Assignment I
EE-311
Due by 11 Sep 2022
Q1. (a) If 2 x 1016 boron atoms per cm3 are added to intrinsic silicon as a substitutional impurity,
determine what percentage of the silicon atoms are displaced in the single crystal lattice.
(b) If 2x1016 /cm3 boron atom doped in intrinsic Si what is the concentration of majority and
minority carriers.
2. Assume that Silicon (bandgap 1.12 eV) is at room temperature and that the Fermi level is exactly
at the bandgap's center. Answer the following questions.
(a) What is the possibility that a condition at the bottom of the conduction band is filled?
(b) What is the probability that a state at the top of the valence band is empty?
Q3. How the effective mass of an electron in the conduction band of GaAs is smaller than that in
Silicon. Explain it with the help of E-K diagram.
Q4. Briefly explain the following:
(a) Electrical conduction in solids (use the concept of bond model)
(b) Splitting of energy states into a band of allowed energy (use concept of bonding and
antibonding of orbitals).
Q5. (a) Most commonly used semiconductor is ……….
A. Germanium
B. Silicon
C. Carbon
D. Sulphur
(b) When a pentavalent impurity is added to a pure semiconductor, it becomes ……….
A. An intrinsic semiconductor
B. An insulator
C. p-type semiconductor
D. n-type semiconductor
(c) An n-type semiconductor is ……….
A. Positively charged
B. Negatively charged
C. Electrically neutral
D. None of the above
(c) A trivalent impurity has ………. valence electrons.
A. 4
B. 5
C. 6
D. 3