JP2008235374A - Organic field effect transistor - Google Patents

Abstract

An organic field effect transistor capable of improving device characteristics is provided.
An organic field effect transistor according to an embodiment includes an organic semiconductor layer, a source electrode and a drain electrode formed on one surface of the organic semiconductor layer, and one of the organic semiconductor layers. A gate insulating film 12 formed on at least a region between the source electrode 13 and the drain electrode 14, and a gate electrode 11 formed on the gate insulating film 12 and on the opposite side of the organic semiconductor layer 15. And a carrier supplement layer 16 that is formed between the organic semiconductor layer 15 and the gate insulating film 12 or on the other surface of the organic semiconductor layer 15 and supplements carriers in the organic semiconductor layer 15.
[Selection] Figure 1

Description

  Some embodiments of the present invention relate to organic field effect transistors.

In recent years, research on an organic semiconductor element including an active layer (hereinafter referred to as an organic semiconductor layer) using an organic semiconductor material has been actively performed (for example, see Patent Document 1). A semiconductor material used for such an organic semiconductor element has characteristics such as a low environmental load, a low productivity cost, a simple manufacturing process, and mechanical flexibility. Therefore, such an organic semiconductor element can be manufactured by a low-temperature process as compared with a conventional inorganic semiconductor element having an active layer (hereinafter referred to as an inorganic semiconductor layer) using an inorganic semiconductor material such as silicon. It has characteristics such as being capable of mass production of large area elements and being able to manufacture flexible semiconductor elements.
JP 2005-268715 A

  However, at present, the performance of organic semiconductor elements does not reach that of inorganic semiconductors, and its application is considered to be limited to use as an image display element in a display. It is desired to open the way to a wide range of applications such as logic circuit element applications by realizing a high mobility element capable of moving carriers at a higher speed in an organic semiconductor, and realizing high responsiveness with fewer inputs.

  Some aspects of the present invention have been made in view of the above circumstances, and an object thereof is to provide an organic field effect transistor capable of improving device characteristics.

  An organic field effect transistor according to the present invention includes an organic semiconductor layer, a source electrode and a drain electrode formed on one surface of the organic semiconductor layer, and on one surface of the organic semiconductor layer, A gate insulating film formed in a region between the source electrode and the drain electrode; a gate electrode formed on the gate insulating film opposite to the organic semiconductor layer; and the organic semiconductor layer and the gate insulating film A carrier replenishment layer that is formed between the films or on the other surface of the organic semiconductor layer and replenishes carriers in the organic semiconductor layer.

  According to such a configuration, more carriers than the normal capacitance model are supplied to the organic semiconductor layer by the carrier supplement layer, and as a result, the drain current and the conductivity can be increased. Therefore, the response to the same gate voltage as the conventional one is improved.

The organic semiconductor layer is preferably made of a material having a carrier mobility of 1 cm ² / Vs or higher. Alternatively, the organic semiconductor layer is preferably made of an organic semiconductor single crystal. Thereby, an organic field effect transistor with high carrier mobility can be realized.

  For example, the carrier supplement layer is made of a polar monomolecular film. The polar monomolecular film is preferably formed of molecules having a polarizability of 0.5 or more. Thereby, an excellent carrier replenishment effect from the polar monomolecular film can be obtained. In order to obtain such a polarizability, the polar monomolecular film preferably contains fluorine.

  When the organic semiconductor layer is p-type, the carrier supplementary layer is made of a material having acceptor properties with respect to the organic semiconductor layer. In such a configuration, electrons are attracted from the organic semiconductor layer by the carrier supplement layer, and as a result, carriers (holes) are supplied into the organic semiconductor layer.

  When the organic semiconductor layer is n-type, the carrier supplement layer is made of a material having a donor property with respect to the organic semiconductor layer. In such a configuration, electrons serving as carriers are supplied into the organic semiconductor layer by the carrier supplement layer.

  Furthermore, in order to achieve the above object, an organic field effect transistor according to the present invention includes an organic semiconductor layer, a source electrode and a drain electrode formed on one surface of the organic semiconductor layer, and the organic semiconductor layer. A gate insulating film formed on at least one region between the source electrode and the drain electrode; and a gate electrode formed on the gate insulating film on the opposite side of the organic semiconductor layer. And a monomolecular film interposed between the organic semiconductor layer and the gate insulating film and formed using a monofunctional silane compound.

