1.41 What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.

<p><strong>1.41 </strong>These solids have conductive in the intermediate range from 10−6 to 104ohm−1m−1. As there is rise in&nbsp;<br>the temperature, conductivity also increases because electrons from the valence band jump to&nbsp;<br>conduction band.<br>Types of semiconductors<br><strong>(a)</strong> n - type semiconductor when silicon or germanium crystal is doped with group 15 element like P or&nbsp;<br>As, the dopant atom forms four covalent bonds like a Si or Ge atom but the fifth electron no used in&nbsp;<br>bonding, becomes delocalised and contribute its share towards electrical conduction. Thus, silicon or&nbsp;<br>germanium doped with P or As is called n-type semiconductor (negative - type).<br><strong>(b)</strong> p - type semiconductor When silicon or germanium is doped with group 13 element like B or Al. The&nbsp;<br>dopant atom forms three covalent bond like a B or Al atom, but at the place of fourth electron a hole is&nbsp;<br>created. Here, this hole moves through the crystal like a positive charge giving rise to electrical&nbsp;<br>conductivity.<br>Thus, Si or Ge doped with B or Al is called p-type of semiconductor, (p stands for positive hole) since, it is&nbsp;<br>the positive hole that is responsible for conduction</p>

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