Aging effects of schottky barrier position sensitive detectors

This paper reports on the changing performance of Schottky barrier position sensitive detectors (PSDs) over a threeyear span. Devices were fabricated from p-Si and thin Schottkybarrier metal films of tantalum, titanium, and aluminum andmeasured over a three-year period, with the aim of investigatingwhich metals produced the best and most stable devices. Resultsshowed the linearity of the electrical outputs was largely unchangedbut that the magnitude of the electrical outputs changedquite markedly in some cases. Generally, it was found that theTa and Al devices showed the most consistent improvement, withTa devices improving on average about 6.5% and Al devicesimproving, on average, 8.5%. For Ti, less than half of the devicesimproved with the average change in performance being a deteriorationin response of 4%. Secondary ion mass spectroscopyresults showed that the Ta and Al metals are migrating withrespect to the silicon interface, which may indicate the growth ofmetal oxides in this region with the possible formation of activepseudometal–insulator–semiconductor structures, which can beassociated with improved device performance. Response times of the PSDs were in the range of 2 to 3 μs for devices based on all three metals.