Question

Question: - A semimetal (e.g., antimony, bismuth) is a material in which electrons would fill states to the top of a band the valence band--except for the fact that the top of this band overlaps very slightly with the bottom of the next higher band. Explain why such a material, unlike the "real" metal copper, will have true positive charge carriers and equal numbers of negative ones, even at zero temperature.

Short answer

Answer: -

Semimetals will have true positive charge carriers and equal numbers of negative ones at zero temperature.

Step-by-step solution

Explanation

Because the semimetal's top of the valence band is slightly overlapped with the conducting band, the electrons will move from the top of the valence band to the bottom of the conducting band and leave holes in the top of the valence band. Thus, semimetals have both holes and electrons as charge carriers. The number of electrons reaching the conduction band is equal to the holes formed in the valance band.

Hence, semimetals will have true positive charge carriers and equal numbers of negative ones at zero temperature.