KR20140034665A

KR20140034665A - Light emittng device

Info

Publication number: KR20140034665A
Application number: KR1020120138944A
Authority: KR
Inventors: 이광칠; 김경훈; 박해진; 김동하; 김재훈
Original assignee: 엘지이노텍 주식회사
Priority date: 2012-09-12
Filing date: 2012-12-03
Publication date: 2014-03-20

Abstract

An embodiment includes a substrate; An ultraviolet light emitting semiconductor structure on the substrate; And an intermediate layer between the ultraviolet light emitting semiconductor structure and the substrate, wherein the ultraviolet light emitting semiconductor structure includes a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. At least one of the first conductivity type semiconductor layer and the second conductivity type semiconductor layer includes AlGaN and the intermediate layer includes AlN and a plurality of air voids in the AlN, Wherein the air voids are at least partially irregularly arranged, and the air voids are arranged at 10 ⁷ to 10 ¹⁰ per 1 square centimeter.

Description

[0001] LIGHT EMITTING DEVICE [0002]

An embodiment relates to a light emitting element.

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

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

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

1 is a view showing a conventional light emitting device.

A conventional light emitting device 100 includes a light emitting structure 140 including a first conductive semiconductor layer 142, an active layer 144, and a second conductive semiconductor layer 146 on a substrate 110 made of sapphire or the like And the first electrode 142 and the second electrode 146 are disposed on the first conductive semiconductor layer 142 and the second conductive semiconductor layer 146, respectively.

Electrons injected through the first conductivity type semiconductor layer 142 and holes injected through the second conductivity type semiconductor layer 146 meet with each other to form an energy band unique to the active layer 144 And emits light having energy determined by the light intensity. The light emitted from the active layer 144 may be different depending on the composition of the active layer 144 and may be blue light, ultraviolet light (UV), deep ultraviolet light, or the like.

In the light emitting device described above, particularly in the horizontal type light emitting device, the light traveling downward in FIG. 1 may be absorbed by the substrate 100 or may be totally reflected by the inner boundary surface of the substrate 100 or the like to lower the light extraction efficiency.

In order to solve such a problem, it is necessary to reflect or scatter light on the surface of the substrate during the method, and to reduce the amount of light that travels to the inside of the substrate and is totally reflected.

2B is a view illustrating a process of forming an air void by a wet etching process in a conventional light emitting device, and FIG. 2C is a cross- Fig.

The light emitting device shown in FIG. 2A uses a patterned sapphire substrate (PSS) to form an air void on the surface of the buffer layer including AlN. In the light emitting device shown in FIG. 2A, a pattern and an air void are formed at the interface between the PSS and the buffer layer, so that light generated in the GaN can be scattered or reflected without advancing into the PSS, thereby improving light extraction efficiency of the light emitting device.

2B, a mask 115 is formed of silicon oxide or the like on the surface of the substrate 110 including sapphire, and a light emitting structure 140 including GaN is grown thereon. In (b), silicon oxide (SiO ₂ ) is removed by using hydrofluoric acid or the like, and in (c), an air void is formed by etching GaN around the region where the silicon oxide is removed.

2 (c) shows the action of a mask such as silicon oxide (SiO ₂ ). Crystal defects (shown by solid vertical lines) that may occur at the interface between the substrate and the buffer layer can be blocked by the mask shown in red, and the buffer layer grown between the masks grows laterally A buffer layer may be formed in the adjacent mask region.

However, the conventional light emitting device described above has the following problems.

In the case of manufacturing the light emitting device shown in FIG. 2 (a), a process is added to optimize the size, period and shape of the pattern formed in the PSS. In the case of the process shown in FIG. 2 (b), the deposition and patterning of the silicon oxide and the wet etching process must be performed, which may result in additional process and cost.

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

Wherein the active layer comprises a multiple quantum well structure and the multiple quantum well structure comprises a quantum wall layer comprising Al _x Ga _(1-x) N (0 <x <1) and AlyGa _(1- y < 1) may be included in at least one cycle.

The quantum well layer may include the dopant of the second conductivity type.

The peak wavelength of the ultraviolet light emitted from the ultraviolet light emitting semiconductor structure may be from 315 nm to 350 nm.

The intermediate layer may be 1.5 micrometers to 10 micrometers in thickness.

The height of each air void may be at least 1 micrometer less than the thickness of the intermediate layer.

The height of each air void may be from 0.5 micrometers to 9 micrometers.

One end of each air void may be in contact with or spaced from the boundary between the substrate and the intermediate layer, and the other end of the air void may be disposed inside the middle layer.

At the top of the other end of the air void, the material of the laterally grown intermediate layer at the periphery of the air void can be combined.

The dislocation of the laterally grown intermediate layer at the periphery of the air void at the upper part of the other end of the air void can converge.

The distance from one end of the air void to the region where the width of the air void is maximum may be larger than the distance from the region where the width of the air void is maximum to the other end of the air void.

The region where the width of the air void is the maximum can be disposed so as to be spaced apart from the boundary between the substrate and the intermediate layer and the boundary between the intermediate layer and the light emitting structure.

