WO2015046766A1 - Transparent electrode and method for manufacturing same - Google Patents

Abstract

According to the present invention, a transparent electrode is formed using a transparent resistance changing material, the resistance state of which changes from a high-resistance state to a low-resistance state according to an applied electric field; a forming process is performed by applying a voltage to the transparent electrode to change the resistance state of the transparent electrode to the low-resistance state such that the transparent electrode has conductivity; as a result, a transparent electrode can be formed which exhibits good Ohmic characteristics with a semiconductor layer formed on the lower portion or the upper portion of the transparent electrode, and which exhibits a high degree of transmission not only with respect to light in the visible light range, but also with respect to short-wavelength light in the UV range. Particularly, according to the present invention, nanoparticles etc. are included inside a transparent electrode, which is made of a resistance changing material, thereby concentrating the electric field, such that forming can be performed easily at a lower voltage; when the same forming voltage is applied, a thicker transparent electrode is formed, thereby enhancing strength of the transparent electrode and safety of the device. In addition, according to the present invention, a plurality of transparent electrode layers, which are made of resistance changing materials, are stacked to form a transparent electrode, thereby forming a transparent electrode having a large thickness and enhancing strength of the transparent electrode and safety of the device. Particularly, a part of the plurality of transparent electrode layers is formed using a material that is well suited to forming, thereby increasing the thickness of the transparent electrode and reducing the forming voltage. In addition, when a plurality of transparent electrode layers are stacked to form a transparent electrode according to the present invention, the plurality of transparent electrode layers are stacked such that the difference in refractive index with regard to an outer air layer decreases towards the upper portion, thereby preventing total reflection of light generated by the semiconductor layer and improving light extraction efficiency. In addition, according to the present invention, a transparent conductive layer is formed on the semiconductor layer in a pattern corresponding to an electrode pad pattern formed on the transparent electrode such that forming is made easy while minimizing degradation of light extraction efficiency, thereby forming a transparent electrode having a large thickness and accordingly enhancing strength of the transparent electrode and safety of the device.

Description

Transparent electrode and manufacturing method thereof

The present invention relates to a transparent electrode and a method of manufacturing the same, and more particularly to a transparent electrode having a high electrical conductivity while having a good electrical conductivity, including the ultraviolet region and a method of manufacturing the same.

Transparent electrodes are used in various fields such as LEDs, solar cells, medical UV sterilizers, fisheries, and the like, and their application fields and their demands are increasing. In particular, the transparent electrode is widely used in the LED field, the current transparent electrode technology applied to the LED can be applied to a portion (365nm ~ 400nm) of the visible region (400nm-800nm) and the entire ultraviolet region (10nm-400nm). Indium Tin Oxide (ITO) -based technology is the main focus.

Recently, the demand for UV LEDs that generate light in the ultraviolet region is increasing rapidly, but since the transparent electrode showing high conductivity and high transmittance in the ultraviolet region has not been developed until now, it is difficult to commercialize the ultraviolet LED.

For example, in the case of a UV LED having an ITO transparent electrode, which is currently used the most, light in the short wavelength ultraviolet region (10 nm to 320 nm) generated in the active layer is mostly absorbed by the ITO, and is transmitted through the ITO to be extracted to the outside. This is only about 1%.

1 shows the transmittance when the ITO transparent electrode is formed on the P-GaN semiconductor layer according to the prior art. As shown in FIG. 1, the transmittance shows 80% or more in the wavelength range of 350 nm or more, but the transmittance decreases rapidly in the ultraviolet range of short wavelength. In particular, the transmittance is 20% or less in the short wavelength region of 280 nm or less. It can be seen that decreases.

Another prior art to solve this problem is to form a metal electrode pad directly without forming a transparent electrode on a semiconductor layer, such as p-AlGaN, but the difference in work function between the metal and the semiconductor layer is too large Ohmic Contact is made Not only does it occur, but the current is concentrated in the metal electrode pad and is not supplied to the entire active layer, thereby causing a problem that the amount of light generated in the active layer is significantly reduced.

In order to solve this problem, various studies have been conducted, but a transparent electrode which shows high conductivity and high transmittance at the same time in all light regions including the ultraviolet region has not been developed. This is because the conductivity and permeability of materials have a trade-off relationship with each other. The material having a high transmittance in the ultraviolet region has a large band-gap, so it is very low in electrical conductivity to be used as an electrode and does not have ohmic contact with a semiconductor material. impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent electrode forming method exhibiting high transmittance and high conductivity not only in the visible light region but also in the short ultraviolet light region, and exhibiting good ohmic contact characteristics with the semiconductor layer, and a semiconductor device manufactured using the same. It is.

In the transparent electrode according to the preferred embodiment of the present invention for solving the above problems, a voltage (forming voltage) above a threshold voltage inherent to a material is applied to form a conductive filament therein, whereby the resistance state is in a high resistance state. A transparent electrode layer formed of a resistance change material changed to a low resistance state; And an electric field concentration layer formed in the transparent electrode layer to reduce the forming voltage.

In addition, the electric field concentrating layer of the transparent electrode according to the preferred embodiment of the present invention may be formed in the middle of the transparent electrode layer, and may be formed of any one of nanoparticles, nanowires, and conductive polymers.

In addition, the electric field concentration layer of the transparent electrode according to a preferred embodiment of the present invention is formed on the interface between the transparent electrode layer and the semiconductor layer, it may be formed of any one of nanoparticles, nanowires, and conductive polymers.

In addition, the electric field concentration layer of the transparent electrode according to a preferred embodiment of the present invention, may be formed in a pattern corresponding to the electrode pad pattern formed on the transparent electrode.

