Multiple Choice Questions: This Activity Contains 29 Questions

6/13/2020 Multiple Choice Questions
Home Chapter 1: Semiconductor Fundamentals Multiple Choice Questions
Multiple Choice Questions
This activity contains 29 questions.
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:
n-type with carrier concentration of 3 × 1016/cm3
p-type with carrier concentration of 1016/cm3
p-type with carrier concentration of 4 × 1016/cm3
Intrinsic
n-type semiconductors are:
Negatively charged
Produced when Indium is added as an impurity to Germanium
Produced when phosphorous is added as an impurity to silicon
None of the above
The probability that an electron in a metal occupies the Fermi-level, at any

temperature (>0 K) is:
0
1
0.5
None of the above
Measurement of Hall coefficient enables the determination of:
Mobility of charge carriers

Type of conductivity and concentration of charge carriers
Temperature coefficient and thermal conductivity
None of the above
If the energy gap of a semiconductor is 1.1 e V it would be:
Opaque to the visible light

Transparent to the visible light
Transparent to the ultraviolet radiation
None of the above
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The conductivity of an intrinsic semiconductor is given by (symbols have

the usual meanings):
σi = eni2 (µn – µp)

σi = eni (µn – µp)
σi = eni (µn + µp)
None of the above.
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:
1, 2, 3 and 4 are correct
1, 2 and 3 are correct
3 and 4 are correct
None of the above
In an intrinsic semiconductor, the mobility of electrons in the conduction

band is:
Less than the mobility of holes in the valence band
Zero
Greater than the mobility of holes in the valence band
None of the above
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:
~ 1021 m–3
~ 1020 m–3
~ 1022 m–3
None of the above
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.)
Jn = –eDn(∂n/∂x) for electrons
J = –eDp(∂p/∂x) for holes
Jp = –e Dp (∂p/∂x) – eDn (∂n/∂x)
None of the above
If the drift velocity of holes under a field gradient of 100v/m is 5m/s, the
mobility (in the same SI units) is
0.05
0.55
500
None of the above
The Hall Effect voltage in intrinsic silicon is:
Positive
Zero
Negative
None of the above
The Hall coefficient of an intrinsic semiconductor is:
Positive under all conditions

Negative under all conditions
Zero under all conditions
None of the above
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:
1 alone is correct
2 alone is correct
3 alone is correct
None of the above
When ne and nh are electron and hole densities, and µe and µn are the
carrier mobilities, the Hall coefficient is positive when
nh µh > neµe
nh µh2 > neµe2

nhµh < neµh
None of the above
A long specimen of p-type semiconductor material:
Is positively charged
Is electrically neutral
Has an electric field directed along its length
None of the above
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:
n + p = ni + pi
n + ni = p + pi
np = nipi
None of the above
If the temperature of an extrinsic semiconductor is increased so that the

intrinsic carrier concentration is doubled, then:
The majority carrier density doubles
The minority carrier density doubles
Both majority and minority carrier densities double
None of the above
At room temperature, the current in an intrinsic semiconductor is due to
Holes
Electrons
Holes and electrons
None of the above
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:
1,000
2,000
50
None of the above
The mobility is given by (notations have their usual meaning):
µ = V0/E0
µ = V02/E0
µ = V0/E02
None of the above
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:
A direction normal to both current and magnetic field
The direction of current
A direction anti parallel to magnetic field
None of the above
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):
p0.e/µp
µp/p0.e
p0.e.µp
None of the above
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:
3.3 x 1015 and 9.9 x 1013 Hz
3.7 x 1016 and 3.5 x 1014 Hz
6.28 x 1017 and 3.1 x 1013 Hz
None of the above
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:
1016/cm3
107/cm3
1017/cm3
None of the above
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:
n0 = 1.5 x 1016/cm3, p0 = 1.5 x 1012/cm3
n0 = 1.5 x 1010/cm3, p0 = 2.25 x 1015/cm3
n0 = 2.25 x 1017/cm3, p0 = 1.0 x 1014/cm3
None of the above
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
1021/cm3
1010/cm3
1016/cm3
None of the above
A good ohmic contact on a p-type semiconductor chip is formed by

introducing:
Gold as an impurity below the contact
A high concentration of acceptors below the contact
A high concentration of donors below the contact
None of the above
Measurement of Hall coefficient in a semiconductor provides information on

the:
Sign and mass of charge carriers
Mass and concentration of charge carriers
Sign of charge carriers alone
Sign and concentration of charge carriers
Some questions in this exercise may have more than one correct answer. To answer such questions correctly, you
must select all the correct answers.
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6/13/2020 Multiple Choice Questions

Home Chapter 1: Semiconductor Fundamentals Multiple Choice Questions

Multiple Choice Questions

This activity contains 29 questions.

A silicon sample is uniformly doped with 1016 phosphorus atoms/cm3 and 2

n-type semiconductors are:

The probability that an electron in a metal occupies the Fermi-level, at any

Measurement of Hall coefficient enables the determination of:

Mobility of charge carriers

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

Opaque to the visible light

The conductivity of an intrinsic semiconductor is given by (symbols have

σi = eni2 (µn – µp)

Consider the following statements: Compared to Silicon, Gallium Arsenide

In an intrinsic semiconductor, the mobility of electrons in the conduction

The Hall coefficient of sample (A) of a semiconductor is measured at room

In a semiconductor, J, Jp and Jn indicate total diffusion current density hole

The Hall Effect voltage in intrinsic silicon is:

The Hall coefficient of an intrinsic semiconductor is:

Positive under all conditions

nh µh2 > neµe2

A long specimen of p-type semiconductor material:

The electron and hole concentrations in a intrinsic semiconductor are ni and

If the temperature of an extrinsic semiconductor is increased so that the

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

A small concentration of minority carriers is injected into a homogeneous

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

Hall effect is observed in a specimen when it (metal or a semiconductor) is

In a p-type semiconductor, the conductivity due to holes (σp) is equal to (e

None of the above

The difference between the electron and hole Fermi energies of a

A sample of n-type semiconductor has electron density of 6.25 x 1018/cm3

In a p-type silicon sample, the hole concentration is 2.25 x 1015/cm3. If the

A good ohmic contact on a p-type semiconductor chip is formed by

Measurement of Hall coefficient in a semiconductor provides information on

Copyright © 1995 - 2011 Pearson Education . All rights reserved.

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