Magnetic-field-guided motion of electrons in a bulk semiconductor

Abstract
The free-electron cyclotron resonance in n-GaAs with rather weak impurity doping in a regular sequence of sheets shows a strong dependence of the carrier scattering rate on the direction of the applied magnetic field B. For the case of B directed exactly along the sheets we find a linewidth narrowing of more than a factor of 4. This effect is due to the B aligned trajectory of the circling electrons which extends along, but outside of the doping sheets. Our experiment is the direct observation of an anisotropic distribution of scatterers in an otherwise isotropic semiconductor.