Effect of Anharmonicity on Urbach's Exponential Tail in Amorphous Semiconductors

Bhatia, K.L.; Bhat, Pawan

doi:10.1002/pssb.2220620133

Cited by 7 publications

(2 citation statements)

References 14 publications

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“…However, the temperature-dependent slope of the Urbach edge of v-SiO, (Fig. 3a)can be interpretedin terms of the model of [20,21], which leads to the conclusion that in v-SiO, the LO phonons are the dominant sources for the broadening of the Urbach edge. The difficulty with the application of the model of DOW and Redfield [12] and of other internal-field theories [22,23] to v-SiO is the same as for c-SiO,; they cannot explain the temperature dependence (2) in a quantitative manner.…”

Section: Vitreous Siomentioning

confidence: 99%

Exciton–phonon interaction in crystalline and vitreous SiO₂

Godmanis

Trukhin

Hübner

1983

Physica Status Solidi (b)

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An investigation of the Urbach rule in crystalline SiO, (u-quartz), crystalline Si0,-Ge, and vitreous SiO, in the framework of the models of Dow and Redfield and of Toyozawa shows that the fundamental optical absorption edge of SiO, is determined by strong exciton-phonon interactions. I n the crystalline and vitreous SiO, low-energy excitons with E = 9.1 eV (a-quartz) and E = 8.7 eV (glass) interact mainly with longitudinal optical phonons. In the crystalline Si0,-Ge alloy the interaction with phonons is realized by excitons localized on germanium impurities. The exciton-phonon interaction in Si0,-Ge and vitreous SiO, is stronger than in crystalline SiO, due to the higher degree of localization of low-energy excitons in these disturbed SiO, forms. The strong exciton-phonon interaction leads to a momentary self-trapping of the low-energy excitons in crystalline and noncrystalline SiO, and to a corresponding relaxation of the Si0,-Ge excitons localized on Ge impurit,ies. Numerical values of the fundamental exciton parameters are deduced and discussed.Eine Untersuchung der Urbach-Regel in kristallinem SiO, (a-Quarz), kristallinem SiO,-Ge und in Si0,-Glas im Rahmen der Modelle von Dow and Redfield sowie Toyozawa zeigt, da13 die fundamentale optische Absorptionskante von SiO, durch starke Exziton-Phonon-Wechselwirkungen bestimmt wird. I n kristallinem und glasernem SiO, wechselwirken niederenergetische Exzitonen mit E = 9,l eV (a-Qnarz) und E = 8,7 eV (Glas) hauptsachlich mit longitudinalen optischen Phononen. In der kristallinen Si0,-Ge-Verbindung wird die Wechselwirkung mit Phononen durch Exzitonen rertlisiert, die an Germaniumverunreinigungen lokalisiert sind. Die Exziton-Phonon-Wechselwirkung in Si0,-Ge und glasernem SiO, ist infolge der hoheren Lokalisierung der niederenergetisrhen Exzitonen in diesen gestorten Si0,-Formen stirker als im kristallinen SiOz. Die starke Exziton-Phonon-Wechselwirkung fiihrt zu einem augenblicklichen Selbsteinfang der niederenergetischen Exzitonen im kristallinen und nichtkristallinen SiO, und zu einer entsprechenden Relaxation der Si0,-Ge-Exzitonen, die an Ge-Verunreinigungen lokalisiert sind. Numerische Werte der fundamentalen Exzitonparameter werden ermittelt und diskutiert.

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Section: Vitreous Siomentioning

confidence: 99%

Exciton–phonon interaction in crystalline and vitreous SiO₂

Godmanis

Trukhin

Hübner

1983

Physica Status Solidi (b)

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“…These fields are caused by disorder, i.e. they are induced by potential fluctuations due to the lack of long-range order by charged defects [26,27]. The addition of As,O, to the mixture increases the degree of disorder in the system and causes an increase in both the optical energy gap and the widths of the tails of localized states as well as a reduction in the value of the constant…”

Section: The Fundamental Absorption Edgementioning

confidence: 99%

The Spin Density and Optical Properties of Amorphous Thin Arsenic Silicate Films

Al‐Ani¹,

Hogarth²

1984

Physica Status Solidi (b)

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The spin density of amorphous As,O,/SiO thin films is found to be lower than that of SiO films deposited under similar conditions. The measurements show a decrease in the spin density of an amorphous As,O,/SiO film with increasing temperature which can be explained in terms of some annealing of dangling bonds. The fundamental absorption edge of these films a t different temperatures is investigated and analysed assuming optical absorption by indirect transitions. The infrared absorption spectra indicate some chemical bonding between the two oxides. Experimental data on the wavelength dependence of the refractive index are presented. The dispersion of the refractive index follows a single-oscillator model. Some effects of room temperature aging of the films are also presented.La concentration des spins Blectroniques mesurec dans les couches minces de As,O,/SiO est plus basse que dans les couches minces de SiO preparees sous les mdmes conditions. Quand la temperature augmente il y a une decroissance du densite des spins dans une couche mince amorphe de SiO, un resultat qui peut &re explique par consequence de la reparation de la structure des couches minces aprds un traitement B temperature peu Blevee. Les seuils d'absorption des couches minces B quelques temperatures sont mesures et analyses avec la theorie d'absorption optique par les transitions non-directes. Les spectres d'absorption dans la region infra-rouges donnaient l'evidence des jonctions chimiques entre les deux oxydes. Les resultats pour l'indice relative de refraction nf et pour sa variation avec la longueur d'onde, la dispersion de nf en termes d'un moddle monooscillatoire, e t les effets de vieillissement, sont present6es.

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Thermal stability of chalcogenide glasses TeAIV in relation to the atomic number of the AIV element

Lasocka

Matyja

1974

Phys. Stat. Sol. (a)

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On the basis of an analysis of the properties of AIV elements and of their alloys with tellurium, an interpretation is given of the observed regularity involving a rise of the thermal stability of chalcogenide glasses Te0.~,-A0.~5 with a decrease in the atomic number of the AIv element. It is postulated that the thermal stability of these glasses is determined by the entropy of melting of the AIV elemcnt referred t o one atom.

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Effect of Anharmonicity on Urbach's Exponential Tail in Amorphous Semiconductors

Cited by 7 publications

References 14 publications

Exciton–phonon interaction in crystalline and vitreous SiO₂

Exciton–phonon interaction in crystalline and vitreous SiO₂

The Spin Density and Optical Properties of Amorphous Thin Arsenic Silicate Films

Thermal stability of chalcogenide glasses TeAIV in relation to the atomic number of the AIV element

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Effect of Anharmonicity on Urbach's Exponential Tail in Amorphous Semiconductors

Cited by 7 publications

References 14 publications

Exciton–phonon interaction in crystalline and vitreous SiO2

Exciton–phonon interaction in crystalline and vitreous SiO2

The Spin Density and Optical Properties of Amorphous Thin Arsenic Silicate Films

Thermal stability of chalcogenide glasses TeAIV in relation to the atomic number of the AIV element

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Product

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Exciton–phonon interaction in crystalline and vitreous SiO₂

Exciton–phonon interaction in crystalline and vitreous SiO₂