ece340Fall03HW12sol - ECE 340 Homework XII Due: Wednesday,...

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ECE 340 Homework XII Fall 2003 Due: Wednesday, October 29, 2003 (20 points total) 1. A Schottky barrier is formed between a metal having a work function of 4.2 eV and p-type Si (electron affinity = 4 eV). The acceptor doping in the Si is 5x10 17 /cm 3 . (a) Draw the equilibrium band diagram showing a numerical value for qV o . (b) Draw the band diagram with 0.3 V forward bias with details including the width of the depletion region and other quantities. (c) Repeat part (b) for 2V reverse bias. Solution: (a), At equalibrium: 17 3 51 0 a Nc m , 0.0259ln 0.449 a iF S i N E Ee V n −= = 0 ( / 2 ) (4 0.449 0.55) 5.0 ( ) (1.1 4.2 4) 0.9 54 . 20 . 8 sg i F s Bg m sm qq E E Eq e V qE q q e V Ve V χ Φ= + + − = + + = Φ= − Φ− = − − = =Φ −Φ = − = 14 6 0 19 17 2 21 1 . 88 . 8 0 0 . 8 4.57 10 1.6 10 5 10 a V Wc m qN ε ××× × == = × ×× × (W is not required for grading) Band diagram: (b), Forward bias: B Φ stays the same, band bending is now 0 0.8 0.3 0.5 f VVV V = = 14 6 19 17 2 2 11.8 8.85 10 0.5 3.61 10 1.6 10 5 10 a V m qN × = × × (W is not required for grading)
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(c), Reverse bias: B Φ stays the same, band bending is now 0 0.8 2 2.8 r
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ece340Fall03HW12sol - ECE 340 Homework XII Due: Wednesday,...

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