Molecular beam epitaxy of high mobility $In0.75Ga0.25As$ for electron spin transport applications Available to Purchase

The authors describe the molecular beam epitaxy of relaxed, nominally undoped $In0.75Ga0.25As–In0.75Al0.25As$ quantum well structures grown on InP substrates. The maximum two-dimensional electron density is $2×1011cm−2$⁠, with a peak mobility of $2.2×105cm2V−1s−1$ at $1.5K$⁠. In high magnetic field, the electron $g$-factor was shown to have a magnitude of $9.1±0.1$ at Landau-level filling factor of 4. The Rashba coefficient, determined from the analysis of the magnetoresistance at high Landau-level filling factor $(>12)$⁠, is $1×10−11eVm$⁠. The mobility is sufficiently high in these two-dimensional electron gases that spin-orbit effects are observed up to $4.2K$⁠. The interface asymmetry, defined as the difference between the wavefunction penetration into the upper and lower $In0.75Al0.25As$ quantum barriers, makes no contribution to the Rashba spin-orbit coupling parameter in this system. Quantum wires defined in these two-dimensional electron gases using insulated, split surface gates show clear quarter-integer quantized conductance plateaux at exactly $0.25(2e2∕h)$ and $0.75(2e2∕h)$ in nonequilibrium transport. $In0.75Ga0.25As$ may have important application as an alternative field effect transistor channel to silicon, and the large electronic $g$-factor and Rashba spin-orbit coupling parameter make this material combination suitable for exploring spin related phenomena in one-dimensional systems.