In a circuit consisting of a pure silicon crystal with each end attached to a different terminal of a battery via conducting wire, is there a current flowing through the wire? It seems that there is no current flowing through the crystal because the flow of the holes cancels out the flow of the electrons, but is there current flowing through the wire?
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1\$\begingroup\$ Pure silicon is an intrinsic semiconductor. The Fermi level is right between the highest covalent band and the lowest conduction band, which are much closer to each other than in an insulator. If you make point contacts on the crystal with wires, you'll get conduction of both electrons and holes. This conductivity is highly temperature-dependent and it's a "mostly useless" concept -- not to mention how hard it is to fuse or bond copper to a silicon crystal face, should you want to. (Using dissimilar wire makes the question interesting.) \$\endgroup\$– jonkCommented Feb 11, 2020 at 2:32
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2 Answers
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It seems that there is no current flowing through the crystal because the flow of the holes cancels out the flow of the electrons
This premise isn't valid.
If you apply an electric field pointing to the left, then holes will drift to the left (producing a conventional current to the left), and electrons will drift to the right (producing a conventional current to the left).
The hole current and electron current won't cancel out, they'll both be in the same direction.
answered Feb 11, 2020 at 6:35
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Apart from what @jonk rightly points out, pure Si is a very bad conductor - actually is more of an insulator, with an intrinsic resistivity of around \$10^5\$ (src). Still, there will be current flow assuming the battery can handle that load.