  According to such a configuration, the monomolecular film adheres to the surface of the source electrode and the drain electrode by providing the monomolecular film formed using the monofunctional silane compound between the organic semiconductor layer and the gate insulating film. This can be prevented, and a monomolecular film can be formed only on the gate insulating film. As a result, it is possible to realize an organic field effect transistor in which a pinch-off region is easily formed and a saturation characteristic is easily obtained while controlling a threshold voltage with a monomolecular film.

The monofunctional silane compound is represented by the general formula R ¹ SiR ² ₂ X (wherein R ¹ is an alkyl group or a derivative thereof, R ² is an inert group, and X is a hydrolyzing group).

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of the organic field effect transistor according to the first embodiment.
The organic field effect transistor 1 includes a gate electrode 11, a gate insulating film 12 formed on the gate electrode 11, a source electrode 13 and a drain electrode 14 formed on the gate insulating film 12, and a gate insulating film 12. The formed organic semiconductor layer 15 and a carrier supplement layer 16 formed between the organic semiconductor layer 15 and the gate insulating film 12 are included.

  The field effect transistor 1 according to the present embodiment is formed on a substrate (not shown). The material constituting the substrate is not particularly limited, and a resin sheet, glass, ceramic, metal, alloy, or the like can be used as appropriate.

  A gate electrode 11 is formed on the substrate. In the present embodiment, for example, the gate electrode 11 is composed of a conductive region formed by introducing impurities into a silicon wafer (not shown).

The gate insulating film 12 is made of, for example, polymers such as polystyrene, polyimide, polycarbonate, polyester, polyvinyl alcohol, polyurethane, epoxy resin, and phenol resin; oxides such as silicon oxide, aluminum oxide, titanium oxide, and zinc oxide; SrTiO ₃ , BaTiO ₃ Ferroelectric oxides such as: nitrides such as silicon nitride and aluminum nitride can be used.

  The source electrode 13 and the drain electrode 14 are made of a metal film such as gold, platinum, copper, titanium, chromium, nickel, and cobalt, for example.

The organic semiconductor layer 15 is preferably made of an organic semiconductor single crystal in which organic molecules are periodically arranged, or an organic semiconductor material having a high carrier mobility of at least 1 cm ² / Vs. Examples of such compounds include oligoacene molecules such as pentacene, tetracene, and anthracene; (2) oligoacene derivative molecules such as rubrene, tetramethylpentacene, tetrachloropentacene, and diphenylpentacene; and (3) oligothiophene molecules such as sexual thiophene and derivatives thereof. Molecule, (4) TCNQ (7,7,8,8-tetracyanoquinodimethane) and its derivative molecule, (5) TTF (1,4,5,8-tetrathiafulvalene) and its derivative molecule, (6 ) Perylene and its derivative molecule, (7) pyrene and its derivative molecule, (8) fullerene molecule such as C60 and its derivative molecule, (9) metal phthalocyanine molecule such as phthalocyanine and copper phthalocyanine and its derivative molecule, (10) porphyrin and Zinc porphyrin and iron Metal porphyrin and its derivative molecules such as porphyrin, (11) BEDT-TTF (bisethylenedithio tetrathiofulvalene) and the like derivative molecules. In particular rubrene, pentacene is preferred.

  The carrier supplement layer 16 supplies additional carriers in addition to the carriers that are normally induced according to the voltage applied to the gate electrode 11. In order to exhibit such an action, the carrier supplement layer 16 preferably has a high electron accepting property (acceptor property) with respect to the p-type organic semiconductor layer 15. For the n-type organic semiconductor layer 15, the carrier supplement layer 16 preferably has a high electron donating property (donor property).

  In this embodiment, a polar monomolecular film is used as the carrier supplement layer 16. The acceptor property or donor property of a polar monomolecular film can be evaluated by the polarizability. In addition, acceptor property or donor property can also be evaluated by electronegativity or electron affinity instead of polarizability.

  When evaluating by the polarizability, the polar monomolecular film preferably has a polarizability of 0.5 or more, more preferably 2.0 or more. The polar monomolecular film having a polarizability of 0.5 or more is preferably formed from a perfluoroalkylsilane compound.

