UNIVERSITY OF CALIFORNIA
College of Engineering
Department of Electrical Engineering and Computer Sciences
EE 105
Prof. Salahuddin
Fall 2009
Homework Assignment #2
Due at the beginning of class on Tuesday (9/15/2009)
Problem 1
[20 points]: P& Junction
IV
The minoritycarrier diffusion lengths (
L
n
and
L
p
) are related to the minoritycarrier diffusion constants (
D
n
and
D
p
, respectively) by the equation
τ
D
L
=
, where
is the minoritycarrier lifetime.
Consider a PN junction of area 100
μ
m
2
formed by locally introducing
boron into the surface region of a silicon sample that is uniformly
doped with phosphorus, as shown to the right.
The minoritycarrier
lifetime for electrons in the Ptype region is
n
= 0.01
μ
s, and the
minoritycarrier lifetime for holes in the Ntype region is
p
= 1
μ
s.
The diode is maintained at 300K.
a)
Calculate the diode saturation current,
I
S
.
(Use the mobility curves
from Problem 3 of HW#1 to determine the minority carrier
mobilities within the quasineutral regions, and then use the
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 Fall '07
 KingLiu
 Pn junction, constantvoltage diode model, diode saturation, minoritycarrier diffusion

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