KR20170088059A - Nitride semiconductor light emitting diode - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting element with improved current diffusion. The nitride semiconductor light emitting element according to an embodiment of the present invention comprises: a p-type nitride semiconductor layer; an active layer formed below the p-type nitride semiconductor layer; an n-type nitride semiconductor layer including a multi-structure formed below the active layer; and a buffer layer formed below the n-type nitride semiconductor layer, wherein the multi-structure may include a structure in which a first doping layer and a second doping layer having doping concentration lower than doping concentration of the first doping layer are alternately stacked.

Description

[0001] NITRIDE SEMICONDUCTOR LIGHT EMITTING DIODE [0002]

An embodiment of the present invention relates to a nitride semiconductor light emitting device having an excellent current diffusion effect.

Nitride semiconductors are widely used in ultraviolet, blue / green light emitting diodes or laser diodes as light sources for full color displays, traffic lights, general lighting and optical communication equipment. Such a nitride-based light emitting device includes an active region of an InGaN-based multi-quantum well structure located between n-type and p-type nitride semiconductor layers, and generates light by recombination of electrons and holes in the quantum well layer in the active region .

The conventional nitride semiconductor device includes, for example, a GaN-based nitride semiconductor device. In the conventional GaN-based nitride semiconductor light emitting device, the content of the p-type dopant of the n-type dopant or the p-type nitride layer of the n-type nitride semiconductor layer is increased to improve the luminous efficiency of the active region, The height is being implemented.

However, in the conventional nitride semiconductor device in which the content of the n-type dopant of the n-type nitride semiconductor layer or the content of the p-type dopant of the p-type nitride semiconductor layer is increased, the luminous efficiency is significantly lowered by current spreading which is not uniform.

In addition, if the content of Si as the n-type dopant in the GaN-based nitride semiconductor is increased by a certain amount or more, the surface morphology deteriorates, and resistance may increase, resulting in deterioration of film quality. Therefore, there is a limit to improve the current diffusion by increasing the content of the dopant.

Therefore, a conventional GnN-based nitride semiconductor light emitting device is required to provide a technique for achieving uniform current diffusion to improve the luminous efficiency.

Korean Patent No. 0700529

SUMMARY OF THE INVENTION The present invention provides a nitride semiconductor light emitting device having improved current diffusion.

The technical objects of the present invention are not limited to the above-mentioned technical problems, and other technical subjects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a nitride semiconductor light emitting device including: a p-type nitride semiconductor layer; An active layer formed below the p-type nitride semiconductor layer; An n-type nitride semiconductor layer including a multi-structure formed under the active layer; And a buffer layer formed below the n-type nitride semiconductor layer, wherein the multi-layer structure includes a first doping layer and a second doping layer having a doping concentration lower than a doping concentration of the first doping layer, As shown in FIG.

According to the present invention as described above, it is possible to improve the current diffusion and improve the luminous efficiency.

1 is a cross-sectional view of a conventional nitride semiconductor light emitting device.
2 and 3 are views showing current crowding of a conventional nitride semiconductor light emitting device.
4 is a graph showing resistivity values depending on the content of Si doping of GaN and AlGaN.
5 is a diagram illustrating a structure of an n-type semiconductor layer of a nitride semiconductor light emitting device having improved current diffusion according to an embodiment of the present invention.
Figures 6 and 7 show improved current spreading, in accordance with an embodiment of the present invention.
8 is an image of light emission of a conventional nitride semiconductor light emitting device.
9 is an image of light emission of a nitride semiconductor light emitting device according to an embodiment of the present invention.
10 is an SIMS profile showing the content of Al and Si in the conventional nitride semiconductor light emitting device.
11 is an SIMS profile showing the content of Al and Si in the nitride semiconductor light emitting device according to the embodiment of the present invention.
12 is a graph showing external quantum efficiency of a nitride semiconductor light emitting device according to an embodiment of the present invention.
13 is a cross-sectional view of a nitride semiconductor light emitting device package including a nitride semiconductor light emitting device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

1 is a cross-sectional view of a conventional nitride semiconductor light emitting device.

Referring to FIG. 1, a conventional nitride semiconductor light emitting device 100 includes a substrate 110, a buffer layer 120, an n-type semiconductor layer 130, an active layer 140, a p-type semiconductor layer 150, Type electrode 160, an n-type electrode 170, and a p-type electrode 180.

The substrate 110 is a substrate for growing a gallium nitride-based semiconductor layer, and may include sapphire, SiC, or spinel, but is not limited thereto. For example, the substrate 110 may be a patterned sapphire substrate (PSS), but this is merely exemplary and not limiting.

The buffer layer 120 may be formed between the substrate 110 and the n-type semiconductor layer 130. The buffer layer 120 may be for alleviating the difference in lattice mismatch and thermal expansion coefficient between the light emitting structure formed on the substrate and the substrate 110.

