Question

If we mix a pentavelent impurity in a crystal lattice of Germanium, what type of semiconductor formation will occur?

• A. n-type semiconductor
• B. p-type semiconductor
• C. Both (A) and (B)
• D. None of these

Answer 1

The correct option is A n-type semiconductor

When an impurity atom with $5$ valence electrons (as arsenic) is introduced in a Germanium crystal, it replaces one of the Germanium atoms. Four of the five valence electrons of the impurity atom forms covalent bonds with the neighbouring Germanium atoms and fifth valence electron becomes free to move in the crystal structure. This free electron acts as a charge carrier. Thus a Germanium crystal which is doped with a pentavalent atom is called n-type semiconductor because in it charge carriers are negative (free electrons).