MATERIAL PROPERTIES, PROJECT DESIGN RULES AND PERFORMANCES OF SINGLE AND DUAL-AXIS A-SI-H LARGE-AREA POSITION-SENSITIVE DETECTORS

We have developed large area (up to 80mmx80mm) Thin Film Position Sens itive Detectors (TFPSD) based on hydrogenated amorphous silicon (a-Si: H). Although crystalline silicon PSDs have been realized and applied t o optical systems, their detection area is small (less than 10mmx10mm) , which implies the need of optical magnification systems for supporti ng their field of applications towards large area inspection systems, which does not happen by using a-Si:H devices. The key factors for the TFPSDs resolution are the thickness uniformity of the constituting la yers, the geometry and the position of the contacts. In this paper we present data on single and dual-axis rectangular TFPSDs correlating, t heir performances with the different underlying lateral effects. For t he single axis-detector, with two opposite extended contacts, the outp ut photocurrent difference to sum ratio is a linear function of the po sition of a narrow incident light beam, even for low illumination leve ls (below 20 lux). For the dual-axis detector with extended contacts, at all four sides (except for small gaps at the vertices due to edge e ffects) an almost linear relation has been found between the incident light spot position along both axis and the corresponding output photo currents.