On the other hand, the transparent electrode according to another embodiment of the present invention for solving the above problems is a transparent electrode formed on the semiconductor layer, the transparent electrode is applied to a voltage (forming voltage) or higher than the threshold voltage inherent to the material inside The conductive filaments are formed in the resistive material, and the resistance state is formed of a resistance change material changed from a high resistance state to a low resistance state, and includes a plurality of transparent electrode layers having conductive filaments formed therein.

In addition, at least two layers of the plurality of transparent electrode layers of the transparent electrode according to the preferred embodiment of the present invention may be formed of a resistance change material having a different band gap.

In addition, the plurality of transparent electrode layers of the transparent electrode according to the preferred embodiment of the present invention may be arranged to reduce the difference in refractive index with the air toward the top.

On the other hand, the projection electrode according to another embodiment of the present invention for solving the above problems is a transparent electrode formed on the semiconductor layer, a voltage (forming voltage) or higher than the threshold voltage inherent to the material is applied to the conductive filament therein A transparent electrode layer formed of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state; And a transparent conductive layer formed between the transparent electrode layer and the semiconductor layer and having a smaller conductivity than the transparent electrode layer, having a smaller band gap.

In addition, the transparent electrode according to the preferred embodiment of the present invention may be formed so that a portion of the transparent conductive layer is exposed to the outside.

In addition, the transparent conductive layer between the transparent conductive layer and the semiconductor layer of the transparent electrode according to a preferred embodiment of the present invention may further include a transparent conductive layer formed of a resistance change material formed with a conductive filament.

On the other hand, the method for forming a transparent electrode according to a preferred embodiment of the present invention for solving the above problems, the conductive filament is formed therein when a voltage (forming voltage) higher than the threshold voltage inherent to the (a1) material is applied, Forming a lower transparent electrode layer using a resistance change material whose resistance state is changed from a high resistance state to a low resistance state; (a2) forming an electric field concentration layer on the lower transparent electrode layer; (b) forming an upper transparent electrode layer on the field concentrating layer by using a resistance change material; And (c) applying a forming voltage to the upper transparent electrode layer to form conductive filaments inside the transparent electrode layers.

On the other hand, the transparent electrode forming method according to another embodiment of the present invention for solving the above problems, (a2) forming an electric field concentration layer on the semiconductor layer; (b) When a voltage (forming voltage) higher than a threshold voltage inherent to the material is applied to the field concentrating layer, a conductive filament is formed therein, whereby a resistance change material whose resistance state is changed from a high resistance state to a low resistance state is formed. Forming a transparent electrode layer by using; And (c) applying a forming voltage to the transparent electrode layer to form a conductive filament inside the transparent electrode layer.

In addition, in the step (a2) of the method for forming a transparent electrode according to the preferred embodiment of the present invention, the electric field concentration layer may be formed using any one of nanoparticles, nanowires, and a conductive polymer.

On the other hand, the transparent electrode forming method according to another preferred embodiment of the present invention for solving the above problems, (a) by applying a voltage (forming voltage) above the threshold voltage inherent to the material to form a conductive filament therein, Forming a plurality of transparent electrode layers of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state; And (b) applying a forming voltage to the plurality of transparent electrode layers to form conductive filaments therein.

On the other hand, the transparent electrode forming method according to another preferred embodiment of the present invention for solving the above problems, (a) by applying a voltage (forming voltage) above the threshold voltage inherent to the material to form a conductive filament therein, Forming a transparent electrode layer of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state; (b) applying a forming voltage to the transparent electrode layer to form a conductive filament in the transparent electrode layer, thereby changing the resistance state to a low resistance state; And (c) repeatedly performing steps (a) and (b) one or more times sequentially to further form a transparent electrode layer having conductive filaments formed therein.

In addition, in the method of forming a transparent electrode according to the preferred embodiment of the present invention, at least two layers of the plurality of transparent electrode layers included in the transparent electrode may be formed of a resistance change material having a different band gap.

In addition, in the method of forming a transparent electrode according to the preferred embodiment of the present invention, the plurality of transparent electrode layers may be arranged to decrease the difference in refractive index with air toward the top.

On the other hand, the transparent electrode forming method according to another embodiment of the present invention for solving the above problems, (a) forming a transparent conductive layer having a higher conductivity because the band gap is smaller than the transparent electrode layer; (b) a conductive filament is formed therein by applying a voltage (forming voltage) higher than a threshold voltage inherent to the material on the transparent conductive layer, whereby the resistance state is transparent to a resistance change material that is changed from a high resistance state to a low resistance state. Forming an electrode layer; And (d) applying a voltage between the transparent conductive layer and the transparent electrode layer to form a conductive filament inside the transparent electrode layer.

In addition, in the transparent electrode forming method according to a preferred embodiment of the present invention, the step (b), the transparent electrode layer is formed so that a portion of the transparent conductive layer is exposed to the outside, the step (d), the external A conductive filament may be formed inside the transparent electrode layer by applying a voltage between a portion of the transparent conductive layer and the transparent electrode layer.

In addition, in the transparent electrode forming method according to a preferred embodiment of the present invention, in the step (a), the transparent conductive layer may be formed on the transparent electrode layer formed of a resistance change material formed therein.

According to the present invention, a transparent electrode is formed of a resistance change material made of a transparent material whose resistance state is changed from a high resistance state to a low resistance state by an applied electric field, and a voltage is applied to the transparent electrode to reduce the resistance state of the transparent electrode. The transparent electrode is made conductive by performing a forming process to change the shape of the transparent electrode, thereby exhibiting good ohmic characteristics with a semiconductor layer formed under or above the transparent electrode, It is possible to form a transparent electrode exhibiting high transmittance.

In particular, the present invention can be easily formed at a lower voltage by concentrating an electric field by including nanoparticles in the transparent electrode formed of a resistance change material, thicker transparent electrode when the same forming voltage is applied It can form to enhance the strength of the transparent electrode and the safety of the device.

In addition, the present invention can form a transparent electrode by stacking a plurality of transparent electrode layer formed of a resistance change material to form a transparent electrode, thereby enhancing the strength of the transparent electrode and the safety of the device. In particular, by forming a portion of the plurality of transparent electrode layers with a material that is well formed, it is possible to reduce the forming voltage while increasing the thickness of the transparent electrode.

In addition, in the present invention, when the plurality of transparent electrode layers are stacked to form a transparent electrode, by stacking the plurality of transparent electrode layers such that a difference in refractive index with the external air layer decreases toward the top, the light generated in the semiconductor layer is prevented from total reflection. The light extraction efficiency can be improved.

In addition, the present invention by forming a transparent conductive layer in a pattern corresponding to the electrode pad pattern formed on the transparent electrode on the semiconductor layer, to facilitate the forming while minimizing the reduction in light extraction efficiency, to form a thick thickness of the transparent electrode Therefore, the strength of the transparent electrode and the safety of the device can be enhanced.

1 is a diagram showing the transmittance when the ITO transparent electrode is formed on the P-GaN semiconductor layer according to the prior art.

2 is a diagram illustrating a structure of a transparent electrode and a semiconductor device including the same according to the first embodiment of the present invention.

3A to 3C are diagrams for explaining the properties of the resistance change material.

4A to 4E illustrate the transmittance characteristics, ohmic characteristics before performing the forming process, contact resistance characteristics before performing the forming process, and performing the forming process according to the first embodiment in which a transparent electrode is formed using Ga ₂ O ₃ material on a p-GaN semiconductor layer. The following ohmic characteristics and contact resistance characteristics after performing the forming process are respectively shown.

5 illustrates a structure of a transparent electrode and a semiconductor device including the same according to the second embodiment of the present invention.

6 is a view showing the structure of a transparent electrode according to a third embodiment of the present invention.

7A and 7B illustrate a structure of a transparent electrode and a method of forming a transparent electrode according to a fourth preferred embodiment of the present invention.

8A and 8B illustrate a structure of a transparent electrode and a method of forming a transparent electrode according to a fifth exemplary embodiment of the present invention.

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

However, the present invention is applied to all the transparent electrodes (OLED transparent electrode, solar cell transparent electrode, LED transparent electrode, etc.) in contact with the semiconductor layer, the contents described below are for explaining the technical idea of the present invention It should be noted that this is only one embodiment.

2 is a diagram illustrating a structure of a transparent electrode and a semiconductor device including the same according to the first embodiment of the present invention. Referring to FIG. 2, a transparent electrode and a semiconductor device having the same according to the first exemplary embodiment of the present invention include a transparent electrode on the semiconductor layer 10 such that the semiconductor layer 10 and the transparent electrode 20 are in contact with each other. 20 is formed, a metal electrode pad 30 is formed on the transparent electrode 20, and a conductive filament (or metal filament) is formed inside the transparent electrode.

Here, it should be noted that the semiconductor layer 10 includes not only an inorganic semiconductor layer and an organic semiconductor layer, but also a concept including all materials through which charge can flow. In addition, it should be noted that all of the "semiconductor layers" mentioned below are used in the same sense. The inorganic semiconductor layer includes a single element semiconductor made of a single element such as Si and Ge. In addition, the inorganic semiconductor layer is a compound such as a Nitride compound semiconductor layer (GaN, AlGaN, InN, InGaN, AlN, etc.) and an oxide compound compound semiconductor layer (GaO, ZnO, CoO, IrO2, Rh2O3, Al2O3, SnO, etc.). The concept includes a semiconductor layer.

The organic semiconductor layer is typically a concept including a material forming an electron (hole) injection layer and an electron (hole) transport layer of an organic light emitting diode (OLED).

On the other hand, in order to improve the conductivity of the semiconductor layer 10, the surface in contact with the transparent electrode 20 of the semiconductor layer 10 is preferably doped with a p type or n type.

Meanwhile, the transparent electrode of the present invention is formed of a transparent material (resistance change material) whose resistance state is changed by an applied electric field, and a conductive filament is formed therein by forming (forming process or electric break down). It is. Such a resistance change material is mainly used in the field of resistive RAM (ReRAM), and when a voltage higher than a threshold inherent to the material is applied to the material, electro-forming is performed, so that the resistance state of the material, which is an insulator at first, is a high resistance state. It is changed to a low resistance state at to show conductivity.

3A to 3C are diagrams illustrating the characteristics of such a resistance change material. Referring to FIG. 3A, when a voltage above a threshold is applied to a resistance change material that is an insulator, an electrode metal material is diffused into the thin film by an electrical forming process or a resistance structure as shown in FIG. 3A due to a defect structure in the thin film. Conductive filaments (or metallic filaments) are formed inside the change material. Thereafter, even when the voltage applied to the material is removed, the conductive filament 22 is maintained, and current flows through the conductive filament 22, so that the resistance state of the material is maintained in the low resistance state.

Referring to FIG. 3B, it can be seen that the resistance change material (AlN) shows an insulator characteristic before the forming process and then shows the I-V characteristic of the metal after the forming process. In addition, the conductive filament formed in the transparent electrode may be SET or RESET as shown in FIG. 3B using the JOULE-HEATING effect.

Figure 3c is a graph showing how stable the conductive filament can be formed after the formation, as shown by the red dotted line of the graph shows that the low resistance state can be stably maintained for 10 years after the formation of the conductive filament Can be.

In a preferred embodiment of the present invention, as the resistance change material, a transparent conductive oxide-based material (SiO2, Ga2O3, Al2O3, ZnO, ITO, etc.), a transparent conductive Nitride-based material (Si3N4, AlN, GaN, InN, etc.), Transparent conductive polymer-based materials (polyaniline (PANI), poly (ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS), etc.), and transparent conductive nanomaterials (CNT, CNT-oxide, Graphene, Graphene-oxide, etc.) were used. In addition to the above materials, any material that is transparent and exhibits the above-described resistance change characteristics may be used to form the transparent electrode of the present invention. However, it should be noted that the meaning of the materials having conductivity is that they have conductivity by a forming process.

4A to 4E illustrate the transmittance characteristics, ohmic characteristics before performing the forming process, contact resistance characteristics before performing the forming process, and forming process according to the first embodiment in which a transparent electrode is formed using Ga ₂ O ₃ material on a p-GaN semiconductor layer. The subsequent ohmic characteristics and the contact resistance characteristics after performing the forming process are shown, respectively.

In the example illustrated in FIGS. 4A to 4E, a transparent electrode thin film (thickness: 80 nm) was formed of Ga ₂ O ₃ material on a p-GaN semiconductor layer commonly used in LEDs.

Referring to the graph shown in FIG. 4A, it can be seen that the Ga ₂ O ₃ transparent electrode of the illustrated example exhibits transmittance of 80% or more with respect to light in an ultraviolet region having a wavelength of 264 nm or more. This also can be seen that the transmittance is significantly improved compared to the conventional ITO-based transparent electrode showing a transmittance of 20% shown in FIG.

4B to 4E are measured by using ohmic characteristics (FIGS. 4B and 4D) and TLM (Transfer Length Method) patterns when the distance between the measuring electrodes is 2 μm, 4 μm, 6 μm, 8 μm, and 10 μm. Resistance characteristics (FIGS. 4C and 4E) are shown.

Referring to Figure 4b, based on the case where the distance between the measuring electrode 2㎛, the forming process is carried out previously and the transparent electrode, independent of the voltage applied is of 1.0 * 10 ^-11 A and out to find out the current flow, not at all It can be seen that it does not exhibit ohmic characteristics. In addition, referring to FIG. 4C, it can be seen that the ohmic contact resistance characteristic also shows no linearity at all.

On the other hand, referring to Figure 4d, after performing the forming process, when the voltage applied to the transparent electrode is 0V ~ 1.0V, based on the distance between the measuring electrode is 2㎛ 0 ~ 2.0 * 10 ^-2 to the transparent electrode As the current flows about A, 10 ⁹ times more current flows than before the forming process, and the current-voltage relationship also shows good ohmic characteristics that are proportional to each other. In addition, referring to Figure 4e, it can be seen that the ohmic contact resistance characteristics are significantly improved compared to before the forming process because the contact resistance characteristics also exhibit a linearity.

When Figures 4a to clean up the Ga ₂ O ₃ transparent electrode characteristics formed on the illustrated example p-GaN semiconductor layer in Fig. 4e, Ga ₂ O ₃ transparent electrode is at least 80% transmittance with respect to light of ultraviolet region having a wavelength of more than 264nm shows a result of measurement using the TLM pattern before performing the forming step exhibits a contact resistance of 51,680Ω㎝ ^-2, performed after the forming step is 2.64 * 10 ^-5 exhibits a contact resistance of Ω㎝ ^-2 superior conductivity It can be seen that not only is it improved, but also shows good ohmic characteristics.

The transparent electrode and the semiconductor device including the same according to the first embodiment of the present invention have been described so far.

In the case of the first embodiment described above, the transparent electrode was formed of a single layer, and thus, the transparent electrode was formed of a very thin thin film. The reason is that the above-mentioned resistance change material for forming the transparent electrode has a large band gap and thus a very large resistance, and thus, when the thickness thereof becomes thick, it is difficult to form an appropriate amount of conductive filaments.

However, as in the first embodiment described above, when the transparent electrode is formed to have a very thin thickness, the strength of the transparent electrode itself may be weakened, and thus, the overall strength of the semiconductor device may be weakened.

Transparent electrodes according to the second to fifth embodiments of the present invention described below solve this problem.

5 illustrates a structure of a transparent electrode and a semiconductor device including the same according to the second embodiment of the present invention.

Referring to FIG. 5, referring to a structure of a transparent electrode 500 according to a second exemplary embodiment of the present invention, the transparent electrode 500 according to the second exemplary embodiment may be formed of a resistance change material on the semiconductor layer 10. The upper transparent electrode layer 511 and the lower transparent electrode layer 512, and the electric field concentrating layer 520 is formed in the transparent electrode layer (511, 512) to reduce the forming voltage.

The electric field concentrating layer 520 is composed of a plurality of nanoparticles, nanowires, conductive polymers, etc. (hereinafter referred to as "nanoparticles", etc.), and in the process of forming the transparent electrode layer 510 formed of a resistance change material, the electrode By concentrating the electric field applied by the probe 100 in nanoparticles, nanowires, conductive polymers, etc. without being scattered in various directions, the formation of the conductive filaments 22 is possible by applying a relatively small voltage. When a voltage is applied, the conductive filament 22 can be formed in the transparent electrode layer thicker than the case where the electric field concentration layer is not included. Therefore, the thickness of the transparent electrode 510 can be formed to be thicker, thereby further enhancing the strength of the transparent electrode 510 and the safety of the device. In this case, also in the case of nanowires, conductive polymers, and the like, it is preferable that the nanoparticles are configured in the form of particles having a small aspect ratio.

In addition, the current concentrating layer 520 is formed in a pattern corresponding to the electrode pad pattern (not shown) formed on the transparent electrode 500, it is preferably formed so as not to impair the transmittance of light.

Referring to FIG. 5 again, a plurality of conductive filaments 22 are formed in the transparent electrode layer 510, and each of the conductive filaments 22 forms nanoparticles 520 constituting the current concentrating layer 520. The current path is formed through the semiconductor layer 10.

In the second embodiment, since the conductive filament 22 is formed through the nanoparticles 520 of the current concentrating layer, it is easier to adjust the spacing of the nanoparticles 520 constituting the electric field concentrating layer 520. The spacing of the conductive filaments 22 can be adjusted, thus forming uniform conductive filaments 22.

Referring to the method of forming the transparent electrode according to the second preferred embodiment of the present invention, first, the lower transparent electrode layer 512 is formed on the semiconductor layer 10 by using a resistance change material, and the electric field concentration layer ( 520 is formed. The method of forming the electric field concentrating layer 520 can be variously applied. In the simplest method, a solution containing nanoparticles or the like is applied onto the lower transparent electrode layer, and the solution is evaporated. Besides After depositing a thin metal, a method of forming nanoparticles through heat treatment may be applied.

After the electric field concentrating layer 520 is formed, the upper transparent electrode layer 511 is formed on the electric field concentrating layer 520 with the same resistance material as the resistance change material used to form the lower transparent electrode layer 512. At this time, since the electric field concentrating layer 520 is disposed in an arbitrary region on the lower transparent electrode layer 512 with nanoparticles or the like, a part of the upper transparent electrode layer 511 is formed on the lower transparent electrode layer 512, and a part of the nanoparticles is formed. Since the lower transparent electrode layer 512 and the upper transparent electrode layer 511 are connected to one, so as to form the transparent electrode layer 510, and the nanoparticles 520 are included at the same height in the middle of the transparent electrode layer. Has a structure.

Finally, when the upper transparent electrode layer 511 is formed, the resistance change material used to contact the electrode probe 100 on the upper transparent electrode layer 511 and form the upper transparent electrode layer 511 and the lower transparent electrode layer 512. The conductive filament 22 is formed inside the transparent electrode layer 510 by applying a voltage higher than a threshold voltage inherent to the transparent electrode to complete the transparent electrode.

6 is a view showing the structure of a transparent electrode according to a third embodiment of the present invention. Referring to FIG. 6, in comparison with the second embodiment, the transparent electrode of the third embodiment is not formed in the middle of the transparent electrode layer, but is formed on the interface with the semiconductor layer 10. There is a difference.

Referring to FIG. 6, the electric field concentrating layer 620 of the third embodiment may be formed on the semiconductor layer 10 using nanoparticles made of the same material as the electric field concentrating layer 520 of the second embodiment. In this case, the nanoparticles 620 may be formed on the semiconductor layer 10 in the same manner as in the second embodiment, and may be formed to correspond to an electrode pad pattern (not shown) to be formed on the transparent electrode 600. It may be formed so as not to impair the transmittance of light.

In addition, a resistance change material is deposited on the electric field concentrating layer 620 to form a transparent electrode layer 610, and a conductive filament 22 is formed inside the transparent electrode layer 610 so that the resistance state of the transparent electrode layer 610 is increased. It is changed from the high resistance state to the low resistance state.

As shown in FIG. 6, the conductive filaments 22 formed in the transparent electrode 600 are connected to the semiconductor layer 10 through the nanoparticles 620 as in the second embodiment, and thus, the nanoparticles and the like. Since the electric field is concentrated at 620, the conductive filament 22 can be formed with a relatively low forming voltage, and a thicker thickness when the same voltage is applied as compared with the case where the electric field concentrating layer 620 is not formed. The transparent electrode 600 may be formed to improve the strength of the transparent electrode 600 and the safety of the device.

In addition, since the conductive filaments 22 are formed through the nanoparticles 620 and the like of the electric field concentrating layer, by adjusting the intervals of the nanoparticles 620 constituting the electric field concentrating layer, the intervals of the conductive filaments 22 are more easily achieved. Can be adjusted, and thus uniform conductive filaments 22 can be formed.

Referring to the method of forming the transparent electrode according to the third preferred embodiment of the present invention, first, the electric field concentrating layer 620 is formed on the semiconductor layer 10. Since the method of forming the electric field concentrating layer 620 is the same as in the above-described second embodiment, a detailed description thereof will be omitted.

Thereafter, the resistance change material is deposited on the semiconductor layer 10 and the electric field concentrating layer 620 to form the transparent electrode layer 610, thereby including the transparent electrode 600 including the transparent electrode layer 610 and the electric field concentrating layer 620. ).

Finally, the conductive filament 22 is formed inside the transparent electrode layer 610 by contacting the electrode probe 100 on the transparent electrode layer 610 and applying a voltage higher than a threshold voltage inherent to the transparent electrode layer 610. Complete 600.

7A and 7B illustrate a structure of a transparent electrode and a method of forming a transparent electrode according to a fourth preferred embodiment of the present invention.

The transparent electrode according to the fourth embodiment of the present invention is characterized by including a plurality of transparent electrode layers, the thickness of each transparent electrode layer may be the same, or may be different from each other. In addition, the material of each transparent electrode layer may also be a resistance change material of the same material having the same band gap, or may be a resistance change material having a different band gap.

In particular, when the semiconductor layer 10 is a device that emits light, such as an LED or an OLED, the plurality of transparent electrode layers constituting the transparent electrode are made of a material having different refractive indices, and the more transparent electrode layers positioned above When formed using a material having a small difference in refractive index with air, light generated in the semiconductor layer 10 may be totally reflected by the transparent electrode and prevent the light from flowing back into the semiconductor layer 10.

First, referring to FIG. 7A, the transparent electrode 700 according to the fourth embodiment illustrated in FIG. 7A includes a plurality of transparent electrode layers, and at least two layers of the transparent electrode layers may have different band gaps. It was formed of a material having.

