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Transport in High-Mobility Si1−xGex Heterostructures Grown by Molecular-Beam Epitaxy

Published online by Cambridge University Press:  25 February 2011

Don Monroe ,
Y.-H. Xie ,
E. A. Fitzgerald  and
P. J. Silverman
Don Monroe
Affiliation:
AT&T Bell Laboratories, P.O. Box 636, Murray Hill, NJ 07974
Y.-H. Xie
Affiliation:
AT&T Bell Laboratories, P.O. Box 636, Murray Hill, NJ 07974
E. A. Fitzgerald
Affiliation:
AT&T Bell Laboratories, P.O. Box 636, Murray Hill, NJ 07974
P. J. Silverman
Affiliation:
AT&T Bell Laboratories, P.O. Box 636, Murray Hill, NJ 07974
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Abstract

We report Hall mobilities (at T = 4.2K) as high as 180,000cm2V−1 s−1 in modulation-doped Si layers in Si1−x Gex heterostructures grown by Molecular-Beam Epitaxy. These mobilities reflect dramatic improvements in the quality of relaxed Si1−xGex buffer layers (with x'30%) grown by gradual grading of composition at high temperature. The resulting moderate threading dislocation densities (< 106 cm−2 ) appear to cause no mobility degradation. The strong damping of Shubnikov de Haas oscillations, as well as the increase of mobility with carrier density, indicate predominantly small-angle scattering. This suggests that residual Coulomb scattering from background impurities limit the mobility, rather than interface-roughness scattering as for the Si/SiO2 interface. The reduced interfacial scattering, as well as the strain-induced splitting of the valley degeneracy to select the two low-effective-mass valleys, significantly enhance room-temperature transport as well, with μHall ' 2,100cm2 V−1 s−1. We also observe a small splitting of the remaining twofold valley degeneracy using the integral quantized Hall effect. As a further indication of the high sample quality, measurements to 17T at 0.3K show indications of the v = 2/3 fractional quantum Hall effect.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 281: Symposium D – Semiconductor Heterostructures for Photonic and Electronic Applications , 1992 , 449
Copyright
Copyright © Materials Research Society 1993

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References

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