sentaurus device related problem, LDMOS selfheating + impact ionisation

Hi all,
i am trying to simulate a LDMOS device which includes self heating and impact ionization effect. The code is same as given in the example section of sentaurus. when only thermodynamic model or only avalanche model is included, it works fine with step size of 1e-6. But when both of them are activated, it's showing convergence problems(even with step size of e-20) and problems like "Temperature is outside of the allowed range". please help to solve it.

May I know about other alternatives about how to activate both selfheating effect and imapct ionization for the LDMOS device given in example section of senaturus work bench?

The code is given as follows, where
*she: Thermode{ { Name="substrate" Temperature=300 SurfaceResistance=5e-4 } } & Physics {Thermodynamic}
*impact ionzn: Avalanche in physics section

File {
Grid= "@tdr@"
Parameters= "@parameter@"
Output= "@log@"
Current= "@plot@"
Plot= "@tdrdat@"
}

Electrode {
{ Name= "drain" Voltage= 0.0 hRecVelocity= 1.93E6 }
{ Name= "gate" Material = "PolySi"(N) Voltage= 0.0 }
{ Name= "source" Voltage= 0.0 hRecVelocity= 1.93E6 }
{ Name= "substrate" Voltage= 0.0}
}

Thermode{ { Name="substrate" Temperature=300 SurfaceResistance=5e-4 } }

Physics {
Thermodynamic
Mobility(
DopingDependence
HighFieldSaturation
Enormal
)
Recombination(
SRH( DopingDependence)
eAvalanche(Eparallel)
hAvalanche(Eparallel)
)
}


Insert= "PlotSection_des.cmd"
Math {
Extrapolate
Notdamped= 50
Iterations= 20
ExitOnFailure
CNormPrint
ErrRef(Electron)= 1e8
ErrRef(Hole) = 1e8
Digits= 5
eMobilityAveraging= ElementEdge
* uses edge mobility instead of element one for electron mobility
hMobilityAveraging= ElementEdge
* uses edge mobility instead of element one for hole mobility
GeometricDistances
* when needed, compute distance to the interface instead of closest
* point on the interface
ParameterInheritance= Flatten
* regions inherit parameters from materials
}

Solve {
*- Creating initial guess:
Coupled(Iterations= 100 LineSearchDamping= 1e-4){ Poisson }

Quasistationary (
Initialstep= 0.01 Increment= 1.35
MaxStep= 0.4 Minstep= 1.e-20
Goal { Name= "gate" Voltage= 11.0}
){ Coupled { Poisson Electron Hole Temperature} }
Save(FilePrefix= "n@node@_Vg6")

Load(FilePrefix= "n@node@_Vg6")
Coupled { Poisson Electron Hole Temperature}
NewCurrentFile= "IdVd_Vg6_"
Quasistationary (
Initialstep= 2.5e-4 Increment= 1.35
Minstep= 1.e-20 MaxStep= 0.05
Goal { Name= "drain" Voltage= 40.0 }
){ Coupled { Poisson Electron Hole Temperature}
CurrentPlot( Time= (Range= (0 1) Intervals= 30) )
}

Plot(FilePrefix= "n@node@_Vg6")

}