A Separate‐Absorption‐Charge‐Multiplication Short‐Wave Infrared Avalanche Photodiode With an Ultrahigh Gain Based on PbS Quantum Dots

ABSTRACT Short‐wave infrared (SWIR) avalanche photodiodes (APDs) hold great promise for applications in optical communication and single‐photon detection. The conventional SWIR APDs rely on Ge and InGaAs, which are hindered by complex processes, high material defect densities, and high costs. In the present work, a separate‐absorption‐charge‐multiplication (SACM) SWIR APD is proposed, combining the advantages of Si APD and colloidal PbS quantum dots (QDs). Si has a near‐zero ratio of hole to electron ionization coefficient, giving rise to an extremely low noise factor. PbS QDs show excellent optoelectronic performance and compatibility with substrates. The PbS QD SACM‐type APD exhibits a multiplication gain of up to 117, a responsivity of 2.41 A/W, and an external quantum efficiency of 239% under 90 V bias at 1250 nm. This device not only extends the response wavelength of Si APD but also provides a new strategy for low‐cost SWIR APDs.