KR20130022984A - A light emitting diode and method for the same - Google Patents

Abstract

PURPOSE: A light emitting diode and a manufacturing method thereof are provided to improve the efficiency of a DBR(Distributed Bragg Reflector) by forming a planarization layer between an active layer and the DBR. CONSTITUTION: A first semiconductor layer(130), an active layer(140), and a second semiconductor layer(170) are successively formed on a substrate(110). The active layer includes one or more well layers and barrier layers. A buffer layer(120) reduces lattice mismatch between the substrate and the first semiconductor layer. A DBR(160) is formed between the active layer and the second semiconductor layer. A planarization layer(150) is formed between the DBR and the active layer. The planarization layer includes AlGaN with AlN or Al of 95% or more.

Description

LIGHT EMITTING DIODE AND METHOD FOR THE SAME

The present invention relates to a light emitting diode and a method of manufacturing the same.

The light emitting diode is basically a PN junction diode which is a junction between a P-type semiconductor and an N-type semiconductor.

When the light emitting diode is bonded to the P-type semiconductor and the N-type semiconductor, and a current is applied by applying a voltage to the P-type semiconductor and the N-type semiconductor, holes of the P-type semiconductor move toward the N-type semiconductor, and On the contrary, electrons of the N-type semiconductor move toward the P-type semiconductor, and the electrons and holes move to the PN junction.

The electrons moved to the PN junction are combined with holes as they fall from the conduction band to the valence band. At this time, the energy difference corresponding to the height difference, that is, the energy difference, of the conduction band and the home appliance is emitted, and the energy is emitted in the form of light.

Such a light emitting diode is a semiconductor device that emits light and has characteristics such as eco-friendliness, low voltage, long lifespan, and low cost. In the past, light emitting diodes have been widely applied to simple information display such as display lamps and numbers. In particular, with the development of information display technology and semiconductor technology, it has been used in various fields such as display fields, automobile headlamps and projectors.

On the other hand, there are many kinds of light emitting diodes, and can be distinguished according to the wavelength of light to be emitted. For example, when the wavelength of light emitted is 200 to 340 nm, it may be called a deep UV light emitting diode.

The deep ultraviolet light emitting diode may be applied to various business fields such as bio, sterilization, water purification and white lighting industries.

The deep ultraviolet light emitting diode may be formed using AlGaN or AlInGaN. This is manufactured by using AlGaN or AlInGaN containing Al in GaN to increase the band gap by absorbing a wavelength of 340 nm or less, which is the emission wavelength of the deep ultraviolet light emitting diode, in the case of GaN commonly used in light emitting diodes. It was.

However, the conventional deep ultraviolet light emitting diode was formed by using AlGaN or AlInGaN containing Al, which could solve the absorption problem to a wavelength of 380 nm or less, but P-type was a problem due to the inclusion of Al. For the ohmic of the type semiconductor layer, the contact layer of the P-type semiconductor layer was formed of InGaN or GaN to form ohmic and flip-type, but this also caused light absorption in the contact layer, It caused a problem of lowering the luminous efficiency.

On the other hand, US Patent Publication No. 200601338449 describes a technique for improving the light efficiency using the DBR. However, U.S. Patent Publication No. 200601338449 applies DBR to a light emitting diode that emits a wavelength corresponding to visible light with a wavelength band of 380 to 600 nm, and the composition of Al in the active layer is different from that of a deep ultraviolet light emitting diode. It is not difficult to apply, and furthermore, the light emitting diode emitting visible light can be made relatively free of structural changes in comparison with the deep ultraviolet light emitting diode, so that the DBR can be formed on the flattened surface relatively easily. In the deep ultraviolet light emitting diode which emits deep ultraviolet light in the 340nm band, such a structural change is not easy and there is a problem that it is not easy to apply the technique described in US Patent Publication No. 200601338449 to the deep ultraviolet light emitting diode.

US 20060138449 A1

An object of the present invention is to provide a light emitting diode having high luminous efficiency.

Another object of the present invention is to provide a light emitting diode having a good crystallinity and a high reflectance DBR between a P-type semiconductor layer and an active layer.

Still another object of the present invention is to provide a light emitting diode having a planarization layer between the DBR and the active layer to improve the efficiency of the DBR.

