KR20200137790A - Field effect light emission device - Google Patents

Abstract

The present invention relates to a field effect light emission device, which can simplify a circuit manufacturing process. According to an embodiment of the present invention, the field effect light emission device comprises: an active layer providing a channel region; a first graphene layer including a first region overlapping with a first end of the active layer and an extension part extending to an outside of the active layer from the first region; a first source/drain electrode including a first metal electrode coupled with the extension part of the first graphene layer; a second graphene layer including a second region overlapping with a second end of the active layer and an extension part extending to an outside of the active layer from the second region; a second source/drain electrode including a second metal electrode coupled with the extension part of the second graphene layer; a first dielectric layer formed at the channel region between the first end and the second end of the active layer; a main gate electrode on the first dielectric layer; a second dielectric layer on the first region of the first graphene layer; a first control gate electrode disposed on the second dielectric layer; a third dielectric layer on the second region of the second graphene layer; and a second control gate electrode disposed on the third dielectric layer.

Description

Field effect light emission device

The present invention relates to semiconductor technology, and more particularly, to a field control light emitting device.

In recent years, as the lighting, display device, and optical communication industries gradually develop, research to develop a multifunctional light emitting device has been continuously made. The currently used light emitting device is an inorganic light emitting diode device manufactured by selectively doping a group 3-5 semiconductor having a direct transition band gap. The basic light emission principle is that the electrons and holes injected of the inorganic light emitting diode device meet at the PN junction and recombine to emit light.

However, it is difficult to implement the inorganic light emitting diode device transparently or flexibly due to the physical properties of the material itself. As an alternative to this, transparent and flexible organic light emitting diode devices based on organic materials have been developed. However, the organic light emitting diode device is vulnerable to moisture and thus has instability that does not have a long lifespan, and has a limitation in that its performance is lower than that of the existing inorganic light emitting device due to its low luminous efficiency.

In addition, in general, one sub-pixel used in a display device includes one light-emitting diode element and one transistor that controls it. Such a structure acts as a weakness in terms of efficiency, circuit fabrication, and degree of integration, which impedes the implementation of large-area and high-resolution display devices.

Therefore, the technical problem to be solved by the present invention is that while having flexibility and transparency, a long life is secured, stable, and luminous efficiency is high, the control circuit is simplified to facilitate the circuit manufacturing process, and the high degree of integration of the circuit is high. It is to provide a field control light emitting device capable of implementing a display device capable of high resolution.

According to an embodiment of the present invention, the field control light emitting device includes an active layer providing a channel region; A first graphene layer having a first region overlapping on a first end of the active layer and an extension extending from the first region toward the outside of the active layer; And a first source/drain electrode including a first metal electrode coupled to an extended portion of the first graphene layer. A second graphene layer having a second region overlapping on a second end of the active layer and an extension extending from the second region toward the outside of the active layer; And a second source/drain electrode including a second metal electrode coupled to the extended portion of the second graphene layer. A first dielectric layer formed on the channel region between the first end and the second end of the active layer and a main gate electrode on the first dielectric layer; A second dielectric layer on the first region of the first graphene layer and a first control gate electrode disposed on the second dielectric layer; And a third dielectric layer on the second region of the second graphene and a second control gate electrode disposed on the third dielectric layer. The contact surfaces of the graphene layers bonded to the metal electrodes may be fluorinated. The second dielectric layer and the third dielectric layer may be the same dielectric layer, and the first control gate electrode and the second control gate electrode may have the same level. Both ends of the main gate electrode may be offset from an inner end of the first region and an inner end of the second region toward the first end and the second end of the active layer, respectively. The first source/drain electrode and the second source/drain electrode are disposed on a first surface of the active layer, and the main gate electrode is disposed on a second surface opposite to the first surface of the active layer. Can be. The first source/drain electrode, the second source/drain electrode, and the main gate electrode may be disposed on the same surface of the active layer. The first to third dielectric layers may be the same dielectric layer, and the first control gate electrode, the second gate electrode, and the main gate electrode may have the same level. The second dielectric layer and the third dielectric layer may encapsulate the graphene layer and the active layer. At least one of the first to third dielectric layers may include a two-dimensional hexagonal boron nitride (hBN) layer. The active layer is a transition metal dichalcogenide having one transition metal selected from the group consisting of Mo, W, Nb, Ta, Zr, Hf, Tc, Re, Cu, Ga, In, Sn, Ge, and Pb. Metal di-chalcogenides). The transition metal dichalcogenide may be tungsten diselenide (WSe ₂ ). When a positive voltage is simultaneously applied to the first control gate electrode and the second control gate electrode, the active layer operates as a P-type conductor, and simultaneously to the first control gate electrode and the second control gate electrode. When a negative voltage is applied, the active layer can operate as an N-type conductor. The graphene layer may have a structure in which 4 to 6 layers of single-layer graphene are stacked. The active layer may include a light emitting region provided by recombination of electrons and holes injected from the first control gate electrode and the second control gate electrode. The position of the emission region or the emission wavelength may be controlled by the voltage applied to the main gate electrode.

