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Unformatted text preview: ECE 340 Homework XI Fall 2003 Due: Friday, October 24, 2003 1. A p +-n silicon diode (V o = 0.956 volts) has a donor doping of 10 17 /cm 3 and an n-region width = 1 μm. Does it break down by avalanche or punchthrough? What if the doping is only 10 16 /cm 3 ? Refer to Fig. 5-22. Solutions: (a) Since 0.956 V v o l t s = 17 3 10 d N c m − = , and 2 ln a d i N N kT V q n = , we have 19 3 2.4123 10 a N c m − = × , we see indeed Na >>N d . From Fig. 5-22, the V br for silicon at 17 3 10 d N c m − = is about 12 volts. The voltage (V) we used to calculate the depletion width therefore is about 12.956, or approximately 13 volts. At that voltage, the depletion region width extending to n region is: ( ) 2 2 0.412 a n d a d d N V V x m q N N N q N ε ε µ ⎛ ⎞ = ≈ = ⎜ ⎟ ⎜ ⎟ + ⎝ ⎠ (**) Because x n0 is less than the physical n-region width, therefore, avalanche breakdown is going to happen before punch-through....
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- Fall '03
- Volt, P-n junction, Volts, nd, physical n-region width