Question 1

What distinguishes a direct bandgap semiconductor from an indirect bandgap semiconductor?

Accepted Answer

In direct bandgap semiconductors, electrons can directly recombine with holes and emit photons.

Answer

Indirect bandgap semiconductors emit phonons instead of photons.

Answer

Direct bandgap semiconductors have a larger energy gap than indirect ones.

Answer

Indirect bandgap materials are always better conductors than direct ones.

Question 2

Which of the following materials is an example of a direct bandgap semiconductor?

Accepted Answer

Gallium arsenide (GaAs)

Answer

Zinc oxide (ZnO)

Answer

Silicon (Si)

Answer

Germanium (Ge)

Question 3

What is the primary consequence of a semiconductor having an indirect bandgap?

Accepted Answer

It is less efficient at emitting light compared to direct bandgap semiconductors.

Answer

It has a higher thermal conductivity.

Answer

It operates at higher temperatures.

Answer

It can absorb light more efficiently.

Question 4

Why are direct bandgap semiconductors preferred for light-emitting applications?

Accepted Answer

They allow for efficient radiative recombination of electron-hole pairs.

Answer

They can conduct electricity better than indirect ones.

Answer

They have a higher melting point.

Answer

They do not require any external energy for light emission.

Question 5

In the context of semiconductor physics, what does the term 'bandgap' refer to?

Accepted Answer

The energy difference between the top of the valence band and the bottom of the conduction band.

Answer

The temperature at which a semiconductor conducts electricity.

Answer

The frequency of emitted light from a semiconductor.

Answer

The density of charge carriers within the semiconductor.

Question 6

What type of transitions typically occur in indirect bandgap semiconductors during electron-hole recombination?

Accepted Answer

Phonon-assisted transitions are necessary for recombination.

Answer

No transitions occur at all.

Answer

Direct photon emission without assistance.

Answer

Electrons jump to energy levels in nearby materials.

Question 7

What is the typical energy bandgap range of direct bandgap semiconductors used in visible light applications?

Accepted Answer

1.8 eV to 3.5 eV

Answer

4.0 eV to 6.0 eV

Answer

0.1 eV to 0.5 eV

Answer

0.7 eV to 1.2 eV

Question 8

Which of the following statements is true about photonic devices made from direct bandgap semiconductors?

Accepted Answer

They can efficiently convert electrical energy into light.

Answer

They primarily operate in the infrared spectrum.

Answer

They cannot be used in laser applications.

Answer

They require a higher energy input than indirect semiconductors.

Question 9

What effect does temperature have on the bandgap of semiconductors?

Accepted Answer

The bandgap generally decreases with increasing temperature.

Answer

The bandgap increases with increasing temperature.

Answer

The bandgap remains constant regardless of temperature.

Answer

The bandgap switches between direct and indirect.

Question 10

Which of the following applications would likely benefit most from using direct bandgap semiconductors?

Accepted Answer

Light-emitting diodes (LEDs)

Answer

Thermal sensors

Answer

Solar panels

Answer

Transistors

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