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Unformatted text preview: EEE 352 – Fall 2007 Test 2 Solutions October 31, 2007 1. A Si pn junction is measured to have a builtin potential of 0.9 V and a junction depletion width of 0.1 µ m. What are N D and N A in the n and ptype regions, respectively? The ntype region has the heavier doping. From the junction builtin voltage equation, we can find the product N D N A as: 6 35 20 2 2 10 78 . 2 0259 . 9 . exp 10 25 . 2 exp ln − × = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ × = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = cm T k eV n N N n N N T k eV B bi i A D i A D B bi From the junction width, we can find the sum of the two dopants as: 3 18 14 2 5 19 35 2 10 14 . 2 10 854 . 8 7 . 11 2 ) 10 ( 10 6 . 1 10 78 . 2 2 2 − − − − × = × ⋅ ⋅ × × = = = + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + = cm V eW N N N N N N N N e V W bi A D A D A D A D bi ε ε We can now solve these two equations together to find: 3 17 3 18 10 4 . 1 10 . 2 − − × = × = cm N cm N A D ....
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This note was uploaded on 04/04/2008 for the course EEE 352 taught by Professor Ferry during the Fall '08 term at ASU.
 Fall '08
 Ferry

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