ELE533 Bipolar Devices

Mid Term Exam
July 9, 1998

Question 1 Answer

Name_____________________________________

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.

Consider a silicon pn junction. The p side is uniformly doped with 10¹⁶ acceptors/cm³. The n side is doped with 10¹⁸ donors/cm³.

What is the built in potential?     0.81eV

What is the position of the Fermi level relative to the intrinsic level on the p side of the junction?    E_i - E_f = 0.356eV

The junction area is 10 microns by 10 microns. What is the saturation current, Is, in the equation,

I = Is*e^V/Vt

Is = AqD_Nn_i²/W_PN_A = 2.79X10^-16A

Assuming u_n = 1500

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. Show the built-in potential on the diagram.

V_bi = 0.81V,   V_P = - 0.356V,   V_n = 0.465V