ELE533 Mid Term Question 1 Answer

An abrupt Si p-n junction has the following properties at 300 oK:
Property P side N side Unit
Doping NA = 1018 ND = 5X1015 cm-3
Lifetime tn = 0.1 tp = 10 uS
Mobility un = 250 un = 1300 cm2/V-s
Mobility up = 100 up = 400 cm2/V-s
A = 10-4 cm-2

Draw the equilibrium energy band diagram for this junction, including numerical values for the Fermi level position relative to the intrinsic level on each side. Find the contact potential from the diagram.


ANSWER

Vn = Ef - Ei = Vt*ln[Nd/ni] = 0.33

Vp = Ei - Ef = Vt*ln[Na/ni] = 0.46 V

Vbi = Vn + Vp = 0.793V