Design rules of (Mg,Zn)O-based thin-film transistors with high-κ WO3 dielectric gates

We present a study on the design and optimization of metal-insulator-semiconductor field-effect transistors based on (Mg,Zn)O channel material with WO3 dielectric. The thickness of the dielectric and of the channel layer were adjusted independently to minimize the off-current density j(off), the subthreshold slope (SS), and to modify the turn-on voltage. For optimized dielectric thickness, values of j(off) < 10(-8) A/cm(2) and SS = 68 mV/decade were obtained. The variation of the (Mg,Zn)O-film thickness gives rise to a shift of the turn-on voltage: For 21 nm thick channels V-on = -1.68V is obtained and by reducing the thickness to 8.6 nm V-on = -0.27V. Using a Pt gate metal, normally off transistors with V-on = 0.19V were realized. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764559]