PbS Colloidal Quantum Dot Photodiodes for SWIR Detection

Abstract

In this work, PbS colloidal quantum dot based photodiodes are realized compatible for the integration on ROIC's. Schottky photodiode architecture is selected for its fast response and moderate sensitivity. The device is formed from Indium tin oxide (ITO) anode, the photosensitive PbS layer and a schottky contact formed of titanium and gold. Pinhole-free uniform PbS quantum dots film achieved by optimized layer by layer spin coating process. Solid-state ligand change procedure applied during film coating using 3-mercaptopropionic acid (3-MPA) in order to remove long oleic acid ligand that degrades electron mobility in the film. Fabricated detectors achieved rectification ratios of 15 at +/- 1 V bias. Preliminary tests show a responsivity of 0.24 A/W is achieved. Specific detectivity D* is calculated as 3,54x1010 that is limited due to high dark currents.