Investigation of metal contacts on high-resistivity large-area amorphous selenium alloy films

Amorphous selenium (a-Se) alloy materials doped with lithium (Li), boron (B), arsenic (As), and chlorine (Cl), were synthesized for room temperature radiation detection applications using an optimized alloy composition for enhanced charge transport properties. A two-step synthesis process has been implemented to first synthesize the a-Se (As) and a-Se (Cl) master alloys from zone-refined Se (~7N), and then synthesize the final mixed optimized alloys. The alloy material was used for thin-film deposition on oxidized aluminum (Al) and indium tin oxide (ITO) coated glass substrates. Material purity, morphology, and compositional analysis of the a-Se alloy materials were investigated by glow discharge mass spectroscopy (GDMS), x-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). Different metals of various work functions (Ni, W, Au, Pd, In, Cu, Sn, Cu, Ag, Al, Cr, Zn and Mo) were selected for Schottky barrier detector performance studies. Current-voltage (I-V), capacitance voltage (C-V), and current transient measurements were performed at different temperatures to investigate the metal contacts and contact stability characteristics. Single and multi-element detectors with and without various blocking contacts (electron and holes) have been fabricated and tested and the results show promising characteristics for x-ray and high energy nuclear radiations with its high dark resistivity (~10¹² Ω-cm) and large-area scalability.