KR20160120572A - Photoconductive device based on a nanowire grown using graphene and Method for manufacturing the same - Google Patents

Abstract

According to an embodiment of the present invention, a photoconductive device comprises: a substrate; a first graphene layer formed on the substrate; a plurality of light emitting structures grown on the graphene layer; a second graphene layer formed on the light emitting structure; a first metal electrode in contact with the first graphene layer; and a second metal electrode in contact with the second graphene layer. The photoconductive device not only has better photoconductivity, but also can flow a much more amount of photocurrents by forming a nanowire with a higher density and a longer growth length, and using both the nanowire and graphene as a channel, by using the graphene layer for forming the nanowire on a silicon (Si) substrate.

Description

Technical Field The present invention relates to a photoconductive device based on nanowires grown using graphene and a method of manufacturing the same.

The present invention relates to a photoconductive element and a method of manufacturing the same, and more particularly, to a photoconductive element based on a nanowire structure including graphene and a method of manufacturing the same.

Development of light emitting diodes and laser diodes having a wavelength range of blue light to ultraviolet light region has been demanded in connection with improvement of multi-coloring and data density required for light emitting devices and optoelectronic devices.

Gallium nitride (GaN) is a direct bandgap semiconductor, and its band gap is relatively large at about 3.45 eV, so it is widely used to develop blue and ultraviolet light emitting devices. However, since the conventional GaN light emitting device based on a thin film has a size of more than a micrometer, it is limited to be applied to a light emitting device which becomes finer and smaller.

Particularly, in the case of a thin-film device, a stress is generated due to a difference in lattice constant between the substrate and the GaN film during fabrication, and defects such as dislocation occur to mitigate the stress, have.

Nanowires are collectively referred to as nanostructures with a diameter of several hundreds of nanometers or less and a length of several micrometers or more. These nanowires remain standing without contact with the substrate and have a large surface area, so they can be used as a basic unit for constructing various devices. Particularly, the GaN nanowire can be used as a material of a new next-generation nano light emitting device which overcomes the disadvantages of the conventional thin film light emitting device.

However, when the GaN nanowires are grown while directly supplying a precursor of gallium and a precursor of nitrogen on the Si substrate, the formation density of the nanowires is low and the growth length is short.

In manufacturing the photoconductive device, when only such nanowires are fabricated to be used as a channel, a relatively large amount of photocurrent can be flown to assure the responsivity of the device, but the relatively low photoconductivity there is a problem that it is difficult to expect an excellent operation speed due to photoconductivity.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a nanowire having a higher density and a longer growth length by using a graphene layer in forming a nanowire on a Si substrate, It is an object of the present invention to provide a photovoltaic device capable of not only having more excellent photoconductivity but also allowing a larger amount of photocurrent to flow.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-mentioned problems, and other matters not mentioned may 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 photovoltaic device including: a substrate; A first graphene layer formed on the substrate; A plurality of light emitting structures grown on the graphene layer; A second graphene layer formed on the light emitting structure; A first metal electrode in contact with the first graphene layer; And a second metal electrode in contact with the second graphene layer; .

The light emitting structure includes nanowires grown on the substrate; And a multi quantum well structure layer grown in the circumferential direction of the nanowire; . ≪ / RTI >

The light emitting structure may further include quantum dots formed in the multi quantum well structure layer.

The light emitting structure may further include a shell layer formed on the multiple quantum well structure layer.

The multiple quantum well structure layer may include an alternately formed barrier layer and a well layer.

The barrier layer may be made of GaN.

The well layer may be made of InGaN.

The quantum dot may be made of InGaN.

The nanowire may be made of an n-type semiconductor, and the well layer may be made of a p-type semiconductor.

According to another aspect of the present invention, there is provided a method of manufacturing a photovoltaic device including: (a) forming a first graphene layer on a substrate; (b) growing a plurality of light emitting structures on the first graphene layer; (C) forming a second graphene layer on the light emitting structure; And (d) forming a first metal electrode in contact with the first graphene layer and a second metal electrode in contact with the second graphene layer; .

