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ESE 2021 Technical Quiz 33 || Semiconductors-2
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Question 1
Two exactly same semiconductors formed from materials having bandgap of1.1 eV and 0.7 eV are taken.Then the ratio of intrinsic carrier concentration Of the first semiconductor to the second one will be _____ 
10-3 (assuming kT=0.026 eV).
10-3 (assuming kT=0.026 eV). Question 2
Silicon is doped with boron to a concentration of 4×1017 atoms/cm3. Assuming the intrinsic carrier concentration of silicon to be 1.5×1010/cm3 and the value of 
to be 25 mV at 300 K
Compared to undoped silicon, the Fermi level of doped silicon?
Question 3
The effective masses of electron and hole in germanium are mn = 0.55mO and mp = 0.37mO respectively, then the energy difference between mid-band level and intrinsic Fermi level at 300 K in Ge is
Question 4
At T=300 K, an n-type silicon sample contains a donor concentration Nd = 1016 cm-3 and intrinsic concentration ni = 1.5 × 1010 cm-3 the minority carrier hole lifetime is found to be 
= 20 µs. What will be the thermal-equilibrium hole recombination rate in the material?
= 20 µs. What will be the thermal-equilibrium hole recombination rate in the material? Question 5
A semiconductor sample at room temperature has intrinsic concentration of 2.5 X 1017 /m3. After doping what will be the minority carrier concentration if the majority carrier concentration is given as 5.5 X 1021 /m3.
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