KR20150021613A - Nitride semiconductor light emitting device using electron reservoir and spreading layer - Google Patents

Abstract

Disclosed is a nitride semiconductor light emitting device capable of improving the brightness and solving an issue relating to leakage current using electronic storage and spreading layer. According to an embodiment of the present invention, the nitride semiconductor light emitting device comprises: an n type nitride semiconductor layer formed with nitride where n type impurities are doped; a strain absorbing layer formed on the n type nitride semiconductor layer; an active layer formed on the strain absorbing layer; and a p type nitride semiconductor layer formed with nitride where p type impurities are doped on the active layer. Electronic storage and spreading layer are formed between the strain absorbing layer and the active layer. The electronic storage and spreading layer include InxAlyGa1-x-yN where n type impurities are doped.

Description

TECHNICAL FIELD [0001] The present invention relates to a nitride semiconductor light emitting device using an electron storage and diffusion layer,

The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device using an electron storing and spreading layer.

Generally, the nitride semiconductor light emitting device has a light emitting region covering ultraviolet, blue and green regions. In particular, the GaN-based nitride semiconductor light emitting device has been widely used as an optical device of a blue or green light emitting diode (LED), a high-speed device such as a MESFET (Metal Semiconductor Field Effect Transistor), a HEMT Switching devices, and high output devices.

1 schematically shows a conventional nitride semiconductor light emitting device.

1, a general nitride semiconductor light emitting device includes a substrate 110, an undoped nitride semiconductor layer 120, an n-type nitride semiconductor layer 130, an active layer 140, a p-type nitride semiconductor layer 150 a first electrode 161 contacting the p-type nitride semiconductor layer 150, and a second electrode 162 contacting the n-type nitride semiconductor layer 130.

In the case of the nitride semiconductor light emitting device having the above structure, electrons supplied through the n-type nitride semiconductor layer 130 and holes supplied through the p-type nitride semiconductor layer 150 recombine in the active layer 140, Occurs.

However, in the case of electrons supplied through the n-type nitride semiconductor layer 130, the rate of holes supplied through the p-type nitride semiconductor layer 150 is higher than that of the holes, and the amount of electrons to be supplied is larger. In addition, electrons and holes are recombined at the shortest moving distance, and light emission is concentrated only in the vicinity of the second electrode 162 without introducing a separate current dispersion layer.

On the other hand, the current-spreading layer is mainly formed of an AlGaN layer. When the AlGaN layer is formed directly below the active layer, a series resistance of the light emitting device may increase.

As a background art related to the present invention, there is Korean Patent Laid-Open Publication No. 10-2010-0060162 (published on Jun. 10, 2010), which discloses a nitride semiconductor device in which an AlGa layer can be formed as a boring- A light emitting diode device is disclosed.

An object of the present invention is to provide a nitride semiconductor light emitting device capable of improving brightness and improving leakage current blocking effect by forming an electron storing and spreading layer capable of electron storage and spreading function under the active layer.

According to an aspect of the present invention, there is provided a nitride semiconductor light emitting device including: an n-type nitride semiconductor layer formed of a nitride doped with an n-type impurity; A strain buffer layer formed on the n-type nitride semiconductor layer; An active layer formed on the strain buffer layer; And a p-type nitride semiconductor layer formed on the active layer by a nitride doped with a p-type impurity, wherein an electron storage and diffusion layer is formed between the strain buffer layer and the active layer.

According to another aspect of the present invention, there is provided a nitride semiconductor light emitting device including: an n-type nitride semiconductor layer formed of a nitride doped with an n-type impurity; A strain buffer layer formed on the n-type nitride semiconductor layer; An active layer formed on the strain buffer layer; And a p-type nitride semiconductor layer formed on the active layer by a nitride doped with a p-type impurity, wherein an electron storage and diffusion layer is formed in the strain buffer layer in the form of an intermediate layer.

In the above embodiments, the electron storage and spreading layer is preferably formed to include In _x Al _y Ga _1-xy N (<0x <1, 0 <y <1) doped with n-type impurities. At this time, the electron storage and spreading layer may increase as the mole ratio (x) of indium toward the active layer. In addition, the electron storage and diffusion layer may have a mole ratio (x) of indium of 0.001 to 0.02. Also, the electron storage and spreading layer may have a molar ratio (y) of aluminum of 0.12 to 0.18.

