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EEE 352—Spring 2008
Homework 9
7.1
Calculate V
bi
in a silicon pn junction at T = 300 K for (a) N
d
= 10
15
cm
3
and N
a
=
(i) 10
15
, (ii) 10
16
, (iii) 10
17
, and (iv) 10
18
cm
3
.
(b) Repeat for N
d
= 10
18
cm
3
.
To begin, the builtin potential is given by(7.10) to be
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
2
ln
i
d
a
B
bi
n
N
N
e
T
k
V
.
Using the value of n
i
from Table B.4, we find the following values:
N
a
=
10
15
10
16
10
17
10
18
(a)
N
d
= 10
15
cm
3
0.575
0.634
0.694
0.754
(b)
N
d
= 10
18
cm
3
0.754
0.813
0.873
0.932
7.5
An abrupt pn junction at zero bias has dopant concentrations of N
a
= 10
17
cm
3
and N
d
= 5
×
10
15
cm
3
.
T = 300 K.
(a) Calculate the Fermi level on each side of
the junction with respect to the intrinsic Fermi level.
(b) Sketch the equilibrium
band diagram for the junction and determine V
bi
from the diagram and the results
of part (a).
(c) Calculate V
bi
using Eq. (7.10), and compare the results to part (b).
(d) determine x
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This homework help was uploaded on 04/03/2008 for the course EEE 352 taught by Professor Ferry during the Spring '08 term at ASU.
 Spring '08
 Ferry

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