How can the indirect and direct band gap can be identified by practical observation using any spectroscopy techniques or any other techniques.
Faisal what if both responds to tauc plot.. How to identify or stick the material as direct band gap or indirect band gap?
An optical band-gap should normally correspond to a direct band gap transition, as indirect transitions are forbidden.
So many papers are available. Try with Tauc Plot and Kubleka-Munk Equation. Good Luck.
Dear Dr. Issac
Direct and indirect band gaps:
In semiconductor physics, the band gap of a semiconductor is always one of two types, a direct band gap or an indirect band gap.
The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone. If the k-vectors are the same, it is called a "direct gap".
If they are different, it is called an "indirect gap".
The band gap is called "direct" if the momentum of electrons and holes is the same in both the conduction band and the valence band; an electron can directly emit a photon. 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.
From the free encyclopedia
those semiconductor whose top of the valence band and botton of conduction band lies as same k- value called as direct semiconductor and lies at different k- values are called indirect band gap semiconductor. energy vs (alfa* hv)^n, n=2 for direct band gap and n=0.5 for indirect band gap.
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