What is the difference between direct and indirect band gap?

What is the difference between direct 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.

What is the difference between direct bandgap and indirect bandgap semiconductors what type of semi conductors are used in optical sources?

In direct bandgap semiconductor the electron “rising” from valence band to the conduction band will only change it’s potential (energy). In indirect bandgap semiconductor the electron “rising” from valence band to the conduction band will change it’s potential (energy) and momentum.

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On what factors does the band gap depends?

The band gap energy of semiconductors tends to decrease with increasing temperature. When temperature increases, the amplitude of atomic vibrations increase, leading to larger interatomic spacing. The interaction between the lattice phonons and the free electrons and holes will also affect the band gap a little.

What are direct and indirect bandgap semiconductors which of them is preferred for LEDs and why?

In direct band gap semiconductors like gallium nitride most of these electrons are in the trough of the conduction band and may move to the valence band without any change in momentum from a phonon. For these reasons indirect semiconductors are not likely to be used for LEDs.

What are the direct band gap and indirect band gap semiconductors?

The band gap represents the minimum energy difference between the top of the valence band and the bottom of the conduction band, However, the top of the valence band and the bottom of the conduction band are not generally at the same value of the electron momentum.

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What is an indirect bandgap?

An indirect band gap is where the maximum of the valence band and the minimum of the conduction band occur at different values of k. The maximum of the valence band is at k = 0, but the minimum in the conduction band is at a k vector on the Brillouin zone boundary.

What is direct bandgap?

In a direct band gap semiconductor, the top of the valence band and the bottom of the conduction band occur at the same value of momentum, as in the schematic below. Each photon of energy E has momentum p = E / c, where c is the velocity of light.

What is band gap in materials?

The band gap is the minimum amount of energy required for an electron to break free of its bound state. When the band gap energy is met, the electron is excited into a free state, and can therefore participate in conduction.

What is the basic difference between optical band gap and electrical band gap?

Electrical band gap is the minimal energy required to create an electron hole pair in a semiconductor, whereas optical band gap is the exciton energy which determines the onset of vertical interband transitions.

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What are indirect semiconductors?

Examples of “indirect” semiconductors are Si, Ge, and GaP. In this case, the transition between the maximum of valence band to the minimum of the conductive band is not possible with only the absorption of photon with energy hν close to the bandgap Wg.