KR102049248B1 - SEPARATION METHOD OF GaN CRYSTAL LAYER USING SACRIFICIAL LAYER - Google Patents

Abstract

Disclosed is a method of separating a GaN crystal layer using a sacrificial layer which can easily separate a graphene layer, a GaN buffer layer and a GaN crystal layer from a carrier substrate by using a sacrificial layer while growing the GaN crystal layer on the graphene layer with minimal damage to the graphene layer; and a light emitting device including the same. According to the present invention, the method of separating a GaN crystal layer using a sacrificial layer comprises: a step of forming a sacrificial layer on a carrier substrate; a step of transferring and depositing the graphene layer on the sacrificial layer to expose a portion of the sacrificial layer; a step of forming a GaN buffer layer on the graphene layer; a step of growing a GaN crystal layer on the GaN buffer layer; and a step of lifting-off the graphene layer, the GaN buffer layer and the GaN crystal layer from the carrier substrate by removing the sacrificial layer on the carrier substrate.

Description

GaN crystal layer separation method using a sacrificial layer {SEPARATION METHOD OF GaN CRYSTAL LAYER USING SACRIFICIAL LAYER}

The present invention relates to a method for separating a GaN crystal layer using a sacrificial layer and a light emitting device including the same, and more particularly, the GaN crystal layer can be grown on the graphene layer while minimizing damage to the graphene layer. The present invention relates to a GaN crystal layer separation method using a sacrificial layer capable of easily separating a graphene layer, a GaN buffer layer and a GaN crystal layer from a carrier substrate, and a light emitting device including the same.

In general, graphene refers to a two-dimensional thin film of a honeycomb structure made of a layer of carbon atoms. At this time, the carbon atoms form a carbon hexagonal network surface having a two-dimensional structure during chemical bonding by sp ² hybrid orbits. The aggregate of carbon atoms with this planar structure is graphene, which is about 0.34 nm thick, with only one carbon atom. Such graphene is structurally and chemically very stable, and has excellent charge mobility about 100 times faster than silicon, and is capable of flowing about 100 times more current than copper.

In addition, graphene has excellent transparency, and may have a higher transparency than indium tin oxide (ITO), which is conventionally used as a transparent electrode. Such graphene has excellent thermal conductivity and has excellent heat dissipation characteristics.

Accordingly, various studies are being conducted to apply graphene to electronic devices using the characteristics of graphene.

However, since the surface of graphene has almost no dangling bonds or functional groups, the surface of graphene has strong hydrophobicity. For this reason, it is very difficult to grow other inorganic materials, such as GaN, on graphene. Accordingly, various methods for growing an inorganic material on graphene have been proposed. For example, as a method of growing GaN on graphene, after oxidizing the surface of graphene, a buffer layer made of ZnO is first formed on the surface of oxidized graphene, and GaN is grown on the ZnO buffer layer. There is this.

However, in this method, since ZnO, which is a heterogeneous material, exists between graphene and GaN, the quality of the grown GaN crystal is degraded. For this reason, in the case of a light emitting device manufactured using a GaN crystal layer grown on ZnO, which is a heterogeneous material, there is a problem in that optical and electrical characteristics are deteriorated.

In addition, various methods for growing GaN on graphene have been proposed, but there is a problem in that the characteristics of the light emitting device are deteriorated due to large damage of graphene or deterioration of the quality of the grown GaN crystal layer.

Related prior arts are Korean Patent Publication No. 10-0707166 (Apr. 13, 2007), which discloses a method for manufacturing a GaN substrate.

An object of the present invention is to grow a GaN crystal layer on the graphene layer while minimizing damage to the graphene layer, and to easily separate the graphene layer, GaN buffer layer and GaN crystal layer from the carrier substrate using a sacrificial layer. A method of separating a GaN crystal layer using a sacrificial layer and a light emitting device including the same are provided.

GaN crystal layer separation method using a sacrificial layer according to an embodiment of the present invention for achieving the above object comprises the steps of forming a sacrificial layer on a carrier substrate; Transferring and laminating a graphene layer on the sacrificial layer to expose a portion of the sacrificial layer; Forming a GaN buffer layer on the graphene layer; Growing a GaN crystal layer on the GaN buffer layer; And removing the sacrificial layer on the carrier substrate to lift off the graphene layer, the GaN buffer layer, and the GaN crystal layer from the carrier substrate.