The difference in thermal expansion coefficient between the substrate and the intermediate layer may be greater than the difference in thermal expansion coefficient between the intermediate layer and the light emitting structure.

In the light emitting device according to the present embodiment, the potential generated at the interface between the substrate and the intermediate layer is blocked by the air void in the growth process, so that the quality of the light emitting structure made of AlGaN, GaN or the like can be improved. The light extraction efficiency can be improved by the void.

1 is a view showing a conventional light emitting device,
2B is a view illustrating a process of forming an air void by a wet etching process in a conventional light emitting device, and FIG. 2C is a cross- Fig.
3 is a view illustrating an embodiment of a light emitting device,
4A to 4F are views showing an embodiment of a manufacturing process of the light emitting device of FIG. 2,
5A and 5B are views showing another embodiment of the manufacturing process of the light emitting device of FIG. 2,
6 is an AFM image of the air void,
7A and 7B are AFM images of an intermediate layer in which an air void is formed after 1-micrometer growth of AlN,
8A to 8C are diagrams showing the internal quantum efficiency, the light scattering effect, and the light extraction efficiency of the light emitting device according to the density of air voids,
9A to 9C are views showing the shape change of the air void due to the difference in thermal expansion coefficient between the substrate and the intermediate layer,
10 is a view showing one embodiment of the shape of the air void,
11A to 11E are views showing a manufacturing process of another embodiment of the light emitting device,
12A to 12D are SEM and CL images of the light emitting device shown in FIG. 3,
13 is a view showing an embodiment of a light emitting device package in which a light emitting device is disposed,
14 is a view showing an embodiment of a lighting device in which a light emitting element is disposed,
15 is a view showing an embodiment of a video display device in which a light emitting device is disposed.

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

In the description of 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.

3 is a view showing an embodiment of a light emitting device.

The light emitting device 200 includes an intermediate layer 220 and a light emitting structure 240 disposed on a substrate 210.

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

The intermediate layer 220 is intended to mitigate the difference in lattice mismatch and thermal expansion coefficient of the material between the substrate 210 and the light emitting structure 240 in the present embodiment. In addition to the above- (240), and is the same in the other embodiments described later. The material of the intermediate layer 240 may be at least one of Al, GaN, InN, InGaN, AlGaN, InAlGaN, and AlInN in addition to the Group III-V compound semiconductor such as AlN. However, since the intermediate layer 220 has a predetermined thickness and an air void is formed therein as described later, it may be an intermediate layer having a different role from the conventional buffer layer.

The lattice mismatch between GaN and AlGaN and sapphire is very large when the substrate 210 is formed of sapphire or the like and the light emitting structure 240 including GaN or AlGaN is disposed on the substrate 210, The dislocation, melt-back, crack, pit, and surface morphology defects that degrade the crystallinity can occur. Therefore, AlN can be used for the intermediate layer 220.

A plurality of air voids 225 may be formed in the intermediate layer 220. One end a of the air void may be disposed in contact with the boundary between the substrate 210 and the intermediate layer 220, (B) may be disposed inside the intermediate layer 220, and the other end (b) may be disposed inside the intermediate layer 220. The detailed structure and arrangement of the air void 220 will be described later.

Although not shown, an undoped GaN layer or an AlGaN layer may be disposed between the intermediate layer 220 and the light emitting structure 240 to prevent the potentials and the like from being transmitted into the light emitting structure 240. Further, the dislocation is blocked even in the intermediate layer 220, and the intermediate layer of high quality / high crystallinity can be grown.

The light emitting structure 240 includes a first conductive semiconductor layer 242, an active layer 244, and a second conductive semiconductor layer 246.

The first conductive semiconductor layer 242 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a first conductive dopant. The first conductive semiconductor layer 242 may be 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? For example, the first conductive semiconductor layer 242 may be formed of Al ₀ _.55 Ga ₀ _.45 N, and the second conductive semiconductor layer 242 may be formed of any one of AlGaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. have.

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

When the light emitting device 200 illustrated in FIG. 3 is an ultraviolet (UV) light source, a deep ultraviolet light source, or a non-polarized light emitting device, the first conductivity type semiconductor layer 242 may include at least one of InAlGaN and AlGaN. When the first conductive semiconductor layer 242 is made of AlGaN, the content of Al may be 50%. If the potential generated in the substrate or the intermediate layer is transmitted to the active layer, since In can not be used in the active layer in the deep ultraviolet light emitting device, defects due to dislocation can not be buffered. In addition, in the case of a deep ultraviolet light emitting device, since deep ultraviolet light is absorbed much in GaN, AlGaN can be used as a material of the light emitting structure.

The active layer 244 is disposed between the first conductivity type semiconductor layer 242 and the second conductivity type semiconductor layer 246 and includes a single well structure, a multiple well structure, a single quantum well structure, A multi quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure.

