Amorphous silicon balanced photodiode for detection of ultraviolet radiation

In this work, we present a new amorphous silicon balanced photodiode, which takes advantage of the differential measurement to reveal very small variations of photocurrent in a large background current signal.The device has been fabricated with a four-mask process and characterized in dark and under 365 nm monochromatic ultraviolet radiation.Results have demonstrated the ability of the structure to detect differential currents three orders of magnitude lower than the current flowing in each sensor. Common mode rejection ratio (CMRR) values around 42 dB have been found comparable with those obtained in other crystalline differential diode structures. The CMRR resulted constant with both the reverse bias voltage and the radiation intensity.