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

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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 crystalline layered devices. The sputtered a-Si : H detectors were configured as SB-intrinsic-n-type (SB-i-n) devices and exhibited properties similar to doped a-Si : H p-i-n diodes produced by conventional plasma-enhanced vapor deposition processes. A figure of merit is the correlation coefficient (r) which measures the linearity of the device output and which has a maximum value 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 crystalline silicon (c-Si) devices, with Pt/c-Si and Au-Zn/c-Si devices having r~1 for a range of measurements. The maximum detectable position range, 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 µm while for the a-Si devices it was less than 50µm. A comparison of device response was made using a green diode laser (532 nm) and a red gas laser (633 nm) and a focused white light source.