The electron and hole diffusion coefficients in silicon are D n = 35 cm 2 /s and D p = 12.5 cm 2 /s , respectively. Calculate the electron and hole diffusion current densities (a) if an electron concentration varies linearly from n = 10 15 cm − 3 to n = 10 16 cm − 3 over the distance from x = 0 to x = 2.5 μ m and (b) if a hole concentration varies linearly from p = 10 14 cm − 3 to p = 5 × 10 15 cm − 3 over the distance from x = 0 to x = 4.0 μ m . (Ans. (a) J n = 202 A/cm 2 , (b) J p = − 24.5 A/cm 2 )
The electron and hole diffusion coefficients in silicon are D n = 35 cm 2 /s and D p = 12.5 cm 2 /s , respectively. Calculate the electron and hole diffusion current densities (a) if an electron concentration varies linearly from n = 10 15 cm − 3 to n = 10 16 cm − 3 over the distance from x = 0 to x = 2.5 μ m and (b) if a hole concentration varies linearly from p = 10 14 cm − 3 to p = 5 × 10 15 cm − 3 over the distance from x = 0 to x = 4.0 μ m . (Ans. (a) J n = 202 A/cm 2 , (b) J p = − 24.5 A/cm 2 )
Solution Summary: The author calculates the diffusion current density due to electrons using the following equation: J_n=202A/cm2.
The electron and hole diffusion coefficients in silicon are
D
n
=
35
cm
2
/s
and
D
p
=
12.5
cm
2
/s
, respectively. Calculate the electron and hole diffusion current densities (a) if an electron concentration varies linearly from
n
=
10
15
cm
−
3
to
n
=
10
16
cm
−
3
over the distance from
x
=
0
to
x
=
2.5
μ
m
and (b) if a hole concentration varies linearly from
p
=
10
14
cm
−
3
to
p
=
5
×
10
15
cm
−
3
over the distance from
x
=
0
to
x
=
4.0
μ
m
. (Ans. (a)
J
n
=
202
A/cm
2
, (b)
J
p
=
−
24.5
A/cm
2
)
Silicon is doped with ND= 2 × 1015 impurity atoms/cm3 . Assume the electron and hole mobilities for the given impurity are un = 1320 cm2 / V.s, and up=460 cm2 /V.s respectively. Use ni = 1.5 × 1010/cm3
Calculate the resistivity of silicon.
Assume an aluminum line runs diagonally from one corner of a 20 mm × 20 mm silicon material to the other corner. What is the resistance of this line if it is 1 μm thick and 5 μm wide? The resistivity of pure aluminum is 2.82 μΩ-cm.
A lightly-doped p-type Si region has a hole concentration of 1*10^11 cm-3 at a temperature of 320 K. Assume the hole mobility is 470 cm^2/Vs and the electron mobility is 1430 cm^2/Vs at 320 K. The bandgap of Si is 1.12 eV. Calculate the resistivity of this Si region at 320 K.
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