In order to achieve the above object, according to an aspect of the present invention, the first type semiconductor layer containing Al, the active layer containing Al, comprises a second type semiconductor layer, between the active layer and the second type semiconductor layer A distributed Bragg reflector (DBR); And a planarization layer provided between the DBR and the active layer.

The planarization layer may be planarized at an interface with the DBR.

The planarization layer may have a thickness of 10 nm or less.

The planarization layer may include AlGaN containing 95% or more of AlN or Al.

The active layer includes at least one well layer and a barrier layer, the well layer comprises a nitride semiconductor layer containing 40% or 60% Al, and the barrier layer comprises a nitride semiconductor containing 56% or 75% Al. It may comprise a layer.

The DBR includes a superlattice structure in which a nitride semiconductor layer containing 60% Al and a nitride semiconductor layer containing 95% Al is repeatedly stacked 20 to 30 times or a nitride semiconductor layer containing 50% Al and 95% Al. It may be a superlattice structure in which the nitride semiconductor layer is repeated 5 to 20 times.

According to another aspect of the invention, forming a plurality of semiconductor layers including at least a first type semiconductor layer and an active layer on a substrate; Forming a planarization layer on the semiconductor layer; Surface-treating the surface of the planarization layer while completing the formation of the planarization layer; Forming a DBR on the surface of the surface treated planarization layer; And forming a second type semiconductor layer on the DBR.

The surface treatment of the surface of the planarization layer may be a treatment of flowing a gas containing In or Sb to the surface of the planarization layer.

Surface treatment of the surface of the planarization layer may be performed for 1 to 2 minutes at a temperature of 1000 degrees.

According to the present invention, there is an effect of providing a light emitting diode having high luminous efficiency.

Moreover, according to this invention, there exists an effect which provides the light emitting diode provided with DBR with a good crystallinity and a high reflectance between a P-type semiconductor layer and an active layer.

Another object of the present invention is to provide a light emitting diode having a planarization layer between the DBR and the active layer in order to improve the efficiency of the DBR.

1 is a cross-sectional view showing a light emitting diode according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, a light emitting diode 100 according to an embodiment of the present invention includes a substrate 110, a buffer layer 120, a first type semiconductor layer 130, an active layer 140, and a planarization layer 150. ), A distributed bragg reflector (DBR) 160, and a second type semiconductor layer 170.

The light emitting diode 100 may further include a superlattice layer (not shown) or an electron breaking layer (not shown).

The substrate 110 may be any substrate capable of growing semiconductor layers. The substrate 110 may be a sapphire substrate, a SiC substrate, a spinel substrate, or the like, and preferably, a sapphire substrate.

The substrate 110 has a buffer layer 120, a first type semiconductor layer 130, an active layer 140, a planarization layer 150, a DBR 160, a second type semiconductor layer 170, and the like on one surface thereof. And a PSS pattern (Patterned Sapphire Substrate) (not shown) on the other surface thereof.

When the light emitted from the active layer 140 is emitted to the outside through the other surface of the substrate 110, the PSS pattern serves to reduce the light that is totally reflected inside the loss in the substrate 110. That is, the PSS pattern (not shown) has a boundary surface when the light passes between two media having different refractive indices, that is, when the light passes from the substrate 110 to the outside (ie, in the air). That is, reflection and transmission occur at the substrate 110 and the external interface), thereby minimizing the reflection to increase the amount of light emitted to the outside through the substrate 110 to increase luminous efficiency.

The PSS pattern (not shown) may be formed of hemispherical protrusions on the other surface of the substrate 110, but the shape thereof is not limited thereto and may be in various forms, for example, a polygonal shape including a cone shape or a pyramid shape. It may be provided.

The buffer layer 120 may be provided to mitigate lattice mismatch between the substrate 110 and the first type semiconductor layer 130. In addition, the buffer layer 120 may be formed of a single layer or a plurality of layers, and when formed of a plurality of layers, the buffer layer 120 may be formed of a low temperature buffer layer and a high temperature buffer layer. The buffer layer 120 may include AlN.

The first type semiconductor layer 130 may be doped with a first conductive impurity, for example, an n-type impurity, and may be formed of a nitride semiconductor including Al, for example, n-AlGaN. In addition, when the first type semiconductor layer 130 is formed of a single layer or multiple layers, for example, the first type semiconductor layer 130 is formed of multiple layers, the first type semiconductor layer 130 may have a superlattice structure.

