Implementation of Specific Frequency Response Using SOI Photodetector Cell

A new silicon-on-insulator (SOI) photodetector was proposed to implement a specific frequency response. The photodetector consists of a photodiode or phototransistor. As an example, a floating body SOI NMOS phototransistor was fabricated by using 1.5-$mu$m CMOS technology. The electrical and the optical properties of the transistor were measured and characterized. It was found that a 350-nm-thick n$^+$ polysilicon gate in a phototransistor could filter out optical signals with wavelengths less than 450 nm by absorbing the signals. Gate and drain biases for reasonable operation of the SOI NMOS phototransistor were 0 V to the threshold voltage of the MOSFET and less than about 1.5 V, respectively.