Impact of doping and channel inhomogeneities on the stability of industrially fabricated WS2 FETs

We report doping-dependent charge trapping in WS2 field-effect transistors fabricated on a 300~mm wafer. In particular, higher n-type doping—associated with smaller channel areas—correlates with an increased density of active defects. This behavior explains the asymmetric threshold voltage degradation observed in large-area ambipolar devices, where the n-branch consistently shifts more than the p-branch under gate bias stress (by a factor of ~3). Through electrical characterization and photoluminescence mapping, we attribute this asymmetry to process-induced inhomogeneities in the WS2 layer and its chemical environment, which lead to enhanced n-type doping at the channel center relative to the edges. The non-uniform doping profile and conduction of the 2D channel are then captured using an equivalent circuit model that quantitatively reproduces the observed degradation asymmetry and corroborates our interpretation. These results have important implications for the development of large-scale 2D semiconductor transistors, highlighting the impact of unintentional process-induced doping and channel heterogeneity on device performance and reliability.