At this time, the first type semiconductor layer 130 may be provided with a thickness of 1.6㎛.

The superlattice layer (not shown) may be provided between the first type semiconductor layer 130 and the active layer 140, and a structure in which at least two AlGaN layers having different compositions are repeatedly stacked or AlN layer and AlGaN The layers may be repeatedly stacked, and the superlattice layer (not shown) may be provided at a position formed before the active layer 140 to allow dislocations or defects to the active layer 140. By preventing the transfer, it may serve to alleviate the formation of dislocations or defects of the active layer 140 and to play an excellent role in crystallinity of the active layer 140.

The active layer 140 may be formed of a nitride semiconductor layer including Al, and the active layer 140 may be formed of a single layer or a plurality of layers. In addition, the active layer 140 may have a single quantum well structure including one well layer (not shown), or a multiple quantum well having a structure in which a well layer (not shown) and a barrier layer (not shown) are alternately stacked. It may be provided in a structure. In this case, the well layer (not shown) or the barrier layer (not shown) may be formed of a superlattice structure, respectively or both.

In this case, the active layer 140 may be an active layer that emits deep ultraviolet light, light having a wavelength in the range of 200 nm to 340 nm. Therefore, the light emitting diode 100 according to an embodiment of the present invention may be a deep ultraviolet light emitting diode.

The active layer 140 may include a barrier layer including a well layer including a nitride semiconductor layer (eg, an InAlGaN layer) containing 40% Al and a nitride semiconductor layer (eg, an InAlGaN layer) including 56% Al. In the case where the active layer 140 is formed, the active layer 140 may emit light in a range of 280 nm, and the active layer 140 may include 75% of a well layer including a nitride semiconductor layer (eg, an InAlGaN layer) containing 60% of Al. When the barrier layer includes a nitride semiconductor layer (eg, an InAlGaN layer) including Al, the active layer 140 may emit light in a range of about 250 nm.

The planarization layer 150 may be provided on the active layer 140.

The planarization layer 150 is flattened by surface treatment of an interface with the DBR 160, ie, a surface contacting the DBR 160. In this case, the surface-treated surface of the planarization layer 150 forms the planarization layer 150 as described later with reference to FIG. 2 and at the same time the planarization layer 150 at a high temperature, that is, a process temperature of 1000 degrees. A gas containing In or Sb may be flowed to the surface of the planarized surface, that is, the surface of the planarization layer 150 may be flattened by flowing In or Sb.

The planarization layer 150 may have a thickness of 10 nm or less. When the planarization layer 150 is provided with a thickness exceeding 10 nm, the charge injected into the active layer 140 through the planarization layer 150 may be affected by, for example, an electric hole, that is, a hole injection may be difficult. The thickness of the planarization layer 150 is 10 nm or less because not only the voltage drop Vf is worsened, but also the light transmission characteristics are worsened, thereby degrading the overall efficiency of the light emitting diode 100 according to the embodiment of the present invention. It is preferable. In addition, the planarization layer 150 may not be too thin. This is because the planarization layer 150 may not serve as a planarization layer if it is too thin.

The planarization layer 150 may include a nitride including Al, preferably AlN or AlGaN containing 95% or more of Al.

The planarization layer 150 is provided between the active layer 140 and the DBR 160 described later. The planarization layer 150 is provided because the DBR 160 is provided on the active layer 140. That is, when the DBR 160 is provided on the planarized surface, the light reflection property is excellent, but the reverse direction, that is, when provided on the rough surface, the light reflection property tends to be poor. The light emitting diode 100 according to an embodiment of the present invention includes a large amount of Al in the active layer 140 because the active layer 140 emits deep ultraviolet rays. In addition to the occurrence of aluminum droplets (Al droplet) phenomenon is likely to form a roughness of the surface of the active layer 140 is rough. Therefore, the planarization layer 150 of the light emitting diode 100 according to an embodiment of the present invention is provided on the active layer 140 having the rough surface, and serves to planarize the rough surface of the active layer 140. As a result, the DBR 160 is provided on a flat surface, thereby preventing the reflection characteristics of the DBR 160 from being lowered.

