Next: 3.7.2 Auger Recombination
Up: 3.7 Generation and Recombination
Previous: 3.7 Generation and Recombination
3.7.1 ShockleyReadHall and Surface Recombination
Carrier generation in space charge regions and recombination in e.g. high
injection regions is modeled using the well known ShockleyReadHall
(SRH)
equation

(3.142) 
The auxiliary variables and are defined by
For trap energy level
located in the mid gap and the
recombination rate has its maximum. The variables and are the
carrier effective densities of states (see
Section 3.3). The dependence on the lattice temperature
is given by the variables
and
and the
recombination lifetimes for electrons and holes,
and
. The thermal carrier velocities at 300 K are calculated
using

(3.145) 
to obtain the recombination times at 300 K
The recombination times are modeled using traps of donor, acceptor, or neutral
type, respectively, of trap density
, and the trap capture cross sections
for electrons and holes,
and
.
The effect of surface recombination is included by using nonzero surface
recombination velocities for electrons and holes , respectively.
The effect is stronger with decreasing distance to the surface .
Finally, the temperature dependence is included. The effect of trap assisted
band to band tunneling (TBB) in Si is accounted for by a field enhancement
factors and , which are modeled after [187].
As TBB is of importance only for materials with indirect bandgap this effect is
neglected in literature for technologically important IIIV materials, which
have a direct bandgap (see Section 3.3.1).
The default values recommended for the SRH recombination model are summarized in the
following table:
Table 3.35:
Parameter values for SRH recombination model
Material 
[cm] 
[eV] 
[m] 
[m] 
[m/s] 
[m/s] 
Si, Ge 
1e13 
0.0 
1e15 
1e15 
0.0 
0.0 
IIIVs 
2e16 
0.4 
1e14 
1e13 
0.0 
0.0 

Next: 3.7.2 Auger Recombination
Up: 3.7 Generation and Recombination
Previous: 3.7 Generation and Recombination
Vassil Palankovski
20010228