Variable-range hopping transport in modulation-doped n-channel Si/Si1-xGex quantum well structures

D. H. Shin, C. E. Becker, J. J. Harris, J. M. Fernández, N. J. Woods, Trevor Thornton, D. K. Maude, J. C. Portal

Research output: Contribution to journalArticle

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Abstract

We have measured the temperature- and field-dependent longitudinal conductivity, σxx, in the Landau level tails of two modulation-doped Si/Si1-xGex two-dimensional electron gas samples at temperatures below 1 K. The temperature dependence of σxx at the minima of the Shubnikov-de Haas oscillations obeyed a relation of the form σxx min (T) ∝ (1/T) exp[-(T0T) 1/2 ], in agreement with published models of variable-range hopping between localized states by Ono and by Polyakov and Shklovskii. However, the value and magnetic field dependence of the characteristic temperature, T0, cannot be explained quantitatively on Ono's model, which is based on Gaussian localization of the electron wavefunction on a scale given by the magnetic length. Polyakov and Shklovskii used exponential wavefunctions to derive an alternative expression for the characteristic temperature, and to model the conductivity in the vicinity of the peaks between adjacent quantum Hall plateaux. Our results have been analysed according to this theory, and show good agreement: the magnetic field dependence of the corresponding characteristic temperature, T1 (v), obeys the power law relation. T1 ∝ (Δv)γ, as expected from theory, while the experimental value of γ, 0.90 ± 0.07, agreed with that determined from a half-width analysis of the σxx peaks; however, this value differs from the theoretically predicted figure of approx. 2.3.

Original languageEnglish (US)
Pages (from-to)762-767
Number of pages6
JournalSemiconductor Science and Technology
Volume14
Issue number9
DOIs
StatePublished - Sep 1999

Fingerprint

Semiconductor quantum wells
Modulation
quantum wells
modulation
Wave functions
Temperature
temperature
conductivity
Magnetic fields
Two dimensional electron gas
magnetic fields
electron gas
plateaus
temperature dependence
oscillations
Electrons
electrons

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Materials Science(all)
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Variable-range hopping transport in modulation-doped n-channel Si/Si1-xGex quantum well structures. / Shin, D. H.; Becker, C. E.; Harris, J. J.; Fernández, J. M.; Woods, N. J.; Thornton, Trevor; Maude, D. K.; Portal, J. C.

In: Semiconductor Science and Technology, Vol. 14, No. 9, 09.1999, p. 762-767.

Research output: Contribution to journalArticle

Shin, D. H. ; Becker, C. E. ; Harris, J. J. ; Fernández, J. M. ; Woods, N. J. ; Thornton, Trevor ; Maude, D. K. ; Portal, J. C. / Variable-range hopping transport in modulation-doped n-channel Si/Si1-xGex quantum well structures. In: Semiconductor Science and Technology. 1999 ; Vol. 14, No. 9. pp. 762-767.
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