Extrinsic Semiconductor
The above are schematic diagrams of extrinsic semiconductors, into which doping agents of Boron(B) and phosphorus(P) have been introduced, respectively. Which of the following statements is correct?
a) Silicon(Si) has valence electrons.
b) Phosphorus(P) has valence electrons.
c) The above left are N-type semiconductors and the above right are P-type semiconductors.
d) Electrons are the majority charge carriers of the above right semiconductors, and holes are the majority charge carriers of the above left semiconductors.
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Silicon being a group 4 element has 4 valence slectrons, hence statement (a) is valid Also in the image given Boron having 3 valence electrons is deficient by 1 electron compared to silicon hence a hole is created for each boron atom as 1 covalent bond is incomplete when born bonds to silicon atoms. On the other hand, phosphorus having 5 valence electrons has 1 extra electron compared to silicon & due to this it provides an excess of electrons to the part of silicon on the right. Therefore statement (d) becomes valid as well.