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What is a semiconductor?
A semiconductor is a solid whose electricalconductivity is in between that of a conductor and that of aninsulator, and can be controlled over a wide range, eitherpermanently… or dynamically. Semiconductor materials can be elements (e.g. germanium, silicon),compounds (e.g. copper oxide, lead sulfide), or metal alloys (e.g.gallium arsenide, gallium aluminum indium phosphide). A pure semiconductor material is a very poor conductor or even aninsulator, but when impurities called dopants are added it canbecome a quite good conductor. There are two classes of dopants: N type and P type . N type dopants createnegatively charged current carriers (i.e. free electrons )in the semiconductor, just like ordinary conductors use. P typedopants create positively charged current carriers (i.e. holes ) in the semiconductor. (Note: dopants do no make thesemiconductor material electrically charged.) Becausesemiconductors have two different types of current carrier (notjust the one that ordinary conductors have), it is possible tocreate junctions between differently doped parts of semiconductormaterial that conduct in one direction but not the other, or due toquantum mechanical effects do other useful things. Semiconductor is a material that has the electrical conductivitybetween that of a conductor and an insulator. Silicon, germaniumand graphite are some examples of semiconductors. Source : Physics and Radio-Electronics ( website) (MORE)
