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Problem 1 (25 points)
Consider a silicon pn junction with a crosssectional area of 10
4
cm
2
and the
following parameters at T = 300K:
17
3
15
3
7
6
10
,
5 10
,
10
,
10
N
cm
N
x
cm
s
s
d
a
p
n
22
400
/ . ,
1000
/ .
pn
cm V s
cm V s
a)
(10 points) Sketch the thermalequilibrium energyband diagram across the pn
junction.
b)
(5 points) Determine the ratio of the hole current to total current at the space
charge edge x
n
c)
(5 points) Determine the ratio of the electron current to total current at the space
charge edge x
p
d)
(5 points) Calculate the total number of excess electrons in the p region for
V
a
=0.5V
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Problem 2 (25 points)
Consider an Si pnp transistor with N
E
= 2x10
17
cm
3
, N
B
= 2x10
16
cm
3
, N
C
= 2x10
15
cm
3
. The metallurgical base width is 1
m and the base cross sectional area is 10
m
2
. Assume the critical field to be equal to 10
5
V/cm.
2
10
14
1.5 10
,
11.7 78.854 10
/
i
s
n
x
cm
x
x
F cm
a)
(5 points) Draw the energy band diagram under equilibrium.
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This note was uploaded on 10/03/2010 for the course ESE 231 taught by Professor Kamoua,r during the Spring '08 term at SUNY Stony Brook.
 Spring '08
 Kamoua,R

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