How does doping increase the conductivity of semiconductors? Explain.

In order for a substance to conduct electricity, its valence electrons must cross the band gap, which is the energy gap between the valence band and conduction band. Because the band gap is so small for semiconductors, doping with small amounts of impurities can dramatically increase the conductivity of the material. The process of adding impurity in an intrinsic semiconductor is known as doping. It increases the conductivity of a semiconductor because impurity added increases the charge carriers in the semiconductor. Example: The conductivity of silicon is increased by adding a small amount (of the order of one in 108 ) of pentavalent (antimony, phosphorus, or arsenic) impurity, and this semiconductor is called n -type semiconductors. Here conductivity is due to the extra electron or delocalised electron. The conductivity of silicon can also be increased by adding a trivalent (boron, gallium, indium) atoms, and this semiconductor is called p -type semiconductor. Here conductivity is due to positively charged electron holes.

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because,

All the domains get oriented in the direction of magnetic field

All the domains get oriented in the direction opposite to the direction of magnetic field

Domains are not affected by magnetic field

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter -1 - The Solid State>Gujarat Board-2018>Q 5

MEDIUM

12th Gujarat Board

IMPORTANT

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Which of the following is an example for interstitial solid solution.

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