Room temperature fabricated ZnO thin film transistors with high-k $(Bi_1.5_}Zn_{1.0}Nb_{1.5}O_7)_{0.7}(MgO)_{0.3}$ gate insulators

Abstract

Low voltage organic TFTs (OTFTs) and ZnO based TFTs (<5V), utilizing room temperature deposited $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_{7}$ (BZN) thin films were recently reported, pointing to high-k gate insulators as a promising route for realizing low voltage operating flexible electronics. $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_{7}$ (BZN) thin film is one of the most promising materials for gate insulator because of its large dielectric constant (~60) at room temperature with an applied dc electric field. However their tendency to suffer from relatively high leakage current at low electric field (>0.3MV/cm) hinder the application of BZN thin films for gate insulator. In order to improve leakage current characteristics of BZN thin film, we mixed 30mol% MgO with 70mol% BZN and their dielectric and electric properties were characterized. We investigated the leakage current characteristic of $(Bi_{1.5}Zn_{1.0}Nb_{1.5}O_{7})_{0.7}(MgO)_{0.3}$ thin film and reported the results of the fabrication and characterization of thin film transistor using $(Bi_{1.5}Zn_{1.0}Nb_{1.5}O_{7})_{0.7}(MgO)_{0.3}$ gate insulator and ZnO active layer at room temperature by rf magnetron sputtering technique on PET and glass substrate. The devices exhibited low operation voltages (on PET, 1.2V and glass, 1.68V), high mobility (on PET, $20.4cm^2/V.s$ and glass, $35.3cm^2/V.s$) and also high on-off ratio (on PET, $6.45x10^5$ and glass, $1.88x10^5$).