The step (a) may include: (a1) synthesizing a first graphene layer using a catalyst layer; (a2) forming a PMMA layer on the first graphene layer; (a3) removing the catalyst layer; And (a4) transferring the remaining graphene layer from the catalyst layer to the substrate; . ≪ / RTI >

The step (b) includes the steps of: (b1) growing a nanowire on the substrate; And (b2) growing a multiple quantum well structure layer in the circumferential direction of the nanowire; . ≪ / RTI >

The step (b) may further include forming quantum dots in the multi quantum well structure layer in the course of growing the multiple quantum well structure layer.

The step (b) may further include forming a shell layer on the multiple quantum well structure layer.

The step (b2) may correspond to a step of alternately forming the barrier layer and the well layer.

The step (c) includes the steps of: (c1) synthesizing a second graphene layer using a catalyst layer; (c2) forming a PMMA layer on the second graphene layer; (c3) removing the catalyst layer; And (c4) transferring the second graphene layer remaining after the catalyst layer is removed to the upper portion of the light emitting structure; . ≪ / RTI >

According to an aspect of the present invention, it is possible not only to obtain nanowires with higher density and longer length, but also to use graphene as a channel with such nanowires, so that excellent operation speed and photoconductivity A photoconductive element having photoconductivity can be obtained.

According to another aspect of the present invention, the emission area of a light emitting device such as an LED or a LD in the form of a nanowire is increased, and the internal quantum efficiency and the external quantum efficiency are increased, thereby improving the luminous efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
1 is a view showing a step of forming a first graphene layer.
2 is a view showing a step of forming a PMMA layer on the first graphene layer.
3 is a view showing a step of removing the catalyst layer from the first graphene layer.
4 is a view showing a step of transferring the first graphene layer onto a substrate.
5 is a view showing a step of removing the PMMA layer from the transferred graphene layer.
6 is a view showing a step of growing nanowires on a graphene layer.
Fig. 7 is a diagram showing the growth direction of nanowires through a lattice structure of GaN crystal.
8 is a view showing a step of forming an insulating layer formed between the graphene layer and the nanowire.
9 is a view showing a step of forming a light emitting structure by forming a quantum well structure layer with growth of a nanowire.
10 is a cross-sectional view showing the quantum well structure layer shown.
Fig. 11 is a diagram showing the growth direction of the quantum well structure layer shown in Fig. 10 through the lattice structure of the GaN crystal.
12 is a view showing a step of growing a shell layer on a quantum well structure layer to complete a light emitting structure.
13 is a view showing a step of forming a packed particle aggregate between the light emitting structures.
14 is a view showing a step of forming a second graphene layer on the upper portion of the light emitting structure.
15 is a view showing a photovoltaic device completed by forming a first metal electrode and a second metal electrode which are in contact with the first graphene layer and the second graphene layer, respectively.
16 is a photomicrograph showing a case where nanowires are directly grown on a substrate without using a graphene layer.
17 and 18 are photomicrographs showing the case where nanowires are grown using the first graphene layer according to the present invention.
19 is a photomicrograph of a first graphene layer and the nanowires grown thereon.
20 and 21 are Raman spectra obtained at points B and C shown in FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The overall configuration of the photoconductive device according to an embodiment of the present invention will be described with reference to FIG.

15 is a view showing a photovoltaic device completed by forming a first metal electrode and a second metal electrode which are in contact with the first graphene layer and the second graphene layer, respectively.

15, a photovoltaic device according to an embodiment of the present invention includes a substrate 10, a first graphene layer 20, a light emitting structure 30, an insulating layer 40, a packed particle aggregate 50 , A second graphene layer (60), a first metal electrode (70), and a second metal electrode (80).

As the substrate 10, for example, a (111) oriented Si substrate may be used and at least one cleaning process may be used.

The first graphene layer 20 enhances the growth density of the nanowires 31 (see FIGS. 10 and 12) constituting the light emitting structure 30 and allows the growth of the nanowires 31 (see FIGS. 10 and 12) Is a component formed on the substrate 10 so as to ensure a better photoconductivity.

When a heat treatment is performed in the process of forming the first graphene layer 20 on the substrate 10, a natural oxide film (not shown) is formed between the first graphene layer 20 and the substrate 10 As shown in FIG.

The light emitting structure 30 includes a multilayer quantum well structure layer 32 grown / formed in the circumferential direction of the nanowire 31 and the nanowire 31 grown on the first graphene layer 20, ). ≪ / RTI > The specific structure of the light emitting structure 30 will be described later in detail.

