Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

We investigated the effects of top gate voltage (VTG) and temperature (in the range of 25 to 70 degrees C) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of V-TG from -20V to +20V, decreases the threshold voltage (V-TH) from 19.6V to 3.8V and increases the electron density to 8.8 x 10(18) cm(-3). Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on V-TG. At V-TG of 20V, the mobility decreases from 19.1 to 15.4 cm(2)/V.s with increasing temperature, showing a metallic conduction. On the other hand, at V-TG of -20V, the mobility increases from 6.4 to 7.5 cm(2)/V.s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.