Pulse characteristics of silicon double barrier optical sensors with signal amplification

The pulse characteristics of optical sensors with double potential barriers formed on the opposite sides of a high-resistivity (ν) silicon substrate have been studied. The first barrier is formed by multiple micro-sized Ti–νSi contact barriers surrounded by Ti–SiO2–νSi MOS structures. The second one is the ν–n+ potential barrier formed at the bottom of the wafer. The structure presents signal amplification for both polarities of the applied voltage. Under negative bias applied to the semi-transparent Ti-electrode, the reason of the current gain is the change in the transport mechanism of carriers through the potential barrier of the Schottky barrier along its perimeter, which is due to the strong electric field originated by the photogenerated minority carriers forming an inversion layer at the silicon-oxide interface. Under positive bias, the current gain is due to the operation of the ν–n+ potential barrier, which was studied earlier, and in this work it is used for comparison purposes.