Top-Down Fabrication Process of ZnO NWFETs

Abstract

ZnO NWFETs were fabricated with and without Al2O3 passivation. This was done by developing a new recipe for depositing the thin film of ZnO. By using a high donor concentration of 1.7 x 1018 cm-3 for the thin film, contact resistance values were lowered (passivated device had Rcon = 2.5 x 104 Ω; unpassivated device had Rcon = 3.0 x 105 Ω). By depositing Zn first instead of O2, steep subthreshold slopes were obtained. The passivated device had a subthreshold slope of 225 mV/decade and the unpassivated device had a slope of 125 mV/decade. Well-behaved electrical characteristics have been obtained and the passivated device shows field effect mobility of 10.9 cm2/Vs and the un-passivated device shows a value of 31.4 cm2/Vs. To verify the results, 3D simulation was also carried out which shows that the obtained values of sub-threshold slope translate into interface state number densities of-1.86 x 1013 cm-2 for the unpassivated device and 3.35 x 1014 cm-2 for the passivated device. The passivated device is suitable for biosensing applications.