Question

A perfect crystal of silicon in the given figure is doped with some elements as given in the options. Which of these options show $n$-type semiconductors?

• A.
• B.
• C.
• D.

Answer 1

Answer: (C), (D)

The $n$-type semiconductor from silicon has to be doped with electron-rich impurities (element having more valence electrons).

As group $14$ element like $Si$ has $4$ valence electrons, therefore, to get an extra electron carrier for the semiconductor, it has to be doped with elements of valency $5$ i.e., group $15$ elements such as $P$ or $As$.

The fifth valence electron of the group $15$ element $(P,As)$ now becomes an extra electron and is free and delocalized. These delocalized electrons enhance the conductivity of doped silicon.




Hence, the options $\left(A\right)$ and $\left(C\right)$ are correct.