Question

Why impurity doped silicon is a semiconductor?

Answer 1

Si has four valence electrons. When it's doped with an impurity Group-15 element such as P or As which have five valence electrons, 4 out of 5 electrons are used to form covalent bonds and the remaining 5th electron becomes delocalized and increases the conductivity of the doped Si.

Answer 2

Answer:

The electrical conductivity of an intrinsic semiconductor is very low at room temperature. This makes it unsuitable for the fabrication of electronic devices. When the impurities are added in a semiconductor crystal, the number of free electrons or holes is increased. Thus, by adding suitable impurities, the electric conductivity of an intrinsic semiconductor is increased considerably. ..