Omnivision Proposes Combined Buried-Surface TG Structure

Omnivision patent application US20130092982 "Partial buried channel transfer device for image sensors" by Gang Chen, Sing-Chung Hu, Hsin-Chih Tai, Duli Mao, Manoj Bikumandla, Wei Zheng, Yin Qian, Zhibin Xiong, Vincent Venezia, Keh-Chiang Ku, and Howard Rhodes proposes to have additional doping on TG making its adjacent to PD part to be buried-channel:

"The result is that any dark current generated under transfer device 425 is likely to drift toward floating diffusion region 415. This feature prevents white pixels from forming and reduces image lag by discouraging electrons from being sent back to photosensitive element 410 after a transfer event."