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Electroreflectance Study of Porous Silicon made from Substrates with Different Resistivities

Published online by Cambridge University Press:  17 March 2011

Toshihiko Toyama ,
Yasuharu Nakai  and
Hiroaki Okamoto
Toshihiko Toyama
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka 560-8531, Japan
Yasuharu Nakai
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka 560-8531, Japan
Hiroaki Okamoto
Affiliation:
Department of Physical Science, Graduate School of Engineering Science, Osaka University Toyonaka, Osaka 560-8531, Japan
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Abstract

Employing electroreflectance (ER) spectroscopy, we have studied optical transitions in porous Si (PSi) with a thickness of 100±50 nm made from crystalline Si (c-Si) substrates with different resistivities, 4–10 ωcm (p-), 0.1–1 ωcm (p), and < 0.018 ωcm (p+). The ER features observed at 1.1–2.8 eV in p+ PSi are analyzed with a simple effective mass approximation (EMA) model for confined electron-hole (e-h) pairs in a spherical quantum dot as we have previously done for those observed at 1.2–3.1 eV in p- PSi. From the ER analysis with the EMA model, the effective crystal size is estimated without destruction, and the kinetic energy and the Coulomb attraction energy of the confined e-h pairs are also deduced.

Furthermore, the ER features corresponding to the optical transitions at E1(E0') critical point (CP) are observed at 2.8–3.3 eV in p+ PSi. With an increase in the crystal size, the transition energy of E1(E0') CP in p+ PSi is decreased, while that in p- and p PSi is unchanged from that of 3.4 eV found in c-Si including the p+c-Si. From the Raman results, strain- and disorder-induced spectral changes are found to be negligible, so that the high doping induced effect is the most acceptable mechanism for the red-shift in E1(E0') transitions of Si nanocrystals with the crystal size of 2–3 nm.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 638: Symposium F – Microcrystaline & Nanocrystalline Semiconductors-2000 , 2000 , F3.5.1
Copyright
Copyright © Materials Research Society 2001

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