Negative differential photoconductance in an alternately doped multiple quantum well structure

Abstract
We have measured the infrared photoconductivity of an alternately doped multiple quantum well structure. From this measurement, the density of the electrons dynamically stored in the undoped wells, which is critically important in the theory of tunneling, can be deduced at different external biases. A striking negative differential photoconductance feature is observed which is fully consistent with the theory of sequential tunneling.