What kind of conductor will be formed when 'As' is dopped to 'Ge'?

N-type semiconductor

The answer is 3. N-type semiconductor.

When arsenic (As) is doped to germanium (Ge), a n-type semiconductor is formed.

Arsenic is a pentavalent element, meaning it has five valence electrons. When arsenic is added to germanium, the arsenic atom donates one of its valence electrons to the germanium atom. This creates a free electron in the conduction band of the germanium atom, which can conduct electricity.

In contrast, a p-type semiconductor is formed when a trivalent element, such as gallium (Ga), is doped to germanium. Gallium has three valence electrons, so when it is added to germanium, one of the germanium valence electrons is left without a match. This creates a hole in the valence band of the germanium atom, which can be filled by an electron from a neighboring atom. This process creates a mobile hole, which can conduct electricity.

A superconductor is a material that conducts electricity with zero resistance. Superconductors are formed when materials are cooled to very low temperatures.

An intrinsic semiconductor is a semiconductor that is not doped with impurities. Intrinsic semiconductors have a small but finite conductivity.