A Highly Sensitive Detector for Radiation in the Terahertz Region

In this paper, we report progress in the development of a detector for photons in the terahertz region consisting of a lateral quantum dot (QD), defined in a semiconductor heterostructure by mesa patterning and three negatively biased metallic gates, and a single-electron transistor (SET) on top of the mesa and, hence, capacitively coupled to the QD. We study the behavior of the QD as a function of the potential applied to the gates using the SET as a sensitive charge detector and identify the bias region of the device, where it is sensitive to incident terahertz radiation. The QD converts incident photons into charge excitations, which can be detected by the SET, resulting in a signal of the order 10 ⁸ electrons for each absorbed photon. Based on the dark count rate and an estimate of the quantum efficiency, the detector should enable low-power measurements in the terahertz region with noise-equivalent power ~10^-19 W/Hz^1/2 exceeding the sensitivity of commercially available bolometers by two orders of magnitude