  In the case of the p-type organic semiconductor layer 15, the polar monomolecular film preferably contains an element or substituent having a high electronegativity. The electronegativity defines the ability of atoms in the molecule to attract electrons, and the higher this value, the higher the acceptor property of the carrier supplement layer 16. Examples of such elements and substituents include methoxy group, alkoxy group, halogen, group 14 element, and group 15 element.

  Next, an example of the manufacturing method of the organic field effect transistor according to the present embodiment will be described with reference to FIGS.

<Preparation of organic semiconductor single crystal>
First, a method for forming the organic semiconductor layer 15 will be described. For example, a single crystal of a sublimable organic compound such as rubrene, pentacene, or tetracene can be produced by a technique called physical vapor transport. Hereinafter, a method for manufacturing a field effect transistor using a rubrene single crystal will be described.

  FIG. 2 is a diagram for explaining the physical vapor transport method. In this method, first, as shown in FIG. 2, an inert gas such as argon is allowed to flow through a tubular electric furnace 9 to which a temperature gradient is applied, so that the upstream side of the tubular electric furnace 9 is heated to a higher temperature. Next, powdery organic semiconductor raw material 7, for example, rubrene, is placed on the high temperature part, the temperature is set so that the high temperature part becomes 220 ° C., and it is slowly sublimated and crystallized in the low temperature part downstream. Furthermore, the obtained crystal 8 is placed on the upstream portion again, and crystallization is repeated several times (for example, three times), whereby a high-purity organic semiconductor crystal can be obtained. In this way, a normal rubrene single crystal having a flat surface (typically about 0.5 mm square and a thickness of 5 μm or less) is obtained.

<Production of substrate>
As shown in FIG. 3, a conductive silicon wafer is used as the gate electrode 11, and the surface of the conductive silicon wafer is oxidized to form a gate insulating film 12 of about 500 nm made of silicon oxide. Subsequently, gold is vacuum-deposited on the gate insulating film 12 with a thickness of about 10 nm, and patterning is performed by lithography and etching to form the source electrode 13 and the drain electrode 14. The distance between the source electrode 13 and the drain electrode 14 is, for example, about 5 μm.

  As shown in FIG. 4, a carrier supplement layer 16 is formed on the gate insulating film 12. As a method for forming the carrier replenishment layer 16, a thin film forming method such as a CVD method is used. For example, a polar monomolecular film is formed using a perfluorodecylsilane compound.

  As shown in FIG. 5, the organic field effect transistor 1 is manufactured by laminating the organic semiconductor layer 15 made of the single crystal obtained in the process shown in FIG. 2 on the carrier supplement layer 16 by natural electrostatic attraction. Is done. According to this method, a transistor having no crystal grain boundary and a flat contact surface with the gate insulating film 12 on a molecular scale is formed.

  Next, the transfer characteristics and the Hall effect were measured for the organic field effect transistor 1 according to the present embodiment. As the organic field effect transistor 1 to be measured, the carrier supplementary layer 16 is provided with polar monomolecular films (F-SAMs) made of a perfluorodecylsilane compound, and the organic semiconductor layer 15 is provided with a rubrene single crystal. .

FIG. 6 is a diagram showing transfer characteristics (changes in drain current _ID and conductivity σ with respect to gate voltage V _G ) of organic field effect transistor 1. As shown in FIG. 6, when the threshold value (the drain current I _D -the extension of the straight line portion of the gate voltage V _G curve is the intersection of the horizontal axis and about 1 V in this example), the drain current I _D and the conductivity σ are exceeded. It can be seen that increases rapidly.

FIG. 7 is a diagram showing the measurement results of the Hall effect of the organic field effect transistor 1 according to this embodiment. In the Hall effect measurement, the Hall coefficient was obtained by applying a magnetic field perpendicular to the conduction surface and measuring the transverse voltage component. The upper diagram of FIG. 7 shows the result of the change of the reciprocal of the Hall coefficient R _H with respect to the gate voltage V _G (V), and the lower diagram of FIG. 7 shows the diagram of the change of the Hall mobility μ _H with respect to the gate voltage. In the upper diagram of FIG. 7, values obtained by a normal capacitance model are also shown.

