Velocity of surface carriers in inversion layers on silicon

Abstract

Velocity-field curves for surface free-carriers in silicon are determined from measurements on resistivegate IGFETs. The measurements were performed on n-channel devices fabricated on both (100) and (111) substrates and on p-channel devices fabricated on (100) substrates. The channel length of the devices is ∼8 μm and the impurity concentration of the substrates is ∼ 10 15 cm −3. The dependence of velocity on the field strength along the channel is found to be well approximated by an empirical relationship involving three parameters: low-field mobility μ 0, a critical field E cy signalling the onset of velocity saturation, and a parameter α that determines the curvature between the constant-mobility and constant-velocity branches of the curve. The curve-fitting parameters are given in tabular form for the two n-channel and one p-channel systems studied. The dependence of the velocity-field curves on temperatures in the range 100–350K is also reported.