According to an embodiment of the present invention, the first and second control gate electrodes located on the region where the first and second graphene layers at both ends of the active layer overlap each other to apply an electric field to the interface between the two-dimensional semiconductor and the graphene. By adjusting the level and adjusting the height of the Schottky barrier by the change of the Fermi level, it is an inorganic device, so it is resistant to moisture, so a long life is secured, stable, and luminous efficiency is high, and flexibility and transparency due to the graphene electrode are achieved. As a single electronic device having a single electronic device in charge of light emission and control, a circuit fabrication process is easy, a high degree of integration of a circuit is achieved, and when applied to a pixel of a display device, a field control light emitting device capable of a large area and high resolution can be provided.

1A is an exploded perspective view of a field control light emitting device according to exemplary embodiments.
1B and 1C are partially enlarged views of the field control light emitting device shown in FIG. 1A.
2A and 2B are diagrams for explaining the operation of the field control light emitting device when voltages of the same sign are simultaneously applied to two control gate electrodes according to an exemplary embodiment of the present invention.
3 is a graph showing conduction characteristics of an electric field control light emitting device when voltages of the same sign are applied to two control gate electrodes according to an exemplary embodiment of the present invention.
4 is a view for explaining the operation of the field control light emitting device when voltages of different symbols are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
5 is a 3D diagram for explaining the operation of the field control light emitting device when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
6 is a current-voltage graph showing rectification characteristics when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
FIG. 7 is an optical microscope photograph of light generated from an electric field control light emitting device when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
8 is a graph showing an EL spectrum and a PL spectrum of light emitted when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
9 is a graph comparing EL spectra according to a change in a drain-source voltage when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
10 is a graph showing a relationship between a drain-source voltage and a current density when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
11 is a graph showing a relationship between a current density and an EL peak area when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
12 is a graph showing a relationship between a drain-source voltage and an EL peak area when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
13 is a graph illustrating a relationship between a voltage applied to a main gate electrode and a current when voltages of different symbols are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
14A to 14C are views for explaining the operation of the field-controlled light emitting device in regions I to III shown in FIG. 13.
FIG. 15 is a graph showing light emission characteristics of region I shown in FIG. 13 when voltages of different symbols are simultaneously applied to two control gate electrodes according to an embodiment of the present invention.
FIG. 16 illustrates EL peak areas and current densities of region I shown in FIG. 13 when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention. It is a graph showing.

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

The embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is as follows. It is not limited to the examples. Rather, these embodiments are provided to make the present disclosure more faithful and complete, and to completely convey the spirit of the present invention to those skilled in the art.

In the drawings, the same reference numerals refer to the same elements. Also, as used herein, the term “and/or” includes any and all combinations of one or more of the corresponding listed items.

The terms used in this specification are used to describe examples, and are not intended to limit the scope of the present invention. In addition, even if it is described in the singular in this specification, a plurality of forms may be included unless the context clearly indicates the singular. In addition, the terms "comprise" and/or "comprising" as used herein specify the presence of the mentioned shapes, numbers, steps, actions, members, elements and/or groups thereof. It does not exclude the presence or addition of other shapes, numbers, movements, members, elements and/or groups.

Reference to a layer formed “on” a substrate or other layer herein refers to a layer formed directly on the substrate or other layer, or formed on an intermediate layer or intermediate layers formed on the substrate or other layer. It may also refer to a layer. Further, for those skilled in the art, a structure or shape arranged “adjacent” to another shape may have a portion disposed below or overlapping with the adjacent shape.

In this specification, "below", "above", "upper", "lower", "horizontal" or "vertical" Relative terms such as, as shown on the drawings, may be used to describe the relationship between one component member, layer, or region with another component member, layer, or region. It is to be understood that these terms encompass not only the orientation indicated in the figures, but also other orientations of the device. In addition, as used herein, "two-dimensional material" refers to all materials of a two-dimensional structure in which several atomic arrangements form a layer and these layers are arranged in at least one or more layers.

In the following, embodiments of the present invention will be described with reference to cross-sectional views schematically showing ideal embodiments (and intermediate structures) of the present invention. In these drawings, for example, the size and shape of the members may be exaggerated for convenience and clarity of description, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, the embodiments of the present invention should not be construed as being limited to the specific shape of the region shown in this specification. In addition, reference numerals of members in the drawings refer to the same members throughout the drawings.

In the present specification,'graphene' may refer to a single layer graphene as well as a stack of a small number of single layer graphenes (few monolayers). For example, the small number may be in the range of 1 to 6.

1A is an exploded perspective view of an EL device according to an embodiment of the present invention. 1B and 1C are partially enlarged views of the field control light emitting device shown in FIG. 1A. In FIG. 1C, the relative positional relationship between the inner ends of the graphene layers 101 and 201 and both ends of the main gate electrode 32 is shown by a dashed line and a dotted line.

