Journal Article

Thin-Film Quantum Dot Photodiode for Monolithic Infrared Image Sensors

Heremans, Paul, Malinowski, Pawel, Georgitzikis, Epimitheas, Vamvaka, Ioanna, De Moor, Piet, Frazzica, Fortunato, Van Olmen, Jan, Hens, Zeger, Maes, Jorick, Cheyns, David

2017

Overview

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 10−6 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.

• Publisher: MDPI AG,MDPI
• Subject: image sensor / imaging / infrared / monolithic integration / PbS / quantum dot / Quantum dots / Sensors