In this paper, two kinds of colloidal quantum dots, PbS and HgTe, are explored for SWIR photodetectors application.
The colloidal dots are prepared by hot injection chemical synthesis, with organic ligands around the dots keeping them
stable in solution. For the purpose of achieving efficient carrier transport between the dots in a film, these long organic
ligands are replaced by shorter, inorganic ligands. We report uniform, ultra-smooth colloidal QD films without cracks
realized by dip-coating and corresponding ligand exchange on a silicon substrate. Metal-free inorganic ligands, such as
OH- and S2-, are investigated to facilitate the charge carrier transport in the film. Both PbS and HgTe-based quantum dot photoconductors were fabricated on interdigitated gold electrodes. For PbS-based detectors a responsivity of 200A/W is measured at 1.5μm, due to the large internal photoconductive gain. A 2.2μm cut-off wavelength for PbS photodetectors
and 2.8μm for HgTe quantum dot photodetectors are obtained.