Assessment of mobility and its degradation parameters in a shell doped junctionless transistor

Abstract

This work showcases the improvement in the mobility achieved in shell doped (SD) double gate (DG) junctionless (JL) transistors. After analysing the volume and accumulation conduction mechanisms in SD JL devices, it is shown that accumulation mobility (μacc) can be enhanced by ∼three times for a shell depth of 2 nm and a shell doping of 2 × 1019 cm−3 in comparison with a conventional JL transistor with the same doping. A single method is used to extract the mobility and its degradation factors (α and β), and the dependence of both on shell doping and depth is investigated. α and β, attributed to the series resistance and surface roughness scattering of the device, respectively, increases with a decrease in shell depth and doping. Additionally, a modified McLarty function has been used to extract an intrinsic mobility degradation factor (α10(vol)) caused by the gate-dependent bulk conduction in the SD JL transistor. α10(vol), which is independent of the series resistance, increases with shell depth, thus indicating the dominance of Coulomb scattering at higher shell doping. The work provides new viewpoints on conduction mechanisms, mobility and its degradation factors, and the extraction methodology in an SD JL transistor.