Bychkov-Rashba dominated band structure in an In0.75Ga0.25As-In0.75Al0.25As device with spin-split carrier densities of <1011 cm-2

We demonstrate that a Bychkov-Rashba dominated band structure can be stabilized in a nominally undoped In0.75Ga0.25As-In0.75Al0.25As quantum well. The transport properties of this system have been measured at 1.7 and 4.2 K and the Rashba coefficient α has been determined in enhancement and depletion modes with an insulated front gate. In enhancement mode, α is 1 x 10-11 eV m with carrier densities ns between 1.4 and 1.9 x 1011 cm-2. In depletion mode, with ns<1.4 x 1011 cm-2, α was reduced to 0.7 x 10-11 eV m. The wavefunction penetration into the In0.75Al0.25As barriers, i.e. the interface asymmetry, makes no contribution to α in this system. We minimize the Zeeman energy spin-splitting in this high g-factor system by analysing only the Shubnikov-de Haas structure below 0.5 T, i.e. for Landau level filling factors >12. The combination of the two spin-split subbands in ρxx can be separated using a magnetic field modulation technique where analogue dρxx/dB or d2ρxx/dB2 signals are measured directly. The In0.75Ga0.25As-In0.75Al0.25As quantum well will have applications both in one-dimensional systems and in gate-induced two-dimensional electron gases where a dominant Bychkov-Rashba spin-splitting is required without the complications of an embedded strained InAs well and without a significant contribution from the interface asymmetry at the In0.75Al0.25As barriers. (fast track communication)