Semiconductor Physics, Quantum Electronics & Optoelectronics. 2002. V. 5, N 1. P. 9-15.

PACS: 78.67. Bf, 78.67.Hc

Urbach’s rule peculiarities in structures with CdS_XSe_1-X nanocrystals
V.P. Kunets, N.R. Kulish, Vas.P. Kunets, M.P. Lisitsa

Institute of Semiconductor Physics, NAS of Ukraine, 45 prospect Nauky, 03028 Kyiv, Ukraine
Phone: +380 (44) 265 6282

Abstract. We have found that the long wavelength fundamental absorption edge of CdS_XSe_1-X nanocrystals grown in an oxide glass follows to the generalized Urbach rule that takes into account both the dynamic (phonon induced) and static (defect induced) disorders of nanocrystal lattice. Temperature intervals with the dominant influence of both disorders on the absorption edge were determined. We have also estimated Urbach rule constants comparing them with the bulk ones. Using various Urbach`s rule theories we analyzed the most considerable changes of nanocrystal parameters when their sizes are decreased down to the quantum scale. It was found that the exciton-phonon coupling constant and exciton localization one are increased; the average electric fields induced by phonons and charged point defects are also increased.

Keywords: Urbach’s rule, absorption, nanocrystal, quantum confinement.
Paper received 20.02.02; revised manuscript received 05.03.02; accepted for publication 05.03.02.

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