JEE Questions for Physics Semiconductor Devices Quiz 17 - MCQExams.com

Which statement is correct?
  • N—type germanium is negatively charged and P—type germanium is positively charged
  • Both N—type and P—type germanium are neutral
  • N—type germanium is positively charged and P—type germanium is negatively charged
  • Both N—type and P—type germanium are negatively charged
Let np and ne be the number of holes and conduction electrons respectively in a semiconductor. Then,
  • np> ne in an intrinsic semiconductor
  • np = ne in an extrinsic semiconductor
  • np = ne in an intrinsic semiconductor
  • np> ne in an intrinsic semiconductor
Which one of the following statements is false?
  • The resistance of intrinsic semiconductor decreases with increase of temperature
  • Pure Si doped with trivalent impurities gives a p—type semiconductor
  • Majority carriers in a n-type semiconductor are holes
  • Minority carries in a p-type semiconductor are electrons
In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is
Physics-Semiconductor Devices-88200.png
  • A p–type semiconductor
  • An insulator
  • A metal
  • An n–type semiconductor
In a semiconducting material the mobilities of electrons and holes are μe and μh respectively. Which of the following is true?
  • μe> μh
  • μe< μh
  • μe = μh
  • μe< 0; μh> 0
The addition of antimony atoms to a sample of intrinsicgermanium transforms it to a material which is
  • Superconductor
  • An insulator
  • N–type semiconductor
  • P–type semiconductor
A semiconductor dropped with a donor impurity is
  • P–type
  • N–type
  • NPN type
  • PNP type
The impurity atom added to germanium to make it N–type semiconductor is
  • Arsenic
  • Iridium
  • Aluminium
  • Iodine
When N–type of semiconductor is heated
  • Number of electrons increases while that of holesdecreases
  • Number of holes increases while that of electronsdecreases
  • Number of electrons and holes remains same
  • Number of electrons and holes increase equally
Gas is
  • Element semiconductor
  • Alloy semiconductor
  • Bad conductor
  • Metallic semiconductor
If ne and nh are the number of electrons and holes in a semiconductor heavily doped with phosphorus, then
  • ne>>nh
  • ne
  • ne ≤nh
  • ne=nh
An N–type and P–type silicon can be obtained by dopingpure silicon with
  • Arsenic and Phosphorous
  • Indium and Aluminum
  • Phosphorous and Indium
  • Aluminum and Boron
The state of the energy gained by valance electrons when the temperature is raised or when electric field isapplied is called as
  • Valance band
  • Conduction band
  • Forbidden band
  • None of these
A pure semiconductor behaves slightly as a conductorat
  • Room temperature
  • Low temperature
  • High temperature
  • Both (b) and (c)
The band gap in germanium and silicon in eV respectively is
  • 0.7, 1.1
  • 1.1, 0.7
  • 1.1, 0
  • 0, 1.1
At room temperature, a P-type semiconductor has
  • Large number of holes and few electrons
  • Large number of free electrons and few holes
  • Equal number of free electrons and holes
  • No electrons or holes
In a semiconductor
  • There are no free electrons at any temperature
  • The number of free electrons is more than that in a conductor
  • There are no free electrons at 0 K
  • None of the above
When phosphorus and antimony are mixed ingermanium, then
  • P–type semiconductor is formed
  • N–type semiconductor is formed
  • Both (a) and (b)
  • None of the above
The energy gap of silicon is 1.14 eV. The maximum wavelength at which silicon will begin absorbingenergy is
  • 10888 Å
  • 1088.8 Å
  • 108.88 Å
  • 10.888 Å
The charge on a hole is equal to the charge of
  • Zero
  • Proton
  • Neutron
  • Electron
When germanium is doped with phosphorus, the dopedmaterial has
  • Excess positive charge
  • Excess negative charge
  • More negative current carriers
  • More positive current carriers
A Ge specimen is doped with Al. The concentration of acceptor atoms is ~1021 atoms/m3. Given that the intrinsic concentration of electron hole pairs is ~1019 / m3, the concentration of electrons in thespecimen is
  • 1017/m3
  • 1015 / m3
  • 104 / m3
  • 102 / m3
Which of the following has negative temperature coefficient of resistance?
  • Copper
  • Aluminum
  • Iron
  • Germanium
In semiconductors at a room temperature
  • The valence band is partially empty and the conduction band is partially filled
  • The valence band is completely filled and the conduction band is partially filled
  • The valence band is completely filled
  • The conduction band is completely empty
Regarding a semiconductor which one of the following is wrong?
  • There are no free electrons at room temperature
  • There are no free electrons at 0 K
  • The number of free electrons increases with rise of temperature
  • The charge carriers are electrons and holes
Which of the following statements is true for an N–type semiconductor?
  • The donor level lies closely below the bottom of the conduction band
