A highly sensitive terahertz photon detector based on a semiconductor quantum dot

We have developed a detector for photons in the terahertz region consisting of a lateral semiconductor quantum-dot (QD), defined in the two-dimensional electron gas (2-DEG) of a mesa-patterned heterostructure using three metallic gates, and a metallic single-electron transistor (SET) fabricated on top of the mesa. The SET is capacitively coupled to the QD. THz photons can be absorbed by the QD resulting in excitations associated with a change in charge-state of the QD, which can be detected directly as a change in the conductance of the SET. We characterize the detector by using radiation from a black-body emitter at the 1 K stage of our apparatus. Operation of the detector at a temperature of 300 mK is demonstrated and the noise equivalent power (NEP) is estimated to be of the order of 10 19 W/radicHz based on a dark count rate of 0.1/s and a quantum efficiency of the order of 0.1 %.