The insulating layer 40 is formed between the substrate 10 and the nanowire 31 (see Figs. 10 and 12) to form a shell layer 34 (see Fig. 12) constituting the light emitting structure 30, And function as an insulator between the fins 20.

In addition to the function of the insulator, the insulating layer 40 may also function to improve light emission efficiency by reflecting light that is emitted through the light emitting structure 30 and directed toward the substrate.

Meanwhile, the insulating layer 40 may be made of Al ₂ O ₃ nanoparticles in consideration of this function.

The packed particle aggregate 50 is filled between the plurality of the light emitting structures 30 and the particles constituting the packed particle aggregate 50 have a surface plasmon effect outside the light emitting structure 30 The efficiency of light emission can be further increased. As the particles constituting the packed particle aggregate (50), for example, Ag-SiO ₂ can be applied.

The second graphene layer 60 is formed on the upper side of the growth direction of the light emitting structure 30 so that the photoconductive device can secure a better photoconductivity in the same manner as the first graphene layer 20 It is a functional component.

The metal electrodes 70 and 80 are formed to be in contact with the graphene layers 70 and 80 in order to utilize the graphene layers 20 and 60 as photoconductive cyanets. (Ni), aluminum (Al), an alloy of gold and nickel, and an alloy of gold and aluminum may be used as the material of the metal electrodes 70 and 80.

Hereinafter, with reference to FIGS. 1 to 14, a specific manufacturing method of the photoconductive device according to an embodiment of the present invention having the above-described structure will be described.

First, the process of forming the first graphene layer 20 on the substrate 10 will be described with reference to FIGS. 1 to 5. FIG.

FIG. 1 is a view showing a step of forming a first graphene layer, and FIG. 2 is a view showing a step of forming a PMMA layer on a first graphene layer. Fig. 3 is a view showing a step of removing the catalyst layer from the first graphene layer, Fig. 4 is a view showing a step of transferring the first graphene layer onto a substrate, Fig. 5 is a cross- And removing the PMMA layer from the first graphene layer.

Referring to FIG. 1, the first graphene layer 20 may be synthesized by chemical vapor deposition (CVD) using a catalyst layer F made of nickel, copper, or platinum.

That is, the first graphene layer 20 is formed by reacting a metal foil having a thickness of several nanometers to several tens of nanometers at a high temperature with a mixed gas of methane and hydrogen, so that an appropriate amount of carbon is dissolved in the catalyst layer F And then allowing it to adsorb and then cooling it to room temperature.

When the catalyst layer F made of the metal foil is reacted with the mixed gas containing methane and hydrogen at a high temperature and cooled to room temperature, the carbon atoms contained in the catalyst layer F crystallize on the surface, Thereby forming a crystal structure.

Next, referring to Figs. 2 to 5, the catalyst layer F is removed from the laminate composed of the catalyst layer F and the first graphene layer 20, and the first grease layer F, from which the catalyst layer F has been removed, The process of transferring the pinned layer 20 onto the substrate will be described.

Referring to FIGS. 2 and 3, the catalyst layer F can be removed by the PMMA method.

 That is, in order to remove the catalyst layer F from the laminate obtained by growing the first graphene layer 20 on the catalyst layer F, a PMMA layer (polymethyl) is first formed on the first graphene layer 20 methacrylate layer (P), and then the catalyst layer (F) is removed by etching to obtain a laminate to be transferred onto the substrate (10).

Next, referring to FIGS. 4 and 5, a laminate composed of a laminate obtained by removing the catalyst layer F, that is, a first graphene layer 20 and a PMMA layer P formed on the surface thereof, The PMMA layer P is removed by dissolution or the like to obtain a laminate having a form in which the first graphene layer 20 is laminated on the substrate 10. [

Meanwhile, in the process of transferring the first graphene layer 20 onto the substrate 10, an oxide film (not shown) may be formed on the surface of the substrate 10 by the heat treatment. If a Si substrate, for example, is used as the substrate 10, the oxide film may be made of SiO ₂ .

In the present invention, the processing conditions applied to form the first graphene layer 20 on the catalyst layer (F) are as follows.

