Influence of ballistic and pocket effects on electron mobility in Si MOSFETs

Room temperature magnetoresistance of nanometer bulk Si n-type MOSFETs was measured at magnetic fields up to 10 T. The electron magnetoresistance mobility was determined for transistors with the gate length in 30 nm to 1000 nm range and was shown to decrease with decreasing the gate length. We show that the mobility reduction is caused both by the ballistic motion and the pocket effect and that for the strong inversion the influence of both limitations on the mobility is comparable.