1A and 1B, the field control light emitting device 300 according to an exemplary embodiment includes an active layer 31 disposed on the first dielectric layer 30 and the first dielectric layer 30 to provide a channel region. ), a first source/drain electrode including a first graphene layer 101 and a first metal electrode 104, a second source including a second graphene layer 201 and a first metal electrode 204 /Drain electrode, the main gate electrode 32 on the first dielectric layer 30 and the first dielectric layer 30, the first control gate electrode 102 on the second dielectric layer 103 and the second dielectric layer 103 ) And a third dielectric layer 203 and a second control gate electrode 202 on the third dielectric layer 203. The active layer 31 may have a first end (31e(1) in FIG. 1C) and a second end (31e(2) in FIG. 1C) spaced apart from each other.

The first and second metal electrodes 104 and 204 may be coupled to the first graphene layer 101 and the second graphene layer 201, respectively. Regarding the material of the metal electrodes 104 and 204, an example of the control gate electrodes 102 and 202 to be described later may be referred to. The metal electrodes 104 and 204 and the main gate electrode 32 to be described later may be formed of the same material. The above-described embodiments are exemplary, and the present invention is not limited thereto.

According to an embodiment, the active layer 31 may include a 2D semiconductor material. The 2D semiconductor material may include any one of black phosphorus and transition metal chalcogenides, or a combination thereof (eg, a layered structure, a mixture or a compound of these matters). The transition metal chalcogenide is one of Mo, W, Nb, Ta, Zr, Hf, Tc, Re, Cu, Ga, In, Sn, Ge, Pb, and one of S, Se, and Te. It may include. For example, transition metal chalcogenide is a transition metal dichalcogenide (Transition Dichalcogenides) MoS ₂ , MoSe ₂ , MoTe ₂ , WSe ₂ , WTe ₂ , WS ₂ , ZrS ₂ , ZrSe ₂ , HfS ₂ , HfSe ₂ And NbSe ₂ may include any one of. In some embodiments, the metal chalcogenide-based material is a _first metal chalcogenide material including MoS ₂ , MoSe ₂ , MoTe ₂ , WSe ₂ , WTe ₂ or WS ₂ and ZrS ₂ , ZrSe ₂ , HfS ₂ , HfSe The second metal chalcogenide material including ₂ or NbSe ₂ may include a reaction compound generated by covalent bonding or metal bonding with each other. According to an embodiment, the 2D semiconductor material included in the active layer 31 may be a material composed of a monolayer.

The 2D semiconductor material may be a bipolar semiconductor using both electrons and holes as driving charges. Since the active layer 31 includes a bipolar semiconductor, the device characteristics may be changed to n-type or p-type depending on the polarity of the applied electric field control voltage, and the change of the device characteristics will be described later with reference to FIGS. 2A to 2B. I will do it. The bipolar semiconductor is black phosphorus, MoS2, WS2, NbS2, TaS2, ZrS2, HfS2, TcS2, ReS2, CuS2, GaS2, InS2, SnS2, GeS2, PbS2, MoSe2, WSe2, NbSe2, TaSe2, ZrSe2, HfSe2, TcSe2, ReS2, TcS2 At least one of CuSe2, GaSe2, InSe2, SnSe2, Ge Se2, PbSe2, MoTe2, WTe2, NbTe2, TaTe2, ZrTe2, HfTe2, TcTe2, ReTe2, CuTe2, GaTe2, InTe2, SnTe2, GeTe2, and PbTe2 may be included.

The two-dimensional semiconductor may function as a light emitting layer. As the emission layer, preferably, the two-dimensional semiconductor may be a bipolar two-dimensional semiconductor. The principle of light emission in the emission layer will be described later in detail with reference to FIG. 4.

The first dielectric layer 30 may be disposed on the active layer 31. The first dielectric layer 30 may be formed on the channel region between the first end 31e(1) and the second end 31e(2) of the active layer 31. According to an embodiment of the present invention, the first dielectric layer 32 may serve as a substrate for the field control light emitting device 300. The first dielectric layer 30 may be selected from various materials capable of forming a thin film on it by a film formation method such as a solution method or a vapor deposition method. For example, silicon, silicon-germanium, silicon carbide (SiC), or It can be formed of glass. In another embodiment, the first dielectric layer 30 may be formed of a flexible material to implement the flexible field control light emitting device 300. For example, the flexible material may be selected from a polyester-based polymer, a silicone-based polymer, an acrylic polymer, a polyolefin-based polymer, a copolymer thereof, or a hexagonal boron nitride (hBN) group. Preferably, the first dielectric layer 30 may be formed of the hexagonal boron nitride (hBN).

The hexagonal boron nitride refers to a material having a hexagonal crystal structure among compounds composed of a ratio of boron and nitrogen in a 1:1 ratio, and, similar to graphene, boron and nitrogen atoms have a hexagonal honeycomb-shaped flat crystal structure. That is, since the graphene and the crystal structure having flexibility are similar, the hexagonal boron nitride may also have flexibility. In addition, the hexagonal boron nitride has a band spacing of about 6 eV, unlike the graphene, and thus has excellent performance as an insulating layer. In addition, since boron and nitrogen are bonded by strong covalent bonds, the physical and chemical stability is high, so that it can be used as a sealing layer as described later.