The reciprocal of the Hall coefficient R _H corresponds to the carrier density. For this reason, it can be seen from the results shown in the upper diagram of FIG. 7 that the carrier density increases 10 times as the electric field is applied. From the results shown in the lower diagram of FIG. 7, the hole mobility is about 5 to 25 cm ² / Vs, and decreases as the electric field is applied.

  From the results shown in FIG. 6 and FIG. 7, by providing a polar monomolecular film as the carrier replenishment layer 16, more carriers than the normal capacitance model are supplied to the organic semiconductor layer 15. As a result, the drain current and the conductivity are increased. Can be increased. The results of examining the conductivity amplification effect due to the polarity of the monomolecular film are shown below.

FIG. 8 shows organic field effect transistors in the case where weakly polar methyl-terminated monolayers (with Me-SAMs) and strong polar fluorine-terminated monolayers (with F-SAMs) are used as the carrier replenishment layer 16, respectively. 1 shows the transfer characteristic (change in drain current _ID with respect to the gate voltage V _G ), and FIG. 9 shows the measurement result of the Hall effect at this time.

  From the results shown in FIGS. 8 and 9, it can be seen that the greater the polarity of the monomolecular film, the greater the carrier injection effect.

  As described above, according to the organic field effect transistor 1 according to the present embodiment, by providing the carrier supplement layer 16 on the side of the gate insulating film 12 of the organic semiconductor layer 15, more carriers than in the normal capacitance model are organic. As a result, the drain current and the conductivity can be increased. Therefore, the response to the same gate voltage as the conventional one is improved. For this reason, it is possible to achieve both high mobility and high responsiveness by selecting the organic semiconductor layer 15 having high carrier mobility. The organic field effect transistor 1 according to this embodiment has desirable characteristics for low power element applications such as logic circuit elements.

(Second Embodiment)
FIG. 10 is a cross-sectional view of an organic field effect transistor according to the second embodiment.
The organic field effect transistor 1 includes a gate electrode 11, a gate insulating film 12 formed on the gate electrode 11, a source electrode 13 and a drain electrode 14 formed on the gate insulating film 12, and a gate insulating film 12. The organic semiconductor layer 15 is formed, and the carrier supplementation layer 17 is formed on the organic semiconductor layer 15.

  The field effect transistor 1 according to this embodiment is different from the first embodiment in that the carrier supplementation layer 17 is formed on the organic semiconductor layer 15 on the side opposite to the gate insulating film 12. Since the configuration of the gate electrode 11, the gate insulating film 12, the source electrode 13, the drain electrode 14, and the organic semiconductor layer 15 is the same as that of the first embodiment, the description thereof is omitted.

  The carrier supplement layer 17 supplies additional carriers in addition to the carriers that are normally induced according to the voltage applied to the gate electrode 11. In order to exhibit such an action, it is preferable that the carrier replenishment layer 17 has a high electron accepting property (acceptor property) with respect to the p-type organic semiconductor layer 15. For the n-type organic semiconductor layer 15, the carrier supplement layer 17 preferably has a high electron donating property (donor property).

As the acceptor carrier supplement layer 17, F ₄ -TCNQ, TCNQ, or the like can be used. In addition, as the carrier replenishment layer 17 having a donor property, TTF molecules such as TTF, BEDT-TTF, BETS, MDT-TTF, DMET, OMTF, OMSF, HMTTF, HMTSF, TMTTF, TMTSF, TMPD, DAP, TDAP, TDAE, etc. These amine-based donor molecules can be used. As the carrier replenishment layer 17, a polar monomolecular film may be used as in the first embodiment.

  Next, an example of the manufacturing method of the organic field effect transistor according to the present embodiment will be described with reference to FIGS.

<Preparation of organic semiconductor single crystal>
First, similarly to the first embodiment, a single crystal organic semiconductor layer 15 is formed by a physical vapor transport method (see FIG. 2).

<Production of substrate>
As shown in FIG. 11, a conductive silicon wafer is used as the gate electrode 11, and the surface of the conductive silicon wafer is oxidized to form a gate insulating film 12 of about 500 nm made of silicon oxide. Subsequently, gold is vacuum-deposited on the gate insulating film 12 with a thickness of about 10 nm, and patterning is performed by lithography and etching to form the source electrode 13 and the drain electrode 14. The distance between the source electrode 13 and the drain electrode 14 is, for example, about 5 μm.

