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

Abstract

We have studied 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 (SdH) 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 subbands exhibit a strong anomalous negative magnetoresistance, reaching ≈ 25% of a zero field value at B = 12 T. The decrease of resistance 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.