Development of Transparent Thin Film Transistors on PES Polymer Substrates

In this study, we demonstrate ZnO-based transparent thin film transistors (TTFT’s) implemented on polyethersulfone (PES) polymer substrates. For the developed TTFT’s, radio-frequencymagnetron sputter techniques were used to deposit Al-doped ZnO (AZO) at zero oxygen partial pressures for the source, the drain, and the gate-contact electrodes, undoped ZnO at low oxygen partial pressures for the active p-type layer, and SiO2 for the gate dielectric. The TTFT’s were processed at room temperature (RT), except for a 100 ◦C sputtering step to deposit the AZO source, drain, and gate-contact electrodes. The devices have bottom-gate structures with top contacts, are optically transparent, and operate in an enhancement mode with a threshold voltage of +13 V, a mobility of 0.1 cm/Vs, an on-off ratio of about 0.5 × 10 and, a sub-threshold slope of 4.1 V/decade.