Spin Gratings and the Measurement of Electron Drift Mobility in Multiple Quantum Well Semiconductors

A direct optical measurement of electron drift mobility in multiple quantum well semiconductors is achieved by creating electron spin gratings in time-resolved degenerate four-wave mixing measurements. Grating decay rates are measured for spin and concentration gratings in a GaAs $/$AlGaAs sample at room temperature, giving an in-well electron diffusion coefficient $D_e=127\mathrm{}{\mathrm{cm}}^2/\mathrm{s}$ compared with an ambipolar coefficient $D_a=13.3\mathrm{}{\mathrm{cm}}^2/\mathrm{s}$.