Question

Which of the following are true for n type semiconductor?

• A. There are doped with 15^th group elements (Arsenic & Phosphorous)
• B. They are doped with 13^th group elements(Boron and Aluminium
• C. They have holes which helps in conduct electricity.
• D. They have free e^- which helps in conduct electricity.

Answer 1

Answer: (A), (D)

The correct options are
A

There are doped with 15^th group elements (Arsenic & Phosphorous)

D

They have free e^- which helps in conduct electricity.

Let’s take the example to explain this If phosphorous (15th group element) (valence electrons are 5) doped into silicon which have4 valence electrons. The 4 electrons of silicon bonds with $4e^{-}$ of phosphorous forming 4 covalent bonds leaving one electron.This helps in conducting electricity.So, semiconductor like silicon when doped with ${15}^{th}$ group elements, it has free electrons which help in conducting electricity and these type of semiconductors are called n-type semiconductors.