Enhancing detectivity in multi-barrier Ag2Se-PbS CQD photodetector through numerical optimization of design parameters

Colloidal quantum dots (CQDs) with variable narrow bandgaps have emerged as powerful competitors to epitaxially grown semiconductors in the domain of infrared light transitions. This class of materials holds great promise for the development of next-generation optoelectronic devices, especially photodetectors. In recent developments, the use of silver chalcogenide CQDs has extended into biomedical applications of quantum dots. This expansion is attributed to their advantageous properties, such as low toxicity and tunable intraband transitions reaching the mid-infrared window. In this research, we investigate a structure for mid-infrared photon detection in the form of an intraband Ag2Se-PbS colloidal quantum dot (CQD) photodetector. Detectivity, a crucial performance parameter, is enhanced through numerical optimization by manipulating key design parameters such as Ag2Se CQD diameter, Ag2Se film doping density, and the number of PbS CQD layers in the barrier layer of the device's active region. This optimization process is conducted at various temperatures and biases. The results reveal that, under conditions of a 1 V bias and 80 K, the designed Ag2Se-PbS CQD infrared photodetector achieves peak detectivities. Specifically, observed peak detectivities of 13.13×109 Jones for Ag2Se CQDs with a diameter of 3.7 nm, and 11.01×109 Jones for a film doping density of 6.7×1018 cm-3 of Ag2Se CQDs.