What is the advantage of direct bandgap semiconductor materials for optical sources?

Direct-bandgap semiconductors can emit light efficiently because electrons can drop directly from the conduction band to the valence band without changing their momentum, which requires interactions that can drain away energy.

Why do direct band gap semiconductors make better LEDS and lasers than indirect band gap materials?

A direct bandgap material tends to have a much larger radiative recombination rate (or probability) than an indirect bandgap material. The radiative recombination efficiency (or the brightness of a LED) is the result of competition between the two processes.

Why is a direct bandgap semiconductor more useful than an indirect bandgap semiconductor for the development of a light emitting diode?

The same principle applies to recombination of electrons and holes to produce photons. The recombination process is much more efficient for a direct band gap semiconductor than for an indirect band gap semiconductor, where the process must be mediated by a phonon.

What is the difference between direct band gap and indirect band gap?

If the k-vectors are different, the material has an “indirect gap”. The band gap is called “direct” if the crystal momentum of electrons and holes is the same in both the conduction band and the valence band; an electron can directly emit a photon. Indirect bandgap materials include crystalline silicon and Ge.

Why indirect band gap materials are not useful in optoelectronic devices?

In an “indirect” gap, a photon cannot be emitted because the electron must pass through an intermediate state and transfer momentum to the crystal lattice.

Why semiconductors are preferred to make LED?

The preferred semiconductors that are used in making the LED are Gallium Arsenide, Gallium phosphide or the combination of the two Gallium arsenide phosphide. It dramatically decreases power costs and also the LED’s are more luminous than the bulbs because most of the power of the bulb goes waste as heat.

Is led indirect band gap semiconductor?

But if you have an indirect band gap the electrons and holes have a different ⃗ vector, and so a momentum has to be transferred → you will get a lattice vibriation, which means you will get the energy in form of a phonon at the recombination. Because of that a LED has a semiconductor with a direct band gap.

Which of the following is known as indirect band gap semiconductors?

Which of the following is known as indirect band gap semiconductors? Explanation: The elemental semiconductor is made up of a single element from the fourth column elements such as Germanium. Here recombination takes place takes place via traps. It is called indirect band gap semiconductors.

Is silicon direct or indirect band gap?

It is well known that Si is an indirect band gap semiconductor with a large energy difference between the direct gap (3.5 eV) and the indirect gap (1.1 eV).

Is GE a an direct or indirect band gap semiconductor?

Germanium is an indirect semiconductor like silicon but with a smaller band gap and a direct band gap transition slightly above the indirect one. This properties makes Ge superior to Si for optical applications from the visible to the NIR (1.6 μm).

Why do the indirect band gap semiconductors have smaller absorption coefficient compared to those having direct band gap?

For an indirect band gap semiconductor, like Si, absorption occurs when there is a lattice vibration (phonon) assisting the photon absorption. So the absorption coefficient increases less slowly above Eg, compared to GaAs.