Dynamic coupling effect in Z FET and its application for photodetection

In this paper, the application of the zero subthreshold swing and zero impact ionization FET ( $\text{Z}^{2}$ -FET) for photodetection is studied with TCAD simulation. Dynamic coupling effect is utilized to form carrier injection barriers in the partially depleted silicon-on-insulator (PD-SOI) film. Photoelectron accumulation at the front gate interface lowers the hole injection barrier and modulates the turn-on voltage. The light-triggering threshold of the device can be tuned by the front gate voltage, which controls the injection barrier height. We explore two operation modes suited to different applications, and demonstrate the operation of a one-transistor active pixel sensor array. Unlike other image sensors that utilize only one type of carrier, the $\text{Z}^{2}$ -FET photodetector uses photo-generated holes to induce high electron currents through internal amplification, leading to a high sensitivity of up to $1.8\times 10^{5}$ e-/(lux $\cdot \text{s}$ ).