Spin physics and transport in narrow-gap III-V based heterostructures and epilayers

mixing of the first subband SdH series and a magneto-intersubband oscillation, the onset of which occurs when the Fermi energy is close to the bottom of the second subband. It is only at the lowest concentrations where the well asymmetry is minimal that beat patterns due to two narrowly split SdH series are observed. This splitting energy is found to be dependent on magnetic field, dropping from approx 4.8 meV at B = 0 T to approx 3.2 meV at B 1.3 T. In contrast, no beating is found in gated InAs/AISb wells at 4.2K over the largest concentration range yet reported in a single sample (4.8x10 sup 1 sup 1 cm sup - sup 2 < n < 2.4x10 sup 1 sup 2 cm sup - sup 2). The Heusler alloy NiMnSb is identified as a candidate for an electrical spin injector for InAs. A simple technique for the fabrication of bulk NiMnSb targets for laser ablation is detailed, and attempts at laser ablation of NiMnSb thin films are reported. Oxygen is identified as the major contaminant for the production of stoichiometric films. High electric field Hall measurements on InAs and InSb epilayers grown on GaAs show that electron energy loss at high fields occurs via plasmon, coupled plasmon-phonon and optical phonon emission, even in intrinsic inSb at 300 K. A simple 'catchment' model based on these energy loss mechanisms is developed and provides an excellent fit to mu(E), the mobility variation with applied electric field. Using this model, an estimate of the plasmon cutoff wavelength to within approx 10 % is possible for weakly degenerate or degenerate electron gases. An increase in the carrier concentration up to a factor of 3 is observed at high fields, and demonstrates that estimates of the saturation drift velocity made using I-V curves and an assumption of constant carrier concentration are invalid in these materials. It is commonly assumed that the beat patterns observed at low temperatures in the quantum magneto-resistance (QMR) of many high mobility semiconductor heterostructures are due to the presence of two Shubnikov-de Haas (SdH) series of slightly differing periods. The appearance of a second series is attributed to a 'Zero Field Spin Splitting' arising from the quantum well potential (Rashba) asymmetry and the beat pattern is used to derive a value for the spin-orbit coefficient (alpha sub 0). We present QMR measurements on gated InAs/GaSb quantum wells over an extended temperature range, 0.4 K < T < 31 K. At high carrier concentrations, a beating is observed which arises from