CBSE 2024 · Region 2 · Set 1 · Q21 · 2 marks
How does the energy gap of an intrinsic semiconductor effectively change when doped with a (a) trivalent impurity, and (b) pentavalent impurity? Justify your answer in each case.
Marking-scheme solution
(a)
Decreases.
Justification: An acceptor energy level is formed just above the top of the valence band.
(b)
Decreases.
Justification: A donor level is formed just below the bottom of the conduction band.
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