Investigation of enhanced impact ionization in uniaxially strained Si n-channel metal oxide semiconductor field effect transistor

The impact ionization rate in uniaxially strained silicon is evaluated from viewpoints of the ionization threshold and maximum electric field Em for the first time. Strain and temperature dependences of β are investigated on the basis of the change in slope in a universal relation while E_m, which is also dependent on strain and temperature, is investigated on the basis of the change in saturation voltage V_DSAT. The impact ionization rate is a function of β and E_m such that we also evaluated strain and temperature dependence of multiplication factor M-1 (= /_sub=/ _D) to determine the major concern of change in impact ionization rate. The result shows that the change in E_m due to the change in potential drop along the channel is the major concern in a uniaxially strained silicon n-channel metal oxide semiconductor field effect transistor (nMOSFET).