InGaN / InGaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and InGaN / AlGaN / , / AlGaAs, GaP (InGaP) / AlGaP, but the present invention is not limited thereto. The well layer may be formed of a material having an energy band gap smaller than the energy band gap of the barrier layer. In particular, the active layer 244 according to the embodiment may generate ultraviolet light or deep ultraviolet light. In this case, the active layer 244 may have a multi-quantum well structure, and more specifically, an Al _x Ga _(1-x) A quantum well structure including a quantum well layer including N (0 <x <1) and a quantum well layer including Al _y Ga _(1-y) N (0 <x <y <1) Where the quantum well layer may comprise a dopant of a second conductivity type as described below.

The second conductive semiconductor layer 246 may be formed of a semiconductor compound. The second conductive semiconductor layer 246 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a second conductive dopant. The second conductivity type semiconductor layer 246 is formed of a semiconductor material having a composition formula of In _x Al _y Ga ₁ _-x- _y N (0? X? 1, 0? _Y? 1, 0? _X + y? For example, when the second conductive semiconductor layer 246 is made of Al _x Ga _(1-x) N, the second conductivity type semiconductor layer 246 may be formed of Al _x Ga _(1-x) N, The composition of Al may decrease from 0.55 to 0.3 as the distance from the region adjacent to the active layer 244 increases, and the composition of Ga may increase from 0.45 to 0.7.

When the second conductive semiconductor layer 246 is a p-type semiconductor layer, the second conductive dopant may be a p-type dopant such as Mg, Zn, Ca, Sr, or Ba. The second conductive semiconductor layer 246 may be formed as a single layer or a multilayer, but is not limited thereto. The second conductive semiconductor layer 246 may include at least one of InAlGaN and AlGaN when the light emitting device 200 is ultraviolet (UV), deep ultraviolet (Deep UV), or unpolarized light emitting device.

Although not shown, an electron blocking layer may be disposed between the active layer 244 and the second conductive semiconductor layer 246, and an electron blocking layer having a superlattice structure may be disposed between the active layer 244 and the second conductive semiconductor layer 246 . For example, AlGaN doped with a second conductive dopant may be disposed in the superlattice, and a plurality of GaN layers having different composition ratios of aluminum may be interleaved to form a layer.

The transparent conductive layer 260 may be disposed on the light emitting structure 240 to uniformly supply the current from the second electrode 256 to the second conductive semiconductor layer 246 over a wide area. Although not shown, a GaN layer may be disposed between the second conductive semiconductor layer 246 and the transparent conductive layer 260, and GaN may be doped with the second conductive type dopant.

In order to supply current to the first conductivity type semiconductor layer 242 when the substrate 210 is an insulating substrate, the first conductive type semiconductor layer 242 is mesa-etched from the transparent conductive layer 260 to a portion of the first conductivity type semiconductor layer 242, Type semiconductor layer 242 may be exposed.

The first electrode 252 may be disposed on the exposed first conductive semiconductor layer 242 and the second electrode 256 may be disposed on the transparent conductive layer 260.

The light emitting device 200 having the above structure can prevent the dislocation growth due to the lattice mismatch and the difference in the thermal expansion coefficient at the interface between the substrate 210 and the intermediate layer 220 by forming air voids in the intermediate layer 220. The light emitted from the active layer 244 in the downward direction in FIG. 3 is scattered or refracted by the air void 225 to prevent the light from entering into the substrate 210, It is possible to prevent the total extraction and the light extraction of the light emitting element 200 from being degraded.

4A to 4F are views showing a manufacturing process of the light emitting device of FIG.

First, as shown in FIG. 4A, a seed 220a for growing an intermediate layer, that is, an intermediate layer in this embodiment, is formed on a substrate 210. FIG. The seeds 220a may be formed and arranged in a random size.

An intermediate layer 220 including air voids is grown on the substrate 210 as shown in FIG. 4B. The composition of each layer is the same as that shown in FIG. 3, and the composition of each layer is shown in FIG. 3 And therefore it is omitted.

If the intermediate layer 220 to be grown AlN, TMAl at a temperature Centigrade 1200 to 1400 degrees (Tri-methyl Aluminum) and NH _3, respectively 10 to 100 [mu] mol / min (umol / min) and 50 to 500 micromoles / Min, and the molar ratio of the Group 5 element to the Group 3 element may be less than 100.

If the growth temperature of AlN is lower than 1200degree, the adsorption of aluminum on the sapphire surface is slow and the generation of seeds such as nuclei having good crystallinity may be difficult. When the temperature is higher than 1400degree, The crystallinity of AlN may be bad. The additional growth temperature of the intermediate layer 220 may be in the range of 1000 to 1600 ° C. In general, since aluminum manganese has low surface mobility, high temperature is required for high-quality epitaxial growth, It is not necessary to grow to more than 1600 degrees.

At this time, a plurality of air voids 225 may be randomly formed from the interface between the substrate 210 and the intermediate layer 220, and potentials may be generated at the interface between the substrate 210 and the intermediate layer 220 The potential can be merged in the region where it meets the air void 225.

