GATE ECE Carrier transport PYQs & Answers

Questions 1–10 of 17. Imported answers require independent review unless marked reviewed.

Consider carrier transport in a Zener diode in the breakdown region. Which is the dominant transport mechanism for current flow in this case?

Your answerChoose one option.

Drift

Diffusion

Tunneling

Ballistic transport

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Consider that the concentration of electrons in a semiconductor bar varies linearly from

along the x-direction. Assume that the concentration of electrons is not varying along other directions (that is along y- and z-directions). [Given: the mobility of electron is

, thermal voltage is

and electron charge is

Coulomb.] The density of electron diffusion current (in A/mm

) is ___. (rounded off to two decimal places)

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The intrinsic carrier concentration of a semiconductor is 2.5 × 10¹⁶ /m³ at 300 K. If the electron and hole mobilities are 0.15 m²/Vs and 0.05 m²/Vs, respectively, then the intrinsic resistivity of the semiconductor (in kΩ.m) at 300 K is ______.

(Charge of an electron e = 1.6 × 10⁻¹⁹ C.)

Your answerChoose one option.

1.65

1.25

0.85

1.95

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The electron mobility μₙ in a non-degenerate germanium semiconductor at 300 K is 0.38 m²/Vs.

The electron diffusivity Dₙ at 300 K (in cm²/s, rounded off to the nearest integer) is ______.

(Consider the Boltzmann constant kB = 1.38 × 10⁻²³ J/K and the charge of an electron e = 1.6 × 10⁻¹⁹ C.)

Your answerChoose one option.

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An electric field of

is applied along the length of a copper wire of circular cross-section with diameter

. Copper has a conductivity of

The current (in Amperes, rounded off to two decimal places) flowing through the wire is ______.

Your answerChoose one option.

0.46

1.82

0.58

1.12

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The free electron concentration profile

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?

Diagram for Electronics and Communication Engineering question 26

Your answerSelect all correct options. You can choose more than one.

For

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

For

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

For

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

For

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

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Consider a long rectangular bar of direct bandgap

-type semiconductor. The equilibrium hole density is

and the intrinsic carrier concentration is

. Electron and hole diffusion lengths are

and

, respectively.

The left side of the bar (

) is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at

because of the laser. The steady state electron density at

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

is _________.

Your answerChoose one option.

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Select the CORRECT statement(s) regarding semiconductor devices.

Your answerSelect all correct options. You can choose more than one.

Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.

Collector region is generally more heavily doped than Base region in a BJT.

Total current is spatially constant in a two terminal electronic device in dark under steady state condition.

Mobility of electrons always increases with temperature in Silicon beyond 300 K.

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-type semiconductor with zero electric field is under illumination (low level injection) in steady state condition. Excess minority carrier density is zero at

, where

cm is the diffusion length for electrons. Assume electronic charge,

C. The profiles of photo-generation rate of carriers and the recombination rate of excess minority carriers (

) are shown. Under these conditions, the magnitude of the current density due to the photo-generated electrons at

is ________ mA/cm

(rounded off to two decimal places).

Diagram for Electronics and Communication Engineering question 56

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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 statements is true?

Your answerChoose one option.

Silicon atoms act as

-type dopants in Arsenic sites and

-type dopants in Gallium sites

Silicon atoms act as

-type dopants in Arsenic sites and

-type dopants in Gallium sites

Silicon atoms act as

-type dopants in Arsenic as well as Gallium sites

Silicon atoms act as

-type dopants in Arsenic as well as Gallium sites

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GATE ECE Carrier transport PYQs

How to practice Carrier transport

Question 14

Question 64

Question 46

Question 48

Question 50

Question 26

Question 16

Question 47

Question 56

Question 9