Investigating the impact of source/drain doping dependent effective masses on the transport characteristics of ballistic Si-nanowire field-effect-transistors
This article studies the impact of doping dependent carrier effective masses of the source/drain regions on transport properties of Si-nanowire field effect transistors within ballistic limit. The difference of carrier effective mass in channel and that in the source/drain regions leads to a misalignment of respective sub-bands and forms non-ideal contacts. Such non-idealities are incorporated by modifying the relevant self-energies which control the effective electronic transport from source to drain through the channel. Non-ideality also arises in the nature of local density of states in the channel due to sub-band misalignment, resulting to a reduction of drain current by almost 50%. The highest values of drain current, leakage current, and their ratio are obtained for the S/D doping concentrations of 3 × 10{sup 20} cm{sup −3}, 8 × 10{sup 20} cm{sup −3}, and 2 × 10{sup 20} cm{sup −3}, respectively, for the nanowire of length 10 nm and diameter of 3 nm. Interestingly, the maximum of sub-threshold swing, minimum of threshold voltage, and the maximum of leakage current are observed to be apparent at the same doping concentration.