On the universality of inversion layer mobility in Si MOSFET´s: Part I-effects of substrate impurity concentration

This paper reports the studies of the inversion layer mobility in n- and p-channel Si MOSFET´s with a wide range of substrate impurity concentrations (10¹⁵ to 10¹⁸ cm^-3). The validity and limitations of the universal relationship between the inversion layer mobility and the effective normal field (E_eff) are examined. It is found that the universality of both the electron and hole mobilities does hold up to 10¹⁸ cm ^-3. The E_eff dependences of the universal curves are observed to differ between electrons and holes, particularly at lower temperatures. This result means a different influence of surface roughness scattering on the electron and hole transports. On substrates with higher impurity concentrations, the electron and hole mobilities significantly deviate from the universal curves at lower surface carrier concentrations because of Coulomb scattering by the substrate impurity. Also, the deviation caused by the charged centers at the Si/SiO₂ interface is observed in the mobility of MOSFET´s degraded by Fowler-Nordheim electron injection