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-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-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 beta and E-m such that we also evaluated strain and temperature dependence of multiplication factor M - 1 (= I-sub/I-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). (C) 2010 The Japan Society of Applied Physics