hw03 - ECE 315 Homework 3 Due 12noon Sept 13 2007 in the...

ECE 315 Homework 3
Due 12noon, Sept. 13, 2007 in the drop box
1. (P-N junction, continued from Prob. 7 of HW 2. Please follow the numbers there. ) For
a p-n junction well described by the depletion region approximation as shown below, assume
the electron mobility μ
n
=1000cm
2
/Vs, the hole mobility μ
p
=400cm
2
/Vs, and the minority
lifetime τ
n
= τ
p
=10
-7
s
(a) In equilibrium, which region(s) satisfy the charge neutrality condition? Explain briefly.
(4 pts)
(b) In equilibrium, which region(s) satisfy the relation of np=n
i
2
? Explain briefly. (4 pts)
(c) At V
D
=0, Calculate the depletion capacitance in F/cm
2
. (4 pts)
(d) Estimate the ideal saturation current I
S
at 250K, 300K and 400K. You can use the n
i
values from Problem 2 of Homework 2. Assume A = 1cm
2
. (6 pts)
2. (Generation and recombination in the depletion region) For the p-n junction in Prob. 1,
the voltage across the diode is V
D
and the current is I
D
.
(a) At V
D
= 0.6V forward bias, what is the minority carrier concentrations at –x
p
and x
n
? (4
pts)
(b) At V
D
= – 1.0V reverse bias, what is the minority carrier concentrations at –x
p
and x
n
? (4
pts)
(c) Plot the log( n ) and log( p ) throughout the entire device under V
D
=0V, V
D
=0.6V and
V
D
= – 1.0V in the same plot (for better comparison). (4 pts)
(d) Plot J
n
, J
p
and J
n
+J
p
throughout the entire device under V
D
=0V, V
D
=0.6V and V
D
= –
1.0V in separate plots. (4 pts)
(e)