1
GATE ECE 2024
MCQ (More than One Correct Answer)
+1
-0

The free electron concentration profile $n(x)$ in a doped semiconductor at equilibrium is shown in the figure, where the points A, B, and C mark three different positions. Which of the following statements is/are true?

GATE ECE 2024 Electronic Devices and VLSI - Semiconductor Physics Question 2 English
A

For $x$ between B and C, the electron diffusion current is directed from C to B.

B

For $x$ between B and A, the electron drift current is directed from B to A.

C

For $x$ between B and C, the electric field is directed from B to C.

D

For $x$ between B and A, the electric field is directed from A to B.

2
GATE ECE 2023
MCQ (Single Correct Answer)
+1
-0.33

In a semiconductor, if the Fermi energy level lies in the conduction band, then the semiconductor is known as

A
degenerate n-type.
B
degenerate p-type.
C
non-degenerate n-type.
D
non-degenerate p-type.
3
GATE ECE 2023
MCQ (Single Correct Answer)
+1
-0.33

For an intrinsic semiconductor at temperature $$T=0K$$, which of the following statement is true?

A
All energy states in the valence band are filled with electrons and all energy states in the conduction band are empty of electrons.
B
All energy states in the valence band are empty of electrons and all energy states in the conduction band are filled with electrons.
C
All energy states in the valence and conduction band are filled with holes.
D
All energy states in the valence and conduction band are filled with electrons.
4
GATE ECE 2022
MCQ (Single Correct Answer)
+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
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