1. In a P – Type silicon sample, the hole
concentration is 2.25 x 1015 /cm3. If the intrinsic
carrier concentration is 1.5 x 1010 /cm3, the electron
concentration is [GATE’95]
a.
Zero
b.
1010 /cm3
c.
105 /cm3
d.
1.5 x 1010 /cm3
2.
The intrinsic carrier density at 300oK
is 1.5 x 1010 /cm3 for silicon. For N –Type silicon doped
to 2.25 x 1015 /cm3, the equilibrium electron and hole
densities are [GATE’97]
a.
N= 1.5 x 1015 /cm3 , P =
1.5 x 1010 /cm3
b.
N= 1.5 x 1010 /cm3 , P =
2.25 x 1015 /cm3
c.
N= 2.25 x 1015 /cm3 , P =
1.0 x 105 /cm3
d.
N= 1.5 x 1010 /cm3 , P =
1.5 x 1010 /cm3
3.
The electron and hole concentrations in a
intrinsic semiconductor are ni and pi respectively. When
doped with a P – Type material, these change to n and p, respectively. Then [GATE’98]
a.
n + p = ni + pi
b.
n + ni = p +
pi
c.
npi = nip
d.
np = nipi
4.
The intrinsic concentration of silicon sample of
300oK is 1.5 x 1016 /m3, if after doping, the
number of majority carriers is 5 x 1020 /m3, the minority
carrier density is [GATE’03]
a.
4.50 x 1011 /m3
b.
3.33 x 104 /m3
c.
5.00 x 1020 /m3
d.
3.00 x 10-5 /m3
5.
The concentration of minority carriers in an
extrinsic semiconductor under equilibrium is
[GATE’06]
a.
Directly proportional to the doping
concentration
b.
Inversely proportional to the doping
concentration
c.
Directly proportional to the intrinsic
concentration
d.
Inversely proportional to the intrinsic
concentration
6.
The electron and hole concentrations in an
intrinsic semiconductor are ni per cm3 at 300oK.
Now, if acceptor impurities are introduced with a concentration of NA
per cm3 (where NA > ni),
then electron concentration per cm3 at 300oK will be [GATE’07]
a.
ni
b.
ni + NA
c.
NA – ni
d.
ni2 / NA
7.
A silicon sample is uniformly doped with 1016
phosphorous atoms / cm3 and
2x 1016 boron atoms/cm3 . if all the dopants are fully
ionized, the material is [GATE’91]
b.
p-type with carrier concentration of 1016 /cm3
c.
p-type with carrier concentration of 2x 1016 /cm3
d.
n-type with carrier concentration of 2x1016 /cm3
where is the solution
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