Excitation energy evolution of photoluminescence spectrum in amorphous hydrogenated silicon

Fujisaki

Nomura

2008

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Monte Carlo simulation of hopping‐randomwalk at localized band tail states with the exponential density has been executed. The mean square hopping distance of electrons and the average density of electrons at the starting site after s steps are shown to be given by ∼ sα and ∼ s–γ, respectively. The exponents α andγ increase with temperature and reach 1 and 3/2 at high temperatures, respectively. α is shown to be equal to the dispersion parameter, αi, at short time in the time‐of‐flight experiment. The temperature behaviour of α are shown to agree with that of αi in amorphous hydrogenated silicon (a‐Si:H) observed in the electric field lower than 1×104 V/cm. The average depth of electrons and holes in the exponential tail increases with steps and thermally balance at an energy, which is named the hopping‐edge. The temperature dependence of the hopping‐gap, which means the energy difference between electron and hole hopping‐edges, agrees with that obtained from the excitation energy dependence of the luminescence peak energy in a‐Si:H. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Comparison With Experimentssupporting

confidence: 54%

Section: Calculationmentioning

confidence: 99%

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Electron hopping‐randomwalk at localized band tail states with exponential density in amorphous hydrogenated silicon

Fujisaki

Nomura

2008

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“…This means that electrons and holes excited in conduction and valence bands in a-Si:H arrive promptly at mobility edges by emitting phonons, then lose the energy through hopping between localized band tail states and thermally balance at an energy. Therefore, the energy is named the hopping-edge [3]. Photocarriers move near the hopping-edges of valence and conduction bands by the hopping, and electron-hole pairs photoexcited recombine radiatively near the hopping-edges.…”

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confidence: 99%

“…We have researched on the hopping-gap in a-Si:H [3] ,which is the energy difference between hopping-edges of electron and hole, by measuring the excitation energy dependence of the luminescence peak energy. Furthermore, we have discussed the origin of the luminescence center from the excitation energy dependence.…”

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confidence: 99%

Temperature dependence of hopping‐edge in amorphous hydrogenated silicon

Hoshino

Ogiwara

2008

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Luminescence peak energy of amorphous hydrogenated silicon (a‐Si:H) increases with excitation energy in the Urbach tail and in the higher excitation energy range the peak energy is constant. The excitation energy at which the peak energy turns from increase to constant is shown to be understood as the hopping‐gap. The hopping‐gap decreases with temperature as in the case of the optical bandgap. Furthermore, it is discussed by comparing with the luminescence in porous Si that the luminescence in a‐Si:H may be due to the radiative recombination of electron‐hole pairs in hydrogen‐free Si nanostructures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Luminescence from hydrogen‐free silicon nanostructures in amorphous hydrogenated silicon

Monji

Deki

2010

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