First, a foil made of copper (applicable to various metals such as nickel and platinum) having a thickness of several nanometers to several tens of nanometers is inserted in the center of a horizontal electric furnace of a CVD system and mixed with methane and hydrogen at a high temperature of about 800 to 1000 ° C Gas so that an appropriate amount of carbon is either dissolved or adsorbed in the catalyst bed. The amount of hydrogen gas was about 2 ~ 5 sccm, the amount of methane gas was about 30 ~ 50 sccm, and the growth pressure was about 300 ~ 600 mTorr. After cooling to room temperature at a rate of about 100 to 250 ° C / min, the carbon atoms contained in the catalyst layer crystallized on the surface to form a graphene structure.

In addition, in an embodiment of the present invention, graphene is grown on the metal foil, the catalyst layer is removed using the PMMA method, and then the first graphene layer 20 is transferred to the substrate 10, (10) and the first graphene layer (20). However, the technical idea of the present invention is not limited thereto.

That is, the laminate composed of the substrate 10 and the first graphene layer 20 can be obtained by introducing the substrate 10 in which the catalyst layer F is deposited to a thickness of several nm to several tens nm into the CVD system, 1 < / RTI > graphene layer 20 is grown.

Next, the process of growing the nanowires 31 on the first graphene layer 20 will be described with reference to FIGS. 6 and 7. FIG.

Fig. 6 is a view showing a process of growing nanowires on a graphene layer, and Fig. 7 is a diagram showing a growth direction of nanowires through a lattice structure of a GaN crystal.

Referring to FIGS. 6 and 7, the nanowire 31 is formed of a first conductive semiconductor, and a plurality of the nanowires 31 may be provided on the first graphene layer 20. In addition, the nanowires 31 may be grown in a direction substantially perpendicular to the surface of the first graphene layer 20, that is, in the c-plane direction (see FIG. 7).

Meanwhile, in describing the present invention, the first conductivity type semiconductor has properties of an n-type conductivity type semiconductor, and in the case of a second conductivity type semiconductor which will be described later, As an example. Also, in the present invention, the nanowire 31 is formed of n-type GaN as an example.

The nanowire 31 may be grown by, for example, MOCVD (Metal Organic Chemical Vapor Deposition), wherein the nanowire 31 is comprised of a substrate 10 and a first graphene layer 20 The stacked body may be loaded into the MOCVD reactor to perform heat treatment together with the supply of the hydrogen gas, and then the precursor gas of gallium and the precursor gas of nitrogen may be supplied.

In one embodiment of the present invention, the process conditions applied to grow the nanowire 31 are specifically as follows:

The substrate 10 on which the first graphene layer 20 is formed is charged into the MOCVD reactor and the substrate 10 is stabilized at a high temperature for a predetermined period of time. Deg.] C for 30 seconds to 5 minutes. Trimethylgallium (TMG), which corresponds to a precursor of gallium (Ga), and ammonia gas, which is a precursor of nitrogen, are used as the fuel gas supplied to the inside of the reactor, and the substrate temperature, pressure and growth time are respectively 850 to 1000 ° C , 400 to 600 Torr, and 60 to 90 minutes, respectively. At this time, the amount of TMG was about 0.2 to 1.0 sccm, and the flow rate of ammonia gas was 1 to 3 slpm.

On the other hand, the nanowires 31 grown by the above-described process can be doped with n-type and / or p-type, if necessary, and SiH ₄ gas type) and / or Cp ₂ Mg gas (in the case of p-type).

According to such processes, the nanowires grown on the graphene layer show improved results in terms of growth density, length, etc. as compared to the nanowires grown directly on the substrate without the graphene layer. These results are well illustrated in Figs. 16-18.

FIG. 16 is a photomicrograph showing a case where nanowires are directly grown on a substrate without using a graphene layer. FIGS. 17 and 18 show the case where nanowires are grown using a first graphene layer according to the present invention Is a photomicrograph showing.

Referring to FIGS. 16-18, the nanowires 31 (FIGS. 17 and 18) grown using the graphene layer have a significantly higher density than the nanowires grown without the graphene layer (FIG. 16) And its growth length is also long enough.

19 to 21 that the graphene layer 20 is still present on the substrate 10 even after the nanowire 31 is grown using the first graphene layer 20 as described above .

19 is a micrograph of the first graphene layer and the nanowires grown thereon, and FIGS. 20 and 21 are Raman spectra obtained at points B and C shown in FIG. 19. FIG.

As can be seen from the Raman spectra shown in FIGS. 20 and 21, peaks for graphene (denoted by G) clearly appear at points other than the positions where the nanowires 31 are formed Thus, it can be confirmed that the nanowire 31 is directly grown on the first graphene layer 20.

