Metals, Semiconductors, and Insulators
Every solid has its own characteristic energy band structure. In order for a material to be conductive, both free electrons and empty states must be available.
Metals have free electrons and partially filled valence bands, therefore they are highly conductive (a).
Semimetals have their highest band filled. This filled band, however, overlaps with the next higher band, therefore they are conductive but with slightly higher resistivity than normal metals (b).
Examples: arsenic, bismuth, and antimony.
Insulators have filled valence bands and empty conduction bands, separated by a large band gap E g(typically >4eV), they have high resistivity (c ).
Semiconductors have similar band structure as insulators but with a much smaller band gap. Some electrons can jump to the empty conduction band by thermal or optical excitation (d). E g=1.1 eV for Si, 0.67 eV for Ge and 1.43 eV for GaAs
To continue reading click on the link below:
http://pees.etf.ukim.edu.mk/predmeti/elmat/literatura/UPRM/EME4-2.pdf
Metals have free electrons and partially filled valence bands, therefore they are highly conductive (a).
Semimetals have their highest band filled. This filled band, however, overlaps with the next higher band, therefore they are conductive but with slightly higher resistivity than normal metals (b).
Examples: arsenic, bismuth, and antimony.
Insulators have filled valence bands and empty conduction bands, separated by a large band gap E g(typically >4eV), they have high resistivity (c ).
Semiconductors have similar band structure as insulators but with a much smaller band gap. Some electrons can jump to the empty conduction band by thermal or optical excitation (d). E g=1.1 eV for Si, 0.67 eV for Ge and 1.43 eV for GaAs
To continue reading click on the link below:
http://pees.etf.ukim.edu.mk/predmeti/elmat/literatura/UPRM/EME4-2.pdf
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