JEE Questions for Physics Semiconductor Devices Quiz 10 - MCQExams.com

A P-type semiconductor can be obtained by adding
  • Arsenic to pure silicon
  • Gallium to pure silicon
  • Antimony to pure germanium
  • Phosphorous to pure germanium
The valence of an impurity added to germanium crystal in order to convert it into a P-type semiconductor is
  • 6
  • 5
  • 4
  • 3
In a semiconductor, the concentration of electrons is 8 × 1014/cm3 and that of the holes is 5 × 1012cm3. The semiconductor is
  • P-type
  • N-type
  • Intrinsic
  • PNP-type
In P-type semiconductor, there is
  • An excess of one electron
  • Absence of one electron
  • A missing atom
  • A donor level
Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity
  • Decreases
  • Increases
  • Remains unchanged
  • Becomes zero
When the electrical conductivity of a semiconductor is due to the breaking of its covalent bonds, then the semiconductor is said to be
  • Donor
  • Acceptor
  • Intrinsic
  • Extrinsic
A piece of copper and the other of germanium are cooled from the room temperature to 80 K, then which of the following would be a correct statement
  • Resistance of each increases
  • Resistance of each decreases
  • Resistance of copper increases while that of germanium decreases
  • Resistance of copper decreases while that of germanium increases
Suitable impurities are added to a semiconductor depending on its use. This is done to
  • Increase its life
  • Enable it to withstand high voltage
  • Increase its electrical conductivity
  • Increase its electrical resistivity
In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of
  • 1MeV
  • 0.1MeV
  • 1 eV
  • 6eV
Which of the following materials is the best conductor of electricity?
  • Platinum
  • Gold
  • Silicon
  • Copper
If ne and nh represent the number of free electrons and holes respectively in a semiconducting material, then for N-type semiconducting material
  • ne << nh
  • ne >> nh
  • ne = nh
  • ne = nh = 0
Identify the incorrect statement regarding a superconducting wire
  • Transport current flows through its surface
  • Transport current flows through the entire area of cross-section of the wire
  • It exhibits zero electrical resistivity and expels applied magnetic field
  • It is used to produce large magnetic field
Wires P and Q have the same resistance at ordinary (room) temperature. When heated, resistance of P increases and that of Q decreases. We conclude that
  • P and Q are conductors of different materials
  • P is N-type semiconductor and Q is P-type semiconductor
  • P is semiconductor and Q is conductor
  • P is conductor and Q is semiconductor
If the lattice constant of this semiconductor is decreased, then which of the following is correct?
Physics-Semiconductor Devices-87785.png
  • Ec and Ev, increase, but Eg decrease
  • Ec and Ev decrease, but Eg increase
  • All Ec, Eg, Ev decrease
  • All Ec, Eg, Ev increase
In extrinsic P and N-type semiconductor materials, the ratio of the impurity atoms to the pure semiconductor atoms is about
  • 1
  • 10–1
  • 10–4
  • 10–7
A hole in a P-type semiconductor is
  • An excess electron
  • A missing electron
  • A missing atom
  • A donor level
In P-type semiconductor the majority and minority charge carriers are respectively
  • Protons and electrons
  • Electrons and protons
  • Electrons and holes
  • Holes and electrons
Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?
  • The number of free conduction electrons is significant in C but small in Si and Ge
  • The number of free conduction electrons is negligible small in all the three
  • The number of free electrons for conduction is significant in all the three
  • The number of free electrons for conduction is significant only in Si and Ge but small in C
Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added
  • The material obtained will be N-type germanium in which electrons and holes are equal in number
  • The material obtained will be P-type germanium
  • The material obtained will be N-type germanium which has more electrons than holes at room temperature
  • The material obtained will be N-type germanium which has less electrons than holes at room temperature
A semiconductor is cooled from T1K to T2K. Its resistance
  • Will decrease
  • Will increase
  • Will first decrease and increase
  • Will not change
If Np and Ne be the numbers of holes and conduction electrons in an extrinsic semiconductor, then
  • Np > Ne
  • Np = Ne
  • Np < Ne
  • Np > Ne or Np < Ne depending on the nature of impurity
The energy gap between conduction band and the valence band is of the order of 0.7eV. Then, it is
  • An insulator
  • A conductor
  • A semiconductor
  • An alloy
Semiconductor material having fewer free electrons than pure germanium or silicon is
  • p-type
  • n-type
  • Both (a) and (b)
  • None of the above
Fermi level of energy of an intrinsic semiconductor lies
  • In the middle of forbidden gap
  • Below the middle of forbidden gap
  • Above the middle of forbidden gap
  • Outside the forbidden gap
The addition of antimony atoms to a sample of intrinsic germanium transforms it to a material which is
  • Superconductor
  • An insulator
  • N-type semiconductor
  • P-type semiconductor
Electric conduction in semiconductor takes place due to
  • Electrons only
  • Holes only
  • Both electrons and holes
  • None of the above
Energy band diagrams for three semiconductor sample of silicon are as show. We can then assert that
Physics-Semiconductor Devices-87790.png
  • Sample X is undoped while samples Y and Z have been doped with a third group and a fifth group impurity respectively
  • Sample X is undoped while both samples Y and Z have been doped with a fifth group impurity
  • Sample X has been doped with equal amounts third and fifth group impurities while samples Y and Z are undoped
  • Sample X is undoped while samples Y and Z have been doped with a fifth group and a third group impurity respectively
The temperature coefficient of resistance of a semiconductor
  • Is always positive
  • Is always negative
  • Is zero
  • May be positive or negative or zero
P-type semiconductor is formed when
A. As impurity is mixed in Si
B. Al impurity is mixed in Si
C. B impurity is mixed in Ge
D. P impurity is mixed in Ge
  • A and C
  • A and D
  • B and C
  • B and D
In case of a semiconductor, which of the following statement is wrong?
  • Doping increase conductivity
  • Temperature coefficient of resistance is negative
  • Resistivity is in between that of a conductor and insulator
  • At absolute zero temperature, it behave like a conductor
Energy bands in solids are a consequence of
  • Ohm's Law
  • Pauli's exclusion principle
  • Bohr's theory
  • Heisenberg's uncertainty principle
In a P-type semiconductor
  • Current is mainly carried by holes
  • Current is mainly carried by electrons
  • The material is always positively charged
  • Doping is done by pentavalent material
At ordinary temperature, the electrical conductivity of semiconductor in mho/metre is the range
  • 103 to 10–3
  • 106 to 109
  • 10–6 to 10–10
  • 10–10 to 10–16
When the temperature of silicon sample is increased from 27oC to 100oC, the conductivity of silicon will be
  • Increased
  • Decreased
  • Remain same
  • Zero
A light emitting diode (LED) has a voltage drop of 2 volt across it and passes a current of 10 mA when it operates with a 6 volt battery through a limiting resistor R. The value of R is
  • 40 kΩ
  • 4 kΩ
  • 200 Ω
  • 400 Ω
In N-type semiconductors, majority charge carriers are
  • Holes
  • Protons
  • Neutrons
  • Electrons
Semiconductor is damaged by the strong current due to
  • Lack of free electron
  • Excess of electrons
  • Excess of proton
  • None of these
GaAs is
  • Element semiconductor
  • Alloy semiconductor
  • Bad conductor
  • Metallic semiconductor
Which of the energy band diagrams shows in the figure correspond to that of a semiconductor

