1 V-Operable High-Mobility Amorphous Indium–Tin–Gallium–Zinc Oxide Thin-Film Transistors with High- k Hafnium Dioxide Gate Dielectrics through Continuous Atomic Layer Deposition

High-mobility amorphous indium–tin–gallium–zinc oxide (ITGZO) thin-film transistors (TFTs) with hafnium dioxide (HfO 2 ) dielectric films are fabricated via continuous atomic layer deposition (ALD) using a liquid delivery system . The ITGZO TFTs prepared with a single cocktail precursor exhibit improved interfacial characteristics owing to the low surface roughness of the gate dielectric and channel layers and their high proportion of metal–oxygen bonding structures. A high field-effect mobility (up to 150 cm 2 V –1 s –1 ), high on/off current ratio (>10 8 ), and low subthreshold swing (<0.07 V dec –1 ) at operating voltages within 1 V are achieved. To the best of our knowledge, this work is the first to report the highest mobility of 1 V-operable metal-oxide TFTs even with an amorphous-phase channel, which is comparable with those of polycrystalline silicon-based TFTs. The origin of the exceptional electrical characteristics of the resulting devices is analyzed by investigating the role of continuous ALD and Sn incorporation into the IGZO film. Low activation energies (∼15 meV) and density of trap states (∼9.3 × 10 21 eV –1 cm –3 ) are determined, indicating superior charge-transport properties compared with other reported ALD-based metal-oxide TFTs.