Charge trapping effects in photovoltage measurements of (Ga,Mn)As

We report charge trapping effects in a ferromagnetic (Ga,Mn)As thin film observed during measurements of the photovoltage under inhomogeneous illumination conditions. Using a laser diode as the excitation source, the temperature-dependent response has been observed, with open-circuit voltages as high as −1.4 V. The unexpectedly large and sharp temperature-dependent responses are explained in terms of the excitation of photo-generated charges and their trapping in localised states, or separation of the charges across the film/substrate interface. The sharp features found in the signals suggest their possible use for studying localised trapping states in semiconductors using inhomogeneous illumination.