A very high gain and a wide dynamic range static induction phototransistor

This letter describes a new phototransistor based on the static induction transistor (SIT) structure. A D/C optical gain and a gain-bandwidth product of a fundamental normally-on type static induction phototransistor (SIPT) are reported. The D/C optical gain G of more than 10⁵has been obtained at 10-pw incident power levels (λ = 8800 Å), and the average gain-bandwidth product of approximately 10⁸(Hz) has been measured at a few ten nanowatts of incident optical power level (λ = 6550 Å). The SIPT is characterized by a high sensitivity at low incident power, good linearity for a wide optical dynamic range, a high controllability of the gain, and a response time which is determined by the gate impedance.