Mid Term Exam
October 25, 2005
An abrupt Si p-n junction has the following properties at 300 ^{o}K:
Property | P side | N side | Unit |
Doping | N_{A} = 10^{18 } | N_{D} = 10^{16 } | cm^{-3} |
Lifetime | t_{n} = 0.1 | t_{p} = 10 | uS |
Mobility | u_{n} = 250 | u_{n} = 1200 | cm^{2}/V-s |
Mobility | u_{p} = 100 | u_{p} = 350 | cm^{2}/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.
V_{bi} = V_{T} ln[N_{A}N_{D} / n_{i}^{2}] = 0.817VC_{J} = A[eq N_{D} / 2 V_{bi}] = 3.1 pF
t_{b} is the base transit time.t_{b} = Q/I = w_{n}^{2} / 2 D_{p}
t_{b} = r C_{Diff}
r = V_{T}/I
C_{Diff} = t_{b} I /V_{T} = (3x10^{-4})^{2} * 10^{-3} / 2* 0.0259*440*0.0259 = 150 pF