Semiconductors are a large group of materials used in radio engineering (germanium, silicon, selenium, copper oxide). In terms of their electrical properties, semiconductors occupy an intermediate position between conductors and non-conductors of electric current.
In radio electronics, the term "semiconductors" often refers not to the materials themselves, but to semiconductor devices such as diodes, thyristors, transistors, and varicaps. For the manufacture of semiconductor devices, mainly silicon (Si) and germanium (Ge) are used.
Electron-hole conductivity
At temperatures close to absolute zero, a semiconductor does not conduct current because it has no free electrons. However, as the temperature increases, the bond between valence electrons and atomic nuclei weakens, and some electrons, due to thermal motion, can escape from their atoms. An electron that has broken free from an atomic bond becomes “free,” and the place it occupied becomes a vacancy called a hole. Both holes and electrons conduct electric current.
The higher the temperature of a semiconductor, the greater the number of free electrons and holes it contains. The formation of a hole is always associated with the departure of a valence electron from the atomic shell, and the hole itself is considered a positive electric charge equal in magnitude to the negative charge of the electron.
By adding impurities to a semiconductor, it is possible to give it predominantly electron or hole conductivity. Based on this, the following semiconductor types are obtained: semiconductors with electron conductivity are called n-type (negative), and those with hole conductivity are called p-type (positive).
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