  As shown in FIG. 12, the organic semiconductor layer 15 made of a single crystal obtained in the previous step is bonded onto the gate insulating film 12 by natural electrostatic attraction. According to this method, there is no crystal grain boundary, and the contact surface with the gate insulating film 12 becomes flat on the molecular scale.

As shown in FIG. 13, a carrier supplement layer 17 is formed on the organic semiconductor layer 15. As the carrier supplementation layer 17, an F ₄ -TCNQ film is formed by, for example, vacuum deposition.

Next, the transfer characteristics and the Hall effect were measured for the organic field effect transistor 1 according to the present embodiment. Organic field effect transistor 1 to be measured is provided with F ₄ -TCNQ film as a carrier supplemented layer 17, it was used with a rubrene single crystal as the organic semiconductor layer 15.

FIG. 14 shows transfer characteristics (changes in drain current _ID and conductivity σ with respect to gate voltage V _G ) of the organic field effect transistor 1 according to the second embodiment. As shown in FIG. 14, the threshold (the drain current I _D - is the intersection of the extension line and the horizontal axis of the straight portion of the gate voltage V _G curve, in this example about 1V) exceeds the drain current I _D and conductivity It can be seen that σ increases rapidly.

FIG. 15 is a diagram showing a measurement result of the Hall effect of the organic field effect transistor 1 according to the present embodiment. In the Hall effect measurement, the Hall coefficient was obtained by applying a magnetic field perpendicular to the conduction surface and measuring the transverse voltage component. The upper diagram of FIG. 15 shows the result of the change of the reciprocal of the Hall coefficient R _H with respect to the gate voltage V _G (V), and the lower diagram of FIG. 15 shows the diagram of the change of the Hall mobility μ _H with respect to the gate voltage. The upper diagram of FIG. 15 also shows values obtained by a normal capacitance model.

The reciprocal of the Hall coefficient R _H corresponds to the carrier density. For this reason, it can be seen from the results shown in the upper diagram of FIG. 15 that the carrier density increases 2 to 3 times as the electric field is applied. From the results shown in the lower diagram of FIG. 15, the hole mobility is maintained at ² cm ² / Vs. Further, as compared with the first embodiment, it is also characteristic that the carrier increasing effect is sustained even in a region of a high gate voltage (negative) of about −20V.

From the results shown in FIG. 14 and FIG. 15, when the p-type organic semiconductor layer 15 is used, an acceptor film such as an F ₄ -TCNQ film is provided as the carrier supplementation layer 17. More carriers are supplied to the organic semiconductor layer 15, and as a result, drain current and conductivity can be increased. For the n-type organic semiconductor layer 15, the same effect can be expected by providing the donor carrier supplementation layer 17.

  As described above, according to the organic field effect transistor 1 according to the present embodiment, the carrier supplement layer 17 is provided on the organic semiconductor layer 15 on the side opposite to the gate insulating film 12, so that the conventional capacitance model can be obtained. Many carriers are supplied to the organic semiconductor layer 15, and as a result, drain current and conductivity can be increased. Therefore, the response to the same gate voltage as the conventional one is improved. For this reason, it is possible to achieve both high mobility and high responsiveness by selecting the organic semiconductor layer 15 having high carrier mobility. The organic field effect transistor 1 according to this embodiment has desirable characteristics for low power element applications such as logic circuit elements.

(Third embodiment)
FIG. 16 is a cross-sectional view of the organic field effect transistor according to the present embodiment.
The organic field effect transistor 1 includes a gate electrode 11, a gate insulating film 12 formed on the gate electrode 11, a source electrode 13 and a drain electrode 14 formed on the gate insulating film 12, and a gate insulating film 12. The formed organic semiconductor layer 15 and the monomolecular film 18 formed between the organic semiconductor layer 15 and the gate insulating film 12 are included.

  In the field effect transistor 1 according to this embodiment, a monomolecular film 18 is formed between the organic semiconductor layer 15 and the gate insulating film 12. Since the configuration of the gate electrode 11, the gate insulating film 12, the source electrode 13, the drain electrode 14, and the organic semiconductor layer 15 is the same as that of the first embodiment, the description thereof is omitted.

