Negative Absolute Mobility of Holes in n-Doped GaAs Quantum Wells.

We observe the effect of negative absolute mobility for minority holes in n-modulation-doped GaAs quantum wells at low temperatures. Photoinjected minority holes drift towards the positive electrode, which is shown experimentally using a photoluminescence imaging technique. The effect is attributed to "carrier drag" by the high-mobility electron plasma via electron-hole scattering. From a quantitative analysis we are able to determine electron- hole momentum relaxation times.