93.6 cm² V^-1·s^-1 Homostructure a-IGZO Thin-Film Transistor with High-k Gate Dielectric Fabricated at Room Temperature

In this work, amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) with HfLaO gate dielectric have been fabricated at room temperature. The carrier mobility of the TFTs can be significantly improved by adopting homostructure a-IGZO layers with various stoichiometric ratios. This improvement can be attributed to the raised carrier density in indium-rich a-IGZO because more donor-like oxygen vacancies are induced by the content of indium oxide, reducing the source/drain electrode contact resistance. Moreover, multiple channels can be formed in the homostructure, simultaneously contributing to carrier transport. As a result, high-performance TFTs with a a-I_1.0G_2.9Z_0.2O_y/a-I_1.0G_3.1Z_0.2O_y/a-I_1.0G_2.9Z_0.2O_y homostructure have been obtained with an ultra-high mobility of 93.6 cm² V^-1·s^-1, a low subthreshold swing of 0.12 V dec^-1, a low threshold voltage of 2.5 V, and an impressive ION/IOFF ratio of 3.4×10⁷. Besides, the intrinsic three-terminal structure of the homostructure TFTs was further exploited to concurrently mimic the biological behaviors of neurotransmitters and neuromodulators, achieving synaptic behaviors of long-term potentiation (LTP) and depression (LTD).