The buffer layer 120 may be a combination of group III and group V elements or may be formed of one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. The buffer layer 120 may be doped with a dopant, but is not limited thereto.

The n-type semiconductor layer 130 may be formed on the buffer layer 120. The n-type semiconductor layer 130 may be formed of a compound semiconductor such as a group III-V and a group II-VI. An n-type dopant such as Si, Ge, Sn, Se, or Te may be added to the n- Lt; / RTI > The n-type semiconductor layer 130 is a semiconductor material having a composition formula of Inx1Aly1Ga1-x1-y1N (0? x1? 1, 0? y1? 1, 0? x1 + y1? 1), for example, GaN, AlGaN, InGaN, InAlGaN and the like.

The active layer 140 may be formed on the n-type semiconductor layer 130. The active layer 140 is a layer where electrons (or holes) injected through the n-type semiconductor layer 130 and holes (or electrons) injected through the p-type semiconductor layer 150 meet. The active layer 140 transitions to a low energy level as electrons and holes recombine, and generates light having a wavelength corresponding thereto.

The active layer 140 may have any one of a single well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW) structure, a quantum dot structure, Is not limited thereto.

InGaN / InGaN, GaN / AlGaN, InAlGaN / GaN, GaAs (InGaAs) / AlGaAs, GaP (InGaP) / InGaN / GaN, / AlGaP, but the present invention is not limited thereto. The well layer may be formed of a material having a band gap smaller than the band gap of the barrier layer.

The p-type semiconductor layer 150 may be formed on the active layer 140. The p-type semiconductor layer 150 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI. The p-type semiconductor layer 150 may include a p-type dopant such as Mg, Zn, Ca, Can be doped. The p-type semiconductor layer 150 is formed of a semiconductor material having a composition formula of InxAlyGa1-x-yN (0? x? 1, 0? y? 1, 0? x + y? 1) or a semiconductor material having a composition formula of AlInN, AlGaAs, GaP, GaAs, GaAsP , AlGaInP, < / RTI >

The ohmic layer 160 may be formed between the p-type semiconductor layer 150 and the p-type electrode 180. The ohmic layer 160 diffuses the current injected through the p-type electrode 180 to the p-type semiconductor layer 150 widely. The ohmic layer 160 can be selected from a material having low sheet resistance and high light transmittance.

The ohmic layer 160 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 ), 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 or Ni / IrOx / Au / ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Au, and Hf, but the present invention is not limited thereto.

The p-type electrode 180 is formed on the p-type semiconductor layer 150, and the n-type electrode 170 is formed on the n-type semiconductor layer 130.

Sectional view of a conventional nitride semiconductor light emitting device 100 may have a mesa structure.

2 and 3 are views showing current crowding of a conventional nitride semiconductor light emitting device.

The n-type semiconductor layer 130 of the conventional nitride semiconductor light emitting device 100 may be n-GaN doped with a constantly doped Si dopant.

carriers are injected along the shortest current path when a current is applied to the light emitting element 100 through the p-type electrode 180 and the n-type electrode 170. Therefore, the p- Current crowding may occur only in the vicinity of the shortest distance of the electrode 170. Such current concentration lowers the luminous efficiency because it makes the entire luminescent layer difficult to use.

Referring to FIG. 2, arrows indicate the current flow, and the thickness of the arrows indicates the relative intensity of the current. Although a large amount of current flows in the shortest distance region 220, almost no current flows in the edge region 210.

Referring to FIG. 3, when the region 300 to 400 on the x-axis is the region of the n-type electrode 170 and the region 50 to 150 is the region of the p-type electrode 180, the triangle represents the direction and intensity of the current. The larger the size of the triangle, the larger the current intensity. The current is mostly concentrated around the n-type electrode 170.

4 is a graph showing resistivity values depending on the content of Si doping of GaN and AlGaN.

The resistivity of the n-type semiconductor layer 130 must be reduced in order to alleviate the current concentration and improve the current diffusion in the light emitting device having the mesa structure. If the content of the doped Si dopant in the n-type semiconductor layer 130 is increased, the resistivity can be reduced.

GaN, which is a nitride used in the conventional n-type semiconductor layer 130, has a limitation in increasing the Si content because the resistivity does not decrease any more when the Si content exceeds a certain level.

Referring to the graph of FIG. 4, the relationship (310) between the Si content and the resistivity of GaN shows that the resistivity is no longer decreased when the Si content of GaN is 1020 [cm -3] or more. On the other hand, the relationship between the Si content and the Si content of AlGaN (320) shows that the resistivity decreases continuously as the Si content of AlGaN increases.

Therefore, in the embodiment of the present invention, AlGaN in which the content of the Si dopant is increased in the n-type semiconductor layer 130 is used to reduce the resistivity and relax the current concentration.