The monomolecular film 18 controls the threshold voltage (V _th ) of the organic semiconductor layer 15 to a desired value. In the present embodiment, the monomolecular film 18 is formed using a monofunctional silane compound. When adsorbed on the gate insulating film 12, the monomolecular film 18 has a structure in which the monofunctional group of the monofunctional silane compound is hydrolyzed.

Specifically, a monofunctional silane compound represented by the general formula of R ¹ SiR ² ₂ X can be used as the monofunctional silane compound. By changing R ¹ , the threshold voltage characteristics of the organic semiconductor layer 15 can be controlled. R ¹ is, for example, an alkyl group containing a trifluoromethyl group (—CF ₃ ), an amino group (—NH ₂ ) and the like. R ² is an inert group such as an alkyl group. Here, the inert group means a group that does not form a bond between the substrate surface or molecules in the reaction for forming a monomolecular film. From the viewpoint of reducing the steric hindrance of the monofunctional silane compound and adsorbing many monomolecular films 18 on the gate insulating film 12, R ² is preferably a small group such as a methyl group. Further, the two R ² bonded to the silicon atom may be different. X is a group that contributes to chemical adsorption on the gate insulating film 12 and is composed of a hydrolyzable group such as a halogen or an alkoxy group. As the X is hydrolyzed, the monomolecular film 18 is adsorbed on the gate insulating film 12.

The monofunctional silane compound has a lower adsorptivity than the bifunctional silane compound (R ¹ SiR ² X ₂ ) or the trifunctional silane compound (R ¹ SiX ₃ ). For this reason, the monomolecular film 18 can be prevented from adsorbing to the source electrode 13 and the drain electrode 14, and the monomolecular film 18 can be adsorbed only on the gate insulating film 12.

  Next, an example of the manufacturing method of the organic field effect transistor according to the present embodiment will be described with reference to FIGS.

<Preparation of organic semiconductor single crystal>
First, similarly to the first embodiment, a single crystal organic semiconductor layer 15 is formed by a physical vapor transport method (see FIG. 2).

<Production of substrate>
As shown in FIG. 17, a conductive silicon wafer is used as the gate electrode 11, and the surface of the conductive silicon wafer is oxidized to form a gate insulating film 12 of about 500 nm made of silicon oxide. Subsequently, gold is vacuum-deposited on the gate insulating film 12 with a thickness of about 10 nm, and patterning is performed by lithography and etching to form the source electrode 13 and the drain electrode 14. The distance between the source electrode 13 and the drain electrode 14 is, for example, about 5 μm.

  As shown in FIG. 18, a monomolecular film 18 is formed on the gate insulating film 12. The monomolecular film 18 may be formed by a gas phase method such as a CVD method, or a method using a liquid phase such as a spin coating method or a dipping method.

  As shown in FIG. 19, the organic field effect transistor 1 is produced by bonding the organic semiconductor layer 15 made of the single crystal obtained in the previous step onto the monomolecular film 18 by natural electrostatic attraction. . According to this method, a transistor having no crystal grain boundary and a flat contact surface with the gate insulating film 12 on a molecular scale is formed.

  Next, the effect of the organic field effect transistor 1 according to the present embodiment will be described.

FIG. 20 shows current-voltage characteristics (changes in drain current I _D with respect to drain voltage V _D ) of the organic field effect transistor 1 according to the present embodiment. As this embodiment, the organic field effect transistor 1 in which the monomolecular film 18 is formed on the surface of the gate insulating film 12 using the monofunctional silane compound CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (CH ₃ ) ₂ Cl. Was used.

FIG. 21 shows current-voltage characteristics of the organic field effect transistor of the comparative example. In the comparative example, an organic field effect transistor in which a monomolecular film 18 is formed on the surface of the gate insulating film 12 using the trifunctional silane compound CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₃ is used. Using.

  20 and 21, when comparing the characteristics of the device on the monomolecular film formed from two types of silane compounds, in the organic field effect transistor 1 according to this embodiment in which the adhesion of the silane compound on the drain electrode 14 is eliminated. As a result, a pinch-off region is more easily formed, and as a result, a tendency that saturation characteristics are easily obtained appears.

  As described above, according to the organic field effect transistor according to the present embodiment, the monomolecule in which the monofunctional group of the monofunctional silane compound is hydrolyzed between the organic semiconductor layer 15 and the gate insulating film 12. By providing the film 18, the monomolecular film 18 can be formed only on the gate insulating film 12. As a result, it is possible to realize an organic field effect transistor in which a pinch-off region is easily formed and saturation characteristics are easily obtained while controlling the threshold voltage by the monomolecular film 18.

The present invention is not limited to the description of the above embodiment.
In addition, various modifications can be made without departing from the scope of the present invention.

It is a schematic block diagram of the organic field effect transistor which concerns on 1st Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 1st Embodiment. It is a figure which shows the state which forms the organic electric field transistor which concerns on 1st Embodiment. It is a figure which shows the state which forms the organic electric field transistor which concerns on 1st Embodiment. It is a figure which shows the state which forms the organic electric field transistor which concerns on 1st Embodiment. It is a figure which shows the transfer characteristic of the organic field effect transistor which concerns on 1st Embodiment. It is a figure which shows the result of the Hall effect measurement of the organic field effect transistor which concerns on 1st Embodiment. It is a figure which shows the transfer characteristic of the organic field effect transistor about various carrier supplementary layers. It is a figure which shows the result of the Hall effect measurement about various carrier supplementary layers. It is a schematic block diagram of the organic field effect transistor which concerns on 2nd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 2nd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 2nd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 2nd Embodiment. It is a figure which shows the transfer characteristic of the organic field effect transistor which concerns on 2nd Embodiment. It is a figure which shows the result of the Hall effect measurement of the organic field effect transistor which concerns on 2nd Embodiment. It is a schematic block diagram of the organic field effect transistor which concerns on 3rd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 3rd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 3rd Embodiment. It is a figure which shows the state which forms the organic field effect transistor which concerns on 3rd Embodiment. It is a figure which shows the transfer characteristic of the organic field effect transistor which concerns on 3rd Embodiment. It is a figure which shows the transfer characteristic of the field effect transistor of a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic field effect transistor, 11 ... Gate electrode, 12 ... Gate insulating film, 13 ... Source electrode, 14 ... Drain electrode, 15 ... Organic-semiconductor layer, 16 ... Carrier supplement layer, 17 ... Carrier supplement layer, 18 ... Monomolecule film

Claims (10)

An organic semiconductor layer;
A source electrode and a drain electrode formed on one surface of the organic semiconductor layer;
A gate insulating film formed on one surface of the organic semiconductor layer and at least in a region between the source electrode and the drain electrode;
A gate electrode formed on the gate insulating film and on the opposite side of the organic semiconductor layer;
A carrier replenishment layer formed between the organic semiconductor layer and the gate insulating film or on the other surface of the organic semiconductor layer and replenishing carriers in the organic semiconductor layer;
An organic field effect transistor. The organic semiconductor layer is made of a material having a carrier mobility of 1 cm ² / Vs or higher.
The organic field effect transistor according to claim 1. The organic semiconductor layer is made of an organic semiconductor single crystal.
The organic field effect transistor according to claim 1. The carrier supplement layer is made of a polar monomolecular film,
The organic field effect transistor according to claim 1. The polar monomolecular film is formed from molecules having a polarizability of 0.5 or more.
The organic field effect transistor according to claim 4. The polar monomolecular film contains fluorine,
The organic field effect transistor according to claim 4. The organic semiconductor layer is p-type, and the carrier supplementation layer is made of a material having acceptor properties with respect to the organic semiconductor layer.
The organic field effect transistor according to claim 1. The organic semiconductor layer is n-type, and the carrier supplementary layer is made of a material having a donor property with respect to the organic semiconductor layer.
The organic field effect transistor according to claim 1. An organic semiconductor layer;
A source electrode and a drain electrode formed on one surface of the organic semiconductor layer;
A gate insulating film formed on one surface of the organic semiconductor layer and at least in a region between the source electrode and the drain electrode;
A gate electrode formed on the gate insulating film and on the opposite side of the organic semiconductor layer;
A monomolecular film interposed between the organic semiconductor layer and the gate insulating film and formed using a monofunctional silane compound;
An organic field effect transistor. The monofunctional silane compound is represented by the general formula R ¹ SiR ² ₂ X (wherein R ¹ is an alkyl group or a derivative thereof, R ² is an inert group, and X is a hydrolyzing group).
The organic field effect transistor according to claim 9.

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