  • The donor level lies closely above the top of the valence band
  • The donor level lies at the halfway mark of the forbidden energy gap
  • None of the above
In a P–type semiconductor, germanium is dopped with
  • Gallium
  • Boron
  • Aluminum
  • All of these
A piece of semiconductor is connected in series in an electric circuit. On increasing the temperature, thecurrent in the circuit will
  • Decrease
  • Remain unchanged
  • Increase
  • Stop flowing
Resistivity of a semiconductor depends on
  • Shape of semiconductor
  • Atomic nature of semiconductor
  • Length of semiconductor
  • Shape and atomic nature of semiconductor
Although carbon, silicon and germanium have same lattice structure and four valence electrons each, their band structure leads to the energy gaps as
  • Eg(Si) g(Ge) g(C)
  • Eg(SD> Eg(Ge)< Eg(C)
  • Eg(Si) < Eg(Ge)> Eg(C)
  • Eg(Si)> Eg(Ge)> Eg(C)
Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 × 1016 m–3. Doping byindium increases nh to 4.5 × 1022 m–3. The doped semiconductor is of
  • n-type with electron concentration ne = 2.5 × 1023m–3
  • p-type having electron concentration ne = 5 × 109m–3
  • n-type with electron concentration ne = 5 × 1022m–3
  • p-type with electron concentration ne = 2.5 ×1010m–3
C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator where as Si is intrinsic semiconductor. This is because
  • In case of C the valence band is not completely filled at absolute zero temperature
  • In case of C the conduction band is partly filled even at absolute zero temperature
  • The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third
  • The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit
In the forward bias arrangement of a PN–junction diode
  • The N–end is connected to the positive terminal of the battery
  • The P–end is connected to the positive terminal of the battery
  • The direction of current is from N–end to P–end in the diode
  • The P–end is connected to the negative terminal of battery
A p–n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength
  • 6000 Å
  • 4000 nm
  • 6000 nm
  • 4000 Å
The reverse biasing in a PN junction diode
  • Decreases the potential barrier
  • Increases the potential barrier
  • Increases the number of minority charge carriers
  • Increases the number of majority charge carriers
What is the current in the circuit shown below?
Physics-Semiconductor Devices-88208.png
  • 0 A
  • 10–2 A
  • 1 A
  • 0.10 A
The PN junction diode is used as
  • An amplifier
  • A rectifier
  • An oscillator
  • A modulator
In the depletion region of an unbiased P–N junctiondiode there are
  • Only electrons
  • Only holes
  • Both electrons and holes
  • Only fixed ions
What controls the conduction of PN junction
  • Majority carriers
  • Minority carriers
  • Holes
  • Electron
The approximate ratio of resistances in the forward and reverse bias of the PN–junction diode is
  • 102 :1
  • 10–2 :1
  • 1 : 10–4
  • 1 : 104
In a junction diode, the holes are due to
  • Protons
  • Neutrons
  • Extra electrons
  • Missing of electrons
In forward bias, the width of potential barrier in a P – N junction diode
  • Increases
  • Decreases
  • Remains constant
  • First increases then decreases
The cause of the potential barrier in a P – N diode is
  • Depletion of positive charges near the junction
  • Concentration of positive charges near the junction
  • Depletion of negative charges near the junction
  • Concentration of positive and negative charges near the junction
The dominant mechanism for motion of charge carriers in forward and reverse biased silicon P - N junctions are
  • Drift in forward bias, diffusion in reverse bias
  • Diffusion in forward bias, drift in reverse bias
  • Diffusion in both forward and reverse bias
  • Drift in both forward and reverse bias
Which circuit will not show current in ammeter?

  • Physics-Semiconductor Devices-88210.png
  • 2)
    Physics-Semiconductor Devices-88211.png

  • Physics-Semiconductor Devices-88212.png

  • Physics-Semiconductor Devices-88213.png
In a P – N junction diode if P region is heavily doped than n region then the depletion layer is
  • Greater in P region
  • Greater in N region
  • Equal in both region
  • No depletion layer is formed in this case
Which one is in forward bias

  • Physics-Semiconductor Devices-88214.png
  • 2)
    Physics-Semiconductor Devices-88215.png

  • Physics-Semiconductor Devices-88216.png
  • None of these
The reason of current flow in P - N junction in forward bias is
  • Drifting of charge carriers
  • Minority charge carriers
  • Diffusion of charge carriers
  • All of the above
The resistance of a reverse biased P - N junction diode is about
  • 1 ohm
  • 102ohm
  • 103 ohm
  • 106 ohm
In comparison to a half wave rectifier, the full waverectifier gives lower
  • Efficiency
  • Average dc
  • Average output voltage
  • None of these
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