PISCES-2ET and Its Application Subsystems - Stanford Technology ...

CHAPTER 3
Physical Models
3.1 Mobility Models
Carrier mobility is one of the most important parameters in the carrier transport model. In PISCES-
2ET, the mobility is, for most cases, modeled as the function of the total doping density, N, lattice
temperature, T L , surface/interface scattering mechanisms which are generally modeled using the
dependence on the transverse electric field to the surface/interface, and the electric field along the
current path (longitudinal field). When the device size is in the submicron regime, however, the local,
longitudinal field dependence may not be accurate enough and non-local effects, which is mainly
characterized by the carrier temperature dependence, have to be taken into consideration. The
following expression describes in a general way the carrier mobility dependence on various factors:
µ ( N, T L , E ⊥ , E || /T c ) = f ( µ 0 ( N, T L , E ⊥ ),
E || /T c )
(3.1)
where E || and E ⊥ are the longitudinal and transverse components of the electric field with respect to
(w.r.t) the current direction, µ 0
, which depends on N, T L
, and E ⊥ , is called the low field mobility
because when E || → 0 , µ → µ 0 , T c
is the carrier temperature with the subscript c representing either
n or p for electrons and holes, respectively, and the symbol E || ⁄ T c indicates the dependency is either
on E || or on T c but not on both. In some models such as ones developed by Intel, the above expression
is simplified to the following form to separate mobility reductions due to different field components:
PISCES-2ET – 2D Device Simulation for Si and Heterostructures 13