A quantum dot as a sensitive terahertz detector

The formation of 1 μm-diameter quantum dot (QD), defined by mesa patterning and metal gates in a GaAs/AlGaAs heterostructure, is studied using a capacitively coupled aluminium single-electron transistor (SET). The SET senses the charge of the QD at different gate potentials and can identify stable and metastable states of the QD. An electrostatic model gives a good description of the stable states, leaving, however, some unanswered questions concerning the metastable states. The application of the device for the sensitive detection of terahertz radiation is discussed.