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Quiz: EDC-Semiconductor Theory

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Number of Questions: 20

Question: 6 -

Consider a semiconductor bar having square cross-section . Assume that holes drift in the positive X-direction and a magnetic field is applied in the positive Z-direction perpendicular to the direction in which holes drift . The sample will show

Options:

  1. a magnetic field in positive Y-direction

  2. a negative resistance in positive Y-direction

  3. a negative voltage in positive Y-direction

  4. a positive voltage in positive Y-direction.

    5. Answer:

    a negative voltage in positive Y-direction
    Solution:

    Holes will be forced towards negative y-direction . So a negative voltage in positive y-direction.

Question: 7 -

when a semiconductor bar is heated at one end , a voltage across the bar is developed . If the heated end is positive , the semiconductor is

Options:

  1. p-type

  2. n-type

  3. intrinsic

  4. Highly degenerate

    5. Answer:

    n-type
    Solution:

    The heated end becomes positive , it means injected minority carrier due to heat are holes . So the bar is of n-type.

Question: 8 -

Consider a Si sample under equilibrium condition , doped with boron concentration of 1017/cm3 . At T=300K , is this material n-type or p-type? What are the majority and minority carrier concentrations ?

Options:

  1. n-type; n=1017/cm3 , p=103/cm3

  2. p-type; p=1017/cm3 , n=103/cm3

  3. n-type; n=1017/cm3 , p=1010/cm3

  4. p-type; p=1017/cm3 , n=1010/cm3

    5. Answer:

    p-type; p=1017/cm3 , n=103/cm3
    Solution not available.

Question: 9 -

In an extrinsic semiconductor , the Hall coefficient RH

Options:

  1. increases with increase of temperature

  2. decreases with increase of temperature

  3. is independent of the change of temperature

  4. changes with change of magnetic field

    5. Answer:

    increases with increase of temperature
    Solution:

    RH is inversely proportiona; to carrier concentration . As temperature increases electron-hole pair starts generating and these carriers starts dominating impurity carriers , so n reduces and RH increases.

Question: 10 -

Which one of the following pairs of semiconductors and current carriers is correctly matched ?

Options:

  1. n - type . . . No. of electrons < No. of holes

  2. p -type . . . No. of electrons > No. of holes

  3. Bulk . . . Neither electrons nor holes

  4. Intrinsic . . . No. of electrons = No. of holes

    5. Answer:

    Intrinsic . . . No. of electrons = No. of holes
    Solution:

    Intrinsic - No. of electrons = No. of holes p-type - No. of electrons < No. of holes n-type - No. of electrons > No. of holes Bulk - Either lightly doped n or p-type