(b)  At T > 0 K, four thermally generated
electron-hole pairs The filled circles ( ) represent electrons
and empty circles ( ) represent holes Rationalised 2023-24
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(ii) Trivalent (valency 3); like Indium (In),
Boron (B), Aluminium (Al), etc We shall now discuss how the doping
changes the number of charge carriers (and
hence the conductivity) of semiconductors