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Which of the following statements are correct with respect to semiconductors?

Electrons are charge carriers in n-type semiconductors.

a. The addition of group 3A elements to group 4A semiconductors decreases the conductivity of the group 4A semiconductors.

b. Holes are charge carriers in p-type semiconductors.

c.The conductivity of semiconductors can be increased by the doping process.

d.The addition of group 5A elements to group 4A semiconductors increases the conductivity of the group 4A semiconductors.

e.As the temperature increases, the conductivity of semiconductors decreases.

2 Answers

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  • Anonymous
    8 years ago
    Favorite Answer

    All are correct except a.

    Addition of group IIIA elements increases the conductivity of group IVA semiconductors by increasing the number of holes.

    (Addition of group VA elements does this by increasing the number of free electrons.)

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  • 6 years ago

    A and E are not true.

    A is false because the addition of group 3A elements to group 4A semiconductors will increase the conductivity of group 4A because as you move down the periodic table the distance between the bond gap shortens until you get to the bottom where no bond gap occurs. For example the bond gap decreases as you move from diamond (carbon), to silicon, to germanium, to gray tin. Moving one element down to lead, the band gap collapses altogether. As a result, led has the structure and properties of a metal.

    E is false because as the temperature increases the conductivity of semiconductors increase as well because as the temperature increases, electrons from the valence band are promoted to the conduction band, and the number of charge carriers in the conduction band increases.

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