Cascade Model for Reduction of Field-Effect Mobility of Electrons in Lightly Doped Channel of Submicron Gate Si Thin-Film Field-Effect Transistors

Publisher Website
Google Scholar
Abstract
Polycrystalline silicon accumulation-type thin-film field-effect transistors (TFTs), whose channel lengths range from 20 µm to 0.3 µm, have been fabricated, and reduction of the field-effect mobility of electrons has been observed in the lightly doped channel of submicron-gate TFTs. This phenomenon was well understood by assuming the diffusion of donor ions from the source and the drain to the channel which raised the barrier height between polycrystalline Si grains near the source and the drain. A model for device performance was built by cascading two Si TFTs with different channel doping levels. Considering that the shape of the depletion region on the surface of polycrystalline Si grains in channels is modulated by the gate voltage, the drain current-voltage characteristics were calculated, and found to be in good agreement with the experimental results.