On the other hand, when the nanowires are grown on the graphene, there is an advantage that defects due to metal impurities and scattering of electrons can be reduced as compared with the case of growing nanowires using metal catalysts. By improving the carrier mobility due to the pin, it is possible to exhibit excellent performance in application as a photoconductive element.

Next, the process of forming the insulating layer 40 will be described with reference to FIG.

8 is a view showing a step of forming an insulating layer formed between the graphene layer and the nanowire.

Referring to FIG. 8, the insulating layer 40 is formed by dispersing nanoparticles, and can be obtained, for example, by dispersing nanoparticles of Al ₂ O ₃ through spin coating.

That is, the insulating layer 40 may be formed by spin coating on the first graphene layer 20 in the void space between the nanowires 31, And functions as an electrical insulator between the shell layer 34 to be formed later and the first graphene layer 20.

The insulating layer 40 is formed by reflecting the light directed toward the substrate 10 from the light emitting structure 30 (FIG. 9) including the nanowires 31 as described above, The function of improving the luminous efficiency of the device can also be performed.

Next, with reference to Figs. 9 to 12, a process of forming the light emitting structure 30 including the nanowires 31 will be described in detail.

FIG. 9 is a view showing a step of forming a quantum well structure layer with the growth of nanowires to form a light emitting structure, and FIG. 10 is a sectional view showing a quantum well structure layer. 11 is a view showing the growth direction of the quantum well structure layer shown in FIG. 10 through the lattice structure of the GaN crystal, and FIG. 12 is a view showing a state in which the light emitting structure is completed by growing a shell layer on the quantum well structure layer Fig.

Referring to FIGS. 9 and 10, the light emitting structure 30 includes a multi quantum well layer 32 formed on the nanowire 31.

The process of forming the multiple quantum well structure layer 32 includes forming a barrier layer 32a and a well layer 32b on the nanowire 31 as a process of forming an active layer of the light emitting structure 30, Are alternately grown.

The barrier layer 32a may be made of, for example, GaN. The barrier layer 32a is formed by alternately supplying TMGa (trimethylgallium) corresponding to the source of Ga and NH ₃ corresponding to the source of N according to a pulse method, at a temperature of approximately 650 ° C to 780 ° C, Temperature growth method which is supplied under a pressure of 300 torr.

The well layer 32b may be made of, for example, InGaN. The well layer 32b is formed by alternately supplying TMIn (Trimethylindium) corresponding to a source of In, TMGa corresponding to a source of Ga, and NH ₃ as a source of N, and the well layer 32b has a temperature of approximately 600 캜 to 750 캜, Lt; RTI ID = 0.0 > of < / RTI >

The multi-quantum well structure layer 32 grows in the m-plane direction corresponding to the circumferential direction of the nanowire 31 (see FIG. 11) by growing under a high-speed carrier gas and low pressure condition, 31) surface to a substantially uniform thickness.

Next, referring to Fig. 12, a process of forming the quantum dot 33 and the shell layer 34 is shown.

The quantum dot 33 includes a step of forming a dot made of, for example, InGaN in the multiple quantum well structure layer 22 in the middle of the step of growing the multiple quantum well structure layer 32.

The quantum dots 33 may be formed by alternately supplying TMIn corresponding to the source of In, TMGa corresponding to the source of Ga, and NH ₃ corresponding to the source of N according to the pulse method, The supply of NH ₃ may be stopped while supplying TMIn and TMGa simultaneously, and the supply of TMIn and TMGa may be stopped while NH ₃ is supplied. Thus, by alternately supplying the source, it is possible to induce formation of a small droplet type quantum dot rather than a thin film form.

When the sources are alternately injected for forming the quantum dots 33, the injection time of each source is approximately 30 seconds to 120 seconds, the temperature condition is approximately 500 DEG C to 700 DEG C, the pressure condition is approximately 100 torr to 300 torr . The injection time of the source affects the size of the quantum dot 33.

In this way, when the process of forming the multiple quantum well structure layer 32 and the quantum dot 33 is alternately repeated, the quantum dot Q is formed in the multiple quantum well structure layer 32 grown in the circumferential direction of the nanowire, Its size and distribution increase in proportion to temperature and growth time. In addition, the size of the quantum dot 33 may be varied from 10 nm to 200 nm.