The main gate electrode 32 may be disposed on the first dielectric layer 30. The main gate electrode 32 may be physically spaced apart from the first control gate electrode 102 and the second control gate electrode 202 to be described later. As for the material of the main gate electrode 32, examples of the control gate electrodes 102 and 202 to be described later may be referred to.

Graphene constituting the graphene layers 101 and 201 is a transparent and flexible material, and has high conductivity among two-dimensional materials, and has excellent properties as a conductor, so it has great use value as a flexible electrode in wearable electronic devices. In addition, since the graphene is a two-dimensional material having a very thin thickness, it does not have a masking effect, and thus, unlike a bulk material, all charges may be affected by an electric field. Therefore, the properties of graphene as a two-dimensional material can be effectively controlled by the electric field.

The graphene layers 101 and 201 may have a structure in which single-layer graphenes are stacked in about 4 to 6 layers. The graphene layers 101 and 201 exhibit various electrical properties depending on the number and shape of the stacked layers, and multilayer graphene may have relatively close electrical properties to semiconductors when the number of stacked layers is small (2 to 3 layers). have. Conversely, in the case of a multilayer graphene stacked with four or more layers, the multilayer graphene may have electrical properties close to metal.

Referring to FIG. 1C, the first graphene layer 101 and the second graphene layer 201 are respectively overlapped on the first end 31e(1) of the active layer 31 and a second region. It may have a second area overlapping on the end 31e(2). According to an embodiment, both ends of the main gate electrode 32 are respectively from the inner end of the first region (101e in Fig. 1C) and the inner end of the second region (201e in Fig. 1C). It may be offset toward the first end 31e(1) and the second end 31e(2).

The control gate electrodes 102 and 202 that may be disposed on the first region and the second region will be described later. According to an embodiment, the first graphene layer 101 and the second graphene layer 201 are extended portions 105 further extending from the first region and the second region to the outside of the active layer 31, 205). The extensions 105 and 205 may be located on the first dielectric layer 30, the second dielectric layer 103, or the third dielectric layer 203. When the graphene layers 101 and 201 have extensions 105 and 205, the first and second metal electrodes 104 and 204 may be coupled to the extensions 105 and 205.

According to an embodiment of the present invention, at least a portion of the graphene layers 101 and 201 may include fluorographene (FG of FIG. 1B) formed by fluorination of graphene. The graphene fluoride may function as a contact surface for bonding the graphene layers 101 and 201 to the first metal electrode 104 or the second metal electrode 204. When the graphene fluoride is disposed on the contact surface of the graphene layers 101 and 201, it prevents the metal electrodes 104 and 204 from directly reacting with the 2D semiconductor surface to prevent the Fermi level fixation phenomenon. , Fluorine can increase charge transfer efficiency by acting as a mediator of charge transfer between graphene and metal. Accordingly, electric charges can be effectively injected from the metal to the 2D semiconductor, and an interface with low resistance can be formed to lower the electrode resistance of the 2D semiconductor device. In addition, since graphene fluoride serves as an encapsulation layer, characteristics and stability of the device may be improved.

In one embodiment, by having a heterojunction structure in which a two-dimensional material of the graphene layers 101 and 201 and a two-dimensional material of the active layer 31 are stacked, various electronic devices and circuits can be formed within a thickness range of several nanometers. It can be configured, and it may be easy to implement a flexible and transparent wearable electronic device that is difficult to implement with a conventional silicon-based electronic device. In addition, electronic devices based on two-dimensional materials have high flexibility and transparency, and in addition, they have high charge mobility and electric field control characteristics, so that the utility value of the device can be increased. Among the two-dimensional materials, graphene, which has very high conductivity, is used as a transparent and flexible electrode, and when stacked with other materials to form a heterojunction structure, doping by an electric field is possible due to a unique band structure.

In one embodiment, the first control gate electrode 102 and the second control gate electrode 202 are each of the first region of the first graphene layer 101 and the second region of the second graphene layer 101. It can be placed on the area. The control gate electrodes 102 and 202 may control electrical characteristics of the first region and the second region by applying an electric field to the interface between the semiconductor and the graphene electrode. The control gate electrodes 102 and 202 change the Fermi level of graphene contained in the graphene layers 101 and 201 by applying an electric field to the interface between the active layer 31 and the graphene layers 101 and 201. The height of the key barrier can be adjusted. According to an embodiment, the two control gate electrodes 102 and 202 are configured to control only the first region and the second region, which are regions in which the graphene layers 101 and 201 and the active layer 31 contact each other. The channel region provided by the active layer 31 may be controlled by the main gate electrode 32 to control the charge concentration (doping) in the channel region.

