Vertically Stacked Intraband Quantum Dot Devices for Mid-Wavelength Infrared Photodetection

Abstract

Intraband quantum dots are degenerately doped semiconductor nanomaterials that exhibit unique optical properties in mid- to long-wavelength infrared. To date, these quantum dots have been only studied as lateral photoconductive devices, while transitioning toward a vertically stacked structure can open diverse opportunities for investigating advanced device designs. Here, we report the first vertical intraband quantum dot heterojunction devices composed of Ag₂Se/PbS/Ag₂Se quantum dot stacks that bring the advantage of reduced dark conductivity with a simplified device fabrication procedure. We discuss the improvement in the colloidal synthesis of Ag₂Se quantum dots that are critical for vertical device fabrication, identify an important process that determines the mid-wavelength infrared responsivity of the quantum dot film, and analyze the basic device characteristics and key detector performance parameters. Compared to the previous generation of Ag₂Se quantum dot-based photoconductive devices, approximately 70 times increase in the mid-wavelength responsivity, at room temperature, is observed.