Theory of the field-assisted photomagnetoelectric effect in thin films: Experiment on n-type GaAs and applications

The field-assisted photomagnetoelectric (FAPME) effect is the generalization of the classical PME effect obtained by the application of a (strong) longitudinal electric field: photogenerated carriers are magnetoconcentrated by the Lorentz force and consequently the current-voltage (I(V)) law becomes non-linear. The theory of the FAPME effect is proposed for thin semiconductor layers, where the recombination rate at the film-substrate interface is a key parameter. The roles of other important factors (electric and magnetic fields, lifetime, dimensions) are also systematically investigated. Experimental data for the open-circuit voltage, the photomagnetoresistance and the I(V) characteristics were obtained for n-type GaAs films 1.5 μm thick in magnetic and electric fields of up to 13 T and 1.5 x 10⁴ V m^-1 respectively. A satisfactory agreement with the theory is found, in spite of some inherent limitations (film non-uniformity, influence of the semi-insulating GaAs substrate). Complementary magnetotransport measurements were performed without photoexcitation in the temperature range 77–300 K. These numerous and independent experiments are simultaneously exploited for the assessment of several basic properties of GaAs: the lifetime, the surface recombination velocities, the Hall and drift mobilities and the scattering mechanisms.