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 $\beta$ and maximum electric field $E_{\text{m}}$ for the first time. Strain and temperature dependences of $\beta$ are investigated on the basis of the change in slope in a universal relation while $E_{\text{m}}$, which is also dependent on strain and temperature, is investigated on the basis of the change in saturation voltage $V_{\text{DSAT}}$. The impact ionization rate is a function of $\beta$ and $E_{\text{m}}$ such that we also evaluated strain and temperature dependence of multiplication factor $M - 1\ (= I_{\text{sub}}/I_{\text{D}})$ to determine the major concern of change in impact ionization rate. The result shows that the change in $E_{\text{m}}$ 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).