A light emitting device including a GaN crystal layer according to an embodiment of the present invention for achieving the above object is a substrate; A graphene layer disposed on the substrate; A GaN buffer layer disposed on the graphene layer; A GaN crystal layer disposed on the GaN buffer layer; A first electrode pad disposed on one edge surface of the graphene layer exposed by mesa etching the GaN buffer layer and the GaN crystal layer; And a second electrode pad disposed on an upper surface of the GaN crystal layer, wherein the graphene layer, the GaN buffer layer, and the GaN crystal layer are lifted off from the carrier substrate.

In the GaN crystal layer separation method using the sacrificial layer according to the present invention, a sacrificial layer is formed on a carrier substrate, a graphene layer is transferred and laminated on the sacrificial layer, and a GaN buffer layer is first formed on the graphene layer by a low temperature process. Then, since the GaN crystal layer is grown by a high temperature process, it may be possible to easily separate the graphene layer, the GaN buffer layer and the GaN crystal layer from the carrier substrate using the sacrificial layer while minimizing the damage of the graphene layer due to the high temperature.

In addition, the GaN crystal layer separation method using the sacrificial layer according to the present invention is a low-cost quartz carrier substrate is used, the graphene layer, GaN buffer layer and GaN crystal from the carrier substrate by a lift off process to selectively remove the sacrificial layer After separating the layers, it is possible to wash and recycle the carrier substrate, thereby reducing the manufacturing cost.

In addition, the GaN crystal layer separation method using the sacrificial layer according to the present invention is used as a transparent electrode of the light emitting device because the granene layer maintains its original characteristics, or used as a heat dissipation means by utilizing the excellent thermal conductivity of the graphene layer It may be.

In addition, the light emitting device including the GaN crystal layer according to the present invention can grow the GaN crystal layer on the graphene layer while minimizing damage to the graphene layer, and using the sacrificial layer, the graphene layer and the GaN buffer layer from the carrier substrate. And since the GaN crystal layer can be easily separated, it can have an excellent luminous efficiency by securing a GaN crystal layer having excellent quality.

1 is a process flowchart showing a GaN crystal layer separation method using a sacrificial layer according to an embodiment of the present invention.
2 to 5 are cross-sectional views showing a GaN crystal layer separation method using a sacrificial layer according to an embodiment of the present invention.
6 is a cross-sectional view showing a light emitting device including a GaN crystal layer according to an embodiment of the present invention.
7 and 8 are SEM photographs of GaN-graphene crystal grown at a low temperature of 750 ℃.
Fig. 9 is a photograph showing photographing a state in which a graphene layer, a GaN buffer layer, and a GaN crystal layer are lifted off from a carrier substrate.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a GaN crystal layer separation method using a sacrificial layer according to a preferred embodiment of the present invention and a light emitting device including the same will be described in detail with reference to the accompanying drawings.

1 is a process flow chart showing a GaN crystal layer separation method using a sacrificial layer according to an embodiment of the present invention, Figures 2 to 5 is a process showing a GaN crystal layer separation method using a sacrificial layer according to an embodiment of the present invention. It is a cross section.

As shown in FIG. 1, in the GaN crystal layer separation method using the sacrificial layer according to the embodiment of the present invention, a sacrificial layer forming step (S110), a graphene layer stacking step (S120), a GaN buffer layer forming step (S130), and GaN Crystal layer growth step (S140) and lift off step (S150).

Sacrificial layer  formation

1 and 2, in the sacrificial layer forming step S110, the sacrificial layer 120 is formed on the carrier substrate 110.

The carrier substrate 110 may be made of a quartz material. Since the quartz carrier substrate 110 is much cheaper than the sapphire substrate, the quartz carrier may have an advantage in terms of price competitiveness.

The sacrificial layer 120 preferably includes a material that can be selectively removed. Specifically, the sacrificial layer 120 may be made of a material capable of wet etching, and preferably, SiO ₂ may be used.

The sacrificial layer 120 is formed on the entire surface of the carrier substrate 110 and has the same area as the carrier substrate 110.

Graphene layer  Lamination

1 and 3, in the graphene layer stacking step (S120), the graphene layer 130 is transferred and stacked on the sacrificial layer 120.

