ON THE UNIVERSALITY OF INVERSION LAYER MOBILITY IN SI MOSFETS .1. EFFECTS OF SUBSTRATE IMPURITY CONCENTRATION

This paper reports the studies of the inversion layer mobility in n- a nd p-channel Si MOSFET's with a wide range of substrate impurity conce ntrations (10(15) to 10(18) cm(-3)). The validity and limitations of t he universal relationship between the inversion layer mobility and the effective normal field (E(eff)) are examined. It is found that the un iversality of both the electron and hole mobilities does hold up to 10 (18) cm(-3). The E(eff) dependences of the universal curves are observ ed to differ between electrons and holes, particularly at lower temper atures, This result means a different influence of surface roughness s cattering on the electron and hole transports. On substrates with high er impurity concentrations, the electron and hole mobilities significa ntly deviate from the universal curves at lower surface carrier concen trations 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 e lectron injection.