The field-assisted photomagnetoelectric effect: theory and experiment in semi-insulating GaAs

Abstract

The field-assisted photomagnetoelectric (FA-PME) effect is a promising superposition of the conventional PME effect and of the magnetoconcentration effect: when a (high) electric field is superimposed, Lorentz forces cause the photogenerated carrier profile to be modified, and consequently the current-voltage characteristics I(V) become non-linear. The authors propose a general theoretical model and derive specific results for the case of semiconductor samples the thickness of which is much larger than both diffusion length and light absorption depth. The behaviour of the FA-PME effect as the electric field is varied is analysed with special emphasis on the role of bulk and surface recombinations and trapping mechanisms. Measurements of photomagnetoresistance, short-circuit ME current and I(V) characteristics have been made in semi-insulating GaAs, 350 mu m thick for a wide-range of electric (0-105 V m-1) and magnetic (0-14T) fields. These experiments are fully consistent with the theory and therefore constitute a basis for very accurate characterisation of carrier lifetime ( tau n=1.7 ns, tau p=2.2 ns) and of surface recombination velocities (s from 300 to 20000 m s-1).