In the example illustrated in FIG. 7A, the transparent electrode 710 is formed by sequentially forming a first transparent electrode layer 711 and a second transparent electrode layer 712. The first transparent electrode layer 711 is formed of a resistance change material in which the conductive filament 22 is easily formed by foaming because the band gap is smaller than that of the second transparent electrode layer 712, and the second transparent electrode layer 712 is formed. Silver was formed using a resistance change material having a larger band gap than that of the first transparent electrode layer and having better transmittance to light in all regions including the ultraviolet region.

In addition, as shown in the example of FIG. 7A, the transparent electrode has a structure in which the third transparent electrode layer 713, the fourth transparent electrode layer 714, and the third transparent electrode layer 713 are sequentially formed. May be In this case, the fourth transparent electrode layer 714 is formed of a resistance change material in which the conductive filament 22 is easily formed by foaming because the band gap is smaller than that of the third transparent electrode layer 713. 713 may be formed using a resistance change material having a greater band gap than that of the fourth transparent electrode layer 714 and having better transmittance with respect to light in all regions including the ultraviolet region.

That is, the third transparent electrode layer 713 and the fourth transparent electrode layer 714 illustrated in FIG. 7A (b) may include the second transparent electrode layer 712 and the first transparent electrode layer 711 illustrated in FIG. 7A (a). And each of the same material).

As described above, in the plurality of transparent electrode layers illustrated in FIG. 7A, the total reflection effect may be reduced as the transparent electrode layer having a small difference in refractive index from air is disposed on the upper portion.

Referring to the method of forming the transparent electrode illustrated in FIG. 7A, first, a resistance change material is deposited on the semiconductor layer 10 to form the first transparent electrode layer 711. In this case, the first transparent electrode layer 711 may be formed of a resistance change material in which the conductive filament 22 is easily formed by foaming because the band gap is smaller than that of the second transparent electrode layer 712. As shown.

Thereafter, a second transparent electrode layer 712 is deposited on the first transparent electrode layer 711. The second transparent electrode layer 712 may be formed using a resistance change material having a larger band gap than the first transparent electrode layer 711 and having a better transmittance to light in all regions including the ultraviolet region.

When the transparent electrode 710 including the plurality of transparent electrode layers 711 and 712 is completed, the electrode probe 100 is contacted with the second transparent electrode layer 712 positioned at the top to apply a voltage to the second transparent electrode 710. By forming the conductive filaments 22 by forming the electrode layer 712 and the first transparent electrode layer 711, the resistance state of the transparent electrode 710 is changed from a high resistance state to a low resistance state.

The method of forming the transparent electrode illustrated in FIG. 7A (b) may be similar to the method of forming the transparent electrode illustrated in FIG. 7A (a). The third transparent electrode layer 713 and the fourth transparent electrode layer 4 may be formed on the semiconductor layer 10. After the transparent electrode layer 714 and the fifth transparent electrode layer 715 are sequentially formed, the transparent electrode layers 713, 714, and 715 are formed by contacting the electrode probe 100 with the fifth transparent electrode layer 715 and applying a voltage thereto. The transparent electrode is completed by forming the conductive filament 22. In this case, the fourth transparent electrode layer 714 may be formed of a resistance change material in which the conductive filament 22 is easily formed by forming because the band gap is smaller than that of the other transparent electrode layers 713 and 715.

In the case of the fourth embodiment shown in FIG. 7A, a transparent electrode layer formed of a resistance change material which is relatively easy to form is included in the transparent electrode, so that the transparent electrode can be formed to a thicker thickness even when the same voltage is applied. Therefore, the physical strength of the transparent electrode and the safety of the device can be enhanced.

7B is the same as that of FIG. 7A in that a plurality of transparent electrode layers are stacked to form a transparent electrode. However, in the case of FIG. 7B, there is a difference in that foaming is performed for each transparent electrode layer constituting the transparent electrode.

Specifically, in the plurality of transparent electrode layers illustrated in (a) of FIG. 7B, the first transparent electrode layer 721, the second transparent electrode layer 722, and the third transparent electrode layer 723 having different band gaps are sequentially formed. The semiconductor layer 10 is stacked and formed.

In the process of forming the transparent electrode layer, after forming the first transparent electrode layer 721 on the semiconductor layer 10, the electrode probe 100 is in contact with the first transparent electrode layer 721 to apply a voltage to the first transparent electrode layer 721. ) Is first formed to form the conductive filaments 22 therein.

Thereafter, the second transparent electrode layer 722 is formed on the first transparent electrode layer 721, and the second transparent electrode layer 722 is formed in the same manner as the first transparent electrode layer 721 to form the conductive filament 22 therein. To form. Similarly, the third transparent electrode layer 723 is formed on the second transparent electrode layer 722 and the transparent electrode 720 is completed by forming.

In the example of FIG. 7B, when the difference in refractive index with the outside air decreases from the first transparent electrode layer 721 to the third transparent electrode layer 723, the light introduced from the semiconductor layer 10 is totally reflected. As described above, there is an effect of blocking the flow into the semiconductor layer 10 again.

On the other hand, the fourth embodiment shown in (b) of FIG. 7B except that the plurality of transparent electrode layers are all formed of a resistance change material of the same material, the transparent electrode and the structure shown in (a) of FIG. 7B And since the formation method is the same, a detailed description is omitted.

In the case of the transparent electrode according to the fourth embodiment described above with reference to FIG. 7B, the transparent electrode is formed to include a plurality of transparent electrode layers 731 each formed with a conductive filament 22, thereby forming the transparent electrode in a desired thickness. The thickness of the transparent electrode and the safety of the device can be enhanced.

8A and 8B illustrate a structure of a transparent electrode and a method of forming a transparent electrode according to a fifth exemplary embodiment of the present invention.

