Fluorination-Enabled Monolithic Integration of Enhancement- and Depletion-Mode Indium-Gallium-Zinc Oxide TFTs

Common metal-oxide thin-film transistors (TFTs) are unipolar (n-type) in nature, operating either in the enhancement-mode (EM) or depletion-mode (DM). A simple technology allowing easy monolithic integration of both EM and DM TFTs is desirable for improved performance of a metal-oxide circuit. In this letter, the channel regions of select TFTs in a circuit were fluorinated. These TFTs remained EM when subjected to a heat-treatment in a non-oxidizing atmosphere, while the rest was turned DM. The difference between the threshold voltage of an EM and a DM TFT can be simply and precisely modulated by controlling the heat-treatment temperature and duration. An inverter monolithically constructed of EM and DM indium-gallium-zinc oxide TFTs is presented as a demonstration.