Optimizing the response of Schottky barrier position sensitive detectors

One of the key criteria in measuring the effectiveness of position sensitive detectors (PSDs) is that of sensitivity-how large an electrical signal can be produced for a given change in the incident light position. The larger the signal produced, then the less additional electronics for amplification required. In this paper we report on optimizing device response by altering substrate thickness and substrate resistivity. We have found that thinner substrates result in greatly increased sensitivities with equal if not improved linearities compared with the equivalent thicker substrate devices. In this work we compare three Schottky metals, Al, Ti and Ta. The improvements in sensitivities for Al devices were greatest at more than 100%, while with Ti and Ta, improvements were better than 50%. Another aspect of the work currently under investigation is the effect of substrate resistivity on the sensitivity and linearity of devices. Preliminary results so far show that high resistivity devices produce markedly higher sensitivities but also respond more to levels of background light, to which low resistivity devices are essentially impervious.