Depletion region in n-type ohmic contact

[PF123]

Hello every one,

Here in below figure we can see an ohmic contact formation between a metal and n-type semiconductor .

Here how the N-type semiconductor bands are banded upward ?
and what type of depletion charge exists there ?

 

[yehokhenan]

electrons will flow into the semiconductor from the metal until enough negative charge has accumulated in the semiconductor to give an electric field strong enough to stop the flow of charge. The electric field comes from the semiconductor having a net negative charge (where before it was neutral). The bands are bent whenever you have a non-zero charge density. Electrons are depleted from the metal and accumulated in the semiconductor.