wondering about MOSFET ( second order effect)

[vesperon]

i'm pool at english, just listen TT

second order effect, in mosfet, punch through,
how can flow the 'current' through depletion region??

is that region cannot flow the current, right?
i cant understand why the current flow on punch-through.

avalanche breakdown?

 

[erikl]

second order effect, in mosfet, punch through,
how can flow the 'current' through depletion region??

is that region cannot flow the current, right?
i cant understand why the current flow on punch-through.

Sure current can flow in a depletion region whenever charge carriers are available. A depletion region is only depleted (of charge carriers) if there is no source for new charge carriers. The leakage current through a depletion region consists of charge carriers diffusing into it or being thermally generated in it. Punch-through is given when a depletion region extends to a highly doped region which can inject charge carriers into it. See this excerpt from The Power Electronics Handbook: View attachment punch-through__The_power_electronics_handbook_p66-68.pdf

avalanche breakdown?

This is a different phenomenon. See the PDF above, too.

 

[dick_freebird]

Leakage at the blocking junction is the "seed" for impact
ionization (avalanche at its extreme).

Once you accept that your textbooks are full of assume-away
and for-purposes-of-analytical-simplicity there's a whole world
of nonideal mechanisms to discover.