The transparent electrode 810 according to the fifth preferred embodiment of the present invention illustrated in FIG. 8A includes a transparent conductive layer 811 formed on the semiconductor layer 10 and a transparent electrode layer formed of a resistance change material on the transparent conductive layer 811. 812).

The transparent conductive layer 811 is formed of a material having a higher conductivity due to a smaller band gap than the transparent electrode layer 812. The transparent conductive layer 811 may be formed of materials (eg, ITO, ZnO, etc.) used as a transparent electrode in the conventional transparent electrode technology. Can be.

In addition, the transparent electrode layer 812 is formed of the above-described resistance change material and conductive filaments 22 are formed therein, and the resistance state thereof is changed to a low resistance state.

In addition, some regions of the transparent conductive layer 811 are formed to be exposed to the outside. The partial region 813 of the transparent conductive layer 811 exposed to the outside is in contact with the electrode probe 100 and used in the forming process. In the method of exposing a portion of the transparent conductive layer 811 to the outside, the transparent electrode layer 812 is formed on the entire surface of the transparent conductive layer 811, and a portion of the transparent electrode layer 812 is etched to etch the transparent conductive layer 811. By using a method of exposing a portion of the region 813 to the outside, or by depositing a resistive change material only in the region except the exposed region of the transparent conductive layer 811 to expose a portion of the transparent conductive layer to the outside.

Referring to FIG. 8A, a method of forming a transparent electrode according to a fifth embodiment is described. First, a transparent conductive layer having a higher conductivity due to a smaller band gap than a transparent electrode layer 812 described later as a very thin thin film on the semiconductor layer 10. 811 is formed by evaporation. At this time, the transparent conductive layer 811 may be formed of materials (eg, ITO, ZnO, etc.) used as a transparent electrode in the prior art. However, when the transparent conductive layer 811 is formed too thick, since the light in the ultraviolet region flowing from the semiconductor layer 10 does not pass through the transparent conductive layer 811, it is preferable to form the thinnest layer possible. In a preferred embodiment of the present invention, the transparent conductive layer 811 is formed to a thickness of about 3 nm to 5 nm.

In addition, in a preferred embodiment of the present invention, by forming a transparent conductive layer 811 in a pattern corresponding to the electrode pad pattern (not shown) formed on the transparent electrode using a photo process, to the transparent conductive layer 811 As a result, the light extraction efficiency may be reduced. That is, since the electrode pad pattern (not shown) formed on the transparent electrode layer 812 does not allow light to pass through, forming a transparent conductive layer in a pattern corresponding thereto may reduce the light extraction efficiency.

After the transparent conductive layer 811 is formed, a transparent electrode layer 812 is formed thereon using a resistance change material. At this time, the transparent electrode layer 812 is formed so that a portion of the transparent conductive layer 811 is exposed to the outside, and the method thereof has been described above and thus will be omitted.

Subsequently, a portion of the transparent conductive layer 811 exposed to the outside is in contact with the electrode probe 100 in the forming process of the transparent electrode layer 812 and used in the forming process. That is, one of the pair of electrode probes 100 for performing the forming is in contact with the transparent electrode layer 812, and the other is in direct contact with the exposed area of the transparent conductive layer 811 to apply a voltage. When a voltage is applied in this manner, as shown in FIG. 8A, a current path is formed through the transparent electrode layer 812 and the transparent conductive layer 811 formed thereunder to form a current path through only the transparent electrode layer 812. The forming process may be performed at a lower voltage than that of forming.

In the absence of the transparent conductive layer 811, a current path must be formed only through a high resistance resistance change material, so that forming is difficult, and thus a larger forming voltage is required. Therefore, according to the fifth embodiment of the present invention, the conductive filament 22 can be formed on the thicker transparent electrode at the same forming voltage as compared with the case where the transparent conductive layer 811 is not provided, thereby providing the strength and The safety of the device can be enhanced.

8B is a diagram showing a modification of the fifth preferred embodiment of the present invention. Referring to FIG. 8B, the transparent electrode 820 according to the modification of the fifth embodiment may include a lower transparent electrode layer 821 formed on the semiconductor layer 10, a transparent conductive layer 822 formed on the lower transparent electrode layer 821, An upper transparent electrode layer 823 formed on the transparent conductive layer 822.

8B is a transparent conductive layer 822 and an upper transparent electrode layer (except that the lower transparent electrode layer 821 is further formed under the transparent electrode of the fifth embodiment shown in FIG. 8A). 823 has the same configuration as the transparent conductive layer 811 and the transparent electrode layer 812 of FIG. 8A. Before forming the transparent conductive layer 822, the lower transparent electrode layer 821 is formed with a conductive filament 22 formed therein.

Referring to the method of forming the transparent electrode according to the modification illustrated in FIG. 8B, first, a resistive change material is deposited on the semiconductor layer 10 to form a lower transparent electrode layer 821, and contacting the electrode probe 100 thereon. Then, a forming voltage is applied to the lower transparent electrode layer 821 to form a conductive filament 22 therein. The process of forming the lower transparent electrode layer 821 is the same as that of the first embodiment described above.

Thereafter, a transparent conductive layer 822 is formed by depositing on the lower transparent electrode layer 821, and an upper transparent electrode layer 823 is formed to expose a portion of the transparent conductive layer 822 thereon. The transparent conductive layer 822 is preferably formed to correspond to the electrode pad pattern to be formed on the upper transparent electrode layer 823, and the method of generating the upper transparent electrode layer 823 is as described above with reference to FIG. 8A.

When the upper transparent electrode layer 823 is formed, as described above with reference to FIG. 8A, the forming electrode is applied by contacting the electrode probe 100 to the upper transparent electrode layer 823 and the transparent conductive layer 822, respectively. Conductive filaments 22 are formed on the transparent electrode layer 823.

