G. BELEV¹, S. O. KASAP¹

Abstract

Current commercial large area flat panel direct conversion x-ray image detectors use doped amorphous selenium (a-Se) alloys as the x-ray photoconductor for the conversion of x-ray radiation to collectable charges. The simple metal/a-Se/metal structure has a large dark current that prevents its use in practical detectors. For this reason, the x-ray photoconductor is not a simple metal/a-Se/metal structure but rather a multilayer structure in which electron and hole injection blocking layers have been inserted next to the electrodes to reduce the dark current. The desirable electron and hole transport in the injection blocking layers are usually achieved by suitably alloying and doping the selenium material, which is a very difficult task. We have proposed a novel way to produce hole-injection blocking layers based on lowering the temperature of the substrates during the film deposition process. X-ray photoconductor layers containing such cold-deposited hole-injection blocking layers have been successfully tested in pilot high resolution x-ray image detectors for mammography. In this paper, we present one possible explanation for the observed changes in the electronic transport in a-Se based films produced at low substrate temperatures..

Keywords

X-ray detectors, Amorphous selenium, Charge transport, Electronic properties, Dark current reduction.

Submitted at: Nov. 5, 2008
Accepted at: Sept. 9, 2009

Citation

G. BELEV, S. O. KASAP, The influence of the substrate temperature on charge transport in vacuum deposited amorphous selenium films♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 9, pp. 1053-1059 (2009)

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