Three-dimensional simulations of ultrasmall metal-oxide-semiconductor field-effect transistors: The role of the discrete impurities on the device terminal characteristics

We present results for the fluctuations in the threshold voltage and electron drift velocity in ultrasmall devices due to different numbers and distribution of impurity atoms in the device active region. We find that fluctuations in the threshold voltage V _T are due to both the actual number and position of the dopant atoms. For the devices being considered, the correlation of the threshold voltage (average drift velocity) to the number of dopant atoms in a 10 nm range at various depths shows that the atoms in the top 15-20 nm (top 8 nm) beneath the channel have the most impact.