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Space Charge Layers at the Porous Silicon Surface

Published online by Cambridge University Press:  26 February 2011

S. Z. Weisz ,
J. Avalos ,
M. Gomez ,
A. Many ,
Y. Goldstein  and
E. Savir
S. Z. Weisz
Affiliation:
Department of Physics, University of Puerto Rico, Rio Piedras, PR 00931
J. Avalos
Affiliation:
Department of Physics, University of Puerto Rico, Rio Piedras, PR 00931
M. Gomez
Affiliation:
Department of Physics, University of Puerto Rico, Rio Piedras, PR 00931
A. Many
Affiliation:
Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
Y. Goldstein
Affiliation:
Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
E. Savir
Affiliation:
Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
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Abstract

Pulse measurements on the porous-Si/electrolyte system are employed to determine the surface effective area and the surface-state density at various stages of the anodization process used to produce the porous material. Such measurements were combined with studies of the luminescence spectra and scanning tunneling microscopy (STM). Both the effective area and the luminescence intensity are found to increase with anodization time, reaching maximum values for the same anodization time (1–2 minutes). In most cases, they decrease monotonically with further anodization. The surface state density, on the other hand, decreases with anodization time from the initial value of ∼1012 cm−2 for the virgin surface, down to ∼1011 cm−2 at the common anodization time for which both the effective area and the luminescence intensity are peaked. The surface-state density increases upon further anodization, reaching a value of at least 1013 cm−2 after ∼10 minutes of anodization. Apart from its intensity, the luminescence spectrum is essentially independent of anodization time. The common peak of the spectra is at about 700 nm. The STM measurements reveal a pronounced surface roughness. Preliminary results indicate that for 1 - 2 minute anodization (maximum effective area), the roughness scale is of the order of 1 -2 nm. After 10-minutes anodization, on the other hand, the roughness microstructure becomes finer (roughness scale of only 0.5 - 0.7 nm). These findings indicate that the various characteristics studied are closely interrelated. Such information may help in understanding the luminescence mechanism, but further work is required in order to interpret more fully the results presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 378: Symposium B – Defect and Impurity-Engineered Semiconductors and Devices , 1995 , 899
Copyright
Copyright © Materials Research Society 1995

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