When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called

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In a pure semiconductor, the conductivity is solely due to the thermal excitation of electrons from the valence band to the conduction band, which occurs by the breaking of covalent bonds. Such a semiconductor, without any added impurities, is called an intrinsic semiconductor. Extrinsic semiconductors (p-type and n-type) have their conductivity significantly enhanced by the addition of specific impurities (doping). Answer: intrinsic.