  We report on the observation of the magneto-photogalvanic effect (MPGE) due
to inter-subband transitions in (001)-oriented GaAs quantum wells. This effect
is related to the gyrotropic properties of the structures. It is shown that
inter-subband absorption of linearly polarized radiation may lead to
spin-related as well as spin independent photocurrents if an external magnetic
field is applied in the plane of the quantum well. The experimental results are
analyzed in terms of the phenomenological theory and microscopic models of MPGE
based on either asymmetric optical excitation or asymmetric relaxation of
carriers in k-space. We observed resonant photocurrents not only at oblique
incidence of radiation but also at normal incidence demonstrating that
conventionally applied selection rules for the inter-subband optical
transitions are not rigorous.