The dotted line g indicates the growth direction of the AlN constituting the intermediate layer 220. Since the AlN grows in the horizontal direction in addition to the growth in the vertical direction, the AlN grown horizontally or side- ought. The dislocations grown at the interface between the substrate 210 and the intermediate layer 220 are shown by a dot-dash line (d), and as the AlN is laterally grown and converged, the dislocation is also merged.

In FIG. 4C, the growth of the intermediate layer 220 is completed, and AlN grows horizontally or laterally in addition to the vertical direction, so that the growth of the air void 225 is blocked, and the potential also converges.

The air void means an area filled with air in a space in which the AlN or the like is not grown in the intermediate layer 220 and may be filled with a process gas during the manufacturing process or may be a vacuum.

Then, the light emitting structure 240 and the transparent conductive layer 260 are grown on the intermediate layer 220 as shown in FIG. 4D. The first conductive semiconductor layer 242 may be formed using an AlGaN layer doped with an n-type dopant using a chemical vapor deposition (CVD) method, molecular beam epitaxy (MBE), sputtering or vapor phase epitaxy (HVPE) .

The first conductive semiconductor layer 242 may be formed by depositing a silane containing an n-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ) Gas (SiH ₄ ) may be implanted and formed.

The active layer 244 may be formed by implanting trimethylgallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and trimethyl indium gas (TMIn) to form a multiple quantum well structure But is not limited thereto.

Second conductive composition of the semiconductor layer 246 is shaped the same as described above, such as the chamber and trimethyl gallium gas (TMGa), ammonia gas (NH _3), nitrogen gas (N _2), and magnesium (Mg) p Bisei including impurities butyl cyclopentadienyl magnesium _{(EtCp 2 Mg) {Mg (} C 2 H 5 C 5 H 4) 2} is injected may be a p-type GaN layer formed, but the embodiment is not limited thereto. The transparent conductive layer 260 is formed of a material such as ITO (Intium Tin Oxide).

4E, the portions of the second conductivity type semiconductor layer 246, the active layer 244, and the first conductivity type semiconductor layer 242 are mesa-etched from the side surface of the transparent conductive layer 260 So that a part of the first conductivity type semiconductor layer 242 can be exposed.

The first electrode 252 and the second electrode 256 may be disposed on the exposed first conductive semiconductor layer 242 and the transparent conductive layer 260, respectively, as shown in FIG. 4F. The first electrode 252 and / or the second electrode 256 may be formed of a conductive material such as a metal. More specifically, the first electrode 252 and / or the second electrode 256 may be formed of Ag, Ni, Al, Rh, Pd, Ir, Ru, Pt, Au, Hf, and an optional combination thereof, and may be formed as a single layer or a multilayer structure.

In FIG. 4F, the height h ₁ of each of the air voids may be at least 1 micrometer smaller than the thickness h _{2 of the} entire intermediate layer 220. The thickness h ₂ of the intermediate layer 220 may be between 1.5 micrometers and 10 micrometers, and the height h ₁ of each air void may be between 0.5 micrometers and 9 micrometers.

And the air void can have a density of 10 ⁷ to 10 ¹⁰ deployed per square centimeter.

The height h ₁ and width of each of the air voids may be random for each of the air voids in which the air void modifies the growth conditions when growing the intermediate layer 220 on the substrate 210 And is formed spontaneously. In addition to the shape, the air void may be random at least in some areas, and the distance and pitch between neighboring air voids in FIG. 4F may not be constant.

Figures 5A and 5B illustrate another embodiment in which air voids grow. In the embodiment shown in FIGS. 4A to 4F, the air void starts to grow on the interface between the substrate and the intermediate layer, but in this embodiment, the air void is grown in the intermediate layer 220 '. That is, in FIG. 5A, seeds 220a such as AlN may be formed on the substrate 210 'so that the air voids between adjacent seeds 220a' may grow at a distance from the substrate 210 ' And the seed 220a 'grows in the vertical and horizontal directions g', so that the growth of the air void 225 'is terminated and the potential d' can converge as shown in FIG. 5B. The subsequent method of manufacturing the light emitting device is the same as the above embodiment.

The shape and size and arrangement of the air voids are random as described above, and the shape and arrangement of the air voids may be periodic when a mask is used as described later in Figs. 2A to 2C. When the mask is used, the distance and / or the pitch between the air voids can not be controlled at a predetermined interval, for example, on a nano scale due to the size of the mask itself. However, The distance and / or pitch between the air voids may be nanoscale and the density of the air voids according to embodiments of the present invention may be greater than the density of the air voids produced by the mask process.

As one example, as illustrated above, the air void may have a density of 10 ⁷ to 10 ¹⁰ deployed per square centimeter, wherein the density of the air void means the number of air voids formed per unit area. The density of the air void is in a range exceeding the resolving power of the present photolithography, and the light extraction efficiency of the light emitting device can be further improved due to the air void arranged more densely than the conventional one.

If the density of the air void is less than 10 ⁷ per square centimeter, it can also be produced by the mask process described above. When forming an air void using photolithography and dry etching using a mask on AlN, Micrometer to 3 micrometers in size. At this time, if air voids having a width of 2 micrometers are formed, they can be formed at a density of 6 × 10 ⁶ per 1 square centimeter. If an air void having a width of 3 micrometers is formed, It can be formed at a density of 3 x 10 ⁶ per centimeter. Therefore, when air voids are formed at a density of less than 10 ⁷ per square centimeter, a process using a conventional mask can be used.

