Magnetotransport with two occupied subbands in a Si(100) inversion layer

TL;DR

This study investigates magnetotransport phenomena in high-mobility Si(100) inversion layers, revealing two occupied subbands, anomalous negative magnetoresistance, and inhomogeneous electron distribution, with implications for understanding subband dynamics at low temperatures.

Contribution

It provides new insights into the behavior of two occupied subbands in Si(100) inversion layers, including their impact on magnetoresistance and electron mobility at low temperatures.

Findings

Observation of two series of Shubnikov-de Haas oscillations.

Strong negative magnetoresistance up to 25%.

Inhomogeneous electron distribution beneath the gate.

Abstract

We have studied an electron transport in inversion layers of high-mobility Si(100) samples. At high electron concentrations and temperatures below 4.2 K, two series of Shubnikov-de Haas oscillations have been observed. The temperature damping of the second series oscillations indicates that the second occupied subband belongs to the first energy level of the fourfold-degenerate ladder $0'$. Samples with two occupied subbans exhibit a strong anomalous negative magnetoresitance, reaching $\rm \approx 25 \%$ of a zero field value at $B =$ 12 T. The resistance decrease is more pronounced for lower temperatures and higher electron concentrations. We explain this behaviour by an increase of the second subband mobility due to the freezing-out of the scattering of $0'$ electrons. Based on the measured periods of SdH oscillations, we conclude that the electrons are distributed inhomogeneously beneath the sample gate.