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

Material Properties for Heterostructures
1 2 x ε 1 – 1
------------- ( 1 – x) ε 2 – 1
+ + -------------
ε
ε
1 + 2 ε 2 + 2
= ------------------------------------------------------------------------
1 x ε 1 – 1
– ------------- ( 1 – x) ε 2 – 1
– -------------
ε 1 + 2 ε 2 + 2
(4.21)
where ε 1
is that of AlAs for both the materials, and ε 2
is that of GaAs for AlGaAs and of InAs for
AlInAs. The formulation applies to both high and low frequencies.
The dielectric constants for Ge x Si 1-x are obtained by using the linear interpolation for those
of Ge and Si. For the quaternary Ga x In 1-x As y P 1-y , the interpolation scheme in Eq. (4.18) is used based
on the data for the constituent binaries.
4.6 Mobilities
Due to the lack of experimental data, the mobility dependences on composition, doping, lattice
temperature, and field are not complete for most of the compound materials. Whenever data are not
available constant mobility as listed in Section 3.1.1.1 is used. Readers are referred to [29] for data for
many other materials, even though the collection of data is rather out-of-date (1971).
4.7 Impact Ionization
For relevant formulas and material parameters, see Section 3.3.1.1.
PISCES-2ET – 2D Device Simulation for Si and Heterostructures 41