When an intrinsic semiconductor is doped with a trivalent impurity (say aluminium), an additional acceptor energy level is formed slightly above the top of the valence band. As a result energy gap is reduced to a large extent.
Class 12 Physics NCERT Sample Paper Question Session 2024-2025.
How does the energy gap of an intrinsic semiconductor change when doped with a trivalent impurity?
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When an intrinsic semiconductor is doped with a trivalent impurity (p-type doping), acceptor energy levels are introduced just above the valence band. The overall energy gap remains unchanged, but the effective gap for conduction decreases due to these additional energy levels.
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