Theoretical determination of the temporal and spatial structure of /spl alpha/-particle induced electron-hole pair generation in silicon

Physics-based modeling of the impact ionization process in silicon was performed to determine the time constants and radial distribution of electron-hole pairs after an /spl alpha/-particle strike. The radial distribution exhibited a Gaussian shape with a radius of approximately 50 nm. The impact ionization process took place over a period of less than approximately 500 fsec, implying time constants for use in semiconductor device simulations on the order of a few hundred fsec, a value much smaller than has been used in earlier device simulation work. Device simulations then show that the implication of using these shorter time constants is the creation of a higher concentration of electron-hole pairs at shorter times that cause stronger shunting effects for /spl alpha/-particle strikes between source and drain of MOS transistors.