Abstract:
Two dimensional Poisson-Schrödinger equation is solved numerically in depletion all
around (DAA) operation of n-channel four gate transistor (G4-FET) by finite element
method. Potential distribution is obtained by solving 2-D Poisson equation. The influence
of different gate bias voltages on the location and size of the conducting channel is
studied, which also includes fully depleted condition for certain gate bias voltages. The
developed model is used to investigate the gradual change of the size of the conducting
channel from drain to source, when drain is positively biased. Conduction band profile is
studied and shallow n-well region is found. By solving 2D Schrödinger equation, Eigen
energy at various cross sections between drain and source, subband profiles from source
to drain and wave function distribution are observed. Weak energy quantization is found
by observing small energy difference (less than kT) between subsequent subband profiles
and noticing wave function distribution extending beyond neutral n-well and into the
depletion region. Using the outputs of 2D Poisson-Schrödinger solver, a ballistic currentvoltage
model is developed by mode-space approach and modified Tsu-Esaki equation.
Finally, effect of gate bias on current-voltage characteristics is investigated.
