Fig. 3: Threshold voltage tuning in 2D FETs via programmable ion migration in LIPS.
From: van der Waals dielectrics for threshold engineering in two-dimensional field effect transistors
a Schematic representing the migration of Li+ ion within the top-gate dielectric layer, e.g., LIPS. The mobile ions occupy intermediate positions within LIPS as the top-gate bias (\({V}_{{TG}}\)) is applied for a finite duration of time. \({E}_{f,m}\) corresponds to the back gate metal Fermi level, \({E}_{C}\) is denoted as the conduction band minima and \({E}_{V}\) corresponds to valence band maxima. b Back-gate transfer characteristics of a MoS2 FET were measured by sweeping back-gate voltage (\({V}_{{BG}}\)) from −1 to 3 V at \({V}_{{DS}}\) =1 V. Tunable back-gate threshold voltage (\({V}_{{th},{BG}}\)) values (0.25–1.5 V) were obtained by programmable and non-volatile ion movement in LIPS, achieved using a \({V}_{{TG}}\) pulse of 8 V pulse with durations from 1 s to 50 s. c The distinct \({V}_{{th},{BG}}\) values showed no detectable drift measured over 150 s, reaffirming the non-volatile retention. Similarly, the back-gate transfer characteristics of a d WSe2 FET were assessed by sweeping the \({V}_{{BG}}\) from −4 V to 0 V at \({V}_{{DS}}\) =1 V. e Four distinct negative \({V}_{{th},{BG}}\) bands (−1.25 V to −2.25 V) were achieved with no noticeable drift over time, confirming the non-volatile retention of the programmed \({V}_{{th},{BG}}\).
