Search

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/Hz1/2 exceeding the sensitivity of commercially available bolometers by two orders of magnitude

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.

A highly sensitive detector of submillimeter wavelength radiation is reported. The detector consists of a semiconductor quantum dot (QD) and a metallic single-electron transistor (SET). The SET detects change in the potential distribution induced by photon absorption within the QD. We have fabricated and studied this detector at wavelengths longer than 200μm. High sensitivity, ∼10−20W∕Hz in terms of noise equivalent power, is found. Further optimization of the detector design is suggested.

We report progress in developing a sensitive detector for terahertz radiation, based on a semiconductor quantum dot (QD) capacitively coupled to a metallic single electron transistor (SET). A charge polarization of the QD induced by the absorption of individual photons is detected by the voltage-biased SET. We investigate the sensitivity of the detector to broadband radiation, over a range of QD barrier heights, and find that there is a measurable photo-signal over wide range of gate voltages defining the QD. This is an improvement on previous designs of terahertz detector based on the QD/SET principle, and makes the new detector a candidate for use in an imaging device.