The influence of the surface on charge carrier transport in GaAs films

Contactless transient photoconductivity measurements in n-doped GaAs films with different doping concentrations are presented. It is shown that at low excess carrier densities the signal is due to excess charge carriers separated in the space charge region. These signals are characterized by a long decay time not related to the bulk properties of the films. At moderate excess carrier densities surface recombination takes place still hampered by the space charge field giving way to a high surface recombination at high excitation densities.