As described above, the quantum point Q formed in the multi-quantum well structure layer 32 can further increase the luminous efficiency of light by further increasing the coupling ratio between electrons and holes.

On the other hand, the light emitting structure 30 has a structure in which a multi quantum well structure layer 32 grown on the nanowire 31 and a quantum well structure 33 formed on the multi quantum well structure layer 32 Layer 34 as shown in FIG.

The shell layer 34 has a property of a second conductivity type semiconductor as opposed to the nanowire 31, and may be made of, for example, P-type GaN.

In this case, the shell layer 34 is uniformly distributed evenly over the surface of the multiple quantum well structure layer 32 by simultaneously injecting TMGa corresponding to the source of Ga and NH ₃ corresponding to the source of N, ), In which case the temperature may be set to approximately 600 ° C to 800 ° C and the pressure may be set to approximately 100 torr to 300 torr.

Next, with reference to Fig. 13, a process of forming the filled-particle aggregate 50 will be described.

13 is a view showing a step of forming a packed particle aggregate between the light emitting structures.

The present step may be performed by filling Ag-SiO ₂ nanoparticles between the plurality of light emitting structures 30 by spin coating, for example. In this case, the size of the nanoparticles constituting the packed particle aggregate 50 may range from approximately 20 to 30 nm.

The packed particle aggregate 50 filling the spaces between the plurality of the light emitting structures 30 can increase the efficiency of light emission through the surface plasmon effect outside the light emitting structure 30 You can give.

The Ag-SiO ₂ nanocomposite having a core-shell structure is prepared by a sol-gel method and has an advantage that the size and chemical composition of the metal particle can be easily controlled. It has very stable thermodynamic properties in the atmosphere.

In the case of such Ag-SiO ₂ , since the SiO ₂ shell has a thickness of about 2 to 10 nm and the Ag-SiO _{2 has} a diameter of about 20 to 30 nm uniformly and is uniformly dispersed by spin coating, And the Ag-SiO ₂ nanocomposite are used together to form a hybrid structure.

The effect of the surface plasmon according to the Ag-SiO ₂ constituting the packed particle aggregate 50 is approximately 80% or more, which is superior to the case of simply using a nano metal.

Next, the process of forming the second graphene layer 60 will be described with reference to FIG.

14 is a view showing a step of forming a second graphene layer on the upper portion of the light emitting structure.

Referring to FIG. 14, the present process is a process of forming a second graphene layer 60 on the light emitting structure 30 and the packed particle aggregate 50.

The second graphene layer 60 may be formed in the same manner as the first graphene layer 20 described above.

That is, the second graphene layer 60 may be formed as follows. First, a graphene crystal structure is formed by using a catalyst layer F made of a metal foil and the catalyst layer F is removed by a PMMA method to form a laminated body composed of the PMMA layer P and the second graphene layer 60 . Next, the obtained laminate is transferred onto the light emitting structure 30 and the packed particle aggregate 50, and the PMMA layer P is removed to remove the PMMA layer P on the upper side of the light emitting structure 30 and the packed particle stack 50 A second graphene layer 60 formed can be obtained.

Of course, the process of obtaining the graphene layer 60 is not limited thereto, and the other process applied to obtain the first graphene layer 20 may be applied to form the second graphene layer 60 You can get it.

Next, the process of forming the metal electrodes 70 and 80 will be described with reference to FIG.

15 is a view showing a photovoltaic device completed by forming a first metal electrode and a second metal electrode which are in contact with the first graphene layer and the second graphene layer, respectively.

Referring to FIG. 15, the metal electrodes 70 and 80 may be formed through a sputtering system.

That is, the first metal electrode 70 of the metal electrode is formed by depositing a metal material on the substrate 10 by using a sputtering system equipment so that the metal material contacts the side edge portion of the first graphene layer 20 And then subjected to a heat treatment process.

In addition, the second metal electrode 80 may be formed by depositing a metal material on the second graphene layer 60 using a sputtering system, and then subjecting the metal material to a heat treatment process.

The metal electrodes 70 and 80 may be made of metal such as gold (Au), nickel (Ni), aluminum (Al), an alloy of gold and nickel, or an alloy of gold and aluminum as described above.

