title: Enhanced detection efficiency of direct conversion X-ray detector using polyimide as hole-blocking layer.
abstract: In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (≥10 V/μm) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm(2)/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector.
authors.affiliation: Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada.
authors.forename: Shiva
authors.initials: S
authors.lastname: Abbaszadeh
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Scott
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Bubon
authors.forename: Alla
authors.initials: A
authors.lastname: Reznik
authors.forename: Karim S
authors.initials: KS
authors.lastname: Karim