Question

A Si step junction maintained at room temperature under equilibrium conditions has a p-side doping of Na = 2x1015/cm3 , and an n-side doping of Nd = 1015/cm3 . Compute (a) Built-in potential Vbi (b) Depletion region width W, and xp, xn (c) Maximum electric field at x=0 (d) Electrostatic potential V at x=0 (e) Make sketches of the charge density, electric field, and electrostatic potential as a function of position x

Answer 1

cm3 Given that the P-side doping Na= 2x100 No = 1015 Iam3 we have to find built in potential built in potential Voi = Vy In Na Nd Ni2 For si Ni = 1.5x100 Iam3 V+ = 26 mv at room temp Voi = 0.026 m | 2x10'5 x 10's) (1.5X10102) = 0.026 in 1 2x1030 1 12.25x1620) Vbi = 0.595 v (b) we have to find the depletion width Depletion width is given by 2x8.85x 1612 x 0.595 wa ? Even nat te bergs () W= 0.314 um Xp = wx No - Natna 0.314x106. 10 s 2x10'5 +1015 Xp= 0.1046 um Xn - wx Na = 0.314 x 0. 2093 um 0.209 = (0) 0.314 x 2x1015 2x101541015 (el Maximum Electric field 1 Emax ) = 2V! - 2x0.595 - 3.789 M V w 0.314 (FI Electrostatic potential v= -(Edn at nao V=0

- 6 Sketch of Electric field, Electrostatic potential choon Sketch Now to of charge density, draw change density 10000 cloooo @ 000 000 in charge density - - 250"