The substrate 210 may be formed of a material suitable for semiconductor material growth or a carrier wafer, may be formed of a material having excellent thermal conductivity, and may include a conductive substrate or an insulating substrate. For example, at least one of sapphire (Al ₂ O ₃ ), SiO ₂ , SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge and Ga ₂ O ₃ can be used.

A pattern may be disposed on the surface of the substrate 210 to reflect or scatter light traveling in the direction of the substrate 210 emitted from the active layer 224 to improve the light efficiency of the light emitting device 200 as a whole.

Since the substrate 210 and the light emitting structure are different materials, the lattice mismatch is very large and the thermal expansion coefficient difference between them is very large. Therefore, the dislocation, the melt-back The buffer layer 215 may be formed between the substrate 210 and the light emitting structure because cracks, pits, and surface morphology may occur.

The first conductivity type semiconductor layer 222 may be 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? For example, GaN, AlN, AlGaN, InGaN, InN, InAlGaN and AlInN, and n-type dopants such as Si, Ge, Sn, Se and Te can be doped.

The doping concentration of the n-type dopant may be relatively high in the lower region of FIG. 2 in the first conductive type semiconductor layer 222. The higher the doping concentration of the n-type dopant, the more electrons can be carriers. , It is necessary for the electrons to smoothly move from the first conductivity type semiconductor layer 222 to the active layer 224.

The active layer 224 is disposed between the first conductivity type semiconductor layer 222 and the second conductivity type semiconductor layer 226 and may include a single well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW) Well structure, a quantum dot structure, or a quantum wire structure.

InGaN / InGaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and AlGaN / AlGaN / InGaN / GaN, / AlGaAs, GaP (InGaP) / AlGaP, but is not limited thereto.

A superlattice layer 230 is disposed between the first conductive semiconductor layer 222 and the active layer 224 and will be described later.

The second conductive semiconductor layer 226 may be formed of a semiconductor compound. The second conductive semiconductor layer 226 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a second conductive dopant. The second conductive semiconductor layer 226 may be formed of any one or more of AlGaN, GaN AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the second conductivity type semiconductor layer 226 is a p-type semiconductor layer, the second conductivity type dopant may be a p-type dopant such as Mg, Zn, Ca, Sr, and Ba. The second conductivity type semiconductor layer 226 may be formed as a single layer or a multilayer, but is not limited thereto.

An electron blocking layer 240 may be disposed between the active layer 224 and the second conductive semiconductor layer 226. Since the electrons have greater mobility than the holes, the electron blocking layer 240 prevents an excessive amount of electrons from migrating and gathering to a portion adjacent to the second conductivity type semiconductor 226, 226), it is possible to prevent electrons and holes from combining with each other only in the adjacent region.

Electron blocking layer 240 is _{Al x In y Ga 1 -x- y} N can be formed of (0≤x≤1,0≤y≤1) based semiconductor, for example may be made of AlGaN, an active layer ( 224, and may be formed to have a thickness of, for example, about 100 Å to about 600 Å, but the present invention is not limited thereto.

Since the contact characteristics between the second electrode 266 and the second conductivity type semiconductor layer 226 are poor, the light-transmitting conductive layer 250 may be formed on the light-emitting structure 220. Therefore, the ITO (Indium Tin Oxide) It is possible to improve current injection characteristics into the second conductivity type semiconductor layer 226 because the contact characteristics with the second electrode 266 are improved.

The second conductivity type semiconductor layer 226, the electron blocking layer 240, the active layer 224, and the super lattice layer 230 from the translucent conductive layer 250 to portions of the first conductivity type semiconductor layer 222 The first electrode 262 is disposed on the first conductive type semiconductor layer 222 exposed by a part of the first conductive type semiconductor layer 222 and the first electrode 262 is disposed on the transparent conductive layer 250, Two electrodes may be disposed.

The first electrode 262 and the second electrode 266 may include at least one of Al, Ti, Cr, Ni, Cu, Or a multi-layer structure.

Although FIG. 2 shows a lateral light emitting device, a super lattice layer structure described later may be applied to a vertical light emitting device or a flip chip light emitting device.

FIG. 3 illustrates a structure of the superlattice layer of FIG. 2, and FIG. 4 illustrates an energy band gap of the superlattice layer of FIG.