In this case, the graphene layer 130 may be lifted off by a mechanical force in the case where the graphene layer 130 is formed to have a considerably thick thickness, and only the monolayer graphene is lifted off when the sacrificial layer 120 is removed. Even if it is possible. Specifically, the graphene layer 130 may have a thickness of 0.2 (monolayer) to 100 (multilayers) nm.

The graphene layer 130 may be a graphene multilayer in which graphene is stacked in a multilayer structure. Various methods are disclosed for forming graphene multilayers. For example, the graphene multilayer may be formed by applying and reducing graphene oxide on a substrate, or the graphene multilayer may be formed by chemical vapor deposition using a metal catalyst.

The graphene layer 130 manufactured by the above method is suitable for use as a transparent electrode material such as a light emitting device or a display panel because it is excellent in electrical conductivity and thermal conductivity and is very transparent.

At this time, in the present invention, instead of directly forming the graphene layer 130 on the carrier substrate 110 on which the sacrificial layer 120 is formed, the graphene layer 130 prepared by the above-described method is transferred using a transfer means. Since the process is to be disposed on the sacrificial layer 120, the process can be simplified.

Here, the graphene layer 130 preferably has a smaller area than the sacrificial layer 120 and the carrier substrate 110. Accordingly, a portion of the sacrificial layer 120 may be exposed to the outside of the graphene layer 130.

GaN Buffer layer  formation

1 and 4, in the GaN buffer layer forming step S130, after forming Ga seeds on the graphene layer 130, GaN crystals are grown on the Ga seeds to form GaN buffer layers 140.

In this step, the GaN buffer layer 140 is first grown on the graphene layer 130 at low temperature, which is the first time the GaN buffer layer 140 is grown at low temperature, while the GaN buffer layer 140 is grown. This is because damage to the graphene layer 130 disposed below may be minimized.

That is, after the carrier substrate 110 having the graphene layer laminated is introduced into a deposition chamber (not shown), a Ga source is exposed to the exposed upper surface of the graphene layer 130 at a first temperature range of 300 to 700 ° C. Ga seeds (not shown) are formed on the graphene layer 130 by HVPE (Hydride Vapor Phase Epitaxy) method. At this time, the formation of the Ga seed may be performed for about 5 to 10 minutes.

Next, when the Ga seed covers the entire exposed upper surface of the graphene layer 130, while raising the temperature in the deposition chamber to a temperature of 700 to 1,100 ° C., a hydrogen nitride compound such as ammonia (NH ₃ ) may be used. It is provided in the deposition chamber. Then, GaN crystals may be grown while the Ga seeds on the graphene layer 130 are bonded to nitrogen. The growth of the GaN crystals may be performed for about 1 to 30 minutes.

According to the present embodiment, even though the temperature in the deposition chamber is increased to 700 to 1,100 ° C. during the growth of the GaN crystal, the graphene layer 130 is formed by the Ga seed because Ga seeds are already formed on the surface of the graphene layer 130. Since it may be protected, it is possible to minimize the damage to the graphene layer 130. The GaN crystal formed by the above process may be the GaN buffer layer 140.

As such, after the GaN buffer layer 140 is formed on the graphene layer 130, the temperature in the deposition chamber is lowered to 300 to 600 ° C. to cool the GaN buffer layer 140 and relax the internal stress. .

GaN Crystalline layer  growth

1 and 4, in the GaN crystal layer growth step S140, the GaN crystal layer 150 is grown on the GaN buffer layer 140.

That is, the GaN crystal layer 150 on the GaN buffer layer 140 in an HVPE method for supplying a hydrogen nitride compound such as ammonia (NH ₃ ) into the deposition chamber while raising the temperature in the deposition chamber back to the second temperature range of 700 to 1,100 ° C. To grow).

Therefore, the growth of the GaN buffer layer 140 and the growth of the GaN crystal layer 150 may be continuously performed in one deposition chamber.

At this time, the GaN buffer layer 140 having the same width as the graphene layer 130 is disposed on the graphene layer 130 even if the temperature in the deposition chamber rises again to 700 to 1,100 ° C. during the growth of the GaN crystal layer 150. Since the GaN buffer layer 140, the graphene layer 130 may be stably protected.

Therefore, since the GaN buffer layer 140 protects the graphene layer 130 under the GaN crystal layer 150, the graphene layer 130 may be minimized.

As such, in the present invention, since the GaN crystal layer 150 is grown on the GaN buffer layer 140, it may be possible to secure excellent crystal quality, and thus the GaN crystal layer 150 having excellent quality without damaging the graphene layer 130. ) Can be formed.

