Avalanche multiplication in amorphous selenium and its utilization in imaging

Amorphous selenium (a-Se) is a well known photoconductor that is currently used in X-ray image detectors and HARP video tubes. Recent advances have made it practical to operate a-Se at extremely high electric fields F, where avalanche multiplication occurs. At sufficiently high fields, the effective quantum efficiency (η∗) (or the overall yield) of the photoconductor can be increased several orders of magnitude above unity and renders avalanche …