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Title: Influence of the SiO{sub 2} interlayer thickness on the density and polarity of charges in Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks as studied by optical second-harmonic generation

By accurately tuning the SiO{sub 2} interlayer thickness the density and polarity of charges in Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks can be controlled. We report on the number density, polarity, and physical location of charges present in the stacks as studied by optical second-harmonic generation (SHG). Depending on the SiO{sub 2} interlayer thickness (1–150 nm) the effective charge density in the Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks ranges from 10{sup 13} to 10{sup 11} cm{sup −2} for both n- and p-type silicon. The polarity of the charges switches from negative to positive around a SiO{sub 2} interlayer thickness of 5–10 nm at which point the effective charge density in the stacks is negligible. This switch in polarity is apparent from spectroscopic, time-dependent, and azimuthal SHG measurements. The observed trends in charge density and polarity can be explained by tunneling of electrons into defect states at the SiO{sub 2}/Al{sub 2}O{sub 3} interface as well as the presence of fixed and bulk charges at the Si/SiO{sub 2} interface and in the SiO{sub 2}, respectively. This charge mechanism appears to hold generally for Si/SiO{sub 2}/Al{sub 2}O{sub 3} stacks as similar results were observed for SiO{sub 2} films prepared by various techniques.
Authors:
; ; ; ;  [1]
  1. Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
Publication Date:
OSTI Identifier:
22275747
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM OXIDES; CHARGE DENSITY; DENSITY; EFFECTIVE CHARGE; ELECTRONS; HARMONIC GENERATION; HETEROJUNCTIONS; INTERFACES; SILICON; SILICON OXIDES; THICKNESS; THIN FILMS; TIME DEPENDENCE; TUNNEL EFFECT