Omnivision's patent application US20160099371 "Back side illuminated image sensor with guard ring region reflecting structure" by Eric Webster proposes just that - the reflective metal guard ring around SPAD pixel:
Another Omnivision's application US20160027837 "Visible and Infrared Image Sensor" by Eric Webster, Howard Rhodes, and Dominic Massetti proposes Si-Ge photosensitive layer to extend IR response:
Another Omnivision's application US20160027837 "Visible and Infrared Image Sensor" by Eric Webster, Howard Rhodes, and Dominic Massetti proposes Si-Ge photosensitive layer to extend IR response: