Q. 8 Carrier concentration of an intrinsic semiconductor can be changed by addin
ID: 475720 • Letter: Q
Question
Q. 8 Carrier concentration of an intrinsic semiconductor can be changed by adding impurity atoms which donate (electrons to the conduction band) or accept electrons from the valence band. They are called donors (Na) and acceptors (Na), respectively. The impurity atom concentration is usually fraction of Si atoms per unit volume (a) If a Si atom is replaced by boron which has 3 outer electrons, does it behave as a donor or acceptor 8(b) What happens if Si atoms are substituted by Phosphorus atoms, does it behave as a donor or acceptor. 8(c) what determines if the donor atom will donate the electrons or not?Explanation / Answer
8a) Silicon has 4 outer electrons or valence electrons, when replaced with Boron which has 3 outer electrons
will end up accepting 4 th electron to bond . Therefore it is indeed an acceptor
8b) Phosphorous has 5 electrons in its outer shell when only 4 electrons are required to bond.
Hence it is a donor.
8c) Number of outer shell electrons and easy ionzation determines the donor atom.
12a) It is for electrons in the conduction band, So equation 14 will be the answer
12b) First equation is Fermi-Dirac (FD) , Second and third equations represent Maxwell -Boltzmann (MB)
and Bose-Einstein relationship respectively.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.