The quality of the GaN crystal layer 150 grown on the graphene layer 130 by the method according to the embodiment of the present invention described above is hardly different from the quality of the general GaN crystal layer formed directly on the sapphire substrate. Therefore, the GaN crystal layer 150 of the present invention can be sufficiently used for manufacturing light emitting devices.

lift off

1 and 5, in the lift-off step S150, the sacrificial layer on the carrier substrate 110 (120 of FIG. 4) is removed to remove the graphene layer 130 and the GaN buffer layer 140 from the carrier substrate 110. ) And the GaN crystal layer 150 are lifted off.

In this case, the sacrificial layer is removed by using any one of a hydrogen fluoride (HF) solution and a buffered etch (BOE) solution.

That is, during the lift-off step (S150), any one of a hydrogen fluoride (HF) solution and a buffered oxide etching (BOE) solution is sprayed on the carrier substrate 110 on which the GaN crystal layer 150 is grown for 1 to 30 minutes. Alternatively, the sacrificial layer exposed to the outside of the graphene layer 130, the GaN buffer layer 140, and the GaN crystal layer 150 may be removed by an immersion etching process.

Accordingly, the sacrificial layer on the carrier substrate 110 is removed, and the graphene layer 130, the GaN buffer layer 140, and the GaN crystal layer 150 on the carrier substrate 110 are easily separated and separated by the removal of the sacrificial layer. You can do it.

Thereafter, the carrier substrate 110 is subjected to a rinse treatment with DI (deionized) for approximately 5 to 10 seconds. The carrier substrate 110 thus cleaned can be recycled, thereby reducing manufacturing costs.

In the GaN crystal layer separation method using the sacrificial layer according to the embodiment of the present invention described above, a sacrificial layer is formed on the carrier substrate, the graphene layer is transferred and laminated on the sacrificial layer, and then GaN is formed on the graphene layer by a low temperature process. Since the GaN crystal layer is grown by the high temperature process after forming the buffer layer first, it is possible to easily separate the graphene layer, GaN buffer layer and GaN crystal layer from the carrier substrate using the sacrificial layer while minimizing the damage of the graphene layer due to the high temperature. Can be.

In addition, in the GaN crystal layer separation method using the sacrificial layer according to the embodiment of the present invention, a low-cost quartz carrier substrate is used, and the graphene layer and the GaN buffer layer are removed from the carrier substrate by a lift-off process to selectively remove the sacrificial layer. After the GaN crystal layer is separated, the carrier substrate can be washed and recycled, thereby reducing manufacturing costs.

In addition, the GaN crystal layer separation method using the sacrificial layer according to the embodiment of the present invention is used as a transparent electrode of the light emitting device because the granule layer maintains its original characteristics, or heat dissipation utilizing the excellent thermal conductivity of the graphene layer It may be used as a means.

6 is a cross-sectional view illustrating a light emitting device including a GaN crystal layer according to an embodiment of the present invention.

As shown in FIG. 6, the light emitting device 200 including the GaN crystal layer according to the embodiment of the present invention includes a substrate 210, a graphene layer 230 disposed on the substrate 210, and a graphene layer. And a GaN buffer layer 240 disposed on 230. GaN crystal layer 250 disposed on GaN buffer layer 240 and a first surface disposed on one side edge surface of the graphene layer 230 exposed by mesa etching the GaN buffer layer 240 and GaN crystal layer 250 The electrode pad 260 and the second electrode pad 270 disposed on the upper surface of the GaN crystal layer 250 may be included.

In this case, the graphene layer 230, the GaN buffer layer 240 and the GaN crystal layer 250 are lifted off from the carrier substrate (not shown) by the GaN crystal layer growth method using the sacrificial layer according to the embodiment of the present invention described above. Lifted off may be used.

The GaN crystal layer 250 may include an n-doped n-GaN crystal layer 252, an active layer 254 having a multi-quantum well structure, and a p-doped p-GaN crystal layer 256.

The graphene layer 230 may serve as an electrode for providing a current to the n-GaN crystal layer 252. As is known, since graphene has excellent conductivity, the current injection efficiency of the light emitting device 200 may be improved.

