Question

A p-type Si semiconductor is made by doping an average of one dopant atom per 5 × 10⁷ silicon atoms. If the number density of silicon atoms in the specimen is 5 × 10²⁸ atoms m⁻³, find the number of holes created per cubic centimetre in the specimen due to doping. Also give one example of such dopants.

Answer 1

Number density of atoms in Si,

= 5 × 10²⁸ atoms m⁻³

= 5 × 10²² atoms cm⁻³

Since 1 atom of dopant is doped in 5 × 10⁷ silicon atoms,

∴ Total number of dopant atoms,

= `(5 xx 10^22)/(5 xx 10^7)`

= 1 × 10¹⁵ atoms cm⁻³

Each dopant atom forms a hole in a p-type semiconductor, resulting in a total of 1 × 10¹⁵ holes per cubic centimetre.

Boron (B) is a common dopant used in the production of p-type semiconductors.