Solution-Processed La Alloyed ZrOx High-k Dielectric for High-Performance ZnO Thin-Film Transistors

We report La alloyed ZrO
_x
high-k gate insulator (GI) for ZnO thin-film transistors (TFTs) by solution-process. The La concentration in ZrO
_x
is varied from 0 to 7.5% for optimum device performance. The atomic force microscopy and X-ray photoelectron spectroscopy analysis of 5% La alloyed ZrO
_x
GI show smooth surface with higher metal-oxide (M-O) bonds and reduced defect density in the bulk compared with pristine ZrO
_x
. Therefore, ZnO TFT using 5% La alloyed ZrO
_x
GI exhibits hysteresis-free device performance, with saturation mobility of 11.58cm
²
/V · s, I
_ON
/I
_OFF
ratio of 2.67 × 10
⁸
, threshold voltage of 1.25V, and subthreshold swing of 249mV/dec. We also achieve highly stable ZnO TFTs under positive bias stress using 5% La alloyed ZrO
_x
GI.