In addition, since graphene also has excellent thermal conductivity, the graphene layer 230 may also perform a heat dissipation function for releasing heat generated from the active layer 254. Thus, the graphene layer 230 may prevent deterioration and performance degradation of the light emitting device 200 due to heat.

The light emitting device including the GaN crystal layer according to the embodiment of the present invention described above can grow the GaN crystal layer on the graphene layer while minimizing damage to the graphene layer and, using the sacrificial layer, the graphene layer from the carrier substrate. Since the GaN buffer layer and the GaN crystal layer can be easily separated, the GaN buffer layer can have excellent light emission efficiency by securing a GaN crystal layer having excellent quality.

7 and 8 are SEM photographs of GaN-graphene grown with crystals at a low temperature of 750 ° C.

7 and 8, as can be seen in the SEM image, after the GaN crystal layer was grown by GaN crystal growth at a low temperature of 750 ° C. by the GaN crystal layer growth method using the sacrificial layer according to an embodiment of the present invention, When the sacrificial layer was removed by BOE treatment to lift off the graphene layer, GaN buffer layer and GaN crystal layer from the carrier substrate, it was confirmed that the graphene layer remained almost intact.

9 is an actual photograph showing a state in which the graphene layer, the GaN buffer layer and the GaN crystal layer are lifted off from the carrier substrate.

As shown in FIG. 9, when the graphene layer is laminated on the carrier substrate on which the sacrificial layer is formed, the GaN buffer layer and the GaN crystal layer are formed, and the sacrificial layer is selectively removed through BOE treatment, the graphene layer is removed from the carrier substrate. It was confirmed that the pinned layer, GaN buffer layer, and GaN crystal layer were easily lifted off.

Although the above has been described with reference to the embodiments of the present invention, various changes and modifications can be made at the level of those skilled in the art. Such changes and modifications can be said to belong to the present invention without departing from the scope of the technical idea provided by the present invention. Therefore, the scope of the present invention will be determined by the claims described below.

S110: sacrificial layer forming step
S120: graphene layer lamination step
S130: GaN buffer layer forming step
S140: GaN crystal layer growth stage
S150: lift off stage
110: carrier substrate
120: sacrificial layer
130: graphene layer
140: GaN crystal layer

Claims (12)

Forming a sacrificial layer on the carrier substrate;
Transferring and laminating a graphene layer on the sacrificial layer to expose a portion of the sacrificial layer;
Forming a GaN buffer layer on the graphene layer;
Growing a GaN crystal layer on the GaN buffer layer; And
Removing the sacrificial layer on the carrier substrate to lift off the graphene layer, GaN buffer layer, and GaN crystal layer from the carrier substrate;
The carrier substrate is a quartz material,
After the lift off step, the carrier substrate is washed and recycled,
In the forming of the sacrificial layer, the sacrificial layer has the same area as the carrier substrate, the graphene layer has a smaller area than the sacrificial layer and the carrier substrate, a portion of the sacrificial layer is exposed to the outside of the graphene layer GaN crystal layer separation method using a sacrificial layer, characterized in that.
delete The method of claim 1,
The sacrificial layer
GaN crystal layer separation method using a sacrificial layer, characterized in that SiO ₂ .
delete The method of claim 1,
The GaN buffer layer forming step,
Forming a Ga seed on the graphene layer; And
Growing a GaN crystal on the Ga seed to form a GaN buffer layer.
The method of claim 5,
Forming a Ga seed on the graphene layer,
GaN crystal layer separation method using a sacrificial layer characterized in that carried out in the first temperature range condition of 300 ~ 700 ℃ by HVPE (Hydride Vapor Phase Epitaxy) method.
The method of claim 1,
The graphene layer is
GaN crystal layer separation method using a sacrificial layer characterized in that it has a thickness of 0.2 ~ 100nm.
The method of claim 1,
The graphene layer is
GaN crystal layer separation method using a sacrificial layer, characterized in that the graphene multilayer is laminated in a multilayer structure.
The method of claim 5,
The GaN crystal layer growth step,
GaN crystal layer separation method using a sacrificial layer, characterized in that carried out under a second temperature range of 700 ~ 1,100 ℃ supplying a hydrogen nitride compound on the Ga seed.
The method of claim 1,
In the lift off step,
The sacrificial layer is GaN crystal layer separation method using a sacrificial layer, characterized in that the removal using any one of hydrogen fluoride (HF) solution and buffered etch (BOE) solution.
delete delete

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