High performance ZnO nanowire field effect transistors with organic gate nanodielectrics: Effects of metal contacts and ozone treatment

High performance ZnO nanowire field effect transistors (NW-FETs) were fabricated using a nanoscopic self-assembled organic gate insulator and characterized in terms of conventional device performance metrics. To optimize device performance and understand the effects of interface properties, devices were fabricated with both Al and Au/Ti source/drain contacts, and device electrical properties were characterized following annealing and ozone treatment. Ozone-treated single ZnO NW-FETs with Al contacts exhibited an on-current (I_on) of ∼4 μA at 0.9 V_gs and 1.0 V _ds, a threshold voltage (V_th) of 0.2 V, a subthreshold slope (S) of ∼130 mV/decade, an on-off current ratio (I_on:I _off) of ∼10⁷, and a field effect mobility (μ_eff) of ∼1175 cm² V^-1 s^-1. In addition, ozone-treated ZnO NW-FETs consistently retained the enhanced device performance metrics after SiO₂ passivation. A 2D device simulation was performed to explain the enhanced device performance in terms of changes in interfacial trap and fixed charge densities.