1
GATE ECE 2022
+1
-0.33

Consider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is 1017 cm$$-$$3 and the intrinsic carrier concentration is 1010 cm$$-$$3. Electron and hole diffusion lengthss are 2 $$\mu$$m and 1 $$\mu$$m, respectively. The left side of the bar (x = 0) is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at x = 0 because of the laser. The steady state electron density at x = 0 is 1014 cm$$-$$3 due to laser illumination. Under these conditions and ignoring electric field, the closest approximation (among the given options) of the steady state electron density at x = 2 $$\mu$$m, is _____________.

A
0.37 $$\times$$ 1014 cm$$-$$3
B
0.63 $$\times$$ 1013 cm$$-$$3
C
3.7 $$\times$$ 1014 cm$$-$$3
D
103 cm$$-$$3
2
GATE ECE 2022
+1
-0.33

In a non-degenerate bulk semiconductor with electron density n = 1016 cm$$-$$3, the value of EC $$-$$ EFn = 200 meV, where EC and EFn denote the bottom of the conduction band energy and electron Fermi level energy, respectively. Assume thermal voltage as 26 meV and the intrinsic carrier concentration is 1010 cm$$-$$3. For n = 0.5 $$\times$$ 1016 cm$$-$$3, the closest approximation of the value of (EC $$-$$ EFn), among the given options is _________.

A
226 meV
B
174 meV
C
218 meV
D
182 meV
3
GATE ECE 2022
MCQ (More than One Correct Answer)
+1
-0.33

Select the CORRECT statements regarding semiconductor devices

A
Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.
B
Collector region is generally more heavily doped than Base region in a BJT.
C
Total current is spatially constant in a two terminal electronic device in dark under steady state condition.
D
Mobility of electrons always increases with temperature in Silicon beyond 300 K.
4
GATE ECE 2017 Set 1
+1
-0.3
A bar of Gallium Arsenide (GaAs) is doped with Silicon such that the Silicon atoms occupy Gallium and Arsenic sites in the GaAs crystal. Which one of the following statement is true?
A
Silicon atoms act as p-type dopants in Arsenic sites and n-type dopants in Gallium sites
B
Silicon atoms act as n-type dopants in Arsenic sites and p-type dopants in Gallium sites
C
Silicon atoms act as p-type dopants in Arsenic as well as Gallium sites
D
Silicon atoms act as n-type dopants in Arsenic as well as Gallium sites
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