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No-Phonon and Phonon-Assisted Indirect Transitions in Si1−xGex Single Crystals

Published online by Cambridge University Press:  10 February 2011

A. Gerhardt
A. Gerhardt*
Affiliation:
Institut fur Kristallzüchtung, D-12489 Berlin, Rudower Chaussee 6, Germany FAX: +049 (30) 63923003 Phone: +49 (30) 63923091 e-mail: donecker@ikz-berlin.de
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Abstract

The absorption properties of high quality bulk Si1−xGex single crystals (0 ≤ × ≤ 0.16) are studied. Transmission measurements were performed at the indirect absorption edge. The shape of the absorption edge is characterized by structures attributed to the onset of no-phonon and phonon-assisted indirect optical transitions. Threshold energies have been determined using a differential method. A corrected calibration function for the dependence of the excitonic energy gap on composition is presented for the compositions, where x ranges from 0 to 0.16. The presented calibration function can be used for the composition analysis by an optical method. The analysis is independent of absolute transmission values.

A simulation of the absorption spectra by calculations based on second order perturbation theory was used to fit the experimental data This procedure allows to estimate the oscillator strength of the no-phonon transition in dependence on x.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 450: Symposium O – Infrared Applications of Semiconductors , 1996 , 451
Copyright
Copyright © Materials Research Society 1997

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References

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