Optical transitions in strained Si_1-yC_y and Si_1-x-yGe_xC_y layers on Si(001)

authored by

H. J. Osten, W. Kissinger, M. Weidner, M. Eichler

Abstract

The addition of carbon atoms into Si or SiGe layers on Si opens the possibility for strain and bandstructure engineering. In this paper we will investigate the influence of carbon on the optical transitions of Si_1-yC_y and Si_1-x-yGe_xC_y layers grown pseudomorphically on Si(001) substrate using solid source MBE including also full strain-compensation. The layers were investigated by spectroscopic ellipsometry and electroreflectance spectroscopy for y ≤ 1.2%. From the numerical derivatives of the measured dielectric constants, we determined the critical points energies E₀′, E₁ and E₂ as a function of the carbon content y. This shift was analyzed by measuring and fitting electroreflectance spectra at 80K and ellipsometry data at room temperature, resulting in a week and nearly linear dependence on the carbon content at all transitions. These dependencies indicate that the interpretation of optical spectra of C-containing alloys can not be performed straightforward by simple interpolating between the appropriate band structures of silicon, germanium and carbon. An analysis based on only strain-induced contributions also does not describe the experimental results correctly. For a description of the observed energy shifts for pseudomorphic Si_1-x-yGe_xC_y we have to consider at least strain-induced effects and effects due to alloying.

External Organisation(s)

Leibniz Institute for High Performance Microelectronics (IHP)

Type

Conference article

Journal

Materials Research Society Symposium - Proceedings

Volume

379

Pages

199-204

No. of pages

6

ISSN

0272-9172

Publication date

1995

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Materials Science, Condensed Matter Physics, Mechanics of Materials, Mechanical Engineering