On the Mobility Behavior in Highly Doped Junctionless Nanowire SOI MOSFETs

Abstract

The electron mobility in highly-doped junctionless (JL) nanowire (NW) silicon-on-isulator (SOI) MOSFETs with various nanowire widths is experimentally studied and analyzed. The evidence for the considerable enhancement of the effective electron mobility in narrow NW devices as compared to counterpart planar (wide) devices, having the same film thickness and doping, and as compared to the bulk silicon mobility with the same doping is presented. This mobility enhancement increases with decreasing the NW width. The reason for this effect is considered to be reduction of the impurity Coulomb scattering in narrow NW MOSFETs due to: (i) the reduced depletion-layer width; (ii) stronger screening of ionized impurities; (iii) the reduced number of neighbor ionized doping atoms per each free carrier in very narrow NWs. These results are of great importance since mobility degradation due to high doping was considered to be one of the most important limitations of the JL NW MOSFETs.