1. A Si p-n-p bipolar junction BJT transistor has impurity concentrations of
5×10$^{18}$, 2×10$^{17}$, and 10$^{16}$ cm$^{-3}$ in the emitter, base, and collector,
respectively. The base width is 1.0 µm, and the device cross-sectional area is
0.2 mm$^2$. When the emitter-base junction is forward biased to 0.5eV and the
base-collector junction is reverse biased to 5V.
a) Calculate the actual neutral base width $W$ after subtracting the depletion
width of the emitter-base junction and the depletion width of the base-
collector junction.
b) Calculate the minority carrier concentration at the emitter-base junction
$P_n(0)$.
Assume that the diffusion constants of minority carriers in the emitter, base and
collector are $D_E$= 52 cm$^2$/s, $D_P$ = 40 cm$^2$/s, and $D_C$ =115 cm$^2$/s, respectively and the
corresponding lifetimes are 10$^{-8}$ s, 10$^{-7}$ s and 10$^{-6}$ s.
c) Calculate the current components $I_{EP}$, $I_{CP}$, $I_{EN}$, $I_{CN}$, and $I_{BB}$
$L_P = \sqrt{D_P\tau_P}$