5 is a diagram illustrating a structure of an n-type semiconductor layer of a nitride semiconductor light emitting device having improved current diffusion according to an embodiment of the present invention.

The n-type semiconductor layer 430 of the nitride semiconductor light emitting device 400 may include a structure in which the first doping layer 132 and the second doping layer 134 are alternately stacked, according to an embodiment of the present invention. have.

The dopant content of the first doping layer 132 is higher than that of the second doping layer 134.

The first doping layer 132 may be formed of AlGaN. The first doping layer 132 may be doped with an Si dopant. For example, the concentration of the Si dopant may be 1E19 or more, preferably 1E19 to 3E19 [atoms / cm < 3 >], but this is for exemplary purposes only, and is not limited thereto.

The second doping layer 134 may be formed of GaN. The second doping layer 134 may be formed of undoped u-GaN, or the Si dopant may be doped to a low concentration. The concentration of the Si dopant doped in the second doping layer 134 should be lower than the concentration of the Si dopant in the first doping layer 132. [

The Si dopant concentration of the second doping layer 134 should be lower than the Si dopant concentration of the first doping layer 132. [ No additional Si doping is required for the second doping layer 134 for the concentration of the Si dopant in the second doping layer 134. The Si dopant of the second doping layer 134 may be one that has been diffused during the growth of the first doping layer 132.

For example, the Si dopant concentration of the second doping layer 134 may be 1E18 to 1E19 [atoms / cm3], but is not limited thereto and may have a concentration ranging from 0 to 1E18 [atoms / cm3].

In general, the Si dopant concentration of the conventional n-GaN layer is 6E18 to 8E18 [atoms / cm3]. Therefore, the Si dopant concentration of the second doping layer 134 is lower than the Si dopant concentration of the conventional n-GaN layer Is preferably lower than the Si dopant concentration of the first doping layer 132. [

The thickness of the first doping layer 132 may be between 3 and 30 nm and the thickness of the second doping layer 134 may be between 3 and 30 nm. It is preferable that the thickness of the doping layer 134 is all 10 [nm], but this is only an example and is not limited thereto.

5, the first doping layer 132 and the second doping layer 134 are alternately stacked twice on the n-type semiconductor layer 430. However, But is not limited thereto. For example, the first doping layer 132 and the second doping layer 134 may be alternately stacked 10 to 30 times.

Figures 6 and 7 show improved current spreading, in accordance with an embodiment of the present invention.

Referring to FIG. 6, current diffusion is improved by the n-type semiconductor layer 430 according to the embodiment of the present invention, and the current is diffused to the edge 210 of the n-type semiconductor layer 430 and flows .

Referring to FIG. 7, experimentally, it is found that the n-type semiconductor layer 430 spreads to the opposite edge of the n-type electrode 170 of the n-type semiconductor layer 430. Referring to FIG. 3 again, as compared with FIG. 7, the embodiment of the present invention has an effect that the current distribution is further spread to the left on the x-axis.

FIG. 8 is an image of light emission of a conventional nitride semiconductor light emitting device, and FIG. 9 is an image of light emission of a nitride semiconductor light emitting device according to an embodiment of the present invention.

8 and 9, in the plan view taken on the upper part of the light emitting device, the left circular body is the n-type electrode 170 and the right circular body is the p-type electrode 180 part. Red indicates that the density of the current is higher, and the density of the current is lower toward the green color.

8 and 9, it can be seen that the light emitting device according to the embodiment of the present invention is more concentrated in the vicinity of the p-type electrode than the conventional light emitting device. Therefore, it can be seen that the current diffusion is further improved in the embodiment of the present invention as compared with the conventional light emitting device.

FIG. 10 is a SIMS profile showing the content of Al and Si in the conventional nitride semiconductor light emitting device, and FIG. 11 is an SIMS profile showing the content of Al and Si in the nitride semiconductor light emitting device according to the embodiment of the present invention.

10, since Al is used in the p-type semiconductor layer 150 or the active layer in the conventional nitride semiconductor light emitting device, the concentration of Al is high in the corresponding layer portion, but the concentration is low in the n-type semiconductor layer 130 . Since the Si dopant is doped to a predetermined concentration in the n-type semiconductor layer 130 of the conventional nitride semiconductor light emitting device, the Si concentration is constant.

Referring to FIG. 11, a nitride semiconductor light emitting device 400 according to an embodiment of the present invention includes a first doping layer including AlGaN doped with a relatively high concentration of Si dopant in an n-type semiconductor layer 130, Since the second doping layer containing u-GaN doped at a relatively low concentration is alternately stacked, the Al concentration and the Si concentration appear to have the same tendency and oscillate up and down.

12 is a graph showing external quantum efficiency of a nitride semiconductor light emitting device according to an embodiment of the present invention.

