TFT-based, multi-stage, active pixel sensor for alpha particle detection

A multi-stage thin film transistor (TFT)-based active pixel sensor (APS), capable of successfully detecting small impulses of charge resulting from incident alpha particle strikes, is presented. Detection of alpha particles is important in the field of neutron detection, where fully integrated thin-film-based detectors are an attractive alternative to conventional 3He-based proportional counters owing to their low-cost and large-area scaling capability, combined with the use of readily available materials. A typical TFT process, however, produces only N-type devices with low electron mobilities-making high-gain CMOS amplifier designs unfeasible. The disadvantages of using a TFT-only APS design are mitigated by cascading multiple low-gain TFT amplifiers, which results in a higher overall pixel gain-subsequently allowing for the successful detection and readout of alpha particle strikes. Presented is a new APS fabricated in an indium gallium zinc oxide TFT process is presented, and successful initial alpha response measurements are reported.