Photoresistance imaging of quantum Hall devices

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Abstract
Spatially resolved measurements of the photoresistance of a 2D electron gas in a quantizing magnetic field have been performed using visible light. The influence of illumination on the resistance is a maximum when the light spot illuminates an edge of the sample. The sign of response is determined by the directions of both bias current and magnetic field as well as by the edge which is under illumination. Using this technique we are able to measure the characteristic length scale of the confining potential at the edge and we obtain a value of approximately=20 mu m for the sample used.