Question

The electrical conductivity of silicon increases by replacing a fraction of silicon atoms by arsenic atoms. Give appropriate reasons to support the statement.

Answer 1

1.Substances that do not conduct but on heating shows moderate conductivity due to the slightly higher gap between the valence band and the conduction band are called semi-conductors.

2.Semi conductors are of mainly two types - p-type and n-type and n type are those which are formed by doping Silicon(Si) with Phosphorous(P) and Arsenic(As) respectively.

3.On doping Si ( $1s^{2}2s^{2}2p^{6}3s^{2}3p^2$) with small amount of As ( $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^3$) there is an extra electron after bonding with $4$ electrons which moves freely and conducts electricity.

Hence, Silicon conductance increases on adding a small amount of Arsenic as it forms an n-type semiconductor.