The DBR 160 may include a nitride semiconductor layer containing Al by 60%, for example, a nitride semiconductor layer including AlGaN and a nitride semiconductor layer containing Al by 95%, for example, 20 to 30 times. The superlattice structure may be repeatedly stacked, the DBR (160) of this structure can mainly reflect the wavelength of 254nm, two layers may be provided with an average thickness of 24nm and 29nm, respectively.

In addition, the DBR 160 may include a nitride semiconductor layer including 50% Al, for example, a nitride semiconductor layer including AlGaN, and a nitride semiconductor layer including AlGaN, for example, 5 to 5%. It may be made of a superlattice structure stacked repeatedly 20 times, the DBR (160) of this structure can mainly reflect the wavelength of 280nm, two layers may be provided with an average thickness of 26nm and 36nm, respectively.

In this case, the DBR 160 may change the composition of the nitride semiconductor layers according to the wavelength of the light to be reflected, and may also change the number and thickness of the nitride semiconductor layers.

The second type semiconductor layer 170 may be a III-N-based compound semiconductor doped with a second-type impurity, for example, a P-type impurity, such as (Al, In, Ga) N-based Group III nitride semiconductor. The second type semiconductor layer 170 may be an AlGaN layer doped with P-type impurities, that is, a P-AlGaN layer. In addition, the second type semiconductor layer 170 may be formed of a single layer or multiple layers. For example, the second type semiconductor layer 170 may have a superlattice structure.

In this case, the second type semiconductor layer 170 may be provided freely regardless of the wavelength of the light emitted from the active layer 140, that is, freely made of a constituent material and thickness, such that the DBR 160 may be provided. This is because the second type semiconductor layer 170 is not positioned on the path of the light emitted from the active layer 140 because the light emitted from the active layer 140 is reflected and travels toward the substrate 110. .

The electron breaking layer (not shown) may be provided between the active layer 140 and the second type semiconductor layer 170, and may be provided to increase recombination efficiency of electrons and holes, and have a relatively wide band gap. It may be provided with a material. The electron breaking layer (not shown) may be formed of a (Al, In, Ga) N-based group III nitride semiconductor, and may be formed of a P-AlGaN layer doped with Mg. In this case, the planarization layer 150 may serve as the electronic breaking layer (not shown).

Accordingly, the light emitting diode 100 according to the embodiment of the present invention may include at least the substrate 110, the first type semiconductor layer 130, the active layer 140, the planarization layer 150, the DBR 160, and the second type. And a semiconductor layer 170. The active layer 140 contains Al at a high concentration by emitting deep ultraviolet rays in the range of 200 nm to 340 nm, and the surface roughness thereof is rough, and the planarization layer 150 has the active layer 140. And the DBR 160 to remove the rough surface of the active layer 140 so that the DBR 160 is provided on the planarized surface to serve to improve the light reflection characteristics of the DBR 160. It is provided. Therefore, the light emitting diode 100 according to an embodiment of the present invention is reflected by the DBR 160 in comparison with a conventional light emitting diode, in particular, a light emitting diode emitting deep ultraviolet light in the range of 200 nm to 340 nm, and thus, A light emitting diode excellent in luminous efficiency by the amount of light emitted can be provided.

2 is a flowchart illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

1 and 2, in the method of manufacturing a light emitting diode according to an embodiment of the present disclosure, first, a substrate 110 is prepared, and at least a first type semiconductor layer is formed on the substrate 110. A process S10 of forming a plurality of semiconductor layers including the 130 and the active layer 140 is performed.

In this case, the substrate 110 may be a sapphire substrate, the first semiconductor layer 130 is an n-type AlGaN layer, preferably _{n-Al 0 .47 Ga 0 .53} N may be a layer, of 1.6㎛ The active layer 140 may include a nitride semiconductor layer including Al (eg, an InAlGaN layer).

In this case, the buffer layer 120 may be formed on the substrate 110 before the first type semiconductor layer 130 is formed. The buffer layer 120 may be a layer including AlN.

Subsequently, a process (S20) of forming the planarization layer 150 on the semiconductor layers is performed. At this time, the planarization layer 150 may be made of AlN or AlGaN containing 95% or more of Al.

Meanwhile, the process of forming the planarization layer 150 (S20), that is, completing the process of forming the planarization layer 150 (S20) and simultaneously surface-treating the surface of the planarization layer 150. Proceed to (S30).