Also, in the above embodiments, the electron storage and spreading layer may be formed to a thickness of 50 to 500 ANGSTROM.

In addition, in the above embodiments, the doping concentration of the n-type impurity doped in the electron storage and spreading layer may be 1/15 to 1/2 of the doping concentration of the n-type nitride semiconductor doped in the n-type nitride semiconductor layer.

In addition, in the above embodiments, the strain buffer layer may be formed of an InGaN layer, a GaN layer, or a GaN / InGaN superlattice layer.

The nitride semiconductor light emitting device according to the present invention includes an electron storage and spreading layer formed of an electron storage and spreading layer, in particular, a four-component InAlGaN, under the active layer. Unlike AlGaN, the InAlGaN-based electron storage and spreading layer can cause electrons to spread over the entire surface of the n-type nitride semiconductor layer without any problem in electrical conductivity. In addition, the InAlGaN-based electron storage and spreading layer slows the rate of electrons injected into the active layer and reduces the amount of electrons injected into the active layer.

As a result, the nitride semiconductor light emitting device using the electron storage and spreading layer according to the present invention can contribute to brightness enhancement, and can also provide a blocking effect on threading dislocation, thereby suppressing leakage current.

In the case of the nitride semiconductor light emitting device according to the present invention, the electron storage and spreading layer having the same refractive index as that of the electron blocking layer formed on the active layer is formed below the active layer, It can exhibit the effect of coupling along the spreading layer.

1 is a cross-sectional view showing a conventional nitride semiconductor light emitting device.
2 is a cross-sectional view illustrating a nitride semiconductor light emitting device using an electron storage and spreading layer according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a nitride semiconductor light emitting device using an electron storage and spreading layer according to another embodiment of the present invention.
4 shows the light emitting area of the nitride semiconductor light emitting device according to the comparative example and the first embodiment.

Hereinafter, a nitride semiconductor light emitting device using an electron storage and spreading layer according to the present invention will be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that the 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. To fully disclose the scope of the invention to a person 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.

FIG. 2 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to another embodiment of the present invention.

2 and 3, the illustrated nitride semiconductor light emitting device includes an n-type nitride semiconductor layer 130 formed of a nitride doped with an n-type impurity such as Si, a quantum barrier layer / quantum well layer alternately stacked And a p-type nitride semiconductor layer 150 formed of a nitride doped with an n-type impurity such as Mg.

The nitride semiconductor light emitting device shown in FIGS. 2 and 3 includes a strain relaxation layer (SRL) 210 (210a and 210b in FIG. 2) formed on the n-type nitride semiconductor layer 130 .

In the case of the active layer 140 having a multiple quantum well structure with a pair of InGaN well layers / GaN barrier layers, a large strain between the InGaN well layer and the GaN barrier layer due to the difference in lattice constants between InGaN and GaN, . This strain generates a large piezoelectric field in the active layer 140 and lowers the internal quantum efficiency of the active layer 140.

Therefore, in order to improve the luminous efficiency of the nitride semiconductor light emitting device, it is necessary to relax the strain in the active layer 140. In the example shown in FIGS. 2 and 3, a strain buffer layer 210 210a and 210b. The strain buffer layer is for strain relaxation of the active layer 140 and may be formed of an InGaN or GaN / InGaN super lattice layer containing indium below the average indium composition ratio of the active layer 140.

The strain minimization of the active layer 140 can be achieved by controlling the thickness of each layer between the strain buffer layer and the active layer and the composition of indium. For example, if the thickness of the quantum barrier layer is small, the average mole ratio of indium in the strain buffer layer can be increased. Conversely, if the thickness of the quantum barrier layer is large, the average molar ratio of indium in the strain buffer layer can be lowered.

The nitride semiconductor light emitting device shown in FIGS. 2 and 3 includes an electron storage and spreading layer formed between the n-type nitride semiconductor layer 130 and the active layer 140.

The electron storage and spreading layer 220 spreads electrons supplied from the n-type nitride semiconductor layer 130 to the front surface and decreases the amount of electrons supplied to the active layer while slowing the movement speed of electrons .

For this, the electron storage and spreading layer 220 may include In _x Al _y Ga _1-xy N (<0x <1, 0 <y <1) doped with an n-type impurity.