By thus contacting the metal electrodes 70 and 80 with the graphene layers 20 and 60, the photoconductive element according to an embodiment of the present invention can utilize the graphene layer as a light conduction channel, Carrier mobility can be secured.

As described above, the photoconductive device according to an embodiment of the present invention can secure increased nanowire density and growth length by growing nanowires on the graphene layer, thereby allowing a large amount of photocurrent to flow .

In addition, the photorefractive element according to an embodiment of the present invention has a structure that can use the graphene layer as a photoconductive channel, thereby ensuring excellent carrier mobility due to the graphene layer, .

That is, according to the structure of the photoconductive device according to an embodiment of the present invention, the merits of the graphene and the nanowire work together to realize quick responsivity and excellent operation speed at the same time will be.

As a result, according to the present invention, it becomes possible to design a photoconductive element having a faster sensor speed and a wider bandwidth, thereby making it possible to produce an optoelectronic device having a very high efficiency , And various applications are possible.

In addition, the photoconductive device according to an embodiment of the present invention includes quantum dots formed in the multiple quantum well structure layer and a packed particle aggregate formed outside the light emitting structure, in addition to the advantages described above due to the graphene layer, It also has the advantage of maximizing efficiency.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

F: catalyst layer
P: PMMA layer
10: substrate
20: First graphene layer
30: light emitting structure
31: nanowire (first conductivity type semiconductor) 32: quantum well structure layer 32
32a: barrier layer 32b: well layer
33: Quantum dot
34: Shell layer (second conductivity type semiconductor)
40: Insulating layer
50: Filled particle aggregate
60: Second graphene layer
70: first metal electrode
80: second metal electrode

Claims (16)

Board;
A first graphene layer formed on the substrate;
A plurality of light emitting structures grown on the graphene layer;
A second graphene layer formed on the light emitting structure;
A first metal electrode in contact with the first graphene layer; And
A second metal electrode in contact with the second graphene layer;
≪ / RTI > The method according to claim 1,
The light-
Nanowires grown on the substrate; And
A multi quantum well structure layer grown in the circumferential direction of the nanowire;
Wherein the photoconductive device comprises a photoconductive element. 3. The method of claim 2,
The light-
And quantum dots formed in the multi quantum well structure layer. The method of claim 3,
The light-
And a shell layer formed on the multi-quantum well structure layer. 3. The method of claim 2,
Wherein the multi-quantum well structure layer comprises:
Wherein the barrier layer and the well layer are alternately formed. 6. The method of claim 5,
Wherein the barrier layer comprises:
GaN. ≪ / RTI > 6. The method of claim 5,
Wherein:
Gt; InGaN. ≪ / RTI > 6. The method of claim 5,
The quantum dots include,
Gt; InGaN. ≪ / RTI > 6. The method of claim 5,
Wherein the nanowire is made of an n-type semiconductor,
Wherein the well layer is made of a p-type semiconductor. (a) forming a first graphene layer on a substrate;
(b) growing a plurality of light emitting structures on the first graphene layer;
(C) forming a second graphene layer on the light emitting structure; And
(d) forming a first metal electrode in contact with the first graphene layer and a second metal electrode in contact with the second graphene layer;
Gt; a < / RTI > photoconductive element. 11. The method of claim 10,
The step (a)
(a1) synthesizing a first graphene layer using a catalyst layer;
(a2) forming a PMMA layer on the first graphene layer;
(a3) removing the catalyst layer; And
(a4) removing the catalyst layer and transferring the remaining graphene layer onto the substrate;
≪ / RTI > 11. The method of claim 10,
The step (b)
(b1) growing nanowires on the substrate; And
(b2) growing a multiple quantum well structure layer in the circumferential direction of the nanowire;
≪ / RTI > 13. The method of claim 12,
The step (b)
And forming quantum dots in the multi quantum well structure layer in the course of growing the multi quantum well structure layer. 13. The method of claim 12,
The step (b)
And forming a shell layer on the multi-quantum well structure layer. 13. The method of claim 12,
The step (b2)
Wherein the barrier layer and the well layer are alternately formed. 11. The method of claim 10,
The step (c)
(c1) synthesizing a second graphene layer using a catalyst layer;
(c2) forming a PMMA layer on the second graphene layer;
(c3) removing the catalyst layer; And
(c4) transferring the second graphene layer remaining after the catalyst layer is removed to the upper portion of the light emitting structure;
≪ / RTI >

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