A Quantum-Dot-Coated Image Sensor With a Wide-Spectral Sensitivity From X-rays to SWIR Photons

Silicon-based complementary metal-oxide semiconductor (CMOS) image sensors dominate a range of application areas but are intrinsically limited to the visible spectrum. For invisible light detection, monolithic integration of a thin-film photon absorber on a CMOS readout chip has been a promising solution. CMOS processes are favorable for a high pixel resolution, low power consumption, and complex readout electronics. Lead sulfide (PbS) colloidal quantum dots (QDs) offer low-cost synthesis, widely tunable light absorption, and high material compatibility. To benefit both sets of features, we have designed a thin-film image sensor by directly processing an absorber stack with a 120-
$\mu$
m PbS-QD layer on our in-house CMOS readout chip. Characterization results prove its potential use in three wavelength ranges (i.e., X-ray, visible, and short-wave infrared) for various applications. To our knowledge, this is the first image sensor using PbS QDs on silicon readout to directly convert X-rays into electrical signals and yet remaining sensitive at a wavelength up to 1.3
$\mu$
m.