The electron storage and spreading layer 220 may be formed between the strain buffer layer 210 and the active layer 140, as in the example shown in FIG. In addition, the electron storage and spreading layer 220 may be formed in the form of an intermediate layer within the strain buffer layers 210a and 210b, as shown in FIG.

It is preferable that the electron storage and spreading layer increases as the molar ratio (x) of indium increases toward the active layer as a whole. In this case, electrons supplied from the n-type nitride semiconductor layer 130 are spread to the front by decreasing the moving speed in the electron storage and spreading layer, and after the spreading, electrons of a proper concentration can be uniformly supplied to the active layer .

 It is more preferable that the mole ratio (x) of indium in the entire electron storage and spreading layer 220 is 0.001 to 0.02. If there is a portion in which the molar ratio (x) of indium is less than 0.001, the series resistance of the diode may increase. On the contrary, when there is a portion where the molar ratio (x) of indium is more than 0.02, a problem of leakage may occur due to occurrence of indium aggregation in the thin film.

In addition, the molar ratio (y) of aluminum in the entire electron storage and spreading layer 220 is preferably 0.12 to 0.18. When the molar ratio (y) of aluminum is less than 0.12, the electron storage effect may be insufficient. On the contrary, when the molar ratio (y) of aluminum exceeds 0.18, the electrical characteristics may be lowered due to an excessive increase in resistance.

The reason why the content of indium and aluminum in the electron storage and spreading layer 220 is limited is that the characteristics of InGaN which is a four-component material and the electrical characteristics of AlGaN are opposite to each other. Since InGaN is a material with good electrical conductivity and AlGaN is a material with low conductivity, it is limited to the Al composition and the In composition of the In _x Al _y Ga _{1 -xy} N layer in order to store and spread the electrons injected into the active layer.

In addition, the electron storage and spreading layer 220 is preferably formed to a thickness of 50 to 500 Å. When the thickness of the electron storage and spreading layer 220 is less than 50 Å, the electron storage effect and the spreading effect may be insufficient. Conversely, when the thickness of the electron storage and spreading layer 220 exceeds 500 ANGSTROM, a leakage current characteristic can be generated.

The doping concentration of the n-type impurity doped in the electron storage and spreading layer is less than the doping concentration of the doping n-type dopant doped in the n-type nitride semiconductor layer 130 to 1/15 to 1 / 2 &lt; / RTI &gt; The doping concentration of the n-type nitride semiconductor doped into the n-type nitride semiconductor layer 130 may be about ³ × ^{10 18} to 1 × 10 ¹⁹ / cm ³ , which may vary depending on the thickness of the n-type nitride semiconductor layer 130 have. If the doping concentration of the doped n-type impurity in the electron storage and spreading layer exceeds 1/2 of the doping concentration of the n-type dopant doped in the n-type nitride semiconductor layer 130, excessive doping of the n- The current spreading effect may be lost and current leakage may occur. Conversely, if the doping concentration of the doped n-type impurity in the electron storage and spreading layer is less than 1/15 of the doping concentration of the n-type dopant doped in the n-type nitride semiconductor layer 130, the diode series resistance may excessively increase .

Meanwhile, the nitride semiconductor light emitting device according to the present invention shown in FIGS. 2 to 4 includes a first electrode 161 electrically connected to the p-type nitride semiconductor layer 150 and a first electrode 161 electrically connected to the n-type nitride semiconductor layer 130 And may further include a second electrode 162 connected thereto.

In addition, the nitride semiconductor light emitting device according to the present invention may further include a substrate 110 such as a sapphire growth substrate under the n-type nitride semiconductor layer 120. In addition, a buffer layer (not shown) such as an undoped nitride layer 120, AlN, or low-temperature grown GaN may be further formed between the substrate 110 and the n-type nitride semiconductor layer 130.

Table 1 shows the results of evaluating the electrical characteristics of the nitride semiconductor light emitting device having the structure shown in FIG. 1 (comparative example) and the nitride semiconductor light emitting device having the structure shown in FIG. 2 (Example 1). In Table 1, the characteristics of the nitride semiconductor light emitting device having the structure shown in FIG. 1 were 100%, and electrical characteristics were shown at relative values.

Example 1 is a nitride semiconductor light emitting device having the structure shown in FIG. 2, in which an electron storage and spreading layer has an In _0.01 Al _0.15 Ga _0.84 N composition on an InGaN strain buffer layer having a thickness of 500 A and a Si doping concentration of 1 x 10 ¹⁸ / cm ^3, and was formed to a thickness of 100 ANGSTROM.

