hw_3_sol - HOMEWORK 3 - SOLUTIONS 2.21. (a) Silicon is...

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HOMEWORK 3 - SOLUTIONS 2.21. (a) Silicon is doped with N D =5&10 15 cm -3 . Find n 0 and p 0 , and locate the Fermi level. Draw the energy band diagram. The material will be n-type. Since the number of donors is much greater than the intrinsic concentration, and assuming all dopants to be ionized, then n 0 = N D . Thus n 0 = 5 × 10 15 cm 3 = N C e E C E f kT assuming non-degenerate material (which we will check later). So E C E f =− kT ln N D N C 0.026 eV ln 5 × 10 15 2.86 × 10 19 = 0.22 eV Since 0.22>2.3kT, the assumption of non-degeneracy is verified. 21 0 2 4- 3 0 15 0 ( ) (1.08 10 ) 2.3 10 cm 51 0 i n p n × == = × × b) A new batch of silicon is doped with boron to N A =4&10 15 cm -3 . Find n 0 and p 0 and locate the Fermi level. Draw the energy band diagram. Again we assume non-degenerate material and complete ionization. thus p 0 =4&10 15 , and E f E V kT ln N A N V 0.026 eV ln 4 × 10 15 3.1 × 10 19 = 0.23 eV E E C V E i 1.12eV 0.23eV f E 2 3 0 0 () 2.9 10 cm i n n p ×
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2.22. Silicon is doped with
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This note was uploaded on 01/11/2012 for the course ECE 432 taught by Professor Lu during the Fall '08 term at Ohio State.

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hw_3_sol - HOMEWORK 3 - SOLUTIONS 2.21. (a) Silicon is...

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