The control gate electrodes 102 and 202 may include metal. For example, the control gate electrode 102 is aluminum (Al), gold (Au), beryllium (Be), bismuth (Bi), cobalt (Co), copper (Cu), hafnium (Hf), indium (In), Manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), palladium (Pd), platinum (Pt), rhodium (Rh), rhenium (Re), ruthenium (Ru), tantalum (Ta), It may contain at least one of tellium (Te), titanium (Ti), tungsten (W), zinc (Zn), or zirconium (Zr). The control gate electrodes 102 and 202 may be a non-metal having conductivity. For example, the control gate electrodes 102 and 202 may include polysilicon or indium-tin oxide (ITO). The above-described embodiments are exemplary, and the present invention is not limited thereto.

The second dielectric layer 103 may be positioned between the first control gate electrode 102 and the first graphene layer 101. The third dielectric layer 203 may be positioned between the second control gate electrode 202 and the second graphene layer 201.

According to an embodiment, the first source/drain electrode and the second source/drain electrode may be disposed on the first surface of the active layer 31. In this case, the second dielectric layer 103 and the third dielectric layer 203 may be physically connected to each other to provide the same dielectric layer. The first control gate electrode 102 and the second control gate electrode 202 respectively disposed on the second dielectric layer 103 and the third dielectric layer 203 provided as the same dielectric layer are formed in the same process step. They can have the same level so that they are formed simultaneously. According to an embodiment, when the first and second source/drain electrodes are disposed on the first surface of the active layer 31, the main gate electrode 30 is disposed on the first surface of the active layer 31. It can be disposed on an opposite second surface.

According to another embodiment not shown in FIGS. 1A and 1B, the first source/drain electrode, the second source/drain electrode, and the main gate electrode 32 may be disposed on the same surface of the active layer 31. have. In this case, the second dielectric layer 103, the third dielectric layer 203, and the above-described first dielectric layer 30 may be physically connected to each other to form the same dielectric layer. The first control gate electrode 102, the second control gate electrode 203, and the main gate electrode 32 respectively disposed on the first dielectric layer 30 to the third dielectric layer 203 provided as the same dielectric layer. May have the same level as above.

According to another embodiment of the invention, not shown in FIGS. 1A and 1B, the second dielectric layer 103 and the third dielectric layer 203 may be physically spaced apart from each other. The above-described embodiments are exemplary, and the present invention is not limited thereto.

According to an embodiment, the second dielectric layer 103 or the third dielectric layer 203 may encapsulate the graphene layers 101 and 201 and the active layer 31. Since the second dielectric layer 103 or the third dielectric layer 203 serves as an encapsulation layer, the stability of the device is improved.

The second dielectric layer 103 and the third dielectric layer 203 may include a two-dimensional insulator. The two-dimensional insulator may be a single layer (monolayer). According to an embodiment of the invention, the two-dimensional insulator is graphene oxide, two-dimensional oxide (for example, Ti _0.8 O ₂ and LaNb ₂ O ₇ ), or hexagonal boron nitride (hBN) It may include at least one of. Preferably, the second dielectric layer 103 and the third dielectric layer 203 may comprise a hexagonal boron nitride (hBN) layer. As described above, the hexagonal boron nitride has excellent performance as a dielectric layer and an encapsulation layer.

2A and 2B illustrate the operation of the field control light emitting device when voltages (positive voltage and negative voltage) of the same sign are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention. It is a drawing for explanation.

2A and 2B, when a positive (positive) voltage (NI) is applied to the first control gate electrode 102 and the second control gate electrode 202 in the same manner, both graphene is generated by the electric field effect. The concentration of electrons in the active layer 31 increases because the Fermi level of the layers 101 and 201 increases and the Schottky Barriers for electrons decrease. Only electrons are selectively injected from the graphene layer 101 electrically connected to one metal electrode (104 in FIG. 1A), and holes are injected from the graphene layer 201 electrically connected to the other metal electrode (204 in FIG. 1A). Therefore, the concentration of electrons in the active layer 31 increases, and the active layer 31 exhibits the characteristics of an n-type semiconductor device. Conversely, when a negative (negative) voltage (PI) is applied to the first control gate electrode 201 and the second control gate electrode 202 in the same manner, the Fermi level of graphene and WSe ₂ decreases and As the Schottky Barriers are lowered, the conductivity for holes increases, and the conductivity for electrons decreases. Since only holes are selectively injected from the graphene layer 201 electrically connected to one metal electrode 204, and electrons cannot be injected from the graphene layer 101 electrically connected to the other metal electrode 104, the active layer ( 31) As the concentration of holes increases, the active layer 31 exhibits characteristics of a p-type semiconductor device. Therefore, by controlling the voltage of the control gate electrode 32 in the electrode region without any physical or chemical doping on the active layer 31, each field control light emitting device 300 exhibits a p-type or n-type characteristic A circuit configuration in which a plurality of elements 300 are disposed is possible.

3 is a graph showing conduction characteristics of an electric field control light emitting device when voltages of the same sign are applied to two control gate electrodes 102 and 202 at the same time according to an embodiment of the present invention. The voltage (V _bg ) of the main gate electrode 32, the voltages (V _tg1 , V _tg2 ) and current density (J _ds ) applied to the two control gate electrodes 102 and 202 may vary, and the graph is It is only a non-limiting experimental example, and the various examples are not limited to specific experimental conditions.

