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Proceedings Paper

Low-frequency non-Gaussian conductance fluctuations in Si near the insulator-metal transition
Author(s): Arup Kumar Raychaudhuri; Swastik Kar; Arindam Ghosh
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Paper Abstract

In this work we review the investigations of conductance fluctuations in doped silicon at low temperatures (2K < T < 20K) as it is tuned through the metal-insulator transition by changing the carrier concentration n. Spectral power, S(f), of the conductance fluctuation retains a generic 1/fα dependence. In the metallic regime (n>nc) the doped Si is like a weakly-localized electron system and the conductance fluctuation is governed by the mechanism of Universal conductance fluctuations. The relative variance of fluctuation follows the temperature dependence ∝ T, where β≈1/2. However, the noise diverges by orders of magnitude as n decreases through the critical concentration nc and the fluctuation also becomes strongly temperature dependent with β>> 1. At the transition (n/nc≈1) the fluctuation becomes strongly non-Gaussian below 20K as observed through the second spectrum S(2)(f). At T=4.2K, we find that after subtracting the Gaussian background , S(2)(f)∝ 1/fp where p is small (< 0.5) for metallic samples (n/nc≥ 1.5) and it grows to > 1 for samples close to the transition n/nc ≈1. The growth of non-Gaussianity is accompanied by a growth in low frequency spectral weight as seen through a significant enhancement of α from close to 1 (n>nc) to nearly 1.4 for n/nc ≈1. The growth of non-Gaussian fluctuation of extremely large magnitude with significant low frequency component points to a correlated low frequency dynamics of charge fluctuation near the insulator-metal transition. This has been interpreted as the onset of a glassy freezing of the electronic system across the transition.

Paper Details

Date Published: 25 May 2004
PDF: 9 pages
Proc. SPIE 5469, Fluctuations and Noise in Materials, (25 May 2004); doi: 10.1117/12.546850
Show Author Affiliations
Arup Kumar Raychaudhuri, Indian Institute of Science (India)
Swastik Kar, Indian Institute of Science (India)
Arindam Ghosh, Indian Institute of Science (India)

Published in SPIE Proceedings Vol. 5469:
Fluctuations and Noise in Materials
Dragana Popovic; Michael B. Weissman; Zoltan A. Racz, Editor(s)

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