Subband occupancies and zero-field spin splitting in InSb-CdTe heterojunctions: magnetotransport experiments and self-consistent calculations

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Abstract
A variety of magnetotransport measurements have been performed on InSb-CdTe heterojunctions containing high mobility ( approximately 20000 cm2 V-1 s-1) two-dimensional electron gases (2DEGS) with low area carrier densities (Ns approximately 1.8-4.2*1011 cm-2). The experimental data have been compared with self-consistent calculations of the energy levels carried out using the 'three-band' model of narrow-gap semiconductors. The 2DEGS in the samples exhibit well resolved quantum Hall plateaux and Shubnikov-de Haas oscillations at temperatures below 5 K; using these data and the persistent photoconductivity (PPC) effect, the subband occupancies have been evaluated as functions of Ns. Parallel-field magnetoresistance measurements show that only two subbands are occupied, even at the highest carrier densities, and indicate the importance of intersubband scattering. The self-consistent calculations predict the number of occupied subbands correctly, and are in agreement with the experimental subband occupancies when the effects of a small amount of interdiffusion are taken into account. The low-field magnetoresistance of the heterojunctions is at first positive and then negative; this is characteristic of weak localization in the presence of spin-orbit scattering.