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Home  arrow Chapter 1: Semiconductor Fundamentals  arrow Multiple Choice Questions

Multiple Choice Questions



This activity contains 29 questions.

Question 1.
A silicon sample is uniformly doped with 1016 phosphorus atoms/cm3 and 2 × 1016 boron atoms/cm3. If all the dopants are fully ionized, the material is:

 
End of Question 1


Question 2.
n-type semiconductors are:

 
End of Question 2


Question 3.
The probability that an electron in a metal occupies the Fermi-level, at any temperature (>0 K) is:

 
End of Question 3


Question 4.
Measurement of Hall coefficient enables the determination of:

 
End of Question 4


Question 5.
If the energy gap of a semiconductor is 1.1 e V it would be:

 
End of Question 5


Question 6.
The conductivity of an intrinsic semiconductor is given by (symbols have the usual meanings):

 
End of Question 6


Question 7.

Consider the following statements: Compared to Silicon, Gallium Arsenide (GaAs) has:
1. Higher signal speed since electron mobility is higher
2. Poorer crystal quality since stoichiometric growth difficult
3. Easier to grow crystals since the vapor pressure Arsenic is high
4. Higher optoelectronic conversion efficiency

Of these statements:
 
End of Question 7


Question 8.
In an intrinsic semiconductor, the mobility of electrons in the conduction band is:

 
End of Question 8


Question 9.
The Hall coefficient of sample (A) of a semiconductor is measured at room temperature. The Hall coefficient of (A) at room temperature is 4×10–4 m3 coulomb–1. The carrier concentration in sample A at room temperature is:

 
End of Question 9


Question 10.

In a semiconductor, J, Jp and Jn indicate total diffusion current density hole current density and electron current density respectively, ∂n/∂x and ∂p/∂x are the electron and hole concentration gradient respectively in x-direc­tion and Dp and Dn are the hole and electron diffusion constants respectively. Which one of the following equations is correct? (e denotes charge of electron.)
 
End of Question 10


Question 11.
If the drift velocity of holes under a field gradient of 100v/m is 5m/s, the mobility (in the same SI units) is

 
End of Question 11


Question 12.
The Hall Effect voltage in intrinsic silicon is:

 
End of Question 12


Question 13.
The Hall coefficient of an intrinsic semiconductor is:

 
End of Question 13


Question 14.
Consider the following statements: pure germanium and pure silicon are examples of:
1. Direct band-gap semiconductors
2. Indirect band-gap semiconductors
3. Degenerate semiconductors
Of these statements:

 
End of Question 14


Question 15.
When ne and nh are electron and hole densities, and µe and µn are the carrier mobilities, the Hall coefficient is positive when

 
End of Question 15


Question 16.
A long specimen of p-type semiconductor material:

 
End of Question 16


Question 17.
The electron and hole concentrations in a intrinsic semiconductor are ni and pi respectively. When doped with a p-type material, these change to n and p, respectively. Then:

 
End of Question 17


Question 18.
If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then:

 
End of Question 18


Question 19.
At room temperature, the current in an intrinsic semiconductor is due to

 
End of Question 19


Question 20.
A small concentration of minority carriers is injected into a homogeneous semiconductor crystal at one point. An electric field of 10 V.cm is applied across the crystal and this moves the minority carriers a distance of 1 cm is 20 µsec. The mobility (in cm2/volt.sec) is:

 
End of Question 20


Question 21.
The mobility is given by (notations have their usual meaning):

 
End of Question 21


Question 22.
Hall effect is observed in a specimen when it (metal or a semiconductor) is carrying current and is placed in a magnetic field. The resultant electric field inside the specimen will be in:

 
End of Question 22


Question 23.
In a p-type semiconductor, the conductivity due to holes (σp) is equal to (e is the charge of hole, µp is the hole mobility, p0 is the hole concentration):

 
End of Question 23


Question 24.
The difference between the electron and hole Fermi energies of a semiconductor laser is 1.5eV and the band gap of the semiconductor is 1.43eV. The upper and lower frequency limits of the laser will be respectively:

 
End of Question 24


Question 25.
A sample of n-type semiconductor has electron density of 6.25 x 1018/cm3 at 300K. If the intrinsic concentration of carriers in this sample is 2.5 x 1013/cm3, at this temperature, the hole density becomes:

 
End of Question 25


Question 26.
The intrinsic carrier density at 300K is 1.5 x 1010/cm3 in silicon. For n-type silicon doped to 2.25 x 1015 atoms/cm3, the equilibrium electron and hole densities are:

 
End of Question 26


Question 27.
In a p-type silicon sample, the hole concentration is 2.25 x 1015/cm3. If the intrinsic carrier concentration 1.5 x 1010/cm3, the electron concentration is

 
End of Question 27


Question 28.
A good ohmic contact on a p-type semiconductor chip is formed by introducing:

 
End of Question 28


Question 29.
Measurement of Hall coefficient in a semiconductor provides information on the:

 
End of Question 29





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