Dark current in multilayer stabilized amorphous selenium X-ray photoconductors

Commercially available flat panel, direct conversion, digital X-ray image detectors use a photoconductive layer of stabilized amorphous selenium (a-Se) sandwiched between two electrodes to convert incident X-ray radiation into stored electrical charge. These detectors use thin n-like and p-like blocking layers to trap charge carriers injected from the contacts and thus reduce the dark current by limiting the rate of carrier injection. The effect of each of these blocking layers is determined by measuring the dark current in 200 mu m thick mammographic detector-like samples of a-Se with three different structures: a single intrinsic layer and n-i and i-p double layers. Dark current is measured as a function of time over 20,000 s and as a function of applied electric field over the range of -10 V/mu m to +10 V/mu m. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim