Omnivision patent application US20150048427 "Image sensor pixel cell with switched deep trench isolation structure" by Sing-chung Hu, Rongsheng Yang, Gang Chen, Howard E. Rhodes, Sohei Manabe, and Hsin-chih Tai proposes a BSI pixel with DTI, filled by a lightly doped poly. A negative pulse applied to the DTI poly allows increasing PD doping and full well while maintaining a low image lag:
