Fotodetector de ponto quântico semicondutor operando em frequência Terahertz

Abstract

Photodetectors are light detecting devices usually formed by semiconductors. They have been studied since the 20th century, and are normally based on quantum wells and dots, for example. Applications for photodetectors range from communications in optoelectronics, obtaining biomedical images, in military purposes, obtaining images in the infrared spectrum, to environmental protection and the manufacturing industry. Within the family of known photodetectors, those operating at frequencies in the order of a few Terahertz are significantly less explored nowadays, due to a lack of possible devices that work in that frequency range. In this work, we propose a photodetector device based on quantum dots that operates in Terahertz. In order to do so, the photo-generated current due to electronic transitions in a semiconductor planar quantum dot attached to outgoing leads is theoretically investigated. An electron is confined in the dot by a pure quantum mechanical effect, which is due to the higher ground state energy of the quantum wells forming the leads, as compared to the one in the dot. The dynamics of a such confined electron interacting with a light pulse is investigated by numerically solving time-dependent Schrödinger equation within the effective mass approximation, and goes beyond the lowest order perturbative approach. Our results shows the coexistence of both linear and non-linear contributions to the photo-generated current in this system, sharply peaked at frequencies in the terahertz range, which are further tunable by the quantum dot radius. The peaks can be made even sharper as one adds a narrow constriction in the dot-leads connection. Details of the dependence of the peaks' frequency, intensity and sharpness on the system parameters are discussed.