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Non-radiative life time is the average time before an electron in the conduction band of a semiconductor recombines with a hole. It is an important parameter in optoelectronics where radiative recombination is required to produce a photon; if the non-radiative life time is shorter than the radiative, a carrier is more likely to recombine non ...
There are several mechanisms by which minority carriers can recombine, each of which subtract from the carrier lifetime. The main mechanisms that play a role in modern devices are band-to-band recombination and stimulated emission, which are forms of radiative recombination, and Shockley-Read-Hall (SRH), Auger, Langevin, and surface recombination, which are forms of non-radiative recombination.
If emission leaves a system in an excited state, additional transitions can occur, leading to atomic radiative cascade. For example, if calcium atoms a low pressure atomic beam are excited by ultraviolet light from their in the 4 1 S 0 ground state to the 6 1 P 1 state, they can decay in three steps, first to 6 1 S 0 then to 4 1 P 1 and finally ...
The fact that radiative recombination is slow in indirect band gap materials also means that, under most circumstances, radiative recombinations will be a small proportion of total recombinations, with most recombinations being non-radiative, taking place at point defects or at grain boundaries. However, if the excited electrons are prevented ...
The dephasing of the polarization leads to creation of populations of electrons and holes in the conduction and the valence bands, respectively. The lifetime of the carrier populations is rather long, limited by radiative and non-radiative recombination such as Auger recombination. During this lifetime a fraction of electrons and holes may form ...
In silicon or germanium diodes, the electrons and holes usually recombine by a non-radiative transition, which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible, or near-ultraviolet light.
Jablonski diagram including vibrational levels for absorbance, non-radiative decay, and fluorescence. When a molecule absorbs a photon, the photon energy is converted and increases the molecule's internal energy level. Likewise, when an excited molecule releases energy, it can do so in the form of a photon.
When that state is either one of strict thermodynamic equilibrium, or one of so-called "local thermodynamic equilibrium", [11] [12] [13] then the distribution of atomic states of excitation (which includes and ) determines the rates of atomic emissions and absorptions to be such that Kirchhoff's law of equality of radiative absorptivity and ...