A Comparison of Schottky Barrier Position-Sensitive Detectors as a Function of Light Wavelength

Position-sensitive detectors (PSDs), are single continuous optical sensors that utilize the lateral photovoltaic effect to produce an electrical output that varies linearly with light spot position. This work reports further on the results from Schottky barrier PSDs fabricated from thin films of tantalum, titanium, and aluminum. The optimal thickness of the Schottky metals was determined, trading off light transmissivity and proper Schottky barrier formation. The objective of this work was to determine if devices performed particularly well or poorly under certain light sources and, if so, at what thickness of film. Each device has been tested in one dimension under 5 mW of red laser light, focused broad-band light, as well as filtered red, green, and blue light. It was found that all devices generally responded well to the filtered red light and worst under the green light source. The extent to which this is true depends on the Schottky metal used and its thickness. It was also found that the detector response changed over time. Most interestingly, the tantalum Schottky barrier devices either improved or remained the same while the titanium devices deteriorated noticeably.