What element is commonly used to dope n-type semiconductors?

In the context of semiconductor physics, n-type semiconductors are those which have extra electrons available for conduction. The process of doping involves introducing impurities into a pure semiconductor to alter its electrical properties.

Arsenic is commonly used to dope n-type semiconductors, particularly in silicon. When arsenic, which has five valence electrons, is introduced into silicon (which has four valence electrons), it donates an extra electron. This additional electron becomes available for electrical conduction, thus increasing the semiconductor's conductivity.

The other options mentioned do not serve the same purpose. Silicon is the base material for semiconductors but does not act as a dopant. Gallium is typically used as a p-type dopant due to its three valence electrons, which create "holes" in the structure. Germanium, while it is also a semiconductor material, does not commonly serve as a dopant for n-type semiconductors in the same way arsenic does.