# Charge Densities in a Semiconductor impurities MCQ’s

This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Charge Densities in a Semiconductor impurities”.

1. Calculate the number of electrons is the number of holes are 15*1010?
a) 15*1010
b) 1.5*108
c) 1.5*109
d) 1.5*1010

2. For which type of material, the number of free electron concentration is equal to the number of donor atoms?
a) P type semiconductor
b) Metal
c) N-type semiconductor
d) Insulator

3. Is n/p=ni2 is a correct formula?
a) True
b) False

4. Identify the correct condition for a semiconductor to be electrically neutral.
a) Nd+p=Na+n
b) Nd-p=Na+n
c) Nd+p=Na-n
d) Nd-p=Na-n

5. Consider a silicon wafer having Nc=2.8*1019cm-3 and the Fermi energy is .25eV below the conduction band. Calculate the equilibrium concentrations of electrons at T=300K?
a) 18*1016cm-3
b) 1.8*1016cm-3
c) 1.8*1014cm-3
d) 180*1016cm-3

6. The 1-fF (E) increases in which of the following band for n type semiconductor?
a) Conduction band
b) Donor band
c) Acceptor band
d) Valence band

7. Do the Fermi energy level changes in a semiconductor?
a) True
b) False

8. If Ef>Efi, then what is the type of the semiconductor?
a) n-type
b) P-type
c) Elemental
d) Compound

9. The fF (E) decreases in which of the following band for p-type semiconductor?
a) Conduction band
b) Donor band
c) Acceptor band
d) Valence band

10. Do the intrinsic Fermi energy level changes with the addition of dopants and acceptors?
a) True
b) False 5 Star
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