Realization of In0.75Ga0.25As two-dimensional electron gas bilayer system for spintronics devices based on Rashba spin-orbit interaction

Narrow gap InGaAs two-dimensional electron gas (2DEG) bilayer samples are fabricated and confirmed to have good electronic qualities as well as strong Rashba-type spin-orbit interactions (SOIs). The 2DEG systems are realized by molecular beam epitaxy in the form of wide quantum wells (QWs) with thicknesses t(QW) similar to 40-120 nm modulation doped in both the upper and lower InAlAs barriers. From the Hall measurements, the overall mobility values of mu(e) similar to 15 m(2)/V s are found for the total sheet electron density of n(s) similar to 8 x 10(11)/cm(2), although the ns is distributed asymmetrically as about 1:3 in the upper and lower 2DEGs, respectively. Careful low temperature magneto-resistance analysis gives large SO coupling constants of alpha similar to 20 x 10(-12) eV m as well as expected electron effective masses of m*/m(0) similar to 0.033-0.042 for each bilayer 2DEG spin sub-band. Moreover, the enhancement of alpha with decrease of t(QW) is found. The corresponding self-consistent calculation, which suggests the interaction between the bilayer 2DEGs, is carried out and the origin of alpha enhancement is discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766749]