Flexible quasi-vertical In-Ga-Zn-O thin-film transistor with 300-nm channel length

In this letter, we report a flexible Indium–Gallium–Zinc-Oxide quasi-vertical thin-film transistor (QVTFT) with 300-nm channel length, fabricated on a free-standing polyimide foil, using a low-temperature process <150 °C. A bilayer lift-off process is used to structure a spacing layer with a tilted sidewall and the drain contact on top of the source electrode. The resulting quasi-vertical profile ensures a good coverage of the successive device layers. The fabricated flexible QVTFT exhibits an ON/OFF current ratio of 10^{4} , a threshold voltage of 1.5 V, a maximum transconductance of 0.73 \mu text{S}~\mu {\rm m}^{-1} , and a total gate capacitance of 76 nF \mu {\rm m}^{-1} . From S-parameter measurements, we extracted a transit frequency of 1.5 MHz. Furthermore, the flexible QVTFT is fully operational when bent to a tensile radius of 5 mm.