1. A small concentration of minority carriers is
injected into a homogeneous semiconductor crystal at one point. An electric
field of 10 V/cm is applied across the crystal and this moves the minority
carriers a distance of 1 cm in 20 µsec. the mobility in cm2/volt-sec
will be [GATE’94]
a.
1,000
b.
2,000
c.
5,000
d.
50,000
2.
[GATE’10]
3. Drift current in semiconductors depends upon [GATE’11]
a.
Only the electric field
b.
Only the carrier concentration gradient
c.
Both the electric field and the carrier
concentration
d.
Both the electric field and the carrier
concentration gradient
4.
The electron concentration in a sample of
uniformly doped n-type silicon at 300oK varies linearly from 1017
/cm3 at x = 0 µm to 6 x 1016 /cm3 at x = 2 µm.
Assume a situation that electrons are supplied to keep this concentration
gradient constant with time. If electronic charge is 1.6 x 10-19
coulomb and the diffusion constant Dn = 35 cm2/sec, the
current density in the silicon, if no electric field is present, is [GATE’03]
a.
Zero
b.
-112 A/cm2
c.
+1120 A/cm2
d.
-1120 A/cm2
5.
Under low level injection assumption, the
injected minority carrier current for an extrinsic semiconductor is essentially
the [GATE’06]
a.
Diffusion current
b.
Drift current
c.
Recombination current
d.
Induced current
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