The superlattice layer 230 has a structure in which the well layer 232 and the barrier layer 234 are repeated several times. For example, the well layer 232 and the barrier layer 234 are repeated three to five times But the present invention is not limited thereto. The well layer 232 may be made of InGaN. The barrier layer 234 may include a first layer 234a and a second layer 234b wherein the second layer 234b may be disposed between the first layer 234a and the first layer 234a, 234a may be made of GaN, and the second layer 234b may be made of AlGaN. A second layer 234b containing Al (aluminum) is provided in the barrier layer 234, so that the stress acting in the active layer direction can be reduced. In addition, the second layer 234b reduces the mobility of electrons directed toward the active layer direction, so that electrons can be evenly distributed over the entire region of the active layer.

4, the energy band gap of the well layer (InGaN) may be smaller than the energy bandgap of the barrier layer (GaN / AlGaN / GaN), and the energy band gap of the first layer (GaN) may be smaller than the energy bandgap of the second layer (AlGaN).

Referring again to FIG. 3, the thickness t4 of the barrier layer 234 may be between 3 and 3.5 times the thickness t1 of the well layer 232, for example, the thickness of the well layer 232 t1 may be between 10 Ohm Strong (A) and 20 Ohm Strong and the thickness t4 of barrier layer 234 may be between 29 Ohm Strong and 71 Ohm Strong.

If the thickness t1 of the well layer 232 is less than 10 angstroms, tunneling of electrons may occur. If the thickness t1 of the well layer 232 is larger than 20 angstroms, the electrons may be trapped in the well, resulting in a decrease in mobility.

The thickness t3 of the second layer 234b may be 1 to 1.5 times the thickness t1 of the well layer 232 and may be, for example, 10 to 30 ohms Strong, It can be 15 ohms to 16 ohms.

The thickness t4 of the entire barrier layer 234 may be the sum of the thickness t2 of the first layer 232a and the thickness t3 of the second layer 234b.

The In (indium) composition ratio in the well layer 232 may be 13% to 17%, for example, the well layer 232 may be In _x Ga _{1 - x} N (0 _{? X} ? 1, 0? ), X may be 0.13 or more and 0.17 or less. Light can be weakly emitted not only in the active layer 224 in the light emitting structure 220 but also in the well layer 232 in the superlattice layer 230. When the composition ratio of In is less than 13%, light having a short wavelength is emitted, The light balance of the active layer 200 may be broken, and if it is larger than 17%, light of a long wavelength may be emitted and overlap with light emitted from the active layer 224.

The Al (aluminum) composition ratio in the second layer 234b may be 1% to 10%, for example, the second layer 234b may be Al _x Ga _{1 - x} N (0 _{? X} ? 1, 1), x may be 0.01 or more and 0.10 or less. In order for the superlattice layer 230 to function as a stress relaxation layer, at least 1% of Al should be contained in the second layer 234b in the bottled layer 234, Lt; / RTI >

If the superlattice layer is made of InGaN / GaN structure, the InGaN / GaN / AlGaN / GaN structure can be formed in one direction due to the difference in lattice constant of InGaN / GaN. Thereby preventing warping of the superlattice layer.

5 is a graph showing the growth of a superlattice layer according to temperature.

 The growth temperature of the barrier layer, particularly the second layer including Al, may be higher than the growth temperature of the well layer containing In. In FIG. 5, AlGaN is grown at a high temperature of about + 190 ° C higher than InGaN, The crystallinity of the layer can be increased and the thickness of the second layer can be determined according to the duration of the high temperature.

The superlattice layer 230 having the above-described structure can serve as a stress relaxation layer that prevents defects acting on the v-pit-shaped valleys and current leakage, particularly when a v-pit (pit) structure is formed in the light emitting structure .

The light emitting device according to the embodiment is provided with a super lattice layer of InGaN / GaN / AlGaN / GaN structure to reduce the stress acting on the light emitting structure and improve the film characteristics of the light emitting structure, The output can be improved.

Table 1 shows the light output of the light emitting device according to the comparative example of FIG. 1 and the current of the light emitting device according to the embodiment. When connected to the same power source, the current flowing through the light emitting device according to the embodiment is increased as compared with the comparative example.

Comparative Example Example Current (mA) 128.34 138.65

6 is a view showing a light emitting device package including a light emitting element.

