Negative differential transconductance effects on anomalous n-type characteristics in p-type WSe2 semiconductor field effect transistors

Abstract

The negative differential transconductance (NDT) effect has recently attracted attention due to its possible application in multi-valued logic (MVL) devices. However, current research is based on the stacked van der Waals heterojunctions composed of two materials to realize a single-peak NDT effect. Complex transistor structures and low electrical performance limit practical applications in MVL devices. In this study, the NDT effect with a high peak current is demonstrated in a simple structured WSe₂ field effect transistor. After oxygen plasma treatment, the upper layer WSe₂ changes into WO_3−x. The NDT effect is observed at gate voltage sweeps from negative to positive values, and is attributed to the competition of two factors. On the one hand, the slow oxygen migration in the top layer WO_3−x leads to a continuous increase of carriers in the channel. On the other hand, the reduction of electrical field induced by gate voltage leads to a decrease of the carrier concentration in the channel. It is the competition that leads to the emergence of the NDT phenomenon and a high peak current (∼200 μA). In a word, we realize a high peak current NDT effect in a transistor with easy-to-prepare structures. This study paves the way for achieving enhanced signal resolution in MVL devices.