Materials having a conductivity of the order of somewhere between that of conductors and insulators are called semi-conductors. Principal semi-conductor elements are germanium and silicon. These two elements are essentially required for the manufacture of transistors.
Characteristics of semi-conductors
(a) Semi- conductor s has a crystalline structure.
(b) The conductivity of semi-conductors varies in accordance to temperature variations.
(c) The conductivity of semi-conductors is greatly affected by light rays of high intensity, ultra- violet rays and infra-red rays.
Germanium and silicon
The atomic number of germanium is 32; it means it had 32 arbitrary electrons. The order of distribution of electrons in various orbits or germanium is 2, 8, 18, and 4. Similarly the atomic number of silicon is 14 and its order of distribution of electrons in various orbits is 2, 8, and 4. In this way it is evident that both the elements have equal number of valence electrons which is 4. It means that both the elements are tetravalent The electrons of germanium and silicon atoms are bonded in covalent bonds and the number of free electrons is almost nil. Consequently, pure silicon is almost insulators, but their conductivity can be increased by adding impurities of other elements to them. Pure semi-conductors are called intrinsic.
Characteristics of semi-conductors
(a) Semi- conductor s has a crystalline structure.
(b) The conductivity of semi-conductors varies in accordance to temperature variations.
(c) The conductivity of semi-conductors is greatly affected by light rays of high intensity, ultra- violet rays and infra-red rays.
Germanium and silicon
The atomic number of germanium is 32; it means it had 32 arbitrary electrons. The order of distribution of electrons in various orbits or germanium is 2, 8, 18, and 4. Similarly the atomic number of silicon is 14 and its order of distribution of electrons in various orbits is 2, 8, and 4. In this way it is evident that both the elements have equal number of valence electrons which is 4. It means that both the elements are tetravalent The electrons of germanium and silicon atoms are bonded in covalent bonds and the number of free electrons is almost nil. Consequently, pure silicon is almost insulators, but their conductivity can be increased by adding impurities of other elements to them. Pure semi-conductors are called intrinsic.
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