In the case of Comparative Example 1, a nitride semiconductor light emitting device was fabricated under the same conditions as in Example 1, and an electron storage spreading layer was formed below the strain buffer layer. In the case of Comparative Example 2, the nitride semiconductor light emitting device was manufactured under the same conditions as in Example 1, and the electron storage spreading layer was formed to a thickness of 550 ANGSTROM.

[Table 1]

VF1: Voltage drop due to rated current

VR: Reverse (-10uA) voltage drop

IR yield: yield of current value by reverse voltage (-5 V) (number of chips whose current value by a reverse voltage is below a certain level / ratio of total number of chips)

PO: Integral sphere emission output

Referring to Table 1, in the case of Example 1, the luminance is increased by about 3% as compared with the reference.

On the contrary, in the case of Comparative Example 1, since the electron storage and spreading layer having a relatively large resistance is located between the n-GaN and the strain buffer layer, the electron transfer to the strain buffer layer becomes difficult and the number of electrons injected into the active layer is reduced , Thereby increasing the VF.

In the case of Comparative Example 2, the electron storage and spreading layer was formed thicker than 500 ANGSTROM, resulting in an increase of In clustering phenomenon and a reverse voltage drop characteristic due to defect increase was not good. That is, the reverse voltage drop characteristic is improved by blocking the threading dislocation at an appropriate thickness of the electron storage and spreading layer. However, if the thickness exceeds 500 ANGSTROM, if the thickness is too large, the reverse voltage drop characteristic is reduced due to defects of the electron storage and spreading layer itself .

FIG. 4 shows the light emitting area of the nitride semiconductor light emitting device having the structure shown in FIG. 1 (reference) and the nitride semiconductor light emitting device having the structure shown in FIG. 2 (Example 1).

In the legend of FIG. 4, a higher luminance is emitted from blue to red. Referring to FIG. 4, the nitride semiconductor light emitting device according to the first embodiment has a relatively large light emitting area that has a higher luminance than the nitride semiconductor light emitting device according to the reference. Effect.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

110: substrate 120: undoped nitride semiconductor layer
130: n-type nitride semiconductor layer 140: active layer
150: p-type nitride semiconductor layer 161: first electrode
162: second electrode 210, 210a, 210b: strain buffer layer
220: Electronic storage and spreading layer

Claims (9)

an n-type nitride semiconductor layer formed of a nitride doped with an n-type impurity;
A strain buffer layer formed on the n-type nitride semiconductor layer;
An active layer formed on the strain buffer layer; And
And a p-type nitride semiconductor layer formed on the active layer, the p-type nitride semiconductor layer being formed of a nitride doped with a p-type impurity,
And an electron storage and spreading layer is formed between the strain buffer layer and the active layer.
an n-type nitride semiconductor layer formed of a nitride doped with an n-type impurity;
A strain buffer layer formed on the n-type nitride semiconductor layer;
An active layer formed on the strain buffer layer; And
And a p-type nitride semiconductor layer formed on the active layer, the p-type nitride semiconductor layer being formed of a nitride doped with a p-type impurity,
And an electron storage and diffusion layer is formed in the strain buffer layer in the form of an intermediate layer.
3. The method according to claim 1 or 2,
Wherein the electron storage and spreading layer comprises In _x Al _y Ga _1-xy N (<0x <1, 0 <y <1) doped with n-type impurities.
The method of claim 3,
Wherein the electron storage and spreading layer increases as the molar ratio (x) of indium to the active layer increases.
The method of claim 3,
The electron storage and spreading layer
Wherein a molar ratio (x) of indium is 0.001 to 0.02.
The method of claim 3,
The electron storage and spreading layer
Wherein a molar ratio (y) of aluminum is 0.12 to 0.18.
3. The method according to claim 1 or 2,
Wherein the electron storage and spreading layer is formed to a thickness of 50 to 500 ANGSTROM.
3. The method according to claim 1 or 2,
Wherein the doping concentration of the doped n-type impurity in the electron storage and spreading layer is 1/15 to 1/2 of the doping concentration of the n-type doping doped in the n-type nitride semiconductor layer.
3. The method according to claim 1 or 2,
Wherein the strain buffer layer is formed of an InGaN layer, a GaN layer, or a GaN / InGaN superlattice layer.

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