Nanopattern multi-well avalanche selenium detector with picosecond time resolution

For the first time, we propose using amorphous selenium (a-Se) as the photoconductive material for time-of-flight (TOF) detectors. The major drawback of a-Se is its poor time-resolution and low mobility due to shallow-traps, problems that must be circumvented for TOF applications. Thus, we propose a nanopattern multi-well a-Se detector to enable the utilization of both avalanche multiplication gain and unipolar time-differential (UTD) charge sensing in one device. Advantages of avalanche-mode a-Se are having photoconductive gain and band transport in extended states with the highest possible mobility and negligible trapping. Most importantly, UTD charge sensing enables operating the detector at its theoretical limit of charge diffusion. Our simulation results show that UTD charge sensing in avalanche-mode a-Se improves time-resolution by more than 3 orders-of-magnitude and proves very promising to achieve for the first time the ultimate goal of 10 ps time-resolution with a material that is low-cost and uniformly scalable to large-area.