Spectroscopic ellipsometric characterization of Si/Si1-xGex strained-layer supperlattices

H. Yao, J. A. Woollam, P. J. Wang, M. J. Tejwani, S. A. Alterovitz

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Spectroscopic ellipsometry (SE) was employed to characterize Si/Si1-xGex strained-layer superlattices. An algorithm was developed, using the available optical constants measured at a number of fixed x values of Ge composition, to compute the dielectric function spectrum of Si1-xGex at an arbitrary x value in the spectral range 1.7 to 5.6 eV. The ellipsometrically determined superlattice thicknesses and alloy compositional fractions were in excellent agreement with results from high-resolution X-ray diffraction studies. The silicon surfaces of the superlattices were subjected to a 9 : 1 HF cleaning prior to the SE measurements. The HF solution removed silicon oxides on the semiconductor surface, and terminated the Si surface with hydrogen-silicon bonds, which were monitored over a period of several weeks, after the HF cleaning, by SE measurements. An equivalent dielectric layer model was established to describe the hydrogen-terminated Si surface layer. The passivated Si surface remained unchanged for > 2 h, and very little surface oxidation took place even over 3 to 4 days.

Original languageEnglish (US)
Pages (from-to)52-56
Number of pages5
JournalApplied Surface Science
Volume63
Issue number1-4
DOIs
StatePublished - Jan 1993

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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