Homework VIII
Fall 2009
Due: Monday, November 02, 2009
Print your name and netid legibly. Show all work leading to your answer clearly
and neatly. Staple multiple pages.
Problem # 1:
A semiinfinite ptype bar is illuminated with light which generates
G
L
electronhole pairs per cm
3
sec uniformly throughout the volume of the
semiconductor.
Simultaneously, carriers are extracted at x = 0 making Δn
p
= 0 at
x = 0.
Assuming a steady state condition has been established and Δn
p
<< p0 for
all x, determine Δn
p
(x) (the excess electron concentration). (Hint: make use of
the diffusion equation 4:34)
Problem # 2:
As pictured above, the x > 0 portion of an infinite semiconductor is
illuminated with light.
The light generates G
op
= 10
15
electronhole pairs/cm3sec
uniformly throughout the x > 0 region of the bar.
G
op
= 0 for x < 0, steady state
conditions prevail, the semiconductor is silicon, the entire bar is uniformly doped
with N
D
= 10
18
/cm
3
, τ
P
= 10
6
sec, and T = 300 K.
(a)
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 Spring '08
 Staff
 Steady State, excess hole concentration, Δnp

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