Efficient suppression of charge trapping in ZnO-based transparent thin film transistors with novel Al2O3∕HfO2∕Al2O3 structure

Charge trapping is dramatically suppressed in ZnO transparent thin film transistors (TFTs) employing a multilayered gate insulator with HfO2 layer sandwiched by Al2O3 layers. In spite of its high dielectric constant, HfO2 has critical drawbacks including huge charge trap density in interfaces. We suggest and demonstrate an elegant solution to minimize the charge trapping introducing Al2O3 buffer layers. The operation of Al2O3∕HfO2∕Al2O3 multilayered gate-insulator structure in the ZnO transparent TFT is evaluated to ensure the voltage difference in the hysteresis loop as low as 0.2V, and the immunization to the threshold voltage shift induced by repeated sweeps of gate voltage.