The light emitting device package 300 according to the embodiment may include a body 310, a cavity formed on the body 310, and a light emitting device 200 disposed in the cavity. In the body 310, And leadframes 322 and 326 for electrical connection with the printed circuit board 200.

The light emitting device 200 may be disposed on the bottom surface of the cavity and the molding part 250 may be disposed in the cavity so as to surround the light emitting device 200. The molding part 350 may include a phosphor 355 And can emit light in the second wavelength range by being excited by the light in the first wavelength range emitted from the light emitting device 200. The resin that can be mixed with the phosphor in the molding part 350 may be any one of a silicone resin, an epoxy resin, and an acrylic resin or a mixture thereof.

The body 310 may be formed of a silicon material, a synthetic resin material, or a metal material. The body 310 may have a cavity with an open top and side and bottom surfaces.

The cavity may be formed in a cup shape, a concave container shape or the like, and the side surface (i) of the cavity may be formed perpendicular or inclined with respect to the bottom surface (b), and may vary in size and shape.

The shape of the cavity viewed from the top may be circular, polygonal, elliptical, or the like, but may be a curved edge shape, but is not limited thereto.

The body 310 may include a first lead frame 222 and a second lead frame 326 and may be electrically connected to the light emitting device 200 through a wire 330. When the body portion 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 portion 310 to prevent an electrical short between the first and second lead frames 322 and 326 have.

The first lead frame 322 and the second lead frame 326 are electrically separated from each other and can supply current to the light emitting element 200. [ The first lead frame 322 and the second lead frame 326 may reflect the light generated from the light emitting device 200 to increase the light efficiency, It may be discharged.

6, the light emitting device 200 may be connected to the first lead frame 322 and the second lead frame 326 through a wire 330. However, in addition to the wire bonding method, Bonding method.

The light emitting device package may include one or more light emitting devices according to the above-described embodiments, but the present invention is not limited thereto.

The above-described light emitting device package can be used as a light source of an illumination system, and can be used, for example, in an image display device and a lighting device.

The above-described light emitting devices may be arranged in a line on a circuit board to be used in a lighting device or as an edge type light source in an image display device.

The light emitting device may be a plurality of light emitting devices arranged on a circuit board in a plurality of rows and columns, and may be used as a light source of direct type in a video display device.

The light emitting device package may be used as a light source of a mobile terminal or a light source of a vehicle lighting apparatus, and may be used as a light source of a headlight, a tail lamp or a direction indicator when used as a light source of a vehicle lighting apparatus.

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, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100, 200: light emitting device 110, 210:
215: buffer layer 220: light emitting structure
222: first conductivity type semiconductor layer 224: active layer
226: second conductivity type semiconductor layer 230: superlattice layer
232: well layer 234: barrier layer
234a: first layer 234b: second layer
240: Electron barrier layer 250: Transparent conductive layer
300: Light emitting device package

Claims (8)

A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer;
A first electrode on the first conductive type semiconductor layer;
A second electrode on the second conductive type semiconductor layer; And
And a barrier layer disposed between the first conductive semiconductor layer and the active layer and including at least a pair of well layers and a barrier layer, wherein the barrier layer is disposed between at least a pair of first layers and between the first layers And a second layer having a composition different from that of the first layer. A light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer;
A first electrode on the first conductive type semiconductor layer;
A second electrode on the second conductive type semiconductor layer; And
And a barrier layer disposed between the first conductive semiconductor layer and the active layer and including at least a pair of well layers and a barrier layer, wherein the barrier layer is disposed between at least a pair of first layers and between the first layers And a second layer having an energy band gap different from that of the first layer. 3. The method according to claim 1 or 2,
Wherein the first layer comprises GaN, and the second layer comprises AlGaN. 3. The method according to claim 1 or 2,
Wherein the well layer comprises InGaN. 3. The method according to claim 1 or 2,
Wherein the thickness of the second layer is 1 to 1.5 times the thickness of the well layer. 3. The method according to claim 1 or 2,
Wherein the thickness of the barrier layer is 3 to 3.5 times the thickness of the well layer. 3. The method according to claim 1 or 2,
And the In (indium) composition ratio of the well layer is 13% to 17%. 3. The method according to claim 1 or 2,
And the Al (aluminum) composition ratio of the second layer is 1% to 10%.

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