Top-Down Fabrication Process of ZnO NWFETs

Abstract

ZnO NWFETs were fabricated with and without Al2O3passivation. 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 1018cm-3for the thin film, contact resistance values were lowered (passivated device had Rcon= 2.5 x 104Ω; unpassivated device had Rcon= 3.0 x 105Ω). 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 1013cm-2for the unpassivated device and 3.35 x 1014cm-2for the passivated device. The passivated device is suitable for biosensing applications.

ZnO Nanowire Field-Effect Transistor for Biosensing: A Review

“…Other tools such as RIE and ion beam etch produce roughness >5 nm. The fabrication process for the complete ZnO NWFET structure is as outlined in [52].…”

ZnO Nanowire Field Effect Transistor for Biosensing: A Review

“…Other tools such as RIE and ion beam etch produce roughness greater than > 5 nm. The fabrication process for the complete ZnO NWFET structure is as outlined in [134].…”

Electric Field Manipulation of Defects and Schottky Barrier Control inside ZnO Nanowires

“…Top-down nanowire fabrication methods suffer similar drawbacks and are limited by their interface state defects. 31 Likewise, isolating individual wires by drop-casting typically involves solvents that can alter the transport properties and contact resistances, 32 which are sensitive to ambient measurement and require high vacuum conditions to avoid the effects of ambient air-activated surface states. 33 It is therefore important to minimize reactant exposure by drycasting nanowires without chemical dispersion and form contacts without lithographic processing.…”

“…Further complicating transport characterization on isolated nanowires are the multiple stages of microfabrication needed to create permanent contacts. , The electrodes are usually deposited by complex, and often costly, photo and electron-beam lithography and focused ion-beam techniques , where the contributions from extrinsic surface contamination and intrinsic defects on electrical transport properties are difficult to separate. Top-down nanowire fabrication methods suffer similar drawbacks and are limited by their interface state defects . Likewise, isolating individual wires by drop-casting typically involves solvents that can alter the transport properties and contact resistances, which are sensitive to ambient measurement and require high vacuum conditions to avoid the effects of ambient air-activated surface states .…”