A method is proposed for the determination of deep impurity levels and density profiles fromC&sngbnd;Vmeasurements and is demonstrated on GaAs Schottky barrier diodes. The technique involves measurements of the time dependence of the bias voltage instead of the barrier capacitance. The spatial distribution of a deep level is observed to exhibit a peak at the boundary between an epitaxial layer and the semi‐insulating substrate. This deep center is located 0.8 eV below the conduction band.