How does arsenic doping create an n-type silicon semiconductor?

To create an n-type semiconductor, arsenic is introduced into a pure silicon crystal through a process called doping.

Silicon atoms have four outer electrons, which they share with neighboring atoms to form stable covalent bonds. Arsenic, however, is a pentavalent atom, meaning it possesses five outer electrons. When an arsenic atom replaces a silicon atom in the crystal lattice, four of its electrons participate in covalent bonding with the surrounding silicon atoms.

The fifth electron from the arsenic atom does not participate in these bonds and is instead donated to the conduction band, becoming a free electron available for electrical conduction. Because this process adds negatively charged electrons as the primary charge carriers, the resulting material is classified as n-type (where n stands for negative). In this context, the arsenic atom acts as a donor.1234