ELE533 Bipolar Devices

ELE533 Mid Term Question 2

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

Area = 10^-4 cm^-2
The width of the N neutral region W_N = 3 microns.
The width of the P neutral region W_P = 2 microns.

Answer

C_JO = [qeNd/2Vbi]^1/2 = 2.25pF

where e = the permitivity of silicon , e = 10^-12

C_diff = (I/Vt)X_n²/2Dn = 169pF