Effect of nonuniform carrier distribution on channel mobility measurement in metal/SiO2/Si field effect transistors

Abstract

The apparent channel mobility of a metal/SiO2/Si field-effect transistor as determined from the current-voltage measurement may yield a significantly underestimated value if proper care is not taken to restrict the applied source-drain voltage. Unlike the well-known velocity saturation effect, the effect to be discussed is due to the nonuniform distribution of carriers along the channel, and therefore is independent of the channel length, but is a function of the ratio of the source-drain voltage to the thermal voltage kT/e. It is more pronounced for devices with thinner gate oxide in the low carrier-concentration regime.