Question

Name the refining method used to produce semiconductors.

Answer 1

Hint: The process of purification of a substance that is usually unusable in its natural form but usable in its pure form is known as refining. It can be used to extract metals from its ore, fuels from natural petroleum, or purify crystals to prepare semiconductors.

Complete step-by-step answer:Semiconductors are materials whose electrical conductivity has a value in between that of an insulator like glass or rubber and a conductor like metallic copper.
Some pure elements which show semiconductor properties are germanium (Ge), silicon (Si), tin (Sn), tellurium (Te), selenium (Se), and gallium (Ga).
Compounds containing multiple elements which show semiconductor properties are gallium arsenide (GaAs), mercury indium telluride ($HgI{{n}_{2}}T{{e}_{4}}$), aluminum gallium arsenide ($A{{l}_{x}}G{{a}_{1-x}}As$), etc.
To utilize a compound or an element as a semiconductor, it must be in its purest form.
The purest form of an element can be obtained using the zone refining method. It is also known as the traveling-melting zone, floating-zone process, or zone melting.
Zone refining uses processes like melting and crystallization to obtain high purity metals.
We know that often in a molten state, impurity is more soluble. Upon cooling, the impurities are removed from the molten metal and do not crystalize giving a pure crystal.
During the zone refining process, an impure metal rod slowly is moved through a mobile circular heater in an inert gas column. Both the metal and the impurities melt but the impurities move along with the heater and are removed and collected at one end whereas the pure metal recrystallizes and gives a pure solid metal at the other end.
Hence semiconductors like germanium (Ge), silicon (Si), and gallium (Ga) can be refined and purified using the zone refining method.

Note: It should be noted that even though zone refining is an excellent refining method, it can be an expensive process and hence is only used for valuable chemicals and laboratory reagents. Also, other techniques can be combined with zone refining to produce ultrahigh purity metal when the liquid-solid equilibria are unfavorable for all impurities.