Aging Effects of Schottky Barrier Position Sensitive Detectors

This paper reports on the changing performance of Schottky barrier position sensitive detectors (PSDs) over a three-year span. Devices were fabricated from p-Si and thin Schottky barrier metal films of tantalum, titanium, and aluminum and measured over a three-year period, with the aim of investigating which metals produced the best and most stable devices. Results showed the linearity of the electrical outputs was largely unchanged but that the magnitude of the electrical outputs changed quite markedly in some cases. Generally, it was found that the Ta and Al devices showed the most consistent improvement, with Ta devices improving on average about 6.5% and Al devices improving, on average, 8.5%. For Ti, less than half of the devices improved with the average change in performance being a deterioration in response of 4%. Secondary ion mass spectroscopy results showed that the Ta and Al metals are migrating with respect to the silicon interface, which may indicate the growth of metal oxides in this region with the possible formation of active pseudometal-insulator-semiconductor structures, which can be associated with improved device performance. Response times of the PSDs were in the range of 2 to 3 mus for devices based on all three metals