Thin-film heterojunction field-effect transistors with multiple subthreshold swings for large-area/flexible electronics and displays

Abstract

This Letter presents a technique for implementing circuits with multiple subthreshold swings. Such circuits are of particular interest to large-area and flexible electronics, including active matrix displays and sensors. In these circuits, devices with large swings may be used for high-precision analogue driving, whereas steep subthreshold devices may be used for fast and low-power switching. This Letter demonstrates that large swings may be obtained by the series connection of diode structures to the source terminals of steep subthreshold devices. In principle, this technique is applicable to a wide range of thin-film transistors, but it is particularly well suited for heterojunction field-effect transistors where the gate heterojunctions may be readily utilised as diodes without altering the fabrication process or increasing the number of mask steps. Implementation of multiple subthreshold swings is demonstrated experimentally and described by a first-order model.