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The problem of preparing high-mobility thin InSb films is revisited for magnetoresistive and spintronic sensor applications. We introduce a growth process that significantly improves the electrical properties of thin unintentionally doped InSb layers ͑60-300 nm͒ epitaxially grown on GaAs͑100͒ substrates by reducing the density of dislocations within the interfacial layer. The epilayer properties are well described by a differential two-layer model. This model confirms that the contribution of the interface can only be donor-like. Moreover, the electrical properties of the InSb layers change continuously away from the interface up to sample thickness of the order of 1 m.

We have used time-resolved spectroscopy to measure the relaxation of spin polarizations in the narrow gap semiconductor material n-InAs as a function of temperature, doping, and pump wavelength. The results are consistent with the D'Yakonov-Perel mechanism for temperatures between 77 and 300 K. However, the data suggest that electron-electron scattering should be taken into account in determining the dependence of the spin lifetime on the carrier concentration in the range 5.2ϫ 10 16 − 8.8ϫ 10 17 cm −3 . For a sample with doping of 1.22ϫ 10 17 cm −3 the spin lifetime was 24 ps at room temperature. By applying a magnetic field in the sample plane we also observed coherent precession of the spins in the time domain, with a g factor g * = −13, also at room temperature.

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We address the inherent high-field magnetoresistance ͑MR͒ of indium antimonide epilayers on GaAs ͑001͒, studying the modification of the MR when processed into a set of geometries. The changes produced by the geometries are quite subtle. The extraordinary MR geometry produces the highest low-field MR while the Corbino geometry produces the largest high-field magnetoresistance. We demonstrate that any material with an unsaturating linear intrinsic MR, will also have an unsaturating linear Corbino MR, and that the ideal material for linear MR sensors in conventional geometries would have a high mobility and a small, linear intrinsic MR.