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The effective density of states (DOS) in the conduction and the valence bands
are expressed by the following theoretical expressions [86]:
represents the number of equivalent energy minima in the conduction band.
Table 3.19:
Parameter values for energy minima in the DOS model
Material 

Material 

Si 
6 
InAs 
1 
Ge 
4 
InP 
1 
GaAs 
1 
GaP 
3 
AlAs 
3 



For an alternative model based on data after
Green [120] is implemented,
which is based on a second order polynomial fit.
Table 3.20:
Parameter values for modeling the effective carrier masses
Material 
[cm] 
[cm] 
[cm] 
[cm] 
[cm] 
[cm] 
Si 
0.14e19 
1.56e19 
1.44e19 
0.17e19 
0.93e19 
2.34e19 

In the model for alloy materials effective carrier masses of the constituents are used
in the expressions (3.91) and (3.92).
In the case of a transition between a direct and an indirect bandgap in IIIV
ternary compounds the valley degeneracy factor is modeled by an
expression equivalent to the one proposed in [157].

(3.94) 
The superscripts and denote direct and indirect, respectively.
In the case of SiGe the splitting of the valley degeneracy due to
strain is modeled accordingly as in [158].

(3.95) 
Here, denotes the energy difference between the valleys shifted
down and up in energy, respectively. It is set equal to 0.6 eV as given in [158].
Next: 3.4 Carrier Mobility
Up: 3.3 BandStructure
Previous: 3.3.4 Effective Carrier Mass
Vassil Palankovski
20010228