Thin-Film Quantum Dot Photodiode for Monolithic Infrared Image Sensors

• Published in: Sensors (Basel, Switzerland) Switzerland), 2017-12, Vol.17 (12), p.2867
• Main Authors: Malinowski, Pawel E, Georgitzikis, Epimitheas, Maes, Jorick, Vamvaka, Ioanna, Frazzica, Fortunato, Van Olmen, Jan, De Moor, Piet, Heremans, Paul, Hens, Zeger, Cheyns, David
• Format: Article
• Language: English
• Subjects: Architecture; Augmented reality; Biometrics; CMOS; Dark current; image sensor; imaging; infrared; Infrared cameras; Infrared imagery; Infrared imaging; Military applications; monolithic integration; Obstacle avoidance; PbS; quantum dot; Quantum dots; Sensors; Thin films
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s17122867

Imaging in the infrared wavelength range has been fundamental in scientific, military and surveillance applications. Currently, it is a crucial enabler of new industries such as autonomous mobility (for obstacle detection), augmented reality (for eye tracking) and biometrics. Ubiquitous deployment of infrared cameras (on a scale similar to visible cameras) is however prevented by high manufacturing cost and low resolution related to the need of using image sensors based on flip-chip hybridization. One way to enable monolithic integration is by replacing expensive, small-scale III-V-based detector chips with narrow bandgap thin-films compatible with 8- and 12-inch full-wafer processing. This work describes a CMOS-compatible pixel stack based on lead sulfide quantum dots (PbS QD) with tunable absorption peak. Photodiode with a 150-nm thick absorber in an inverted architecture shows dark current of 10 A/cm² at -2 V reverse bias and EQE above 20% at 1440 nm wavelength. Optical modeling for top illumination architecture can improve the contact transparency to 70%. Additional cooling (193 K) can improve the sensitivity to 60 dB. This stack can be integrated on a CMOS ROIC, enabling order-of-magnitude cost reduction for infrared sensors.