A pn junction may be formed by depositing a single crystal film of uniformly doped p-silicon onto a substrate that has been doped n-type. The substrate is 500um thick, and the film is 20um thick. The substrate has a 5 ohm-cm resistivity.
a) If the film is doped 1015boron/cm3, find Vbi, W, xp and xn at equilibrium.
b) Repeat a) but for 1017boron/cm3 . How have things changed?
c) Draw a circuit schematic showing a bias of +0.5V applied to each diode and recomputed W for both devices.
d) Repeat c), but for -10V bias. Discuss how things are changing.
e) Finally, under the -10V bias, put a 15mV ac voltage is series with the DC bias. Explain what will happen in the device in terms of W and the free charges.