Referring to FIG. 3, when no voltage is applied to the first control gate electrode 102 and the second control gate electrode 202, the conductivity increases as a strong positive voltage is applied to the main gate electrode 32. It can be seen that it basically has the characteristics of an n-type semiconductor device. When the positive voltage NI is applied to the first control gate electrode 102 and the second control gate electrode 202, any voltage is applied to the first control gate electrode 102 and the second control gate electrode 202 It can be seen that the conductivity increases more than the case without. That is, the characteristics of the n-type semiconductor device are further enhanced. Conversely, when negative voltage (PI) is applied to the first control gate electrode 102 and the second control gate electrode 202, any voltage is applied to the first control gate electrode 102 and the second control gate electrode 202. It can be seen that the conductivity increases as a strong negative voltage is applied to the main gate electrode 32, unlike the case where no application is applied. That is, the characteristics of the p-type semiconductor device are further enhanced.

4 and 5 are diagrams for explaining the operation of the field control light emitting device when voltages of different symbols are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention, and 3D It's a diagram.

Referring to FIGS. 4 and 5, the field-controlled light emitting device according to an embodiment of the present invention has a stepwise energy band structure of five regions of a graphene layer-an overlap region-an active layer-an overlap region-a graphene layer. A positive voltage NI and a negative voltage PI, or a negative voltage PI and a positive voltage NI are respectively applied to the first control gate electrode (102 in FIG. 1) and the second control gate electrode (202 in FIG. 1). Apply. In this case, electrons are injected into the graphene layer as the Fermi level of the graphene layer on one side formed under the control gate electrode to which a positive voltage is applied by the electric field effect is increased, and graphene on the other side formed under the control gate electrode to which a negative voltage is applied. Holes are injected into the graphene layer as the Fermi level of the graphene layer falls in the layer. When the density of holes and electrons in the active layer is changed by adjusting the Fermi level of the active layer containing a bipolar semiconductor (for example, tungsten diselenide (WSe ₂ )), the changed hole and electron density is optimally matched. As electrons and holes recombine, the active layer 31 including the electrons and holes emit light. At this time, using the main gate electrode 32 The Fermi level of the active layer 31 can be adjusted. When the electric field applied to the main gate electrode 32 is adjusted, the doping level of the active layer 31 and the conductivity of electrons and holes are changed, so that the position where the holes and electrons are bonded can be controlled. That is, by finely controlling the region where electrons and holes recombine, the emission point in the active layer can be controlled.

By controlling the density of injected electrons and holes, the emission wavelength can also be controlled by controlling the formation of trions and types and density of excitons. Exciton is a quasi-particle state in which negatively charged electrons and positively charged holes are combined by coulomb attraction, and is generated when light is irradiated, and excitons return to the ground state to contribute to light emission. Trion refers to a quasi-particle state in which additional electrons or holes are attached to excitons.It is unstable in 3D semiconductors and cannot contribute to light emission.However, in 2D semiconductors, it can exist in a stable state even at room temperature due to strong coulomb attraction. Can contribute to light emission.

6 is a current-voltage graph showing rectification characteristics when voltages of different codes are simultaneously applied to two control gate electrodes according to an embodiment of the present invention. The material of the active layer 31 in contact with the graphene layers 101 and 201 may vary, and the graph is only a non-limiting experimental example, and various embodiments are not limited to specific experimental conditions.

Referring to FIG. 6, it can be seen that the source/drain current I _ds does not change linearly with a change in the applied source/drain voltage V _ds . According to the experimental example, it is shown that the field control light emitting device 300 has a rectification characteristic having unidirectional electrical conductivity when voltages of different signs are simultaneously applied to two control gate electrodes. The rectification characteristic occurs when signs of voltages applied to the first control gate electrode 102 and the second control gate electrode 202 are different from each other. For example, when a negative voltage (V _tg2 is negative, PI) is applied to the second control gate electrode 202, the hole concentration of the second graphene layer 201 increases and the electron concentration decreases. At this time, the hole concentration of the first graphene layer 101 decreases and the electron concentration increases. Accordingly, electrons may be selectively injected into the channel in the first graphene layer 101, and holes may be selectively injected in the second graphene layer 201. In this case, when a positive voltage is applied from the second metal electrode 204 electrically connected to the second graphene layer 201, holes may be injected into the second graphene layer 201 and a current may flow. Conversely, when a negative voltage is applied from the second metal electrode 204, holes must be injected from the first graphene layer 101 and electrons are injected from the second graphene layer 201 to allow current to flow. Since the concentration of holes is low in the graphene layer 101 and the concentration of electrons in the second graphene layer 201 is low, holes are not injected from the first graphene layer 101, and the second graphene layer 201 ), no current flows because electrons are not injected.

