A Low Operating Voltage ZnO Thin Film Transistor Using a High- κ HfLaO Gate Dielectric

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 (V T ) of 0.28 V, a small subthreshold swing (SS) of 0.26 V/dec, an acceptable mobility (μ sat ) of 3.5 cm 2 /V s, and a good I on/ I off ratio of I × 10 6 . The SS heavily depends on the HfLaO/ZnO interface charges, a property which is related to the degree of crystallization of ZnO. The low V T and the small SS allow device voltage operation below 2 V for low power application.

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