N-Type Semiconductors – revision notes
N-type semiconductors are obtained by adding pentavalent impurities (Bismuth, Antimony, Arsenic, and Phosphorous) to a pure semiconductor.
The four valence electrons of the impurity atom form covalent bonds with four neighboring semiconductor atoms and the filth electron is free to move in the crystal.
Thus the addition of pentavalent impurity atom provides free electrons to the semiconductor.
The pentavalent impurities which produce N-type semiconductors are known as donor impurities because they donate or provide free electrons to the semiconductor crystal.
In an N-type semiconductor, a large number of free electrons are created by doping which improves its conductivity. But there will be a very small amount of free holes created because of thermal agitation.
Free electrons are much more in number and so they can be termed as majority carriers and holes are comparatively much less and hence they can be termed as the minority carriers. Therefore in N-type semiconductor electrons are the majority charge carriers and holes are the minority charge carriers.