Conversely, when a positive voltage (Vtg2 is a positive value, NI) is applied to the second control gate electrode 202, the electron concentration of the second graphene layer 201 increases and the hole concentration decreases. At this time, the electron concentration of the first graphene layer 101 decreases and the hole concentration increases. Accordingly, holes may be selectively injected into the channel in the first graphene layer 101, and electrons may be selectively injected in the second graphene layer 201. At this time, when a negative voltage is applied from the second metal electrode 204 electrically connected to the second graphene layer, holes may be injected into the second graphene layer, so that current may flow. Conversely, when a positive voltage is applied from the second source/drain electrode 204, holes must be injected from the first graphene layer 101 and electrons from the second graphene layer 201 to allow current to flow. Since the first graphene layer 101 has a low hole concentration, and the second graphene layer 201 has a low electron concentration, no current flows.

7 and 8 are optical micrographs of light generated from an electric field control light emitting device when voltages of different symbols are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention. And a graph showing an EL spectrum and a PL spectrum of emitted light. The source-drain voltage (V _ds ) or the wavelength or intensity of applied light may vary, and the graph is only a non-limiting experimental example, and various embodiments are not limited to specific experimental conditions.

The phenomenon in which an atom or molecule absorbs energy can be expressed as the excitation of electrons from the ground state to the excited state, and the electrons return to the ground state after a certain period of time from the excited state. During this transition in the illuminant, some or all of the energy is emitted as light. At this time, light that is excited and emitted by light is referred to as photoluminescence (PL), and light that is excited and emitted by an electric field is referred to as electroluminescence (EL). Referring to FIGS. 7 and 8, it can be confirmed that the shape and emission wavelength of the spectrum of the electroluminescence and photoluminescence emitted from the field-controlled light-emitting device according to an embodiment of the present invention are substantially the same.

9 to 12 are compared EL spectra according to a change in drain-source voltage when voltages of different signs are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention. These graphs are shown, a graph showing a relationship between a drain-source voltage and a current density, a graph showing a relationship between a current density and an EL peak area, and a graph showing a relationship between a drain-source voltage and an EL peak area.

Referring to FIGS. 9 and 12, it can be seen that the EL intensity and the EL peak area increase as the voltage V _ds applied to the source-drain electrode increases. When the V _ds values are -1.0 V, -2.0 V, -2.5 V, -3.0 V, -3.5 V and -4.0 V, respectively, the light spectrum is P ₀ , P ₁ , P ₂ , P ₃ , P ₄ , And P ₅ . It can be seen that even if the value of V _ds increases, the intensity of light (electroluminescence) increases, but the average wavelength of emitted light does not change. Referring to FIG. 10, a current density value corresponding to a voltage (V _ds ) value (-4.0V to -2.0V) applied to the source-drain electrode can be derived. Fig. 11 shows the relationship between the derived current density value and the EL peak area when the EL spectrum is P1, P2, P3, P4, and P5, respectively. According to this, it can be confirmed that the current density and the EL peak area have a positive correlation. In addition, the relationship between the current density and the EL peak area, and the relationship between the source-drain voltage (V _ds ) and the EL peak area are in the form of a linear function with a positive slope, and from these characteristics, the light emission characteristics are It can be seen that the control is easy.

13 is a graph illustrating a relationship between a voltage applied to a main gate electrode and a current when voltages of different signs are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention. 14A to 14 are views for explaining the operation of the field-controlled light emitting devices of regions I to III shown in FIG. 13 and FIG.

Referring to FIG. 13, it can be seen that the flow of light and current varies as the voltage Vbg applied to the main gate electrode changes. Unlike general devices, the field-controlled light-emitting device 300 according to an embodiment of the present invention has a behavior that is clearly divided into a region I, a region II, and a region III. Region I is an operating region in which light is emitted while current flows. Region II is an operating region in which no current flows and no light is emitted. In addition, the region III is a region through which only current flows without light emission.

As described above (refer to the description of FIGS. 4 and 5), using the main gate electrode 32 The Fermi level of the active layer 31 can be adjusted, and by adjusting the electric field applied to the main gate electrode 32, the position where the holes and electrons meet and the emission point in the active layer 31 can be controlled.

14A to 14C, as the voltage V _bg applied to the main gate electrode 32 (omitted in FIGS. 14A to 14C) increases from negative to positive, the Fermi level of the active layer 31 increases. While electrons are injected into the active layer 31, the hole concentration decreases and the electron concentration increases. In region I, since a region having a high electron concentration and a region having a high hole concentration exist in the active layer 31, a portion of the active layer may have p-type and n-type characteristics, respectively, thereby forming a pn junction. Accordingly, electrons and holes meet in the active layer 31 and light emitted from the active layer 31 can be observed. The maximum current value of the region I and the maximum light intensity (EL intensity) to be described later are found in the region where the hole and electron concentrations are balanced. The reason that the Vbg value having the maximum current value in the region I is biased to less than 0V is that the active layer 31 having n-type semiconductor characteristics is used, and the V _bg value having the maximum current value according to the type of the active layer 31 Can be different. In region II, the active layer 31 forms a depletion region. Electrons are injected into the active layer 31, but the channel is insufficient to have conductivity, and the energy barrier for the holes is increased so that holes cannot be injected any more, so that no current flows and no light emission phenomenon occurs. In region III, it can be seen that the electron concentration of the active layer 31 further increases, and the active layer 31 exhibits n-type characteristics. Accordingly, the concentration of holes in the active layer 31 becomes thin, and the holes cannot operate as driving charges in the active layer 31. Accordingly, bonding of electrons and holes in the active layer 31 does not occur, only current flows due to movement of electrons, and no light emission phenomenon occurs.

