Electronic Devices and Circuits Multiple Choice Questions on “Donor and Acceptor impurities”.
1. At what temperature the donor states are completely ionized?
A. 0 K
B. ROOM
C. 300K
D. 900K
Answer: B
Clarification: At room temperature, the donors have donated their electrons to the conduction banC.
2. The opposite of ionization takes place at which temperature?
A. 0 K
B. ROOM
C. 300 K
D. 900K
Answer: A
Clarification: AT 0 K, all the donors and acceptors are in their lowest energy levels.
3. What do you mean by the tem ‘FREEZE-OUT’?
A. All the electrons are frozen at room temperature
B. None of the electrons are thermally elevated to the conduction band
C. All the electrons are in the conduction band
D. All the holes are in the valence band
Answer: B
Clarification: Freeze out means none of the electrons are transmitted to the conduction banC.
4. Which of the following expressions represent the correct formula for the density of electrons occupying the donor level?
A. nd=Nd-Nd+
B. nd=Nd-Nd–
C. nd=Nd+Nd+
D. nd=Nd+Nd–
Answer: A
Clarification: The density of the electrons is equal to the electrons present in the substrate minus the number of donors present.
5. Which of the following band is just above the intrinsic Fermi level for n-type semiconductor?
A. Donor band
B. Valence band
C. Acceptor band
D. Conduction band
Answer: A
Clarification: For n-type semiconductors, the donor band is just above the intrinsic Fermi level.
6. At absolute zero temperature, which level is above the Fermi energy level in the case of donors?
A. Donor energy level
B. Acceptor energy level
C. Conduction Band
D. Valence Band
7. At T=0 K, the location of Fermi level with respect to the Ec and Ed for the n type material is?
A. Above than conduction band
B. Midway
C. Lower than Ed
D. Greater than Ed
Answer: B
Clarification: At T=0 K, the Fermi level of n band lies between the midway of Ec and Ed as intrinsic Fermi level always lies between the Ec and Ev.
8. At absolute zero temperature, which level is below the Fermi energy level in the case of acceptors?
A. Donor energy level
B. Valence Band
C. Conduction band
D. Acceptor energy level