Development of solid-state avalanche amorphous selenium for medical imaging

Medical Physics
James R ScheuermannW Zhao

Abstract

Active matrix flat panel imagers (AMFPI) have limited performance in low dose applications due to the electronic noise of the thin film transistor (TFT) array. A uniform layer of avalanche amorphous selenium (a-Se) called high gain avalanche rushing photoconductor (HARP) allows for signal amplification prior to readout from the TFT array, largely eliminating the effects of the electronic noise. The authors report preliminary avalanche gain measurements from the first HARP structure developed for direct deposition onto a TFT array. The HARP structure is fabricated on a glass substrate in the form of p-i-n, i.e., the electron blocking layer (p) followed by an intrinsic (i) a-Se layer and finally the hole blocking layer (n). All deposition procedures are scalable to large area detectors. Integrated charge is measured from pulsed optical excitation incident on the top electrode (as would in an indirect AMFPI) under continuous high voltage bias. Avalanche gain measurements were obtained from samples fabricated simultaneously at different locations in the evaporator to evaluate performance uniformity across large area. An avalanche gain of up to 80 was obtained, which showed field dependence consistent with previous measurements from...Continue Reading

References

May 1, 1997·Radiographics : a Review Publication of the Radiological Society of North America, Inc·J A RowlandsZ Huang
Sep 13, 2006·Medical Physics·Aili K BloomquistDaniel J Beideck
Nov 2, 2012·Current Applied Physics : the Official Journal of the Korean Physical Society·Oleksandr BubonAlla Reznik

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