If the number of air voids exceeds 10 ¹⁰ per square centimeter, the number of air voids is too large, so that the AlN does not sufficiently grow horizontally, so that the convergence of the potential or the horizontally grown AlN may not be combined at the upper part of the air void.

6 is an AFM image of the air void.

Air voids can be formed when the area blackened in the image on the left is air void and the brightened AlN is grown to a width or diameter of 0.05 micrometers or more. The image on the left is enlarged from the right. Since four air voids are formed in the area of 0.1 micrometer height and 0.15 micrometer width (shown in red), the air void density is 3 × 10 ¹⁰ per square centimeter . Therefore, it is difficult to form air voids at a density of 10 ¹¹ or more per square centimeter. Figs. 7A and 7B are AFM images of an intermediate layer in which air voids are formed after 1 micrometer growth of AlN.

In FIG. 7A, air voids were formed at a density of 10 ⁸ or more per square centimeter, and in FIG. 7B, air voids were formed at a density of 10 ⁹ or more per square centimeter. In FIGS. 7A and 7B, the relative luminosity of the light emitting device is 1.3 to 1, and the light scattering effect due to the increase in air void density can be expected to increase in FIG. 7B.

If the density of the air void is less than 10 ⁷ per 1 cm 2, the luminous intensity of the light emitting device may be reduced to about 50% as compared with the case of FIG. 7A. If the density of the air void is more than 10 < ¹¹ > per square centimeter, adjacent air voids may merge and defects of AlN may occur in the converging region, The internal quantum efficiency decreases and the luminous intensity of the light emitting device can be reduced to about 50% of FIG. 7A.

8A to 8C are diagrams showing the internal quantum efficiency, the light scattering effect, and the light extraction efficiency of the light emitting device according to the density of air voids.

8A shows that the internal quantum efficiency (IQE) in the multiple quantum well structure of the light emitting device decreases when the density of the air void is 10 ¹¹ or more per square centimeter. In FIG. 8B, the density of the air void increases 8A and 8B, the light extraction efficiency of the entire light emitting device is such that the density of the air void is 10 ⁷ or more per square centimeter, and 10 per square centimeter It can be seen from Fig. 8c that the time when less than ^{11 is} optimal.

If the shape of the air void is increased or the density is increased by varying the growth conditions, it may be a glass for the potential blocking, but the AlN may grow in the lateral direction and may not be formed on the upper part of the air void, Or if the density is made smaller, the AlN grows in the lateral direction and is advantageous for growing AlN on the upper portion of the air void, but is not sufficient for interrupting the dislocation and may not be sufficient for refraction or scattering of light transmitted from the active layer.

9A to 9C are diagrams showing the shape change of the air void due to the difference in thermal expansion coefficient between the substrate and the intermediate layer.

Since the intermediate layer or the light emitting structure is grown at a high temperature during the manufacturing process of the light emitting device, the length and volume of the light emitting device can be reduced according to the thermal expansion coefficient when the light emitting device is disposed at room temperature after the growth process.

This thermal expansion or compression can be made to proceed differently depending on the thermal expansion coefficient of each layer, so that bowing may occur between layers or interfaces. The difference in thermal expansion coefficient may be larger between the substrate 210 such as sapphire and the intermediate layer 220 than between the light emitting structure such as GaN or AlGaN and the intermediate layer 220 such as AlN.

Since the coefficient of thermal expansion of the intermediate layer 220 is larger than the coefficient of thermal expansion of the substrate 210, when the temperature decreases to room temperature after the growth process at a high temperature shown in FIG. 9A, And the warpage of the intermediate layer becomes larger.

At this time, the intermediate layer may shrink more in the region opposite to the substrate, that is, the region in contact with the light emitting structure, rather than the region in contact with the substrate. As the intermediate layer shrinks, the size of the air void may also decrease. Since the intermediate layer shrinks more in the region far from the substrate, the air void has a larger cross-sectional area in the transverse direction in the region remote from the substrate Can be small.

In FIG. 9C, the size of the air void is shown to be wider in order to explain the structure of the air void in detail, and the air void can be random in size and arrangement as described above, May have a random shape other than a long rectangular shape.

That is, the area of the air void contacting the substrate is referred to as a ', the area of the air void opposite to the substrate is referred to as the other end' b ', and the middle area of the air void is defined as'c' the height (h ₃₎ with a height (h ₄₎ from the 'c' to the other terminal 'b' of this void to the 'c' from the end 'a' of the air voids of the previous contraction may be similar or equal. As shown, the middle region 'c' is the region between one end 'a' and the other end 'b' of the air void and may be closer to the other end 'b' than the one end 'a' of the air void.

