A comparative study of position-sensitive detectors based on Schottky barrier crystalline and amorphous silicon structures

The response and properties of thin film position-sensitive detectors (PSDs ) fabricated from novel hydrogenated amorphous silicon (a-Si : H) Schottky barrier (SB) structures are compared in this work with conventional crystal line layered devices. The sputtered a-Si : H detectors were configured as S B-intrinsic-n-type (SB-i-n) devices and exhibited properties similar to dop ed a-Si : H p-i-n diodes produced by conventional plasma-enhanced vapor dep osition processes. A figure of merit is the correlation coefficient (r) whi ch measures the linearity of the device output and which has a maximum valu e of 1. Based on this, the a-Si : H structures gave very promising results (r=0.983 to 0.997), while the overall best results were obtained with cryst alline silicon (c-Si) devices, with Pt/c-Si and Au-Zn/c-Si devices having r similar to1 for a range of measurements. The maximum detectable position r ange, or spatial resolution, of optical sensors is another figure of merit and in this work this parameter for the crystalline devices was measured to be less than 10 mum while for the a-Si devices it was less than 50 mum. A comparison of device response was made using a green diode laser (532 nm) a nd a red gas laser (633 nm) and a focused white light source. (C) 2001 Kluw er Academic Publishers.