Semiconductor Questions and Answers:
Ques: A P-type semiconductor can be obtained by adding
(a) Arsenic to pure silicon
(b) Gallium to pure silicon
(c) Antimony to pure germanium
(d) Phosphorous to pure germanium
Ques: When the electrical conductivity of a semi- conductor is due to the breaking of its covalent bonds, then the semiconductor is said to be
(a) Donar
(b) Acceptor
(c) Intrinsic
(d) Extrinsic
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Ques: Which statement is correct?
(a) N-type germanium is negatively charged and P-type germanium is positively charged
(b) Both N-type and P-type germanium are neutral
(c) N-type germanium is positively charged and P-type germanium is negatively charged
(d) Both N-type and P-type germanium are negatively charged
Ques: The impurity atoms which are mixed with pure silicon to make a P-type semiconductor are those of
(a) Phosphorus
(b) Boron
(c) Antimony
(d) Copper
Ques: At zero Kelvin a piece of germanium
(a) Becomes semiconductor
(b) Becomes good conductor
(c) Becomes bad conductor
(d) Has maximum conductivity
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Ques: In a good conductor the energy gap between the conduction band and the valence band is
(a) Infinite
(b) Wide
(c) Narrow
(d) Zero
Ques: A semiconductor is cooled from T1K to T2K. Its resistance
(a) Will decrease
(b) Will increase
(c) Will first decrease and then increase
(d) Will not change
Ques: The temperature coefficient of resistance of a semiconductor
(a) Is always positive
(b) Is always negative
(c) Is zero
(d) May be positive or negative or zero
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Ques: An N-type and P-type silicon can be obtained by doping pure silicon with
(a) Arsenic and Phosphorous
(b) Indium and Aluminium
(c) Phosphorous and Indium
(d) Aluminium and Boron
Ques: For germanium crystal, the forbidden energy gap in joules is
(a) 1.12 x 10–19
(b) 1.76 x 10–19
(c) 1.6 x 10–19
(d) Zero
Ques: In a P-type semiconductor, germanium is doped with
(a) Boron
(b) Gallium
(c) Aluminium
(d) All of these
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Ques: At room temperature, a P-type semiconductor has
(a) Large number of holes and few electrons
(b) Large number of free electrons and few holes
(c) Equal number of free electrons and holes
(d) No electrons or holes
Ques: The process of adding impurities to the pure semiconductor is called
(a) Drouping
(b) Drooping
(c) Doping
(d) None of these
Ques: Which of the following has negative temperature coefficient of resistance?
(a) Copper
(b) Aluminium
(c) Iron
(d) Germanium
Ques: Which of the following statements is true for an N-type semi-conductor?
(a) The donor level lies closely below the bottom of the conduction band
(b) The donor level lies closely above the top of the valence band
(c) The donor level lies at the halfway mark of the forbidden energy gap
(d) None of above
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Ques: In a P-type semi-conductor, germanium is dopped with
(a) Gallium
(b) Boron
(c) Aluminium
(d) All of these
Ques: The charge on a hole is equal to the charge of
(a) Zero
(b) Proton
(c) Neutron
(d) Electron
Ques: In extrinsic semiconductors
(a) The conduction band and valence band overlap
(b) The gap between conduction band and valence band is more than 16 eV
(c) The gap between conduction band and valence band is near about 1 eV
(d) The gap between conduction band and valence band will be 100 eV and more
Ques: The energy gap of silicon is 1.14 eV. The maximum wavelength at which silicon will begin absorbing energy is
(a) 10888 Å
(b) 1088.8 Å
(c) 108.88 Å
(d) 10.888 Å
Ques: The mobility of free electron is greater than that of free holes because
(a) The carry negative charge
(b) They are light
(c) They mutually collide less
(d) They require low energy to continue their motion
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Ques: Doping of intrinsic semiconductor is done
(a) To neutralize charge carriers
(b) To increase the concentration of majority charge carriers
(c) To make it neutral before disposal
(d) To carry out further purification
Ques: To a germanium sample, traces of gallium are added as an impurity. The resultant sample would behave like
(a) A conductor
(b) A P-type semiconductor
(c) An N-type semiconductor
(d) An insulator
