A low operating voltage ZnO thin film transistor using a high- κ HfLaO gate dielectric

Abstract

This study demonstrates the feasibility of producing a ZnO thin film transistor (TFT) using hafnium-lanthanum-oxide (HfLaO) as the gate dielectric. By integrating high- κ HfLaO with an amorphous ZnO channel, the resulting HfLaO/ZnO TFTs display a low threshold voltage (VT) of 0.28 V, a small subthreshold swing (SS) of 0.26 V /dec, an acceptable mobility (μsat) of 3.5 cm2 /V s, and a good Ion / Ioff ratio of 1× 106. The SS heavily depends on the HfLaO/ZnO interface charges, a property which is related to the degree of crystallization of ZnO. The low VT and the small SS allow device voltage operation below 2 V for low power application. © 2009 The Electrochemical Society.