The two Semiconductor Materials

In Retro Style

From Dictionaries of Electronics

A TRIODE is an electron tube with three electrodes namely a cathode, control grid and anode. This was the first amplifying tube and was invented by Lee de Forest in 1905 when he placed a grid in a diode. By suitably biasing the grid¹ with respect to the cathode it is possible to control the density of the electron stream from the cathode which reaches the anode. Thus the grid voltage controls the anode current.

A GRID is an electrode placed between the cathode and the anode of an electron tube and through the interstices of which the main electron stream of the tube passes.

An ELECTRON TUBE is a general term for an evacuated or gas-filled envelope, containing electrodes and in which conduction occurs by virtue of² electrons or ions which move in a controlled manner according to the voltages or currents applied to the electrodes.

CONDUCTIVITY is a term expressing the ability of a material to carry an electric current. The conductivity of metals, for example, is better, i.e. higher than that of non-metals.

Notes to the text

¹ by suitably biasing the grid – соответственно изменяя (букв. смещая) напряжение на сетке

² by virtue of – благодаря

Strange as it may seem¹, but early in this century electric bulbs lasted longer ² than now. The secret is simple – a direct current was used at that time for lighting (освещение). Direct current helped to wear out refractory metal less. This suggested American engineers the idea to return to the old principle but naturally on a modern basis.

They developed a bulb with the filament to which a miniature circuit with a diode was successively hooked up³. This diode converts standard alternating current (AC) into pulsating constant current (DC). The losses of lighting power are compensated by a mirror reflector, installed as close as possible to the spiral bulb, and the bulb's service life has increased 80 times.

Notes to the text

¹ as it may seem – как может показаться

² lasted longer – служили дольше

³ was successively hooked up – был подключен последовательно

The two semiconductor materials used in the manufacture of semiconductor devices, such as diodes and transistors, are germanium and silicon. Both these materials fall into group IV of the Periodic Table of Elements. An atom of either substance may be represented by a central core having a positive charge and surrounded by orbiting electrons, each having a negative charge.

In its solid state silicon forms crystals of the diamond type, i, e. it forms a cubic lattice in which all the atoms 50 except those at the surface are equidistant from their immediately neighbouring^l atoms.

A study of crystal structures shows that the greatest number of atoms that can be neighbours to a particular atom at an equal distance away from that atom and yet be equidistant from one another is four. Hence each atom in a silicon crystal has four neighbouring atoms.

In the crystal lattice each atom employs its four valence electrons to form covalent bonds with its four neighbouring atoms; each bond consists of two electrons, one from each atom. Each pair of electrons orbits around both its parent atom and ² a neighbouring atom.

Notes to the text

¹ immediately neighbouring – находящийся непосредственно рядом

² both … and – как … так и

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