Scalability of zinc oxide thin-film transistors for RF amplifiers and DC switch applications

In this work, we characterize the scalability of ZnO TFTs for RF transistor and DC switching applications through variations in channel length, total device periphery, and parasitic gate overlap capacitance. For simple device test structures that have not been optimized for either RF transistors or DC switches, we show drain current density (IDS) and Ron scalability for channel lengths (LC) from 10 µm down to 150 nm achieving IDS = 840 mA/mm. Separately, Ron·QG values as low as 359 mΩ-nC were measured for devices with mobility (μe) = 28 cm²/V·s and contact resistance (ρc) = 1 Ω·mm. Ron·QG values were observed to scale well for total device peripheries (W) ranging from 50 µm to 2 mm. Significant improvements in IDS, Ron, and Ron·QG are projected through ohmic contact and mobility optimization, as well as parasitic gate overlap capacitance scaling.