Q. When Arsenic atoms are added to Germanium lattice, it becomes a/an:
Answer: Extrinsic semiconductor
Notes: When a pentavalent (donor) impurity, like arsenic, is added to germanium, it will form covalent bonds with the germanium atoms, leaving 1 electron relatively free in the crystal structure. Pure germanium may be converted into an n-type semiconductor by “doping” it with any donor impurity having 5 valence electrons in its outer shell. Semiconductors which are doped in this manner - either with N- or P-type impurities - are referred to as extrinsic semiconductors.

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