Insights into the impact of random dopant fluctuation on ferroelectric germanium source vertical TFET

Abstract

This paper investigates the effect of random dopant fluctuation (RDF) on the performance of ferroelectric Germanium source vertical tunnel field effect transistor (FE GeS-vTFET) using 3-D device simulation. The variation in the on-state current (σION), off-state leakage current (σIOFF), current ratio σ(ION/IOFF), subthreshold swing (σSS), threshold voltage (σVTH), total gate capacitance (σCgg), transconductance (σgm) and cut-off frequency (σfT) for different source doping concentration and source thickness due to the effect of RDF are evaluated. The findings indicate an increasing tendency in RDF with higher doping concentration in the source region. The variation in the on-current is from 0.2173 mA to 0.2337 mA (∼1.075 times higher), and σIOFF varies from 4.939 fA to 16.545 fA (∼3.349 times higher) from 1 × 1020 /cm3 to 3 × 1020 /cm3 doping concentration, respectively for Germanium source thickness of 12 nm. RDF within the source region mainly contributes to the threshold voltage variation of about 92 % in all regions. The randomized dopant-induced σVTH for the FE GeS-vTFET compared with other field effect transistors of the same technology node showed a substantial reduction in σVTH, signifying that the device is more immune to the effects of RDF. Furthermore, the effect of temperature on the switching properties of the FE GeS-vTFET has been studied.