  We present the theoretical analysis of steady state regimes and low-frequency
noises in quasi-ballistic FETs. The noise analysis is based on the Langevin
approach, which accounts for the microscopic sources of fluctuations originated
from intrachannel electron scattering. The general formulas for local
fluctuations of the carrier concentration, velocity and electrostatic potential
as well, as their distributions along the channel are found as functions of
applied voltage/current. Two circuit regimes with stabilized current and
stabilized voltage are considered. The noise intensities for the devices with
different ballisticity are compared. We suggest that the presented analysis
makes better comprehension of physics of electron transport and fluctuations in
quasi-ballistic FETs, improves their theoretical description and can be useful
for device simulation and design.