Further, the cross-sectional area of the air void in the direction away from the substrate, particularly after the shrinkage due to heat, may be further reduced, and the height h ₅ from one end a to the 'c' (H ₆ ) from the other end (b) to the other end (b) of the air void. Further, h ₃ > h ₅ can be obtained because the entire intermediate layer can be reduced by heat and the size of the air void can be reduced.

10 is a view showing one embodiment of the shape of the air void.

The air voids shown as 225a are arranged at the boundary between the substrate 210 and the intermediate layer 220 at one end and the air voids shown at 225b are disposed at one end spaced apart from the boundary between the substrate 210 and the intermediate layer 220 have. 225c and 225d are arranged such that the air voids are arranged with a predetermined width at the interface between the substrate 210 and the intermediate layer 220 and the embodiment shown at 225e is similar to the embodiment shown at 225a, Shape.

The shape of the air void varies as described above, and is illustrated as having a predetermined width or a width similar to the rhombus in the above-described drawings to illustrate the growth process. However, the shape of the air void is not limited thereto, If the shape is reduced in height from the height, it may have another geometric shape, and may be displayed in a similar manner to a black line or a thread in an SEM photograph described later.

11A to 11E are views showing a manufacturing process of another embodiment of the light emitting device.

This embodiment is a step of manufacturing a vertical type light emitting device.

An air void 225 may be formed in the intermediate layer 220 in order to form an AlN seed on the substrate 210 and to grow the intermediate layer 220 in FIG. 11A. In this case, as shown in FIGS. 4A to 4C and 5A to 5C .

The light emitting structure 240 may be grown on the intermediate layer 220 as shown in FIG. 11B, but the transparent conductive layer may not be formed on the light emitting structure 240.

The ohmic layer 272, the reflection layer 274, the bonding layer 276 and the conductive supporting substrate 278 can be disposed on the light emitting structure 240 as shown in FIG. 11C. The ohmic layer 272, The reflective layer 274, the bonding layer 276, and the conductive supporting substrate 278 may serve as the second electrode.

The ohmic layer 272 may be about 200 Angstroms thick. The ohmic layer 272 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) ), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO nitride), AGZO (Al- Ga ZnO), IGZO , NiO, RuOx / ITO, Ni / IrOx / Au, and Ni / IrOx / Au / ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Au, and Hf, and is not limited to such a material.

The reflective layer 274 may be composed of a metal layer comprising aluminum (Al), silver (Ag), nickel (Ni), platinum (Pt), rhodium (Rh), or an alloy containing Al, Ag, Pt or Rh . Aluminum, silver, or the like can effectively reflect the light generated in the active layer 244, thereby greatly improving the light extraction efficiency of the light emitting device.

Since the metal support 278 can use a metal having a high electrical conductivity and sufficiently emit heat generated during operation of the light emitting device, a metal having high thermal conductivity can be used.

The conductive support substrate 278 may be formed of a metal or a semiconductor material. And may be formed of a material having high electrical conductivity and high thermal conductivity. For example, a material selected from the group consisting of molybdenum (Mo), silicon (Si), tungsten (W), copper (Cu) and aluminum (Al) (Cu-W), a carrier wafer (e.g., GaN, Si, Ge, GaAs, ZnO, SiGe, SiC, SiGe, Ga ₂ O _3, etc.) And the like.

The conductive support substrate 278 may have a mechanical strength enough to separate the entire nitride semiconductor into separate chips through a scribing process and a breaking process without causing warping of the entire nitride semiconductor.

The bonding layer 276 is formed of a metal such as gold (Au), tin (Sn), indium (In), aluminum (Al), silicon (Si), silver (Ag) , Nickel (Ni), and copper (Cu), or an alloy thereof.

The ohmic layer 272 and the reflective layer 274 may be formed by a sputtering method or an electron beam evaporation method and the conductive supporting substrate 278 may be formed by an electrochemical metal deposition method or a bonding method using an eutectic metal , A separate bonding layer 276 can be formed.

Then, the substrate 210 is separated as shown in FIG. 11D. The removal of the substrate 210 may be performed by a laser lift off (LLO) method using an excimer laser or the like in the case of a sapphire substrate, or a dry and wet etching method.

When the excimer laser light having a wavelength in a certain region in the direction of the substrate 210 is focused and irradiated using the laser lift-off method, heat energy is applied to the interface between the substrate 210 and the light emitting structure 240 The interface is separated into gallium and nitrogen molecules, and the substrate 210 is instantaneously separated from the laser light passing portion. At this time, the intermediate layer 220 can also be separated by the dry etching process.

If the substrate 210 is a silicon substrate, the substrate 210 can be separated through a wet etching process, and the intermediate layer 220 can also be separated by a dry etching process.

Then, the light emitting structure 240 on which the substrate is separated is diced in units of elements. At this time, each of the light emitting structures 260 may be etched using a mask (not shown).

11E shows a state in which irregularities are formed in a part of the surface of the first conductivity type semiconductor layer 242 and the first electrode 252 and the passivation layer 280 are formed. The first electrode 252 may have a composition as described above and may be disposed in a flat region of the surface of the first conductive semiconductor layer 242. The passivation layer 280 may be formed of an insulating material, May be made of a non-conductive oxide or nitride. As an example, the passivation layer 280 may be formed of a silicon oxide (SiO ₂ ) layer, an oxynitride layer, or an aluminum oxide layer.

