Semiconductor Theory

21. In the depletion region of a pn junction, there is a shortage of ___________

1. Acceptor ions
2. Holes and electrons
3. Donor ions
4. None of the above

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22. The barrier voltage at a pn junction for germanium is about ___________

1. 5 V
2. 3 V
3. Zero
4. 3 V

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23. The impurity level in an extrinsic semiconductor is about of pure semiconductor.

1. 10 atoms for 108 atoms
2. 1 atom for 108 atoms
3. 1 atom for 104 atoms
4. 1 atom for 100 atoms

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24. The leakage current across a pn junction is due to ___________

1. Minority carriers
2. Majority carriers
3. Junction capacitance
4. None of the above

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25. The leakage current in a pn junction is of the order of

1. Aa
2. mA
3. kA
4. μA

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26. The most commonly used semiconductor is ___________

1. Germanium
2. Silicon
3. Carbon
4. Sulphur

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27. The random motion of holes and free electrons due to thermal agitation is called ___________

1. Diffusion
2. Pressure
3. Ionisation
4. None of the above

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28. The resistivity of a pure silicon is about ___________

1. 100 O cm
2. 6000 O cm
3. 3 x 105 O m
4. 6 x 10-8 O cm

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29. The strength of a semiconductor crystal comes from ___________

1. Forces between nuclei
2. Forces between protons
3. Electron-pair bonds
4. None of the above

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30. When a pentavalent impurity is added to a pure semiconductor, it becomes ___________

1. An insulator
2. An intrinsic semiconductor
3. p-type semiconductor
4. n-type semiconductor

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