Rashba and Dresselhaus Spin-Splittings in Semiconductor Quantum Wells Measured by Spin Photocurrents

The spin-galvanic effect and the circular photogalvanic effect induced by terahertz radiation are applied to determine the relative strengths of Rashba and Dresselhaus band spin-splitting in (001)-grown GaAs and InAs based two dimensional electron systems. We observed that shifting the $\delta$-doping plane from one side of the quantum well to the other results in a change of sign of the photocurrent caused by Rashba spin-splitting while the sign of the Dresselhaus term induced photocurrent remains. The measurements give the necessary feedback for technologists looking for structures with equal Rashba and Dresselhaus spin-splittings or perfectly symmetric structures with zero Rashba constant.