File Name: direct and indirect band gap .zip
Metrics details. Electronic structures of monolayer InSe with a perpendicular electric field are investigated. Indirect-direct-indirect band gap transition is found in monolayer InSe as the electric field strength is increased continuously. Meanwhile, the global band gap is suppressed gradually to zero, indicating that semiconductor-metal transformation happens. The underlying mechanisms are revealed by analyzing both the orbital contributions to energy band and evolution of band edges. These findings may not only facilitate our further understanding of electronic characteristics of layered group III-VI semiconductors, but also provide useful guidance for designing optoelectronic devices.
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 valence band, VB maxima and the bottom of the conduction band conduction band minima, CB minima are not generally at the same value of the electron momentum. Minimum-energy state in the conduction band CB -minima and the maximum-energy state in the valence band VB-maxima are each characterized by a certain crystal momentum and k- vector propagation constant or wave vector in the Brillouin zone. In direct band gap semiconductor Energy is conserved by means of emitting a photon, such transitions are called as radiative transitions. Relative carrier life time is small in case of direct band gap semiconductor. In this case momentum is not same for conduction band minima CB-minima and valence band maxima VB —maxima.
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. 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. In an indirect band gap semiconductor , the maximum energy of the valence band occurs at a different value of momentum to the minimum in the conduction band energy:. The difference between the two is most important in optical devices. As has been mentioned in the section charge carriers in semiconductors , a photon can provide the energy to produce an electron-hole pair. A photon of energy E g , where E g is the band gap energy, can produce an electron-hole pair in a direct band gap semiconductor quite easily, because the electron does not need to be given very much momentum. However, an electron must also undergo a significant change in its momentum for a photon of energy E g to produce an electron-hole pair in an indirect band gap semiconductor.
In semiconductor physics , the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap.
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