Light Emission from Impurity Centres and Urbach's Rule

Lubchenko, A. F.; Dudkin, S. I.

doi:10.1002/pssb.19700400104

Physica Status Solidi (b)

1970

DOI: 10.1002/pssb.19700400104

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Light Emission from Impurity Centres and Urbach's Rule

A. F. Lubchenko

S. I. Dudkin

Abstract: An investigation is made of the shape of the emission spectra due to impurity centres in a solid, taking into account the variation of its quasi-elastic constants during the phototransitions. A formula for the short-wavelength edge of the emission spectrum similar to the Urbach expression for absorption is obtained.Es wird die Linienform der Emissionsspektren von Fremddefektzentren in Festkorpern untersucht, wobei die Anderungen der quasielastischen Konstanten wiihrend des Photoiibergangs berucksichtigt werden… Show more

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Cited by 6 publications

(2 citation statements)

References 17 publications

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“…Quite naturally, the Urbach emission spectrum should have mirror symmetry t o the absorption spectrum [23]. The value i7 = 0.33, obtained from our experimental data (uncorrected for reabsorption) is rather close t o the value (r = 0.46 obtained by Parsons et al [7] from absorption spectra of CdSe a t T = 300 OK.…”

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confidence: 85%

Hot‐exciton luminescence in CdSe crystals

Groß

Permogorov

Morozenko

et al. 1973

Physica Status Solidi (b)

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The emission spectra of CdSe crystals under the excitation in the region of fundamental absorption with the He-Ke laser line 3, = 6328 A have been studied at temperatures 4.2 t o 300 OK. A set of narrow emission lines shifted by the energies of an integer number of LO phonons to lower energies from the exciting line has been observed in the region of fundamental absorption. No emission line has been observed a t the posit,ion shifted by 1 LO. The intensity of LO-shifted lines drastically decreases with increasing crystal temperature. It is shown that this temperature dependence and the comparable intensity of multiphonon lines cannot be explained on the basis of a resonant ltaman scattering model. The observed line emission was assigned to a luminescence of hot excitons. The latter model can explain both thermal quenching of emission and intensity distribution in the spectrum. I n the emission spectra of mechanically polished samples a defect activated 1 LO emission line has been observed. This line is due to the indirect exciton transitions without phonon participation in the partially disordered surface layer. Besides the line structure, the continuous emission background has been observed in the region of fundamental absorption. This background forms t,he high energy exponential tail of the quasi-equilibrium exciton emission line n = 1 A and can be considered as Urbach region of t,he exciton emission spectrum.Es wurden die Emissionsspektren von CdSe-Kristallen bei Anregung im Bereich der Grundgitterabsorption mit der He-Nc-Laserlinie 1 = 6328 A im Temperatnrbereich 4,2 bis 500 OK untersucht. Eine Anzahl von schmalen Emissionslinien, deren Energie um ganzzahlige Vielfache der LO-Phononen yon der Anregungslinie zu niedrigen Energien verschoben sind, wurden im Gebiet de,r Crundgitterabsorption heobachtet. Am Ort der Verschiebung urn 1 LO wurde keine Emissionslinie beobachtet. Die Intensitat der LOverschobenen Linien nimmt stark mit steigcnder Kristalltemperatur ab. Es wird gezeigt, dall die Temperaturabhangigkeit und die relat,ive Intensitit der Multiphononlinien auf der Basis eines resonanten Itaman-Streuungsmodells nicht erkliirt werden konnen. Die beobachtete Linienemission wird als Lumineszenz heiBer Exzitonen angesehen. Das letztere Model1 kann sowohl die thermische Tilgung der Emission als auch die Intensitiitsverteilung des Spektrums erklaren. I m Emissionsspektrum von mechanisch polierten Proben wurde eine storstellenaktivierttc 1 LO-Emissionslinie beobachtet. Diese Linie riihrt von indirekten Exzitonenubergiingen ohne Phononenbeteiligung in der teilweise fehlgeordneten Oberflachenschicht her. Xeben der Linienstruktur wurde der kontinuierliche Untergrund im Bereich der Grundgitterabsorption untersucht. Dieser Untergrund bildet den hochenergetischen exponentiellen Auslaufer der Quasigleichgewichts-Exzitonenemissionslinie n = 1 A und kann als Urbach-Bereich des Exzitonen-Emissionsspcktrums angesehen werden.

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supporting

confidence: 85%

Hot‐exciton luminescence in CdSe crystals

Groß

Permogorov

Morozenko

et al. 1973

Physica Status Solidi (b)

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“…papers (8 to 11) in the Einstein approximation to normal vibration frequencies; later on this expression has been generalized (12) to the case of their weak dispersion.…”

mentioning

confidence: 99%

Urbach's rule with the dispersion of frequencies

Lubchenko

Fishuk

1971

Physica Status Solidi (b)

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Institute of Theoretical Physics, Academy of Sciences of the Ukrainian SSR, Kiev Urbac h' s Rule with the Dispersion of Frequencies BY A. F. LUBCHENKO and I. I. FISHUK As is known, the shape of the long-wavelength edge of light absorption by localized excitations and excitons is well described by the formula Gj w 2kT ' d = Q ~t h -Consequently , i =-4 7 Q-%} . 1 B r e they ar ! This expression is analogous to formula (1); the temperature dependence of d is the same as in paper (13). The value of e is defined by the character of the fre-K14 physica status solidi (b) 48quency dispersion of w . SAn analogous expression defines, too, the shape of the short-wavelength e m i s sion edge (if the signis substituted for + before ( Q -3 )).

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Urbach rule

Kurik

1971

Phys. Stat. Sol. (a)

567

251

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Light Emission from Impurity Centres and Urbach's Rule

Cited by 6 publications

References 17 publications

Hot‐exciton luminescence in CdSe crystals

Hot‐exciton luminescence in CdSe crystals

Urbach's rule with the dispersion of frequencies

Urbach rule

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