In the light emitting device 200 shown in FIG. 11E, the air void is removed together with the intermediate layer, but the potential generated at the interface between the substrate and the intermediate layer is blocked by the air void described above in the growth process of the light emitting structure 240, The quality of the light emitting structure 240 can be improved.

12A to 12D are SEM photographs and CL images of the light emitting device shown in FIG.

The air void shown by black solid lines in Fig. 12A is shown in a pale view in the image of Fig. 12B, and the portion shown by black solid lines in the left side view in Fig. 12C is air void. In the CL image, 12D, an AlN deep impurity peak (315 to 350 nm peak) is observed in the region where the air void is formed. It can be estimated that dislocation is concentrated around the air void.

In FIG. 12A, the size of the air void is random as described above and has a predetermined width in the lateral direction. However, since it is a nano scale, it is displayed as a line in the vertical direction in the SEM photograph. Electrons may be charged on the surface and the sharpness of the picture may be deteriorated.

The CL image is a principle for measuring the excited optical spectrum by irradiating the sample with x-rays, and the limitations such as the spatial resolution of the optical detector used in the CL image measurement in FIGS. 12B and 12C Around the air void is blurred. Particularly, the position of the air void may be unclear because the peak of the optical spectrum does not appear in the air void and the light is emitted at the dislocation in the periphery.

12D is a spectrum obtained by line-scanning a specific position. 12B and 12C appearing in a dark state are obtained for a predetermined period of time and averaged to reduce the noise generated during the measurement and thus the position of the air void is clearly displayed.

The density of the air void is increased in the light emitting device manufactured according to the above process, compared with the case of forming the air void by the photolithography and etching process using the conventional mask, so that the AlN or the like grows in the horizontal direction So that high-quality growth is possible and the light scattering effect can be increased due to the air void which is more dense than the conventional one. In addition, the manufacturing process of the light emitting device can be simplified because no mask is used. FIG. 13 is a view showing an embodiment of a light emitting device package including the light emitting device.

The light emitting device package 300 according to the embodiment is a flip chip type light emitting device package including a body 310 including a cavity and a first lead frame 321 and a second lead frame 322 provided on the body 310, A light emitting device 200 according to the above-described embodiments, which is electrically connected to the first lead frame 321 and the second lead frame 322, installed in the body 310, And a molding part 350 formed in the cavity.

The body 310 may be formed of 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, 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 .

The first lead frame 321 and the second lead frame 322 are electrically disconnected from each other and supply current to the light emitting device 200. The first lead frame 321 and the second lead frame 322 may reflect the light generated from the light emitting device 200 to increase the light efficiency, It may be discharged.

The light emitting device 200 may be electrically connected to the first lead frame 321 and the second lead frame 322 by ball solder 340.

The molding part 350 may surround and protect the light emitting device 200. In addition, the phosphor 360 is conformally coated on the molding part 350 as a separate layer from the molding part 350. In this structure, the phosphors 360 are distributed so that the wavelength of the light emitted from the light emitting device 200 can be changed in the entire region where the light of the light emitting device package 300 is emitted.

The light in the first wavelength range emitted from the light emitting device 200 is excited by the phosphor 360 and converted into light in the second wavelength range and light in the second wavelength range passes through the lens (not shown) The light path can be changed.

In the above-described light emitting device package 300, since the potential generated at the interface between the substrate and the intermediate layer is blocked by the air void during the growth process, the quality of the light emitting structure made of AlGaN, GaN or the like is improved In particular, in the case of the horizontal type light emitting device, the light extraction efficiency can be improved by the air void.

In particular, when at least one of the first conductivity type semiconductor layer and the second conductivity type semiconductor layer in the light emitting device 200 includes AlGaN and the active layer includes AlGaN / GaN, the peak wavelength of ultraviolet rays emitted from the light emitting structure is And the improvement of the quality of the light emitting structure due to the convergence of the electric potential due to the above arrangement of the air voids in the substrate of the light emitting device 200 and the improvement of the light extraction effect can be remarkable .

The light emitting device package 300 may be mounted on one or a plurality of light emitting devices according to the embodiments described above, but the present invention 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. Such a light emitting device package, a substrate, and an optical member can function as a light unit. Still another embodiment may be implemented as a display device, an indicating device, a lighting system including the semiconductor light emitting device or the light emitting device package described in the above embodiments, for example, the lighting system may include a lamp, a streetlight . Hereinafter, a head lamp and a backlight unit will be described as an embodiment of an illumination system in which the above-described light emitting device package is disposed.

14 is a view showing an embodiment of a headlamp including a light emitting device package.

The light emitted from the light emitting device module 401 in which the light emitting device package is disposed is reflected by the reflector 402 and the shade 403 and then transmitted through the lens 404 to the front of the vehicle body You can head.

