L37 - SUMMARY FROM LAST CLASS Doped semiconductor N-type...

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Dr. P. Lucas U of A MSE 110 Doped semiconductor SUMMARY FROM LAST CLASS N-type doping corresponds to introduction of donor impurities from Group V which donate negatively charged mobile carriers (electrons) and generate donor states below the conduction band. P-type doping corresponds to introduction of acceptor impurities from Group III which contribute positively charged mobile carriers (holes) and generates acceptor states above the valence band. Intrinsic semiconductors have no dopants. The conductivity is due to charge carriers thermally excited across the band gap E g . Extrinsic semiconductors are doped and the conductivity at room T is due to the holes and electrons contributed by the dopant atoms. All dopants are ionized at room temperature because E b is small compared to kT: In extrinsic semiconductor, the number of charge carrier is constant over the extrinsic temperature region where all the dopant carriers are excited but intrinsic carrier are not significantly excited. = kT E N n b D ex 2 exp
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Dr. P. Lucas U of A MSE 110 Semiconductivity SEMICONDUCTOR DEVICES The conductivity of an intrinsic semiconductor is a contribution of both holes and electrons: σ =n h h + n e e Intrinsic N-type The conductivity of a N-type semiconductor is mainly due to the extrinsic electrons contributed by the donor impurities: σ =n e e . A simple conductivity measurement does not specify which type of charge carrier is responsible for the conductivity. P-type The conductivity of a P-type semiconductor is mainly due to the extrinsic holes contributed by the acceptor impurities: σ = n h h .
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Dr. P. Lucas U of A MSE 110 Hall effect SEMICONDUCTOR DEVICES It is possible to identify the majority charge carrier in a semiconductor using the Hall effect.
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