Fully room-temperature IGZO thin film transistors adopting stacked gate dielectrics on flexible polycarbonate substrate

• IGZO TFT with GeO2/TiO2/GeO2 dielectric has been fabricated on PC substrate at room temperature.
• RT Flexible TFT exhibits small gate swing of 0.132 V/decade and good Ion/Ioff ratio of 2.4 × 107.
• Such good performance was attributed to combined effect of higher-κ TiO2 and large band gap GeO2.

This study demonstrates the feasibility of producing an InGaZnO thin-film transistor (TFT) using a high-κ germanium oxide (GeO2)/titanium oxide (TiO2)/GeO2 gate stack on a flexible polycarbonate substrate. The flexible TFT exhibited a small sub-threshold swing of 0.132 V/decade, an acceptable field effect mobility of 8 cm2/(V s), and a robust Ion/Ioff ratio of 2.4 × 107. The improved device performance can be attributed to the combined effect of high-κ TiO2 and the large band gap of GeO2 that exhibits a tendency to remain in a Ge4+ oxidation state at room temperature.