Vertical Thin Film Transistor Based on Conductivity Modulation of Graphene Electrode by Micro-Hole Patterning

Abstract

The vertical thin film transistor (VTFT) has several advantages over the planar thin film transistor, such as a high current density and low operating voltage, because of the structural specificity. However, it is difficult to realize transistor operation in a VTFT because of the structural limitation that the gate field is blocked. As a solution, the conductivity modulation of a graphene electrode is studied with a micro-hole structure as a gate field transfer electrode. The micro-hole array pattern in the graphene allows better penetration of the gate field to junction and the work function to be modulated. Moreover, the patterning induces a doping effect on the graphene which results in a high barrier at the p-n junction and improves the conductivity in the device operation. The optimum performance is shown at 5 mu m hole size and 30% hole ratio by analyzing the hole size and the area ratio. The proposed structure shows about 20 times higher on-current than a planar transistor with a same active area. Compared to a VTFT using simple graphene working function modulation, the proposed structure has an on-state current that is ten times higher and off-state current that is reduced 50%, and therefore has an improved on-off ratio. © 2021 Wiley-VCH GmbH