non convergence beyond 0.8v

[tara]

Dear Quantum Staff:

i simulated a p-i-n Fet ,which got converged (slater Koster calculation used) for drain bias of  0 to 0.8 v  ,with gate bias of 2v (for id-vd characteristics). i saw your newly published tutorial on convergence tricks, but beyond a drain bias of 0.8 v  , nothing seems to converge slater Koster calculation for my structure . i want to  sweep my drain bias upto 2v and see what currents i am getting for that.

 i am attaching the two scripts i used for my device .What could be the possible reason for non convergence in my structure  and what other changes could be made to converge my calculation upto drain  bias of 2v(with gate bias of 2v)

[Anders Blom]

A general problem in your calculation is that the Si surface is not passivated, so there will be a lot of dangling bonds that give an incorrect electronic structure.

I would also use a Neumann condition on the vacuum side.

Can't say if this helps your specific problem, but they should be addressed, else results might not be correct.