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 μS μm
^-1
, and a total gate capacitance of 76 nF μm
^-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.