6 May 2009 A new CMOS SiGeC avalanche photo-diode pixel for IR sensing
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Near-infra-red sensing with silicon is limited by the bandgap of silicon, corresponding to a maximum wavelength of absorption of 1.1 μm. A new type of CMOS sensor is presented, which uses a SiGeC epitaxial film in conjunction with novel device architecture to extend absorption into the infra-red. The SiGeC film composition and thickness determine the spectrum of absorption; in particular for SiGeC superlattices, the layer ordering to create pseudo direct bandgaps is the critical parameter. In this new device architecture, the p-type SiGeC film is grown on an active region surrounded by STI, linked to the S/D region of an adjacent NMOS, under the STI by a floating N-Well. On a n-type active, a P-I-N device is formed, and on a p-type active, a P-I-P device is formed, each sensing different regions of the spectrum. The SiGeC films can be biased for avalanche operation, as the required vertical electric field is confined to the region near the heterojunction interface, thereby not affecting the gate oxide of the adjacent NMOS. With suitable heterojunction and doping profiles, the avalanche region can also be bandgap engineered, allowing for avalanche breakdown voltages that are compatible with CMOS devices.
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Carlos Augusto, Carlos Augusto, Lynn Forester, Lynn Forester, Pedro C. Diniz, Pedro C. Diniz, } "A new CMOS SiGeC avalanche photo-diode pixel for IR sensing", Proc. SPIE 7298, Infrared Technology and Applications XXXV, 729839 (6 May 2009); doi: 10.1117/12.818269; https://doi.org/10.1117/12.818269


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