The effect of trapped charge on silicon nanowire pseudo-MOSFETs

The effects of organic molecules grafted on top of silicon nanowires are modeled as the oxide trap charges (Q_ot) and interface trap charges (Q_it). The device investigated here is a pseudo-MOSFET with a thick bottom oxide (200 nm) and only a thin native oxide (5 nm) on top. With Q _ot = -5.0 × 10¹¹ cm^-2 and the U-shaped distribution of interface trap density (D_it) as a function of trap energy (E_t), the structures are reproduced through the conventional technology computer aided design (TCAD) simulation tool, and the channel is imaginarily divided into several sections (5 × 5 regions) to apply the localized traps. The electrical parameters are extracted from the each part to quantitatively compare their effectiveness. The local position of the grafted molecules, modeled by these charges, is shown to result in strong variations in the relative change in the threshold voltage and subthreshold swing. These variations are explained by the surface depletion and scattering near the edges of the etched device and the series resistance effect.