Electronic Devices and Circuits

Donor and Acceptor impurities

Question 1
Marks : +2 | -2
Pass Ratio : 100%
The opposite of ionization takes place at which temperature?
0 K
ROOM
300 K
900K
Explanation:
AT 0 K, all the donors and acceptors are in their lowest energy levels.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Valence Band
Conduction Band
Donor Energy level
Acceptor energy level
Explanation:
For n-type semiconductors, the donor energy level is always greater than the Fermi level energy.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
At what temperature the donor states are completely ionized?
0 K
ROOM
300K
900K
Explanation:
At room temperature, the donors have donated their electrons to the conduction band.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
At T=0 K, the location of Fermi level with respect to the Ec and Ed for the n type material is?
Above than conduction band
Midway
Lower than Ed
Greater than Ed
Explanation:
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.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
What do you mean by the tem ‘FREEZE-OUT’?
All the electrons are frozen at room temperature
None of the electrons are thermally elevated to the conduction band
All the electrons are in the conduction band
All the holes are in the valence band
Explanation:
Freeze out means none of the electrons are transmitted to the conduction band.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Which of the following expressions represent the correct formula for the density of electrons occupying the donor level?
nd=Nd-Nd+
nd=Nd-Nd–
nd=Nd+Nd+
nd=Nd+Nd–
Explanation:
The density of the electrons is equal to the electrons present in the substrate minus the number of donors present.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
At absolute zero temperature, which level is above the Fermi energy level in the case of donors?
Donor energy level
Acceptor energy level
Conduction Band
Valence Band
Explanation:
At T=0 K, the tem exp(-∞)=0 in the expression of
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Which of the following band is just above the intrinsic Fermi level for n-type semiconductor?
Donor band
Valence band
Acceptor band
Conduction band
Explanation:
For n-type semiconductors, the donor band is just above the intrinsic Fermi level.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
P type, A-Conduction band, B-donor energy band, C- Valence band
P type, A-Conduction band, B-acceptor energy band, C- Valence band
n type, A-Conduction band, B-donor energy band, C- Valence band
n type, A-Conduction band, B-acceptor energy band, C- Valence band
Explanation:
The given figure has B band below the intrinsic Fermi level, so that would be acceptor energy band and will be a p-type semiconductor.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
At absolute zero temperature, which level is below the Fermi energy level in the case of acceptors?
Donor energy level
Valence Band
Conduction band
Acceptor energy level
Explanation:
At T=0 K, the tem exp(-∞)=0 in the expression of