Fig. 3. Modulation of NDR behavior through contact, gate structure, and Lch.
(A) Transfer characteristics of a representative Ti-contacted CNT-TFT with Lch = 5 μm and Wch = 50 μm. (B) Output characteristics of the CNT-TFT in/around the subthreshold region on a logarithmic scale. (C) Comparison of 2D color plots of output conductance gds for Pd-contacted and Ti-contacted CNT-TFTs. The area outlined with the red dashed line represents the NDR zone of the Pd-contacted CNT-TFT. (D) Schematic band diagrams of Pd- and Ti-contacted devices illustrating the mechanism of contact-dependent NDR behavior. (E) Schematic illustration of CNT-TFTs with air-gap and overlapping gate structures. (F) 2D color plots of output conductance gds for CNT-TFTs with air-gap and overlapping gate structures. The area outlined with the red dashed line represents the NDR zone of the CNT-TFT with overlapping gate structure. (G) Comparison of PVR versus Vgs for CNT-TFTs with different gate structures. (H) Schematic band diagrams of CNT-TFTs with air-gap and overlapping gate structures illustrating the mechanism of gate structure–affected NDR behavior. (I) 2D color plots of output conductance gds for CNT-TFTs with different Lch of 5, 10, and 20 μm. (J) Comparison of NDR window and (K) PVR for CNT-TFTs with different Lch. The subthreshold region is marked with a dashed box in (J). (L) Schematic band diagrams of CNT-TFTs with different Lch illustrating the mechanism of Lch-dependent NDR behavior.