ECE 440
Homework VI
Spring 2006
Due: Monday, February 20, 2006
1. (a) An ntype Si sample with N
d
= 1x10
17
/cm
3
is steadily illuminated such that g
op
= 3x10
21
EHP/cm
3
s. If
τ
n
=
τ
p
=1 μs for the excitation, calculate the separation in the quasiFermi
levels, (F
n
F
p
). Draw a band diagram such as Fig. 411.
(b) At t=0, the illumination in part (a) is terminated. Assuming the carrier lifetimes remain
the same, calculate the separation in the quasiFermi levels at t=4 μs. Draw a corresponding
band diagram at 300 K.
2. Refer to problem 1 part (a) in HW V. The same silicon bar is steadily illuminated at 300 K
and a uniform excess carriers are generated in the Si bar. Assume that
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 Spring '11
 Leburton
 hole concentration, band diagram, diffusion current densities, ntype Si sample

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