Ambipolar organic thin-film field-effect transistor and making method

• US 20060214162A1
• Filed: 03/23/2006
• Published: 09/28/2006
• Est. Priority Date: 03/25/2005
• Status: Active Grant

• Current Assignee: Osaka University, Shin-Etsu Chemical Company Limited
• Original Assignee: Osaka University, Shin-Etsu Chemical Company Limited
• Inventors: Mizuno, Eriko, Kawai, Tomoji, Taniguchi, Masateru, Fukui, Ikuo
• Granted Patent: US 7,265,380 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/471 the gate dielectric comprising only organic materials
• CPC Class Codes: H10K 85/311 Phthalocyanine

Abstract

In a thin-film field-effect transistor having metal/insulator/semiconductor (MIS) structure, the semiconductor layer is formed of an organic compound, and the insulator layer is formed of an organic compound which is soluble in an organic solvent and exhibits spontaneous polarization similar to ferroelectric material. The transistor exhibits n-type transistor characteristics when polling is conducted by applying a voltage which is not less than a coercive electric field and not more than a withstand voltage between source and gate electrodes, and absent polling, the transistor exhibits p-type transistor characteristics.

Claims

1. An ambipolar organic thin-film field-effect transistor having metal/insulator/semiconductor structure, wherein

the material of which the semiconductor layer is made comprises an organic compound, and the material of which the insulator layer is made comprises an organic compound which is soluble in an organic solvent and exhibits spontaneous polarization similar to ferroelectric material,

the transistor exhibits n-type transistor characteristics when polling is conducted by applying a voltage which is not less than a coercive electric field and not more than a withstand voltage of the organic compound of the insulator layer between source and gate electrodes, and the transistor exhibits p-type transistor characteristics when polling is not conducted.

2. The transistor of claim 1, wherein the organic compound of which the insulator layer is made is a polymer having a weight average molecular weight of 2,500 to 1,000,000.

3. The transistor of claim 1, wherein the organic compound of which the insulator layer is made is an insulating polymer having cyano groups.

4. The transistor of claim 3, wherein the organic compound of which the insulator layer is made is an insulating polymer having cyanoethyl groups.

5. The transistor of claim 4, wherein the organic compound of which the insulator layer is made is cyanoethylpullulan.

6. The transistor of claim 1, wherein the organic compound of which the insulator layer is made has a withstand voltage of at least 1 MV/cm, a coercive electric field of at least 50 kV/cm, and a spontaneous polarization Pr of at least 1.5 μ

C/cm².

7. A method for preparing an ambipolar organic thin-film field-effect transistor, comprising the steps of:

applying a solution of an organic solvent-soluble organic compound in an organic solvent onto a gate electrode in the form of a metal layer,

drying the applied solution to form an insulator layer, and

laying a semiconductor layer on the insulator layer.