  • Physics-Semiconductor Devices-87792.png
  • 2)
    Physics-Semiconductor Devices-87793.png

  • Physics-Semiconductor Devices-87794.png

  • Physics-Semiconductor Devices-87795.png
To obtain electrons as majority charge carriers in a semiconductor, the impurity mixed is
  • Monovalent
  • Divalent
  • Trivalent
  • Pentavalent
For germanium crystal, the forbidden energy gap in joules is
  • 1.12 × 10–19
  • 1.76 × 10–19
  • 1.6 × 10–19
  • Zero
In a P-type semiconductor, the acceptor impurity produces an energy level
  • Just below the valence band
  • Just above the conduction band
  • Just below the conduction band
  • Just above the valence band
The mobility of free electron is greater than that of free holes because
  • The carry negative charge
  • They are light
  • They mutually collide less
  • They require low energy to continue their motion
Which of the following energy band diagram shows the N-type semiconductor?

  • Physics-Semiconductor Devices-87797.png
  • 2)
    Physics-Semiconductor Devices-87798.png

  • Physics-Semiconductor Devices-87799.png

  • Physics-Semiconductor Devices-87800.png
The valence band and conduction band of a solid overlap at low temperature, the solid may be
  • A metal
  • A semiconductor
  • An insulator
  • None of these
Which impurity is doped in Si to form N-type semiconductor?
  • Al
  • B
  • As
  • None of these
The process of adding impurities to the pure semiconductor is called
  • Drouping
  • Drooping
  • Doping
  • None of these
Donor type impurity is found in
  • Trivalent elements
  • Pentavalent elements
  • In both (a) and (b)
  • None of these
The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the
  • Variation of scattering mechanism with temperature
  • Crystal structure
  • Variation of the number of charge carriers with temperature
  • Type of bond
Electric current is due to drift of electrons in
  • Metallic conductors
  • Semiconductors
  • Both (a) and (b)
  • None of these
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