Influence of infrared illumination on the accuracy of the quantized Hall resistance

The influence of infrared radiation on the accuracy of the quantized Hall resistance devices used in metrology is investigated. Samples exhibiting anomalous quantized Hall resistances due to large contact resistances resulting from a partially depleted electron gas can be brought back to a normal behavior by illumination with short pulses of infrared light. In addition, the critical current in the QHE regime can be considerably increased by the same illumination method.