In this manner, the forming of the transparent conductive layer 822 and the upper transparent electrode layer 823 capable of reducing the forming voltage on the lower transparent electrode layer 821, which is already formed, is performed to form the modified example of the fifth embodiment. The transparent electrode can be formed thicker than the transparent electrode shown in Fig. 3, and as a result, the strength of the transparent electrode and the safety of the device can be further enhanced.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

Claims (20)

1. A transparent electrode layer formed of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state by applying a voltage (forming voltage) above a threshold voltage unique to the material to form a conductive filament therein; And

   And an electric field concentrating layer formed in the transparent electrode layer to reduce the forming voltage.
2. The method of claim 1,

   The field concentrating layer is formed in the middle of the transparent electrode layer, characterized in that formed of any one of nanoparticles, nanowires, and conductive polymers.
3. The method of claim 1,

   The field concentrating layer is formed at an interface between the transparent electrode layer and the semiconductor layer, and is formed of any one of nanoparticles, nanowires, and a conductive polymer.
4. The method according to claim 2 or 3,

   The field concentrating layer is formed in a pattern corresponding to the electrode pad pattern formed on the transparent electrode.
5. A transparent electrode formed on a semiconductor layer, wherein the transparent electrode

   By applying a voltage (forming voltage) above a threshold voltage inherent to the material to form a conductive filament therein, the resistance state is formed of a resistance change material that is changed from a high resistance state to a low resistance state, and a conductive filament is formed therein. A transparent electrode comprising a plurality of transparent electrode layers.
6. The method of claim 5,

   At least two layers of the plurality of transparent electrode layers is formed of a resistance change material having a different band gap.
7. The method according to claim 5 or 6,

   The plurality of transparent electrode layers are disposed so that the difference in refractive index with the air decreases toward the top.
8. As a transparent electrode formed on a semiconductor layer,

   A transparent electrode layer formed of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state by applying a voltage (forming voltage) above a threshold voltage unique to the material to form a conductive filament therein; And

   And a transparent conductive layer formed between the transparent electrode layer and the semiconductor layer and having a smaller conductivity than the transparent electrode layer with a smaller band gap.
9. The method of claim 8,

   And a portion of the transparent conductive layer is exposed to the outside.
10. The method of claim 8,

    Between the transparent conductive layer and the semiconductor layer,

    The transparent electrode further comprises a transparent conductive layer formed of a resistance change material formed with a conductive filament.
11. As a method of forming a transparent electrode,

    (a1) When a voltage (forming voltage) above a specific threshold voltage is applied to the material, a conductive filament is formed therein, thereby forming a lower transparent electrode layer using a resistance change material whose resistance state is changed from a high resistance state to a low resistance state. Forming;

    (a2) forming an electric field concentration layer on the lower transparent electrode layer;

    (b) forming an upper transparent electrode layer on the field concentrating layer by using a resistance change material; And

    (c) forming a conductive filament inside the transparent electrode layers by applying a forming voltage to the upper transparent electrode layer.
12. As a method of forming a transparent electrode,

    (a2) forming an electric field concentration layer on the semiconductor layer;

    (b) When a voltage (forming voltage) higher than a threshold voltage inherent to the material is applied to the field concentrating layer, a conductive filament is formed therein, whereby a resistance change material whose resistance state is changed from a high resistance state to a low resistance state is formed. Forming a transparent electrode layer by using; And

    (c) forming a conductive filament in the transparent electrode layer by applying a forming voltage to the transparent electrode layer.
13. The method according to claim 11 or 12,

    In the step (a2), the electric field concentrating layer is formed using any one of nanoparticles, nanowires, and conductive polymers.
14. (a) a conductive filament is formed therein by applying a voltage (forming voltage) above a threshold voltage inherent to the material, thereby forming a plurality of transparent electrode layers of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state; Doing; And

    (b) forming a conductive filament therein by applying a forming voltage to the plurality of transparent electrode layers.
15. (a) forming a transparent electrode layer of a resistance change material whose resistance state is changed from a high resistance state to a low resistance state by applying a voltage (forming voltage) above a threshold voltage inherent to the material to form a conductive filament therein; ;

    (b) applying a forming voltage to the transparent electrode layer to form a conductive filament in the transparent electrode layer, thereby changing the resistance state to a low resistance state; And

    (c) repeatedly performing steps (a) and (b) at least once in order to further form a transparent electrode layer having conductive filaments formed therein.
16. The method according to claim 14 or 15,

    At least two layers of the plurality of transparent electrode layers included in the transparent electrode is formed of a resistance change material having a different band gap.
17. The method according to claim 14 or 15,

    And the plurality of transparent electrode layers are disposed such that a difference in refractive index with air decreases toward the upper portion.
18. (a) forming a transparent conductive layer having a higher conductivity with a smaller band gap than the transparent electrode layer;

    (b) a conductive filament is formed therein by applying a voltage (forming voltage) higher than a threshold voltage inherent to the material on the transparent conductive layer, whereby the resistance state is transparent to a resistance change material that is changed from a high resistance state to a low resistance state. Forming an electrode layer; And

    (d) applying a voltage between the transparent conductive layer and the transparent electrode layer to form a conductive filament inside the transparent electrode layer.
19. The method of claim 18,

    In the step (b), forming the transparent electrode layer so that a part of the transparent conductive layer is exposed to the outside,

    In the step (d), a conductive filament is formed inside the transparent electrode layer by applying a voltage between a portion of the transparent conductive layer exposed to the outside and the transparent electrode layer.
20. The method of claim 18, wherein in the step (a), the transparent conductive layer

    The conductive filament is formed on the transparent electrode layer formed of a resistance change material formed therein.

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