Single photon detection with a quantum dot transistor

We propose and demonstrate a type of GaAs/AlGaAs modulation-doped field eff ect transistor (FET) which is sensitive to single photons. The FET contains a layer of InAs quantum dots formed using an in-situ, self-organising meth od, adjacent to the channel and separated from it by a thin AlGaAs barrier. Capture of a single photo-excited carrier by a quantum dot leads to a size able change in the source-drain current through the transistor, allowing th e detection of a single photon. We show this is because the mobility of the electron channel is extremely sensitive to the charge trapped in the dots. This discovery may allow a new type of single photon detector to be develo ped which does not rely upon avalanche processes.