External quantum efficiency represents the number of photons emitted out of contrast to the number of charges injected. Therefore, comparing the external quantum efficiency 610 according to the conventional light emitting device 100 and the external quantum efficiency 620 of the light emitting device 400 according to the embodiment of the present invention, The external quantum efficiency is higher because the current diffusion is improved and the light emitting efficiency is better in the active layer.

13 is a cross-sectional view of a nitride semiconductor light emitting device package including a nitride semiconductor light emitting device according to an embodiment of the present invention.

The nitride semiconductor light emitting device package of the present invention includes a body 15, a nitride semiconductor light emitting device 400 formed on the body 15, a first lead frame 15a connected to the nitride semiconductor light emitting device 400, And a molding part 35 surrounding the frame 15b and the nitride semiconductor light emitting device 400.

The body 15 may be formed of a silicon material, a synthetic resin material, or a metal material, but is not limited thereto. If the body 15 is made of a conductive material such as a metal, an insulating material may be further formed on the surface of the body 15 to prevent electrical connection between the first lead frame 15a and the second lead frame 15b.

The nitride semiconductor light emitting device 400 may be mounted on the body 15 or on the first lead frame 15a or the second lead frame 15b. The nitride semiconductor light emitting device 400 is directly connected to the first lead frame 15a and the nitride semiconductor light emitting device 400 is connected to the second lead frame 15b through the wires 25. [ In this case, the first lead frame 15a is connected to a first electrode (not shown) electrically connected to the first semiconductor layer 10 of the nitride semiconductor light emitting device 400, and the second lead frame 15b is connected to the first electrode And a second electrode (not shown) electrically connected to the second semiconductor layer 40 of the nitride semiconductor light emitting device 400.

The molding part 35 covers the nitride semiconductor light emitting device 400. Although not shown, the molding part 35 may further include a wavelength conversion particle such as a fluorescent material.

The light emitting device of the embodiment of the present invention may further include an optical member such as a light guide plate, a prism sheet, and a diffusion sheet to function as a backlight unit. Further, the light emitting element of the embodiment can be further applied to a display device, a lighting device, and a pointing device.

At this time, the display device may include a bottom cover, a reflector, a light emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, the reflector, the light emitting module, the light guide plate, and the optical sheet may form a backlight unit.

The reflector is disposed on the bottom cover, and the light emitting module emits light. The light guide plate is disposed in front of the reflection plate to guide light emitted from the light emitting element forward, and the optical sheet includes a prism sheet or the like and is disposed in front of the light guide plate. The display panel is disposed in front of the optical sheet, and the image signal output circuit supplies an image signal to the display panel, and the color filter is disposed in front of the display panel.

The lighting device may include a light source module including a substrate and a light emitting device of the embodiment, a heat dissipation unit that dissipates heat of the light source module, and a power supply unit that processes or converts an electric signal provided from the outside and provides the light source module . Furthermore, the lighting device may include a lamp, a head lamp, a streetlight or the like.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: nitride semiconductor light emitting element
110: substrate
120: buffer layer
130: an n-type semiconductor layer
140:
150: a p-type semiconductor layer
160: Ohmic layer
170: n-type electrode
180: p-type electrode

Claims (8)

a p-type nitride semiconductor layer;
An active layer formed below the p-type nitride semiconductor layer;
An n-type nitride semiconductor layer including a multi-structure formed under the active layer; And
And a buffer layer formed under the n-type nitride semiconductor layer,
The multi-
And a second doping layer having a doping concentration lower than a doping concentration of the first doping layer and the second doping layer,
Nitride semiconductor light emitting device. The method according to claim 1,
The first doping layer may include a first doping layer,
Si is formed of AlGaN having a dopant,
Nitride semiconductor light emitting device. 3. The method of claim 2,
Wherein a concentration of the Si in the first doped layer is in the range of 1e19 to 3e19 [atoms / cm < 3 >],
Nitride semiconductor light emitting device. The method according to claim 1,
Wherein the second doping layer comprises a first doping layer,
GaN,
Nitride semiconductor light emitting device. 5. The method of claim 4,
Wherein the Si concentration of the second doped layer is in the range of 1e18 to 1e19 [atoms / cm < 3 &
Nitride semiconductor light emitting device. The method according to claim 1,
The thickness of the first doping layer is 10 [nm]
Wherein the thickness of the second doping layer is 10 [nm]
Nitride semiconductor light emitting device. The method according to claim 1,
Wherein the first doping layer and the second doping layer are alternately stacked 10 to 30 times,
Nitride semiconductor light emitting device. Body;
A first lead frame and a second lead frame disposed on the body;
The nitride semiconductor light emitting device according to any one of claims 1 to 7, which is mounted on the body so as to be electrically connected to the first lead frame and the second lead frame. And
And a molding portion surrounding the nitride semiconductor light emitting device.
Nitride semiconductor light emitting device package.

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