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.