As described above, in the light emitting device used in the light emitting device module 401, the electric potential generated at the interface between the substrate and the intermediate layer is blocked by the air void in the growth process, so that the quality of the light emitting structure made of AlGaN, GaN or the like can be improved In particular, in the case of the horizontal flat type light emitting device, the light extraction efficiency can be improved by the air void.

15 is a view showing an embodiment of a video display device including a light emitting device package.

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

The light source module comprises a light emitting device package 535 on a circuit board 530. Here, the circuit board 530 may be a PCB or the like, and the light emitting device package 535 is the same as that described with reference to FIG.

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

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

The light guide plate 540 scatters the light emitted from the light emitting device package module so that the light is uniformly distributed over the entire screen area of the LCD. Accordingly, the light guide plate 530 is made of a material having a good refractive index and transmittance. The light guide plate 530 may be formed of poly methylmethacrylate (PMMA), polycarbonate (PC), or polyethylene (PE). Also, if the light guide plate 540 is omitted, an air guide display device can be realized.

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

In the second prism sheet 560, a direction of a floor and a valley of one side of the supporting film may be perpendicular to a direction of a floor and a valley of one side of the supporting film in the first prism sheet 550. This is for evenly distributing the light transmitted from the light source module and the reflective sheet in all directions of the panel 570.

In this embodiment, the first prism sheet 550 and the second prism sheet 560 constitute an optical sheet, which may be made of other combinations, for example, a microlens array or a combination of a diffusion sheet and a microlens array Or a combination of one prism sheet and a microlens array, or the like.

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

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

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

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

As described above, in the light emitting device used in the light emitting device module 401, the potential generated at the interface between the substrate and the intermediate layer is blocked by air voids in the growth process, The quality of the light emitting structure made of AlGaN, GaN or the like can be improved. In particular, in the case of the horizontal light emitting device, the light extraction efficiency can be improved by the air void.

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

100, 200: light emitting device 110, 210, 210 ': substrate
115: mask 220, 220 ': intermediate layer
225, 225 ': Air void 230: Potential
240: light emitting structure 242, 246: first and second conductive semiconductor layers
244: active layer 252, 256: first and second electrodes
260: transparent conductive layer 272: ohmic layer
274: reflective layer 276: bonding layer
278: conductive support substrate 280: passivation layer
300: light emitting device package 310: body
321, 322: first and second lead frames 340: solder
350: molding part 360: phosphor layer
400: head lamp 410: light emitting element module
402: Reflector 403: Shade
404: Lens 500: Display device
510: bottom cover 520: reflector
530: circuit board module 540: light guide plate
550, 560: first and second prism sheets 570:
580: Color filter

Claims

Board;
An ultraviolet light emitting semiconductor structure on the substrate; And
An intermediate layer between the ultraviolet light emitting semiconductor structure and the substrate,
Wherein the ultraviolet light emitting semiconductor structure includes a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer formed between the first conductive semiconductor layer and the second conductive semiconductor layer,
At least one of the first conductive semiconductor layer and the second conductive semiconductor layer includes AlGaN,
Wherein the intermediate layer comprises AlN and a plurality of air voids in the AlN, the air voids being at least partially irregularly arranged, wherein the air voids are arranged in the range of 10 ⁷ to 10 ¹⁰ per square centimeter .

The method according to claim 1,
Wherein the active layer comprises a multiple quantum well structure and the multiple quantum well structure comprises a quantum wall layer comprising Al _x Ga _(1-x) N (0 <x <1) and AlyGa _(1- < y < 1).

3. The method of claim 2,
And the quantum well layer includes the dopant of the second conductivity type.

The method according to claim 1,
Wherein the ultraviolet light emitted from the ultraviolet light emitting semiconductor structure has a peak wavelength of 315 nm to 350 nm.

The method according to claim 1,
Wherein the intermediate layer has a thickness of 1.5 micrometers to 10 micrometers.

The method according to claim 1,
Wherein the height of each air void is at least 1 micrometer smaller than the thickness of the intermediate layer.

The method according to claim 1,
Wherein the height of each of the air voids is 0.5 micrometers to 9 micrometers.

The method according to claim 1,
Wherein one end of each air void is in contact with or spaced from a boundary between the substrate and the intermediate layer, and the other end of the air void is disposed inside the intermediate layer.

9. The method of claim 8,
And the material of the laterally grown intermediate layer at the periphery of the air void is combined at the upper part of the other end of the air void.

9. The method of claim 8,
And a dislocation of an intermediate layer grown laterally at the periphery of the air void is converged at an upper portion of the other end of the air void.

8. The method of claim 7,
Wherein the distance from one end of the air void to the maximum width of the air void is larger than the distance from the maximum width of the air void to the other end of the air void.

12. The method of claim 11,
Wherein a region where the width of the air void is maximum is disposed so as to be spaced apart from a boundary between the substrate and the intermediate layer and a boundary between the intermediate layer and the light emitting structure.

13. The method according to any one of claims 1 to 12,
Wherein a difference in thermal expansion coefficient between the substrate and the intermediate layer is larger than a difference in thermal expansion coefficient between the intermediate layer and the light emitting structure.