1
GATE ECE 2005
+2
-0.6
A silicon sample 'A' is doped with 1018 atoms/cm3 of Boron. Another sample 'B' of identical dimensions is doped with 1018 atoms/cm3 of Phosphorus. The ratio of electron to hole mobility is 1/3. The ratio of conductivity of the sample A to B is
A
3
B
1/3
C
2/3
D
3/2
2
GATE ECE 2003
+2
-0.6
The electron concentration in a sample of uniformly doped n-type silicon at 300oK varies linearly from $$10^{17}/cm^3$$ at x = 0 to $$6\times10^{16}/cm^3$$ at x = 2 $$\mu m$$. Assume a situation that electrons are supplied to keep this concentration gradient constant with time.If electronic charge is $$1.6\times10^{-19}\;coulomb$$ and the diffusion constant $$D_n=3\;cm^2/s$$, the current density in the silicon, if no electric field is present is
A
Zero
B
120 A/cm2
C
+1120 A/cm2
D
-1120 A/cm2
3
GATE ECE 2003
+2
-0.6
An n-type silicon bar 0.1 cm long and $$100\;\mu m^2$$ in cross-sectional area has a majority carrier concentration of $$5\times10^{20}/m^3$$ and the carrier mobility is $$0.13\;\;m^2/v-s\;$$ at 300oK. if the charge of an electron is 1.6×10-19 coulomb, then the resistance of the bar is
A
$$10^6\;\Omega$$
B
$$10^4\;\Omega$$
C
$$10^{-1}\;\Omega$$
D
$$10^{-4}\;\Omega$$
4
GATE ECE 1992
+2
-0.6
A semiconductor is irradiated with light such that carriers are uniformly generated throughout its volume. The semiconductor is n-type with $$N_D=10^{19}/cm^3$$. If the excess electron concentration in the steady state id $$\triangle n=10^{15}/cm^3$$ and if $$\tau_p=10\;\mu\;sec$$ [minority carrier life time] the generation rate due to irradiation
A
$$is\;10^{20}\;e-h\;pairs/cm^3/sec$$
B
$$is\;10^{24}\;e-h\;pairs/cm^3/sec$$
C
$$is\;10^{10}\;e-h\;pairs/cm^3/sec$$
D
cannot be determined as the given data is insufficient
GATE ECE Subjects
Network Theory
Control Systems
Electronic Devices and VLSI
Analog Circuits
Digital Circuits
Microprocessors
Signals and Systems
Communications
Electromagnetics
General Aptitude
Engineering Mathematics
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