Importance of the Collisional Broadening of the States across MOSFET Technology Generations

G. Kannan, D. Vasileska
Arizona State University, US

Keywords: scattering, collisional broadening of the states


There are two assumptions made in the derivation of the Fermi’s Golden Rule: (1) it is assumed that the scattering is infrequent which allows us to impose the long time limit and arrive at the energy conserving delta function, and (2) collision duration time is assumed to be zero, which implies that the intra-collisional field effect is neglected. The assumption (1) basically means that collisional broadening of the states (CBS) is being ignored in many analyses of deep-submicrometer devices. But when is that assumption correct? In this work we investigate the effect of CBS on three different technologies of MOSFET devices with substrate doping densities equal to 1017 cm-3, 1018 cm-3, and 1019 cm-3 (the higher the doping density, the smaller is the device, as high doping density is used to prevent the punch-through effect). We might conclude from the analysis performed that collisional broadening of the states is more significant in smaller device structures due to the Coulomb scattering being increased by two orders of magnitude and interface roughness dominating the intra-subband scattering in this structure at very high doping densities.