15 and 16 are graphs showing light emission characteristics of region I shown in FIG. 13 when voltages of different symbols are simultaneously applied to two control gate electrodes 102 and 202 according to an embodiment of the present invention. And a graph showing an EL peak area and a current density.

15 and 16, in region I, an EL peak area or EL intensity has a distribution similar to the current value shown in FIG. 13. It can be seen that the EL peak area value and the EL intensity value are controlled by the voltage (V _bg ) applied to the drain-source electrode like the current density. According to the light emission characteristics shown in FIG. 15, it can be seen that even if the V _bg value changes, the intensity of the emitted light changes, but the average wavelength of the emitted light does not change.

In the present invention, a light emitting device is implemented by controlling the type of charge injected in a basic transistor structure, and an n-type light-emitting diode or a p-type light-emitting diode can be implemented through two control gate voltages. In addition, the channel region may be implemented as a light emitting region by additionally controlling the main gate voltage.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and that various substitutions, modifications, and changes are possible within the scope of the technical spirit of the present invention. It will be obvious to those who have knowledge.

30: first dielectric layer
31: active layer
31e(1), 31e(2): the first and second ends of the active layer, respectively
32: main gate electrode
101: first graphene layer
101e: inner end of the first region
102: first control gate electrode
103: second dielectric layer
104: first metal electrode
105: extended portion of the first area
201: second graphene layer
201e: inner end of the second region
202: second control gate electrode
203: third dielectric layer
204: second metal electrode
205: extension of the second area
300: field control light emitting element

Claims (15)

An active layer providing a channel region;
A first graphene layer having a first region overlapping on a first end of the active layer and an extension extending from the first region toward the outside of the active layer; And a first source/drain electrode including a first metal electrode coupled to an extended portion of the first graphene layer.
A second graphene layer having a second region overlapping on a second end of the active layer and an extension extending from the second region toward the outside of the active layer; And a second source/drain electrode including a second metal electrode coupled to the extended portion of the second graphene layer.
A first dielectric layer formed on the channel region between the first end and the second end of the active layer and a main gate electrode on the first dielectric layer;
A second dielectric layer on the first region of the first graphene layer and a first control gate electrode disposed on the second dielectric layer; And
A field control light-emitting device comprising a third dielectric layer on the second region of the second graphene and a second control gate electrode on the third dielectric layer. The method of claim 1,
The field control light emitting device in which the contact surfaces of the graphene layers bonded to the metal electrodes are fluorinated. The method of claim 1,
The second dielectric layer and the third dielectric layer are the same dielectric layer, and the first control gate electrode and the second control gate electrode have the same level. The method of claim 1,
Both ends of the main gate electrode are offset from an inner end of the first region and an inner end of the second region toward a first end and a second end of the active layer, respectively. The method of claim 1,
The first source/drain electrode and the second source/drain electrode are disposed on the first surface of the active layer,
The main gate electrode is an electric field control light emitting device disposed on a second surface opposite to the first surface of the active layer. The method of claim 1,
The first source/drain electrode, the second source/drain electrode, and the main gate electrode are disposed on the same surface of the active layer. The method of claim 6,
The first to third dielectric layers are the same dielectric layer, and the first control gate electrode, the second gate electrode, and the main gate electrode have the same level. The method of claim 1,
The second dielectric layer and the third dielectric layer encapsulate the graphene layer and the active layer. The method of claim 1,
At least one of the first to third dielectric layers includes a two-dimensional hexagonal boron nitride (hBN) layer. The method of claim 1,
The active layer is a transition metal dichalcogenide having one transition metal selected from the group consisting of Mo, W, Nb, Ta, Zr, Hf, Tc, Re, Cu, Ga, In, Sn, Ge, and Pb. Metal di-chalcogenides). The method of claim 10,
The transition metal dichalcogenide is tungsten diselenide (WSe ₂ ). The method of claim 1,
When a positive voltage is simultaneously applied to the first control gate electrode and the second control gate electrode, the active layer operates as a P-type conductor,
When a negative voltage is simultaneously applied to the first control gate electrode and the second control gate electrode, the active layer operates as an N-type conductor. The method of claim 1,
The graphene layer is an electric field control light emitting device having a structure in which 4 to 6 layers of single-layer graphene are stacked. The method of claim 1,
The active layer includes a light emitting region provided by recombination of electrons and holes injected from the first control gate electrode and the second control gate electrode. The method of claim 14,
An electric field control light emitting device in which the position of the emission region or the emission wavelength is controlled by a voltage applied to the main gate electrode.

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