In this case, the step (S20) of forming the planarization layer 150 and the step (S30) of surface treating the surface of the planarization layer 150 may be performed in-situ in the same chamber. desirable.

In the step (S30) of surface treating the surface of the planarization layer 150, the substrate 110 on which the planarization layer 150 is formed is heated at a high temperature, that is, at a temperature of 1000 degrees for 1 to 2 minutes. On the surface of the gas containing In or Sb, that is, a process for supplying In or Sb to the surface of the planarization layer 150 for 1 to 2 minutes at a temperature of 1000 degrees. For example, when Al is flowed at about 100cc when the active layer 140 is formed, a process of flowing In at 20 to 30cc may be performed.

In operation S20 of forming the planarization layer 150, the surface of the planarization layer 150 is planarized.

Subsequently, a process (S40) of forming the DBR 160 on the planarization layer 150 in which the surface is surface-treated is performed.

In this case, the DBR 160 includes 60% Al, an AlGaN layer having an average thickness of 24 nm and 95% Al, and a superlattice structure in which an AlGaN layer having an average thickness of 29 nm is repeatedly stacked 20 to 30 times. It is possible to form a superlattice structure in which 50% of Al, an AlGaN layer having an average thickness of 26 nm and 95% of Al, and an AlGaN layer having an average thickness of 36 nm are repeatedly stacked 5 to 20 times.

Subsequently, a process (S50) of forming the second type semiconductor layer 170 on the DBR 160 is performed to form the light emitting diode 100 according to the exemplary embodiment.

The second type semiconductor layer 170 is a P-type AlGaN layer is impurity doped, and preferably is Mg a Al _{0 .53} Ga _{0 .47} N doped layer, the thickness may be 300nm.

In this case, although not shown, a mesa for etching the second type semiconductor layer 170, the DBR 160, the planarization layer 150, and the active layer 140 to expose the first type semiconductor layer 130. The etching process may proceed.

In addition, a process of forming electrodes of Ni / Au and Pd / Au on the surface of the first type semiconductor layer 130 and the second type semiconductor layer 170 exposed by the mesa etching may be performed. .

The present invention has been described above with reference to the above embodiments, but the present invention is not limited thereto. Those skilled in the art will appreciate that modifications and variations can be made without departing from the spirit and scope of the present invention and that such modifications and variations also fall within the present invention.

110 substrate 120 buffer layer
130: type 1 semiconductor layer 140: active layer
150: planarization layer 160: DBR
170: type 2 semiconductor layer

Claims (9)

A first type semiconductor layer including Al, an active layer containing Al, and a second type semiconductor layer,
A distributed bragg reflector (DBR) disposed between the active layer and the second type semiconductor layer; And
And a planarization layer provided between the DBR and the active layer.
The light emitting diode of claim 1, wherein the planarization layer has a flattening interface with the DBR.
The light emitting diode of claim 1, wherein the planarization layer has a thickness of 10 nm or less.
The light emitting diode of claim 1, wherein the planarization layer comprises AlN or AlGaN containing 95% or more of Al.
The method of claim 1, wherein the active layer comprises at least one well layer and a barrier layer,
The well layer includes a nitride semiconductor layer containing 40% or 60% of Al,
The barrier layer comprises a nitride semiconductor layer comprising 56% or 75% Al.
The method according to claim 1, wherein the DBR is a nitride semiconductor layer containing 50% of Al or a superlattice structure or a lattice semiconductor layer containing 60% Al and a nitride semiconductor layer containing 95% Al 20-30 times A light emitting diode having a superlattice structure in which a nitride semiconductor layer containing 95% Al is repeatedly stacked 5 to 20 times.
Forming a plurality of semiconductor layers including at least a first type semiconductor layer and an active layer on the substrate;
Forming a planarization layer on the semiconductor layer;
Surface-treating the surface of the planarization layer while completing the formation of the planarization layer;
Forming a DBR on the surface of the surface treated planarization layer; And
Forming a second type semiconductor layer on the DBR.
The method of manufacturing a light emitting diode according to claim 7, wherein the surface treatment of the planarization layer surface is a treatment of flowing a gas containing In or Sb to the surface of the planarization layer.
The method of claim 8, wherein the surface treatment of the planarization layer surface is performed for 1 to 2 minutes at a temperature of 1000 degrees.

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