Chapter 18.5

Chapter 18.5 - Intrinsic semiconductors (III) MSE 2090:...

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21 MSE 2090: Introduction to Materials Science Chapter 18, Electrical Conductivity Intrinsic semiconductors (III)
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22 MSE 2090: Introduction to Materials Science Chapter 18, Electrical Conductivity Intrinsic semiconductors (IV) σ = n|e|( μ e + μ h ) Let’s calculate carrier concentration for Si at 300 K ) ( | | n h e e μ + μ σ = 3 16 1 1 2 19 1 1 4 m 10 3 . 1 s V m ) 05 . 0 14 . 0 ( C 10 6 . 1 m 10 4 n × = + × × Ω × = A V = Ω s C A = molar volume of Si 12 cm 3 /mol N A 6 × 10 23 atoms/mol 6 × 10 23 / 12 × 10 -6 = 5 × 10 28 atoms/m 3 fraction of excited electrons per atom ~10 -13
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23 MSE 2090: Introduction to Materials Science Chapter 18, Electrical Conductivity Extrinsic semiconductors Extrinsic semiconductors - electrical conductivity is defined by impurity atoms. Example : Si is considered to be extrinsic at room T if impurity concentration is one impurity per 10 12 lattice sites (remember our estimation of the number of electrons promoted to the conduction
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Chapter 18.5 - Intrinsic semiconductors (III) MSE 2090:...

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