646s05hw6 - ELEG 646; ELEG 446 - Nanoelectronic Device...

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ELEG 646; ELEG 446 - Nanoelectronic Device Principles – Spring 2005 Homework #6 - due Thursday, 21 April 2005, in class 1. A symmetrical abrupt Ge p-n junction has an impurity concentration of 10 15 atoms cm -3 on both sides. Calculate the avalanche breakdown voltage if the maximum field at breakdown is 2.5 x 10 5 V/cm. Calculate the breakdown voltage if the impurity concentration on the n-side remains the same, but on the p-side it becomes 10 19 cm -3 . 2. Using the value of ionization coefficient α i ( E ) of 1.8x10 -35 E 7 cm -1 (where E is the electric field), use the avalanche breakdown integral condition (Eq. 4.4.9 in MKC text) to show that the avalanche breakdown voltage of an abrupt silicon p-n junction is given by: V B (volts) = 5.3x10 13 N I -3/4 . Here N I = N A N D /(N A + N D ) is the effective doping concentration in a junction that is assumed to be equivalent to a one sided step junction so that the electric field is only on one side (from 0 to W). 3.
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