Substrate bias effects on noise and minority carrier lifetime in SOI MOSFET single-photon detector

Operation speed of the single-photon detector based on the silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) is affected by the noise and minority carrier lifetime, both of which are found to be dependent on the substrate bias. The noise spectrum are obtained at various substrate voltages in dark condition while keeping the average drain current constant. The noise becomes minimum at around the transition point between front- and back-channel operations, and in the back-channel region near the transition point. On both negative and positive sides of the substrate voltage, the noise shows peculiar Lorentzian spectra. Minority carrier lifetime is evaluated by the analysis of drain current histogram at different substrate voltages. It is found that the peaks in the histogram corresponding to the larger number of stored holes become higher as the substrate bias becomes more positive. This can be attributed to the prolonged lifetime presumably caused by the higher electric field inside the body of SOI MOSFET. It can be concluded that, once the inversion channel is induced for detection of the photo-generated minority carriers, the small absolute substrate bias is favorable for short lifetime and low noise, leading to high-speed operation.