High-k gate oxide formed by anodic oxidation for organic field effect transistors

Abstract

This chapter reports presents a comparative investigation of anodically grown HfO2 and Ta2O5 films as gate oxides for pentacene field effect transistors (OFETs). Ta and Hf films are deposited by e-beam evaporation onto highly doped Si wafers and anodization is out in a buffered solution of tartaric acid (0.1 M) mixed with ethylene glycol. After gate oxide growth, organic field effect transistors (OFETs) were completed by vacuum deposition of pentacene and gold drain and source contact through a shadow mask. Optical and electrical properties of films grown at various anodization voltage were reported which show that high quality films are obtained at room temperature. HfO2 and Ta2O5 exhibit a high dielectric constant, which leads to devices showing a good field effect mobility at low voltage. Devices with HfO2 show improved characteristics with a higher stability and a lower leakage current at low drain bias as well as a high mobility.